Extending hex broach cut length

[Storm_Eagle]

Hi i have a 8 mm hex broach with a stated max cut length of 25 mm and would like to extend it to 35 mm. My guess is that the max cut length is based on the chips packing in the grooves of the broach. And i was thinking that i can reduce the amount of chips by pre drilling 6 small holes by the corners before drilling the center hole like this:


Would this work to extend the cut length of the broach? And would the 2.5 mm drilled holes be accurate for a 35 mm length when using a center drill first to accurately start the hole?

And no i don't have access to a EDM machine, and don't want to pay a lot of money for a company to wire-EDM this part.

 

[Martin W]

Should definitely help. Like you say, I would be worried a 2.5 mm drill would wander. You would need a very high speed and just peck at the holes. Most small hex broaches I have seen only have 12-13 mm of depth of cut.
Any way to flip the part accurately and broach from both sides?
Martin

 

[Eddyde]

You do didn't mention what the material is?
For the most accuracy, I would start with a spotting drill, not a center drill.
Use a new drill at the appropriate speed for the material. Peck to clear chips frequently, as Martin recommended.
Use lubricant.
IMHO, it would be difficult to withdraw the broach halfway through, in order to broach from both sides. Chips could jamb the teeth and you might break the broach. Also, precise alignment would be an issue.