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Clearance on register of a set tru chuck?

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BGHansen

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#1
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
 

mikey

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#2
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.
 

BGHansen

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#3
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
 

darkzero

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#4
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.
 

mikey

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#5
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?
 

darkzero

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#6
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?
 

mikey

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#7
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.
 

Wreck™Wreck

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#8
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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mark_f

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#11
I have a question. It has been too many years since I have seen a set true chuck and I never had to disassemble one. When you speak of clearance, such as .010", that means you can move the chuck .005" in any direction?

Also, the set screws for adjusting the chuck, should they be flat on the end that goes against the chuck?

I am building a set true ER 40 collet chuck. I was thinking about using 1/4" set screws. They should be large enough aren't they?
 

darkzero

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#12
I have a question. It has been too many years since I have seen a set true chuck and I never had to disassemble one. When you speak of clearance, such as .010", that means you can move the chuck .005" in any direction?
Yes


Also, the set screws for adjusting the chuck, should they be flat on the end that goes against the chuck?
Most definitely! You don't want anything like a cup point digging into your backplate, if you do you'll risk raising a burr & not be able to remove the chuck from the adapter if the raised burr is larger than the mating clearance. The set screws aren't for holding, they're just for adjustment.

Normally the set screws are in the chuck & contact the adapter. I'm not sure how you are making your adjustable ER40, by the way you described, sounds like you are making it so the ER40 chuck fits inside the adapter & the set screws are on the adapter. No matter, same difference.


I am building a set true ER 40 collet chuck. I was thinking about using 1/4" set screws. They should be large enough aren't they?
1/4" would be fine. ER40 collet chucks are very light. Even if you are converting one to an adjustable/Set-Tru type, I doubt it would weigh as much as an adjustable scroll chuck.

To give you an idea. My 6.3" Bison Set-Tru chucks use M18 set screws for adjustment & they weigh 21-25lbs. M18 is roughly .70" & they use M18 all the way up to their 25" chucks. The 6.0" Gator Tru-Adjust 3 jaw chuck I used to have weighed just under 20 lbs & it had M12 screws.

On my 5" D1-4 ER40 chuck that I made a Tap-Tru, I've never had it bump out of true having no adjustment set screws. IMO you can't really take heavy of enough cuts for just over 1" dia max to be able to knock it out of true. The mounting bolts on the face has plenty of enough holding power.

In case you don't know what I meant by Tap-Tru, the register on my adapter is slightly smaller than the ER40 platea. I just lightly snug the mounting bolts, tap the chuck true, then tighten up the mounting bolts. Plain & simple. Here's a pic I took of my ER40 plate when I finished mounting it. You can tell it doesn't weight much at all. And if you are making yours so the chuck sits inside the adapter, might want to add holes for a tommy bar. Comes in real handy if you don't have a spindle lock on your lathe. The style ER40 plate I got already had the 3 holes for the tommy bar. Lucky for me the size of the tommy bar fits perfectly on my super spacer as well so I only had to make one tommy bar.




 

mark_f

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#13
Yes




Most definitely! You don't want anything like a cup point digging into your backplate, if you do you'll risk raising a burr & not be able to remove the chuck from the adapter if the raised burr is larger than the mating clearance. The set screws aren't for holding, they're just for adjustment.

Normally the set screws are in the chuck & contact the adapter. I'm not sure how you are making your adjustable ER40, by the way you described, sounds like you are making it so the ER40 chuck fits inside the adapter & the set screws are on the adapter. No matter, same difference.




1/4" would be fine. ER40 collet chucks are very light. Even if you are converting one to an adjustable/Set-Tru type, I doubt it would weigh as much as an adjustable scroll chuck.

To give you an idea. My 6.3" Bison Set-Tru chucks use M18 set screws for adjustment & they weigh 21-25lbs. M18 is roughly .70" & they use M18 all the way up to their 25" chucks. The 6.0" Gator Tru-Adjust 3 jaw chuck I used to have weighed just under 20 lbs & it had M12 screws.

On my 5" D1-4 ER40 chuck that I made a Tap-Tru, I've never had it bump out of true having no adjustment set screws. IMO you can't really take heavy of enough cuts for just over 1" dia max to be able to knock it out of true. The mounting bolts on the face has plenty of enough holding power.

In case you don't know what I meant by Tap-Tru, the register on my adapter is slightly smaller than the ER40 platea. I just lightly snug the mounting bolts, tap the chuck true, then tighten up the mounting bolts. Plain & simple. Here's a pic I took of my ER40 plate when I finished mounting it. You can tell it doesn't weight much at all. And if you are making yours so the chuck sits inside the adapter, might want to add holes for a tommy bar. Comes in real handy if you don't have a spindle lock on your lathe. The style ER40 plate I got already had the 3 holes for the tommy bar. Lucky for me the size of the tommy bar fits perfectly on my super spacer as well so I only had to make one tommy bar.




Thank you. That is what I wanted to know. The flange on my ER 40 chuck is 3.950" diameter. The backplate (adapter) is 5" diameter. The chuck will set in a recess in the backplate. I have the chuck finished. I am going to make .020" clearance. .010" just seems like it may not be enough at times. My other collet chuck was dead on mounted on the lathe (where I made it) but was .003" out mounted on the dividing head.
20170910_122935_HDR.jpg 20170910_122946_HDR.jpg
 

expressline99

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#15
I made a chuck backing plate earlier this year and figured the "boss" would center it correctly. Having very little instruction other than make it fit the boss. It had lots of run out. Mind you the chuck I was making it for was 40+ years old. I came back and took the snug fit to having .005-.010 (as I recall) then was able to adjust it. Worked like a charm. These seem like really nice chucks. I really like that ER40 collet chuck!

Paul
 

4gsr

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#17
All of my Adjust A True chucks have a mild steel pad behind each set screw. They have a shoulder on them so you don't loose them when you remove the chuck from the adapter. I would advise against brass tipped set screws. The brass will eventually mushroom and cause problems removing the set screws in my opinion. Ken
 

benmychree

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#18
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.
I quite agree with your post; I have a 10" dia. Buck AdjustTru on my 19" lathe and have about that amount of adjustability, and at times it gets mostly used up, especially with soft jaws. There is simply no good reason to make the allowance small.
 

mikey

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#19
The little caps that go on the adjuster screws have a shoulder on them as Ken points out; they can only travel so far. It makes no sense (on an adjust-tru chuck) to make the snout of the back plate any smaller than the maximum travel of these caps. You can screw the adjusters all the way in and measure the gap to get an idea of what the travel may be but unless you're using soft jaws or a work piece that is way off, you are unlikely to ever use up that much travel.

For what it's worth, the caps in my chuck are hardened. Makes sense that they would be, as they will be under pressure when used to adjust the chuck while under slight tension from the locking screws. Brass may not be a good substitute for these caps.
 

benmychree

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#20
The little caps that go on the adjuster screws have a shoulder on them as Ken points out; they can only travel so far. It makes no sense (on an adjust-tru chuck) to make the snout of the back plate any smaller than the maximum travel of these caps. You can screw the adjusters all the way in and measure the gap to get an idea of what the travel may be but unless you're using soft jaws or a work piece that is way off, you are unlikely to ever use up that much travel.

For what it's worth, the caps in my chuck are hardened. Makes sense that they would be, as they will be under pressure when used to adjust the chuck while under slight tension from the locking screws. Brass may not be a good substitute for these caps.
The adjusting screws on my Buck Chuck are straight dog point setscrews, no limiting factor.
 

higgite

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#22
I made a chuck backing plate earlier this year and figured the "boss" would center it correctly. Having very little instruction other than make it fit the boss. It had lots of run out. Mind you the chuck I was making it for was 40+ years old. I came back and took the snug fit to having .005-.010 (as I recall) then was able to adjust it. Worked like a charm. These seem like really nice chucks. I really like that ER40 collet chuck!

Paul
Paul, I can relate. I'm in the same boat with my 5C chuck. Made the baseplate as close a fit as I could to the spindle register. No room to "tap-tru". So far I haven't needed tap-tru precision, but opening up the recess on the baseplate a few thou is on my to-do list. Glad you like your ER40 chuck.

Tom
 

mikey

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#23
The olde Tap-Tru technique! @darkzero coined the term as far as I know but I suspect hobby guys have been using this technique, either inadvertently or on purpose, for many years.
 

higgite

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#24
Yeah, I was calling it the "tap-tap" method and Darkzero came up with "Tap-Tru". Pure genius. I think I asked him if I could steal his term and he either said yes or no, I don't remember which. I've slept since then.

Tom
 

mikey

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#25
Yeah, I was calling it the "tap-tap" method and Darkzero came up with "Tap-Tru". Pure genius. I think I asked him if I could steal his term and he either said yes or no, I don't remember which. I've slept since then.

Tom
Tom, you crack me up! Your term is probably as accurate but Will's term has style!!!
 

darkzero

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Yeah, I was calling it the "tap-tap" method and Darkzero came up with "Tap-Tru". Pure genius. I think I asked him if I could steal his term and he either said yes or no, I don't remember which. I've slept since then.

Tom
Tom, I don't recall you or anyone else asking me for permission to use the name. It's just a name that I started calling a trick method that has probably been around forever. Of course I don't mind but I do appreciate the recognition! :)
 
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