Post by jimmarch on Aug 9, 2012 0:57:53 GMT -5
I need a quick sanity check here before I put a $270 part under the knife.
I'm in the middle of converting my Ruger NewVaq 357 to a true 9mmPara. I have a Bowen chromoly cylinder blank for a Ruger mid-frame, I have a section of Douglas Premium Barrel in true 9mm left over from somebody's rifle project
and I have access to a machine shop with lathe and mill. I've been practicing and working on some of the peripheral parts that don't matter so much, like the gas trap to get threaded on the end of the barrel.
The lathe is in excellent shape and I've made good progress on the barrel. I have it turned right and threaded correctly both ends, and I'm happy with the alignment.
BUT, the cylinder is another matter. Haven't touched it yet. Did some tests on the mill today, and it clearly has some free play "wiggle" at the business end....015" or so thou per my dial indicator. Taking it straight up and down with my chucking reaming in there, dial on the reamer shaft, I'm getting about .002" play on the dial.
Now. Assuming I can get the cylinder blank locked in good on the mill's vice, and get it aligned vertical in relation to the mill's chuck, and understanding that I'm just using the mill like it was a drill press...will this kind of play in the mill head matter?
More details: I know the Bowen blank is already heat-treated, to about 35 on the Rockwell C scale. It has .2" pilot holes that seem to match my frame extremely well, so I'm not going to get fancy and try line-boring it. I'm going to follow the pilot holes Bowen drilled.
I have a good quality US-made cobolt twist drill of 11/32nd (.3437 decimal) to expand the pilots pre-ream. I have a good US-made chucking reamer of .3555" for the "long throats" this will need. And I have a Manson chamber reamer that I can pilot to guide inside of the .3555" hole, and hand-ream to the correct headspace.
I *think* the normal pre-ream drill size should be 1/64th (.0156") smaller than the final ream size. The drill bit in question is just a fraction bigger than that spec would call for, by .003". I'm thinking that shouldn't matter, right?
Assuming I can flood all these steps with enough oil, does it appear I can do this, despite the slop in the mill head? Will that slop let it follow the Bowen .2" pilots correctly, or is it likely to wander?
YES, I'll be doing test holes, but...not in full-grade chromoly.
Am I on the right track here, or am I about to seriously hose a $270 cylinder blank?
I'm in the middle of converting my Ruger NewVaq 357 to a true 9mmPara. I have a Bowen chromoly cylinder blank for a Ruger mid-frame, I have a section of Douglas Premium Barrel in true 9mm left over from somebody's rifle project
and I have access to a machine shop with lathe and mill. I've been practicing and working on some of the peripheral parts that don't matter so much, like the gas trap to get threaded on the end of the barrel.The lathe is in excellent shape and I've made good progress on the barrel. I have it turned right and threaded correctly both ends, and I'm happy with the alignment.
BUT, the cylinder is another matter. Haven't touched it yet. Did some tests on the mill today, and it clearly has some free play "wiggle" at the business end....015" or so thou per my dial indicator. Taking it straight up and down with my chucking reaming in there, dial on the reamer shaft, I'm getting about .002" play on the dial.
Now. Assuming I can get the cylinder blank locked in good on the mill's vice, and get it aligned vertical in relation to the mill's chuck, and understanding that I'm just using the mill like it was a drill press...will this kind of play in the mill head matter?
More details: I know the Bowen blank is already heat-treated, to about 35 on the Rockwell C scale. It has .2" pilot holes that seem to match my frame extremely well, so I'm not going to get fancy and try line-boring it. I'm going to follow the pilot holes Bowen drilled.
I have a good quality US-made cobolt twist drill of 11/32nd (.3437 decimal) to expand the pilots pre-ream. I have a good US-made chucking reamer of .3555" for the "long throats" this will need. And I have a Manson chamber reamer that I can pilot to guide inside of the .3555" hole, and hand-ream to the correct headspace.
I *think* the normal pre-ream drill size should be 1/64th (.0156") smaller than the final ream size. The drill bit in question is just a fraction bigger than that spec would call for, by .003". I'm thinking that shouldn't matter, right?
Assuming I can flood all these steps with enough oil, does it appear I can do this, despite the slop in the mill head? Will that slop let it follow the Bowen .2" pilots correctly, or is it likely to wander?
YES, I'll be doing test holes, but...not in full-grade chromoly.
Am I on the right track here, or am I about to seriously hose a $270 cylinder blank?
