Soft Jaw best practices?

Hello.

I was using some soft jaws this weekend (steel parts, AL jaws) and got to wondering if there any not-so-obvious tricks I should be using. Currently I'm talking round work, so the profiles are simple but I have a few questions-

1) Do you the cut the jaw to exact size, or maybe a little over? For say a 1" diameter round feature, would you bore them to 1.000 or maybe 1.003"? Undersized will pinch and make them a pain to remove, too far O/S won't grip well.

2) Do you cut any relief on the bottom of the relived profile? Either to accommodate the errant chip or unseen bur?

3) Is it possible to safely get more than 2 items in soft jaws? I've always been taught and experienced that more than 2 objects (stacked laterally) in the jaws will leave at least 1 loose.

4) Is using a roughing endmill to leave a serrated profile of sorts a benefit? I had a rougher in the TC so that's I used and it worked very well so was just curious.

Thanks

Cole2534 said:

Hello.

I was using some soft jaws this weekend (steel parts, AL jaws) and got to wondering if there any not-so-obvious tricks I should be using. Currently I'm talking round work, so the profiles are simple but I have a few questions-

1) Do you the cut the jaw to exact size, or maybe a little over? For say a 1" diameter round feature, would you bore them to 1.000 or maybe 1.003"? Undersized will pinch and make them a pain to remove, too far O/S won't grip well. I cut them so the nominal part just slips.

2) Do you cut any relief on the bottom of the relived profile? Either to accommodate the errant chip or unseen bur? Only if needed for the part.

3) Is it possible to safely get more than 2 items in soft jaws? I've always been taught and experienced that more than 2 objects (stacked laterally) in the jaws will leave at least 1 loose. I saw this is a good rule of thumb. Can more be done? Sure, but I don't find it to be reliable with just a jaw.

4) Is using a roughing endmill to leave a serrated profile of sorts a benefit? I had a rougher in the TC so that's I used and it worked very well so was just curious. The only way that really works is if the material you are holding onto is softer

Thanks

Click to expand...

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Cole2534 said:

Hello.

I was using some soft jaws this weekend (steel parts, AL jaws) and got to wondering if there any not-so-obvious tricks I should be using. Currently I'm talking round work, so the profiles are simple but I have a few questions-

1) Do you the cut the jaw to exact size, or maybe a little over? For say a 1" diameter round feature, would you bore them to 1.000 or maybe 1.003"? Undersized will pinch and make them a pain to remove, too far O/S won't grip well.

2) Do you cut any relief on the bottom of the relived profile? Either to accommodate the errant chip or unseen bur?

3) Is it possible to safely get more than 2 items in soft jaws? I've always been taught and experienced that more than 2 objects (stacked laterally) in the jaws will leave at least 1 loose.

4) Is using a roughing endmill to leave a serrated profile of sorts a benefit? I had a rougher in the TC so that's I used and it worked very well so was just curious.

Thanks

Click to expand...

Yes, we do it all the time. We run jobs with 3-4-6 parts in soft jaw, these parts are also our 'high volume' running 100-300 at a time. BUT these are well dialed in and very short/stubby with only maybe 1/4-3/8" sticking up. It wouldn't be worth the risk to me if I was only making a handful of parts.... Ultimately I think it depends on your comfort level, what type of parts ($$ mats, etc), what/how you are cutting (facing to length or doing lots of cutting) and if the time savings make sense to "risk" throwing a part or breaking tooling.

I use a lot of aluminum soft jaws for steel parts but it also depends on the type or part we make.

Cole2534 said:

Hello.

I was using some soft jaws this weekend (steel parts, AL jaws) and got to wondering if there any not-so-obvious tricks I should be using. Currently I'm talking round work, so the profiles are simple but I have a few questions-

1) Do you the cut the jaw to exact size, or maybe a little over? For say a 1" diameter round feature, would you bore them to 1.000 or maybe 1.003"? Undersized will pinch and make them a pain to remove, too far O/S won't grip well.

Click to expand...

A lot of times I just go for something close. Plunge in a 3/8 endmill to hold a 3/8 round piece of stock.

Sometimes I get fancy, and swing some slighter bigger arcs than the diameter to get 3 or 4 point contact,
I'll do this especially if there is going to be any variance in the stock diameter or I have to do
some real hogging on it.

2) Do you cut any relief on the bottom of the relived profile? Either to accommodate the errant chip or unseen bur?

Click to expand...

No, just a nice crisp square corner endmill. Seems a relief would be a chip magnet and
make your life worse.

3) Is it possible to safely get more than 2 items in soft jaws? I've always been taught and experienced that more than 2 objects (stacked laterally) in the jaws will leave at least 1 loose.

Click to expand...

Depends.. I don't like to do that, but sometimes you have to.. When you have a million tiny
little parts to do. I certainly don't want to do any real hogging like that.. Several
ways I've done this.. On the moving jaw, just sliding in a couple pieces of a manilla folder
is enough sometimes. I also sometimes will use a hard-ish piece of rubber to take up any differences.

For repeat job I had, I actually made the moving jaw out of nylon.. worked great.

For rectangular stuff. You can always run them in strips and keep them attached to each other,
and break them apart GENTLY as your last machining operation, or just leave a small film
at the bottom and break them apart when they come out.

4) Is using a roughing endmill to leave a serrated profile of sorts a benefit? I had a rougher in the TC so that's I used and it worked very well so was just curious.

Thanks

Click to expand...

I've used sand paper, but I don't think it would help all that much, though you never know. Smaller
point of contact might help on something that is really slick.

My rule of thumb with soft jaws is to not use aluminum jaws on any steel job that has a quantity to them.
They mushroom out and you lose accuracy. 7075 helps but still does after a period of time.

I cut them size for size and sometimes .001"-.002" larger than the part.
Don't use a serrated, that has potential room for locating error.
Undercut only if you need it.

More than 1 part is doable,but you have to make sure that those parts are darn near identical in size or else you have one fly out.

I've found the biggest trick to soft jaws (aside from the ones mentioned) is corner relief, especially on smaller parts, and most especially on intricately shaped parts with small corner radii.

A lot of folks cut soft jaws to the outline of the part, and then can't get the thing to fit because CNC mills usually get sloppy on how they cut tight inside and outside corners, so they wind up removing material from the softjaw 0.0005" at a time until it fits. By the time it does, you've lost all quality contact holding the part in place.

gkoenig said:

I've found the biggest trick to soft jaws (aside from the ones mentioned) is corner relief, especially on smaller parts, and most especially on intricately shaped parts with small corner radii.

A lot of folks cut soft jaws to the outline of the part, and then can't get the thing to fit because CNC mills usually get sloppy on how they cut tight inside and outside corners, so they wind up removing material from the softjaw 0.0005" at a time until it fits. By the time it does, you've lost all quality contact holding the part in place.

Click to expand...

That is a really good point. Relieve your corners!! It makes life much more simple on second ops.

gkoenig said:

I've found the biggest trick to soft jaws (aside from the ones mentioned) is corner relief, especially on smaller parts, and most especially on intricately shaped parts with small corner radii.

A lot of folks cut soft jaws to the outline of the part, and then can't get the thing to fit because CNC mills usually get sloppy on how they cut tight inside and outside corners, so they wind up removing material from the softjaw 0.0005" at a time until it fits. By the time it does, you've lost all quality contact holding the part in place.

Click to expand...

Good call.

I would hate to think about how many soft jaws I make a year. Easily in the hundreds... possibly in the thousands. Nearly everything I do is small volume and ridiculously intricate so bear that in mind.

I generally cut my soft jaws .000 to .003 over depending on the shape of the part. The more close fits I have in the X direction and the more inside corners, the looser I make it. Any tighter than that and I start leaving marks on the part.

Pay really close attention to inside corners. I don't like to drive the cutter that is making the soft jaws into a corner that is anywhere close to the same radius as the cutter. Think .020 on the radius over nominal.

Get real used to using tangent arcs in your cam system to accommodate square outside corners in the part.

Prepare yourself mentally to adjust the Y and Z (and possibly the X) axis on the part after you run the first one. I know, a soft jaw should be perfect after you just got done cutting it... but it never is "perfect", but probably good enough for the first part to pass. But not good enough for very tight tolerances.

Space your soft jaws out. The closest I'll come to having completely closed soft jaws is a clearance of .030". I used to use old hotel key cards to space my soft jaws, but my wife started to get suspicious as to why I always had strange hotel key cards in my pocket of my work clothes... don't use them. That was a shitty Christmas.

Tighten the vise when you are cutting the soft jaws to the exact same torque that you will use when you machine the part. Put in your spacer as close as you can to the Z plane that the vise will be seeing the load, and use a torque wrench to tighten it. Vises move a tremendous amount depending on how much torque you put on the screw (think .01").

Get all you XYZ squared away, and have the first good part off the jaws... bore a hole at a known location on the unused portion of the soft jaw. Then etch in the location of said hole. Then when you need to get back into the jaws in the future (or if you fuck something up), it is simple to sweep it back in.

G00 Proto said:

I would hate to think about how many soft jaws I make a year. Easily in the hundreds... possibly in the thousands. Nearly everything I do is small volume and ridiculously intricate so bear that in mind.

I generally cut my soft jaws .000 to .003 over depending on the shape of the part. The more close fits I have in the X direction and the more inside corners, the looser I make it. Any tighter than that and I start leaving marks on the part.

Pay really close attention to inside corners. I don't like to drive the cutter that is making the soft jaws into a corner that is anywhere close to the same radius as the cutter. Think .020 on the radius over nominal.

Get real used to using tangent arcs in your cam system to accommodate square outside corners in the part.

Prepare yourself mentally to adjust the Y and Z (and possibly the X) axis on the part after you run the first one. I know, a soft jaw should be perfect after you just got done cutting it... but it never is "perfect", but probably good enough for the first part to pass. But not good enough for very tight tolerances.

Space your soft jaws out. The closest I'll come to having completely closed soft jaws is a clearance of .030". I used to use old hotel key cards to space my soft jaws, but my wife started to get suspicious as to why I always had strange hotel key cards in my pocket of my work clothes... don't use them. That was a shitty Christmas.

LMAO!!

Tighten the vise when you are cutting the soft jaws to the exact same torque that you will use when you machine the part. Put in your spacer as close as you can to the Z plane that the vise will be seeing the load, and use a torque wrench to tighten it. Vises move a tremendous amount depending on how much torque you put on the screw (think .01").

Get all you XYZ squared away, and have the first good part off the jaws... bore a hole at a known location on the unused portion of the back/stationary soft jaw. Then etch in the location of said hole. Then when you need to get back into the jaws in the future (or if you fuck something up), it is simple to sweep it back in.

Click to expand...

If your vise is moving .01" (!!) you have other issues to deal with... However, vises do move a bit (.001-.002" in normal circumstances IMO) so you should be clamping the same when machine soft jaws and clamping actual parts.

I tried to get "my " guys to do this and could not get it to register (pun intended)... this was a very easy 'concrete' way to pick up zero after you have machined them and needing to re-locate them for the same job...

Mike1974 said:

If your vise is moving .01" (!!) you have other issues to deal with... However, vises do move a bit (.001-.002" in normal circumstances IMO) so you should be clamping the same when machine soft jaws and clamping actual parts.

I tried to get "my " guys to do this and could not get it to register (pun intended)... this was a very easy 'concrete' way to pick up zero after you have machined them and needing to re-locate them for the same job...

Click to expand...

I swear some of the monkeys that I've had running machines could move the solid jaw anywhere between -.005 and +.010 depending on the cut of meth they were provided for "Work Release" that day. Ah the good old days. On the plus side, the "Work Release" convicts always showed up on time (prison bus) and always brought a damn good lunch (prison cafeteria) and they were always will to trade said lunch for a couple smokes or a $.99 cent airplane sized bottle of liquor... not that I would ever stoop to such nefarious deeds.

G00 Proto said:

Vises move a tremendous amount depending on how much torque you put on the screw (think .01").

Click to expand...

You need to get some better vises! My fixed jaw may move .0003"-.0004" max going from soft to just about hammering the handle tight.

DavidScott said:

You need to get some better vises! My fixed jaw may move .0003"-.0004" max going from soft to just about hammering the handle tight.

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Wow, you’re really calling me out on the carpet... I’d invite you to settle this in the parking lot, but since you are just one state away, I’d be concerned you might take me up on the offer

I threw a test indicator on an average soft jaw (Monster Jaw) in a Kurt 688. Zeroed the Indicator at lightly tightened (.000) and then took it to very snug with a regulation Kurt vise handle and it deflected .0060”. Keep in mind I weigh a whopping 140 lbs and get picked on by most average grade schoolers .

I’d try the same thing on my Orange Vise, but they are heavy and it’s hotter than the gates of Hell today. I’ll just keep my opinion that a vise can deflect up to .010” so plan accordingly.

G00 Proto said:

I’d try the same thing on my Orange Vise, but they are heavy and it’s hotter than the gates of Hell today. I’ll just keep my opinion that a vise can deflect up to .010” so plan accordingly.

Click to expand...

I have done that test with an Orange. The answer was -0.0002" in downward Z deflection under all 250lb of my fat ass pressing on the wrench. This is in a single station configuration.

It isn't magic or anything - the Orange just has the jaw carrier actively pulling down on the fixed jaw side, where as a Kurt's fixed jaw is held on with nothing but bolts.

gkoenig said:

I have done that test with an Orange. The answer was -0.0002" in downward Z deflection under all 250lb of my fat ass pressing on the wrench. This is in a single station configuration.

It isn't magic or anything - the Orange just has the jaw carrier actively pulling down on the fixed jaw side, where as a Kurt's fixed jaw is held on with nothing but bolts.

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I ti not the bolts (of course if they are loose!) but the key that is usually the culprit. I've had brand new vises have the key/slot interface having .002" slop. This will allow the jaw to flex and move. If you shim them, or re-cut, IME the movement will stop, or become very little...

G00 Proto said:

Wow, you’re really calling me out on the carpet... I’d invite you to settle this in the parking lot, but since you are just one state away, I’d be concerned you might take me up on the offer

I threw a test indicator on an average soft jaw (Monster Jaw) in a Kurt 688. Zeroed the Indicator at lightly tightened (.000) and then took it to very snug with a regulation Kurt vise handle and it deflected .0060”. Keep in mind I weigh a whopping 140 lbs and get picked on by most average grade schoolers .

I’d try the same thing on my Orange Vise, but they are heavy and it’s hotter than the gates of Hell today. I’ll just keep my opinion that a vise can deflect up to .010” so plan accordingly.

Click to expand...

I've seen the same amount of deflection on both my 688's. I'm also 140 lbs, so another data point.��

I have a ton of kurt vises old and newer and I havent noticed any deflection, Now thanks to you clowns I am going to check mine cause I am curiuos .

we hold very tight tols on them and repeatability is dead nuts,I do notice a shift of a thou or 2 when someone else runs one machine with a set of vises on it. going to have to check those particular ones out with the person doing the tightening and they dont tighten hard either but I am wondering if my tighten is a tad difference than theres, just that little extra can make a difference.

Do you guys reuse you soft jaws for the same job, as in they have been taken off and reinstalled?
Do you make any kind of alignment marks or features to get both halves lined up.

The few that I have made I had the jaws touching the vise base and eyeballed up the left side even when installing the blanks. I then took a skim cut off the top and left side (maybe 1/8” cut 1/2” deep off the side), figuring I could indicate them back in.
I still had to fiddle around to get the movable jaw lined up nice. It’s a Kurt DX6

Would have been quicker to make new. I broke down and ordered Monster Jaw 10 packs for $140 shipped.

Thanks


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I can't believe I got half way through these replies before it dawned on me that these are soft jaws on a vise. Coffee not working this morning.
Multiple parts stacked in lathe jaws made no sense.