Squareness comparator/surface guage

Started this a while ago, keeps getting out on the back burner due to shop problems and break downs. Still working on my lathe DC drive system that failed...

It's based on Stefan Gotteswinter's project. Did a bunch more mill work last night on the top slide piece.
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And my progress so far. IMG_20180221_010118.jpg

To use as a surface guage, I can just spin the top slide around to the back and extend the DTI off the back for about 4" of reach. Not a huge amount of surface covered, but more than I have right now, which is nothing, and my surface plate is small.
I figured with the addition of the surface grinder, and my hopes of making lapping plates, I really need a way to measure squareness and surfaces.

It would be nice to afford a nice reference standard tho. I may just have to rely on comparative squaring. Checking both sides of something and splitting the difference.
 
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H
Correction. The clamp body is 01, the screw is an old mt3-jt3 arbor, which means, I have no idea what it is. Might have been case hardened, might have been totally hardened. Didn't turn terribly with carbide. Its tough, but machines reasonably.
 
H
It is Oh 1. Letter O. Stands for Oil Hardening tool steel.
Put a dab of grease on the rubbing surfaces.
Cut a small washer out of brass and use a dab of grease.
IMG_20180408_230840.jpg

The lip left over was a happy happenstance of the parting tool. Fits perfectly inside the hole. I'll call it a guidance bushing... Yeah!
 
H
More more.

Finished the indicator holder/clamp.
Messed the dovetail up a bit. Couldn't get the clearance angles right on the grind, I used an old no. 2 center drill. Its a little wide and requires a few turns of the cap screw to snug it up. I was hoping to use a thumb screw for this part too, but you have to crank it too hard to close it up. Bummer. But, the idea would be to have a dedicated indicator for this stand. So, shouldn't matter much.

IMG_20180409_234329.jpgIMG_20180409_234343.jpgIMG_20180409_234405.jpgIMG_20180409_234432.jpg

I have to order some small cap screws and figure out what I want to use to join the indicator holder to the body. Stefan used spring steel. I don't have any spring steel. And such a small piece isn't worth buying stock. I have some various shim material that goes quite thick in various metals, also some other mystery sheet metals. I'll have to find something that is springy, but not too hard or soft.

Coming along.
 
I would suggest if your going to use that sort of indicator you use a steeper angle and that type doesn't read so good that way. A plunger indicator would work better that way (vertical)
 
H
Hi Richard.
What do you mean it wont read well? If I push the needle over so it's more horizontal/parallel to the work spriface, shouldn't it read okay? Could you please explain more?

Also, the indicator was just propped up on the ledge of the clamp body. The two pieces are not screwed together yet.
 
If your measuring squareness on the side of a square or angle block that method is good, but the way you have it with stem sitting on the bottom in a almost vertical position it isn't the way that style of indicator is designed to be used.
 
The gage Stefan made is used to test squareness and not a height gage. See the curved front or are you planning on milling a slot in yours to sweep with?
 
H
Ok, you’re right. But on my mitioyo indicator, I can push the stem to move it’s position. If I push the stem closer to the face, almost parallel to a horizontal work surface, would it not measure fine on a horizontal plane? I apologize, maybe I’m missing something why that wouldn’t work alright?

IMG_20180411_065323.jpg
 
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