Stevenson Blocks...

Understood, John

That said: What I may do, in my forthcoming idle-moments, is see if I can design a little adapter to take watchmaker-style split collets ... with a slimline substitute for the ER nut.

I currently have 6mm, 8mm &10mm bodied collets available [plus, of course the 11mm BCA ones], so should be able to work something out. ... All I really want the 'Stevenson' blocks for is their concentricity.

MichaelG.

The general relativity field equation:

is possibly more apposite to rocket travel, if not rocket science.

Andrew

Michael could you not accurately bore a bit of square and hex stock to take a parallel shank ER20 Holder, could even size the block to clear the nut. Put a flat on teh parallel shank and use a grubscrew to retain it which will allow it to be taken out for other uses.

Must admit that since I got theStevenson 5C spin indexer I use that to put squares and hexes on things as its quicker and more accurate than blocks.

I use 5C blocks for the hex and square operations. I stay with 5C due to having a full set of collets off my old South Bend lathe. I may start to look into ER stuff soon now the price is right due to popularity.

.

Jason,

I was rather hoping that 'Stevenson's accurately ground blocks' would be closer tolerance than 'a bit of square and hex stock'.

MichaelG.

Nothing to stop you skimming the stock to a better size/finish/accuracy

Another option is to hold the parallel shank ER20 in an ER32 block and buy just one suitable ER32 collet.

Edited By JasonB on 07/01/2016 17:18:29

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Jason,

I was rather hoping that 'Stevenson's accurately ground blocks' would be closer tolerance than that too !!

Let's just forget it.

MichaelG.

Is there any reason (apart from the obvious one of extra expense on materials) why they can't be made double-ended? That is to say, have an ER20 on one end paired with an ER25 on the other end. Likewise ER32/ER40. That way you would only need two blocks to cover quite a range. Of course, you wouldn't sell so many. I think I've found the reason!

John

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It might be tricky to stand them vertically.

MichaelG.

Not if it was clamped to an angle plate and cylindrical square combination, though I'm struggling to think of an operation that would need it to be mounted in such a way, that couldn't be acheived horizontally or with a rotary table. Doubtless someone will come up with several!

John

Give over John, I have to think of the Royalties and me 4 quid.

Oh and the two quid that Steven at Ausee owes.

Her you go John H

Milling the slot in the underside of a piston and then laying teh block on it's side to drill & ream the Gudgeon pin at 90degrees. Yes it can be done in a rotary table but you need to remount and clock teh table and have a 3-jaw to fit the table. This way you only need to centre it once and the vice fixed jaw does not move so no need to ctr again. ER being smaller also allows you to get in closer with a small piston where the 3-jaw may get in teh way

Edited By JasonB on 08/01/2016 16:54:10

Jason

I'm curious as to why a spin indexer is more accurate than JS collet blocks?

Having said that your piston is done by the block method.

Ian P

Ian I tend to work small parts on the end of a bar so can often have 18" or so of bar sticking out the end of a block if say machining a square on the end. Each time the block is reset in the vice for the next face you have to ensure it is up tight against a vice stop and knocked down firm which is not easy with a long length of bar making the block unbalanced. With the indexer all I do is undo spindle lock, index to next position, lock spindle , cut and repeat. Its not that the blocks are inaccurate but that you have to spend time making sure you accurately reposition them.

Piston can't be done in a Stevo indexer as they don't stand on end for the first op.

One other thing is what do you do if you are holding say a 10mm dia part in your ER block and want to hold a 10mm cutter in your ER collet chuck to machine it? Not a problem if holding work in a 5C collet

J

Edited By JasonB on 08/01/2016 17:21:48

Fully understand all that, so it all makes sense now, thanks

Ian P

One other thing that you can't do with an ER block that you can with an indexer

I'm not running the ER blocks down, its just that all tools have their uses and some suit a particular job more than others and I managed OK with the blocks before I got the indexer. Also just got a set of 5C blocks from Santa.