Vise Abuse

[rmac]

If I clamp something off to one side of my woodworking vise, the movable jaw will rack (twist) so it's not parallel to the fixed jaw and it only contacts one corner of the work. This is pretty common, and the solution is to pack the unused side of the vise with something about the same thickness as the work so that the jaws stay parallel when the clamping force is applied.

But what about a milling vise? I would think the same kind of twist would be a problem, and that the same solution would apply. But I see guys on YouTube hanging stuff out of one side of the vise all the time without any concern about the jaw twisting.

Is this acceptable practice? And if not, how do you come up with packing that's exactly exactly exactly the same thickness as the workpiece so that you're not applying more pressure to the packing than to the work? Or is there some other way (besides the packing) to manage the problem?

I hope this makes sense.

-- Russell Mac

[SteveM]

Yes, it's just as much abuse on a Kurt D-60 as it is on a Craftsman woodworking vise, it's just not as visible - until, of course, the part flies out of the vise!

If the jaw twists, the work will be held more on the inside edge than the outside edge, and a helical end mill on the outboard end can pull the work up.

As far as packing the other side of the vise, you can have a selection of blocks handy and a machinist jack for precise sizing. You could just use a nut an an assortment of different lengths of matching bolts.

Steve

[earlgo]

Sometimes the step blocks used in pairs will work but they result in about eighth inch increments, but a shim or two will help.

These used in the saw vise.

I imagine that the adjustable parallels that languish in your toolbox would work, too, if you didn't clamp things too tightly.

or you could use a (homemade) screw jack if the part is large: https://www.mcmaster.com/jacks/wrench-a ... rew-jacks/

--earlgo

[RSG]

Nice idea Earlgo

[pete]

Every post I've ever read about that one sided mill vise clamping frowns on the habit. It puts a huge amount of racking torque on the moving jaw it's not really designed for. My guess is the damage it finally causes doesn't show up until it's too late with extra wear on the jaw guide ways and maybe more wear on the screw and nut. Besides that, it vastly reduces the holding power the jaw exerts on the part. And I've noticed exactly the same on a few of the YT machining channels. In some instances there was no need to position the part to one side at all. Any decent milling vise today isn't exactly cheap. So I'd very much agree with Steve's point, if it's not a good idea for even a much cheaper woodworking vise, I'll pass on knowingly doing the same to a mill vise.

I'd also agree with Earl about those adjustable parallels and the LIGHTLY part. I automatically thought my Starrett's were hardened until someone mentioned there's weren't. Mine aren't either, or at least there not very hard. So hard clamping when used as an adjustable spacer might not be a good idea. For some reason using a pair of step blocks in that orientation never occurred to me, so many thanks for that clever tip Earl.

[Rich_Carlstedt]

yes, I don't think I would want my adjustable parallels used in a vise.
I use my mill step blocks and for the in between sizes I bought a very cheap set ( 2 actually ) of feeler gauges
from a auto store ( The cheapest they have ) and it is about 1/2 " thick ,
I don't care how accurate or what the markings say or if they get damaged , I just use them to take up space in the vise.
So my range is .001" to infinity
Its easy for me to know whether I have my good set or the vise set. The good set has a knurl wheel "clamp" to lock the gauges settings
and the cheap set (s) just have a loose rivet holding the set ------like I said, cheap...
Like Earl shows in his picture, I also have an extra set of step blocks near my saw
Rich

[rmac]

Thanks, everyone. I wasn't sure, but I sort of suspected that it was important to be concerned about racking. Too bad some of the YouTube guys aren't.

Adjustable parallel: I'd never thought of this, but agree that it's better to keep items marked "Starrett" in the drawer marked "Don't mess this stuff up".

Machinist's jack: I have a (homemade) pair and have used them successfully for packing.

Nut and bolt: Like the machinist's jacks, often too big to work with the small parts I want to hold.

Feeler gauges: This was a real forehead slapper for me because I dreamed up a similar arrangement for use in the woodworking vise about ten years ago, but never thought to bring the idea over to the other side of the shop.

Mill step block: New idea for me, too. Thanks!

Anyway, this is all very helpful. Thanks again.

-- Russell Mac

[Harold_V]

Russ,
I specialized in small work when I ran my commercial shop. I handled small parts regularly as a result, and often had to use one side of my vise to do so. My policy was to use one of the parts on the opposite side of the vise, always at the extreme end to assure the part being machined was being firmly clamped. I had a policy of holding dimensions, so it would be unusual for my parts to vary enough to be of concern. As a result,
any part would do. When a side isn't required, I like to keep the work centrally located in the vise.

On the subject of adjustable parallels----they are outstanding for measuring windows (pocket cuts). Much more precise than calipers.

[rmac]

My policy was to use one of the parts on the opposite side of the vise, always at the extreme end to assure the part being machined was being firmly clamped.

Yes, that's a great idea if you have that second part. Sometimes a remnant from whatever stock you started with can also be used the same way. When neither is available, I really like the feeler gauge idea.

On the subject of adjustable parallels----they are outstanding for measuring windows (pocket cuts). Much more precise than calipers.

On the subject of precision measurement----I never thought it would happen, but I've found myself trying to make sub-thousanth measurements a couple of times with my little engines. (Getting a good piston-to-cylinder fit, making bearings fit just right with their mating parts, etc.) I know there are very fancy and expensive tools for measuring bores, but I wonder what kind of precision I can expect with telescoping gauges and a micrometer. If I get everything clean, and use perfect technique, and hold my mouth just right, should I be able to measure tenths?

And what about holes too small for a telescoping gauge? Gauge pins, I guess?

-- Russell Mac

[GlennW]

You should definitely be able to measure to tenths with telescoping gauges. I'll quite often use both telescoping gauges and bore gauges just as an exercise to prove that.

I have use gauge pins up to .5". and mainly use the .250" and below for small hole gauging.

[Bill Shields]

It is all a matter of holding mouth right and 'feel'

Do not forget that if it appears to be a tight fit...just warm it a bit and the fit will change

[GlennW]

Here is a post from Harold regarding the use of telescoping gauges:

I spent considerable time running a Heald 271 internal grinder, grinding bearing housings for the guidance system of the Sergeant Missile. Tolerance for the critical diameter (the bearing bore) was + .0002", - 0000". Two other diameters (counterbores) were also ground, although with less demanding tolerances.

One of the things I had in my favor was flood cooling. Working dry to tight tolerances isn't a reasonable process, as heat becomes ultra critical. Temperature change, alone, is enough to push parts out of tolerance.

I'd like to comment on the use of telescoping gauges, which I also have used extensively for tight tolerance work. Contrary to popular opinion, I highly recommend one go back in the hole a second time when attempting to determine size. It's not quite as important for small diameters, where the tight radius tends to steer the telescoping gauge to center, but on larger bores, that's not as likely. For that reason, my habit is to go in the hole with the gauge extended slightly larger than the bore, the lock snugged, but not tight. The gauge is then dragged through the bore, all the while the gauge is being guided side to side, finding center.

Once pulled through the bore, I go back. Here's where there is high controversy. My logic is, and it has been proven time and time again in practice, is that if the gauge falls through the bore, I didn't have it on center originally, so the reading I would have achieved was erroneous and should be ignored. By contrast, if, in the process of repeating the operation, the gauge found center and the feel I found originally was repeated, I accepted that as a proper feel. The only thing left, at this point, is to repeat the feel when measuring with a micrometer.

Some feel that several iterations should be accomplished, with an average of the readings being considered proper. I firmly disagree with a that kind of logic, as the moment a false reading is introduced, one can not hope to achieve a reliable reading. A second pass through the bore, before measuring, immediately determines if the inspection was acceptable, or not.

Harold