Converting swaged aluminium shafts to uni-bushes - unexpected problems

AndyS

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A large proportion of our club arrows have been donated by members over a lot of years, and as a result there's quite a mix of shaft and nock types, which when combined with variations on the serving on some of the club strings means it can be quite a challenge to find a set of arrows of the right length that will actually fit the string on a specific bow!

So I'm trying to standardise on a cheap G-nock equivalent that gives a good fit on standard shop-bought dacron strings, and re-serving existing strings where necessary to get a uniform serving diameter and nock fit!

A lot of the shafts have most markings worn off, so a bit of time with a micrometer and I had the outer diameters of a lot of the candidates and bought a few dozen of the required uni-bushes. I always opted for the xx16 option as I figured if these were slightly loose on say a 1716 bush in a 1714 shaft, then a thin layer of epoxy should cope with it, but a 1714 bush wouldn't work if a 17xx shaft turned out to be a 1716 when I cut the swage off!

Many of the conversions have gone well and proved to be well worth the effort when used at a try-it we ran this weekend, where any arrow (that went with us) would fit any serving on any bow :cheerful:

BUT.... I now have a few dozen arrows where I've cut off the swaged end (I cut all the shafts where I thought I'd got the necessary uni-bushes in one go) and the "correct" uni-bush isn't even close to going into the shaft:confused:.

Looking closer, there appear to be two issues:
  • On some older non-anodised shafts (which appear to be Easton) the wall thickness appears to be thicker than .016 - more like .020 or .021
  • On other shafts the rear of the shaft tapers slightly before it gets to the swage that I cut off :duh:

In both cases, the hole in the end of the cut shaft is too small for the expected uni-bush to fit, but the next size smaller bush is very loose.

Obviously with the tapering shafts I could trim another 1/2" or more off the back to lose the taper - but I'd rather not if I can avoid it.

I'm tempted to try epoxy to fill the gap and use something like wraps of serving thread to keep the bush central in the shaft whilst it sets - but wondered if anyone here has been through this problem and has a proven method to fit an under sized uni-bush?

Or does anyone know of any similar bushes to the Easton offerings, but in slightly different diameters (that will still take a g-nock)?

Thanks.
 


4d4m

Member
Can you sand down the outer diameter of the non-fitting bushes? You could use a power drill or dremel. Find a parallel drill bit that is the closest fit inside the bushing. Wrap with a little tape if it's too loose. You want a friction fit that stops the bit spinning inside the bushing but still allows the bushing to be pushed on and off easily. Then chuck the bit in a drill and gently spin it while holding the narrow part of the bushing against some sandpaper. This would work but would be time consuming if you're doing a lot. Much quicker for larger numbers: if you know someone local with a lathe (e.g. model engineer or hobbyist) you could get them to size down the bushings for a small consideration.
 


geoffretired

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I have never done what you are wanting to do, but I have used one shaft inside another for other purposes. Is it possible to make sleeves from one thinner shaft to take up the slack?
 


dvd8n

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If you stick with one manufacturer then aren't the groove sizes the same no matter what the fitting of the nock is? Or am I just hopelessly naive...
 


AndyS

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Can you sand down the outer diameter of the non-fitting bushes? You could use a power drill or dremel. Find a parallel drill bit that is the closest fit inside the bushing. Wrap with a little tape if it's too loose. You want a friction fit that stops the bit spinning inside the bushing but still allows the bushing to be pushed on and off easily. Then chuck the bit in a drill and gently spin it while holding the narrow part of the bushing against some sandpaper. This would work but would be time consuming if you're doing a lot. Much quicker for larger numbers: if you know someone local with a lathe (e.g. model engineer or hobbyist) you could get them to size down the bushings for a small consideration.
I like your thinking, but unfortunately I do have quite a few to do and suspect this might still be quite time consuming even with a lathe (even if I knew someone with one)
 


AndyS

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I have never done what you are wanting to do, but I have used one shaft inside another for other purposes. Is it possible to make sleeves from one thinner shaft to take up the slack?
I'll investigate this one when I get chance, it should be quite quick if I can find suitably sized shaft offcuts!
 


AndyS

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If you stick with one manufacturer
I don't know. But the only local option for one manufacturer of both nock types would be Bohning - and I can't find any information on Bohning groove sizes.
Converting the glue-ons to push-ins also makes its much easier to swap a damaged nock on the spot.
And of course I'm already committed to this route because I've already bought the new nocks and bushings!
 


geoffretired

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If you have any old lengths of electrical cable; separate strands could be wound round the nocks. Or blister packs can be cut up to make a wrap.
Perhaps a wider plastic straw. You may need to split it down its length and trim some off to prevent an overlap.
 


LionOfNarnia

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If I had the same issues I'd try wrapping a turn or two of PTFE tape around the nock 'shaft'.

- It's cheap enough to be worth a go, and can be useful in many other DIY situations too.
 


geoffretired

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If the gaps between the items are right, one possible solution might be heat shrink. Very small gaps, insulation tape?
 


AndyS

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Thanks for the ideas guys,

The problem is the fit of the bushings into the shaft - the nocks themselves fit the bushes fine, though PTFE tape does work well for slightly loose nocks - I already use that to get a better fit from Beiter In-Outs on my ACGs.

I'd wondered about insulation tape but I suspect it might scrape off if I try for a friction fit, and I'm not sure how well it will glue - the bushings ideally want to be semi-permanent.

Still quite liking the arrow shaft sleeve idea, but not had chance to see if its workable.
 


geoffretired

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If arrow shaft sleeve is too thick for the gap, the cover of a AA battery or similar battery can be removed from dead batteries and cutting won't be too difficult with strong scissors etc.
 


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