Clearance on register of a set tru chuck?

BGHansen

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Curious about the clearance between the register on the backing plate and chuck on a set tru chuck. I'm assuming the best way to set one up is to take the register to net to the chuck for starters. Set the chuck in place and transfer the bolt holes from the chuck to the backing plate. Then remove the chuck and take 0.005" - 0.010" off the register to give you 0.0025" - 0.005" of radial adjustment.

Thanks, Bruce
 
Curious about the clearance between the register on the backing plate and chuck on a set tru chuck. I'm assuming the best way to set one up is to take the register to net to the chuck for starters. Set the chuck in place and transfer the bolt holes from the chuck to the backing plate. Then remove the chuck and take 0.005" - 0.010" off the register to give you 0.0025" - 0.005" of radial adjustment.

Thanks, Bruce

Hey Bruce,
I don't know if this will help but I just got a Yuasa Accu-chuck. They call it an adjust-true chuck but unlike every other similar chuck, they only use three adjusting screws instead of four. Yuasa just has to be different!

Anyway, I measured my chuck and backing plate for you and got a 3.150" ID for the recess in back of the chuck; this receives the snout of the backing plate, which measured 3.1417" OD. So, just a bit over 0.0080" of adjustability. Hope this helps.
 
Hey Bruce,
I don't know if this will help but I just got a Yuasa Accu-chuck. They call it an adjust-true chuck but unlike every other similar chuck, they only use three adjusting screws instead of four. Yuasa just has to be different!

Anyway, I measured my chuck and backing plate for you and got a 3.150" ID for the recess in back of the chuck; this receives the snout of the backing plate, which measured 3.1417" OD. So, just a bit over 0.0080" of adjustability. Hope this helps.
Perfect! I figured there had to be a little clearance. Looks like I have a POTD tomorrow.

Thanks, Bruce
 
I went through this same thing when I made the adapter for the 5" Bison Set-Tru for my old HF 8x14 lathe. Looking at the dimensions for the chuck & the adapters in the Bison Catalog, they list only .0008" clearance. So ok, that's what I did. Like your idea, I made the register for the adpater for a close fit, transferred the mounting holes, then turned down the register .001". Well it wasn't enough to allow adjustment. I forget but I think I went with .006" clearance. I took off like 2 thou at a time until I was able to adjust the TIR properly. That 5" chuck was used so though so I'm not sure if that was due to an issue with the chuck.

However .0008" just doesn't seem like it enough. I just checked Gator's catalog & they list the same exact thing, .0008". In fact their dimensions are pretty much identical there. I'm not surprised due to someone who had left Bison & went to work for Gator but nope I'm not saying anything. :) Anyways, when I turned the stock 3 jaw chuck plain back chuck that came with my lathe into a Tap-Tru as well as making my ER40 chuck for the lathe a Tap-Tru, I had to do the same, about 5 thou. I've never measured my 2 Bison Set-Tru chucks to verify the clearance but I think they have to have more than .0008" like they list.
 
The adjusting screws have a separate head that projects into the space where the backplate register sits. Those heads only have so much travel so you can't make the snout too small but I should think an OD delta of 0.008 to 0.0100" should work fine. Or am I overthinking this?
 
I agree, I don't think anymore than 10 thou is necessary. I would say start with 5 thou & go from there. Won't really hurt if the clearance is on the larger side but I would say keep it as minimal as you can, not only to adjust TIR to the lowest you can but also considering if you will ever use the adjustable chuck to dial in parts.

If you do use it like that as some do like for production work, you would have to determine how much clearance you would want. I don't use my adjustable chucks like that, I only adjust for lowest possible TIR for the clamping range that I use the most. For example, I adjust my TIR at 1"dia with my 6 jaw Set-Tru & 1.5"dia with my 3 jaw Set-tru. TIR won't be accurate through the whole range of the scroll but if it's a well made chuck it should be pretty good. My Bison chucks are pretty damn good.

I say minimal clearance as needed only cause it will help save you time adjusting TIR whenever you have to disassemble & reassemble the chuck. May not be that often but you should clean it periodically.

Sorry for the semi hijack but here's another subject that people seem to have different opinions on. Whether or not to leave the adjustment set screws tight or loose after adjusting TIR. I leave my adjustment screws tight. Some people say that after you adjust TIR & tighten up the chuck mounting bolts, you should back off the adjustment screws. I don't agree with that.

For one, leaving those adjustment set screws loose, there's a chance of those set screws backing out & flying out. Unlikely to happen & you should notice any of them backing out before they could fly out. Leaving the set screws tight gives you less chance of the chuck from being bumped out of true, the very disadvantage of a Tap-Tru. But I've never had on of my Tap-Trus get bumped out of alignment.

My Bison Set-Tru check have pretty large diameter set screws, almost twice the size that were on my old Gator adjustable chuck. I never had a problem with the smaller set screws on that Gator chuck but there must be a reason why Bison choose to use such large screws.

What say you guys?
 
I agree, I don't think anymore than 10 thou is necessary. I would say start with 5 thou & go from there. Won't really hurt if the clearance is on the larger side but I would say keep it as minimal as you can, not only to adjust TIR to the lowest you can but also considering if you will ever use the adjustable chuck to dial in parts.

If you do use it like that as some do like for production work, you would have to determine how much clearance you would want. I don't use my adjustable chucks like that, I only adjust for lowest possible TIR for the clamping range that I use the most. For example, I adjust my TIR at 1"dia with my 6 jaw Set-Tru & 1.5"dia with my 3 jaw Set-tru. TIR won't be accurate through the whole range of the scroll but if it's a well made chuck it should be pretty good. My Bison chucks are pretty damn good.

I say minimal clearance as needed only cause it will help save you time adjusting TIR whenever you have to disassemble & reassemble the chuck. May not be that often but you should clean it periodically.

Sorry for the semi hijack but here's another subject that people seem to have different opinions on. Whether or not to leave the adjustment set screws tight or loose after adjusting TIR. I leave my adjustment screws tight. Some people say that after you adjust TIR & tighten up the chuck mounting bolts, you should back off the adjustment screws. I don't agree with that.

For one, leaving those adjustment set screws loose, there's a chance of those set screws backing out & flying out. Unlikely to happen & you should notice any of them backing out before they could fly out. Leaving the set screws tight gives you less chance of the chuck from being bumped out of true, the very disadvantage of a Tap-Tru. But I've never had on of my Tap-Trus get bumped out of alignment.

My Bison Set-Tru check have pretty large diameter set screws, almost twice the size that were on my old Gator adjustable chuck. I never had a problem with the smaller set screws on that Gator chuck but there must be a reason why Bison choose to use such large screws.

What say you guys?

I just got this chuck and still have to make a D1-4 backplate for it but I already know I'll leave my adjustment screws tight. It makes no sense to loosen them, in my opinion.
 
Give it a generous clearance of 1/16" or more, this is where the adjusting screws will contact the back plate. The ability to adjust it is the whole point is it not?

Adjust the chuck EVERY time that you change jaws or part diameter, if you have dozens of jaw sets this is necessary.
The register does not locate the chuck the screws do so the clearance is unimportant as long as it is enough to cover the range needed. On the 2 NC lathes that I regularly run the clearance is 1/8" or so.

There will come a time when you will need to run a job using a sketchy at best set up and a wide range of adjustment will be a big help, such as this.
10" long welded soft jaws, I may have to offset the chuck .040" from one part run to the next which is about twice per year.
2000 parts per order, it is a mess of chips.
 
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