Cylindrical squares or blocks

[tiptop]

It's been a while since I posted, been a little busy getting ready for class. Anyhow I stopped by my friends diesel shop on the way home today and found six nice wrist pins. They measure 5.25 tall, 2.375 od and a hole size of 1.125;
I checked them with my best square and they look right on. I will do a better evaluation when I get more time. In the mean time here are some pics. They are in my album at this location.

http://imageevent.com/aatiptop/toolspage/miscellaneoustools?n=0

Edited od measurement.

[johnhurd]

Must be a optical illusion that material looks thicker than .150 to me

[Chipslinger]

It's been a while since I posted, been a little busy getting ready for class. Anyhow I stopped by my friends diesel shop on the way home today and found six nice wrist pins. They measure 5.25 tall, 1.375 od and a hole size of 1.125;
I checked them with my best square and they look right on. I will do a better evaluation when I get more time. In the mean time here are some pics. They are in my album at this location.

http://imageevent.com/aatiptop/tools...neoustools?n=0

In reference to your Sig line, How is adrian doing?

[Lew Hartswick]

In reference to your Sig line, How is adrian doing?

Not Chipslinger but I check his BB once a day and he has been on his
boat a lot. pix of his kid etc.
...lew...

[lugnut]

John, I get .625 thick your eyes don't lie, just your math
Jay I think they would make great cylinder type squares. Looks like a great find.
Mel

[tiptop]

Mel, John was right, I had my numbers wrong. I went back and edited my original post instead of reposting. Yes i think they will work good. If they are off, I guess it would give me a reason to get the cylindrical grinder up and running. Jay

[Forrest Addy]

Wrist pins make good culinder squares if the ends are ground referencing from the OD. If you have a granite flat, a dial test indicator, and a dial test indicator you can check the actual squareness to as close as you can read the DTI. And no you don't set the gage from from a hard square. Squares are self checking if you know the trick.

For not enough to buy a coffee and brag rights lasting until your next aw-$hit, what it the surface gage trick for proving a square?

[TGTool]

Ah yes, nice trick. This came up awhile back so I'll let someone else go for the coffee this time.

Jan

[dave5605]

I could make a real nice ring roller with those wrist pins.

[tiptop]

I give

Forrest, I have to confess that after my hour long search, I have not come up with a better way to check a cylindrical type square. Now I know (and Have for years) how to check and set a carpenters square (since I was schooled as a pattern maker) but I do not know of a precise way to check a machinists square against itself. I do understand the game of threes and checking agaist each other. I am sure that the weekend after next you can enlighten me and 16 or 17 others. I can hardly wait. Unfortunately I am one of the home shop types that want to repair old broken down antique machine tools. This is what I like about my machine work and being semi-retired, I can do what I like and never make a dime and be happy just trying.
Yes dave5605, they would make a really nice ring roller, but I have one in progress already so I think I will continue with my origanal thought.

[Paul Alciatore]

The only method I know for self-checking a square is to place it against a straight edge and scribe a line with it. Then reverse it and scribe another line starting at the same point. If the lines diverge, the square is off.

But this method is not going to give you tenths, perhaps only accurate to a few thousanths. And it is limited by the straightness of the straight edge and the width of the area available for scribing the lines.

I am sure they can be compared with blocks or cylinders, but that is not self checking.

[Paul Alciatore]

OK, here is another way to check a square. Place the faceplate on the lathe. Place the square against the faceplate. Run the DI along the edge of the square using the longitudal feed on the lathe.

Now, rotate the faceplate and square 180 degrees, keeping the square in exactly the same position on the faceplate. Now run the DI along the SAME edge of the square.

The readings should all be zero, but that will not always be the case. If the readings match for each point along the square's edge then the square is good. Any differences will indicate an out of square condition. Remember that all readings must be taken in the same direction or sense. The DI will be reversed on the second pass so it may be necessary to reverse the readings on the second pass. Think front-to-rear = increased reading for both. Or rear-to-front for both.

Looking for matched readings will allow for any misalignment in the lathe spindle axis vs the ways.

But again, this is not self checking as you are using the lathe.

[lazlo]

The only method I know for self-checking a square is to place it against a straight edge and scribe a line with it.

To check a cylindrical square:

• Mount it on your mill table, and put a DTI in a Zero-Set holder in the spindle.
  
• Find the tangent at the bottom of the cylinder on one edge of the square by feeding the saddle in and out and finding the high spot.
  
• Preload the DTI, and wind the spindle/DTI from the bottom to the top. Measure the difference.
  
• Without touching the cylindrical square, spin the indicator holder to the opposite site (180° from where you were), find the high spot again and wind the spindle/DTI from the bottom to the top. Measure the difference.
  
• Now rotate the DTI holder 180° (back to where it was), rotate the cylinder 1/2 a turn and repeat the process.

From those three measurements, you can calculate the taper and lean of the cylindrical square with simple trig.

I scratch those numbers on the top of the cylindrical square, so I always know what I'm working with...

[Forrest Addy]

First of all I apologise for hijacking the thread but it seemed like a good opportunity to pass on some relevent info.

Here's how to prove a square.

Squares are self checking; you can use them to check themselves. The ways to do so come down to us from old metrology books and apprentice texts. It's old technology. An old fart taught me this particular trick back when and I've passed it on many times since then.

You need cylindrical square to test, a surface plate, a surface gage, and a dial test indicator (and clamps etc).

Naturally you have work clean and control heat input to the equipment.

The mast of the surface gage has a ball on it. Invert the mast so the ball is placed into into the "crotch" of the base barely clear of the surface plate so the mast inclined back at some angle that you will have to adjust to bring the DTI into position.

Mount the DTI on the upper part of the mast and adjust so the indicator ball is in a vertical plane over the mast ball and contacts the square under test just below the upper corner of the reference diameter.

Youve just made a gage. Bring the assembled surface gage to the square under test and contact the ball to the reference diameter. Adjust the DTI to a good zero.

With the assembled gage in contact with the square under test rotate the surface gage around a vertical axis a few degrees either way to maximize the reading. Refine the zero. This will take some careful fiddling. Be careful: the merest knock or nudge may disturb the setting.

Move to the opposite side of the square and take a reading rotating the gage to maxiimize DTI reading. Note any error. Return to the original side to check for repeat zero. If readings are equal on both sides of the square and you have determined by precious checks the square is a near perfect cylinder then the base of the square is perpencidular to the reference cylinder. The principle derives from the Euclidean proposition defining a cylinder as a rectangle rotated around one edge. The buisness with thesurfaceplate, surface gage, DTI etc takes advantage of it to quantify the truth of the square.

This procedure doubles the acual error so it is very accurate if well executed. If your indicator is in good shape and your readings are consistent, you can prove and quantify (if the cosine error is accounted for) to 1/10 the DTI's graduations. Check the square at a number of locations and make repeat zero checks between each. While the surface gage is set up check every square you own and make record of the error thus calibrating and proving what may have been mystery tooling to date.

This is sensitive work but well within the capability of a home shop owner exercising ordinary care.

[lazlo]

Hi Forrest,

With the assembled gage in contact with the square under test rotate the surface gage around a vertical axis a few degrees either way to maximize the reading. Refine the zero. This will take some careful fiddling. Be careful: the merest knock or nudge may disturb the setting.

Move to the opposite side of the square and take a reading rotating the gage to maxiimize DTI reading. Note any error. Return to the original side to check for repeat zero.

That's the process I described in the post above yours, which is basically a slightly more detailed version of Paul's second post (with an extra reading added to measure the lean)

If you use that method to take three readings that are spaced 90° apart, you can derive the taper and lean of the cylindrical gage. Say the first measurement was D1, and the second measurement 180° opposite was D2:

Taper = (D1 + D2) / 2

Now the third reading, with the cylinder rotated and the DTI back at the start is D3:

Lean = [(D2 - Taper) - (D3 - Taper)] / 2

Cheers,

Robert