# String making jig as part of my bow press with a spring tensioner



## b0w_bender (Apr 30, 2006)

OK my bow press has become my archery Swiss army knife. It was a draw board and bow press in one and now I've added a string jig too. Basically what I did was create an insert that slips into the end of the press. This insert has an integrated spring to keep the fibers taught as the serving is applied. I have a set screw that holds it in a static position when I do the initial fiber wrap. I then tie it off and use the bow press crank to add the desired amount of tension to the string as I apply the servings. It is really rather handy to be able to loosen and tighten the string tension as you work on it. Enjoy!

Stay tuned I've also modified the bobbin to make it easier to apply the serving I'll start a new thread for that. (I'm still working out the details)


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## kc hay seed (Jul 12, 2007)

lets see some more deail pictures of your press.i have a jack like that and am trying to make a press.thanks


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## b0w_bender (Apr 30, 2006)

Sorry, probably should have referenced the original press thread in the initial post.
http://www.archerytalk.com/vb/showthread.php?t=1321214

That thread shows all the iterations I went through to get to the final press design.


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## Tunaboy (Oct 3, 2004)

Hey BB any chance you can hook up a lawnmower or beer dispencer?


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## b0w_bender (Apr 30, 2006)

beer dispenser, hmmm, hey not a bad Idea, I'll have to think on that one for a while.
:icon_1_lol:

:darkbeer:


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## Razorbak (May 26, 2004)

pretty sweet set up


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## Hammer0419 (Nov 21, 2005)

Very neat setup.


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## b0w_bender (Apr 30, 2006)

Hi guys thought I would share my latest string Jig modification
I've modified the single post jig seen in the videos to be a dual post. I used the original Jack insert and cut the foot off of it. I then cut a slot in it and mounted the spring from the single post insert into it. Now I have the same spring tensioning system only with the dual post setup.


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## drmajor (Nov 10, 2010)

What size is this square tube?
What type and poundage is the spring?
Who makes the spindles or is there a DIY version?


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## b0w_bender (Apr 30, 2006)

The tube is the portion of steel that came with the Jack, I believe it is 1.5" 
Spring came from McMaster Car here is the link

http://www.mcmaster.com/#9573k72/=b8k4vv

I bought the spindles from someone on Ebay but a bunch of people on here will make them for you if you ask.


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## CandianQuest (Mar 31, 2010)

What type of rail/guild did you use for the back 2 posts, and would a metal/welding supplier have some?


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## b0w_bender (Apr 30, 2006)

Honestly I don't know much about the posts since I purchased them from Ebay.


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## CandianQuest (Mar 31, 2010)

b0w_bender said:


> Honestly I don't know much about the posts since I purchased them from Ebay.


sorry i was a bit unclear, I mean the metal track they are bolted to, the metal channel, what did you use for that.


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## CandianQuest (Mar 31, 2010)

I retract my statement, it is just an open seam channel I can buy that at nearly any metal supplier...


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## dwagoner (Sep 27, 2007)

b0w_bender said:


> The tube is the portion of steel that came with the Jack, I believe it is 1.5"
> Spring came from McMaster Car here is the link
> 
> http://www.mcmaster.com/#9573k72/=b8k4vv
> ...


your only using a 176lb spring???? you should check some of these out, .3 inches of travel and its to 350lbs max load

http://www.mcmaster.com/#orders/=b95cft


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## b0w_bender (Apr 30, 2006)

dwagoner said:


> your only using a 176lb spring???? you should check some of these out, .3 inches of travel and its to 350lbs max load
> 
> http://www.mcmaster.com/#orders/=b95cft


that is 175 per inch of compression so an inch and 3/4 should equate to 300 lbs correct?


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## b0w_bender (Apr 30, 2006)

CandianQuest said:


> I retract my statement, it is just an open seam channel I can buy that at nearly any metal supplier...


In this case it is the tube that came with the Jack but I will be upgrading it. It is a bit too thin.


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## dwagoner (Sep 27, 2007)

b0w_bender said:


> that is 175 per inch of compression so an inch and 3/4 should equate to 300 lbs correct?


no that 176 is max load and its at 25% no way you can compress that 1.25" spring down 3/4".


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## mbw (Oct 11, 2010)

dwagoner said:


> no that 176 is max load and its at 25% no way you can compress that 1.25" spring down 3/4".


That spring is 4" long that bow_bender is using...its rated deflection at load is 25%(1") of its relaxed length of 4". So it would equal 176lbs/inch of compression. I wouldn't think it would have a problem reaching 300lbs.


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## b0w_bender (Apr 30, 2006)

mbw said:


> That spring is 4" long that bow_bender is using...its rated deflection at load is 25%(1") of its relaxed length of 4". So it would equal 176lbs/inch of compression. I wouldn't think it would have a problem reaching 300lbs.


Well I'm not an engineer but that's what I was thinking. Had me scared there for a second that perhaps I was on the wrong track. thanks for the input.

I have a 500 pound scale on it's way we will no shortly for sure.


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## CandianQuest (Mar 31, 2010)

Based off your design I am building a home made scale insert for the jack (bowbender, I admit to borrowing many of your ideas with the press, the jig {which I am making completely myself because talked to a friend who has a metal lath for making the pegs!}, and also for a draw board, the only thing this isn't going to be is a shooting machine as it will be bolted down in the end) and bought a 8" die cast spring that is 1-3/4" (so no buckling will occur reducing accuracy of pressure) with Approx 225lbs/inch of compression, so I will be able to mark the tube at exact increments where the tension on the string will be 100lbs, 150lbs, 300lbs, 400lbs and 450lbs, when I am done I will post pictures. It won't be for a while though because I need to go home first to get access to the welder and tap and die sets. I ran through the amount I will be spending, and it will likely be around 200, but as looking up those three machine prices online they would cost me over $900 and likely over $1050 if you include shipping.


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## b0w_bender (Apr 30, 2006)

looking forward to seeing it!


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## b0w_bender (Apr 30, 2006)

OK NUTS AND BOLTS PM'ed me and provided this description for the spring selection

Die compression springs are rated for precise,
repeatable, spring force performance. They are Generally,color coded.

Precision Springs are rated at
either 15% load, 20% load, or 25% load.

So, when you use die springs at the factory recommended load, and do no go beyond the recommended deflection rating percentage...

the spring should provide repeatable performance for million-plus load cycles.

if you have a 176 lb load rated spring, and you routinely go to 300 lbs or more... you MIGHT get there, but you are going beyond the design performance for this spring. Over time you are likely not to get repeatable results or a catastrophic failure.

Thanks for that info Nuts and Bolts!
So I say at around $10.00 for these springs it only makes sense that you buy the correct one.

So perhaps this would be a better Choice at 294 max load
http://www.mcmaster.com/#orders/=b9ypaa

or

this 398# max load version
http://www.mcmaster.com/#9584k72/=b9yr9c


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## CandianQuest (Mar 31, 2010)

The spring I ordered have a recommended spring load of 600# with a maximum of 900#, with a rate of 225# per inch of compression (if you compress the spring 2" the spring is pushing out at a force of approx 450#)... From working with cattle and building gates and presses from blue prints we usually doubled everything, so if it called for 2" square tube with 1/8" wall thickness we used 2" tube with 1/4" wall thickness, lets just say I am a firm believer of being unable to over-engineer something... My father jokes that whenever I build something I build it to death.


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## b0w_bender (Apr 30, 2006)

Ha CanadianQuest I like how you think. Even though you are a Canadian you think just like a typical American, if a little will do it well, then a whole lot will do it better!

Are you Canadian living close to the US border cause I think we're rubbing off on ya?


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## CandianQuest (Mar 31, 2010)

I did grow up in the southern cattle country of Alberta, but I truly think the innovative farmer/rancher personality doesn't have borders! If you look at the inventions that farmers and ranchers have made around the world you would be amazed, especially if they have long winters where they are cooped up in their shops making "improvements" to the equipment they bought years prior.


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## b0w_bender (Apr 30, 2006)

This probably comes as no surprise I grew up on a farm also.

:hail: :cow:


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## mbw (Oct 11, 2010)

Yeah...N&B is correct. Hadn't thought about the yeild strength or cyclic count of the spring.


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## CandianQuest (Mar 31, 2010)

Quick question, what is the shortest cable/ string you have ever heard of? I need to know for installation of the c channel once I finish all the jig parts


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## b0w_bender (Apr 30, 2006)

Well there is the yoke cable on a lot of the Hoyt's they are 10 or 12 inches? or something approximately close to that.


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## b0w_bender (Apr 30, 2006)

I got an email requesting this info so I figured I would post it here.

These are the steps and dimensions I used to make the insert

1) Cut the foot off the Jack foot insert that came with the Jack
2) Cut drill and tap a hole for the post plate this dimension is based on the width of your posts mine is 5.25" from the left (foot) end. Make sure your plate will clear the Jack as it rotates
3) Sand down 4 sides of a piece of 1.25" PVC pipe so that it fits inside the insert. The OD is 1.9"+- so you need to sand a bit on the belt sander to get it to fit the 1.5" interior of the insert.
4) Slide the pipe in flush with the right end
6) Drill and tap the hole for the .38 threaded rod spring stop all the way through both sides of the insert and the PVC pipe
7) Insert the 3/8" Spring stop threaded rod. Grind close to flush. Hit it with a hammer to flatten the threads to hold it in place.
7) Drill hole for a retaining screw through one side of the insert and the PVC pipe to keep the spring from moving out.
9) insert the spring into the insert from the left hand side of the insert all the way into the PVC pipe until it hits the spring stop. 
10) insert the spring retaining screw. rotate the spring the screw slips between the spring wires
11) Attach Post plate and posts
12) insert into Jack
13) from the side drill a hole through both the jack telescoping part and the insert and tap it for a .24/20 bolt. This bolt holds the jig from compressing while wrapping the thread.

Start making Strings!


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## Venado0 (Jun 6, 2010)

Just wanted to say thanks for taking the time and sharing your knowledge! Great info here....


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## b0w_bender (Apr 30, 2006)

Thanks for the kind words Vernodo0!

Here is an update to showing my latest improvements on the Jig. I got rid of those sissy post and replaced them with posts that are 6" tall and 1.5" across the base. The bases are .5" plate steel and are broader than most so they do not flex. I can wrap my threads with out the annoying flex in the jig giving me much more consistent thread tension.


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## b0w_bender (Apr 30, 2006)

OK I've made some significant upgrades to my string jig that I figured I would share with you guys. Since my tensioning spring is built into the base of my posts I have decided I should incorporate the string twister into the jig as a post. the pin in the twister is in the exact same place one of the posts would be so when I rotate the jig the string is in place all I need to do is increase the tension and add the center serving. Saves me from having to remove the string from the posts and moving it to a stretcher. You'll note that the posts are much beefier than the original this helps keep the tension on each strand consistent. The specs are 1" bolt that I cut drilled and threaded for the 1/4" post. The angle Iron is 3/8" by 2" steel angle. There is a thrust barring from McMaster car. To hold the post in vertical position when doing the layout there is a through bolt 10-24 I believe. I believe the posts are 6" high and 8" on center.


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## tryin (Jun 26, 2007)

really neat stuff here- a little late in the eve for me on all the math!
awesome set-up


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## jkcerda (Jan 25, 2007)

tag


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## b0w_bender (Apr 30, 2006)

Well since this got bumped to the top here is a video of how this thing actually works
UgICsMW_lBc&feature


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## b0w_bender (Apr 30, 2006)

Here is how I attached it to the bench.


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## b0w_bender (Apr 30, 2006)

For those interested I also posted this with drawings on my website
http://nwspinner.com/index.php/patsstringjig


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## drisk1 (Dec 26, 2013)

great design, thanks for sharing all the info


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## adventurejack (Oct 30, 2006)

saved


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## Airrichbows1 (Jul 23, 2016)

Neet device


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