Which Milling Vice

[JasonBModerator @jasonb]

To square up a block of stock the rear fixed jaw is the ref surface so the bottom of the vice should not come into it.

 

Machine first face No1

Then rotate so face No1 is against fixed jaw and machine No2.

If fixed jaw is true the corner between N01 and N02 will be 90deg

[Nicholas FarrParticipant @nicholasfarr14254]

Hi JasonB, yes I’m aware of that procedure, however, my back jaw is square to the bottom of the vice, the accuracy test for these vices gives a parallelism of 0.03mm on a length of 100mm, between the bottom of the vice, and the base, and a perpendicularity of 0.05mm on a length of 100mm of both jaws to the bottom of the vice, therefore, if the back jaw is square to the bottom of the vice, the bottom of the vice needs to be parallel to the base, and that would make the back jaw perpendicular to the base.

Regards Nick.

[JasonBModerator @jasonb]

The gap that can be seen at the bottom of the workpiece suggest base is flat and work sis being raised off the bed near the moving jaw as it is pushed back against the wonky rear jaw

 

[David DeavilleParticipant @daviddeaville66164]

After all the testing and advice today I have just ordered a ARC Versatile Milling Vice 100mm, will get back to you with my findings.

Thanks All

Dave.

[ChrisLHParticipant @chrislh]

The rather light table on my Dore-Westbury milling machine together with a not particularly rigid vice means that, although everything is square initially, the whole assembly deflects under the load due to tightening the vice. Nothing machined in this set up is ever square ! I always get a reminder as the X travel becomes rather stiff.

[Howard LewisParticipant @howardlewis46836]

My firstb thought was ” What is the reading across the table of the mill?” If the mill is out of tram, readings on the vice will show out of square.

Once the vice is on the table, with both surfaces clean, then the vice can be checked.

The vice should be aligned so that the fixed jaw is parallel to the axis over which the table moves.

I made up a goalpost arrengement for rapid aliugnment, rather than spending time clocking and tapping to and fro. The two pillars are turned to be a snug fit in the T slot on the mill table..

A horizontal bar is fixed between the upright pillars (To endure consistent location, I Vee’d the cross bar)

The pillars are secured to the table by long M8 bolts passing into T nuts, taking care that the bolts do not protrude below the t nuts.

Once secured in place, a light ciut is taken along each side of the cross bar. When clmped to this, the fixed jaw is parallel to the line of motion of the table.

With this arrangement, my K4 vice will reallign within 0.025 mm

If the face to which the fixed jaw is secured shows no vertical misalignment, then check that the surfaces of the jaw are: square to each other.  And that the vertical faces are parallel.

Fix the jaw in place (Ensure that there is no interference between the lower corner of the jaw and the corner of the vice body.

If need be, undercut the horizontal surface of the vice to ensure this, even if it means using a hacksaw and a file. make sure that everything is clean, no swarf anywhere!

Hopefully, after all this, the face of the fixed jaw will be verical.  If it not  the reaason needs to be found and rectified.

If the jaw faces  are not parallel, being hardened, thay will be difficult to correct in a home workshop.

For this you mwould need a surface grinder, to just clean up one face.

If the narrow lower face is not square to the clamping face, the base of the vice could be undercut, to just clear the jaw, or machined all over, to ensure parallelism to the mill table.

HTH

Howard

[David Deaville]

On 3 April 2024 at 13:30 David Deaville Said:

Hi,

 

‘Snip’

 

When I bolt work directly to the table it comes out precisely square, so it is the vice that has the error in it and not the Mill.

 

Thanks

Dave D.

All the replies and comments do not alter the fact that you ‘nailed’ the problem in your original post.

Several things come to mind.

• Running a DTI up/down on the fixed jaw will tell you how square the jaw is but it relies on knowing that the vertical travel (whether its the quill or column) is perpendicular to the table surface.
• Above assumes the jaw thickness is parallel, but it could be removed and the DTI run on the body face.
• If we assume the mill is tramming correctly and the jaw seating face shows its out of square, then the DTI tip should be traversed over the top flat surface of the vice ‘ways’ to if there is any height variation which would indicate that the base of the vice is not parallel to its ways
• Mention was made earlier in this thread of the jaws and mounting surfaces being ‘cleaned up’. If the base of the vice is parallel then a quick fix would be to ‘clean up’ the surface of the fixed jaw recess with the side of an endmill, then put the jaw back on.
• Above does not negate the obvious solution of returning the vice to the supplier if as it seems it is out of spec.

Ian P

[PeteParticipant @pete41194]

The very first thing I’d do is put that same tall part back in the vise and lightly tighten the moving vise jaw against it, just enough that part can’t be moved using a bit of hand pressure. Then use a dial indicator with it’s tip touching and the dial zeroed close to the top rear side of that block. Then start tightening the vise to your usual torque on the vise handle. Milling vises and even including the genuine Kurt vises ALL have a degree of flex and deflection in that rear jaw, and enough to slightly bend the vise bed when that tightening pressure goes high enough. 6″ Kurt vises are capable of exerting up to 7,000+ pounds of closing force with well supported and heavy parts. I’d suggest the vise in that picture and it’s rear jaw are a whole lot less rigid than any of those Kurt’s. That deflection is well known, and with cnc and volume part production, a lot of companies will use a proper torque wrench each time so the vise deflects to the same known position so it can be compensated for.

Checking if there’s any inaccuracy in the machining and grinding of that fixed jaw by running an indicator up and down it is a good first step. But it’s only a static test without any of the loads the vise will see as it’s tightened. There’s some very expensive industrial level milling vises built with the vise bed and rear fixed jaw cut, machined and ground from a single piece of Durabar cast iron for that exact reason.Some are also built to standard Bridgeport tee slot pitch dimensions and will use 3 cap head screws on each side and through the vise bed so the vise is then held down at 6 points to help stiffen the vise bed even more against that bed deflection.

One way around that very high cost for those industrial level vises and for most of the smaller parts were using milling vises for is to use what are known as precision, toolmaker or grinding vises. Most that I know of are also built with the vise bed and rear jaw as one single piece of hardened tool steel. And even the off shore one’s are almost always ground to far better dimensional accuracy in all 3 dimensions than even a Kurt vise is. Or at least all 3 of mine have been. My largest can open up to around 4″ wide and it’s extremely accurate. It also cost about 1/4 of what my 6″ Glacern milling vise did. For anyone thinking about a vise of this type, just be sure whichever one your looking at buying does have proper clamping slots at both ends and on both sides. Not all of them do. And you can increase there rigidity even more by using hold down clamps along each side and in as many tee slots as your mill table has to fixture the vise in place.

[Nicholas FarrParticipant @nicholasfarr14254]

Hi, well if he has got 0.1mm difference on a 1″ jaw, from the top of the jaw to the bottom, with a maximum run out of 0.05mm over 100 perpendicularity, as per the accuracy figures, that really is a wonky jaw, whatever the cause is.

Regards Nick.

[PeteParticipant @pete41194]

It depends on which direction that fixed jaw is tilted. Some are ground with the top of the fixed jaw leaning towards the moving jaw by a few thou in an effort at some compensation for that rearward deflection. I believe the Vertex clones of the Kurt vise are or at least were done in that way.

[HuubParticipant @huub]

I have the same vice as in the pictures (brand: Saba). The vice wasn’t square at all. I removed the vice jaws, tightened the gibs (screws on the bottom), placed a 20 mm 4 flute end mill and milled the faces square. That only took a light cut.
The second problem was a difference in height between left and right of 0.04 mm. I solved it by making my own parallels from mild steel. I marked the right edge of the parallels so they can be placed back in the same position as they were made.
Now the vice is pretty accurate.

 

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