Do you peck drill with through coolant?

lowCountryCamo · Jul 18, 2017

I am drilling deep holes in 17-4 stainless 36 rockwell. One hole is .150" 1.6" deep. Another is .08" 2" deep. I'm using OSG carbide tc drills on the .150" and Mitsubishi tc on the .08". Running on a haas vf3. Parameters are 250sfm and .0007"ipr on the .08" and .0015"ipr on the .150" I am also drilling .375 with and OSG tc drill but not that deep.

Am I better to peck or just rely on the tc to blast out the chips? I have a feeling that pecking is hard on carbide drills, in this material, and especially on the long X drills.

Thanks,
Steve A

Milland · Jul 18, 2017

Yes, pecking is bad for carbide due to micro-fracture of the cutting edge while it tries to "pull up" through the existing chip, which pulls off bits of carbide from the chisel edge. Then you risk hitting chips left at the bottom when coming back down.

Is your TSC 300psi or higher? You need pressure when using small drills due to the low volume of coolant getting through the tiny holes in the drill. I'd bet you're safe with the .150" drill, but I'd contact Mits with your machine data (pressure, desired feed/speed. etc.) to get their advise for the .080" drill.

Shop Supply Guru · Jul 18, 2017

lowCountryCamo said:
I am drilling deep holes in 17-4 stainless 36 rockwell. One hole is .150" 1.6" deep. Another is .08" 2" deep. I'm using OSG carbide tc drills on the .150" and Mitsubishi tc on the .08". Running on a haas vf3. Parameters are 250sfm and .0007"ipr on the .08" and .0015"ipr on the .150" I am also drilling .375 with and OSG tc drill but not that deep.

Am I better to peck or just rely on the tc to blast out the chips? I have a feeling that pecking is hard on carbide drills, in this material, and especially on the long X drills.

Thanks,
Steve A

1st you need to use a 3xD drill in those sizes and go max depth. Then go to depth with your through coolant drill no peck.

yardbird · Jul 18, 2017

Yeah I agree if its high pressure coolant you might get away with it? 2" deep is a long way in there for that tiny drill.

Brent

Bobw · Jul 18, 2017

lowCountryCamo said:
I am drilling deep holes in 17-4 stainless 36 rockwell. One hole is .150" 1.6" deep. Another is .08" 2" deep. I'm using OSG carbide tc drills on the .150" and Mitsubishi tc on the .08". Running on a haas vf3. Parameters are 250sfm and .0007"ipr on the .08" and .0015"ipr on the .150" I am also drilling .375 with and OSG tc drill but not that deep.

Am I better to peck or just rely on the tc to blast out the chips? I have a feeling that pecking is hard on carbide drills, in this material, and especially on the long X drills.

Thanks,
Steve A

My personal theory.. They say don't peck with carbide.. Why?

I've found that you can peck all day long with carbide in nasty work hardening materials....
BUT!!!! You have to feed back out a bit, and cut the chips off clean before you rapid out,
then leave a little clearance from where you stopped to begin feeding again..

Straight up peck cycle, I find you rip the cutting edges right off of a carbide drill.. And
cobalts too, though they last a little longer (nasty work hardening stuff).

36C, but what condition.. Solution treated or heat treated? 2 TOTALLY different animals...
When you get it, its ready to be "precipitation hardened" and its sort of hard, but its gummy
and sticky, kind of like 304... Heat treat it and depending on your final condition, it can
actually increase machinability by up to 50% AND the BEST PART.. It essentially loses all
of its shitty "stainless" properties (as far as cutting goes).. Treat it just like a hardened alloy steel.

deadlykitten · Jul 18, 2017

lowCountryCamo said:
Am I better to peck or

... time for trials

deadlykitten · Jul 19, 2017

Bobw said:
My personal theory.. They say don't peck with carbide.. Why?

I've found that you can peck all day long with carbide in nasty work hardening materials....
BUT!!!! You have to feed back out a bit, and cut the chips off clean before you rapid out,
then leave a little clearance from where you stopped to begin feeding again..

hello Bobw

i never dwell when drilling, but retreat in feed movement for a few tenths

such samples show exactly what you are describing ; kindly !

Code:

G01 Z+target_position     feed G95
    Z+target_position-0.3
G00 Z+clearance
    Z+target_position-0.5

........................or

Code:

G01 Z+target_position     feed   G95
    Z+target_position-0.3
    Z+clearance           feed*k
    Z+target_position-0.5

Bobw said:
I find you rip the cutting edges right off

right off every tool that is changing direction with an increased feed

sometimes fatique is not visible, but is good to know that it is there ...

skywalker4 · Jul 19, 2017

i cannot imagine not pecking on either drill, maybe like .030"- .050", i never experienced any breakdown of the cutting edge, and coolant thru shouldn't be leaving chips in the hole?

DMF_TomB · Jul 19, 2017

lowCountryCamo said:
I am drilling deep holes in 17-4 stainless 36 rockwell. One hole is .150" 1.6" deep. Another is .08" 2" deep. I'm using OSG carbide tc drills on the .150" and Mitsubishi tc on the .08". Running on a haas vf3. Parameters are 250sfm and .0007"ipr on the .08" and .0015"ipr on the .150" I am also drilling .375 with and OSG tc drill but not that deep.

Am I better to peck or just rely on the tc to blast out the chips? I have a feeling that pecking is hard on carbide drills, in this material, and especially on the long X drills.

Thanks,
Steve A

.
.
usually only peck if having more problems by not pecking

Mtndew · Jul 19, 2017

lowCountryCamo said:
I am drilling deep holes in 17-4 stainless 36 rockwell. One hole is .150" 1.6" deep. Another is .08" 2" deep. I'm using OSG carbide tc drills on the .150" and Mitsubishi tc on the .08". Running on a haas vf3. Parameters are 250sfm and .0007"ipr on the .08" and .0015"ipr on the .150" I am also drilling .375 with and OSG tc drill but not that deep.

Am I better to peck or just rely on the tc to blast out the chips? I have a feeling that pecking is hard on carbide drills, in this material, and especially on the long X drills.

Thanks,
Steve A

If you have the flute length AND enough TSC pressure to remove chips, there is no need to peck.
I've drilled 1/4" holes 7" deep no peck without issues.

But to answer your question, yes I sometimes peck, but only in rare situations. Like when my drill isn't coolant thru or when I just can't seem to break a damn chip.

AARONT · Jul 19, 2017

As previously mentioned pilot to 3xD with a stub drill then come in with the long drills. If you're running 300psi or more for tsc go in one shot. If not, you will have to peck using the method BobW mentioned.

toolsteel · Jul 19, 2017

When I use through coolant drills I never peck. I am mostly working in toolsteel...4140P, A8 etc....probably in the 20-22RC range. I use Through coolant drills down to .109 diameter and don't peck. I will feed them to the max depth per catalog...NOT the end of the flutes. We also do some drilling in fully hardened toolsteel (58-62Rc) It is a pretty brutal operation, we do use coolant but never a through coolant drill. In hard material the coolant holes make the drill to weak to take the down pressure involved and the drill just shatters. We end up having to peck with a solid carbide drill in order to get coolant at the tip.....like I said ...its pretty brutal and we avoid it...but when necessary it can be made to work. I don't think 30ish Rc requires anything special beyond the right speeds and feeds per the catalog. I have found with the drills I use that the catalog numbers are pretty accurate provided a good setup and holder.

sinha · Jul 19, 2017

Bobw said:
You have to feed back out a bit, and cut the chips off clean before you rapid out,
then leave a little clearance from where you stopped to begin feeding again..

This exactly is the behavior of standard peck-drilling cycles with full retraction.

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Do you peck drill with through coolant?

lowCountryCamo

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