×
INTELLIGENT WORK FORUMS
FOR ENGINEERING PROFESSIONALS

Log In

Come Join Us!

Are you an
Engineering professional?
Join Eng-Tips Forums!
  • Talk With Other Members
  • Be Notified Of Responses
    To Your Posts
  • Keyword Search
  • One-Click Access To Your
    Favorite Forums
  • Automated Signatures
    On Your Posts
  • Best Of All, It's Free!
  • Students Click Here

*Eng-Tips's functionality depends on members receiving e-mail. By joining you are opting in to receive e-mail.

Posting Guidelines

Promoting, selling, recruiting, coursework and thesis posting is forbidden.

Students Click Here

Jobs

Broaching a hex hole
2

Broaching a hex hole

Broaching a hex hole

(OP)
I need some advise on how to broach a hexagon into a BLIND hole. The workpiece is 2" diameter, 22" long and I need to have a 3/4"AF hex Female hole put into both ends about 2" deep. Like a cap head screw. Can anyone advise me on how to do this?.  

RE: Broaching a hex hole

Sinker EDM, assuming a conductive material.

-handleman, CSWP (The new, easy test)

RE: Broaching a hex hole

rotary broach maybe, if you don't mind some distortion on the lead-in.  Although 2" may be a bit long.  I've only read about the process...I've never tried it.

RE: Broaching a hex hole

Broaching a blind hole that deep gives you a big problem; where do the chips go?

EDM solves that problem, at the expense of speed.

Another possibility; through- broach a pair of short cylinders, press them into blind bored holes in the ends of the workpiece, and secure with threaded Dutch pins or plug welds or whatever.



 

Mike Halloran
Pembroke Pines, FL, USA

RE: Broaching a hex hole

Through broach per MikeHalloran suggests.  Then inertia weld three pieces.

Ted

RE: Broaching a hex hole

Can you think of using a shaping machine . the challenge lies perhaps in getting a tool made and securing the job firmly on the machine. Last week I was contemplating of this route for a square hole. EDM is way too expensive and very slow too.  

I have not failed. I've just found 10,000 ways that won't work." — Thomas Edison
_____________________________________
 

RE: Broaching a hex hole

I'm with handleman on this one.  EDM would be the simplest solution.  Isn't all that expensive or hard to do either.

James Spisich
Design Engineer, CSWP

RE: Broaching a hex hole

Is this mass production or a single piece?  Mass production can be done by driving a broach into a pilot hole that is deeper than the hex portion to allow for chip accumulation.  If this is set up correctly, the 6 chips will curl uniformly and compact into the bottom of the hole.   

RE: Broaching a hex hole

Can you bore a larger diameter passed the region that you need the hex?  That would give you someplace for the chips to go.

RE: Broaching a hex hole

Could your piece be made 18" long, then take 2,2" pieces with the 3/4" Hex already in them, then weld them to the workpiece?

RE: Broaching a hex hole

(OP)
Thanks everyone. The EDM route has proved very costly. I have 12 pieces to do right now and then repeating in dribs and drabs over time. I can drill the hole within reason as deep as I like. I can probably increase the bore diameter after the 2" deep bit where the male hex will insert.
From your comments blind hole boring or punching is a method but I have never seen "blind hole broaches or punches" are these available? or would I need to make myself? (BTW if the answer is make myself then I will be asking a whole load of other questions!!)
Assuming they are stuck well I dont mind about the chips remaining in the bottom of the hole.

RE: Broaching a hex hole

agpowder,

A place I worked at used to have a "Polygonal Hole Drilling Attachment"; it made a lot of noise but produced pretty good holes, hexagons were much better and sharper than squares which had slightly rounded corners, but I don't think that they recommended going much deeper than twice the AF distance, so that may rule it out for you.

It was made by Watts Brothers Tool Works in Wilmerding PA and I believe they're still in business, may be worth asking them if they still make them and if they can go deeper now.

I saw a CNC turning centre producing hex holes fairly recently (Dianichi, I think) using a rotary tool in a driven tooling station, so I guess that it's the same principle but without the noisy guide plate!



 

RE: Broaching a hex hole

One other method depending on materials and permissible features might be to swage the form.

Griffy

RE: Broaching a hex hole

Good one Ajack, this is better than conventional blind form broaching on low volume stuff.

RE: Broaching a hex hole

When you say a hexagon, what do you really mean? Would a pilot hole with a diameter greater than the minor dimension be acceptable? alternatively, would a small pilot hole at each apex be acceptable?  

Cheers

Greg Locock

SIG:Please see FAQ731-376: Eng-Tips.com Forum Policies for tips on how to make the best use of Eng-Tips.

RE: Broaching a hex hole

Some very good information taken from the web pages of Holden Ventures LLC. I would give these people a call about your problem.

Blind-hole broaching
Blind-hole broaching violates two broaching principles: the tool does not pass completely through the work piece, and it must be withdrawn backwards over the broached surface. But it can be done when necessary. The job usually involves a series of short push broaches, each slightly larger in diameter than the preceding tool. These short push broaches are mounted on a circular indexing table that rotates under or over the work piece; the broaching machine pushes the work piece over the tool, withdraws it, and then waits for the next broaching tool to index into position.



http://holdenventures.com/BD.aspx

RE: Broaching a hex hole

Buy two deep well impact sockets of 3/4" size and weld them to the ends or your rod. I suggest impact sockets because they usually don't have any plating.

If you need the two inch diameter on the end then press the sockets into a hole drilled in each end. Then weld the exposed ends.

RE: Broaching a hex hole

Can't you drill a hole, tap thread, drill a larger hole with the same diameter as the outside of an inbusbolt and put an inbusbolt in it?
It was just an idea, please don't shoot me.

Greetings

RE: Broaching a hex hole

agpowder,

   My machine tools book dates from the mid-seventies.  It has a section describing a system for drilling square, hexagonal, octagonal and other weird shaped holes.  The photos are courtesy Watts Brothers Tool Works.  

   Try searching Google for Watts Brothers Tool Works, and for Reuleaux triangle.  

               JHG

Red Flag This Post

Please let us know here why this post is inappropriate. Reasons such as off-topic, duplicates, flames, illegal, vulgar, or students posting their homework.

Red Flag Submitted

Thank you for helping keep Eng-Tips Forums free from inappropriate posts.
The Eng-Tips staff will check this out and take appropriate action.

Reply To This Thread

Posting in the Eng-Tips forums is a member-only feature.

Click Here to join Eng-Tips and talk with other members!


Resources