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ER-32 Collet Blocks

B

Brian Ross

Active Member
This has been on my list of things to do for a long time. I saw a video of Stefan Gotteswinter where he showed what he had made. I like the design where the collet is closed using a rear nut that includes the collet taper. It is much more compact than the design that uses a front nut. This design allows the collet block to be entirely within the jaws of the vise. Here are a few photos:

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The blocks are nominally 2" square x 2.25" and are made of hot rolled. The nuts are better material but I'm not sure exactly what. A pretty simple project but a bit fiddly to get everything concentric and each side an equal distance from the centre line. After lots of small cuts they both end up being within 0.001" tir close in to the collet and about 0.003" tir 4 inches out.
 
No, you hold them in a vise on a mill. The square block allows you to hold a round part and quickly be able to index in 90 degree increments and the hex in 60 degree increments. Some uses would be adding wrench flats to a shaft, milling hex heads to round parts, drilling holes at 90 or 60 degrees into the periphery of a round part and I'm sure there are lots more. The holes in the nut for the tommy bar were indexed by using the square block.

They may not get used all the time but they are pretty handy for some things.
 
That is cool, never thought of clamping the ER-series from the rear. You're right, the nut isn't in the way then.
 
Brian,

These are an interesting design, @Brian Ross. Would be curious to know how they are working out for you. Would also be grateful if you could supply the link to the Stefan Gotteswinter video, as I cannot find it. Thanks.
 
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Great job @Brian Ross!I bought a hex block but I think a square one would have been a better choice. I’ve thought about making one but so far I haven’t been able to convince myself that I can get everything lined up and concentric
 
Don, the collet blocks work fine. I don't use them often but are pretty handy when needed. Stefan didn't make a video of this project, it was just a posting with some sketches on his website. I see that the project is no longer on his website. I did a search and did find a German version of the site though: https://gtwr.de/div/webold/german/projekte/pro_er25.html

You could probably get what you need from there. As for the construction, it is a bit fiddly but not really difficult. I just used regular mild steel (not hardened) so chips could get embedded if care isn't taken in cleaning chips out of the vise before tightening. I did all of the turning first and then put a pin in a collet and did a bunch of measuring to make sure that the sides were all parallel to and the same distance from the central axis. So, measure each side then take small cuts with a fly cutter and keep repeating until it is as good as you desire. I stopped when all sides were within a couple of thou. Not super precision but good enough for what I needed.
 
Thanks Brian.

I see that the drawings are for ER25, but I'm sure it won't be too much labour to upsize it to ER32. I'm thinking the greatest 'challenge' may be accurately translating the notes to English. o_O

Cheers!
 
Pardon my ignorance but I don't see the advantage of this over making a collet block that is larger than the nut diameter.
What am I missing?
 
David, you aren't really missing anything. With the tightening nut in the rear, the collet blocks are much more compact especially in the case of the hex block. I was able to make both the square and hex blocks from 2" x 2" material. In all of the commercially available ER-32 collet blocks I have seen the front closing nut is larger than the block itself which makes it less convenient to use on a mill table. Of course you can shim them up so the nut doesn't interfere with the table but for the ones I built you don't have to.
 
Brian Ross said:
David, you aren't really missing anything. With the tightening nut in the rear, the collet blocks are much more compact especially in the case of the hex block. I was able to make both the square and hex blocks from 2" x 2" material. In all of the commercially available ER-32 collet blocks I have seen the front closing nut is larger than the block itself which makes it less convenient to use on a mill table. Of course you can shim them up so the nut doesn't interfere with the table but for the ones I built you don't have to.
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Thanks Brian, to be fair I have only used my ER32 collet blocks in a horizontal position where the back of the nut indexes against the vise.
 
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