Checking Flatness

[Neil Jones]

I've been using the corners of three 1-2-3 blocks set on my surface plate to check the angle plate I'm trying to grind flat and square. I tried to use 3 jack stands that have points but the adjustment is too coarse. What do others use to check for flatness?

[Tobias-B]

would 'parallels' be too easy an answer?

I've used several on the plate to check a plane with
a protruding feature before. It's not the most precise,
but it works fine for things like car bellhousings...

t

[lakeside53]

Can't you just sweep it with an indicator on a suitable ground base. I do on my surface table...

[Rustybolt]

Check with Evan. He had a way of checking flaness using a laser.

[Neil Jones]

"would 'parallels' be too easy an answer?"

Yes, because I'm looking for just a small point of contact in three places.

"It's not the most precise, but it works fine for things like car bellhousings..."

I need to be precise. Surprised others haven't commented as I would think this is a common situation for many machinists.

[LES A W HARRIS]

I've been using the corners of three 1-2-3 blocks set on my surface plate to check the angle plate I'm trying to grind flat and square. I tried to use 3 jack stands that have points but the adjustment is too coarse. What do others use to check for flatness?

Some thing along these lines may help.
Plane established with three 0.7500" dia balls.









Sleeves made of 1" dia delrin, snap over ball, to keep from rolling too much on table.
Vee blocks keep stock from rolling around.

As you are grinding angle plates, Blue the surface?

Cheers,

[tony ennis]

Yes, because I'm looking for just a small point of contact in three places.

Heh, 'use ball bearings' was a drop-dead obvious answer.

Less obvious was putting them in those little sleeves, which is clever.

[dp]

You can drop them into a washer, too. So long as they don't roll away while you're using them any retainer will work. But I really like the plastic tubes.

[Paul Alciatore]

I would think ball bearings would also work well. As for 1-2-3 blocks, they come in matched pairs, but the third one may be off by quite a bit unless you carefully select it.

[Mcgyver]

neat idea Wes