Broaching a hex hole 2

[agpowder]

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?.

 

[handleman]

Sinker EDM, assuming a conductive material.

-handleman, CSWP (The new, easy test)

 

[tripleZ]

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.

 

[MikeHalloran]

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

 

[hydtools]

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

Ted

 

[arunmrao]

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
_____________________________________

 

[DesignerGuy16]

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

 

[ornerynorsk]

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.

 

[bvanhiel]

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

 

[limey1]

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?

 

[agpowder]

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.

 

[ajack1]

This might help

http://www.slatertools.com/rotary_broaching.htm

 

[SincoTC]

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!

 

[griffengm]

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

Griffy

 

[ornerynorsk]

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

 

[GregLocock]

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

SIGlease see FAQ731-376 for tips on how to make the best use of Eng-Tips.

 

[unclesyd]

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

 

[HDS]

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.

 

[europipe]

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

 

[drawoh]

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