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Fairly long keyway in bore

Pattnmaker

New member
I am currently currently cutting a replacement fan out of a 4" block of 6061. One of the last things I need to do is put a1/4" keyway in the 15/16 bore. The bore is about 3 inches long. I have been debating on whether to buy a broach and bushing or take it to an occasional customer who has a slotter. I have never used a broach. I just realized this morning a standard bushing may be too short? The other complication is the job is a rush and I had to commit to having it done for Tuesday next week. What's the safest way to put in this bushing as I will have about 40 hours into the part by the time the keyway has to be done?
 

Milland

Active member
We had a thread on this just last month:

Keyway broach 5 - 6 inch long help

If you have a CNC mill, make your own single-tooth slotting cutter and DIY. Take off a 1/2 thou (.01mm) or so each pass, should be a low stress op as long as everything is stable and you make sure your spindle is locked.

Do a practice bore if you're worried.
 

Micmac1

New member
We approach keyways 4 different ways depending on the part. Tight tol stuff goes to a contract broaching shop local to us, smaller nominal stuff we either make a broach bushing for the bore and broach with the arbor press. Bigger stuff we use a right angle milling head, and lastly we grind a hss bit and just use the mill or lathe and lock the spindle. For the sake of time i would either just machine a hss bit or MSC a broach & bushing overnight and do it by hand in a press. Honestly depending on the tolerence even if the standard broach bushing is short it probably would be ok for +/-.005 work as long as the bore fits the bushing well. you can always shim the bushing if the diameter is off.
 

Pattnmaker

New member
Started thinking about using mill as a slotter last night but then thought about the fact its a high speed spindle. And that I don't have time to hand code it. Called a local wire shop this morning dropped it off this morning and will pick it up later today.
 

Milland

Active member
Started thinking about using mill as a slotter last night but then thought about the fact its a high speed spindle. And that I don't have time to hand code it. Called a local wire shop this morning dropped it off this morning and will pick it up later today.

That works. Nice to get such a quick turnaround.
 
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