what type of workholder should be used
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    Default what type of workholder should be used

    First off I am not a trained machinist, sort of a jack of all trades .
    I need to machine some wheels that will be used in a "turks-head"
    There are 4 wheels forming a rectangular hole thru which we draw round AL and CU tubes. The wheels are machined oversize and then heat treated to hrc 60 - 65.
    When done the axels A and B should be aligned within .0005 and the flats of the sides C and D parallel within .0005 and perpendicular to the axels.
    Not having a lot of experience doing something like this I really do not know how to start.
    We have a Victor 20-40 lathe with buck 3 and 6 jaw chucks and also a bison adjustable collet chuck.
    Any help would be appreciated.
    Carson

    Last edited by carsonc; 02-28-2011 at 09:21 PM.

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    well no one can see the pics now, I have no idea what happened to them.
    What I am working on is a steel wheel (d2) 3 in in dia and 2 in wide with .75 in axels that are .75 in long.
    I need the axels to be very parallel and the side of the wheel to run true with the axels. what would be the best way to hold these so that everything comes out true. All attempts so far have failed.
    Carson

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    What do you have for tools/machinery for manufacturing these wheels?

    What quantity are you making and is this a repeat job?

    Regards,

    Stan-

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    Default

    Quote Originally Posted by carsonc View Post
    First off I am not a trained machinist, sort of a jack of all trades .
    I need to machine some wheels that will be used in a "turks-head"
    There are 4 wheels forming a rectangular hole thru which we draw round AL and CU tubes. The wheels are machined oversize and then heat treated to hrc 60 - 65.
    When done the axels A and B should be aligned within .0005 and the flats of the sides C and D parallel within .0005 and perpendicular to the axels.
    Not having a lot of experience doing something like this I really do not know how to start.
    We have a Victor 20-40 lathe with buck 3 and 6 jaw chucks and also a bison adjustable collet chuck.
    Any help would be appreciated.
    Carson

    I cannot make out your pictures at all, but let me make a few points first.
    1) You are being asked to hold that kind of accuracy while trying to perform a forming technique? Seems a bit unusual to me. You will have enough defromation in the finished tube that those initial tolerances are moot.
    2) As also stated by another member, what other tools do you have to work with. Machining, then heat treating, will certainly change the dimensions. You will need to finish the work with cylindrical/OD grinder to get it to your .0005 tolerances.
    IMO, it would seem logical and sufficient to machine the rollers from tool steel and heat treat if you thing the forces will cause problems. Aluminum and Copper are pretty soft after all....
    Grant

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    I cant make out the pictures either, when I orig posted them they were too large but readable and now they are too small .
    What I am making looks like a steel wheel 3 in dia and 2 in wide, there are axels on both sides .75 dia and .75 long. When mounted on the turkshead there are 2 wheels of 1 size and 2 others of another size,
    The larger wheels are at the top and bottom and the smaller wheels are on the sides. The width of the smaller wheels is the same as the smaller dim of the finished tube , the larger dim is controlled by moving the smaller wheels in or out. all the wheels touch one another so that the metal does not flow out the corners.
    When we are drawing the tubes there is a mandrel inside that controls the inside dim and corner radius. The finished part (a rectanglular tube) is +/- .001 . wall thickness can be .020 up to .050.
    I was trying to do all the work on the lathe, we have dead and live centers,a bison adjustable collet chuck, 3 and 6 jaw buck chucks
    I turn the d2 bar stock slightly oversized and then heat treat the parts, we try for hrc 63, then do the finish work.
    I tried using the collet chuck and the live center (yes I know that's not correct) but its what I tried, I could only get within .002.
    I wanted to try and avoid using just centers with a lathe dog, because it is very hard to grip the hardened axle (with the dog)
    I need to make 15 pairs of different sizes.
    Because the wheels touch each other (forming the rectangle) is why the tolerance is so tight and also one reason for heat treating.
    We only use AU and CU tubes but they will wear the wheels after a while even tho they are heat treated.
    An average run would be 3,000 feet of finished tube.

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    Years ago I made shaped tubing on a draw bench with a Turks head. The rolls were ground to a fine finish, no doubt between centers on a cylindrical grinder after heat treatment. We were making tubes in the shape of the leading and trailing edges of helicopter rotor blades. I am thinking a lathe-turned roll would mark up the tube.

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    We can normally get a near mirror finish on the wheels by using a new insert for the final pass.
    I might have found the reason I cannot hold the tolerance, it seems like the live center which has 3 rows of bearings plus the thrust bearing has a problem. It still turns smoothly , but there seems to be a little play that was not there before. It would be common to all the different setups I have tried. I ordered a new one from DGI and hopefully it will do the trick.
    Carson


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