Author Topic: 12-sided ER Collet Blocks  (Read 832 times)

Offline JHovel

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12-sided ER Collet Blocks
« on: April 21, 2020, 05:20:26 AM »
Hi all,
a couple of years ago I needed to do some repetitive indexed grinding. Setting up the indexer or rotary table on the surface grinder just wasn't an option. So I looked for some Stevenson Blocks - invented by the late John Stevenson. At the time, freight and time was against me, so I decided to make a hex block myself.
In the process of working out how to go about it, the limitations of Stevenson blocks for my purpose became obvious. So I figured out a way to overcome them: I wanted to have the block itself bigger across the flats than the ER collet nut, so I could sit it flat on the magnetic chuck. Next I wasn't too sure about the repeatability of blocking it in on the surface chuck, since it would have to be resting against the corners of the hex block. So I decided to mill chamfers on all corners. Then a light went on in my head and I decided to make 12-sided blocks!
That not only overcame my concerns about blocking in on a magnetic chuck, but it also meant that holding the blocks in a vice on the mill or in the drill press vice would have it sit AND clamped on FLATS no matter the position!
I made two prototypes, ER32 and ER40 as accurately as I could.
They worked out so well, that I showed them to a tool manufacturer friend, Felix Mu, in Melbourne, Australia (near where I live) who agreed that this was better than was available.
Between us we figured out a way of making them available. He has a factory in China and agreed to be the sole distributor. He called the "Joe Blocks" which made me cringe, but that's his sales hat talking. Anyway, they are now commercially available, you only need one block not tow (like Stevenson blocks) to have a self-indexing tool fixture for 2, 3, 4, 6 and 12 position drilling, milling, engraving and grinding jobs.
Both ER32 and ER40 blocks are bored to hold the biggest non-standard collets available (which I purchased on Aliexpress) and work fine for me.

Oh, here are the links to my friend's shop for both blocks: http://www.mag-pro.com.au/goods.php?id=469 and http://www.mag-pro.com.au/goods.php?id=252
As an aside, I've bought quite a few tools from Felix, all have exceeded my expectations for accuracy. His factory in China works on western principles of quality control and produced noticeably more reliable products....

This sounds like a sales spiel, but I no longer get any benefits from the sales of these blocks, that's why I only mentioned these here now....
Cheers,
Joe
Cheers,
Joe

Offline Joules

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Re: 12-sided ER Collet Blocks
« Reply #1 on: April 21, 2020, 06:00:21 AM »
Brilliant Joe, I have just come across this problem on my hex ER32 block.  Just about to write up how I measured my little hex crankcase and found my collet block has 0.2mm variation on the edges.   No surface grinder here sadly to turn it into a 12 sided block.  I contemplated making a small 30 degree Vee block to mount under the hex block so it only contacts the surfaces.  Or at a real push just a piece of silver steel rod in contact with one of the bottom faces, so you are no longer referencing from an edge.  Thinking about it the Vee block would give you 12 positions if the block is used on the vice base and none adjustable jaw.
« Last Edit: April 21, 2020, 06:43:02 AM by Joules »
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Offline JHovel

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Re: 12-sided ER Collet Blocks
« Reply #2 on: April 23, 2020, 06:02:59 AM »
You are quite right about using a hex block for 12- sided indexing, but the centre height of every second position will be different :)

Cheers
Joe

Cheers,
Joe

Offline Joules

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Re: 12-sided ER Collet Blocks
« Reply #3 on: April 23, 2020, 11:21:20 AM »
LOL, doing it on the cheap always has its drawbacks.
Honour your mentors, and pay it forward.