making a Reamer Pilot
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  1. #1
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    Default making a Reamer Pilot

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    I am attempting to make small brass pilots for a gun reamer. I haven't been able to get these small things any better than .0015-0.003" of RO. on my lathe.

    A tool post grinder and Harig Grind all is available to me.

    Can anyone give me some advice on how they would do this type of machining.

    Thank you.

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    First method- The but end on a center or zero indicated in a 4 jaw, with the out end going through a bushing on a straight portion of your reamer that is held in your steady. The steady bushing made with the same reamer.

    Second method- Check the bushing holding shoulder to see it is .0002 or so true. If so put stub in your chuck and turn it the reamer holing shoulder for a light tap-on fit and turn the brass bushing when it is off the reamer.

    Method 3: make two bushings to fit the straight portion of your reamer. Turn the bras bushing on the reamer to +.003. Put the two reamer bushings in a v block with the reamer going through and hand turn under a surface grinder wheel to grind to size..yes you have an end block stop to position.

    *Method 4: See if there is a center at the front of the reamer like the screw hole bevel.. if so put that on your center and check it for dead true. if so light press on the brass bushing and run the brass bushing turning the part (reamer bushing) between centers on the reamer.. yes you need go easy so it does not get hot and turn on the reamer..Make a line up mark and then put in your screw.

    Method 4 likely the best and if the but-end has a center all the better to run the job between centers for dead true job..

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    Quote Originally Posted by coyotebgone View Post
    capture.jpg

    I am attempting to make small brass pilots for a gun reamer. I haven't been able to get these small things any better than .0015-0.003" of RO. on my lathe.

    A tool post grinder and Harig Grind all is available to me.

    Can anyone give me some advice on how they would do this type of machining.

    Thank you.
    Do all your turning, without taking the part off the parent stock, until you have all the dimensions as you need.

    By doing all your turning in a single set-up, you eliminate any need to re-align and center up the part.

    Drill the hole undersized, and bore it. Drills wander. Reamers follow the drill, so drilling and then reaming will get you a hole that is pretty much the right size, but not always centered. If you cannot be bothered to bore to actual size, at least bore the drilled hole to get it centered, so the reamer has half a decent chance to stay centered. But if you are boring it anyway...

    Once you have a true running hole in the middle, then turn your OD to size.

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    You might look at your checking process and the places supported as you check it. Then use those same places to hold it as you lathe turn the bushing.

    Turning a stub coming out of your chuck that would act as a mandrel to hold the bushing as you turn it to size should get you to .0000/.0002 close..but you have to consider the slight expansion with tapping part (bushing) onto the mandrel when sizing the OD.Yes this for turning the bushing when it is off the reamer. Take light cuts so not heating it up to go lose.

    Yes you consider how to get the bushing off the stub , perhaps making a flat or a small step diameter so a puller or device to push it off the stub.

    When you turn a stub it is dead true /straight as long as you leave it in the machine. Taking it out and putting it back it is no longer true.

    It is near impossible to start a drill hole dead center as if in make the bore and then parting it off.
    I used to tool-bit mark a drill spot before starting the drilling/still .0005 and better close was not always possible ..Perhaps I never had a perfect lathe or perfect drill.
    Boring a hole makes one true/and straight..as long as you hold the part OD and ID perfect so true to each other..Boring and skim turning OD then parting off make a true part, the error is left in the chuck or collet.

    We used to make true reamers with grinding a point at the out end and use that for a male center. Then after it done we would snub off that point.
    Yes the most common reamers we made had center at both ends.

    The very best reamer are back-spun for the last .0005 or so.

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    Quote Originally Posted by michiganbuck View Post
    You might look at your checking process and the places supported as you check it. Then use those same places to hold it as you lathe turn the bushing.

    Turning a stub coming out of your chuck that would act as a mandrel to hold the bushing as you turn it to size should get you to .0000/.0002 close..but you have to consider the slight expansion with tapping part (bushing) onto the mandrel when sizing the OD.Yes this for turning the bushing when it is off the reamer. Take light cuts so not heating it up to go lose.

    Yes you consider how to get the bushing off the stub , perhaps making a flat or a small step diameter so a puller or device to push it off the stub.

    When you turn a stub it is dead true /straight as long as you leave it in the machine. Taking it out and putting it back it is no longer true.

    It is near impossible to start a drill hole dead center as if in make the bore and then parting it off.
    I used to tool-bit mark a drill spot before starting the drilling/still .0005 and better close was not always possible ..Perhaps I never had a perfect lathe or perfect drill.
    Boring a hole makes one true/and straight..as long as you hold the part OD and ID perfect so true to each other..Boring and skim turning OD then parting off make a true part, the error is left in the chuck or collet.

    We used to make true reamers with grinding a point at the out end and use that for a male center. Then after it done we would snub off that point.
    Yes the most common reamers we made had center at both ends.

    The very best reamer are back-spun for the last .0005 or so.
    That's sure a convoluted and roundabout way of accomplishing a simple BRASS bushing, per what the OP is wanting to make.

    If you do all the critical dimensions (ID, OD, and one reasonably square edge) in a single setting, it does not matter if you use a collet, a six or three jaw chuck, or simply wedge the stock into the headstock bore so it can't move.
    By turning all in one set up, the accuracy is pretty much down to the possible misalignment of the carriage travel to the center of the axis of rotation of the headstock, and the tolerences and proper setup of the headstock spindle bearings.

    Any time a part has been removed and replaced in any form of work holding, is an opportunity to get it even worse than it has to be. Even the best made mandrel is still just one more place it can go wrong.

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    The ops reamer has a screw at the out end so not going to rest on the tail center if running the bushing on the reamer.
    Putting the reamer shank end in a collet likely will not make the far out end run true if some how not held.
    Looks like the reamer is already made and the Op is trying to make the brass bushing to go on the end...and make it to run true.
    If there is a center under that screw then the reamer holding the bushing might be run between centers.
    looks like he is getting .0015 to .003 error now. I don't think he said how he is doing it.

    *But I do agree if the bushing hole is made dead center and he skims the OD in one holding of the part and then parts it off it will be good/true and straight. Ye, this just doing the bushing alone.. That is why I said he might tool-bit scalp the drill hole ..or bore the hole so it will be center..Agree held in any chuck or collet.
    Last edited by michiganbuck; 01-19-2020 at 08:35 AM.

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    The op’s bushing with running out .0015 to .003 will try to start the reamed bore to cut way over-sized or lock up in the bore and try to cut the chamber not on the bore center. It should run .0002 or better close ID to OD. Op does not say it is a live pilot or solid. Also does not say his choosing for pilot clearance. Seems some smiths like .0002 and others .001 and better.

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    Quote Originally Posted by michiganbuck View Post
    The ops reamer has a screw at the out end so not going to rest on the tail center if running the bushing on the reamer.
    Putting the reamer shank end in a collet likely will not make the far out end run true if some how not held.
    Looks like the reamer is already made and the Op is trying to make the brass bushing to go on the end...and make it to run true.
    If there is a center under that screw then the reamer holding the bushing might be run between centers.
    looks like he is getting .0015 to .003 error now. I don't think he said how he is doing it.

    *But I do agree if the bushing hole is made dead center and he skims the OD in one holding of the part and then parts it off it will be good/true and straight. Ye, this just doing the bushing alone.. That is why I said he might tool-bit scalp the drill hole ..or bore the hole so it will be center..Agree held in any chuck or collet.
    He is actually trying to make the pilot bushings, and you are trying to make it very much more complicated than it has to be. A LOT more.
    Maybe you have seen replaceable non-rotating pilots on reamers, but I can say, I never have. Any I have seen with a screw in the end, were MEANT to rotate.

    The very LAST thing he needs, is to be dicking around with trying to move the bushing from the parent stock at any time before he is ready to part it off.

    Nor is he going to 'run the end of the reamer on a center'. It's a pilot for a chambering reamer, so it does actually need to be reasonably concentric, and with the runout he claims, and without any idea how he managed to get it so bad, the best option I see, is to do all the Ops in one set, then part off the far end. That end can go towards the screw, where it won't even sit crooked on the reamer, if it somehow gets buggered up.

    He posted pictures of the pilot bushing he intends to replace.

    It doesn't matter what his intended clearance is, he wasn't asking that. He wants to know how to make the inside and the outside, concentric.

    My best guess is that he did what pretty much every guy new to lathe stuff does, stuck a drill into the stock, then reamed the hole, and called it good and moved on through the process. That works great for making steel spacers for a welding project, but not so much for when the concentricity counts.

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    Quote Originally Posted by michiganbuck View Post
    Trev, then give the op step by step advice of how to make the part.
    I did. It's in the third post of this thread.

    He wants, as I understood his post, information on how to accurately make replacements for the pilot bushings for his chamber reamers.

    Drill undersize, bore to size the ID. Turn the OD. Part off to length. Deburr. No dicking around with mandrels, centers, or any other tooling.

    All done in one operation, so it does not matter if the stock is held in a 3jaw, in a well centered 4jaw, in a collet, or wedged into the lathe bore with sticks of kindling, as long as it does not move until it is removed on purpose.

    You remind me of a Maths Teacher I once had. He was so good at the stuff, he had no concept of how to explain it to those who were not as good as he was.

    Great mathematician. Lousy teacher.

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    Guess you are right Trev
    I have made chamber reamers and other reamers by all the methods I mentioned.
    Keep it simple is likely the best teaching...Your post #3 does that.

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    Quote Originally Posted by michiganbuck View Post
    Guess you are right Trev
    I have made chamber reamers and other reamers by all the methods I mentioned.
    Keep it simple is likely the best teaching...Your post #3 does that.
    At risk of turning this in to a mutual admiration society meeting, thanks.

    I was scratching my head, trying to work out what you were trying to convey. Like as not, if the fella was confused trying to get a brass bushing made, he was REALLY confused by the time we were done with him.


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