CNC grinding method of manufacture - Page 2
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  1. #21
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    To the OP. I'll echo what others have already suggested, this isn't an ordinary job for a new applicant. At the beginning of my career I interviewed with the foreman after talking with the office folks. The foreman had a long brass shaft in the lathe and was cutting a modified acme thread on it. He gestured to it and casually asked me if I could do that. I had never cut threads in a lathe, let alone acme threads on a long shaft that I knew would deflect. I told him that I didn't know how at the moment but was sure I could learn how to. He hired me right then based upon my answer, also telling me that the applicant before me had tried to BS him and that was why he didn't hire him. This part might be testing for the depth of your knowledge, honesty, AND whether you try to BS your way through a job with a material most of us have never had to grind. You can be held accountable for what you claim to know. It smells of a baited trap.

  2. #22
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    You are applying for a position that will be providing training. I don't think they are expecting you to nail the process but they are looking for someone with general knowledge and the ability to be honest about his level of skills. I would answer with honesty maybe something like this.


    I have an extensive background in machining but have limited experience grinding. I hope to gain this position and build on my skill set with the training provided by your company.

    This job is beyond my level of that limited experience. That said I would first need to consider the condition of the material and if it is in a soft condition and lends itself to being machined. If it can be machined I would proceed as follows.

    I would rough turn the O.D and I.D in one holding operation leaving an appropriate amount of material for finish grinding and cut it off to size. I might leave it a few Thousands oversize on the length and lap the ends flat.

    The part would then be slid onto a precision mandrel held by a 4th axis indexing head in a milling machine. I would machine all of the details around the part to size.

    (If required the part should then be hardened.)

    After heat treat the part would be mounted using a precision I.D. mandrel and the O.D would be ground to size. I would then carefully hold the part by the O.D and finish grind the I.D.

    That is how I would respond to them. ((Please note)). I have very limited experience with carbides and their conditions. I have machined soft tungsten carbide before. I have no idea if it can be heat treated.

    (It was tough to read the print I may have missed some details)

    I took a shot at helping you. Be honest because if you go into this using a bunch of things guys have said here it's only going to take a question or two that you can't answer to screw things up. Just be strait and if it's to be you will get the job.

    Make Chips Boys !

    Ron

  3. #23
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    Quote Originally Posted by Robert R View Post
    Your part requires electric discharge machining to remove the core of the cylinder and to rough bore the side hole pattern. The OD and ID are finished ground to remove the EDM surface damage and to meet the size, surface finish and roundness specification.. The radial cylindrical and conical holes are finished to size by orbital grinding. . The Diagrind company website has the ID grinding tools.

    The radial holes might also be roughed out with custom made diamond hole saws. That would require a backup mandrel to prevent chipping of the ID surface.

    Most of the grinding work could be done on a Moore jig grinder or it's modern equivalent.

    The print dimensions are too small to read. The strategy for machining might change depending on the overall size of the part.

    I suspect the test question is the equivalent of sending a new hire to the tool crib for a left handed monkey wrench. A knowledgeable new hire might object to being set up to play the fool.
    Thanks for the mention Robert. ID grinding is what we specialize in. As mentioned by another user, grinding carbide with diamond is a cakewalk even compared with grinding steel with CBN. When you decide what tooling you need OP, hit us up at [email protected].


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