3J chuck soft jaws (Bison)

[PeterT]

I thought I understood the machinable soft jaw concept but maybe not.

See sketch, can I use these as a jaw 'base'? ie drill/tap & attach sacrificial machinable plates kind of like like red sketch? Or maybe they are hardened & intended for some another purpose? Note they have scroll grooves on underside like regular jaws.

AJAX Soft Blank Jaws for Bison Scroll Chuck 6in 3 Piece Set Soft Blank Solid Jaws for Bison Scroll Chuck 6in 3 Piece Set

These have an index step, no scroll thread. Presumably to engage do these go into a special kind of jaw?

6" CAS6 Bison tongue & groove Chuck Jaws 6MSH DM201477

General soft jaw links

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[PeterT]

maybe partially answering one of my own questions, I think these are intended to go together?

 

[Susquatch]

can I use these as a jaw 'base'? ie drill/tap & attach sacrificial machinable plates kind of like like red sketch? Or maybe they are hardened & intended for some another purpose?

I think they are soft and meant to be machined as is. Maybe turned in place.

Adding a second layer as you propose would work but would add a cantilever load which might not be a good idea with soft jaws.

In general, I like the idea of a lower profile hardened scroll jaw that you add another soft block to. That's prolly what you were thinking of too.

Perhaps the parts you show are actually two parts?

 

[eotrfish]

AJAX Soft Blank Jaws for Bison Scroll Chuck 6in

The description in your first link says it all - SOFT blank jaws. They are complete jaws. You should be able to drill, tap and mount your sacrifial machineable plates.

I think these are intended to go together

Bingo. The second link is for replaceable top jaws. I have a set of Aluminum top jaws that I machined to accept fly reel spools and set of soft steel top jaws as well. Both are easy to machine to required profiles.

The Aluminum top jaws have been removed / reattached many times and are repeatable within .0005" runout. The key to repeatable runout is the precision of the locating step on the mating surfaces.

 

[PeterT]

Thanks @eotrfish . Maybe I should have qualified. My chuck has reversible jaws. Been a while since I had them off but I'm guessing once removed, the exposed sub-jaw would match the underside slot profile like soft jaw on right? For some reason I didn't see any aluminum soft jaws on Ajax for 6" & they are spendy.

ALUMINUM TONGUE & GROOVE JAWS

so thats what made me consider post-1 pic. Un-scroll the existing jaws out altogether, set them aside, no need to disassemble. Use the pre-scroll-threaded machinable ones to accept sacrificial aluminum 'plate' pseudo soft jaws. Mitigates using spacers & making dedicated shallow depth pot chucks, CA glue etc. for facing thin stock discs accurately & repeatable. Do you have any pics of your setups?

jaw detail

TMX Hard Top Jaws for 6" Scroll Chuck, 3pc, 3-883-306P

TMX Hard Top Jaws for 6" 3 Jaw Scroll Chuck, 3 Piece Set, 3-883-306P

www.smalltools.com

 

[eotrfish]

Peter

Since you already have reverible top jaws you could just make sacrificial top jaws with a profile that matches the profile of the master jaws. Bolt them onto the master jaws and away you go. The bolts are 3/8-NC socket head caps. If you don't need to countersink the heads you can probably get away with 3/8" plate (plus the tongue height C minus F in your drawing) With a little precision milling you could make up a bunch of sacrifial top jaws in short order. With precise dimensions on the tongue and groove and marking the top jaws 1,2,3 you should be able to hold .001 TIR when remounting them.

I don't recall where I purchased the top jaws but I'm sure they were a lot cheaper that what KBC is showing on their website. Possibly got them from MSC. They are H&R brand. It's worth a look at the MSC website because they have some other cool full circle top jaws that will work as shallow pot chucks.

I set up all 3 jaws and milled the slot in order to accomodate the back flange of the reel spools. Then mounted them, clamped the master jaws onto a setting ring and turned the front ID to match the largest spool arbor that I planned to make.

Here's a spool mounted in the jaws

The jaws empty

 

[Susquatch]

Since you already have reverible top jaws you could just make sacrificial top jaws with a profile that matches the profile of the master jaws. Bolt them onto the master jaws and away you go. The bolts are 3/8-NC socket head caps.

Mine are the same way with a top and bottom half indexed very tightly with two square sections on each jaw.

I made some pillars that fit on the 3/8 caps and installed longer caps such that the pillars act as quasi soft jaws. Since there are two screws per jaw, you can achieve a wide variety of sizes this way without having to make or buy actual soft jaws. I've also used them a time or two to make plate jaws like the ones @PeterT shows in his last photo above. To achieve low runout, I put a piece of 4" ABS Pipe in the outer screw pillar system I described above to hold the Jaws apart while I machine them to the desired diameter. Usually the pillars can stay there for the subsequent machining operation.

Both of you guys discuss soft jaws as though there is some kind of precision standard on the dimensions of soft jaws. If there is, I didn't know it. This raises some opportunities for me. Are these standards a bit like chuck mounting standards - ie any D1-5 chuck will fit my lathe spindle? In other words, can I buy a set of soft jaws and know that they will fit the bottom half of my jaws? Or is it chuck brand specific? If so, I'll have to make them because my 3-jaw chuck is no name brand.

 

[PeterT]

Both of you guys discuss soft jaws as though there is some kind of precision standard on the dimensions of soft jaws. If there is, I didn't know it.

Soft jaws are quite accurate to the extent they are cut in-situ to the rotational axis of the machine. So even if your normal 3J has some runout, that is negated once the sacrificial soft jaw ID is cut. They also provide a means to cut specific shapes to fit hard to grip objects with a known depth datum etc. Thin, fiddly washer type parts is one example, but there are many other parts that fall in this category.

For smaller parts you can get 5C (collet based) soft jaws aka emergency collets. They come with insert pins to keep the jaws apart/loaded, you make the relief profile, then they are ready to load 1000 parts to that specific shape. But these are spendy & don't work for larger diameters. BTW some guys 3d print their own 5C emergency collets complete with threads & apparently they work not bad with light load.

Back to 3J, once cut, practically they have +/- grip tolerance. If you turn a 1.000" ID relief and insert a 0.999" part, it will feel nice & secure ready for turning. In reality the contact is focused on the OD/ID tangent points depending on their relative diameters. And a 1.001" OD part in 1.000" ID relief also 'fits' but now contact is concentrated on the corners of the soft jaw ear. Its actually not much different to how a regular jaws contact our work but we don't really stop to think about it. I suspect most of the 3J grip is provided by distortion and/or low depth 'bite'. Anyways for my application its holding lightly loaded fiddly parts.

Clickspring & others use a simple method of facing a sacrificial bar end (sometimes its also grooved) & glue the part on with CA 'instant' glue, then do the machining. To remove part, either apply heat or soak in solvent. It works & I do this for quick onsey-twosey's, but it becomes tedious with multiple identical parts. And even so you can have parts come off if the cutting load is much more than delicate, Its better to turn a relief in the bar end so the part is constrained (put chuck principle). But now when you remove the assembly to cook/soak you need to repeat the toolmaking from the beginning.

example dedicated 1-off 'glue chuck' for a gear

 

[Susquatch]

Soft jaws are quite accurate to the extent they are cut in-situ to the rotational axis of the machine. So even if your normal 3J has some runout, that is negated once the sacrificial soft jaw ID is cut. They also provide a means to cut specific shapes to fit hard to grip objects with a known depth datum etc. Thin, fiddly washer type parts is one example, but there are many other parts that fall in this category.

Sorry @PeterT & @eotrfish , when I mentioned the precision you guys were talking about, I was strictly asking about the way the soft jaws attached to the double rectangular attaching system. I have never used this capability even though my jaws have this feature.

More specifically, I was wondering if that rectangular registering system was a standard of some kind that applied to any chuck jaws that had the rectangular index.

It's this registering system in the photo below (copy of your photos) that I am curious about at this time. Nothing more, nothing less.

My no-name brand jaws have this system, but I've never used it other than to reverse my jaws.

Instead I have used other approaches that I made the mistake of discussing - mostly for your benefit. I should not have done that because my question got lost in the confusion. Sorry about that.

 

[PeterT]

I don't recall where I purchased the top jaws but I'm sure they were a lot cheaper that what KBC is showing on their website. Possibly got them from MSC. They are H&R brand. It's worth a look at the MSC website because they have some other cool full circle top jaws that will work as shallow pot chucks.

Yes, the prices are getting nutty. I think its worth me milling some top jaws from scratch since I'm proposing to modify them anyways. Seems like their dimensions have been standardized for a long time. And thinking back, that's one of the reasons I got this style of chuck to begin with.

 

[PeterT]

More specifically, I was wondering if that rectangular registering system was a standard of some kind that applied to any chuck jaws that had the rectangular index.
It's this registering system in the photo below (copy of your photos) that I am curious about at this time. Nothing more, nothing less.

That I don't know. The references & PN's I've shown are specific to Bison (my chuck). They vary by chuck model within same manufacturer. Gator apparently cloned Bison dimensions so presumably would be the same. I've heard some Chinese chucks have 'the same' nominal dimensions but actually don't fit well, so does that mean close-to or QC issues? I recall discussion about differences between Pratt Burnerd chuck & others of same size. The scroll was different, so maybe they have their own jaw standards & therefore you need to stay within their eco-system. I guess removing your jaws measuring might be the quickest way to answer.

 

[thestelster]

Mine are the same way with a top and bottom half indexed very tightly with two square sections on each jaw.

I made some pillars that fit on the 3/8 caps and installed longer caps such that the pillars act as quasi soft jaws. Since there are two screws per jaw, you can achieve a wide variety of sizes this way without having to make or buy actual soft jaws. I've also used them a time or two to make plate jaws like the ones @PeterT shows in his last photo above. To achieve low runout, I put a piece of 4" ABS Pipe in the outer screw pillar system I described above to hold the Jaws apart while I machine them to the desired diameter. Usually the pillars can stay there for the subsequent machining operation.

Both of you guys discuss soft jaws as though there is some kind of precision standard on the dimensions of soft jaws. If there is, I didn't know it. This raises some opportunities for me. Are these standards a bit like chuck mounting standards - ie any D1-5 chuck will fit my lathe spindle? In other words, can I buy a set of soft jaws and know that they will fit the bottom half of my jaws? Or is it chuck brand specific? If so, I'll have to make them because my 3-jaw chuck is no name brand.

There is the, American Standard Tongue and Groove, dimensions which Bison, Buck, BTC, Cushman, TMX, PBA, Yuasa & Rohm Chucks, utilize in their designs. There is a medium duty and heavy duty dimensions.

 

[Susquatch]

I guess removing your jaws measuring might be the quickest way to answer.

OK. I'll do that. Hopefully they are the same. One thing is for sure. I won't find off-the-shelf jaws if they are different.

My 5C chuck is a Bison. The others are either ones I made myself or the two (3 & 4 jaw) that came with my lathe. The Bison is a piece of art.

That said, as cheepo as my three jaw is, it's actually about as good as one could ever hope for. I had always planned to grind the Jaws but then I measured them and realized I had been waaaay too pessimistic! A good mistake to make I guess.

There is the, American Standard Tongue and Groove, dimensions which Bison, Buck, BTC, Cushman, TMX, PBA, Yuasa & Rohm Chucks, utilize in their designs. There is a medium duty and heavy duty dimensions.

There is also........
.......
.......
HOPE!

 

[PeterT]

Of course.. now that my Shars order just landed, I notice these at significantly lower cost (USD)

6" x 1.259" HT American Standard Tongue & Groove Soft Steel Chuck Jaw Set

www.shars.com

Apparently jaws are quite common in different heights, materials, centered, offset (USD)

Soft Jaws - Flat End - American Standard Tongue & Groove

The American standard tongue and groove flat soft jaws you get from us can be used for Bison, Buck, BTC, Cushman, TMX, PBA, Yuasa & Rohm, and other chucks.

eagletoolandsupply.com

Oh well. I intend to make some anyways for the heck of it. My home shop rate is cheap & aluminum isn't very expensive

 

[Susquatch]

Thanks for the reminder @PeterT . I meant to measure my jaws and forgot about it.

 

[PeterT]

Well drawing wasn't too difficult. I don't see a dimension for the side tongue relief so I'll remove my hard jaw to measure. I drew a double ended version in order to flip the jaw around & allow beavering away material from the other side. One thing I notice is the SHCS are 3/8 diameter so the counterbore is kind of a big hole (0.625" nominal). So if the tooling happens to intersect it, you lose a lot of grip contact. Maybe that's why I see thicker ones? I could also extended jaw length inboard of the bolt holes so its unencumbered material. That would make the jaws a bit cantilevered from the movable jaw base but don't think that would be an issue for light duty cutting. I wonder if that's what the commercial ones mean by 'offset' tongue position?

Soft Jaws - Flat End - American Standard Tongue & Groove

The American standard tongue and groove flat soft jaws you get from us can be used for Bison, Buck, BTC, Cushman, TMX, PBA, Yuasa & Rohm, and other chucks.

eagletoolandsupply.com