Square centres

This is from my Audel’s “Progressive Machinist” c.1913 — it suggests the square centre is to be used more for correcting an inaccurately placed centre hole on the work rather than driving the work. At least if I’m reading correctly...

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-frank
 
Bob Korves said:
Winging it here... I suppose a different kind of dog might be used to turn the work using a radially mounted but axially oriented hole or two in the end of the shaft, using pins to drive the work without defacing the OD of the shaft. There would be an axial hole or two in the work. A 60 degree center would also be used as part of the tool to center the work, small diameter and used as shallow as appropriate. The tool would have to be shop made, but with mild steel it would be easy to machine, and there would be no slippage of the center of the work. THe pins could be standard hardened dowel pins. If the drive end of the shaft is big enough in diameter so the pins have some leverage, it would probably work just fine. The tool would not be difficult to make.
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I have done that for cylindrical grinding jobs in the past, but generally, there are few jobs that CANNOT BE DOGGED, FINISHED ON ONE END AND TURNED AROUND AND COMPLETED WHER THE DOG WAS DRIVING.
 
I had a lathe many years ago that had square centers, but not the sort being talked about here; the centers were tapered on the ends that fit the head and tailstocks and were about the same size and taper of #3 Morse, the lathe was perhaps from the 1850s and the carriage was moved by a flat leaf chain and sprocket, it was about 24" swing (blocked up about 3") and 8 ft C-C. It is an antique machine collection somewhere.
 
francist said:
This is from my Audel’s “Progressive Machinist” c.1913 — it suggests the square centre is to be used more for correcting an inaccurately placed centre hole on the work rather than driving the work. At least if I’m reading correctly...

View attachment 308337

-frank
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Obviously pre-OSHA:eek 2:
 
This use of a square center, to relocate a center for true running is a whole different use for the device, they were in fact used for driving work, I think, especially in the turning of brass articles, which back in the day was done using hand tools much like wood turning.
 
Bob Korves said:
Using a drill bit on a mill with a centered rotary table would be my first idea. To make it even better, drill the hole(s) a little undersize and then ream them for a nice and snug pin to hole fit.
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Unless the pin is perfectly located, it would tend to draw the part off center, I think better to have some clearance, that is what I did for grinding work.
 
Good ideas folks, thanks for your thoughts. The countersink idea would be the most simple approach. This one would seem to have a chance to work. 1-170-81056C
Would you hold it in a four jaw or in a collet?

If it doesn't work as a driving centre at least it will still be useful as a countersink :)
 
I have seen a shaft that had several radial grooves pressed into the end that looked like they were used to drive the part. Looked like they were put in with a stamp and a smack with a hammer.
 
Center drivers are available. You need to be quite wealthy to buy one.
 
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