How does a Blanchard Lathe/stock duplicator go wrong?

**4V50 Gary** · July 8, 2018, 08:22 AM

I lifted this from Arfcom. Apparently this stock was defective and remedied. For a "batch" of stocks to go wrong, something had to be wrong with the Blanchard lathe? Workpiece not tightened in the rear? I don't think it could be the pattern (why would anyone put a bad pattern on a Blanchard Lathe?). Thoughts?

Quote:

This stock is kind of unique, notice the scallops? This was the result of improper turning of the stock , resulting in a butt that was too small, and out of spec. It was decided to salvage the stocks with the insertion of wooden scallops to make butt plate to spec in size. Kinda clever.

**4V50 Gary** · July 8, 2018, 09:42 AM

From another post there:

Quote:

I have been told these were a early run of Overton Stocks for IHC. Specs may have just been off and weren't caught until after the run of stocks? Instead of scraping them they were modified ,just a neat bit of IHC history

HiBC · July 8, 2018, 11:34 AM

I don't have experience with a Blanchard Stock machine.

I have some limited experience with a tracer mill. Assuming the cutter is a ball mill,in theory the stylus would have the same radius as the ball mill. However,that may not give the desired results.

As I recall,there was a small amount of stylus deflection necessary for the hydraulic servos to react.
And often some finishing stock was desired.

The simple fix might be compensating with the stylus. Example,we might try a .250 radius stylus for a .500 dia ball mill. Our workpiece might be undersize by .015 material per side .

So we can compensate by making a .265 radius stylus.

T. O'Heir · July 8, 2018, 12:21 PM

"...wrong with the Blanchard lathe?..." It's more likely that one was an arsenal repair(lotta talented guys working there) rather than out of the factory like that. The Blanchard lathe held the stock blank on the end. Wouldn't have been able to do that with that stock if the blank was that short. Any stock duplicator lathe does that.
There's a link to a video of a Blanchard in action here.
https://www.nps.gov/spar/learn/histo...e/machines.htm

July 8, 2018, 12:21 PM	#4
T. O'Heir Senior Member Join Date: February 13, 2002 Location: Canada Posts: 12,453	"...wrong with the Blanchard lathe?..." It's more likely that one was an arsenal repair(lotta talented guys working there) rather than out of the factory like that. The Blanchard lathe held the stock blank on the end. Wouldn't have been able to do that with that stock if the blank was that short. Any stock duplicator lathe does that. There's a link to a video of a Blanchard in action here. https://www.nps.gov/spar/learn/histo...e/machines.htm __________________ Spelling and grammar count!

July 8, 2018, 11:34 AM	#3
HiBC Senior Member Join Date: November 13, 2006 Posts: 8,283	I don't have experience with a Blanchard Stock machine. I have some limited experience with a tracer mill. Assuming the cutter is a ball mill,in theory the stylus would have the same radius as the ball mill. However,that may not give the desired results. As I recall,there was a small amount of stylus deflection necessary for the hydraulic servos to react. And often some finishing stock was desired. The simple fix might be compensating with the stylus. Example,we might try a .250 radius stylus for a .500 dia ball mill. Our workpiece might be undersize by .015 material per side . So we can compensate by making a .265 radius stylus.