Squareness comparator/surface guage

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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.

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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But more progress. The slide clamp is pretty much done with the exception of the slit and the tapped holes for the piece of spring steel on the bottom.

My lathe is currently down. My DC motor drive died. In the process of trying to repair it, but my lathe is dead in the water for the time being. Which sucks, cause there's a few lathe steps I need to do.

For the post, it's 5/8" stainless. I couldn't find drill rod at the local shop and I wasn't going to bug them to cut something. I can usually find everything I need on the cut off racks.
Anyways. The hole in the base is 1/2", I plan to turn a shoulder on the bottom of the post to fit into the 1/2" hole and bolt it from underneath the base.
I also need to throw together a quick slitting saw arbor for my slitting saw so I can cut the clamping slot. Once im happy with the slide clamp I'll move on to the DTI holder. Then made the squareness comparator nose once I know the stick out of the DTI over the base.
Looks great !!
Building one is on my LONG list of things to do.
Is there a reson the radius isn't machined directly into the base?

I guess two reasons, now that you've made me think about it.

One, that's not how Stefan Gotteswinter did it, and I've been using his as a reference. He hardened his, I will probably try the same.

Second, I did not know how far the DTI will stick out. I'll need to basically complete the whole thing in order to know how long I need to make the radius nose. The DTI holder will have a fine adjust, but not an adjustment for length or angle. So determining the stick out would be difficult. I would have had to draw this up, do a mock up, and work from my drawing... And we'll, frankly, that's a lot of thinking. I tend to think on my feet...
Nice looking work !
Thats on my project list as well.
A front radius of large diameter and perhaps removable.
The indicator needs to be centered so the post must be offset or indicator holders made for the project.
I like a centered post so will have to build holders for my indicators.
The post should be able to lean forward and back with a fine adjustment to accommodate and set the indicator or be on a dovetail slide with a adjustable gib or with a solid lock.
It should be a heavy item or at least twice the weight of my current surface gauge.
Well that's the design thoughts I've had so far. Most of my projects are still just dreams.
At this time I'm working to get my machines and components in reasonable condition so I can do some decent work.
All the adjustments and fine tune will be in the dove tail piece. If you look at Stefan's picture up top, you can see a thumb screw just behind the indicator. That is the fine adjustment. The dovetail and the slide clamp are connected with a small piece of spring steel. The thumb screw pushes against a ball bearing pressed into the dovetail piece and ground flat so it's a nice smooth operation. Also, the bottom of the base has 4 ball bearings pressed in and ground flat. No wobble, slides nicely, yet sturdy.
I was in a pinch at a shop and just used a round drop made of drill rod about 3" in diameter and mounted a mag base and indicator on it and it worked slick. Also if you own a Starrett Surface gage that has a V in the front and the indicator rod has a small ball on the end, that too can be used. I have also seen someone grind a flat spot on a 1" ball bearing and it fit flat down in the Starrett Height gage V.
Finally made some more progress on this thing, now that my lathe is up and running again. I have the slit cut in the post clamp done and a thumb screw in. That thumb screw will probably be temporary as its too short. Its too close to the clamp. But progress none the less

I also need to redo the feet on the bottom of the base. I did a v groove but changed my mind and pressed in ball bearings and ground them down but one got hot and came out.

I like this screw a lot better.
I cleaned up the seat that presses against the clamp body as best I could, but it's still just metal on metal rubbing.
When tightening and loosening, you can feel friction. I'm worried about galling over time. If I harden one (or both) of the pieces, would that help them slide against each other better?
The steel is 01.

(Also, is it *zero* one? Or the letter O one?)
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.
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.

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!
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.


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)
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?
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?

I will also be doing the radius on the front for the squareness, then swing the indicator around the post to the back side for the surface guage.
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I'll give that a watch when I have some time this evening.
But, do you not think my positioning would work for both squareness and flatness?
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