Clearance on register of a set tru chuck?

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?
 
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.


img_9141-jpg.166335


img_9113-jpg.166334
 
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.


img_9141-jpg.166335


img_9113-jpg.166334
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.
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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
 
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
 
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.
 
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 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.
 
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