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Thread: Cylindrical Square Project

  1. #1
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    Aug 2009
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    Default Cylindrical Square Project

    I've tossed around the idea of making one of these for quite some time. The thread last week on these gave me the needed push to get started. I already have a piece of DOM tube with the ends ground flat and parallel to each other that I made for a milling set up. When indicating the ends on the surface plate the 10'ths dial doesn't even wiggle. The part measure about 3 5/8" long x 2 1/2" dia. and has a 1/2" wall. There is about a .005 - .010 variance in wall thickness around the tube. So My thought would be to first bore the ID to even up the wall and I should be able to get within .0005 all around.
    Next I would turn a couple end plugs that very lightly push fit into the end so the tube can be ground on centers on my T&C grinder. Once set up on centers I would indicate one end to be perfectly in line with the saddle in-feed and then grind the OD.
    This should end up square, at least in theory. I would mic each end and if there is any difference in dia. something is off.
    The second method in case of first method failure would be to grind the OD to be equal on each end to .0001 or better and I can achieve that accuracy on my grinder and then set the cylinder up in a precision V block and grind one end. Of course the accuracy with this method would depend on the accuracy of the V block.

    JL........................


  2. #2
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    My only suggestion is that you consider making a bigger one. 3 5/8" is a bit on the small side IMO.

  3. #3
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    I understand if you want to have a challenge, but why go ass first to a tree? Grab some solid bar, turn it between centers with one end relieved from the center so it leaves only a ring in the end and then grind it in one setting from the OD and touch clean the ringed end. Verify constant diameter and squareness and done. If you want a lighter one (and I don't see a reason for a lioghtweight measuring reference on a surface plate), then prior to grinding drill axial holes on a circle pattern through the part.
    Amount of experience is in direct proportion to the value of broken equipment.

  4. #4
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    as suggested make it bigger and use a centre, grind it between centres. recess the ends slightly and kiss the end ring while still on the grinder. No need for V blocks and potential inaccuracies
    .

  5. #5
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    Quote Originally Posted by Jaakko Fagerlund View Post
    I understand if you want to have a challenge, but why go ass first to a tree? Grab some solid bar, turn it between centers with one end relieved from the center so it leaves only a ring in the end and then grind it in one setting from the OD and touch clean the ringed end. Verify constant diameter and squareness and done. If you want a lighter one (and I don't see a reason for a lioghtweight measuring reference on a surface plate), then prior to grinding drill axial holes on a circle pattern through the part.
    OK, thanks, you and Mcgyver have the right idea. A lot simpler. I can do that. I guess I had it ass backwards.

    JL...............

  6. #6
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    The article I read in my "Machinist's Bedside Reader" about making one suggested doing it in the lathe as well.

    It's also a good test for the lathe and an opportunity to tweak out any bed twist or bending to line up dead on if the cylinder is out of parallel. So TWO projects in one are being accomplished.

  7. #7
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    If I understood the ring description correctly (analog of the bottom ring on ceramic cups on which the cup rests), I think it would be easier to turn the rings and then the center holes while holding the cylinder in a lathe chuck. Then proceed with the final turning/grinding between centers including facing of the rings.

    I don't have a cylindrical grinder, so I'd either do it with a TPG (Toolpost Grinder) or on a surface grinder between centers. If done with a TPG, I'd, probably, prefer facing the rings with a lathe tool bit (vs. grinding wheel) to make whole bottom surface of the ring perpendicular to the cylinder axis. Because if I use an OD grinding wheel on TPG, it will be hard to achieve (although it wouldn't matter much anyway: this will only affect the total contact area with the surface plate).

    Please feel free to criticize any possible flaws in my mental exercise.
    Last edited by MichaelP; 02-16-2017 at 12:46 AM.

  8. #8
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    I am sure the OP's method can be made to work, but this would be my preferred way to do it.

    I do not like the idea of any holes in it as they could be an opportunity for the metal to age differently in different places. I would keep it totally uniform, meaning solid. I would probably give it a good annealing bake after roughing it out and prior to the final finishing of both the end and the OD. Run the kitchen oven up as high as it will go for an hour or so and then drop the temperature by 100 degrees per hour until it is off. Leave the door closed until it completely cools down.



    Quote Originally Posted by Jaakko Fagerlund View Post
    I understand if you want to have a challenge, but why go ass first to a tree? Grab some solid bar, turn it between centers with one end relieved from the center so it leaves only a ring in the end and then grind it in one setting from the OD and touch clean the ringed end. Verify constant diameter and squareness and done. If you want a lighter one (and I don't see a reason for a lioghtweight measuring reference on a surface plate), then prior to grinding drill axial holes on a circle pattern through the part.
    Last edited by Paul Alciatore; 02-15-2017 at 02:38 PM.
    Paul A.

    Make it fit.
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  9. #9
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    Why make one if you do not have a cylindrical grinder ?

    They are easily gotten from the Caterpillar co.
    I got a wrist pin from a very large Bulldozer engine and it is superb. Absolutely Hard, Square, Round, and ground all over

    Rich

  10. #10
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    Quote Originally Posted by Rich Carlstedt View Post
    They are easily gotten from the Caterpillar co.
    I got a wrist pin from a very large Bulldozer engine and it is superb. Absolutely Hard, Square, Round, and ground all over
    I can not imagine new large Caterpillar wrist pins being inexpensive.

    Good used ones may well be a different matter.
    Cue up Vera Lynn and let the credits roll ...

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