300M material

[jeff]

How does this material compare to 4340 and/or 4340 pht? We cut both pretty much all the time here.

We have to drill some 1/4" holes, 15" deep on a lathe. 

[Colin Gilchrist]

60 to 1, depth to diameter. What could possibly go wrong?

Can you drill them from both sides?

What kind of tool holders do you have, and what kind of coolant delivery method?

Sounds....

...

....

.... uh

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... fun?

[jeff]

3 minutes ago, Colin Gilchrist said:

60 to 1, depth to diameter. What could possibly go wrong?

Can you drill them from both sides?

What kind of tool holders do you have, and what kind of coolant delivery method?

Sounds....

...

....

.... uh

....

....

... fun?

We only a couple of parts to do, blind hole. 

Probably just going to get an aircraft drill and do small pecks. Set it up and let it run, not going to try and break any cycle time records lol.

[RaiderX]

coolant thru spindle tool will be a must. but you knew that.

if time is not issue, cobalt might do it 30 sfm .001 chip lots of pecks

I would lean toward a carbide tipped gun drill and talk to saleman on feeds-speeds per their tool.

 

[Sticky]

If you are used to machining 4340 Pre Hard then 300M is no problem. I would most definitely do this with a gundrill, which will make it a slow but relatively stress free operation. Using an aircraft drill and pecking should remove any remaining hair on your head.

[huskermcdoogle]

2 hours ago, RaiderX said:

I would lean toward a carbide tipped gun drill and talk to saleman on feeds-speeds per their tool.

Send it out for gun drilling and be done with it.  If you don't mind buying a gun drill, it isn't hard to do.  

I haven't cut 300m in 13 or so years, but I recall it being easier to work harden than 4340.  4340 was a cake walk in comparison, from 4340 to 300m figure about a 40%-50% difference in yield strength, 75-80% in ultimate, which means it is more likely to make stringy chips.  Of course those numbers are in the heat treated state.  But anyway, it has more of the elements that make 4340 harder to machine than say 1045.  So bottom line it's going to take more force to cut.  Drilling shouldn't be bad, chatter wise.  But as you know this will all be about keeping the cutting edge cool and chips flowing out of the hole.

[Sticky]

A gundrill is only going to set you back a whopping $100. It's a skill worth having imo.