Collet adaptor sleeve?

[DianneB]

I have a 1944 South Bend 10L and the 3-jaw Cushman chuck is in poor shape. I am going to try to grind the jaws and overhaul the chuck to improve the accuracy so I put the dial indicator on the spindle and was amazed that my 0.001" dial showed NO deviations, internal, face, or internal! Amazing after 73 years!!!

The 10L has the proprietary South Bend taper in the spindle and I would like to make a sleeve to use 5C collets. I am confident in being able to turn the SB taper between centres accurately and assume I can drill or ream the internal for the 5C in the spindle very well but what I don't know is if the sleeve would need to be hardened to maintain its accuracy?

(I am retired and live on a meagre pension so cost is VERY important.)

Thoughts?

[pete]

Maybe 4140 pre hardened might work better for you. It's still machinable but a lot harder than mild steel and isn't that tough to find. With luck Rich Carlstedt will see your post and he'd for sure know the best material to use without extra heat treatment and with most heat treated tool steels you'd then have to finish grind to size. But if I remember the specifications for 5c I think it requires a minimum of an 1 3/8ths spindle through hole. Does your 10L have that? They do make proper 5c collet chucks that are much like a lathe chuck and even use a lathe chuck key to open and close the collets but there fairly expensive. They can be adapted just like any chuck to most lathes just by using a backplate. One thing to remember about 5c is the rear parrallel surface is extremely critical to help keep the collets alignment. You only have a 10th or 2 of being within specification or being out. I believe Hardinge has the full working drawings for the 5c on there website.

I've seen quite a few threads showing ER collet chucks made using mild steel and I've seen at least one thread where aluminum was used. Both I don't think using that is anywhere hard enough and I'm sure the collets seating surface would wear quite quickly so your question about using hardened material is a good one.

[Glenn Brooks]

I think it's fairly common knowledge that many if not most import collets are not hardened. Also There seems to be a lot of threads on various matching forums regarding mild steel shop made collets and arbors. So for home shop use, I bet you would do just fine without hardening the collet.

Probably more important than hardening, would be to choose a material that machines well and produces an excellent finish. This would help improve accuracy and reduce TIR.

Glenn

[DianneB]

.... it requires a minimum of an 1 3/8ths spindle through hole. Does your 10L have that?

Yes, it is a "heavy 10". The taper is 1.625 at the big end and 1.525 at the small end.

They do make proper 5c collet chucks that are much like a lathe chuck and even use a lathe chuck key to open and close the collets but there fairly expensive.

They are WAY out of my price range!

One thing to remember about 5c is the rear parrallel surface is extremely critical to help keep the collets alignment.

Are you referring to the 1.250" parallel 'shank' on the collet?

I've seen quite a few threads showing ER collet chucks made using mild steel......

I don't see any advantage to ER collets - they seem to be in the same price range as 5C. The ER does eliminate the long parallel bore in the holder but they are much shorter.

[jscarmozza]

Dianne, I found this information on the Logan Lathe site where Scott Logan was comparing the Logan lathe to SB. SB used a #3 Morse Taper or a proprietary taper that was the same angle as a #3 Morse. (0.60235 inches/foot). I have a D1-3 spindle on my SB and I made a collect sleeve for it many years ago that works fine with some oddball collets, smaller than 5C, that came with the lathe. I also made a 5C sleeve for my Logan, but I can only use collets with internal threads on that machine. I have a taper attachment on my SB which helps when doing work like this. After you turn and fit the spindle taper, do all of the internal machining in the spindle in one setup, you'll have a very useful tool. Good luck with your project, John

[Conrad_R_Hoffman]

Unless you're doing production work, I'd make it out of leaded steel or a modern equivalent. The most important thing is to get the final seat perfect. Put a center punch mark or a scribe line on the thing so you can insert it the same way every time and machine it in situ.

[pete]

OK your dimensions are ample for the 5c Dianne. What about the spindle through hole. You'd need some way of using a drawtube to open and close the collet itself. If your spindle bore is large enough for that you should be good. There's an Aussi guy on Youtube with a user name of Threadexpress who bought a Tormach RapidTurn for his CNC mill that uses 5c collets, the factory overground the collets rear bore in the spindle by a few 10ths too much. I learned a great deal about the 5c collets and how they locate with his videos about the problems it caused. Yep that 'shank' area you mentioned that's the ground parrallel section on the 5c collets just in front of the rear O.D. threads, and that's what keeps the collet dead straight and in your case it would be keeping the parts parrallel to the lathes ways. It's the straight section between those rear threads and the front taper. The front taper on the spindle or adapter helps locate and close the collet, but it's the rear bore that's highly critical for size as I said. It's what keeps the collet correctly aligned and straight with the spindle. Apparently they slightly overbore most of the length for a 5c and leave a fairly short undersize area at the rear and just in front of where the collets O.D. threads start that gets ground to a 10th or 2 larger than the collets O.D. for alignment purposes. The drawtube does help a bit with pulling the collet straight, but that bore and it's size is a lot more critical than I'd thought. Important enough that Tormach replaced his RapidTurn and I'd guess some changes were made at the factory since there were the same problems with a lot more than his. As long as your aware of it's importance then you can machine to suit the requirements.

Nope I didn't mean to use ER collets, I was using that as an example for people building collet chucks and the material some were using. 5c in my opinion is much superior to any ER collet. ER's only advantage is they use a lot less collets to hold a range of sizes. Afaik ER's aren't or weren't ever designed as a work holding collet. There made for tool holding. Likely it's only the HSM types that use them for work holding because of how slow they are to use that way.

[johnfreese]

I would go with 1144. It machines beautifully and has 100,000 psi tensile strength. You could go to ETD 150 (150,000 psi tensile) without sacrificing much machinability.

[DianneB]

What about the spindle through hole.

The through hole is about 1-1/4" - ample size.

I have one piece of 2-1/2" dia. x 2.5" of what looks like cold rolled in the shop cupboard - would be a pain to machine (because it is too short for a dog) but it's free

Also have some nice brass and bronze bar - they would be lovely to machine but probably too soft.

[Harold_V]

I would go with 1144. It machines beautifully and has 100,000 psi tensile strength. You could go to ETD 150 (150,000 psi tensile) without sacrificing much machinability.

You took the words right out of my mind (mouth). 1144, or Stressproof © would be an excellent choice, as it machines easily, with a nice finish, which isn't necessarily true of chrome moly. I'd be inclined to avoid leaded materials for an object that is intended for longtime use with a high degree of precision.

H

[John Hasler]

I have one piece of 2-1/2" dia. x 2.5" of what looks like cold rolled in the shop cupboard - would be a pain to machine (because it is too short for a dog) but it's free

Getting the accuracy and finish you need with cold-rolled will be a real pain, especially internally. Do a practice run with the cold-rolled and then buy a piece of Stressproof.

[Rich_Carlstedt]

I just saw Pete's comment and others as well. Yes, 1144 and Stress proof are excellent suggestions.
You do not have to heat treat or harden it Dianne
The primary reason for heat treating and hardening is longevity AND to prevent burrs/dings .
Nothing is more exasperating for accuracy than a dinged surface which thwarts all accurate machining done beforehand.
We all realize that when two metals collide, it is the softer one that receives the most damage ....and usually results in a burr or ding
The normal answer is to make it harder. This has the benefit of making a ding less likely and is nicer the grind and give longer life.
Since YOU will be handling the sleeve and will inspect it thoroughly before using it, and if you do so with care, hardening is not required.
I doubt you will ever wear it out !
Match marking a spot on the bushing and the spindle as was suggested is also a great way to maintain accurate placement on subsequent jobs

my Best
Rich