Collet Chuck information

[PeterT]

Doesn't work for Dusty's lathe, but looks like Precision Mathews sells an integrated D1-4 backplate / ER40 collet chuck on Ebay. And it has the equivalent of set-tru (adjustment screws) so can be dialed in independent of back plate adapter. (ebay item number 234016145577)

PM store home here
http://www.ebaystores.ca/Quality-Machine-Tools

 

[YYCHM]

That’s the 5C chuck that I have. Through some miracle I got it down to .0003 runout.

How did you mount it? You have a threaded spindled do you not?

 

[DavidR8]

How did you mount it? You have a threaded spindled do you not?

Yes, sorry I was not specific enough.
I have that chuck on a threaded backplate.

 

[DavidR8]

Duplicate post

 

[YYCHM]

WOW That's as big as your 3J. What is the max dia. it can handle?

 

[Johnwa]

John I bought one of these. After a bit of fiddling around the run out is about .001", but that's good enough for most 9f the work I do. Whe I complained that the runout was twice as much as his claimed .0006" or less he refunded half the purchase price. He also sells them with semi finished backplate for threaded spindles.

https://www.ebay.ca/itm/271667554173

That’s a very tempting price. The army manual shows the SM lathe coming with a spindle insert, MT5 to 5C with a draw tube. I’ve been watching for an MT5 sleeve to bore out but they are all a bit pricey for an impulse purchase.

 

[YotaBota]

Talk about timing, that's the ER40 collet chuck from Precision Matthews I'm looking at getting for my SM1120.

 

[DavidR8]

WOW That's as big as your 3J. What is the max dia. it can handle?

1-1/16” maximum diameter.

 

[Dusty]

As promised photos of my spindle face and 3J chuck registration. Closest measurement I can come up with on the registration inset is 0.9498mm diameter darn close to 95mm. Still trying to wok out the bolt pattern diameter, every time I do I get a different reading. Bolt diameter measures 7.78 mm. Any suggestions how to measure the bolt pattern diameter correctly?

 

[DPittman]

This might be helpful.

https://littlemachineshop.com/mobile/bolt_circle_dia.php

 

[YYCHM]

See circumradius https://www.calculator.net/triangle-calculator.html

 

[PeterT]

So the backplate boss lip engages the matching recess on chuck, then insert/fasten caps crews from behind & screw into chuck. Is that the drill?

Is there a chance that 95mm is your boss & 108mm is your bolt circle diameter? if so, might be a plug in for this LMS 5C collet (or clones like them) without any intermediary adapter. The recess depth is shown at 4mm so how does that compare to your plate/chuck? Your bolt is likely M8 & hole is nominal clearance so ~9mm diameter. That probably wont be a precision hole anyways.

https://littlemachineshop.com/images/gallery/drawings/3047ColletChuckFor5CCollets.pdf
https://littlemachineshop.com/products/product_view.php?ProductID=3047&category=

 

[PeterT]

Just as a quick check, if I assume the LMS referenced 108mm bolt circle diameter & your measured bolt OD, then you would get this kind of dimension (101.31mm) by calipering across the bolt OD tangent. May not be exact but close. Somewhere in your documents they should probably list or reference this stuff so you don't have to guess at it. I assume most of these machines will follow the same standard, whatever that standard is.

 

[Dusty]

Hey Peter, I shall answer your posts #52 & 53 here.

1. So the backplate boss lip engages the matching recess on chuck, then insert/fasten caps crews from behind & screw into chuck. Is that the drill?
1a. Yes that's the drill.

2. Is there a chance that 95mm is your boss & 108mm is your bolt circle diameter?
2a. Shall check that out tomorrow morning when I'm fresh and can steady myself on my good leg. Your word boss is throwing me off.
Believe what your speaking to is the protrusion on the face of my spindle plate that marries with the recess in the chuck. So the boss
sticks out 3mm.

Note: I'm using a really a nice Mitutoyo 9" OAL caliper but there's times I struggle using it like now.

3. The recess depth is shown at 4mm so how does that compare to your plate/chuck?
3a. Recess depth on my 3J chuck is 5.20mm

4. Your bolt is likely M8 & hole is nominal clearance so ~9mm diameter.
4a. Would agree with you on that.

5. Just as a quick check, if I assume the LMS referenced 108mm bolt circle diameter & your measured bolt OD, then you would get this kind of dimension (101.31mm) by calipering across the bolt OD tangent. May not be exact but close. Somewhere in your documents they should probably list or reference this stuff so you don't have to guess at it. I assume most of these machines will follow the same
standard, whatever that standard is.

5a. Unfortunately my Craftex manual provides no mention of design measurements for my 3 & 4 jaw chucks. Sorry!
I shall measure things up tomorrow and get back to you. Darn weather swings is playing havoc with my right leg/knee and giving me
much trouble so be patient. Hopefully the above answers help!

 

[Dusty]

See circumradius https://www.calculator.net/triangle-calculator.html

Thank you Albert Einestein, did I tell you I failed math miserably! LOL

 

[PeterT]

Your word boss is throwing me off. Believe what your speaking to is the protrusion on the face of my spindle plate that marries with the recess in the chuck. So the boss sticks out 3mm.
Sure, protrusion, projection... works for me. Someone once told me that 'boss' normally refers to (only) circular sections so I might get part marks on this one! LOL

Take care of yourself & we'll pick up again when you have more data. this might not be as complicated after all if the parts fit. The only thing with this kind of backplate arrangement is concentricity is pretty much locked into the chuck itself. ie. if the rear face recess or collet nose is not concentric to your backplate PROTRUSION, there is no real means to adjust runout without more serious mods. No different than other direct mounts but people kind of lump 'accuracy' into one bucket.

 

[combustable herbage]

I have the same lathe and I am measuring in the 95mm range from the centers of the holes and in the 108-110 range for the bolt od tangent, I don't have mine off I just took measurements with a ruler from the back should be with in a few mm.

 

[Dusty]

Just as a quick check, if I assume the LMS referenced 108mm bolt circle diameter & your measured bolt OD, then you would get this kind of dimension (101.31mm) by calipering across the bolt OD tangent. May not be exact but close. Somewhere in your documents they should probably list or reference this stuff so you don't have to guess at it. I assume most of these machines will follow the same standard, whatever that standard is.

@PeterT, a new day and I'm just in from measuring in our attached garage. Of course I understand your reference to boss although not the term we used during my air force days. Can't remember what term was used from our technical aircraft orders although specific to aeronautical terms.

Using my inside and outside spring dividers to measure the registration the boss diameter is 95 mm as well as the inset on my chuck give or take a mm. Boss is 3mm thick and the chuck registration inset a hair over 5mm. Bolt OD tangent is within a whisker of 101.31 mm. With my 8mm cap screws being so short in length 15.40mm and with thread wiggle my reading between the three are 1.145mm, 1.139mm, and 1.124mm. Close enough me thinks, what say you to this?

The clearance between the rear of my spindle face plate and head stock is only 2.0mm so the 23.85mm OAL of my 8mm cap screws barely squeeze in.

Thanks to @combustable herbage for his input for his Craftex chuck measurements. Yesterday wasn't a good day for me getting around, I have far too many days like that.

 

[YYCHM]

Looks to me you have a standard 5" chuck so there should be lots of options out there.

 

[Mcgyver]

Thanks shall double check to see if I can locate a #4 MT holder for 5C collets.

probably late to the party here, but a 5C collet won't fit in a 4MT spindle taper . Quite a few manufacturers offered a 4 1/2 MT taper which was a good arrangement - it created a taper just large enough to fit a 5C collet. I had a standard modern like that, wonderful set up....miss that lathe.

On one hand an adapter mounted chuck in the spindle is ideal, on the other hand staying with 5C collets makes a lot of sense as they are so common and have a decent capacity. To stay with a 5C you'll need a collect chuck (vs adapter and drawbar) that mounts to the spindle - is it cam lock?

The big name in the chucks Sjogren which even used trade at quite premium over the low cost ones, but are worth it imo. I held out and eventually got used D1-3 and D16 chucks with hardinge 5C and 2J collets. As I say they are a premium but will hold their value and offer the best performance.

The ER collet was originally used for for tooling while split chucks are for work. there's huge overlap and many use ER's for work and build wonderful things, but if have a choice, I prefer split chucks for work holding. The main reason is an ER chuck needs to grip over its length where as a split can hold short pieces.