Keeping parallels snug in a Kurt Vise

[PhoenixMetal]

I just bought a brand new Kurt D688 vise, and when I put a workpiece in using parallels and tighten the vise, the parallels become loose enough to slide out. I have been removing the parallels at that point so they don't fall out.

I'm new to machining, but I get the idea that the parallels are supposed to stay in during machining, and that they're supposed to stay snug.

The vise came with two little o-rings and some cryptic instructions that say that the o-rings are for use with parallels and that they will help create downward pressure onto the parallels. Here is a link to those instructions.

Their o-ring instructions and diagrams are terrible and I can't understand what I'm supposed to do... Am I supposed to disassemble the vise before putting the o-rings in? And if so, what is the procedure? Of course I could figure out how to take the vise apart on my own, but before I mess with it, I'd like to know whether I really need to do this.

Also, where is that adjustment screw they're talking about? Is it accessible from the rear of the moving jaw or is it hidden behind the jaw plate?

Kurt may have a reputation for making a good product, but they sure are remiss in not providing any instructions (in the box or on their website) for how to use and adjust their product. That's just really not acceptable in my opinion.

Anyhow, does anybody have any experience with using these o-rings?

Thanks!

[One of Many]

The set screw is on the rear face of the moving jaw pointed at you. Right in the center. This set screw pushes the moving jaw back so that the ball swivel is pulled/seated into the ball socket. The ball swivel joint in combination with the wedge on the screw casting is what gives the moving jaw its pull down action. Just loosen this set screw a ways to remove the moving jaw. Remeber to grease the swivel with a dab of moly grease, first to keep it from fretting and second to keep the swivel in the seat while putting it back together. The set screw should not be tightened. Just snug and back off a wee bit, so the swivel can still move. The intructions advise to tighten the set screw so that a .002 feeler gage will just slip under the moving jaw.

The purpose of the O-rings is like a spring under the moving jaw. They lift it up when the vice is unclamped leaving a .002 gap under the moving jaw. Supposedly as you clamp a work piece, the jaw pulls the work piece down onto the parallels.

IMHO that is what a deadblow hammer is for. To tap the part solid, seating the work piece down onto the parallels. I wouldn't trust anything to cut parallel, square or otherwise without seating the part manually.

Secondarily, if there is an open gap under the moving jaw, it can and will collect crud under it, thereby when the jaw does pull down, it is also seating on crud. There goes the parallelism between the jaw faces and additional wear from that crude lapping those surfaces.

Simplistic solution at first glance, but impractical in use!



DC

[Geof]

Some people will probably be horrified at the thought of doing this; hold the part down with the spindle while you tighten the vise.

I have used a tool holder with a piece of Delrin plastic in it that is tapered down to about 0.3" dia at the end. You just tighten the vise up to grip the part and then slightly loosen it, then bring the Delrin down until it is just touching with a bit of pressure and fully tighten the vise.

[One of Many]

Originally Posted by Geof Some people will probably be horrified at the thought of doing this; hold the part down with the spindle while you tighten the vise.

G-code a pattern and some Z rapids to thunk it in place against the parallels!

Now I'd have to admit I have used the quill on mine similarly in setup. I have also used the Z on others (without a quill) as a press to hold a large spring down while installing a C-clip.

DC

[Geof]

Originally Posted by One of Many G-code a pattern and some Z rapids to thunk it in place against the parallels! ....DC

This I have done unintentionally.

[ckirchen]

A urethane pad also works. The 'overtravel' provided by the flexing of the pad would eliminate most of the risk of moving the quill down too far or fast on a CNC.

Chris Kirchen

[PhoenixMetal]

Thanks guys - thanks for the advice. I think I'll try seating the part onto the parallels with a rubber mallet next time. I definitely don't want to use the z axis to hold the part down because that just doesn't sound healthy for the machine. I have tried pushing the part down with my hand while tightening (which didn't help), so I wonder whether the z-axis trick would work anyway.

[MachEng]

We use a rubber band around each jaw to keep them in place.
It works great.

[One of Many]

Originally Posted by MachEng We use a rubber band around each jaw to keep them in place. It works great.

The specific issue here was that the parts were not actually seated to the parallels when clamping. Loose parallels were the indication as a result.

Using something to retain them would keep the parallels from floating around, but it won't help in seating the part against them. We used stock compression springs, old sections of bandsaw blades(teeth ground off) or that black metal banding strap, bent into a Z shape as a spring between the parallels to retain them. Double back tape can also work. Never thought about rubber bands I guess. Either that or the shop owner was too cheap to buy them when there was plenty of free scrap around to fit the need.

DC

[mc-motorsports]

Use your parallels like a flatness gauge, if you can slide them out, your part isn't sitting flat.

Kurt vices are about as good as it gets. Your right, the instructions weren't very clear, but you got what you paid for, a quality machined precision vice that should last longer than your machine.

[carbidecraters]

Originally Posted by Geof Some people will probably be horrified at the thought of doing this; hold the part down with the spindle while you tighten the vise. I have used a tool holder with a piece of Delrin plastic in it that is tapered down to about 0.3" dia at the end. You just tighten the vise up to grip the part and then slightly loosen it, then bring the Delrin down until it is just touching with a bit of pressure and fully tighten the vise.

I am officially horrified!

Havent you guys heard of dead blow hammers?

[Geof]

Originally Posted by carbidecraters I am officially horrified! Havent you guys heard of dead blow hammers?

Sure I have; I also know there is absolutely no risk to the machine doing what I describe.