Drilling for coolant through pull studs

mtlhe · May 14, 2017

Our new VMC has through coolant spindle. All of our Cat40 holders have Haas pull type studs. Rather than replacing all of them could we just remove them and drill the hole. A quick look on Maritools site shows the Haas coolant through stud has a .200" hole w/ a chamfer. Anyone done this before? Recommendation on the drill type(HSS,Cobalt,Carbide)?

Milland · May 15, 2017

I'd buy the correct studs, a broken stud can quickly ruin your day while it ruins your spindle taper and/or bearings.

If you must drill your own, use a Hi-Roc or similar carbide drill, then ream with a carbide reamer to a little smaller size than commercial standards (leave a little more meat). Use the bore cycle to feed in and out, you want the best finish possible to minimize fatigue cracking risks. Best would be to leave the bore a thou or so undersize, then ballize with a carbide bearing ball pressed through the hole (with lube) to compress and smooth the bore.

M.A. Ford - Product Lines

Ballizing, ball burnishing with tungsten carbide balls | ITI Ball

tnmgcarbide · May 15, 2017

a coolant pull stud costs about $10 , a spindle repair starts at $1000.

the carbide drill suggested costs $100.

fmari --MariTool- · May 15, 2017

Don't do it. If drill gets dull and creates an internal crack you will have a failure in the near future with that pull stud. Not worth it.

Limy Sami · May 15, 2017

fmari --MariTool- said:
Don't do it. If drill gets dull and creates an internal crack you will have a failure in the near future with that pull stud. Not worth it.

I'd listen to the man that knows. and @ under $21 a pop? CAT4 Pull Studs - Retention Knobs - MariTool

Oh and if you haven't one, get yourself the socket for torqueing the studs in properly, .it's too easy to overdo things and cause BIG $$$$$ problems Pull Stud Sockets - Retention Knob Sockets - MariTool

gabedrummin · May 15, 2017

You could send out to guy with sinker edm or hole pop em for 10 bucks each .

Limy Sami · May 15, 2017

gabedrummin said:
You could send out to guy with sinker edm or hole pop em for 10 bucks each .

You could, BOTOH have you seen the aftermath of a VMC dropping a tool when it's under load? ...........not a pretty sight, .....nor a cheap one.

mtlhe · May 16, 2017

Well said and I agree with the advise, not worth the risk. Thanks gentleman.

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