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Drill leading off

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68machinist70

Plastic
Joined
Mar 18, 2021
Here's my dilemma.
Drilling a .187 hole 3" deep in 316ss.
Using a Walter carbide through coolant drill.
Running in a HAAS Ds30y with high pressure coolant.
I'm not breaking drills or getting chip weld but my hole keeps leading off center by .006 to .012.
I'm spot Drilling with a 90° 1/4" carbide going. 025 deep.
Using a g83 peck cycle withdrawing .5 out of the hole rapid back to .05 from end of last cut.
Tried running recommend feeds and speeds of 116sf , .0045f
I've played with peck depth from .05 to .250, feeds from .0025 to .006 and rpm from 1800 to 2500.
I get the best results around 2300rpm peck of .200 f.003. It holds a few part about. 002 or so off center or better but will then float out then come back.
I've indicated the drill and spot to .0003 c/l. Ive checked horizontal run out so as to make sure its sitting true to c/l length of the drill.
I've been machining plastic for the past 15 years. Shop is now venturing into steel and this is my first job.
Any help is appreciated.
 
You should spot the hole with a tool that has a greater drill point angle than the drill itself. This allows the center of the drill to make contact first rather than the od of the flute's.

Also +1 on the stubby drill for a pilot
 
Mainly from years ago at previous shops just how deep holes were always done. I've been reading other threads about drilling ss. I may give a steady straight pass a shot.
 
You may consider feeding at 50% upon entry and then going to 100% once the tip is in.....this is useful not only in machining.
 
The stock can work against you. Stainless alloys often bear tensions inside, with round bars you speak of core tension. Just telling
 
Ok, first question: How much pressure is "high pressure" on a Haas?

For me, high pressure is 1000PSI, and I wouldn't peck that drill at all (I would consider using a stubby drill for the first inch or so, but we regularly do holes that are .040" or less by 3 to 6 inches long with just one gun drill).

If high pressure for you is only 250 or 500PSI, then maybe a peck half way through, just to make sure you're evacuating chips well.

I'm assuming your drill point is 118°, your 90° spot is not doing you any favors, either switch it to a 120° or ditch it completely and just slow your feed for the first .100" or so.
 
What is the tip angle on your drill?
Is this maybe a Titex 6685?

I think that I prepped the start hole for those with a C'drill, followed by a SML Cobalt drill of the same D as the through hole (same tip angle as the Titex tool) and then the long drill.

My holes were straight, but I was in a lathe and had the benefit of spindle rotation to guide it too, so ....

I have 1000+ # pump.


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Think Snow Eh!
Ox
 
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