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Crowning Tool Pilot Diameter
- Thread starter CowTowner
- Start date
Clark, we don't have the fancy tools you do. My friend just turns some brass and aluminum for fun on a small lathe in his garage.
While I appreciate the pointer to the correct tool for the job, I was hoping someone could measure the pilots they have on hand and provide the dimensions.
While I appreciate the pointer to the correct tool for the job, I was hoping someone could measure the pilots they have on hand and provide the dimensions.
Call Brownells 1-800-741-0015
or email them http://www.brownells.com/aspx/general/Contact_Us.aspx.
You will connect with a tech who will lkely answer your question in detail. Great folk.
or email them http://www.brownells.com/aspx/general/Contact_Us.aspx.
You will connect with a tech who will lkely answer your question in detail. Great folk.
Cowtowner,
If you want pilots for those chamberings in general, then I would start with the SAAMI drawing barrel dimension for bore diameter less 0.001".
.380 Automatic 0.348"-0.001"=.0347" pilot
.38 Super 0.346"-0.001" = 0.345" pilot
40 S&W 0.390"-0.001"=0.389" pilot
45 Auto 0.442"-0.001"=0.441" pilot
If each pilot is for one specific barrel, you can cut that fit in half, but how important that is also depends on how long the pilot is. If you have a pilot that's one inch long with 0.001" of wiggle room, it can theoretically allow up to 0.0005" of tilt across a 0.5" muzzle. If it is a 4" long pilot (and the barrel is at least that long, too), the maximum tilt will be a quarter of that. This assumes perfectly square seating of the pilot on the cutter.
If you want pilots for those chamberings in general, then I would start with the SAAMI drawing barrel dimension for bore diameter less 0.001".
.380 Automatic 0.348"-0.001"=.0347" pilot
.38 Super 0.346"-0.001" = 0.345" pilot
40 S&W 0.390"-0.001"=0.389" pilot
45 Auto 0.442"-0.001"=0.441" pilot
If each pilot is for one specific barrel, you can cut that fit in half, but how important that is also depends on how long the pilot is. If you have a pilot that's one inch long with 0.001" of wiggle room, it can theoretically allow up to 0.0005" of tilt across a 0.5" muzzle. If it is a 4" long pilot (and the barrel is at least that long, too), the maximum tilt will be a quarter of that. This assumes perfectly square seating of the pilot on the cutter.
Dixie Gunsmithing
Moderator Emeritus
All pilots run about 0.001" under size of the bore, to keep them concentric. It is best to measure a bore, and turn one, if you want to get it super-accurate. If correct, they will fit snuggly, and turn, but there will be no discernible movement as far as wobble, etc.
Dixie Gunsmithing
Moderator Emeritus
You can turn a pilot to about 0.001" fat, which would equal the actual bore dimension, easily, then use emery cloth to take it down to a pilot dimension. That gives it a smooth surface, like it would have had if it been ground.
One can actually take the pilot blank out of the lathe, and keep trying it for fit, in the bore, once you start with the emery, and get the closest fit possible that way. You want it to just slide in, and be able to turn. If you have a long enough bed on the lathe, pull the tailstock back, and use the rifle barrel as a gauge, without taking the blank out of the chuck.
One can actually take the pilot blank out of the lathe, and keep trying it for fit, in the bore, once you start with the emery, and get the closest fit possible that way. You want it to just slide in, and be able to turn. If you have a long enough bed on the lathe, pull the tailstock back, and use the rifle barrel as a gauge, without taking the blank out of the chuck.