Thread: How can I touch up V blocks?

Instead of shimming, step grind them.

Originally Posted by Michael G

I have a a couple of pairs of V blocks acquired over the years and now that my grinder is operational, I'd like to true them up a little. Putting a piece of ground rod in the V, I can measure both ends with the height gauge and while one is passable (5/10ths difference), a couple are 2 thou difference. (I discovered the error because I tried grinding using the inaccurate V and couldn't work out why I was 2 thou out over the length of the part).

I've racked my brains but can't think of a good way to hold/ support the blocks on the mag chuck so I can get the 2 thou blocks closer to the 5/10th block. The best I can think of is get the 5/10th block, flip it over and shim the high end by 5/10th , take a lick off the base and that should then be spot on. Using that one, nest a 2 thou block in the V and grind the sides of the V which then should take that V back to spot on.
Anyone got any thoughts on that or a better plan?

Michael

Hi Michael,

Can you do a drawing showing which way they are out.. is it the V, or is it the base?

Do you know about step grinding? Phil explained it to me once.. you work out which way you want to go, and take a lick off, leaving a strip along one edge, so that acts like a shim when you flip it over. So you can effectively get the shim sizes down to the resolution of the grinder..

Ray

PS.. Speed typist PeteF beat me to it..

Originally Posted by RayG

Which way they are out.. is it the V, or is it the base?

The primary concern is that the V is not parallel to the base.
Yes, step grinding would certainly be easier than trying to find some 5/10th shim.
So the sequence would be -

• Grind the base of the block across leaving a step on the high side
• Flip the block up the right way and grind the tops of the V - at this stage the V should be parallel with the chuck and the tops parallel with the V
• Turn the block over and grind the base parallel with the V / top surface.

Sounds like a plan. Now all I need is a little time...

Michael

Originally Posted by Michael G

The primary concern is that the V is not parallel to the base.
Yes, step grinding would certainly be easier than trying to find some 5/10th shim.
So the sequence would be -

• Grind the base of the block across leaving a step on the high side
• Flip the block up the right way and grind the tops of the V - at this stage the V should be parallel with the chuck and the tops parallel with the V
• Turn the block over and grind the base parallel with the V / top surface.

Sounds like a plan. Now all I need is a little time...

Michael

You don't have to go to work tomorrow, do it then.
Kryn

Michael I have to do this at tafe in the next few weeks.

Originally Posted by welder

Michael I have to do this at tafe in the next few weeks.

I'll send my blocks across shall I?


Meanwhile I made an error in my summary and none of you guys picked it. The step needs to be ground so the high bit is on the low end of the lock - otherwise you double your error (I think)

Michael

(PS didn't get to it today - MIL had a lamp that needed to be fixed. 1/2" x 26tpi...)

Michael I may have misunderstood what you said, but it sounded backward to me.

Say the V of the block is sloping up. You'd leave the step at the highest point of the V. So if the V was across the chuck, with it sloping up toward the back, the step is left on the back. I find the easiest way to remember it is to think about where I need to remove material.

Of course the challenge is to fit it under the grinder, a challenge I'm currently losing with what I thought was going to be a "quick little job" .

Pete

Originally Posted by Michael G

I have a a couple of pairs of V blocks acquired over the years and now that my grinder is operational, I'd like to true them up a little. Putting a piece of ground rod in the V, I can measure both ends with the height gauge and while one is passable (5/10ths difference), a couple are 2 thou difference. (I discovered the error because I tried grinding using the inaccurate V and couldn't work out why I was 2 thou out over the length of the part).

I've racked my brains but can't think of a good way to hold/ support the blocks on the mag chuck so I can get the 2 thou blocks closer to the 5/10th block. The best I can think of is get the 5/10th block, flip it over and shim the high end by 5/10th , take a lick off the base and that should then be spot on. Using that one, nest a 2 thou block in the V and grind the sides of the V which then should take that V back to spot on.
Anyone got any thoughts on that or a better plan?

Michael

Michael, as a suggestion, if your V blocks have clamping grooves on the side, would it be possible to lay the V block upside down on a piece of round machined bar, possibly laying in a T slot, clamp the block so that it is level across then grind the base? Not knowing much about machining, this would be my thoughts on doing it this way, as the V is resting on the bar, therefore it would have to be square/parallel to the base.
Your comments on this idea please?
Kryn

Originally Posted by Pete F

Say the V of the block is sloping up. You'd leave the step at the highest point of the V. So if the V was across the chuck, with it sloping up toward the back, the step is left on the back. I find the easiest way to remember it is to think about where I need to remove material.

We may be talking at cross purposes here (probably) but the material needs to be left on the end of the block that is low so that when the block is flipped over the V sits level. I guess it depends whether you call the step the piece of material left on or the piece of material removed.
Regardless, we have the basic idea.

Originally Posted by KBs PensNmore

If your V blocks have clamping grooves on the side, would it be possible to lay the V block upside down on a piece of round machined bar, possibly laying in a T slot, clamp the block so that it is level across then grind the base? Not knowing much about machining, this would be my thoughts on doing it this way, as the V is resting on the bar, therefore it would have to be square/parallel to the base.

My V blocks don't have clamping groves in them but what you suggest is what I'd prefer to be able to do as that way everything is lined up around the centre line of the V. The closest I can think of is inverting the v over a rod in a vice so the vice clamps the sides while the rod provides the level.

On that divergent thought, what is the preferred vice type for a mag chuck? I would have thought one of those toolmaker's vices with a SHCS screwing into a bar through the base. Any other thoughts?

Michael

I have a pair of those Michael, i find them really handy. For bigger stuff i have used my 5" glacern and vertex on the grinder, but for most work the little SHCS type are fine. The main thing is that the sides are square to the base so they can be put on their sides to grind ends square.

Ew

One of the fitters at work is actually a full blown toolmaker (but who makes tools in Australia these days?). He did his apprenticeship with Hills, back in the days when they made lots of stuff in Australia...
Anyway - I had a nagging thought that I had some plans for a tool maker's vice and sure enough in the collection of apprentice projects he gave me...

Toolmaker's vice.pdf

Probably doesn't need to be as big for me but people may find it interesting to see what apprentices were expected to produce.

Michael

Originally Posted by Michael G

On that divergent thought, what is the preferred vice type for a mag chuck? I would have thought one of those toolmaker's vices with a SHCS screwing into a bar through the base. Any other thoughts?

Michael

That's the type we use most often, but custom mag transfer blocks and jigs are usually involved as well.

Thanks for that PDF, there is one thing that I don't understand about that, and that is there are two holes, one either side, one is 17mm in, and the other is 18mm in... why would they be different?

Ray

Originally Posted by RayG

and that is there are two holes, one either side, one is 17mm in, and the other is 18mm in... why would they be different?

If I'm looking at the same numbers?? 17mm to the holes. 18mm to the end of the slot

Stuart

Originally Posted by Stustoys

If I'm looking at the same numbers?? 17mm to the holes. 18mm to the end of the slot

Stuart

Yep, got it.. good to know the superpowers are still intact... ( although that one was pretty easy )

Ray