Need Advice About Lathe Collets

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divb

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I am new to the hobby and I recently purchased a Little Machine Shop HiTorque 8.5" x 20" Bench Lathe. It is their version of the Sieg SC4 lathe. I really like it and just purchased a set of 3MT Collets from them. These are great for working on shorter pieces of rod but they are not through hole and will only take work that is a couple of inches long.
I would like a set of through hole collets that would work with this lathe but I have no idea what to buy. Would someone be able to recommend or point me to a collet set that is through hole?
 
The spindle bore is 20mm. I looked at the bealtool link - Thanks. I'm somewhat confused about how a through hole collet is held. Mine use a draw bar but the problem is they are not through hole. How would a through hole collet be held. Do they use a tube to hold them in? Yours looks very nice and looks like it mounts to the face plate. This would be good but then I don't understand how it aligns to the spindle center line. I'm sure it is obvious to someone more experienced but I am rather new to this.
 
The Beall ER chuck screws on to the spindle nose so it is aligned with the spindle and does not need a drawbar. It is hollow so that anything that fits in the collet will will fit through the chuck. (ER32 maximum size is 20mm).
A D1-4 ER chuck like mine will attach to the spindle like any other chuck and not need a drawbar.
What kind of spindle nose do you have?
There are some pics in this thread:
http://www.hobby-machinist.com/threads/is-there-a-definitive-article-on-collets.36227/
 
Just looked at LMS's site and they offer two bolt on ER-40 chucks that fit a 4" spindle mount with three bolts. It looks like they might bolt right onto the spindle - might call and check if one will fit. The spindle bore is only 0.80" ID so even an ER-32 chuck would work, although the ER-40 has a 1/4" more capacity.
 
Hi divb,

I have an LMS 8.5x20 and an ER-32 chuck that looks just like the one that LMS sells.

To answer your question, ER collets fit into a collet nut that screws on to the nose of the ER chuck. The collet is hollow, tapered and split so that as the nut is tightened it forces the the collet back into the tapered nose of the chuck and compresses the collet down onto the work piece. Since it is hollow, you can mount work pieces that extend back into the spindle as long as the work piece has a smaller diameter than the spindle ID.

That said, I occasionally wish that I had bought an ER-40 chuck and collet set so I could at least turn short pieces up to 1” in diameter without changing chucks. Hope this helps.

Tom
 
Hi @divb,

It looks like you have some great guidance above.

I just stopped by to say Welcome to the Hobby-Machinist!

-brino
 
Thanks very much for the information. The LMS ER-40 4 inch diameter chuck will fit my lathe and is exactly what I was looking for. As Tom mentioned I would not be able to use the largest size collets as through hole but could hold shorter pieces of stock with them.
Thanks Brino for the welcome to Hobby-Machinist. The help and information has been exactly what I was looking for.
With my admittedly limited knowledge collets seem like a much more accurate way to hold round bar stock than a 3 jaw chuck and almost as easy to use (requiring at most a quick collet change). However on almost all of the youtube videos and blogs that I have seen 3 jaw chucks are used all the time and collets are very rarely if ever used. Am I missing something obvious?
 
The only 'obvious' thing is that collets have a very small workholding range outside of their intended clamping range (hope I said that right...) Collets are great for doing repetitive work on bar stock, whereas I am constantly needing to grab things of varying sizes one right after another. Which is why I use a high quality set-tru 3 jaw chuck which has very little TIR.

Different strokes, different folks. Same result. Oh, and welcome to the forums! :)
 
divb said:
However on almost all of the youtube videos and blogs that I have seen 3 jaw chucks are used all the time and collets are very rarely if ever used. Am I missing something obvious?
Click to expand...

In some limited situations, you just don't care about how concentric the turned end of the bar is to the piece that's in the chuck. Let me explain.......

Mostly that's when you are going to cut all new features on a part. You stick a blank rod in your 3-jaw chuck (that might have say 3 thou. run-out) then if you turn the entire outer surface of the part (even at different diameters) they will all be concentric with each other. After you part it off your work piece is round and all the new features you cut are concentric to each-other and your chuck runout has not mattered! The fact that you reshaped the entire outside of the part means the part has been re-centered about a new axis. That new axis may be 3 thou. away from the axis of the bar still left in the
chuck, but it doesn't matter.

You can even drill holes in the part using a drill bit in the tail-stock and those drilled holes will be concentric to the freshly turned circumference. That's because the the work piece (and chuck) are turning about the lathe spindle axis.

Note:
-in this case you may notice that your first cut is "interrupted" that you just skim one side of the work and the other side is uncut. At this point your work piece will not be round.
-your raw stock needs to start out bigger than the final part diameter plus the offset of the new axis.

However, if you need to re-mount something in your chuck for another operation, or need to create a new feature that has to be concentric with an existing one, then you need to centre that feature that was previously turned. You might not be able to do that to the accuracy required simply due to the chuck runout.

For re-chucking a workpiece you can try to minimize that affect by putting a mark on your work piece (a punch mark, or a sharpie line) inline with jaw #1 and put the work back in the chuck in the same position.

Of course, the ideal is to have a chuck with known low runout, so you don't have to worry about re-chucking a workpiece.

Another factor is cost.....a cheap 3-jaw chuck costs less than the collet adapter and all the collets you'd need to span a much smaller range.

-brino
 
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