Metric annular cutter?
I need to chop an RPK barrel and turn down the end for either an M76 or -74 FSB. Rather then send it off, I'd like to do it in the shop.
I was wondering if I could use a rotary table in the mill. Do some rotary tables allow you to run the barrel from the backside so that I can only have the 1.5" or so FSB journal unsupported? I was thinking I could manually rotate the table under an end mill.
Probably a Frankenstein setup, but hang the rotary table over the table edge so the barrel goes through the center and hangs off the mill table. Then get the barrel through the center and clamped in a v-block with the v-block clamped to the rotary. Swing mill turret and extend ram to reach. Not pretty, but you could do it.
with metal on metal speed setting and tight hold of part is vital. youre gonna have broken endmill flute shards hitting you in face maybe worse id imagine. parts get flung pretty far sometimes even in a Bridgeport mill if your not watching everything carefully. is the bore chrome lined? some worn metal or chrome is what they call work hardened or just harder to start with too. ive not seen your exact set up before you go to cut but you might be better off to eyeball and dermal out the rifling lands and use 2 sizes of center drill then cut the end off and file by hand flush. that will give you the required crown and allow the crown to be centered.
sounds crazy but thinking outside the box works sometimes. im thinking this is a Philippine jungle workshop method using a hand drill and self centering using a center drill but hey if that's all ya got it might work.
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Something like this. I would cut the M72 barrel to 16" (or shorter if I go with the M76 FSB). For profiling, I would drop the quill with an end mill to the barrel, make a slow revolution with the rotary table, then feed the X axis toward the end mill, followed by another rotation, etc. I wouldn't be taking off much, and from my experience, the Yugo barrels are pretty soft.
My lack of experience is showing I'm sure- Are rotary tables (w/ chuck) meant to have the work piece sticking through the backside? I'm basically trying to use the rotary as a lathe without a tailstock.
But I'm assuming the chuck may or may not have a centering pin that fills the center hole on the rotary table?
You are not going to get a very good finish with that setup if your looking for a press fit. A lathe is really what you want to use. If you decide to send it out I can help. I can turn, thread and crown barrels for a fair price. I have been in the machine trade for almost 40 years. I'm not really looking for work, just helping out.
You might be able to get away with a rotary table that has a 4MT bore or larger (generally 12" or larger table) and a chuck that is designed to bolt directly to the rotary table using the T slots instead of using the morse taper.
I think Pookey has turned down a barrel by chucking it up in a drill press and running a peanut grinder up and down it.
Your plan can't be any more WECSOG than that.
I have used a rotary to do this, but like said above you will not get a very good finish. Make sure if you do try this to use a ball Endmill. A square Endmill will brake as soon as it makes contact. A lathe is the best way to go.
One thing I have done if you don't need to take a lot off is this. Get a live center and put it into a v-block, held in a vise. Find the centerline of the live center using an indicator. Place the barrel into a tool holder. Collet holder works best. Put the tool holder in the spindle and bring the z-axis down until the barrel sits in the live center. Use a file first to do most of the removal, then sand paper stepping down to fine emery cloth.
This works fine for removing small amounts of material if you have no other choice.
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Not sure what the old pooky trick is but, you are just taking a lathe and standing it on it's side. You have a head stock "spindle" and a tailstock "live center in the vise".
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