Anyone out there doing their own crowns on a lathe. Any tips?
I plan on centering in a four jaw with a brass pilot and indicate off this to centre to bore and then crown from the bore out. Is this the correct way.
Plan on doing a 90 deg recessed but there is a lot of conflicting info re the 11 deg crown and if it does actually make a difference.
I dont do it myself but that is the way I have seen it done. Make sure the pilot is of the same bore size and is straight of course Recessed 90 degree is the go. My gunsmith has a proper crowning tool to cut it, but you can use the normal lathe tools just work in very very fine increments when finishing it off.
You can do them on a lathe no worries, but depending on the length and weight of barrel, you may want to support the rear of the barrel to get it truely straight. I built a spider that goes on the back of the head stock, with grub screws and aluminium plates to go around the barrel. I use a dial indicator to get this within a thou, then go to the front for the really fine stuff.
You can indicate off a pilot in the bore, just make sure it's a really tight fit, and goes far enough into the bore to give a true centre. I bought a set of Deltronic pins from the US, they are graduated in 10th of a thou, so I just use them. I also have a tenth of a thou dial test indicator, so I can get the barrel exactly in the centre, or within a tenth.
11 degree or recessed doesn't seem to make much difference, it's really a case of the tooling you have, and what is easier.
I shoot Long Range benchrest, so you might not need quite this degree of accuracy, but I just do it this way because I can, and I know it is perfect then. My wife reckons I'm OCD, but then you have to be to shoot 1000yds.
The price of the pins will make you grumpy too. From memory they were around $300 for a set of 25, you get them from Deltronic in California. Biggest issue is you need a set for each bore size, Ideally I would get a set for the 6mm as well, but have other things to spend the money on at the moment.
One thing we have started doing up here in Townsville is monitoring what is happening to the crown. The pins are so accurate, you can watch the muzzle start to bell. We don't have a magic number yet, but should have an answer in the next year or so, saying that if they crown bells x tenths of a thou, it's time to recrown, rather than just every 400 rounds or whatever.
Recessed 90 degree is the go. My gunsmith has a proper crowning tool to cut it, but you can use the normal lathe tools just work in very very fine increments when finishing it off.
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