How do I indicate in something SQUARE?

[ErichKeane]

Huh, looks like Keith Rucker just released this video this morning!

Watching now, but maybe it'll tell me the secret

 

[ErichKeane]

Well shoot, he uses his magic precision-ground square from Solid Rock Machine Shop again. So not much help on the setup.

 

[Cadillac]

You need a trusted square, cube,or block to do this without a lot of indicating and trial/error. Also need a cylinder square to set your indicator to check for squareness after being ground. Of course their are other ways.
A grinders column should be pretty dam square to the machine. Grinding both surfaces in one setup should get you pretty close. Or at least you’ll see how square your column is.

 

[WCraig]

You need a trusted square, cube,or block to do this without a lot of indicating and trial/error. Also need a cylinder square to set your indicator to check for squareness after being ground. ...

The Tom Lipton video I linked to talks about determining square from a block that is close to square. The sides do need to be parallel but that is relatively easy to do with a surface grinder. He uses a tenths indicator to check for parallel and then by flipping the block you can measure the amount that it is non-square. And thus splitting the difference shows the amount it is out of square. Kind of an 'Aha' moment if you watch the video. At least, it was for me.

Craig

 

[RJSakowski]

I always love listening to these true/flat/square conversations. There are so many nuances. Almost all start with "find a true flat surface you can trust", and work from there. I pity the poor fellah, back over a hundred years ago, who had to achieve this without the benefit of modern tools (and ultra-high quality references). What shop tools he used, had far less precise bearings in the head of his equipment. I suspect there was a lot of hand working of the metal after the last machine tool took it's final pass.

It is an interesting problem. There used to be a game show, if you can call it that, where contestants were on an island and teams of two were given various tasks to complete, using whatever resources they found on the island.. Tasks were like make an accurate map of the island. etc. The contestants did surprisingly well, considering their makeshift tools.

Making a straight edge or a square are simple tasks, being accomplished from geometric principles. Making accurate straight edges or squares are more difficult. Making instruments with high degree of accuracy is much more difficult. As has been previously pointed out, it is possible to make a flat surface without the benefit of any modern metrology tools. Once a flat surface is available, it is possible to make a straight edge without the metrology tools. Making a square is a matter of bisecting an 180º angle Two squares, along with a straight edge can be checked for squareness visually within a few thousandths of an inch. which was probably sufficient for most practical reasons.

There is evidence that these techniques were known in antiquity. Any further precision would require more sophisticated metrological instruments. The invention of the micrometer occurred in the eighteenth century, along with the movement to standardize measurements. Optical methods came about near the end of the nineteenth century that would allow measurements to a tenth of a micron or 4 microinches.

 

[ErichKeane]

So I've decided that grinding/indicating in these two is much harder than just doing a cube, so I'm going to make one of those fancy reference squares.

I have this big scrap block of A36 that I'm going to rough out on my shaper and try to do about a 5.75*5.75*2 setup block I can use to do this.

This is a big round I used for a lathe chuck adapter plate at one point but never used the rest. It's a touch over 8" round and 2.5 thick.I probably should have started by squaring up one side on the lathe, but instead did it on the shaper in a pretty error prone setup. I didn't hold it tight enough the 1st time (despite flatting the copper wire a ton!), and had some troubles with the step over, but on the last pass with the 1st side right now!

 

[Shootymacshootface]

So I've decided that grinding/indicating in these two is much harder than just doing a cube, so I'm going to make one of those fancy reference squares.

I have this big scrap block of A36 that I'm going to rough out on my shaper and try to do about a 5.75*5.75*2 setup block I can use to do this.

This is a big round I used for a lathe chuck adapter plate at one point but never used the rest. It's a touch over 8" round and 2.5 thick.I probably should have started by squaring up one side on the lathe, but instead did it on the shaper in a pretty error prone setup. I didn't hold it tight enough the 1st time (despite flatting the copper wire a ton!), and had some troubles with the step over, but on the last pass with the 1st side right now!

That is really sweet!

 

[ErichKeane]

A little more progress today, but probably it! I finished the shaping of 1 side which appears really smooth and flat.

I blued up the opposite side and tried to come up with a way to lay it out, but couldn't come up with one. Instead, I just popped it into the bandsaw 4x to square it up

I'll spend a bit of time in the shaper creating the first 2 90 degree sides because I'm sure my bandsaw isn't close, but a bit of shaping my next time in the shop should get me pretty well roughed out.

 

[ErichKeane]

A little more progress today! I started by putting my "best" bandsaw side down, which was pretty out of wack. I finished a few cuts along that "top" to have as square of a side as I could get.

Annoyingly, as soon as I was ready for my last cut, my electric power feed stopped working! So I spent most of today working to fix that. Turns out someone in the machine's past replaced a 3" key with a 1" key that had a hole drilled down the middle!

There wasn't any set screw or anything that it could have been for, so I'm guessing they used something from a drawer! The key ended up breaking into 2 pieces where the hole was drilled and each piece apparently walked themselves out and all I got was a whirr sound when using my power feed. A trip to Ace for key stock and some replacement bolts (swapped SHCS for hex, since there wasn't enough room around the motor to get to the heads!) and we were back in business.

Flipped the block over and hung it off the side of the vise. The idea is I should be able to use my up/down feed to cut the other side as well to get a 90.

Hopefully ill get much further tomorrow

 

[ErichKeane]

I had time to do one of the 90 degree sides foday, and it went really wrong I wasn't able to get a good grind on the tool considering the angle to the holder (it's just a lathe tool), so it kept digging in.

I managed to get a grind that did decently though, and got all but that top corner cleaned up.

Measuring with a square, the too corner is about as square as I'd think is possible, though the vise is apparently not perfectly trammed. I counted on that anyway, so the idea of this cut is to have a reference surface for the opposite side so I can cut it facing up, and I'll flip it 1x more to recut this side up.

So, SOME progress .