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Thread: Lathe bore to small for stock need to turn ends Help?

  1. #1
    Join Date
    Nov 2010
    Location
    Portland Oregon
    Posts
    570

    Default Lathe bore to small for stock need to turn ends Help?

    Hello Group,
    A friend has called and wants me to turn down the ends to .75 on a piece of 1"CRS 36" long. I know I've seen the answer before but for the life of me I can't remember what it is or if it's possible. I have a SouthBend 9A lathe 48" bed, steady rest, follow rest, lathe dog the correct size, flat plate, 4jaw, 3jaw.
    Look forward to your help..

    TX
    Mr fixit for the family
    Chris

  2. #2
    Join Date
    Aug 2010
    Location
    Flint, Michigan
    Posts
    579

    Default

    Chris, this is the right job for the steady rest. The 3 jaw is fine to hold the headstock end even if a few thousandths out of true, because the work will be done at the steady rest. First chuck the stock and support the outboard end with something. Set the steady rest to the shaft at the chuck so the jaws are firmly fitted but not tight. Move the steady to an inch from the end and bolt in place. Machine that end to size. This is when you would drill a center hole if you were later going to mount the piece between centers. Reverse the stock and cut the other end.

  3. #3
    Join Date
    Jun 2016
    Location
    Western North Carolina, USA
    Posts
    170

    Default

    Sounds like dead center, flat plate, and dog on drive end with live center at tail to me, but depending on how far from the ends you are cutting might need steady rest I guess. Cut next to the live tail center, then flip bar and put dog on the freshly cut.75 end and cut down the remaining 1" end now at the tail live center. Hard to go too far off axis as long as you stay close to the live center in the tail stock.

  4. #4
    Join Date
    Oct 2013
    Location
    USA MD 21030
    Posts
    3,700

    Default

    Follow rest might be better:








  5. #5
    Join Date
    Jan 2004
    Location
    Independent principality of Sinquefieldia (formerly Missouri in the USA)
    Posts
    24,642

    Default

    Do you have a 48" BED, or do you have 48" BETWEEN CENTERS?

    If the BED is 48", I think it is just not happening. If you have 48" between centers, then the steady is what you need to use.
    1601

    Keep eye on ball.
    Hashim Khan

  6. #6
    Join Date
    Aug 2011
    Location
    Central Virginia, USA
    Posts
    351

    Default

    Your lathe is too short. SB specs are bed length, not between centers length. You will be unable to use your tailstock. So, you will need a steady rest, and probably take the right side leadscrew hanger off so you can let the saddle hang part way off the end of the bed. I've done it, but light cuts were the order of the day.

    allan

  7. #7
    Join Date
    Jan 2013
    Location
    SW. Michigan
    Posts
    836

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    Quote Originally Posted by Mr Fixit View Post
    Hello Group,
    A friend has called and wants me to turn down the ends to .75 on a piece of 1"CRS 36" long. I know I've seen the answer before but for the life of me I can't remember what it is or if it's possible. I have a SouthBend 9A lathe 48" bed, steady rest, follow rest, lathe dog the correct size, flat plate, 4jaw, 3jaw.
    Look forward to your help..

    TX
    Mr fixit for the family
    Chris
    I recommend you try taking a basic course to run a lathe

  8. #8
    Join Date
    Nov 2007
    Location
    Woodinville, WA
    Posts
    7,851

    Default

    Find someone local that can pass the 1 inch though the head stock. If you are over this side of the mountains, I'd do it in 30 seconds.

  9. #9
    Join Date
    Oct 2002
    Location
    Saskatoon, Saskatchewan
    Posts
    2,329

    Default

    I've reduced the diameter approximately 1/8" for about 8" on the ends of a (roughly) 5 1/2 foot (or so) long by 1 5/8" shaft using my 9" South Bend so it's doable...depending on just how close to 3/4" the ends have to be. Pesky tolerances, eh? It was made a little more difficult because the shaft was the rear axle axle out off my old Canada Ingot horse drawn grader and it had a good 1 1/2" bow in it from decades of use.

    I used a four jaw chuck to grab about 1/4" of an end of the shaft, a steady rest at the end of the bed and had at it at an rpm that didn't shake the lathe too bad...the outboard end was making quite a circle in mid air. Once I had as much turned down as possible I used a grinder to take the bit under the chuck jaws down to close to finished size and then I simply filed the rest down paying attention that I didn't remove too much stock. Took awhile though.

    That being said, I'd advise finding someone with a lathe that will pass a 1" rod through the spindle.

    Another way to do it is if you have a milling vise setup that attaches to the cross slide for your lathe and a boring head with a MT3 taper, clamp the shaft in the vise, center it on the spindle and then use the boring head to reduce the end
    Last edited by Arcane; 07-17-2016 at 09:39 PM.

  10. #10
    Join Date
    Nov 2008
    Location
    SF East Bay.
    Posts
    4,083

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    Quote Originally Posted by lakeside53 View Post
    Find someone local that can pass the 1 inch though the head stock. If you are over this side of the mountains, I'd do it in 30 seconds.
    There was someone who did an interesting trick. They welded a smaller piece to the end and chucked it up. Supported the far end in a steady rest. Then they turned down the original bar and parted it. Rotate and repeat.

    Dan
    Measure twice. Cut once. Weld. Repeat.
    ( Welding solves many problems.)

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