What Material To Us For Vise Jaw That Will Compress Slightly More Than Aluminum?

gmoushon · Jul 24, 2021

I'm cutting the vise jaws for a production run of 200 small parts. I want to hold 15 parts across a 10" vise jaw. I've done this in the past with 6" jaws but if one or two of the parts are say, .002-.003 out of tolerance, the shorter parts come out of the vise.

My thought is to use a plastic material on the front vise jaw to allow a little compression and take up any slack. There's very little machining force on the part for this second operation.

I picked up some Delrin to try, (this is my first experience with Delrin,) but now that I have the Delrin on the bench, it seems almost as hard as 6061.

Do you think the Delrin will compress enough or do I need to look into a different resin material?

Thanks!
gm.

MrWhoopee · Jul 24, 2021

Nylon might be the ticket here. The problem to watch for is the plastic deforming and staying that way.

dian · Jul 24, 2021

delrin/acetal has a compressive modulus about 1/25 of aluminum.

mhajicek · Jul 24, 2021

Yes, Delrin is far softer / more compressive than aluminum. I was going to recommend PEEK, as it's significantly harder and stronger than Delrin, though it would be a bit pricey.

Edit:

What about using aluminum for the solid jaw with a pocket, and plastic just for the moveable jaw?

PeteM · Jul 24, 2021

For low quantities, I'll cut strips of softwood (lattice, etc.) to capture parts on the movable jaw side. Just crush them until the vise is about normally tight. With moderate cutting forces, these capture and retain parts firmly. Balsa will handle even highly irregular parts as a prototyping expedient.

Just throw away the deformed bits after. Disposable plastic strips might also work, but the crushed cell structure of wood seems effective and the material isn't as slippery as most plastics.

This was, of course, before lumber dealers started selling wood by the ounce.

If you deform plastic with a high part in one setup, seems likely to me that a low part in the same pocket might move the next time around if you try to make permanent plastic jaws. Stay below the deformation limit (high durometer rubber??) and you might have enough clamping force for somewhat permanent jaws and variable thickness parts.

Best if you can have most of the cutting force working against the fixed jaw.

Gordon Heaton · Jul 24, 2021

A lot of plastics are slippery. I prefer leather, and just on the moving jaw of course.

specfab · Jul 24, 2021

For a slightly different approach: I have frequently used a business card between the movable vise jaw and a stack of "identical" parts being held in the vise. It can accommodate a few thousandths of differential compression between parts in a vertical stack, or lined up next to each other between the jaws. Fairly good frictional properties as well.

If you go through enough mergers and acquisition activity in the places where you work, you usually have enough defunct business cards for every clamping situation. ;-)

TDegenhart · Jul 24, 2021

high durometer urethane rubber.

Tom

Booze Daily · Jul 24, 2021

I use a strip of Teflon.

kustomizer · Jul 24, 2021

I have had good luck using a keywat cutter to cut a slot in the live aluminum soft jaw and inserting a 3/16 x 3/16 strip of nylon full width of the jaw that sticks out about .02 farther than the aluminum for cutting harder parts and square o-ring material for real soft parts

Luke.kerbey · Jul 24, 2021

Could you machine a tapered location to negate any deviation in the parts? Maybe like 2-5 degrees? Then use aluminium as the material and allow them to bed in the taper surface?

Or use a hard fixed parallel jaw and a sprung loaded piece to take up any slack in parts?

mhajicek · Jul 24, 2021

I've done this sort of thing with aluminum or even steel jaws. Just cut the "A" side of the parts from a strip the length of the jaws, flip it over as one piece for the "B" side. Parts are cut with the same tool at the same offset, size difference is almost zero within a strip.

Terry Keeley · Jul 24, 2021

I'd think delrin or some other plastic would deform but would it return to it's original size so the next run of parts are held properly?

I think Tom in post #8 might be on the right track. I just made some isolation mounts from 80 duro urethane and that is pretty solid, something a little stiffer would work I'm sure.

edit: I see that was mentioned in post #2...

stephen thomas · Jul 24, 2021

If most of the part is supported in the pockets in the metal fixed jaw, or even just against the fixed jaw, i have use the following materials for various ops:

(You did say cutting forces are minimal)

thick pape/cardstock
cardboard (the kind on the back of notepads, not corrugated)
Wood, just like PeteM describes.
old flat leather belting
Baler belting form Central Tractor (this does not work well for small parts as it tends to try to push them up)

That said, when such things are necessary, i'm usually trying to hold 3 or 4 parts, not 10.

smt

gmoushon · Jul 25, 2021

Thanks for all the feedback. Excellent ideas.

I'll start with the Delrin since I have it on hand and see how it goes. Making the movable jaw modular will allow me to change it if needed.

Here's a couple pics of the setup and the part. Width of the part is 0.250 with a length of 1.61.

Thanks again.
gm.

kustomizer · Jul 25, 2021

gmoushon said:
Thanks for all the feedback. Excellent ideas.

I'll start with the Delrin since I have it on hand and see how it goes. Making the movable jaw modular will allow me to change it if needed.View attachment 325246 View attachment 325247

Here's a couple pics of the setup and the part. Width of the part is 0.250 with a length of 1.61.

Thanks again.
gm.

I was thinking you had individual parts, in strips like that I would simply cut the soft jaws to match the profile, remove all the material I can while still leaving them connected until the last op then seperate them, I wouldn't put any plastic in therr at all

michiganbuck · Jul 25, 2021

With having a surface grinder you might grind verticle groves and put on a strip of electrical tape on both jaws.

HuFlungDung · Jul 25, 2021

I'd try the Delrin, or UHMW and face it with a 'peel and stick' abrasive sheet. I use the stuff that comes in rolls for a 5 or 6" disk sander, not sure what else is handy to get.

4GSR · Jul 25, 2021

I use strips of roofing lead I put in between the back jaw and work piece. When it gets thin, fold it over and reuse.

kustomizer · Jul 25, 2021

10's of thousands of these goofy little bastards have run through these same 6061 jaws over the years, 4 operations, we put in a new blank in the back, a 3rd op strip after being broken in half in the front. 4 separated parts go in the right vise for the final op.Push the green button, when it stops you flip the back strip 90 degrees so you can do the end work, put 4 more parts in the right vise,green button, Put a new blank in the back, the last 4 in the right vise, take the strip from the rear station, break it in half and load them into the front, start it all over again.Whatever wear is in the jaws is even and polished now so they make better parts now than they did when new.

What Material To Us For Vise Jaw That Will Compress Slightly More Than Aluminum?

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