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Thread: Rotary Broach

  1. #31
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    Kent, U.K.
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    I think that it would be defined by depth of broaching and the relief angle on the broach. Sooner or later you're going to thin the base of the stem until it's too weak.
    Peter - novice home machinist, modern motorcycle enthusiast.

    Denford Viceroy 280 Synchro (11 x 24)
    Herbert 0V adapted to R8 by 'Sir John'.
    Monarch 10EE 1942

  2. #32
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    Apr 2012
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    Quote Originally Posted by DennisCA View Post
    Here's a video showing how to build the hemingway kit.

    Thanx for that.
    Added to my Hemmingway-to-buy-list...

  3. #33
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    May 2006
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    It's a little like building a swash plate im thinking... just have to keep in mind some critical angles that have to dissect each other where the bit connects to the work, in fact all bits need to be the same length regardless of diameter...

  4. #34
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    Nov 2007
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    Clovis CA USA
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    The few times I need a hex drive in steel I just heated the bar to drill a hole red hot and drove a hex Allen wrenche
    I use for making a replacement parts.

    It is same way a blacksmith would do the job.

    Some the way the old ways work. The rotory broaching is for screw machine work making thousand of parts in soft metals

    Dave


    Quote Originally Posted by Tungsten dipper View Post
    Just watched this video (Old Tony's) on his new rotary broach. Looks interesting. Do any of you have one, and what are your thoughts? https://www.youtube.com/watch?v=GWyHJVOxKK4

  5. #35
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    Jan 2003
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    Quote Originally Posted by A.K. Boomer View Post
    .................................................. .................................................. .................................................. ................. all bits need to be the same length regardless of diameter...
    If the broaches aren't all the same length then you need the adjustable type. For simple hex and square broaches I ground my own from 8mm M2 drill rod and mine weren't always the same length.

    I'm a little surprised about all the ones that are non-adjustable. Mine are 20 some years old and adjustable, that's all that was sold back in the day. It's so much easier to set the tool with adjustments.

  6. #36
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    Jun 2016
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    Quote Originally Posted by DR View Post
    I'm a little surprised about all the ones that are non-adjustable.
    I don't think there is anything surprising about it. You buy a toolholder from Company A, and then you buy individual broaches from Company A so that they are the correct length. It's a good business plan.

    It's so much easier to set the tool with adjustments.
    Quite the opposite; it's easier when there are no adjustments to make.

  7. #37
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    Quote Originally Posted by tomato coupe View Post
    I don't think there is anything surprising about it. You buy a toolholder from Company A, and then you buy individual broaches from Company A so that they are the correct length. It's a good business plan.

    Quite the opposite; it's easier when there are no adjustments to make.
    I have to ask, how many times have you setup a rotary broach head? Conservatively, I'd say I might have done it 50 times over 25 years (I had 3 customers with repeat orders of broached parts).

    It is a fact, Slater and Somma did not make non-adjustable heads when I was buying mine. The first non-adjustable head I recall on the market was for very high dollar Swiss style screw machines.

    I had a local tool grinding shop make a number of the broaches we used, those were custom eight point squares, way less expensive and far, far quicker delivery than buying from Slater or Somma. Buying from other than Slater was a great business plan. For easy to grind hex or square we did them ourselves on the tool and cutter grinder. Sometimes we'd re-dish the end to sharpen and/or tighten size of broached hole. There is no guarantee they'll be all the same length.

    What about using the attachment in a lathe tailstock? Ever have a lathe where the tailstock quill was a bit below center? Our broaching was done either on gang tooled or turret CNC lathes. In a perfect world the round tool holders would always be on center, in reality they aren't and dialing them in is a pain. With the adjustable type you loosen the adjusting screws, jog the tool tip into to the chamfer on the part and let it self center as you gently hand rotate the lathe spindle, tighten screws.

    It's kind of stupid to argue about this, from experience the adjustable have prove to be much easier to use,
    Last edited by DR; 08-08-2019 at 08:38 PM.

  8. #38
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    Jun 2016
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    Quote Originally Posted by DR View Post
    I have to ask, how many times have you setup a rotary broach head?
    I use mine several times per year.

    What about using the attachment in a lathe tailstock? Ever have a lathe where the tailstock quill was a bit below center?
    I never use mine in a tailstock. But, if I did, it wouldn't matter as my tailstock is on center.

    Our broaching was done either on gang tooled or turret CNC lathes. In a perfect world the round tool holders would always be on center, in reality they aren't and dialing them in is a pain.
    All my gang tooling is at the same height as the spindle. All you have to do is enter the x and z offsets, like you do with any other tool.

    With the adjustable type you loosen the adjusting screws, jog the tool tip into to the chamfer on the part and let it self center as you gently hand rotate the lathe spindle, tighten screws.
    You just skip those steps with the non-adjustable type.

  9. #39
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    Sep 2015
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    NW Illinois
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    Quote Originally Posted by sandiapaul View Post
    Any ideas what the smallest practical square or hex hole you could make with one of these?
    I made a 1/8" square broach to go 1/2" deep in brass. I figured the neck would be to slender and prone to breaking if I used the normal 2* clearance. I used 1 1/2* clearance. It worked well.

    Several years ago I worked on a job that required a 3/4" hex in a blind hole. We bought a punch of the proper size and rammed it in with a hydraulic press.

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