mill vise problems--am I doing something wrong?

I have a Sherline vertical mill (the 5000 series) and I keep having a
problem with my aluminum workpiece pulling loose from the mill vise.
I have NEVER had very good luck getting the Sherline mill vise to hold
aluminum terribly well. Is this a deficiency of their mill vise?
Would a different mill vise solve the problem? Is it possible that .
010" cuts are too much?
Reply to
clayton
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There has been mention of this on the Sherline Yahoo group lately, following extensive discussion and evaluation of Sherline chucks with holding problems.
It appears that (assuming you are using the vise properly) you have a defective vise. As best I can remember, mine has never let a part loose even once in several years of use. It grips as well or better than comparable models you could replace it with. .010" cuts are very conservative in 6061.
I wonder if people use the trivial procedure of yanking on the workpiece after gripping it in the vise. I've never had a workpiece come loose from any vise on any mill if I could not pull it loose by hand. I also do the obvious things like gripping enough of the part (probably always 1/8" or more), and always either gripping in the center of the vise or using a spacer on the opposing side. If such practices do not yield perfectly reliable hold, then I have to believe the vise is defective.
Alan
Reply to
Alan Wright
One other note: these vises (i.e. screwless type) can pretend to be tight when they are not. They will appear to tighten because they are engaging the wrong notch underneath, and thus at full tightness do not yet contact the part. However, in such case the part will be loose to the touch. It is imperative to unscrew the thing far enough to engage a notch far enough in to tighten on the part. This should be apparent to anyone who has tried one, but thought I would make sure.
Alan
Reply to
Alan Wright
I cannot imagine what you are doing to cause this problem from your information supplied, but it is highly unusual. Please describe what you are doing and how. Steve
Reply to
Steve Lusardi
I don't know whether there there was more to what you posted -- both quoted samples that I have seen have not shown more, so I don't know whether the following applies or not.
If the workpiece is sticking out of the vise by a height in excess of perhaps four times the height of the jaw grip, then there is a major problem with leverage working against you.
If you are trying to hold something withoutparallel faces against the jaws, such as round stock stood on end in the milling vise, there is a great chance that it will slip under cutting forces -- even on a machine as small as a Sherline.
A rectangular workpiece is better held with the wide dimension across the width of the vise, and the end resting on the bottom of the vise.
A workpiece with an irregular surface in contact with the jaws is more likely to slip, because there is really very little material in direct contact with the jaws. This can be helped somewhat by putting cardboard between the workpiece and the jaw surface so it produces a larger contact patch.
So yes, more detail about the workpiece and how you are attempting to hold it would help us to figure out what is wrong.
Good Luck, DoN.
Reply to
DoN. Nichols
I use a sherline vise on my Emco Compact 5 milling adapter. It gets lots of use and has never let me down.
Reply to
NewsGroups
============== How big an end mill are you using? Feeds? Speeds?
One trick to hold relatively smooth work pieces in a vice with smooth jaws or on a smooth faceplate is to insert a piece of rough brown paper as from a paper bag. In general the paper is uniform in thickness so parallelism to the fixed jaw should not be affected. It can be helpful to put a rod in between the part and movable jaw parallel to the base so the part will be clamped square to the fixed jaw and not lifted by any tilt of the movable jaw.
I have not tried this my self (brown paper was always enough), but some of my shaper books suggest using worn emery paper in place of the brown paper for even more "bite."
Unka' George [George McDuffee] ------------------------------------------- He that will not apply new remedies, must expect new evils: for Time is the greatest innovator: and if Time, of course, alter things to the worse, and wisdom and counsel shall not alter them to the better, what shall be the end?
Francis Bacon (1561-1626), English philosopher, essayist, statesman. Essays, "Of Innovations" (1597-1625).
Reply to
F. George McDuffee
=============== Good observation/question.
I had assumed (and so apparently had everyone else) that the problem was a rectangular part in the vise, for no good reason.
It may indeed be round, irregular, etc.
Question to original poster -- what is the shape of the aluminum piece you are trying to clamp?
Unka' George [George McDuffee] ------------------------------------------- He that will not apply new remedies, must expect new evils: for Time is the greatest innovator: and if Time, of course, alter things to the worse, and wisdom and counsel shall not alter them to the better, what shall be the end?
Francis Bacon (1561-1626), English philosopher, essayist, statesman. Essays, "Of Innovations" (1597-1625).
Reply to
F. George McDuffee
The emery paper method works well also for clamping several pieces at a time for gang milling, when there is a few thousandths difference between the width/diameter of the parts. The emery cloth will hold it well. At work, we hold 5 pieces of 7/8" bronze round stock about 4" long standing on end in the 2" deep vise, and mill wrench flats on the upper portion of the rods with a horizontal mill, using 1/2"X4" dual cutters and an abuttment stop to help keep them from leaning over from the feed pressure. This will not hold the parts without the emery cloth. One or more will always be loose in the vise jaws.
RJ
Reply to
Backlash
Square workpiece.
Reply to
clayton
Is this perhaps a problem of a worn out vise? I bought the mill with this vise, used (very used). I will try the proposed technique for improving clamping with some fine sandpaper between the workpiece and the jaws.
Reply to
clayton
I tried to use both a 3/4" and a 3/8" end mill, two flute, without success. I tried very low speeds (a few hundred RPM) and very high. I tried even .005" slices. I'm told that I may need to use more aggressive cuts to prevent the end mill form just smearing the material.
Reply to
clayton
Good catch. I put in a piece of 6061 scrap that I cut off the workpiece with a bandsaw, one small enough that it was just barely above the jaws--and I was able to run an end mill across the surface just fine. At .010" slices, it worked just great--not a single snag, stoppage, or loosening. I tried one pass at .015" and while it didn't stop, I could see that this was the upper limit of what I could do.
When I turned that scrap on end, so that there was about 3" sticking above the jaws, the old problems started to appear.
So, does this mean that if you have a workpiece that is fairly big, you should get yourself a mill vise with very tall jaws? Does someone make a mill vise for micromills with varying height jaws?
Obviously, you should turn a workpiece the direction required to get maximum grip from the jaws, and mill vertically rather than horizontally--but sometimes that's just not possible.
Reply to
clayton
You can add a vise stop to the end of your vise on the fixed jaw by drilling and tapping a hole for a flat plate retained by a bolt. This sticks up above the vise jaws and provides a physical stop for the thrust pressure of milling. Another bolt with a locknut tapped into the upper part of the stop provides localized pressure at the top edge of the plate. A horizontal mill can snatch items right out of the vice without using this type of endstop to take the forces. A Bridgeport generally pushes parts over more slowly, but can bust a cutter for you..
RJ
Reply to
Backlash
Help me to visualize this a bit more. The vise has jaws held in place by a few screws. I can replace the current jaws with a plate that uses the same threads, but goes up several inches higher than the current jaws. What's this "bolt with a locknut tapped into the upper part of the stop"? What does this bolt screw into?
Reply to
clayton
Found an example here:
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Reply to
clayton
And always..always mill into the fixed jaw direction if you have a sloppy vise
Gunner
"Pax Americana is a philosophy. Hardly an empire. Making sure other people play nice and dont kill each other (and us) off in job lots is hardly empire building, particularly when you give them self determination under "play nice" rules.
Think of it as having your older brother knock the shit out of you for torturing the cat." Gunner
Reply to
Gunner Asch
You got the idea! This will also allow you to repeat position parts in the mill vise. It's one of the handiest things I use on the mills. The one I poorly described is a piece of 3/8" flatbar bolted to the fixed jaw of the vise to protrude several inches above the jaws. An allen head bolt is tapped into the upper portion, in line with the direction of the table travel. A locking nut holds the bolt tight, but lets it protrude into the vise work area, a couple of inches above the jaws. The upper bolt acts as the actual stop, since it is now adjustable. I have one cut to shape to allow straddle cutters to pass over and around it while it supports tall pieces on a horizontal mill.
RJ
Reply to
Backlash

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