How do you "true up" NEW, pointed, soft jaws to hold a small diameter?

After 20+ years of owning my own shop, I feel like a complete NooB asking this, but truly, I don't know.

How are you supposed to use (or true up) the points on a new set of steel soft jaws, for small diameter chucking?

1) My lathe chucks are Kitagawa B208 or B210's with 1.5mm x 60° serrations.
2) 90% of the soft jaws I purchase are 2 - 2.5" tall, flat ended, steel, offset, soft jaws.
3) We always chuck on something when we bore our jaws: jaw boring rings, jaw boring plates, cheek plates (in between the 120° mating surfaces of the 3 jaws, when closed) and slugs/ pins of material
4) Purchased jaws w/ pointed ends are not a good surface to chuck with, and need to be machined, to spin small diameter material concentric to the spindle.

Question:
How does one true up the points, say for holding Ø3/8" or Ø1/2" ??

Running a long endmill right down the center, does not yield a good gripping surface. It is also way too deep & too small of a diameter to follow with a boring bar. (the L/D ratio would be 7/1)

I can think of making a mill fixture to hold the jaws with the serrations, and then mill a radius (a flat, or the part shape) into the jaws,
OR
Dismounting the chuck from the lathe, and milling the jaws when installed on the lathe chuck. This approach seems like a LOT of unnecessary work.

So, what am I missing????

Thanks,

Doug.

I'm really interested in this too - wonder if drill under size, drill close to size, and then ream would produce a good result?

I too thought about following with a reamer, but the pilot hole would need to be perfectly straight.
A drill might want to walk, and the reamer will follow the pilot.
I figured an endmill would plunge straight, where the drill might wander......

Its not that hard.. I've held down to 3/32" in softjaws on an 8" chuck..
I pretty regularly grab 1/4, 3/8 and 1/2" in a 10 inch chuck in soft jaws.

Its itty bitty material, you don't need much force, and you don't need to grab
on a mile of it..

A list of stuff.

1) you don't need to be able to use BOTH screws in the jaws, you can easily use just one, with
the T-nut hanging out behind the soft jaw.

2) this lets you take beat up jaws and trim 'em down.

4) The "point" does not need to be 120 degrees included, It can be 90.. This
gives you a little more "wiggle room", where you aren't destroying things by
closing the jaws with nothing in them..

5) I've got a jaw I made years ago, that holds whatever in a mill vise at a 45 degree angle
Just slap the lathe jaws in, trim one side, and then the other and done. Nice centered point.
Do it to 3 jaws in a row, and you have a nice set...

6)You don't need the full 2" jaw depth, like I said earlier, take some oldies, and chop
'em down. to an inch or whatever thick.

7) on the really little stuff, get every thing all set with your machine so it will run with the jaws
flying (not clamping). Put your jaws on, and punch an endmill down the center. If they are oldies,
they are probably already thin (don't be afraid to mill your old jaws thinner).. If they are new ones,
don't be afraid to toss the jaws up on the mill and relieve the area behind the point so you only have
to bore an inch or whatever..

8) You mention taking the chuck off to mill your jaws... NO NEED to do that.. Had a job years
ago out of some 3" stuff.. The part JUST fit into the 3", but the part of the part that needed to
be turned was WAY off center..

My first thought was to turn a 3" diameter and then move 2 jaws in and one jaw out.. THAT didn't work..
So I drew it up, looking face on on the chuck.. Milled one jaw, rotate the cad model 120 milled the
second, rotate again, milled the 3rd.. Slapped the jaws up on the lathe, and it worked PERFECT..

9) Maritool (and everybody else) sells ER collet holders that are straight shank.. If I already have
3/4" or 1" jaws on the machine, and I don't have a TON of little D stuff to do, I'll just stick a
straight shank ER holder in the machine and run them that way.


I don't know if any of that helped... Many moons ago I worked with a guy that said he couldn't grab
less than 3/8 in the Mazak we had.. He was a good dude, he taught me a lot.. But after he left, I
made it a mission to figure out how to grab smaller stuff, and I did.. 3/32 copper, $14k a pound
parts..

Doug,
First, do you NEED the length of engagement, jaw to part to really be that long? I ask for a couple of reasons, in the past, I have relieved the middle, like the first 1/2" is "to size" the last half inch the same, and the middle plus .01.(don't care about size or finish in the middle) boring with a small "circle tools" bar is what I use. If you really don't need that much, the simple answer is use shorter jaws, you don't get as many face off in "Z" but who cares they have serrations, retip them, and move them in?
I am sure some one has a better answer but that's what I do. Well, DID before I invested in an ATS collet system. Best of luck
Chris

One way is bring jaws all together and drill a hole a 64th undersize. Another is bring jaws to size that will allow a boring bar thru and just touch the jaw tips. I've done both ways with reasonable success.

I don't.

Anything smaller than .5" diameter I use a Collet. We have a Collet chuck that can be switched out on the spindle for longer run parts. But I also have a small manual 5C closer that I have bored soft jaws for, for short run.

But if I needed to, I would bore them, then take them out and Machine the clearance. Like you said that is a lot of work.

R

Bore em. If there's to much chatter or you can't program the taper out, relieve the backside of the bore about 4xd.

If running a bar, we whip out plastic spacers for the spindle and lock em onto the stock with a set screw. Cheap and easy spindle liner when in a pinch.

I always had less than .0005 doing this holding 1/4 diameter and such..............my chuck was well maintained and in excellent shape.
I would take a new set of pointed jaws, set them at like 1.250 with my 1" boring bar, spin the chuck at 2000 rpm, skin the jaws then MDI the 1" bar to .250 and move them to the new position....boom, ready to run.

US Shop Tools has or used to have 5C bored jaws that would grip a 5C collet. I believe the collet was retained and the whole setup worked with the hydraulic chuck system. Not sure if you had to kiss cut the jaws to your chuck, but so what. You are a machinist.
I have bored jaws down to .375 with success but that was a long time ago. No idea how I did it and the result could have been schit luck.

2x hex 5C collet holders? One to run on, one to change the part out in? Just a thought...

Tonytn36 said:

2x hex 5C collet holders? One to run on, one to change the part out in? Just a thought...

Click to expand...

If you are going that route, go round.. 5C or R8.. And then you can use them in your turret to hold tools also..

Hex can be a bitch to hold in soft jaws.. Actually its easy.. I set my points pointing outwards. Turn 'em.
And then flip 'em back to the ID. Not bad if running single pieces, but a pain in the ass bar feeding.. Have
to get the jaws so that they won't open enough to let the hex spin.

I take all 3 jaws over to the manual mill and mill the point flat leaving about a 1/2 inch or so of the point. I install 2 of them on the chuck on rotate them to 4 and 8 o'clock. I place a short piece round stock on the flats and install the 3rd jaw. (It's now behind the points) Clamp on the round stock and bore. Open the chuck and blow the little piece of round out the back of the draw tube with the air gun.

Back in the late 70s when the shop I was working at got their first CNC, I made the equivalent of these...

Warner Swasey Style Collet Pad Top Jaws

We had several Warner & Swasey turret lathes and a couple hundred sets of the collet pads. Any size round, hex, square you could imagine we had pads for. Never messed with softjaws for small work.

2nd on the Warner Swasey top jaws I have that system and also a 5c "adapter". I think the WS are the 471 size and I have a s20 adapter to use them also.
The one thing about the 5c is careful about chuck pressure/preset of the collet adjustment.
Hydraulic chuck will collapse a 5c collet if pressure is to high/close without something in it

litlerob1 said:

I don't.

Anything smaller than .5" diameter I use a Collet. We have a Collet chuck that can be switched out on the spindle for longer run parts. But I also have a small manual 5C closer that I have bored soft jaws for, for short run.

But if I needed to, I would bore them, then take them out and Machine the clearance. Like you said that is a lot of work.

R

Click to expand...

Problem with collets is.. they want round, hex, or square stock ELSE one may even have to go off to an EDM shop. Valid option, that can be. Just not fast nor cheap.

Partial fix keeping one-each ER-40 and one-each 5C around that are on flat plates, never mounted to a backplate.

Put up in an ordinary 4-Jaw, so long as the stock shape fits, they can be dialed rather substantially off-center. From whence they will "repeat" just as nicely as collets can do to begin with.

Page two:

Enter the 2-jaw chuck. Also repeats well, but the work need not be centered, nor even regular in shape so long as its shape is consistent, complex curves included.

Replaceable STEEL 'soft' jaws can themselves be rapidly tooled to the next level with anything that serves. Adjustable kit mounted TO those can as easily be prepped on the mill, "dialed in" once attached to the "standard" top jaws, and not just on their tops, either.

Or prepped on the Panto Engraver, even, for truly odd shapes. Easier to store and far cheaper than the EDM not in my budget.

One of our PM members even made Torx screw heads that way, engraving machine sort of to reg'lar mills as a watchmaker's lathe is to bigger ones.

doug925 said:

After 20+ years of owning my own shop, I feel like a complete NooB asking this, but truly, I don't know.

How are you supposed to use (or true up) the points on a new set of steel soft jaws, for small diameter chucking?

1) My lathe chucks are Kitagawa B208 or B210's with 1.5mm x 60° serrations.
2) 90% of the soft jaws I purchase are 2 - 2.5" tall, flat ended, steel, offset, soft jaws.
3) We always chuck on something when we bore our jaws: jaw boring rings, jaw boring plates, cheek plates (in between the 120° mating surfaces of the 3 jaws, when closed) and slugs/ pins of material
4) Purchased jaws w/ pointed ends are not a good surface to chuck with, and need to be machined, to spin small diameter material concentric to the spindle.

Question:
How does one true up the points, say for holding Ø3/8" or Ø1/2" ??

Running a long endmill right down the center, does not yield a good gripping surface. It is also way too deep & too small of a diameter to follow with a boring bar. (the L/D ratio would be 7/1)

I can think of making a mill fixture to hold the jaws with the serrations, and then mill a radius (a flat, or the part shape) into the jaws,
OR
Dismounting the chuck from the lathe, and milling the jaws when installed on the lathe chuck. This approach seems like a LOT of unnecessary work.

So, what am I missing????

Thanks,

Doug.

Click to expand...

You might try going this route. I just make a split collet to fit soft jaws I've already got.

Brent

Vancbiker said:

Back in the late 70s when the shop I was working at got their first CNC, I made the equivalent of these...

Warner Swasey Style Collet Pad Top Jaws

We had several Warner & Swasey turret lathes and a couple hundred sets of the collet pads. Any size round, hex, square you could imagine we had pads for. Never messed with softjaws for small work.

Click to expand...

Good idea! LOL (I'm a little late though. I'm only 40 years behind you)

wheelieking71 said:

Good idea! LOL (I'm a little late though. I'm only 40 years behind you)

View attachment 220649

Click to expand...

I like the way you made yours so you can change the pads without taking the jaws off. The ones I made I have to take the darn jaws off. Live and learn I guess. Lol...

Brent

Here's my WS471 adapter

Pocket for shcs mount was reduced/lowered to allow removal of the pad screw without removing jaw
Pad screws are low height shcs




These are pics of the WS471 >S20 pad adapter.
Several sets of the S20 pads had already been modified for a special job on another machine so with modifying a set of the 471 pads they could be mounted without a new set of jaws. A little bit of Rube Goldburg but it works.