Kurt DX6 Jaw lift problem.

I have a pair of Kurt DX6 vises I use in my Sharp VMC. One of the vises has about .022" jaw lift when it has 4" stock clamped in the jaws. The other vise lifts maybe .002"or less. I have cleaned and adjusted them both no matter how I adjust this one vise it always lifts way too high.

Here is my setup I have some shop machined soft jaws 6061 T6 with a step milled in .210" deep. I mill the step in with the jaws clamped together. I give the jaws a wrap as I am tightening them with a dead blow hammer when I use them and also before I machine in the step. Left vise is fine but the right vise lifts too much.

I have checked my machine bed and the vise bed both are right on the money. I used a Tschorn probe to get my readings.

I have checked the half moon disc it is clear of chips and is greased. I have a call into Kurt but they are not going to get back to me until Monday and I have work I want to do.

Any suggestions are appreciated.

The older version has a set screw in the movable jaw to tighten up that half moon.
Does yours have that?

Booze Daily said:

The older version has a set screw in the movable jaw to tighten up that half moon.
Does yours have that?

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Yes and I have tightened it that is how you remove the jaw to clean it out and access the half mooned disc.

gundog said:

I have a pair of Kurt DX6 vises I use in my Sharp VMC. One of the vises has about .022" jaw lift when it has 4" stock clamped in the jaws. The other vise lifts maybe .002"or less. I have cleaned and adjusted them both no matter how I adjust this one vise it always lifts way too high.

Here is my setup I have some shop machined soft jaws 6061 T6 with a step milled in .210" deep. I mill the step in with the jaws clamped together. I give the jaws a wrap as I am tightening them with a dead blow hammer when I use them and also before I machine in the step. Left vise is fine but the right vise lifts too much.

I have checked my machine bed and the vise bed both are right on the money. I used a Tschorn probe to get my readings.

I have checked the half moon disc it is clear of chips and is greased. I have a call into Kurt but they are not going to get back to me until Monday and I have work I want to do.

Any suggestions are appreciated.

Click to expand...

.022 is alot. this can be caused by a few problems.

your problem is cutting the jaws, your doing it wrong!! NEVER clamp the 2 jaws together.

but do this 1st

1st thing I would do is take vice movable jaw completely off. take the screw out and the half moon out. clean it well including the threads for the tightening screw.
put a dab of geese in the moon then put it back together. move the handle back and forth while tightening the screw till its snug to turn jaw.

use a square stock jaw for a spider so to speak. clamp it the same as you would the part. cut the jaws and you should be fine.
Alwasy dry to clamp a spider so to speak as close to the same size as your part other wise if you have any wear in the base you will get lift at different lengths.
always tighten the screw so the movable is snug not tight in the area you are going to clamp as you may have movable jaw wear.
a tip on Jaws and clamping, if your jaws are not parallel and square to the movable jaw and fixed jaw your vise wont seat square when clamping on a part. same when using a spider so to speak it has to be square.
other thing is that could be happening if your endmill corner is nicked so the part is hitting on the inside corner of your step.

also order a few rebuild kits Mcmaster carr has them as well kurt. dont order generic non kurt ones they suck.

Delw said:

.022 is alot. this can be caused by a few problems.

your problem is cutting the jaws, your doing it wrong!! NEVER clamp the 2 jaws together.

but do this 1st

1st thing I would do is take vice movable jaw completely off. take the screw out and the half moon out. clean it well including the threads for the tightening screw.
put a dab of geese in the moon then put it back together. move the handle back and forth while tightening the screw till its snug to turn jaw.

use a square stock jaw for a spider so to speak. clamp it the same as you would the part. cut the jaws and you should be fine.
Alwasy dry to clamp a spider so to speak as close to the same size as your part other wise if you have any wear in the base you will get lift at different lengths.
always tighten the screw so the movable is snug not tight in the area you are going to clamp as you may have movable jaw wear.
a tip on Jaws and clamping, if your jaws are not parallel and square to the movable jaw and fixed jaw your vise wont seat square when clamping on a part. same when using a spider so to speak it has to be square.
other thing is that could be happening if your endmill corner is nicked so the part is hitting on the inside corner of your step.

Click to expand...

Thanks I will give this a try.

Kind of a takeoff on delw’s post, put a spacer between the jaws but put it high up just below the step depth. That should make the jaw lift, then cut it.
Don’t smack the part with a hammer.

Kinda hokey but should get you running til you get it fixed.

I did as you said and used some gauge blocks to space out the jaws and cut the step again.

Tore the vise down again wiped out all the old grease and blew it out again and put new grease on the half moon part. I can tighten that set screw as tight as I can get it more or less don't want to strip the threads I can still turn the vise handle with just a little resistance if I did that to the other vise you wouldn't be able to turn the handle.

I got the lift down to .0036" the other vise is now withing .001" this will work for now. I have another set of older D688 vises on my Trak bed mill I think I will swap them out for these I don't use the Trak very much anymore since I got this machine.

Thanks for all the help it got me going in the right direction.

I am curious what Kurt will say when I finally get a hold of them.

gundog said:

I did as you said and used some gauge blocks to space out the jaws and cut the step again.

Tore the vise down again wiped out all the old grease and blew it out again and put new grease on the half moon part. I can tighten that set screw as tight as I can get it more or less don't want to strip the threads I can still turn the vise handle with just a little resistance if I did that to the other vise you wouldn't be able to turn the handle.

I got the lift down to .0036" the other vise is now withing .001" this will work for now. I have another set of older D688 vises on my Trak bed mill I think I will swap them out for these I don't use the Trak very much anymore since I got this machine.

Thanks for all the help it got me going in the right direction.

I am curious what Kurt will say when I finally get a hold of them.

Click to expand...

if you cant tighten the threads down(with out a cheater bar) and you can still move the jaw back and forth you have one of 2 problems
your need to clean the thread better, Chase it with a tap etc, make sire your screw is clean and goes in all the way free freely.
or your half moon is worn out.

other thing to do is move the jaw back and tight screw see if that locks the jaw. try it in a few different places . also blue it up and hit it with a stone. that will tell that your bed is uneven.
if it is time for a dust up on a surface grinder.

check the movable jaw for burrs nicks etc etc hit it with a stone see if its even.

one thing to keep in mind if your soft Jaws are not parallel and square when you clamp them with the spider it will transfer, just like cutting lathe jaws the better your spider/ spacers are when cutting the jaws the better your jaws will be.

Hmmm, this thread makes me want to hold onto my 688's awhile longer. I have made and used many dozens of sets of soft jaws, and have never had a jaw lift problem. Many parts done this way had to be +/-.002" or so across the width of the part, and jaw lift has just not ever been a factor.

Maybe you are overtorquing the screw? I am pretty gentle with soft jaws, so as to not bow or crush the part.

Regards.

Mike

thats where I was going, the Kurt design should really preclude that much lift unless a a number of different things are going wrong, like cutting the step with the wrong preload and then over tightening, but its only happening on one of the two, so maybe one has some particular problem...look at them side by side, and they will tell you what it is.

If you can't lock the vise up with the setscrew, I'd be running a tap in there and looking to see if the pocket and divot for the half-ball is the same on both. Also if there's any evidence it's got interference on the angled face of the nut block not letting it slide down.

Dont know if thats actually a possible problem. I tossed my 675's on the shelf years ago after not being able to open them without a breaker bar after cleaning and greasing them to the best of my ability multiple times.

The versa-locks on my manual mill are fine, but they've never seen any coolant.

The CNC has one-locks, which have their own issues. The main ones being limited open capacity, and soft jaws are 'a bit' more trouble to make. My 'green' might take a good look at Orange next time around. If I live that long ...

Finegrain said:

Hmmm, this thread makes me want to hold onto my 688's awhile longer. I have made and used many dozens of sets of soft jaws, and have never had a jaw lift problem. Many parts done this way had to be +/-.002" or so across the width of the part, and jaw lift has just not ever been a factor.

Maybe you are overtorquing the screw? I am pretty gentle with soft jaws, so as to not bow or crush the part.

Regards.

Mike

Click to expand...

Mike
I have the older vises and the newer ones. I like the older ones better. If I get .001 jaw lift a bunch of my parts will be garbage due to tol and parallelism.
the newer ones mainly those bought in 2007-2010 have bearing issues as the hardened washers/ and the bearings suck. they went a cheaper route for a few years( tech guy at hurt told me) problem was my vises would stick when trying to open them. it was divots in the hardend washers. I have 2 very old ones that worked perfectly these were used when I got them in the early 90's and my employees would beat them with a dead blow to tighten parts, I did on occasion also back then.

I think it was last year or the year before I rebuilt all of them. 8 and have 2 more to go.
When I cut my jaws steps I always use a brand new endmill for finish, that way I have sharp corners.
I used to build all my own jaws up until 4-5 years ago 20-30 sets at a time. had one batch that I was building that the jaw lift was a little high on one vice I was using, which transfered into the jaws I was making. didnt notice it until I was setting up a job the vises that my jaws were lifting a part. a few thou. I was like WTF rebuilt the vise a few times honed all surfaces etc etc. still couldnt get it. popped some indicators on the vise and noticed the bar I was using for a spider was tappered as well as the vice jaws. thick at top and thin on bottom.like an upside down V between the 2 jaws. with the bar I was using it made it worse.
once I cleaned that up my jaws were dead nuts. less than .0005 lift and even pressure the hole 8" jaw length. all my jaws on my 6" vise are 8" long.

when I cut jaws I am now meticulous, jaws are square no burrs on back lapped on paper a few times. etc etc. if I have a problem its simple to find now. but now I also buy jaws because I use so many. really happy with the parallelism of monster jaws
jaw lift drove me up a wall for a number of years.

I talked to a guy at Kurt today and he told me they had some bad parts get out that the casting wasn't right on the nut he had me take pictures and sure enough what he told me to look for is bad on the vise that lifts real bad. The vise that is missing the paint is the bad one you can see the difference in the 2 vises. I sent them the pictures but it was late and there is a time change between our locations I will see what they say Monday.

Looks like it may be a simple fix to remove a bit more of the material where the paint is missing.

My guess halfway down this thread was going that the casting shown was too tall, or long, and hitting the inside of the moving jaw instead of the half moon washer. This is a location I didn't think of, but I'll bet it has the same effect.

I'm with Spruewell, if you relieve that area so that it properly clamps on the half moon disc instead of hitting there it'll probably stay down. Might be easier than waiting for the right part.

jccaclimber said:

My guess halfway down this thread was going that the casting shown was too tall, or long, and hitting the inside of the moving jaw instead of the half moon washer. This is a location I didn't think of, but I'll bet it has the same effect.

I'm with Spruewell, if you relieve that area so that it properly clamps on the half moon disc instead of hitting there it'll probably stay down. Might be easier than waiting for the right part.

Click to expand...

If you look at the pictures close you will see a section of the casting is missing compare the one picture to the other, the one with the missing paint the largest missing paint side is missing a big piece of the casting. The casting was made wrong.

gundog said:

If you look at the pictures close you will see a section of the casting is missing compare the one picture to the other, the one with the missing paint the largest missing paint side is missing a big piece of the casting. The casting was made wrong.

Click to expand...

You have interference/contact where you shouldn't. The distance from contact with the half moon portion to the area with missing paint is probably too short. The missing material where the paint is gone is if anything helping you, not hurting you. Take off a bit more material where the paint is missing and I'll bet it starts working again. Adding a shim (or flat washer) behind the half moon washer would probably fix the issue as well. I'm going to guess about 0.03" would do it, but it might take a bit more.

I suspect the area is missing paint because the part I'm pointing to (picture below) on the inside of the moving jaw is hitting it. If this is the case you could relieve the area on the moving jaw, relieve the area with the missing paint, or increase the distance to the half moon washer by putting a shim behind the flat side.

You could test this theory by assembling a good vise with the half moon washer removed and seeing if it displays the same symptoms (assuming it ends up touching there).

I got an email from Kurt they are replacing the nut under warranty. This shows how good a company they are. Every company has a problem now and then what matters is how that company responds to the problem. Thanks Kurt.

I don't buy anything new from Kurt. Last shop I worked at had bought several brand new Kurts and each and every one of the was EXTREMELY poor quality.

I've got a couple old D60's that are light years ahead in quality. Tighten up like a bank vault.

It is good to hear that Kurt stands behind their products. Maybe I should ask them why my 688 is a spongy POS.