How do I machine an internal Hex?

I remember quite some time ago Tom Lipton put up a video where he made some small broachess from HSS tool bits. Used his mill to press the broach through aluminum -- worked pretty good. The broach itself wasn't a typical stepped affair with lots of teeth, but just a single cutting end that had a slightly concave grind to it.

7mm hex isn't that big -- at least I have no problem deforming holes that size all to rat poo when I least want it -- wonder if a 7mm Allen wrench could be pressed (ha ha) into service as a broach? I'm assuming the use will be to make a few wheels, not dozens and dozens.

Just a thought.

-frank

Edit: ah, forgot about the blind hole aspect. Might not work so good.
 
For your project 7mm sockets or cheep nut driver bits.
 
Maybe you can make it in two pieces and weld it together after the shaping.
 
Question: is rotary broaching really tough on your spindle bearings? (If I were to do it on my bridgeport?)
 
Superburban said:
A dremel, small file, and an exacto knife?

A drill press, or careful with a hand drill, you could drill out the corners, then drill/ file/chisel out the center.

Search out some premade inserts?





Its a matter of inventorying your skills, time, patience, and tools.
Click to expand...

Milling works well as long as the corner relief is acceptable which is not always the case, some engineers require a minimum corner radius, a blind hole with a flat bottom and minimum corner radius would require a sinker EDM to produce in metals.
In plastics injection molding will produce such forms.
If doing it for fun just relieve the corners and have at it unless you often send yourself "Non Compliance" letters (-:
 
Lots of good ideas thanks guys! Someone pointed out that depending on how many or few I might make could have a big part of deciding how to do this. I'm thinking about all the suggestions. Jim
 
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