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Boring offset hole on a lathe

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  • Boring offset hole on a lathe

    I need to bore an 8mm hole in a piece of 1018 cold rolled steel, .25"x.5"x3". The hole is located 6mm from the end (on the .5" side). I only have a 3 jaw chuck on my Logan 400 lathe. The jaws aren't replaceable, so I can't make soft jaws. Anyone have suggestions for a fixture or other method for this?

  • #2
    Drill a 1/4 hole thru plate in correct position. Drill 1/4 hole in 1/2 or bigger bar. Insert 1/4 rod thru plate and into bar, weld bar to plate, now pull rod mount in lathe with enough swing.. and bore hole, ..now grind off bar from back of plate.

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    • #3
      That would work if I had a welder 😀

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      • #4
        Face plate mount..?

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        • #5
          How close is the required hole position?

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          • #6
            Originally posted by elf View Post
            I need to bore an 8mm hole in a piece of 1018 cold rolled steel, .25"x.5"x3". The hole is located 6mm from the end (on the .5" side). I only have a 3 jaw chuck on my Logan 400 lathe. The jaws aren't replaceable, so I can't make soft jaws. Anyone have suggestions for a fixture or other method for this?
            Drill press? I don't see this as a lathe job. Am I missing something with this suggestion?

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            • #7
              Likewise, I don't see this as a job for a lathe either. I see the piece as 1/4" thick X 1/2" wide X 3" long. Am I also missing something? Also the hole is suppose to be 6mm from the 1/2" end. This has drill press or mill written all over it.
              Last edited by nc5a; 06-13-2020, 08:39 PM. Reason: added explaination

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              • #8
                An excellent exercise in lathe work holding for a home shop machinist.

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                • #9
                  That is a nice rendering of the design. This piece is part of a horizontal cutting frame for a rose engine. The hole is for a bearing. My 8mm Chinese special reamer makes an oversize hole.

                  Here's an image of the full design:
                  Click image for larger version

Name:	MF104zz.JPG
Views:	351
Size:	43.4 KB
ID:	1881138

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                  • #10
                    Originally posted by elf View Post
                    That is a nice rendering of the design. This piece is part of a horizontal cutting frame for a rose engine. The hole is for a bearing. My 8mm Chinese special reamer makes an oversize hole.

                    Here's an image of the full design:
                    Click image for larger version

Name:	MF104zz.JPG
Views:	351
Size:	43.4 KB
ID:	1881138
                    Buy a .314" reamer and be done with all of the parts in a short time.
                    https://www.mscdirect.com/browse/tn/...128+4288051783

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                    • #11
                      If you have a boring head, jold it in 3 jaw chuck, clamp bar in tool post .

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                      • #12
                        clamp it to the tool post & use a boring head? might have to build the boring head first but there was just a thread on that

                        great minds and all that 754
                        --
                        Tom C
                        ... nice weather eh?

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                        • #13
                          layout, prick punch, centre punch and hand drill if you don't a drill press. Another way in the lathe that you don't see much anymore is a pad in the tailstock and the drill in the chuck.

                          ooops ...didn't realize the objective was single pointing it to size. Drop by and I'll ream it for you?
                          in Toronto Ontario - where are you?

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                          • #14
                            I like to have some small adjustable reamers on hand, then you can drill or ream 5/16 , then open it up..
                            the other thing to try, drill or ream 5/16 hole in a scrap piece, then try to ream 8 mm. It may stay closer to size.
                            FWIW loctite can easily take up 2 thou or more.. , just have to wait for it to set up.before use.
                            Last edited by 754; 06-13-2020, 11:37 PM.

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                            • #15
                              Make yourself a jig that will be so handy for future things of this type. Start by cutting out a triangle from 1/4 inch plate or flat bar. The size should be such that when you open your three jaw most of the way, it will fit in the jaws. Then make a second plate that's larger. Bolt them together through the tips of the smaller triangle (you might want spacers at these three spots), and then insert it into the chuck. Mark the position to match your chuck so you can always put it back the same way. You can then drill through the front plate as required for hold down bolts, to hold things like your project. You might use countersink bolts so you can put a hole anywhere without interfering with the jaws.

                              When you mount it for the first time, face it and trim whatever OD on it to make it safe. If your larger plate is a circle, you'll be turning the whole OD. If it's triangular, you'll just be trimming the tips.

                              When you're using it, recognize that you may be swinging a large imbalance. Bolt on an opposing weight if need be.
                              I seldom do anything within the scope of logical reason and calculated cost/benefit, etc- I'm following my passion-

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