# My DIY Arrow Spine Tester



## Guardian Shoote (Jan 11, 2007)

Nice work


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## daltongang (Jul 29, 2009)

What is the benefit of "finding your stiff side"?


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## L.I.Archer (Sep 6, 2010)

daltongang said:


> What is the benefit of "finding your stiff side"?


So you can orient all your arrows the same way. If you fletch the cock vane on the stiff side, on all the arrows, they'll all flex the same way coming off the bow, giving you more consistent shots and better grouping.


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## STUDENT-ARCHER (Jun 26, 2009)

x2!


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## Ouachitamtnman (Sep 4, 2007)

Wow bro. Great work. May be a bit out of my league though. I can definately see the benefits of it.

Thanks


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## L.I.Archer (Sep 6, 2010)

Thanks. I thought it was out of my league too, until I finally had time to sit down, sketch out what I needed to do and the parts to do it with and voila! - a spine tester.


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## kw1 (Feb 9, 2009)

How much weight did you use


---
- KW


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## L.I.Archer (Sep 6, 2010)

kw1 said:


> How much weight did you use
> 
> 
> ---
> - KW


2 lbs.

I changed the design tonight. Those eye-bolts holding the vertical bolt with the washers on it had too much free play and it was hard to get a reading when I spun an arrow. I took out the eye-bolts and fabricated a 3" sleeve using 5/8" PVC pipe and a few screws to tighten up the tolerance from the 1/2" dia. bolt to the inner dia. of the pipe. I also lubed the 1/2" bolt so it slides easily. There is hardly any wiggle room now and everything lines up nicely. I'll get a picture of it when I get the chance.


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## turkeyhunter60 (Apr 19, 2010)

L.I.Archer said:


> 2 lbs.
> 
> I changed the design tonight. Those eye-bolts holding the vertical bolt with the washers on it had too much free play and it was hard to get a reading when I spun an arrow. I took out the eye-bolts and fabricated a 3" sleeve using 5/8" PVC pipe and a few screws to tighten up the tolerance from the 1/2" dia. bolt to the inner dia. of the pipe. I also lubed the 1/2" bolt so it slides easily. There is hardly any wiggle room now and everything lines up nicely. I'll get a picture of it when I get the chance.


Where did you get the Dial Gauge??


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## L.I.Archer (Sep 6, 2010)

turkeyhunter60 said:


> Where did you get the Dial Gauge??


Harbor Freight Tools.


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## L.I.Archer (Sep 6, 2010)

Here's the updated weight slide. There is no free-play in this version vs. the eye-bolt version:


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## turkeyhunter60 (Apr 19, 2010)

Good Job and Thank You....That 1/2 inch bolt...Did you cut the bolt with a Hack Saw flat to mount the rollers on to it...???..And when you put the weight onto the middle of the arrow, you said 2 pounds, you rotate the arrow by hand to find the stiffest spot,spine, and mark it, then your done...???....


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## L.I.Archer (Sep 6, 2010)

turkeyhunter60 said:


> Good Job and Thank You....That 1/2 inch bolt...Did you cut the bolt with a Hack Saw flat to mount the rollers on to it...???..And when you put the weight onto the middle of the arrow, you said 2 pounds, you rotate the arrow by hand to find the stiffest spot,spine, and mark it, then your done...???....


The 1/2" bolt is notched 1/2" from the end and halfway through the diameter so I had a flat spot to mount the L-shaped angle that the rollers are mounted to. On the backside of where I notched, I filed down another flat spot so that the screw head had something flat to sit against. 

And between the original post and this one, notice I moved both rollers on the T-angle to the same side.

And yes, you roll the arrow with your finger right above where the arrow sits on the rollers so you don't influence how the arrow bends. I watch the gauge's needle as I spin the arrow and mark the top of the arrow when the number goes highest on the dial. The top of the arrow at this point would be the stiffest.


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## turkeyhunter60 (Apr 19, 2010)

Thank you for the Info...I got it now....


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## dwagoner (Sep 27, 2007)

kw1 said:


> How much weight did you use
> 
> 
> ---
> - KW


heres AMO standard for measuring arrow spine if you want to get weight dead on, 2lbs is quite close but 1.94 is the exact number
.....The measurement is made by spanning the shafts between 28″ centers . A 1.94 lb. weight is suspended from the center of the shaft and the deflection measurement is made with a digital linear gauge. This is per the AMO standard.


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## L.I.Archer (Sep 6, 2010)

dwagoner said:


> heres AMO standard for measuring arrow spine if you want to get weight dead on, 2lbs is quite close but 1.94 is the exact number
> .....The measurement is made by spanning the shafts between 28″ centers . A 1.94 lb. weight is suspended from the center of the shaft and the deflection measurement is made with a digital linear gauge. This is per the AMO standard.


I didn't care about the AMO standard weight. I know what it is; I just rounded it up to 2 lbs, since I am only using it to measure where my arrow spine is stiffest so I can fletch all my arrows with the stiff side up.


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## 138104 (May 14, 2009)

Here is another spine tester. There should be charts to convert your dial to spine.
http://www.jamesmhill.com/Spine_Tester.html


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## L.I.Archer (Sep 6, 2010)

Perry24 said:


> Here is another spine tester. There should be charts to convert your dial to spine.
> http://www.jamesmhill.com/Spine_Tester.html


No need to convert anything. I just look at the dial while I'm turning the arrow and look to see where the dial number increases. At the peak of the increase, that's where the spine is weakest and the top of the arrow, at that position, is stiffest. I mark it, fletch it and forget about it.

By the way, I used Jim Hill's eye-bolt method at first and there's way too much movement with the bolt that goes through them. I used a 5/8" pvc pipe and shimmed it with screws to tighten up the tolerances so that there is no movement to the bolt that goes through it.


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## 138104 (May 14, 2009)

I thought I would post it up so people could see the chart if they want to see if an arrow matches it's advertise spine. If you just want to check for the stiff side, it isn't needed of course. I do like your design for how the weight touches the arrow and the use of bearings to make it easier to spine.


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## Unk Bond (Aug 1, 2004)

Hello All, very nice. [ Later


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## Bearlee (Dec 24, 2009)

nice!


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## Don Schultz (Jul 5, 2002)

Fine design. Good execution I've seen simpler devices to find the soft axis. Orienting on softspine is also useful for the same reasons, but stiff orientation seems better to me. Also you can find the "bad apple" in the arrow bin.


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## erictski (May 20, 2009)

Does spine need to be tested at a 28" pan...

can you take a cut arrow (for me between 26.5 and 28") and use like a 24" span instead?


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## skynight (Nov 5, 2003)

Here are some instructions I stole and posted a while back. I did make one, but wasn't too pleased with how it turned out for me. i bought a RAM products tester, which will also test broadhead runout which is nice.

http://www.archerytalk.com/vb/showthread.php?t=604405&highlight=spine+tester+skynight


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## L.I.Archer (Sep 6, 2010)

erictski said:


> Does spine need to be tested at a 28" pan...
> 
> can you take a cut arrow (for me between 26.5 and 28") and use like a 24" span instead?


I made it so the brackets at each end could be rotated around to test arrows shorter than 28". My arrows are 27" but the minimum my tester could go is 26" without having to move the brackets closer together.


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## Bearlee (Dec 24, 2009)

Where do you get a dial gage and are roller blade roller bearings the best? 

I have been thinking of doing the same thing , but also making it where the ends were movable to work on an size arrow and it would double as an arrow spinner to test broadheads as well.


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## L.I.Archer (Sep 6, 2010)

Bearlee said:


> Where do you get a dial gage and are roller blade roller bearings the best?
> 
> I have been thinking of doing the same thing , but also making it where the ends were movable to work on an size arrow and it would double as an arrow spinner to test broadheads as well.


Dial gauge at Harbor Freight Tools

Roller blade bearings at Dick's Sporting Goods or anywhere they sell rollerblades. I got mine at Dick's. Get the ones that give you the most speed. The ones I got are Abec7 rated. Not really fast enough to spin arrows. You could get really fast ones online.


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## kc hay seed (Jul 12, 2007)

could you do the same thing with an arrow straightner? just roll the shaft and read the gage.


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## L.I.Archer (Sep 6, 2010)

kc hay seed said:


> could you do the same thing with an arrow straightner? just roll the shaft and read the gage.


An arrow straightener only shows you where the arrow is bent; it won't show you which side of the arrow is weak/strong. To do that, you need a constant weight on the shaft as you turn the arrow. The gauge will tell you which side flexes the most.


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## soless (Nov 7, 2011)

If I was just trying to find the stiff side I use two ear plugs and a tub of water. I Don't mean to rain on your parade but if you clean out the shaft, plug both ends of the shaft with some ear plugs and place the shafts in a tub of water, the stiff side (heaviest side) will sink straight down leaving the weak side up. Then mark/dot the shaft with white out or whatever works for you. The opposite side obviously is the stiff side. This works for me.


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## Stickbower (Sep 17, 2011)

That's friggn cool I'm gunna build one thanks for the idea


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## L.I.Archer (Sep 6, 2010)

soless said:


> If I was just trying to find the stiff side I use two ear plugs and a tub of water. I Don't mean to rain on your parade but if you clean out the shaft, plug both ends of the shaft with some ear plugs and place the shafts in a tub of water, the stiff side (heaviest side) will sink straight down leaving the weak side up. Then mark/dot the shaft with white out or whatever works for you. The opposite side obviously is the stiff side. This works for me.


I've already tried floating arrows. The surface of the water prevents the arrow from spinning around so the stiff side is down. Someone mentioned that it'll work if you reduce the surface tension by adding alcohol to the water or simply using pure alcohol. I don't see the point in wasting all that alcohol.


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## Maui Rhino (Mar 13, 2010)

L.I.Archer said:


> I've already tried floating arrows. The surface of the water prevents the arrow from spinning around so the stiff side is down. Someone mentioned that it'll work if you reduce the surface tension by adding alcohol to the water or simply using pure alcohol. I don't see the point in wasting all that alcohol.


You can add liquid soap to the water. I've used Dawn with good results.


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## straddleridge (Apr 28, 2010)

Look at gluchlichers thread on this forum "the weakest side in the arrow". The arrow will always bend toward the weakest side. This is a law of physics. With carbon arrows the stiff side is often not opposite the weak side.


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## Don Schultz (Jul 5, 2002)

Floating arrows started, at the latest, back when we all shot aluminum. The tubes had welded seams. Floating them found the seam which meant you could get the arrow shaft seams oriented the same, even if they were not oriented optimally. And "the same" added to consistency which adds to accuracy. Floating carbons may or may not help, depending on the construction technique used by the mfg of a particular shaft.

I think the stiff side finder shown in this thread should work best because it is actually measuring a direct effect of stiffness, unlike the floating technique.


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## soless (Nov 7, 2011)

straddleridge said:


> Look at gluchlichers thread on this forum "the weakest side in the arrow". The arrow will always bend toward the weakest side. This is a law of physics. With carbon arrows the stiff side is often not opposite the weak side.


I'll have to read that.



Don Schultz said:


> Floating arrows started, at the latest, back when we all shot aluminum. The tubes had welded seams. Floating them found the seam which meant you could get the arrow shaft seams oriented the same, even if they were not oriented optimally. And "the same" added to consistency which adds to accuracy. Floating carbons may or may not help, depending on the construction technique used by the mfg of a particular shaft.
> 
> I think the stiff side finder shown in this thread should work best because it is actually measuring a direct effect of stiffness, unlike the floating technique.


Point made. I just remembered another trick some of my Trad buddy's used to use. It involved a straight edge, some bow string and some weight. Same concept, just a lot less precise.


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## MLabonte (Jan 19, 2009)

Have a question ! How does this work with the new infused arrows like FMJ'S ??? Would it still be consitant ? I'm just curious since it's pretty much a carbon arrow wrapped in a aluminum casing ! Just wondering if there could be a stiffer " inner core in the carbon " then what the scale might read on the outside aluminum casing ???? 
-Matt


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## L.I.Archer (Sep 6, 2010)

It works fine with FMJs. In fact, I have 2 dozen FMJ arrows that I tested on this device and they are very consistent all around the arrow.


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## MLabonte (Jan 19, 2009)

Good to hear !


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## henro (Oct 9, 2007)

Is there a list of everything needed?


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## skynight (Nov 5, 2003)

henro said:


> Is there a list of everything needed?


The link I posted in post 25 has parts and how to info.


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## archerm3 (Jan 4, 2007)

kc hay seed said:


> could you do the same thing with an arrow straightner? just roll the shaft and read the gage.


Yes you can if you attach a weight to the arrow shaft.


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## buckhead (Apr 7, 2006)

I'm not sure that an arrow straightener would work that well. 

When finding the stiff side of the arrow you would want the bearings to be as far apart as possible to get the most accurate reading.

An arrow straightener usually has the bearings placed fairly close together.


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## sp464 (Jan 19, 2012)

> 2lbs is quite close but 1.94 is the exact number


1.940067907 lbs (880 grams) but who's counting!  BTW... Nice spine tester


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## L.I.Archer (Sep 6, 2010)

sp464 said:


> 1.940067907 lbs (880 grams) but who's counting!  BTW... Nice spine tester


Thanks.


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## archerm3 (Jan 4, 2007)

buckhead said:


> I'm not sure that an arrow straightener would work that well.
> 
> When finding the stiff side of the arrow you would want the bearings to be as far apart as possible to get the most accurate reading.
> 
> An arrow straightener usually has the bearings placed fairly close together.


It's just simple Fizzics to determine the proper weight for the distance between bearings. You would need a higher weight directly proportional with the loss of distance between bearings for the same amount of measured deflection.

On the plus side you could use the reduced distance to determine where along the shaft a weak spot might be. Don't know what you'd do with that info.


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## Mordekyle (Aug 8, 2011)

A question for y'all:

About how much difference do you see between the weak side and the strong side of the shaft?

After spending $30 and a couple hours, I built a tester similar to this, but mounted vertically on a 2 X 10 board. 

I did the 3 eyebolts trick with the 5/8 x 7" bolt with stacked washers coming down through the eyebolts. Shaft is held at the ends with eyebolts coming horizontally through the wood. After not being impressed by the results, I hung the weight by a wire on the shaft. I even clamped on a pair of vise grips (as extra weight) to see if that made a difference.

I could care less if actual spine = manufacturers stated spine, but simply wanted to find strong/weak side in order to index and fletch arrows.

Long story short, I saw about .003" difference between strong and weak side. (Easton ACC)

Are you kidding me? Time and money to find out a meaningless .003?

WHat results do you get?


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## L.I.Archer (Sep 6, 2010)

Mordekyle said:


> A question for y'all:
> 
> About how much difference do you see between the weak side and the strong side of the shaft?
> 
> ...


.003" makes a huge difference at 40, 50 & 60 yards. If you index your arrows all the same way, they'll group much better.


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## Spike Bull (Aug 15, 2003)

If you are using it to find the stiff side and have free wheeling bearings all you have to do is put the shaft on the end bearings and press down in the center of the shaft with the third set and the high side will roll to the top, no need for a gauge or weights.


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## L.I.Archer (Sep 6, 2010)

Spike Bull said:


> If you are using it to find the stiff side and have free wheeling bearings all you have to do is put the shaft on the end bearings and press down in the center of the shaft with the third set and the high side will roll to the top, no need for a gauge or weights.


Yeaaaaaahhhhhhh...no. Roller bearings don't roll as easily as you may think.


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## dwagoner (Sep 27, 2007)

L.I.Archer said:


> Yeaaaaaahhhhhhh...no. Roller bearings don't roll as easily as you may think.


Man everything people post that you dont like you just love to take stabs back at them dont you???? Nice pile of washers and metal!!!! quit being such a smart azz if you dont like what someone says, guy was just trying to point out another option, it may not be totally intended for you and your piece of whatever but maybe for someone else and their ideas. did you ever think about that???? Prolly not cause you think your little contraption is the best eh????



L.I.Archer said:


> .003" makes a huge difference at 40, 50 & 60 yards. If you index your arrows all the same way, they'll group much better.


and you can simiply rotate arrows while shooting and index arrows also, but maybe youve never done that???? the difference in .003 straightness and the difference in his test under load and only difference of .003 is a big difference!! its not .003 on a resting shaft


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## buckman2591 (Feb 6, 2011)

Nicely put


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## buckman2591 (Feb 6, 2011)

I'll give someone a trail camera if they want to build me one


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## buckman2591 (Feb 6, 2011)

TTt


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## bill_collector (Jul 5, 2009)

Posting to find later


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## tack09 (Feb 13, 2009)

Guys I am not sure I understand the need for the spine deflection charts. If your dial indicator measures in thousandths, why do you need a conversion chart? If it deflects .400 is it not a 400 spine arrow? What am I missing here?


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## L.I.Archer (Sep 6, 2010)

tack09 said:


> Guys I am not sure I understand the need for the spine deflection charts. If your dial indicator measures in thousandths, why do you need a conversion chart? If it deflects .400 is it not a 400 spine arrow? What am I missing here?


An arrow won't deflect uniformly across it's entire circumference. One side may be stiffer than the other side due to the overlap of material when the carbon fibers are rolled into a tube. In order to get all your arrows to fly consistently from your bow, they should all have their stiff side oriented the same way.


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## tack09 (Feb 13, 2009)

LI, I am aware of the differing deflection around the circumference of the arrow shaft. I was refering to your post number 19 that was reffering to post #18. I dont understand why you would need the "spine-deflection chart" that is in the thread link in post #18. Thanks for your response but that "spine-deflection chart" still doesnt make any sense to me.


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## autoguns (Apr 27, 2010)

Nice work... I've been pressing my arrows to locate the spine. this looks like it may be easier to do...Thanks for posting it up...JW


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## buckman2591 (Feb 6, 2011)

Indexed 18 fletched arrows earlier in under 5 minutes. Well worth the time and effort to do this!


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## L.I.Archer (Sep 6, 2010)

Awesome!


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## deer slayer 11 (Nov 22, 2012)

So I decided to make my own spine tester. I just got my new shafts in the mail and wanted to find the stiff side of the shaft so I can flech them. but when I rotate the shaft. The needle barely moves. It also hits a high spot in two different spots. I have never used a spine tester before am I doing something wrong?


This is a video. Just click on it.


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## deer slayer 11 (Nov 22, 2012)

Here is some pictures of my spine tester.


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## skynight (Nov 5, 2003)

How much weight is that? Supports should be 28" apart and weight should be 2#. I think biggest thing is the dial caliper being under the weight. On my ram the weight pulls the shaft but does not compress the dial. The dial is under no pressure so just floats on the shaft.

That or you have really consistent shafts.


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## deer slayer 11 (Nov 22, 2012)

Yes it is 28 in and a 2lb weight. I just tried it with a old beman I had and it definitely had a weak side. It even would roll to the same spot. I just did the weight on top like the pic in the thread showed.


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## mbullism (Jun 25, 2009)

make sure the roller ball on the dial indicator is directly on the axis of the arrow shaft...if it is slightly forward or back and the arrow side is riding on the bevel/taper of the indicator point, even slightly, it can jamb things up enough to read as you describe...fwiw


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## deer slayer 11 (Nov 22, 2012)

I will double check it when I get home from work tonight. Thanks!!!


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## Big_Barr (Jun 15, 2012)

You can use more weight to find the stiff side of the arrow, say 3-4 lbs. Thats what i use and once i mark the stiff side i put just 2 lbs back on and spine the stiff side again except i dont need to find it now i just mark down what the dial read. I noticed that the black eagle and carbon tach arrwos are really difficult to locate the stiff spine compared to gold tips or easton. try more weight and see if that helps.


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## deer slayer 11 (Nov 22, 2012)

lol. yep I got the black eagle. The micro diameter at that. Thanks for all the great tips I have to give it a try and see what I can come up with.:thumb::thumb::thumb::thumb::thumb:


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## hoyt em all (Feb 20, 2005)

it's the return spring on your indicator , thats giving you inaccurate readings.i removed mine (spring) and relocated the indicator on top. so theres not much more than the weight of the indicator shaft and the friction of the indicator after that.i still have to tap my finger on the board to let things settle


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## deer slayer 11 (Nov 22, 2012)

Thanks for the tip on the spring hoyt em all. I have been trying everything that big barrr suggested with no luck:doh:. I have two hairs left to yank out before I breakdown and buy the ram spine tester. I really dont want to spend the $250 on one if I can make this thing work. I got tomorrow off so I have the hole day to mess with it. I will let you know how it goes. Thanks everyone! :set1_thinking:


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## deer slayer 11 (Nov 22, 2012)

:banana:Success!!:banana: Thanks hoyt em all:cheers: It was definitely that spring. I have tried it on several shafts and it works great.


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## deer slayer 11 (Nov 22, 2012)

Made a better way to hang my weight.


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## ctownshooter (Jun 6, 2013)

ttt


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## Pittstate23 (Dec 27, 2010)

That's over my head as well but the idea is awesome


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## [email protected] (Aug 23, 2008)

Hello, how long is that half inch bolt You used for Your spine tester, thank You.


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## shinobi3 (Jun 20, 2009)

Mrkd


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## n.vodden (Jun 28, 2012)

Good looking testers guys!

I've been tempted to build one of these for a little while to add to my tools, but as i've never indexed my arrows like this i'm curious as to how much difference it actually makes.

Real world examples, how many of you have noticed improvements in grouping that you can attribute to spine testing/indexing and how much difference does it actually make?

Just want to see if its worth the effort is all


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## dw'struth (Mar 14, 2008)

What is the actual name of that kind of guage? I searched harbor freight, but it didn't show one like you have.....


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## dw'struth (Mar 14, 2008)

dw'struth said:


> What is the actual name of that kind of guage? I searched harbor freight, but it didn't show one like you have.....


Never mind......found it.


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## bbjavelina (Jan 30, 2005)

How do you know when you're seeing spine deviation and when you're seeing un-straightness in the shaft?


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## L.I.Archer (Sep 6, 2010)

bbjavelina said:


> How do you know when you're seeing spine deviation and when you're seeing un-straightness in the shaft?


The needle on the dial moves. You just have to remember that the when the plunger goes into the dial, the needle goes up on the dial, and vice versa when the plunger goes out. On the tester, my dial is at the bottom, so as the plunger goes in (and the arrow deflects more), that tells me the weak side is at the bottom of the arrow shaft. That's when I mark the top of the arrow (where the weight is resting), because that's the stiff side.


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## xforce pse (Mar 9, 2011)

Should not all shafts be equal on both sides when you buy them new as far as bend goes ? then by right you should re-test the spine after a dozen shots or so because it will now be off of the original spine or stiffness that your cock feather is on and you will have to refletch ?


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## L.I.Archer (Sep 6, 2010)

xforce pse said:


> Should not all shafts be equal on both sides when you buy them new as far as bend goes ? then by right you should re-test the spine after a dozen shots or so because it will now be off of the original spine or stiffness that your cock feather is on and you will have to refletch ?


Not really, because there's a seam where the carbon joins to form the tube. The seam is usually where it is stiffest.


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## xforce pse (Mar 9, 2011)

How do you find the seam, is the only way is with a spine tester. Do the factories find the seam when they fletch arrows ? or do they just put the fletching on anywhere ?


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## L.I.Archer (Sep 6, 2010)

xforce pse said:


> How do you find the seam, is the only way is with a spine tester. Do the factories find the seam when they fletch arrows ? or do they just put the fletching on anywhere ?


Arrows fletched at the factory are just glued on anywhere. They won't spend the time indexing the arrows for you. That's what pro shops are for.


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## Alpha Burnt (Sep 12, 2005)

TTT...Resurrect this old thread for new ideas and experiences...


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## handirifle (Jun 9, 2005)

Maybe I am missing something in all this. I fully understand the weak side stiff side argument and do not doubt that an arrow will "always" flex to the weak side, BUT, every video I have seen of actual archers paradox (arrow flexing when shot) I have yet to see one flex up and down. So, if the weak spot happened to end up at the top or bottom why would it matter?

Also, the spine testers I remember, hung a 2lb (or whatever) weight from a hook, right next to the dial indicator as close to center of the 2 uprights as possible. A hanging point that is a couple inches either side of the arrow, is not deflecting in the true center of the shaft, length wise and will not give a true indication of actual deflection. Of course if you find an arrow that flies perfect for your bow, it only matters if you can match that, regardless of AMO spine. I realize that.

While on the weight subject. I see one of the testers had a 2lb weight on TOP of what looked like considerable weight of a shaft and bearings. Was the weight of those items added to the total weight?

Nice work on those things.


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## L.I.Archer (Sep 6, 2010)

[email protected] said:


> Hello, how long is that half inch bolt You used for Your spine tester, thank You.


8" bolt.


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## b0w_bender (Apr 30, 2006)

I like that you used existing hardware to build it. makes it a lot easier for harry home owner to build


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## Rudyonthefly (Dec 13, 2011)

handirifle said:


> Maybe I am missing something in all this. I fully understand the weak side stiff side argument and do not doubt that an arrow will "always" flex to the weak side, BUT, every video I have seen of actual archers paradox (arrow flexing when shot) I have yet to see one flex up and down. So, if the weak spot happened to end up at the top or bottom why would it matter?.


Those videos are most probably of recurve archers. Yes, their arrows will always flex and have archer's paradox when shot (even if the stiff side is opposite the burger button). It's a question of how much will it flex: the weak side on the opposite side of the burger button allows the arrow to flex more compared if the stiff side were there. It takes energy to flex an arrow. That comes from the bow. Energy absorbed by the arrow flexing is not available to accelerate the arrow; the arrow is slower. At 70m or 90m it makes a difference. So if you can find all the weak sides of you arrows and adjust all the nocks so that all the weak sides are in the same spot, all arrows will flex the same amount and thus end up at the same speed and thus your groups will be tighter at the longer distances.

Now for compound bows: there is essentially no archer's paradox if the centre shot is set correctly and the string is released properly. Most flexing in their arrows is in a vertical plane. Same principle about energy absorbed for flexing as described above still applies.

Bottom line: if you have your arrows "spine indexed" your arrows will group better (everything else being equal).

Hope this helps...

LIA: your DIY tester has given me an idea how I can modify my arrow straightener to become a spine tester. Thanks!


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## L.I.Archer (Sep 6, 2010)

Rudyonthefly said:


> Those videos are most probably of recurve archers. Yes, their arrows will always flex and have archer's paradox when shot (even if the stiff side is opposite the burger button). It's a question of how much will it flex: the weak side on the opposite side of the burger button allows the arrow to flex more compared if the stiff side were there. It takes energy to flex an arrow. That comes from the bow. Energy absorbed by the arrow flexing is not available to accelerate the arrow; the arrow is slower. At 70m or 90m it makes a difference. So if you can find all the weak sides of you arrows and adjust all the nocks so that all the weak sides are in the same spot, all arrows will flex the same amount and thus end up at the same speed and thus your groups will be tighter at the longer distances.
> 
> Now for compound bows: there is essentially no archer's paradox if the centre shot is set correctly and the string is released properly. Most flexing in their arrows is in a vertical plane. Same principle about energy absorbed for flexing as described above still applies.
> 
> ...


You're welcome. Always glad to help.


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## Jumpboots101 (Oct 20, 2010)

Tag


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## ruttnwapati (Sep 22, 2008)

Here's my version of a DIY indexer/spine checker with a BOM. Seen the postings here and reading on how to compression test arrows and finding their spine using LCA Press or any linear press as far as that goes. I found this method so inaccurate that I decided to build a tester. Compression testing with a press always had my arrows flexing the same direction no matter which way I rotated it. Let me explain, compressed an arrow and it flexed at 9 o'clock. So,l rotated that same arrow to 12,3,and 6 o'clock positions. Arrow still flexed at 9 o'clock position. I tried several arrows and a couple different presses at the bow shop that indexes them using this compression theory. Had same results.
As far as getting better results.......I really can't say. I practice outside from 40 to 80 yards. Nothing has jumped out 
at me indicating this is a must do in arrow accuracy. But, then again shooting outside with varied winds,light, rain and snow are more of a variable in my accuracy than this indexed arrow thing. Fun project and gets me into another level of tuning all my equipment. 
Good hunting and thanks to the posting OP for the idea.

Bill Of Materials (Home Cheapo, Harbor Freight and True Value Hardware)
1	36” Piece of unistrut 
1	¼”x6” mild steel flat bar
3	3/8” x 1” bolts w/lockwashers
3	Unistrut nuts (3/8”)
2	2 hole “L” unistrut brackets
2	threaded hooks
1	¼ x6 “ flat bar
1	Dial indicator with magnetic base
2	16 oz cannon ball sinkers (2lbs)
2	¼ x 20 x 2” bolts with nuts

Drill a thru hole centered (width) on your center plate ¾” back from front edge. Drill and tap two ¼ x 20 holes for jacking legs on the back edge of this plate to level the dial indicator mounting plate.
Drill 3/8” holes centered and 3/16” from top edge of both “L” brackets. File or grind to make a cradle for arrow to rest in after drilling holes.
Drill pilot holes in lead sinkers and let the hooks tap themselves into the inker body.
Mark center of the unistrut. Place center of flat bar at this center point of unistrut. Then mark 14 inches left and right of center. Secure “L” brackets at these distances. 
Use felt pad in the cradles and on the hook surfaces to make spinning the arrow smooth.


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## b0w_bender (Apr 30, 2006)

I have always wondered why the standard weight was 1.94 pounds. here is on of my theories the original creator Easton or Hoyt or who ever... measure the the pressure of the dial spring and subtracted that from the 2 pound weight so that the actual pressure on the shaft was 2 pounds? So spring is .06 pounds and the weight is 1.94 pounds giving a total deflection of 2#. OK Ok I know it doesn't matter one way or the other but that 1.94 number just makes me shake my head every time I see it. Who does that?


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## ruttnwapati (Sep 22, 2008)

I do not know either. I found those cannon balls at Sportsmans Warehouse and drilled alittle out of them to make the hooks tap into 
those sinkers. I'm slightly under 2#. Still heavier than the 1.94# specified. 
I'll buy your theory of .06# on the indicator spring :wink:


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## edthearcher (Nov 2, 2002)

dwagoner said:


> Man everything people post that you dont like you just love to take stabs back at them dont you???? Nice pile of washers and metal!!!! quit being such a smart azz if you dont like what someone says, guy was just trying to point out another option, it may not be totally intended for you and your piece of whatever but maybe for someone else and their ideas. did you ever think about that???? Prolly not cause you think your little contraption is the best eh????
> 
> 
> 
> and you can simiply rotate arrows while shooting and index arrows also, but maybe youve never done that???? the difference in .003 straightness and the difference in his test under load and only difference of .003 is a big difference!! its not .003 on a resting shaft


thank you


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## edthearcher (Nov 2, 2002)

I have wanted to build a spine tester for the last 2 years, you guys really lit the fire, question is there any advantage to using a digital as apposed to the dial indicator, i have looked at both on the harbor freight web site.

I wish all the naysayers would go away, every time some one has a good idea, smart asses jump in, great post


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## L.I.Archer (Sep 6, 2010)

edthearcher said:


> I have wanted to build a spine tester for the last 2 years, you guys really lit the fire, question is there any advantage to using a digital as apposed to the dial indicator, i have looked at both on the harbor freight web site.
> 
> I wish all the naysayers would go away, every time some one has a good idea, smart asses jump in, great post


The dial doesn't require batteries.


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## tered (Sep 29, 2014)

I bought one from harbor freight. Its a dial not digital. I think its what you want. I like the non digital.


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## bbjavelina (Jan 30, 2005)

Even on the swing-arm spine testers of years gone by the weight was 1.94. That was when there was no spring to skew the readings, and the arm was finely balanced. 

Here's a thought for you all -- on many brands of dial indicators the spring can be easily removed. This avoids erroneous readings, but only works on those machines that have the indicator mounted above the shaft. 

No matter which type of tester you use, you always have to consider the residual bend in the shaft. You can easily find the stiff side of the shaft while ignoring it, but not the true spine. It really depends on how closely you want your shafts matched. 

Best of luck to each of you.


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## kc hay seed (Jul 12, 2007)

i finally made one using the same dial indicator as the ones posted with two eye bolts 28" apart and two one lb. fishing sinkers with s-hooks to hang on shafts,works for me.


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## Outsider (Aug 16, 2011)

I have a question. It looks like the standard weight that you suppose to hand on the arrow is 1.94lbs. But is it the weight of the hanging weight itself? Or whole assembly of the weight? Like a bracket that hold the weight on the arrow.


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## ClintR (Apr 20, 2012)

http://www.harborfreight.com/1-inch-travel-machinists-dial-indicator-623.html

Is this what I need?


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## edthearcher (Nov 2, 2002)

Pysiek said:


> I have a question. It looks like the standard weight that you suppose to hand on the arrow is 1.94lbs. But is it the weight of the hanging weight itself? Or whole assembly of the weight? Like a bracket that hold the weight on the arrow.


every thing, total hanging weight


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## BluMeanie (May 5, 2014)

ClintRhodes said:


> http://www.harborfreight.com/1-inch-travel-machinists-dial-indicator-623.html
> 
> Is this what I need?


That will work fine. Acceptable accuracy for what we are doing, I would say. Repeatability is more important here than absolute accuracy, and generally these do well in that respect.

Note that it says the base is separate, so if you wish to use it for anything other than this you will need to purchase that as well.


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## ClintR (Apr 20, 2012)

BluMeanie said:


> That will work fine. Acceptable accuracy for what we are doing, I would say. Repeatability is more important here than absolute accuracy, and generally these do well in that respect.


Ok. It was the only one that came up in my search. Not really sure I was searching the correct text though


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## lucasm (Jun 24, 2008)

*My Spine Tester*





































Works real nice


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## edthearcher (Nov 2, 2002)

one hell of a piece of workmanship, many kudoos


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## hoyt em all (Feb 20, 2005)

just a" tip" about dial indicators (it may have been covered already) the tip of most if not all stock indicators has a ball tip on the end . so measuring a round arrow with a ball end indicator ,the tangent points have to line up the same to get a accurate reading as opposed to having a flat tip on the indicator . the tips are screw on and you can replace them. you can replace the ball end with a flat tip, file the tip flat (as square to the shaft as you can) or just leave the tip off


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## lucasm (Jun 24, 2008)

Yes I did change the tip after pics were taken


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## josh1974 (May 25, 2014)

Thanks for the inspiration....I just finished mine this morning.


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## tack09 (Feb 13, 2009)

josh1974 said:


> Thanks for the inspiration....I just finished mine this morning.


Very nice job. Can you tell us where the aluminum products cam from?


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## Outsider (Aug 16, 2011)

tack09 said:


> Very nice job. Can you tell us where the aluminum products cam from?


80/20. www.8020.net or their eBay store.


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## josh1974 (May 25, 2014)

Pysiek said:


> 80/20. www.8020.net or their eBay store.


Yep thats where they came from, but I got them from work.


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## Outsider (Aug 16, 2011)

josh1974 said:


> Yep thats where they came from, but I got them from work.


I made my arrow saw from this extrusion. I wish we have those at work. Little bit expensive to buy.


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## josh1974 (May 25, 2014)

Pysiek said:


> I made my arrow saw from this extrusion. I wish we have those at work. Little bit expensive to buy.


Yeah my saw and ASD is all made from this stuff. If I had to buy it, I dont know if I would have done it LOL.


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## Outsider (Aug 16, 2011)

Did you guys remove the spring from dial indicator?


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## josh1974 (May 25, 2014)

Pysiek said:


> Did you guys remove the spring from dial indicator?


I have not, but I may just to see if there is a difference.


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## killerloop (Mar 16, 2008)

Pysiek said:


> Did you guys remove the spring from dial indicator?


With the bearing arms.. I can do it with my eyes closed it's that much of a difference


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## lucasm (Jun 24, 2008)

Yes you have to remove the spring if not you won't get a true reading.


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## CarbonTerry (Jan 8, 2003)

I had all materials on hand except bolt/washers. The washers are a little light but I have brass cylinders that I will glue to the top of the bolt.
The standards are closer than 28" but all I care about is the consistency of the spine. The drilled hole thru the wood is pretty close so there is not much play for the bolt.


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## Outsider (Aug 16, 2011)

CarbonTerry said:


> I had all materials on hand except bolt/washers. The washers are a little light but I have brass cylinders that I will glue to the top of the bolt.
> The standards are closer than 28" but all I care about is the consistency of the spine. The drilled hole thru the wood is pretty close so there is not much play for the bolt.
> 
> View attachment 2204571


That bolt won't scratch your arrows?


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## ruttnwapati (Sep 22, 2008)

Pysiek said:


> That bolt won't scratch your arrows?


I bet nothing a little piece of mole skin or silencing material couldn't take care of.


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## BluMeanie (May 5, 2014)

ruttnwapati said:


> I bet nothing a little piece of mole skin or silencing material couldn't take care of.


Or even one of those little "furniture glide" dots with a stickyback...


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## killerloop (Mar 16, 2008)

Anyone want this for a head start project. Let me know went could work out something I'm sure


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## CarbonTerry (Jan 8, 2003)

No, the end of the bolt is sanded and polished....smooth as a baby's rear.


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## ruttnwapati (Sep 22, 2008)

killerloop said:


> With the bearing arms.. I can do it with my eyes closed it's that much of a difference


Second this. I placed bearings on the cradles and weight. Difference is night and day. Not saying that the cradles and weights without bearings on the "v" block and hanging weight won't provide an accurate reading. I found without the bearings it was a slow tedious process to find stiff plane. Bearings are definitely the way to go,removing the tension spring in the dial indicator and the point of the indicator removed are big plus.


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## turkeyhunter60 (Apr 19, 2010)

ttt for spine tester.


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## kc hay seed (Jul 12, 2007)

how do you remove the tension spring? is the shaft threaded? someone please P.M me the how to on this.thanks in advance!!


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## dw'struth (Mar 14, 2008)

The spring is easy to remove. Pop of the back cover of the dial and unhook the spring with some small pliars.


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