VISE OR TECHNIQUE

I have a small vise in my CNC mill that when I tighten stock on parallels, raises the material approx .015"
I'm told that a good vise cams down when tightened.
I've also been told that banging the stock down while tightening is a normal procedure.
went to Busy Bee, they have several vises to choose from, some where Kurt type
All their vises exhibited the same if not worse raising of the stock problem.
So I have two questions, Is there a reasonable vise that holds the material down?
or is there a method that automatically zeros the Z axis upon touching the stock in program control
I would assume that the vise / stock would need to be isolated from ground and that the tool bit
would send a ground to the control, re zeroing the axis for each part.
Is this done? or what is the recommended way to do this, besides banging the stock down?
usually just using aluminum, but trying to do a consistently good job.
Thanks Peter
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Put a piece of round bar between the work and the moveable jaw.
--
Ron Thompson
On the Beautiful Mississippi Gulf Coast
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Peter Kiproff wrote:

What type of vise? Sounds like a drill press vise or maybe something better in design that has been trashed. I rarely bang stuff down. If you have a bowed or twisted surface and bang it down, how flat do you think your newly cut surface will be upon unclamping? Lifting .015 at front, rear, or both? Lot's of people did not like the old Bridgeport vise. Parts would tend to lift at the front edge, unless you set up the vise properly. That is done by clamping something thin at the top of the jaws before final tightening of the front jaw. Then bang down the sliding block to minimize the lift potential, and then tightening the front jaaw. Be sure the jaw is also bottomed to the bed of the vise. If you are using some type of drill press vise, you are wasting your time. Toss it and get a real one.
What machine/control are you using? Most controls have an auto offset registering method. If your setup (see above) is decent, you should not have to set offsets for each part, they should be all the same.
Nice work can be done with junk, but it is a damn sight easier with good tooling.
michael
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I always tap the material down until the parallels are snug. this will give you the best results.
-- Roger Shoaf If you are not part of the solution, you are not dissolved in the solvent.

normal
material
the
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Grant Erwin wrote:

Works for me too. I think if there's enough clearance and you smack the part hard enough, it actually rebounds. Several light taps generally works better.

I've had a fair number of used Kurt vises apart and I've never seen any O-rings. Can you elaborate on just where they are supposed to be installed? (never had a new one apart...)
Jon
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Jon Anderson wrote:

I got a couple of new Kurts, 688 I think is the mod #. The o-rings are supposed to go under the movable jaw IIRC. Whatever, they are still in the bag they came in, somewhere. Haven't trashed any parts not using the o-rings, and it's been almost 3 years.
michael
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I note Peter said Kurt type, not a Kurt - I'm guessing he was describing the style of vice. Busy Bee sells the lowest grade stuff, I'd be shocked if it was an actual Kurt vice he was taking about (but I've been wrong before :). I think the problem you're having is common, if its a small piece at the top of the vice jaws the force of tightening tends to push the work up. light blows with a dead blow hammer works for me. IMO a poor quality vice will constantly torment you, every time you use it you'll be paying for the low initial price. Maybe have a look at KBC if you're in Canada and in the market for one - they have a broader selection, some cheap, some good (usual no connection disclaimer)
Mike

normal
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the
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When I bought mine, I was told by the salesman (man) that those were needed for really square face to face hard metal work with precision flats.
Haven't - but found the document on how to take it apart on the Kurt web site. That was nice to get.
Have to do it I guess. Hum.
Martin
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Kurt vises use the original "AngLock" principal. That is for every pound of clamping force exerted, 1/2 pound of force pulls the movable jaw down. The "O" rings are needed because this works so well that when using parallels it is possible that after clamping the part the parallel on the movable side will be loose many times. The "O" rings fit in 2 grooves under the movable jaw. You can see the principal in the back cover of our 2002/2003 catalog on our website, www.kurtworkholding.com, and find instructions for the "O" rings.

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Many thanks, Steve. I pulled down the installation instructions at http://www.kurtworkholding.com/downloads/guides/D-Series_O-Ring-Chip-Guard.pdf and saw a recommendation against using the O rings with step jaws, which is what I use about a third of the time. I assume the default in that case is not using the O rings at all? I'd hate to have to swap them out every other time I switched jaws.
Best wishes, Mike
(Steve Kane) wrote:

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