Parlec Vise Hopeless?

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Bill_Cook
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Post by Bill_Cook » Fri Aug 14, 2009 9:39 am

I've got an old worn vise on the mill. I've taken to snugging the hold down bolts on the the movable jaw after getting it against the work, then tightening.
To knock the part down, a chunk of lead does just fine. It doesn't bounce or mess up the work.
It probably doesn't matter, but I like to hit it an odd number of times.

BC

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SteveHGraham
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Post by SteveHGraham » Fri Aug 14, 2009 5:02 pm

I was going to work on this early in the day, but I started off by crashing a cutter (not rotating) into a workpiece and knocking the mill out of tram. I was not sure whether I had destroyed the mill or what, but I wasted no time in wetting my pants, just to be on the safe side. Looks like the mill is okay. One thing surprises me. No matter how tight the nuts are, you can move the head by turning the worm gears. I didn't notice that before.

After I was done weeping and tramming the mill, I put the vise back, stuck two 123 blocks in it (centered properly) and cranked it down. The bottom block stayed tight. So it looks like the vise works, provided the operator has some clue what he's doing.

Here's a great tip I hope you will all put to good use. When the power feed slows down suddenly, it doesn't mean there is something wrong with it, and you should probably take it out of gear.
Every hard-fried egg began life sunny-side up.

toastydeath
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Post by toastydeath » Fri Aug 14, 2009 10:46 pm

Am I the only other person who has stopped knocking parts down in the vise?

I used to do it, but I get much better flatness and parallelism without it.

The only time I knock a part down is when I know the jaw is lifting and can see it on an indicator. And then my first course of action is to disassemble the vise and clean it, and with any sort of angle lock mechanism this usually solves the problem.

Often, what is bringing the part up of the parallels is just the part itself being out of form in some way and has nothing to do with the vise or parallels. Hitting it, in this case, doesn't make the problem better.

Harold_V
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Post by Harold_V » Fri Aug 14, 2009 11:28 pm

SteveHGraham wrote: One thing surprises me. No matter how tight the nuts are, you can move the head by turning the worm gears. I didn't notice that before.
A word to the wise.

Do not attempt to turn the worm gears once the restraining screws (bolts) are tightened. The worm assembly is known to self destruct.
Use a soft hammer and choose your spot carefully to make the final adjustments, always with the bolts snug, but not fully tightened.

Harold

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Mark Hockett
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Post by Mark Hockett » Sat Aug 15, 2009 3:40 am

toastydeath wrote:Often, what is bringing the part up of the parallels is just the part itself being out of form in some way and has nothing to do with the vise or parallels. Hitting it, in this case, doesn't make the problem better.
toastydeath,
Good comment. One way to verify this is to rotate the part 180 degrees so the jaws are contacting the opposite faces of the part. If the parallel on the opposite side is now not touching you know its a problem with the squareness of the part.
Mark Hockett
http://www.islandtechent.com/

gmann109
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Post by gmann109 » Mon Aug 17, 2009 8:54 pm

lakeside53 wrote:Happens often on my brand new Kurt 688 also.... A lot depends on "how" you tap down the part, and the shape of the part. If the part isn't parallel to the vice jaws, something wants to move. Without the use of cylinders, ball etc, you can only stop that within certain limits and "hammering" may not help.

A slightly loose parallel doesn't always mean "bad". If it's loose by a few 10ths, it will slide out...
Hello.

I don't mean to steal this thread but I'm not too far off topic since I 'm talking about mill vises.

Are you saying that a brand new Kurt will lift anyway? I just ordered a new D765 and it better not lift or it's going back to Mother Enco. . Since I got my Webb mill working nicely, I've discovered that my H.F. 100 pound 6" non-adjustable mill vise should be relegated to door stop usage. If has the dreaded lift that's incurable. I used to put up with it, but I'm not going to do that anymore. I have a set of 1/8" parallels and I'll be adding a 1/4" set soon. I sure hope they will stay tight or I wouldn't know what to do.

I sure won't be hitting it with a hammer to get to to work, either. After all of Kurt's advertising, it would be strange indeed if a new one has any lift to it at all. I presume that yours is adjusted per the manual.

They state in the manual that every pound of forward force gives 1/2 pound of angular downward force. I don't know the angle since it only has a drawing but no indication of the degree of the angle. If looks like about 75 degrees?

They also mention that "jaw plates must be used". I presume that these are plates like loose soft jaws to protect the base metal of the vise jaws. Sounds like a good idea to me.

I will have a very bad feeling if my new vise that I don't even have yet is going to lift.....(gulp).

Help me out.....make me feel better.......phew. :(

lakeside53
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Post by lakeside53 » Mon Aug 17, 2009 9:14 pm

Sure.. if the part isn't parallel to both jaws and the uplift forces produced when clamped exceed the downward force from the jaw, it will lift.

It's all matter of degree. As one of the other posters mentioned, excessive clamping (real easy to do on a Kurt) can be a problem. Backing off the pressure can help a lot.

Round bars and whatever are often required until the part is reasonably symmetrical to the jaws.

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GlennW
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Post by GlennW » Mon Aug 17, 2009 9:19 pm

Any vise can and will lift under the right(wrong) circumstances. If you have jaws that are 1 1/2" tall, use 1 3/8 parallels and tighten the tar out of it, good luck!

A little common sense goes a long way.

Still don't know why they refer to it as "common" though. :?
Glenn

Operating machines is perfectly safe......until you forget how dangerous it really is!

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mechanicalmagic
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Post by mechanicalmagic » Mon Aug 17, 2009 9:33 pm

gmann109,
It's been a long time since I read the Kurt manual, but I'll offer an opinion anyway.
Kurt supplies o-rings that hold the jaws up, allowing the jaw to pull down when tightened.
If the jaw is already on the deck, it can't move down more than the thickness of the oil. And depending on oil/chips and the phase of the moon, it might lift. I'm not talking big numbers, but .0002" can feel like a mile.
The other thing that can happen, the base can flex. Again, we are talking tenths.

When you get your new vise, I suggest you set a thin (1/2") part high on parallels.
Mount your best DTI and place the tip on the part, near the movable jaw.
Tighten.
Watch for rise or fall.

If you don't like the movement RTM. Try again.

Dave J.
Every day I ask myself, "What's the most fun thing to do today."
9x48 BP clone, 12x36 lathe, TIG, MIG, Gas, 3 in 1 sheetmetal.

gmann109
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Post by gmann109 » Mon Aug 17, 2009 9:41 pm

mechanicalmagic wrote:gmann109,
It's been a long time since I read the Kurt manual, but I'll offer an opinion anyway.
Kurt supplies o-rings that hold the jaws up, allowing the jaw to pull down when tightened.
If the jaw is already on the deck, it can't move down more than the thickness of the oil. And depending on oil/chips and the phase of the moon, it might lift. I'm not talking big numbers, but .0002" can feel like a mile.
The other thing that can happen, the base can flex. Again, we are talking tenths.

When you get your new vise, I suggest you set a thin (1/2") part high on parallels.
Mount your best DTI and place the tip on the part, near the movable jaw.
Tighten.
Watch for rise or fall.

If you don't like the movement RTM. Try again.

Dave J.
Will do! Thanks.

One thng is sure, a Mill is pretty near unusable without a vise that will at least hold the part soundly.

To be continued, I suspect. LOL. :D

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mechanicalmagic
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Post by mechanicalmagic » Mon Aug 17, 2009 10:17 pm

gmann109 wrote:One thng is sure, a Mill is pretty near unusable without a vise that will at least hold the part soundly.
Sorta depends on your needs. I've whacked parts on Kurts for a few decades. Most times, didn't even check to see if it was needed. (Probably came from earlier times, on other vises.) And to tell the truth, I rarely check the thickness. So what's the big deal? .0005" on a weldment is usually a waste of time.

The tolerances of the part determine the procedures, methods and verification. (OK, I do try to plane wood to +-.003", but I'm not a bit picky.)

Dave J.
Every day I ask myself, "What's the most fun thing to do today."
9x48 BP clone, 12x36 lathe, TIG, MIG, Gas, 3 in 1 sheetmetal.

lakeside53
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Post by lakeside53 » Mon Aug 17, 2009 10:40 pm

Yes, you are correct. We should differentiate between the vice components lifting and the part lifting...


And yes, even if the part lifts, the Kurt will hold it securely!

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