Threading a barrel on a mill

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Sdustin
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Threading a barrel on a mill

Post by Sdustin » Fri Mar 01, 2013 10:40 pm

What's up everyone I want to know if it's possible to thread a barrel with enough accuracy on a CNC MILL. I have a saiga .308 and want to thread the barrel for an ak74 break but I want to be able to mount a silencer once I get one. Is there a way to do it on a mill indexing off the bore? I haven't talked to my uncle that's the machinist yet so he may already know but I figured I'd ask here.

I know he's a good machinist and total gun guy. He showed me a break action .410 he machined the whole thing from 316 stainless and 304. Plus made some parts from brass. He's really good. And he's threaded a .22 rifle for me but he was able to chuck it in the lathe.

And this was the best place I could think to put this question. Thanks.
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Dr.K
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Re: Threading a barrel on a mill

Post by Dr.K » Fri Mar 01, 2013 10:41 pm

I don't have a mill yet, so I don't know. But, if he has a lathe then use that.
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Sdustin
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Re: Threading a barrel on a mill

Post by Sdustin » Fri Mar 01, 2013 10:54 pm

It's an ak. I don't want to have to remove the barrel an I don't think he could put it in the lathe without the barrel removed.
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Re: Threading a barrel on a mill

Post by Dr.K » Fri Mar 01, 2013 11:11 pm

So, you're talking about putting the entire rifle in the mill, and threading the barrel?
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Re: Threading a barrel on a mill

Post by Sdustin » Fri Mar 01, 2013 11:36 pm

Yea I'm sure the table would allow the rifle to be below the table and barrel pass through and mount the barrel with the muzzle 4-6" above the table.
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ChimeraPrecision
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Re: Threading a barrel on a mill

Post by ChimeraPrecision » Sat Mar 02, 2013 12:39 am

1. Your Fixturing needs to be exceedingly rigid, with as little barrel standing above the vise/clamps as possible.

2. Get the closest fitting gage pin to the barrel. Insert said gage in into barel and use an dial indicator to incicate the center of the pin.

3. I assume you have experience thread milling,
Inset proper tool run program and show us some pics when it's done
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57fairlane
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Re: Threading a barrel on a mill

Post by 57fairlane » Sat Mar 02, 2013 1:38 am

Chimera nailed it.

Thread milling is pretty common in CNC land . . . just need the tool and a controller to run X,Y,Z at the same time

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Re: Threading a barrel on a mill

Post by Bendersquint » Sat Mar 02, 2013 2:09 am

I want to see the fixture you come up with its going to be massive.

I watched a thread milling of an AK 2 years ago and the jig was ridiculously large took about an hour to set up and the threads still didnt come out perfect.

I havent seen a stronger jig!

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Re: Threading a barrel on a mill

Post by Sdustin » Sat Mar 02, 2013 2:48 am

The machinist that's my unlce has mill threaded before I'm sure. And bender you saw someone mill thread an it still wasnt right I may not even try it ad just remove the barrel as much as I'd like to avoid that. I guess it can be ray hard if you have a press.
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Re: Threading a barrel on a mill

Post by Bendersquint » Sat Mar 02, 2013 3:39 am

Sdustin wrote:The machinist that's my unlce has mill threaded before I'm sure. And bender you saw someone mill thread an it still wasnt right I may not even try it ad just remove the barrel as much as I'd like to avoid that. I guess it can be ray hard if you have a press.
To say this shop knew what they were doing would be an understatement, these guys do things most people cant even dream of.

The stuff that comes from that shop is utterly revolutionary.

It would be alot easier to pull the barrel and thread on a lathe, thread milling can work but with a piece like this the lathe is better.

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Re: Threading a barrel on a mill

Post by Sdustin » Sat Mar 02, 2013 4:07 am

Here's a pic. I did the trigger conversion myself. I bought the lower handguard retainer from Dinzag he makes a lot of different saiga conversion parts.
Image
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Re: Threading a barrel on a mill

Post by kingjamez » Sat Mar 02, 2013 7:54 am

I'd like to see a mill that allows "table would allow the rifle to be below the table and barrel pass through".

I can't picture that.

I've done some accurate threadmilling, and if you follow what Chimera said I think you'll be good to go. The only thing that I'd add to Chimera is that I'd make a custom barrel insert rod that is at least 12" long. Stick that into the muzzle with 6" going into the bore and 6" above the muzzle. Use a dial indicator on the rod while jogging the Z axis to ensure that the Z axis of the bore is the Z axis of the machine. Do that, and then indicate with a co-axial indicator and you'll be good to go.

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Re: Threading a barrel on a mill

Post by ChimeraPrecision » Sat Mar 02, 2013 11:27 am

He may have a horizontal mill, and not the knee type vertical mill we are thinking of
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Re: Threading a barrel on a mill

Post by SRM » Sat Mar 02, 2013 8:47 pm

just find a big bore lathe and be done.

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Re: Threading a barrel on a mill

Post by Sdustin » Sun Mar 03, 2013 2:09 am

Dinzag sells a thread kit with a thread aliment tool (TAT) its much easier and i can do it all by myself, i think im going to do that and hell i may get lucky and it be good to go and if not oh well. i really want to just get an ak74 muzzle device for it and leave it for a while, then im either going to buy another one to make a folding stock with HK sights on the dust cover and gas block ans ak74 black polymer handguards, and an up turned charging handle, and a coustom RMR mount at the current rear sight block, or outfit this one like that.

id rather just have two one that looks like a regular run of the mill wood stocked ak74 and another one thats all custom with the above mods, once i do the mods if my hand thread job doesnt line up im going to build a form 1 freeze plug reflex can and have a threaded collar right in front of the gas block.
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Re: Threading a barrel on a mill

Post by Shift1 » Sun Mar 03, 2013 1:23 pm

Why not just replace the front sight block with one that is already threaded for 24mm? If necesssary turn barrel down to fit (concentic to bore) You can dial in a receiver in a four jaw lathe chuck. Just need to use lighter clamp force so not to crush it. Take lighter cuts to not twist it. Doing it between centers would be the ideal but ya gotta do what ya gotta do.
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Re: Threading a barrel on a mill

Post by Sdustin » Tue Apr 09, 2013 4:44 am

I got a 5/8x24 die moved the front sight back one pin and re pinned it when i went to start to tap (i also had a thread aliment tool) i found out my barrel was too big for 5/8x24 i was at my uncles machine shop so he offered to thread it between centers while chucking the receiver into the lathe with plastic blocks, he was supposed to email me pic of the thing set up but i haven't gotten them yet, but its done now i just need to get the ak74 brake that i want to use, also i didnt want to do the front sight cause i didnt want to buy a new front sight and i wanted to be able to use a silencer one day, my uncle said he indexed off the bore and its fine for a can, hes very experienced with guns so i know its good to go
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Re: Threading a barrel on a mill

Post by cncjerry » Tue Apr 09, 2013 10:54 am

You need a long table and a head that can rotate to horizontal. You also need software that will do helical interpolation within the correct plane. A lot of software will Only do helical around the z axis, mine will do all axis so I can generate the program for you.

Problem is it won't be as good as a lathe, close will be difficult.

Jerry

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