What size barrel vise bushing?
I have a Brownells barrel vise and one of their #3 aluminum bushings which only has a 1" thru hole. A friend of mine has a lathe and can hone this out for me so I am looking for information on how much to open it up prior to cutting it in half. This will be for a varmint contour barrel on a Savage 112.
The three inch section of barrel just behind the barrel nut has a slight taper starting at 1.057 and tapering to 1.027 at 3" Should I have this honed to this exact dimension? I also have a set of Brownells lead shims in case he can't taper it. What do you guys think?
If you give me the exact length of the bushing I can work out the taper angle to set the compound slide on the lathe to bore it on a taper as it will only be a short taper .
Alluminium collets can just be the exact size and don't have to be a perfect taper as they crush and destort a fair bit and you can run the barrel in a bit more till it jams a bit in the collet and then tighten it up.
Are you giving yourself enough room behind the barrel nut to work the wrench and allow a bit of slide up room as alluminium collets get looser with use ?
If the collet is 3 " long then the taper half angle will be .3 degree.
Using the collet as a sinebar roll distance of 3 inch . With the boring bar touching the back edge you would need a gap of .015 to the boring bar at the very front edge to set .3 degree . Or use a digital angle gauge . Or use a sinebar setting gauge on the compound that goes up against the tailstock shaft.
Last edited by J. Valentine; 05-20-2011 at 12:56 AM.
Thanks J. The bushing is 3" long and I'm looking at this a couple different ways. One is to have it tapered to match the barrel, and the other is to do a straight 1.057 cut and just use the lead shims to take up the taper. I also want to use this bushing to take off the existing barrel that has pretty much the same taper going from 1.030 to 1.004. I think with this barrel I can get by with the lead shims to fill the gap.
When I measured this, I only left about a 3/8" gap in front of the barrel vise to fit the barrel nut wrench. Should I go a little longer on this to allow for slide up room? Thanks.
The collet will hold better if it is taper bored to fit the barrel . Remove any grease or oil from the barrel and the collet with quick drying solvents . You can also dust the collet with fine powdered rosin for extra grip and I have also used castor sugar .
It is no more work to bore it with a slight taper than to bore it straight.
I think 3/8 is a bit close come back to 1 inch it will still be very rigid it depends on the barrel nut wrench style that you have . You will have to bore to different diameters but the taper will not change much . If you like I can recalculate the taper with the new diameters.
That is the good thing about the barrel nut setup it does not place any strain or flex on the action to unlock it and is close to the vise collet . However it is harder to lock onto the nut than an action .
The thing is that more damage is done to barrel finish by a slipping collet than a tight lock up. Even a lead shim can mar a barrel by slipping around . Aluminum is already fairly soft unless you have some hard grade and a lead shim will just reduce it's holding capacity . A lot depends on how hard the barrel is to crack but the problem is you don't know how hard that will be the first time. Some people tape barrels and pad collets but I have not had much success with it and got more slipage.
So the first unlock has to be with the best max grip you can get so you don't get a slipping collet . Then once it is out it does not require so much grip to do it with the next barrel.
However even a tight barrel nut is not as hard to move as a tight barrel shoulder if the barrel nut wrench has a good neat fit and grip.
Last edited by J. Valentine; 05-20-2011 at 03:08 AM.
save the machine work for something else. its a savage, use an action wrench and barrel nut wrench, you dont even need to use a barrel vise.
I make my barrel vise blocks out of a 3" cube of plywood ( glue 3"x3" pieces together) . Drill a hole the size of the barrel perpendicular to the plys. Glass bed the hole to the barrel at the correct location ( don't forget release agent on the barrel) Knock the block off the barrel. Saw the block in two on the hole centerline. Clean up the split faces on the sander. Coat the glass surfaces with powdered or liquid rosin. Put the blocks on the barrel and pop into the barrel vise. Crank down on the vise a bit. Blocks fit the barrel perfectly, will not slip, will not mar the blue,and last forever as there is really no need to crush them on the barrel.
I step bore bushings. I measure the diameter at some convenient point along the barrel so the bushing will fit onto the large shank diameter as far as I want it to and stop when the smaller diameter touches the taper on the barrel. I step bore the bushing, the slit them on one side only. In use, just slide it over the muzzle and up the barrel till it stops with the small diameter touching the taper, the large one on the large diameter of the shank. Tighten vise, do what ya gotta do.
Works like a charm. Much faster than taper boring. My vise has four 1/2-20 Grade 8 clamp bolts that I torque to 90 ft-lbs lubed. I've not had a barrel slip yet using this approach.
Thanks for all of the replies everyone, I know it's a pretty basic question for this forum but I want to get it right so it doesn't mar the existing barrel. I think with all of this information I've got a pretty good handle on it. Thanks again, Bryan