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Thread: Any home made indexing fixture ideas?

  1. #1
    Boolit Master
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    Any home made indexing fixture ideas?

    I have 2 straight barrels(no profile). I want to try make one a octagon and the other flutes. I have a Rong Fu (RF- 20) mill and a EMCO Maximat V10-P lathe.These are hobby equipt but its what I have. I don't have nor at my age do I want to put out more money for tooling over what I have. Any one ever make your own fixture to do this on a mill or a lathe?
    Look twice, shoot once.

  2. #2
    Boolit Master uscra112's Avatar
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    You don 't need an indexer to cut an octagon from a round. Lay the barrel on the table. Cut one flat with a face mill. Flip it over and cut a second flat parallel to the first. Now hold the barrel against a right-angle plate and cut flats at 90 degrees to the ones already cut, OR you can leave it where it is and cut the 90 degree flats with the side of an end mill. Use those four flats to locate the barrel in vee-blocks for the remaining four cuts. Do this twice. Leave enough metal on the first passes to allow for the second passes to achieve final dimensions. One bit of wisdom I learned from my machine-tool building days is that the focussed heat from milling a long thin part will cause warping.** Light cuts, and keep it as cool as possible. Draw file to get a nice final finish.

    **We had one of the largest planers still in existence, and used that to machine lathe beds up to 60 feet long. Heat was distributed end to end on each stroke, so no warping. Planing is how barrels ought to be done, but nobody has planers anymore.
    Last edited by uscra112; 02-09-2018 at 02:02 PM.
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  3. #3
    Boolit Grand Master

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    There are several ways to index an Octagon. on a barrel octagon nut can be made with barrel threads and screwed on tight. then used to index. set barrel between centers and clamp down alighning to flats on the index nut. If you want a tapered octagon then one center post needs to be adjustable for height or shimmed up to achieve the desired taper. Machine in 180* to each cut light cuts and feeds. depending on your mills stability and or solidness climb milling gives a better finish, but on worn lead screws or screw type leads tends to grab. Also if
    you mark your barrels index to the action before set up then the dovetails and screw holes can be put in in this set up also.

    Some of the set up is going to be determined by the length of the barrel and travel of your machine. It gets trickier if the barrel is longer than the travel and cant be done in one pass.

    A simple quick way is to clamp a vee block on the breech end and use it to alighn the barrel flats. Once clamped on and a cut made it cant be removed and stays attached. If you want the traditional "tulip" transition on the octagon then side milling with the appropriate mill is the easiest way. For flutes a ball mill can be used and barrel help in a vise. For a true traditional radious in the flutes a horizontal mill was used with a larger dia mill cutter and the radious on it. A special slitting saw the width of the flute and radious to give finished dimensions. Cuts were .005-.010 rotating 180* thru the pattern till to depth. Stops were set to each ends end of cut. This can be done with a arbhor made for the cutter in a vertical mill and working on the sides centerline. A 3" slitting blade gives about the right radious in and out of the flutes. A ball mill does okay but not the traditional look.

  4. #4
    Boolit Master
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    Thanks fellas for sharing that information. I will give this a try when it starts to warm up. When I bought the mill it came with alot of tooling and it has an arber and saw blades but I never tried them. I do not have coolant pump so I go real slow. Will the saw be ok with that?
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  5. #5
    Boolit Master
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    Coolant washes the chips from the cutter teeth,thin saws are quite fragile and a chip of swarf across a tooth will break the saw.....Climb milling is to be avoided,unless the machine is specifically capable of climb milling.I have seen a machine lift the whole weight of knee and table when a cutter on an internal shape grabbed the far end of the cut,broke the cutter clean in half,and gouged the collet chuck.

  6. #6
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    Not 100% sure which one is the RF20 but I have one of the round column HF green drill/mills. I used a 5c collet indexer bolted to a piece of 3/4"x4" steel (the tailstock was made from the same 3/4"x4" steel) and an approx 1" end mill to get the rounded transition I wanted up towards the receiver ring. The combination of barrel/indexer/tailstock was longer than the bed on my mill and the actual x travel was just over the 22" barrel length. One of the 5c spin indexers will work and they can be had for around $50 without the collet you'll need that will run another $10 or so. It made milling the flats on my mauser's barrel easy. I followed basically the same 10-15K cut rotate that countrygent outlined and used a flood coolant setup made with a bucket, $15 pond pump wrapped in a shop towel to prevent chips from getting inside of it, and I splurged for a magnetic base line-loc setup and added a drain to one end of the table that went back into the bucket (kitty litter with flip top). I added in a T fitting inside of the bucket with a valve to control the flow pressure. Worked great and helped wash away the chips. Draw filed and polished while still in the index jig and even soldered on the sights and swivel base while still in the jig. I know you don't want to buy any more tooling but figured you might find something useful from what I did.
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  7. #7
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    HF in the past had a model almost identical to mine. Mine has approx a 5 inch round column and when I first saw your pictures I thought we have about the same style mill. Yours fortunately has an operator that knows what he is doing and mine doesnt! I was looking at that 5c indexer and that is tempting but this fixed income can drive ya almost nuts. I am not complaining because I still can walk and go any where I want to if I take my time. I have a brand new pump from a 90 percent efficiency furnace(very small pump for condensation water)It would be about right volume for a couple small hoses.
    Look twice, shoot once.

  8. #8
    Boolit Grand Master

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    On a small mill the slitting saw style blade may require a closer set up due to limited travel of the machine. If x travel isn't enough you may have to do 2 set ups meaning recatching the original surfaces. The end mill has the advantage of a smaller dia hence less leverage. usually less spring or flex to it. Even plain old air blowing on the cutter at 15-20 psi goes along ways to cooling and keeping cutter chip free. Water soul is good Black sulfar oil is the best. But the opposite when it comes to clean up of the machine. We would put a cotton cloth over the tanks opening for returning oil to flow thru, this removed a lot of swarf from it. These chips will be sharp and nasty to deal with. here the larger dia side mills are a plus is on a horizontal mill where 2 can be spaced out to desired width and 2 flats cut at the same time. But this only works for straight tapers.

  9. #9
    Boolit Master Moleman-'s Avatar
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    Where there's a will there's a way. Might just take a few ideas till one grows on you. This is about the cheapest indexer out there besides the blocks which only come in hex and square. https://www.ebay.com/itm/5C-PRECISIO...kAAMXQW7VRELSd I've used a cheap $1 plumb bob that I drill a hole in and added a set screw to hold reamer blanks until I got the set of 5c collet blocks and eventually a universal dividing head and the spin indexer. If you found a chunk of octagon stock you could bore it for whatever barrel threads you're going to use but it would need to be timed to the barrel which in turn had a flat milled into it while torqued onto your receiver. The barrel in that pic was installed and a flat cut at TDC then installed in the jig and leveled. If you have a 16, 24, 32, 40, 48, 56, 64, 72, or 80 change gear you could use it as an indexer. I did a version of that to repair a couple teeth that were broken off of the 12" Sheldon lathe I bought. Basically two teeth shaped wedges locked in the gear that was being milled around a center arbor. The fly cutter was centered on a good tooth valley, the gear indexed to a missing one that had been filled with braze and then the root/valley was re-cut. Another idea is I believe on here somewhere. A guy made an octagon barrel by mounting it in his lathe and locking the bull gear which was used as an indexer. He put a lathe bit in with the cutting edge facing the headstock and used his lathe as a very slow shaper to take a few thousands off at a time.

    At any rate here is a pic of my drill/mill shortly after putting the barn up. it was about 3-4 years old at that point and except for the broken plastic cap on the column from moving it was stock at the time. So far in 10 years I've replaced the pin that holds the draw bar head to the shaft, and the rubber way guard wore through and was replaced. Added a power feed, caliper to the down feed, flood coolant and a light inside the head that shines down. It's been a good little mill for me.
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  10. #10
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    Yup, thats identical to mine. When I bought it at a sale I was talking with an older gentleman who had a small pattern making business and his father (deceased) was a gunsmith all his life. He gave me alot of good info (the auction was small metal shop, owner retired). He said if I get the mill and the mill is not what I want it will be the best drill press I could buy. I got the mill, stand and tooling for around 400 hundred bucks. I never regretted it. Of course I was a farmer and construction worker so metal work is new to me for the last 20 years.
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  11. #11
    Boolit Master Moleman-'s Avatar
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    For fluting I wouldn't use the ball end mills I'd use the slitting/slotting saws as mentioned before. I did one barrel with the flutes didn't turn out as nice as they would on a more ridged machine. The slotting saw arbors are easy enough to make on the lathe you have if you don't already have one in the tooling you got with your mill.

    What guns are the barrels going on?

  12. #12
    Boolit Master
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    one will be for a vz24. I bought a bunch of these guns many years ago for playing with. The one barrel I got from Sarco. They have a bunch of 8mm machine gun barrels(I think they said they are new) and they got some of them chambered for 8x57. So that one gets fluted. I never ever dreamed I would build a heavy barrel target gun in 8x57, but the reviews of fellas that rebarrel with them are better than I can dare think! The other is a heavy 22 barrel I will chamber in 22 Hornet for on a pivot action I am making and that one I want to make octagun. I got more dreams than I got money for so I go with the cheap stuff. I have been devouring and meditating on your 35 caliber ar because I really want some time to put a 35 caliber together for myself. I would like to have it a bolt action that could be switched to semi auto easily. I sure enjoy the wisdom on this forum from y'all!
    Look twice, shoot once.

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