# Spine tester completed



## gridman (Aug 26, 2007)

very nice job


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## bowhntr26 (Jan 18, 2008)

Looks Good budy


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## dmgiss (Mar 18, 2010)

very nice


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## Maui Rhino (Mar 13, 2010)

How about a parts list?


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## Jathinkysaurus (Oct 8, 2006)

Looks great! I have a few dial test indicators, looks like I have another use for one of them now.


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## b0w_bender (Apr 30, 2006)

does it fit to the standard?
(28" post to post and does the weight match 1.94 lbs.)

Not that it really has to just curious if you went to that effort.

Have you found significant inconsistencies in your arrows per matched set?


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## killitgrillit (Oct 10, 2007)

b0w_bender said:


> does it fit to the standard?
> (28" post to post and does the weight match 1.94 lbs.)
> 
> Not that it really has to just curious if you went to that effort.
> ...


I read that it was 26" between centers????? and the weight is 2#??? http://www.jamesmhill.com/Spine_Tester.html

I checked some G/T x-cutter pro's and they where nearly perfect, the cheaper the arrow the more deviation there was, I built this to find the stiff side of the arrow so I could line that up with the string.


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## buckman2591 (Feb 6, 2011)

killitgrillit said:


> Howdy all, just threw this togethor and thought I'd share it with ya'll. Easy build and was really suprised when I started testing a bunch of different arrows.


Where did you get the weight from?


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## killitgrillit (Oct 10, 2007)

buckman2591 said:


> Where did you get the weight from?


I took a piece of 2"aluminum bar stock and bored the back of it out and filled it with lead, then turned it on the lathe until I reached 2#'s


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## Jathinkysaurus (Oct 8, 2006)

Great bit of kit; you can spin-check your arrows for straightness with a high degree of accuracy, separate them into groups of consistent spine stiffness, and fletch them all with consistent alignment of the stiff side. I feel a little project coming on. If only I could shoot well enough to make it all meaningful!


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## swbuckmaster (Dec 20, 2005)

Parts list please

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## joe171 (Jan 8, 2012)

Thanks for the planes listed below on the link i want too try to make one
I have been going too a mfg web sight for that imfo some times it`s posted some times after several e mails 
Do you think I should build one 
Joe171


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## buckman2591 (Feb 6, 2011)

Of course!


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## joe171 (Jan 8, 2012)

How do I check spine on a 20 inch arrow if spine is measured at 26 inches


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## SWMoArcher (Sep 20, 2008)

killitgrillit said:


> I read that it was 26" between centers????? and the weight is 2#??? http://www.jamesmhill.com/Spine_Tester.html
> 
> I checked some G/T x-cutter pro's and they where nearly perfect, the cheaper the arrow the more deviation there was, I built this to find the stiff side of the arrow so I could line that up with the string.



http://www.eastonarchery.com/frequently-asked-questions Click on what is arrow spine.

Looks good, should work well to find the stiff side. I think traditional archers use the 26" 2lb method. I don't know why there's 2 different methods.


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## b0w_bender (Apr 30, 2006)

Hi guys 
I think this is really cool and having it match the actual Archery trade associations specification is completely immaterial to it's intended functionality. I mean if what you are interested in is finding inconsistencies from arrow to arrow and the week side of the arrow then the dimensions and are pretty much immaterial. But if you want to actually build to spec then here is the tech guide directly from the Archery Trade associations website.

28" from post to post. The arrow must be 1 inch larger or 29" and the weight applied to the arrow is 1.94 pounds. (Where the heck did they get that from?)
http://www.archerytrade.org/images/documents/TechGuides/ARR202.pdf
Note this standard is for "Non-Wood Arrow Shafts"

I'm not trying to be a stickler prick, I hate it when people get hung up on the whole conformity thing. I'm just clearing up some disinformation so if others want to build to spec they can be fully informed about the minutia. 


OK this whole 1.94 pound thing, I'm told came from Easton. I always assumed that that the odd number was because it was an English conversion from some other round number in a different unit of measure like kilograms or something. I just went to calculateme.com to run the conversions to confirm my hypothesis and it seems to have no rime or reason whats so ever. Comes out to approximately .88 Kilo, 879.96 grams, 13580 Grains.. and so on. I think it just happened to be the weight that they had laying around and had always used so it became the standard. Either that or the guy who milled it out was drunk and they just went with what he came up with something is screwy because why would you choose 1.94 pounds to be a standard.


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## SWMoArcher (Sep 20, 2008)

b0w_bender said:


> Hi guys
> I think this is really cool and having it match the actual Archery trade associations specification is completely immaterial to it's intended functionality. I mean if what you are interested in is finding inconsistencies from arrow to arrow and the week side of the arrow then the dimensions and are pretty much immaterial. But if you want to actually build to spec then here is the tech guide directly from the Archery Trade associations website.
> 
> 28" from post to post. The arrow must be 1 inch larger or 29" and the weight applied to the arrow is 1.94 pounds. (Where the heck did they get that from?)
> ...



I agree with what you said about its intended functionality. The OP did an excellent job with this. I've been meaning to make one for the last couple of years for the same reasons as him, to find the stiff side and weed out arrows that were significantly different than others. Unfortunately my fabricating skills are lacking.


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## b0w_bender (Apr 30, 2006)

Ya I hear ya I think I'm on the Mach II model my first 2 attempts at building a spine tester have been pretty ugly and I have a pretty low threshold when it comes to aesthetics. they just didn't function as well as I would like. killitgrillit's looks pretty nice. 

Just curious once you find the weak side of the arrow how do you orient that? Up, down, left right?

Are you a release or finger shooter?


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## killitgrillit (Oct 10, 2007)

b0w_bender said:


> Ya I hear ya I think I'm on the Mach II model my first 2 attempts at building a spine tester have been pretty ugly and I have a pretty low threshold when it comes to aesthetics. they just didn't function as well as I would like. killitgrillit's looks pretty nice.
> 
> Just curious once you find the weak side of the arrow how do you orient that? Up, down, left right?
> 
> Are you a release or finger shooter?


Thx ya'll for the comments.
I'm marking the stiff side of the arrow and puting that in line with cock vane, I just started playing with this to see if i could get the fliers fixed. I'll have 3-4 arrows that will group and then 1-2 fliers.
There will be a lot of experimenting and listening to ya'll experts.
And I'm a release shooter.


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## Spike Bull (Aug 15, 2003)

Just a guess, but I would bet that 1.94 pounds is what it took to get that 28" shaft to a corresponding deflection, 1/2", or .500 spine! The 28" shaft is not new to archery and the difference from what the trad guys do is probably based on the non-wood aspect of modern arrows.


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## cdp99 (Aug 14, 2010)

joe171 asked: How do I check spine on a 20 inch arrow if spine is measured at 26 inches?

Just use a shorter distance between supports and, if light spined, change the weight. Here's a picture of one I threw together for splining short, low spine kid's arrows:









It's based on the Hill design with 22" between the shaft supports and a 1.25# weight. I don't go much by ASTM or AMO spline but to find what they are I used a 1413 Easton shaft and it's ASTM deflection from the Easton catalog (2.036" deflection with 1.94# and 28" span) to derive a conversion factor for Hill's scale for determining the ASTM spine. For the one pictured, multiply the deflection from the Hill scale by 2.7 to get the ASTM deflection. About the only time I use the ASTM spine is for playing around with Stu's Dynamic Spine calculator. I mostly use spine testing for grouping shafts and finding their stiff side.


Just a FWIW, I tried to calculate the deflection using the beam bending equation
deflection= Weight * Length^3 / (48 * Mod_Elasticity * Mom_Inertia) 
and couldn't get a good fit with Easton's data for their 1214 thru 1816 shafts- had an error range on the deflection of -1% to +8%.


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## aread (Dec 25, 2009)

The 1.94 pounds for the weight is actually 880 grams (not grains)

It's probably as simple as that was the weight that somebody had on hand when the standard was established. 

If you are checking for spine compared to other arrows or spine consistency, the 26" or 28" is not important. It may even be a little more convenient because many of us cut our arrows to less than 28". You are only limited in that you can't compare arrows to the official standard.

Very nice job on the build.

Allen


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## Garceau (Sep 3, 2010)

The above pic is very similar to what I have in my head.

A few things that are bothering me as Im a slight freak when it comes to some things - 

The portions that hold the arrow appear to be bearings. 2 on each side so you can utilize as a spinner - I like this.

Is there any commercially named part that holds those bearings? What Im concerned about is me not getting the holes drilled properly and having some type of slight bind in the arrow shaft.

Damn I wish I had access to a little more machining tools


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## HCATech (Jul 12, 2011)

Looks good OP. Love to see tools and equipment fellow archer's build.


He is a pic of one that we put together inexpensively also.


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## CarbonTerry (Jan 8, 2003)

Sooooo... how many .x00"s would would indicate a weak/stiff spine ??


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## Garceau (Sep 3, 2010)

HCATech said:


> Looks good OP. Love to see tools and equipment fellow archer's build.
> 
> 
> He is a pic of one that we put together inexpensively also.
> View attachment 1541735


Awesome 

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## DssBB (Feb 21, 2010)

Garceau

To answer your previous question about what is commercially available to hold the bearing. The 2 bearing should be mounted on Shoulder Bolts which are precision ground to tight tolerances and will allow the bearing to fit and ride on their shoulder with minimal play and help guarantee concentricity in the bearing rotation. 
I also built quite a few spine testers a couple of years ago and discovered that although the design of using two sets of bearings like the RAM spine testers allowed for the spine tester to be used as an arrow spinner it also contributed to some false readings. The reasons behind my claiming of the false reading is when you apply the load (1.94 lbs) to the arrow and it begins to flex, the radial contacting surface of the arrow depending on the arrow spine will no longer ride on the true diameter of the bearing but will instead be in contact with the edge or corner radius on the inside edge of the bearings. The weaker the arrow spine, the more flex in the arrow and the less contact between the arrow and the true running diameter of the bearing.
The V roller concept used by Bear Paw archery in their spine tester guarantees constant and a true arrow surface to roller contact regardless of the amount of deflection within the arrow. The arrow will always ride with 2 points of contact in the rollers V groove.

Food for thought....There are also more ways to apply 1.94 lbs of flex to an arrow then hanging a weight on it or adding weight from the top.


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## Garceau (Sep 3, 2010)

Excellent thank you ....

,

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## Garceau (Sep 3, 2010)

DssBB

I may have came up with a solution to the binding issue with standard roller bearings.

I need to get to the local bearing shop and see. But i noticed a deal called a flanged bearing. 


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## DssBB (Feb 21, 2010)

Garceau,

Flanged bearings will not work. They are designed with a lip on them so they can be pressed into a bore and the lip prevents them from being installed too deep or pressed through. Standard roller bearings do work but should be mounted on shoulder bolts with a washer or spacer between the back face of the bearing and what it's being mounted to to prevent the outer race from binding. As mentioned previously, utilizing V groove rollers IMO work best.
Here are a couple of images of my Spine Testers I have made in the past. Being the main beam of the tester is extruded aluminum with precision slots extruded into it, the roller supports I made were also designed with two keyed bosses on the bottom face allowing the roller supports to also be moved in or out along the main beam while remaining square and perfectly in line.


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## ColbyKiller (Sep 22, 2008)

Nice looking setup.


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## 10%FOC (Dec 4, 2012)

Ok, so how much would any of you machinists charge to make a spine tester? And an arrow spinner for that matter?


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## bfelver (May 13, 2012)

The industry standard on checking arrows is 28 inches center and using 1.94 pounds . U will still accomplish the same thing ur reading will just be diff . Mine i built is like a ram > i can change the center distance so i can check made up arrows since i wasnt blessed with an awsome draw length lol


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## tushar897 (Dec 18, 2012)

Less powerful bows require arrows with less spine. Less powerful bows have less effect in deforming the arrow as it is accelerated from the bow and the arrow must be "easier" to flex around the riser of the bow before settling to its path. Conversely, powerful bows need stiffer arrows with more spine, as the bow will have a much greater bending effect on the arrow as it is accelerated.An arrow with too much spine for the bow will not flex and as the string comes closer to the bow stave, the arrow will be forced off to the side. Too little spine, or flexion, will result in the arrow deforming too much and being propelled off to the other side of the target. In extreme cases, the arrow may break before it can accelerate, which can be a safety hazard.
---------------------------------
*website templates*


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## Vortex69 (Jul 8, 2007)

DssBB said:


> ...... The reasons behind my claiming of the false reading is when you apply the load (1.94 lbs) to the arrow and it begins to flex, the radial contacting surface of the arrow depending on the arrow spine will no longer ride on the true diameter of the bearing but will instead be in contact with the edge or corner radius on the inside edge of the bearings. The weaker the arrow spine, the more flex in the arrow and the less contact between the arrow and the true running diameter of the bearing.......


Maybe I'm misinterpreting your statement but the way I see it is this: With the weight placed on the arrow, it (the arrow) already has more bend in it that it will ever have from other forces while in the fixture. This means that the shaft is already contacting the bearings at their inner most edges (twoards the weight), therefore, those contact points will not change,....at least for the purposes of this conversation. The exception to this would obviously be a case where there were bad or loose bearings.


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## swbuckmaster (Dec 20, 2005)

You are reading to much into spine. A spine tester only tells you what spine your arrow is nothing else. 
Arrow spine charts are a starting point only. The bow will ultimately tell you what arrow it wants to shoot well. I believe the only way you can find the dynamic spine of the arrow is with a hooter shooter. Dynamic spine isn't the same as arrow spine. 
Dynamic spine is the direction the arrow wants to bend under load. It could want to bend a certain way because the end might not be squared. The nock might not be squared. It might have a stiff side. The arrow may have been hit by another arrow ect. The dynamic spine can change over time. It needs to be checked. It cant be checked by a spine tester. It needs to be shot. 
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## buckman2591 (Feb 6, 2011)

I simply use my spine tester to find the stiffest side of the shaft so I can index all of my shafts the same. I used to think way too much into it and then I remembered what my grandfather has told me time and time again: Keep It Simple Stupid!


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## glücklicher (Aug 23, 2008)

buckman2591 said:


> I simply use my spine tester to find the stiffest side of the shaft so I can index all of my shafts the same.


another very accurate way http://www.archerytalk.com/vb/showthread.php?t=1537989


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## Vortex69 (Jul 8, 2007)

swbuckmaster said:


> ..... Dynamic spine isn't the same as arrow spine.
> Dynamic spine is the direction the arrow wants to bend under load....


Absolutely correct!!!

However, the dynamic arrow load comes from more than one factor and because of that, makes it a bit more complicated. For instance, the average archer that tries to orient the arrows spine by shooting it may have the results scewed because of form or bow tune issues both of which will have an effect on dynamic spine. Spine checkers are by no means a perfect solution but they do help getting things roughed in which helps down the line.


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## DssBB (Feb 21, 2010)

Vortex,

You are correct in what your saying with the arrow flexed under it's 1.94 lb load and the arrow making contact on or near the inner edge of the bearing depending on it's spine and would always rotate on it's current contact points. The point I was making was if someone where to build a spine tester with loose bearings or have them improperly mounted as to allow for play or excessive bearing movement then utilizing the inner edges of the bearings as contact points may not give you correct readings each time. By using V groove rollers as I've used in the spine testers I've made would help to eliminate any potential errors as the arrow would always remain constant in the center of the V grooves and any side forces or play would be eliminated thus improving accuracy and consistency.
I also realize that as you stated, spine testers are by no means a perfect solution but do help to get things started.
I guess from designing and building optical disc molds for over 25 yrs embeds over kill in my own personal projects. In the end it's all about the enjoyment of the sport and how each of us can apply our own knowledge and abilities within the sport.


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## swbuckmaster (Dec 20, 2005)

Bow tune and poor form wont effect dynamic spine. You can put an out of tune bow on a hooter shooter and it will still find the dynamic spine of your arrows.

A spine tester will just make you think you've solved the problem with dynamic spine issues. They may still be there because of the reasons i stated in my previous statement. 

Im not totally convinced a spine tester can find the dynamic spine. It might be better than doing nothing though as stated above. What its made for is to you a deflection reading on your arrow indicating how much bend it has with a certain amount of weight so you know what spine arrow it is and thats about it. Carbon arrows are different animal altogether than aluminums when it comes to finding the actual dynamic spine. Aluminum arrows seen to be easier.

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## Vortex69 (Jul 8, 2007)

swbuckmaster said:


> Bow tune and poor form wont effect dynamic spine..........



Maybe I was a bit unclear. Dynamic spine is just that...dynamic spine. It is what it is. When I said that form/tune would have an effect on DS I should have said form/tune will effect the "amount" of DS. For example, if you have the perfect theoryetical static arrow shot out of a bow with a significant amount of vertical or horizontal nock travel and a fair amount of hand torque, you will increase the load on the arrow and therefore change the DS relative to that same arrow being shot without the nock/torque issue.


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## Hang 'em High (Feb 16, 2011)

great thread


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## ron w (Jan 5, 2013)

the point is that without expensive equipment and allot of math, dynamic spine is impossible to establish and that static spine is just an indicator of whether the arrow shaft is stiff enough to recover from dynamic compression on the shot. that's all been pretty well established many years ago. for most of us a spine tester sorts our arrows and makes liars out of the arrow manufacturers. for all practical purposes, the most important part of our having a spine tester.


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## okherp (Aug 23, 2010)

Far more complicated than I am willing to worry about just to shoot my bow for hunting. But I do have one question:

As a scientist, I noticed the weight has 2 hangers separated by what looks to be about 1". It probably doesn't make too much of a difference, but would the spine flex be _significantly_ affected by the weight being distributed over 2 points as opposed to one?


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## kc hay seed (Jul 12, 2007)

what would floating them in the bathtub do? stiff side down??? just asking.


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## swbuckmaster (Dec 20, 2005)

kc hay seed said:


> what would floating them in the bathtub do? stiff side down??? just asking.


It just gets them wet! 

To line up the dynamic spine on your carbon arrows they need to be shot. No easy way around it!

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