Rotary Broaching question
Close
Login to Your Account
Likes Likes:  0
Page 1 of 2 12 LastLast
Results 1 to 20 of 33
  1. #1
    Join Date
    Nov 2005
    Location
    Saskatchewan, Canada
    Posts
    105
    Post Thanks / Like
    Likes (Given)
    23
    Likes (Received)
    5

    Default Rotary Broaching question

    I am kind of interested in doing some internal & external hexagons. My question is ,can I work the rotary broach off of the lathe tailstock or do I need a totaly different machine to make one of these units operate correctly. Have any small production runs been done sucesfully by you folks. If so, some pros & cons of this device would be appreciated. Have watched some video about this device & looks quite interesting. Thanks in advance for your shared opinions & advice.

  2. #2
    Join Date
    Jun 2006
    Location
    Taylorsville Ky
    Posts
    3,122
    Post Thanks / Like
    Likes (Given)
    0
    Likes (Received)
    38

    Default

    The only rotary broaches I have seen are for cutting a keyway in a bore. I don't know of any that cut an internal hex or will even go in an internal hex.

    The rotary broaches are driven by the spindle of the mill and since the tailstock quill does not spin you can't use one in the tailstock.

  3. #3
    Join Date
    May 2002
    Location
    South Central PA
    Posts
    14,591
    Post Thanks / Like
    Likes (Given)
    2829
    Likes (Received)
    4325

    Default

    It will work fine in a tailstock. It might be handier to mount it in a toolholder on your toolpost so you can use the power feed of your carriage.

  4. #4
    Join Date
    Dec 2000
    Location
    Bremerton WA USA
    Posts
    10,718
    Post Thanks / Like
    Likes (Given)
    41
    Likes (Received)
    4436

    Default

    These people seem to have the Injun sign on rotary broaching:

    http://www.slatertools.com/

    Their stuff is expensive but they offer tooling that does internal hexes, 12 point driving recesses, internal splines and keys, solid keys, etc. Simply add money. As I understand it, rotary broaching requires axial force to feed it and centering for the tool: a tool post mount may be a good idea if size control is important. A little radial offset to refine the size and all that.

  5. #5
    Join Date
    Mar 2005
    Country
    UNITED STATES
    State/Province
    Indiana
    Posts
    6,008
    Post Thanks / Like
    Likes (Given)
    2062
    Likes (Received)
    2047

    Default

    Yes, it will work fine as long as you can hold it in the tailstock. Carl must be unfamiliar with the rotary broaches that you are thinking about using. Google Slater or Somma for more info. The power feed method Mud mentioned using the tool post will make the tools last longer as well as give a more uniform finish.

    I have done a few small runs (10-20 parts each) of 1/2" and 5/8" internal hex parts with mine and had no problems whatsoever using the tailstock. Look on Slater's site for speed and feed info. I can't really think of any cons to the process other than high initial cost of the broach holder. I solved that problem by scoring mine on Ebay a few years ago for about $80 with a 5/8" hex broach.


    Edited to add: Forrest got in a reply while I was in the middle of typing my reply. Quick draw, buddy.

  6. #6
    Join Date
    Feb 2005
    Location
    Hatch, NM Chile capital of the WORLD
    Posts
    9,661
    Post Thanks / Like
    Likes (Given)
    16369
    Likes (Received)
    11766

    Default

    Ekretz, you stole it, those suckers are expensive. Not really all that complicated, but expensive.

    A bit back had several runs of 3/8" 12 point external hexes in 17-4 to do. Went the Slater route. What I remember is that it took a LOT of force. Blew up the power feed on a big old southbend. Switched over to an old clausing, 16X60 or so, blew the powerfeed up on the carriage, then blew the power feed on the turret(it had a turret instead of a tailstock). I think it was just sheared keys, didn't care, then sold 'em.

    Ended up using almost 3ft long cheaters on the handles for the turret. I don't know if it was the material or that a 12 point hex takes a lot more force than a 6 point, but after running 1700 of them suckers, I was SORE and the cheaters were bent.

    I would say that you are better off with the tailstock, but no special equipment required, its really a very simple process. Be aware that it does take a bit of force. I know Slater has the #s and formulas in their catalog, I certainly wouldn't try it on a mine lathe.

    Cons, On long lengths your form will twist a tiny bit, and you need some place for the chips to break off. So you need a groove, either internally or externally depending on what you are doing, though I have seen some socket heads that just mashed the chips into the bottom of the hex, they worked, I was happy.

  7. #7
    Join Date
    Dec 2002
    Location
    Pacific NW
    Posts
    5,228
    Post Thanks / Like
    Likes (Given)
    8
    Likes (Received)
    938

    Default

    As Bobw says, it takes a considerable force to do certain shapes. I've had a couple hex broaching runs in small diameter 12L14, the air collet closer on the 5C collet in my small CNC couldn't hold the bar stock from pushing back because of the broaching force.

    You guys do know you can make the heads yourself, don't you? Not a major machining project.

    The internal broaches can be ground yourself with an indexing head on a T&C grinder. The biggest hassle is finding metric drill rod for the blanks.

    It's also possible to rotary broach without the fancy head. Make the broach with a tailstock center in the back end. Offset your lathe tailstock so the broach body is at about a 1 degree angle offset (or is it 2 degrees?). However much offset, it's a bit leas than the relief angle on the broach cutting end itself. Screw the tailstock in to feed.

  8. #8
    Join Date
    Aug 2002
    Location
    West Unity, Ohio
    Posts
    27,355
    Post Thanks / Like
    Likes (Given)
    7759
    Likes (Received)
    9549

    Default

    I have done many parts this way, but they have all been on "automatic" equipment, so I kant attest to the thrust needed. ???

    I have only done internal hex and "Dbl D" forms. The 12 points must push harder? Of course I have only done it in 1200 series LCS as well as brass, so the material diff will Shirley change things up as well...

    I had a special app where I needed to cross drill perp into the hex, so I needed to time the broach. This proved to werk OK via the method that they show for use on a turret lathe and such, but was a bit more daffycult in an automatic app, but I got there. However the small holder just couldn't handle the extr grief that it placed on it for long and died a cpl times I think. ??? I ended up making my own out of REAL bearings. The new unit is about 6-8 times as big and doesn't fuss at all.

    Yes on the 1* angle. (That would be 2* incl)

    Sometimes I make my own broaches as needed. But I don't use drill rod and if I can grind the broach to size - I Shirley oughtta be able to spin down the shank eh? A drill blank or even a dowel pin will werk in a pinch. (Pending on material to be broached I guess...)

    If you can install in your tailstock - IMO that would be ideal.



    ---------------------

    Think Snow Eh!
    Ox

  9. #9
    Join Date
    Sep 2002
    Country
    UNITED STATES
    State/Province
    Arizona
    Posts
    3,996
    Post Thanks / Like
    Likes (Given)
    1029
    Likes (Received)
    604

    Default

    Quote Originally Posted by Doug View Post
    ...
    You guys do know you can make the heads yourself, don't you? Not a major machining project.
    ...
    The internal broaches can be ground yourself with an indexing head on a T&C grinder. The biggest hassle is finding metric drill rod for the blanks.
    ...
    Doug,

    I would like to hear more about your shop-made rotary broaches. Could you post a sketch of what you do? What bearings do you use?

    McMaster-Carr has hardened drill blanks in metric sizes. Just search for drill blanks, the metric blanks are hidden in with the decimal sizes. Go to the bottom of the page and open the diameter drop-down, then scroll towards the bottom. They have blanks from 1 to 30mm; 0.05mm increments below 6.30mm; 0.10mm increments below 13mm.

    Cal

  10. #10
    Join Date
    Jun 2006
    Location
    Taylorsville Ky
    Posts
    3,122
    Post Thanks / Like
    Likes (Given)
    0
    Likes (Received)
    38

    Default

    Yep, that's not the rotary broach I am familiar with. The only one I know about are the type to cut a keyway in a blind hole.

  11. #11
    Join Date
    Dec 2002
    Location
    Pacific NW
    Posts
    5,228
    Post Thanks / Like
    Likes (Given)
    8
    Likes (Received)
    938

    Default

    Quote Originally Posted by Cal Haines View Post
    Doug,

    I would like to hear more about your shop-made rotary broaches. Could you post a sketch of what you do? What bearings do you use?

    .................................................. .................

    Cal
    Sorry, I kind of misled you. I didn't make my broaching heads. But, I had a friend who made a couple. His were used for some serious broaching, 1/2" hex in pre-hardened steel. They ran in a big CNC lathe.

    He used angular contact bearings to take the thrust, nothing special. My Somma heads have had good use, the bearings are still very tight. Actually, they feel tighter than I would expect. After a few hours running the heads get slightly warm to the touch.

    The factory units probably have proprietary bearings. They're fairly small diameter to be using a standard bearing.

  12. #12
    Join Date
    Dec 2003
    Location
    Palo Alto, CA USA
    Posts
    985
    Post Thanks / Like
    Likes (Given)
    61
    Likes (Received)
    298

    Default

    My Hardinge clone seems plenty beefy enough to broach in 12L14, although 3/8" hex is the biggest I've done. Here I'm using my shop-made 9/32" hex bit in the tailstock to eat a .63" deep hole in one of 20 little banjo wrenches I made a while back:


    No problem holding the stock with the regular lever collet closer.

    I've made a few bits for my eBay Slater rotary broach, using my characteristically "offhand" kind of technique.

    Here's one I made from the back end of a burnt end mill on my little Sanford surface grinder, using a hex collet block to hold it:






    For what it's worth I posted the process on my HomeShopTech site:

    http://www.frets.com/HomeShopTech/To...achmaking.html

  13. #13
    Join Date
    Aug 2006
    Location
    Hesperia, SoCal
    Posts
    4,362
    Post Thanks / Like
    Likes (Given)
    987
    Likes (Received)
    657

    Default

    Alright Ox, we can handle your spelling but, "I ended up making my own out of REAL bearings. The new unit is about 6-8 times as big and doesn't fuss at all. " with no pics, is going too far!

    Bob

  14. #14
    Join Date
    Aug 2002
    Location
    West Unity, Ohio
    Posts
    27,355
    Post Thanks / Like
    Likes (Given)
    7759
    Likes (Received)
    9549

    Default

    OK - lets werk this out....


    Take that little putzy one that you have.

    Hold it in your left hand with the shank end pointing to your right hand.

    Are you with me?



    Got it?



    Now - multiply everything times a factor of 6 or 8.

    Hey - Watchit! - it gets heavy! DON'T DROP IT!

    Sorry bout'cher toe. I should'a warned you first. My bad....




    What? You don't believe me?


    I think I have some 2-1/2" prox bearings in it. They were whatever I could scroung up in a chumms misc bearings box one weekend.... I made the holder to fit the bearings. Not the other way around. Eny bearing will werk.... (Unless you install backwards - then that can git bad inna hurry...)


    With all that said - a bigger than needed one is not really recommended as the trq required to spin it will yield the helical form as mentioned above. As I said - in this application I was driving off the spindle to keep it in time.

    ------------------

    Think Snow Eh!
    Ox
    Last edited by Ox; 07-11-2009 at 01:21 PM. Reason: edit

  15. #15
    Join Date
    Mar 2009
    Location
    Centerville, TN USA
    Posts
    338
    Post Thanks / Like
    Likes (Given)
    4
    Likes (Received)
    6

    Default

    Ox, I have a good laugh at you every day on here!

    Now I gotta go bandage my toe up...

  16. #16
    Join Date
    Aug 2002
    Location
    West Unity, Ohio
    Posts
    27,355
    Post Thanks / Like
    Likes (Given)
    7759
    Likes (Received)
    9549

    Default

    Well look at it this way Mr. Power. THEY say that:

    A) Pain is temporary

    B) Chicks dig scars.

    B1) Not exactly sure who's lookin at'cher hoof, so you may need to hang by the pool for this one to help much.


    C) What doesn't kill yuh only goes to make yuh stronger.

    C1) After a healing spell of course.



    Wifeys camera was out here enyway - so I went ahead and took a cpl shots of it for you. You'll be surprised to find that it looks a lot like a rotary broaching unit. LOL! Will post pics whenever she feels like downloading them...


    ------------------

    ***My intentions are good***
    Ox

  17. #17
    Join Date
    Dec 2003
    Location
    Palo Alto, CA USA
    Posts
    985
    Post Thanks / Like
    Likes (Given)
    61
    Likes (Received)
    298

    Default

    Quote Originally Posted by Ox View Post
    Well look at it this way Mr. Power. THEY say that:

    A) Pain is temporary
    Well, it seems THEY never:

    A) Had arthritis.

    B) Lived with my ex-wife.

    C) Met some of my more, er, "select" cutomers.

  18. #18
    Join Date
    May 2002
    Location
    South Central PA
    Posts
    14,591
    Post Thanks / Like
    Likes (Given)
    2829
    Likes (Received)
    4325

    Default

    Quote Originally Posted by frank ford View Post
    well, it seems they never:

    A) had arthritis.

    B) lived with my ex-wife.

    C) met some of my more, er, "select" cutomers.
    LOL ! :d
    ...

  19. #19
    Join Date
    Aug 2002
    Location
    West Unity, Ohio
    Posts
    27,355
    Post Thanks / Like
    Likes (Given)
    7759
    Likes (Received)
    9549

    Default

    I believe that "They" were in reference to his toe injury. It will heal quickly enough. Those other things .....



    Shaft is 1.5" Dew can for ref.










    ---------------------

    Think Snow Eh!
    Ox

  20. #20
    Join Date
    Mar 2009
    Location
    Centerville, TN USA
    Posts
    338
    Post Thanks / Like
    Likes (Given)
    4
    Likes (Received)
    6

    Default

    Me Likey!!!

    DieselPower goes to his PowerTurn for the morning...Hopes to have something similar ina few hours...


Bookmarks

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •