Holding short lengths

I just realised why he offers the 42 size Raymond - the diameter of the draw bar adapter. They mention a master collet. I suspect that takes the spring collets and brings the holding capacity with that down to 25mm. It's 42mm in bar chuck mode.

Unlike some I wasn't trying to push you in any direction. Just thought that they might be of interest. The above would cause me to rule them out though. A separate bar chuck could have a larger capacity.

John

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No problem John, I appreciate everyones advise. Just discovered [ I think ] why the quote is not through yet. Bt e -mail has been having big probs these last few days, ie logging in and mail going into "cyberspace " so will fire one off using me G -Mail add. see if that brings any action.

cheers.

Raymond - I would suggest you think about taking your own advice. After your thread on ER collet issues, JS started this separate thread to discuss methods of holding short length workpieces. This thread is not about what you have decided to do....

Dave Martin

Dave, JS started this thread in response to me saying what MY gripes are with the ER collets when holding short length parts.

JS knows my decision, so should not need to drag up the soft jaws again and again. [ alluding to ME ] get that through your head. if you can.

You would be better to retitle the thread to " John Stevenson's pop up soft jaws " on account of the times they have " popped up " Since when have fellow members been restricted to a certain size of lathe ? Maybe this forum should state "Owners of lathes above a certain size are not allowed to join". Even better, make it clear that any owner of a lathe that has a larger spindle bore than 38mm is not eligible join. I might be banned for the DSG but would still be allowed to join on account of me GH750 only having the 38 mm spindle bore.

Im sure that i'm not the only "hobbyist that has a " biggish " lathe. I'm sure there are some who have a lathe such as Colchester Triumph or maybe even a Master, and yes maybe even some with a DSG so what !!

They could fit suitable sized spring collets on just about any lathe and Raymond is correct in that sense as they are designed to hold a minimum length. At $200 a piece from what I can see I doubt if many on here would be interested in this particular size and in my case I am happy with what I have even given it's length limitations - rubber collets. More happy than I would be with multi sized bar chuck collets as they do offer shorter grip lengths.

I do have a range of boxford collets - it skips sizes. There are 9 collets in the rack that will hold something like twice that number for a full set. Jason sounds like he needs bigger so probably bought a spring collet chuck. There are lots of options and differing on cost.

Personally I feel people wont have problems with ER providing they grip 1/2 of the collet length - 2 diameters or more as well. Can't prove that but on the face of it they could grip any length as well as any other so why is the length aspect mentioned? Very probably because nothing is exact. Makes sense to me anyway which is why I bought good quality ER16 first. They do for most of my milling too. For lathe work I feel that they will be fine down to 1/2" length. Very probably shorter if they and the holder are precisely made.

Looking at my ER25's they do have reduced grip length up to the 10-11mm but not much at that size, hardly any at all. The smallest size only grips as far back as the recess in the outer body so circa 1/4". The ER16 are relieved at the back in the same way as well. What it boils down to is that up to a certain size the grip length will be something over 2D maybe 3 but not the full length of the collet than at some size it will be the full length of the collet.

Sticking a slug in the back unless it's the exact size doesn't make any sense at all. I'd wonder about rubber bungs even in a rubber flex holder.

If some one is stuck with 3C collets and wants to do a Jason the step types can be bought up to at least 3" dia. Buying them in the UK could be a bit of a problem.

Want 5C but don't want to buy a chuck - make one - draw bar based to simplify it. I think those go up to 6".

Soft jaws are the easiest cheap answer to larger diameter thin things providing that they are stiff enough to go into a 3 jaw.

Raymond may be spending a lot but it might be worth bearing in mind that equipping a lathe is generally reckoned to double it's cost and including a full set of collets for a lathe the size of a DSG might even exceed that. Adding to the lathes co uk info on them they also had an automatic screw cutting drop out and could also have electronic power traverse to move the saddle about. I got fed up with being asked to show visitors that. I always used the wheel. I also don't think that they are entirely correct on the max bed lengths of the T.

John

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I don't think anybody even Raymond has anything against soft jaws John.

My only beef about them is hand fitting the jaws. Hence my interest in the ones where the top of the jaws are on carriers. It's a pity Burnerd don't do them. The other makes to me seem to be rather coarsely built bit I've never broke one. I have broke the end of several chuck keys - ever since they started welding on the ends.

Probably wouldn't like the cost if they did make one.

John

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Edited By Ajohnw on 06/10/2016 17:57:59

I'm not sure we're on the same page here, John. My soft jaws doesn't like holding stock for too long.

He prefers the long lengths over short; make for a bigger meal he says. 

Michael W

Edited By Michael Walters on 06/10/2016 18:05:31

He'd probably be happy with the usual 2D rule but would need to eat lots and do it the right way.

John

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Ok, had a few PM's and emails asking for details on the soft jaws I mentioned.

First off DON'T use the type of soft jaws Michael has illustrated above. For one they are too soft, not concentric, and don't support at the back end but then again anyone who actually used a lathe would know this.

Ajohnw also made a good point about the fit of soft jaws needing work to make fit. I personally can't comment on this as every set I have bought has fitted perfectly but I used to use a guy out at Mansfield, Oxton to be precise who did nothing but make soft jaws for industry. No idea if he's still trading but he turned out really nice work.

First shot to show the concept.

Just a standard set of soft jaws with a tenon machined on the top face and three tapped holes in each jaw with a small counterbore.

Onto these are fitted three pieces of hex bar with three slot in the back to locate onto the tenons and a counterbored hole for an allen screw and a small dowel on the back for repeatability.

Another shot.

better to show the jaw without the hex fitted and the rear of the hexagon.

You then load the jaws in the right direction by fitting a bung onto the ends of the original soft jaws and machining the hex out.

The one on the top of the chuck shows where it's been machined to hold a series of 5mm pins for a second operation. The other positions have been bored for other jobs, sometimes each position has been used 3 times.

I have about 5 sets of these hexagons lettered A to E ? and each jaw is numbered and the position is also numbered and a small notebook list the hole position in the soft jaw and the hex position for each special job so I can quickly go back.

The original soft jaws are never touched after the tenons and holes are drill so they will last the chucks lifetime.

The Hex bits are easily replaced when worn out but to be honest I am only using the A and B sets and have had no need to break out the other sets. The Hex bits were made of mild steel found in the local steel suppliers offcuts bin and cost peanuts.

Depending on which set of holes you choose you can go from the 5mm pin as an example to as big as the chuck can handle.

This being a 7" washer I fitted just for the photo shot but at 6mm thick it's an easy job to face up both sides and the bore.

I hope this is of interest to users.

Yeah, i thought i'd lighten the mood a little, earlier on.

On the real soft jaws, i take it these need machining to get the extension lugs on there.

Trouble is, i have a 100mm recess chuck that came with my lathe, and no provision for buying soft jaws directly, does anyone know how i can measure these,so that i could buy some or possibly make my own?

Could you copy the shape of the original (scroll) on a pentograph for example?

Michael W

Edited By Michael Walters on 07/10/2016 13:44:07

Try Rotagrip they do various softjaws for some of the imported chucks, I got a set from them for the chuck that originally came with my WM280. Its fairly obvious from looking at the sizes available what you need to measure.

To get them to look like Johns you will need to mill down each side to form the tennon and then do the holes, easy enough as they are just unhardened steel. Does not even have to be spot on for the hole locations as you will be machining the hex jaws in situe.

The other option which saves having to mill the jaws is to make the slots in the hex bits the width of the jaw so they just slip over them.

I think Harold Hall's site shows how to machine the teeth if you want to make your own jaws.

Edited By JasonB on 07/10/2016 14:27:19

I get mine from Rotagrip and have to do a bit of hand fitting to get them to fit my Burnerds. I've done it several times on different chucks and have had to fit them. I suspect they come like this to account for chuck wear. Mine are more or less as new.

It's not hard. I hold the jaw by hand on a table and feel the file onto the surface to keep it square. I just use the usual warding file set and may even hold the jaw in my hand and move it on the file. Usually the slot to take the face of the jaw needs work and the depth of the slot. Done slowly it's easy and I leave them a very firm hand push fit into the slots and the use the chuck key to check the fit fully in. Each end can be checked by pushing it into the chuck. Only thou's need removing.

I think the type of chuck I linked to does it by having a slot along the jaws and another across. That way the jaws always go back on in the same position so hard jaws can be exchanged or turned round as well. I have seen mention of large Chinese chucks made this way.

Last time I did some I found the reversed jaws not long afterwards.

John

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Michael, These are ones I made in the more conventional style. If your chuck has 2 piece jaws the master jaw is the one that engages with the scroll,and you only need to make the top set. These ones are from 7075 Aluminium. I have steel ones also for the 150mm and the 315mm chucks. It is important to always use the steel tenon [ if it is 2 piece jaws ]. Close up of the tenon below.

Thats the best soft jaws iv'e seen today.

 There is a lad called Steffan Gottiswinter [or something like that ] has a channel on you tube, and he has one piece jaws, so makes soft jaws in one piece using a pantograph for milling the scroll. cracking job he makes.

Edited By Raymond Anderson on 07/10/2016 16:53:01