Chipping HSS drill in garbage 304SS; Want S+F advice going forward

dandrummerman21 · Dec 22, 2021

I have this job that keeps repeating and quantities get higher and higher. Each part has 8 2.5" (drilled depth) deep M20 tapped holes. The tapping I have down. But the drilling sucks

I have tried solid carbide (not TSC at the time) and after it chips, it quickly went to hell and I had to dig carbide out. With that in mind, I do NOT want to get TSC carbide drills for this job. The quantity is still low (I only have about 150 holes to drill this run) and I do not want to wreck 250$+ drills until I find a sweet spot. I want advice about going forward with HSS only. I also tried a spade drill with cobalt insert but wrecked the insert and body after only a few holes.

With that out of the way, I did snag some oil hole drills from ebay. 11/16" diameter. One is PTD HSS and the other is Nachi M42 Cobalt. I have thru spindle coolant.

So, here are pictures of the drill that I ran this job with last. It was HSS, maybe PTD/Dormer but not sure the brand.

Yes, I just pulled that drill out of the machine. It successfully finished drilling a part to depth looking like that. Honestly it probably sounded better than when resharpened. We resharpen big drills like this in house.

This was running a G83 cycle at 220rpm (40sfm), .9ipm (.004 per rev), and a .060" peck

I think the full out pecking is causing the chip to have to break, but its gummy ass stainless and it doesn't want to break, so it rips the edge off the drill.

So where should I go from here with the new drills? I have thru spindle coolant, so i was thinking I could have a short retract with G73. Or hard code pecks where it doesn't retract, but just pauses a couple revs so the chip breaks. I am almost certain I wont be able to get the chips to break by feeding it hard.

Can I go faster (both SFM and chipload) with the new drills because i have coolant at the tip? Should I G73 it or have it pause or slowly feed back a few thou to break the chip? What would you do?

I will also add, I want it to be reliable, and it doesn't need to break speed records. I don't care if it takes several minutes a hole. As long as it is reliable and predictable. I can change the drill every few parts as needed.

wmpy · Dec 22, 2021

Is it imperative that you break the chips? If you can live with stringers, I would get rid of the pecks. You're not going that deep. Maybe do one peck once you get near the bottom if chips are packing.

If you do peck, make sure you program a decent dwell before you do so it's done making a chip before the tool pulls back.

I'm assuming this is on a VMC?

If you can afford buying new tooling, a premium drill made for SS would be my first choice. OSG EX-SUS drills have been very reliable for me in SS. Though, I don't know if they make them that big.

Shawnrs · Dec 22, 2021

dandrummerman21 said:
I have this job that keeps repeating and quantities get higher and higher. Each part has 8 2.5" (drilled depth) deep M20 tapped holes. The tapping I have down. But the drilling sucks

I have tried solid carbide (not TSC at the time) and after it chips, it quickly went to hell and I had to dig carbide out. With that in mind, I do NOT want to get TSC carbide drills for this job. The quantity is still low (I only have about 150 holes to drill this run) and I do not want to wreck 250$+ drills until I find a sweet spot. I want advice about going forward with HSS only. I also tried a spade drill with cobalt insert but wrecked the insert and body after only a few holes.

With that out of the way, I did snag some oil hole drills from ebay. 11/16" diameter. One is PTD HSS and the other is Nachi M42 Cobalt. I have thru spindle coolant.

So, here are pictures of the drill that I ran this job with last. It was HSS, maybe PTD/Dormer but not sure the brand.

View attachment 337650 View attachment 337651 View attachment 337652 View attachment 337653 View attachment 337654

Yes, I just pulled that drill out of the machine. It successfully finished drilling a part to depth looking like that. Honestly it probably sounded better than when resharpened. We resharpen big drills like this in house.

This was running a G83 cycle at 220rpm (40sfm), .9ipm (.004 per rev), and a .060" peck

I think the full out pecking is causing the chip to have to break, but its gummy ass stainless and it doesn't want to break, so it rips the edge off the drill.

So where should I go from here with the new drills? I have thru spindle coolant, so i was thinking I could have a short retract with G73. Or hard code pecks where it doesn't retract, but just pauses a couple revs so the chip breaks. I am almost certain I wont be able to get the chips to break by feeding it hard.

Can I go faster (both SFM and chipload) with the new drills because i have coolant at the tip? Should I G73 it or have it pause or slowly feed back a few thou to break the chip? What would you do?

I will also add, I want it to be reliable, and it doesn't need to break speed records. I don't care if it takes several minutes a hole. As long as it is reliable and predictable. I can change the drill every few parts as needed.

have you tried inserted drills? In our stainless steel parts we have used Guhring 5514 drills which seem to work fine. I have also use MA-Ford drills in stainless but it seems more like an issue with the matrial being shitty. Most carbide drills we do not peck in stainless but if we have to the peck is usually 2 or 3 pecks max. I know Seco has some crownloc drills that at my old place we used on our lathes.

mhajicek · Dec 22, 2021

TSC makes a huge difference for carbide and powder metal drills. It gets the chips out so you don't have to peck.

Milland · Dec 22, 2021

I'd want to use a cobalt stub drill, coolant through, hard code with no pecks but dwells of at least one revolution say every 1/2", including at the bottom before retract.

Might start at 250 rpm, .003"/flute, adjust s/f and dwell time from what I see and hear. I'd want a good holder, anything I can do to improve stiffness would be helpful. I'd also want a geared head to ensure I had torque and wasn't stalling the mill.

kevin66 · Dec 22, 2021

We have had great luck with Iscar DCN replaceable tip carbide drills in 304 plate using TSC.

CNC_Chip_Thin · Dec 22, 2021

Dwelling and pecking in 304 = work hardening. My go to would be Split point cobalt drill, 35 SFM @ .006 ipm in one shot

https://www.mscdirect.com/product/details/74130519

Booze Daily · Dec 22, 2021

This is on a lathe, but I drill small first then go in with the to-size drill pecking about .300. Go small enough to clear the web, but leave enough so you don’t wipe out the margin on the big drill.

Trevlaw · Dec 22, 2021

Get an OSG EX-SUS GOLD drill in the size you need. They kick ass in stainless at they're recommended feeds and speeds. Also your chipload is way lower than I'd normally run. I go .001" per rev for every .0625" of drill diameter in most generic stainless and it's never let me down.

plastikdreams · Dec 22, 2021

+1 on not pecking, that split second between z+ and z- can be enough to work harden that crap...especially if there's chips in there.

D Nelson · Dec 22, 2021

Try a YG gold p drill they kick ass
And the price is good
Don

Sent from my iPhone using Tapatalk Pro

empower · Dec 22, 2021

dandrummerman21 said:
I have this job that keeps repeating and quantities get higher and higher. Each part has 8 2.5" (drilled depth) deep M20 tapped holes. The tapping I have down. But the drilling sucks

I have tried solid carbide (not TSC at the time) and after it chips, it quickly went to hell and I had to dig carbide out. With that in mind, I do NOT want to get TSC carbide drills for this job. The quantity is still low (I only have about 150 holes to drill this run) and I do not want to wreck 250$+ drills until I find a sweet spot. I want advice about going forward with HSS only. I also tried a spade drill with cobalt insert but wrecked the insert and body after only a few holes.

With that out of the way, I did snag some oil hole drills from ebay. 11/16" diameter. One is PTD HSS and the other is Nachi M42 Cobalt. I have thru spindle coolant.

So, here are pictures of the drill that I ran this job with last. It was HSS, maybe PTD/Dormer but not sure the brand.

View attachment 337650 View attachment 337651 View attachment 337652 View attachment 337653 View attachment 337654

Yes, I just pulled that drill out of the machine. It successfully finished drilling a part to depth looking like that. Honestly it probably sounded better than when resharpened. We resharpen big drills like this in house.

This was running a G83 cycle at 220rpm (40sfm), .9ipm (.004 per rev), and a .060" peck

I think the full out pecking is causing the chip to have to break, but its gummy ass stainless and it doesn't want to break, so it rips the edge off the drill.

So where should I go from here with the new drills? I have thru spindle coolant, so i was thinking I could have a short retract with G73. Or hard code pecks where it doesn't retract, but just pauses a couple revs so the chip breaks. I am almost certain I wont be able to get the chips to break by feeding it hard.

Can I go faster (both SFM and chipload) with the new drills because i have coolant at the tip? Should I G73 it or have it pause or slowly feed back a few thou to break the chip? What would you do?

I will also add, I want it to be reliable, and it doesn't need to break speed records. I don't care if it takes several minutes a hole. As long as it is reliable and predictable. I can change the drill every few parts as needed.

if you have TSC on the machine, its silly not to use a TSC drill. talk to your tool guy and have him recommend a reputable vendor for a drill, buy it on guaranteed test. they will give you the feeds and speeds to run it at, and if it doesnt work, you dont pay.
150 holes in 304 is not a small amount.
pecking is what's likely killing your drills.

i've had INCREDIBLE success with mitsubishi carbide drills in all kinds of materials, and my local rep always gives me tools on guaranteed test. as well as feeds and speeds that work off the bat.

dandrummerman21 · Dec 22, 2021

Okay, it's late and I have glanced at suggestions thus far but haven't looked into anyone's specific tools or pricing on anything. I'm just going to post some more information.

Machine is a Kitamura h400 horizontal. It has a transmission so I have low end torque.

Thru spindle coolant pump is 1000psi but I think we have it limited to 600 or 800.

The tools I bought are HSS and Cobalt, both with thru spindle coolant holes in them, in the 70$ range. I have the means to resharpen these tools, but I lack the means to sharpen carbide drills in house.

I will be holding these drills in a 11/16" TG collet for TSC, so most of the pressure will be going out the tip of the tool. I wasn't running TSC previously because it just pissed out the collet.

I do not have any insert drills that size, only allied spade drills, which didn't work at the time.

I had 0% chance before, running regular drills, with no pecking. I haven't put the TSC hss drills in the machine to test. If some of you think I might be able to break a chip without pecking, that'd be awesome. I can't tolerate too much of a rats nest around the tool because it would likely get big quickly and knock coolant nozzles around. I can program it to try to spin/throw off chips if necessary.

Keep suggestions coming, thank you. I'll read more into things in the morning.

Rapid_Tech · Dec 22, 2021

HSS drills in a Kitamura horizontal with 100's of psi of TSC :dopeslap:

. Get yourself a flat bottom indexable drill like an Iscar DR. A 17.5mm drill running at a reasonable speed of 2000rpm and a feed of .004/rev will make each hole in about 20 seconds and it'll look like it was reamed.

Mtndew · Dec 23, 2021

BT Fabrication · Dec 23, 2021

the coolant on the peck is killing that drill, aka super hot tip on the end from rubbing and not cutting hard enough, aka low feed, then it retracts into ice cold coolant that is fracturing the drill as it plunges back into the material.
anything that deep needs tsc. most people tend to feed too slow in stainless which creates more heat and problems.

Omega · Dec 23, 2021

Are you spotting the hole ?, Spot/ Cobalt drill if you want slow with reliability.. 50 sfm x 3.82 divide by drill dia = RPM ....so 275 RPM good old G83 peck .150 to .250 deep at 3 to 4 IPM and walk away..

As others have said, OSG (high perf. drills) you could kick the above up 20 to 30 percent.

dandrummerman21 · Dec 23, 2021

Okay, update.

I want to use what I already bought. BUT am open to the suggestions above if it doesn't work out. Again, I can resharpen HSS/CO without issue, and can do so many times before the tool gets too short. I can't resharpen solid carbide.

I did look into prices:

OSG EX SUS GOLD 17.5MM 232$ LIST. NO THRU COOLANT?

GUHRING 5514 17.5MM 382$ LIST. NO THRU COOLANT? I DID NOT LOOK UP THRU COOLANT VERSION

ISCAR DR0688-3445-075-05-5D-N 551$ LIST. PLUS INSERTS.

ISCAR DCN 0787-394-100A-5D 409$ LIST PLUS INSERTS.

HERTEL STUB COBALT: NOT LONG ENOUGH BUT I HAVE THESE AND INTEND TO SPOT WITH THEM

YG GOLD: NOT COOLANT THRU?

The winner in my mind out of the above suggestions would be the Iscar DR. At least, that is what I would try first if I need to buy more tools.

Onto results. I've only ran 1 part this morning, and it went well. Well, the main drill did.

I put in a screw length M42 cobalt drill, 135* point, at 400rpm and 2ipm (.005 ipr). I was only going .100 deep. On the very first hole, when it went to retract back to the rapid plane after spotting, I heard a "DINK" and took a look. The chip tore the cutting edge right off of the drill. I since changed to a G82 cycle and am feeding at 500rpm 1.5ipm now. That worked without chipping.

With the HSS coolant thru drill, I changed to 35sfm (about 200rpm) and increased to .006ipr (1.2ipm). I changed it to a G73 cycle, 1/2" deep peck, but I only have it retracting .003" in the hole, just to break the chip. Chips came out long, wrapped around a bit, but That was not a real issue (other than I will need to add a spindle reversal between holes to throw chps) I plan on trying to shorten the peck so i have shorter chips. Tool looked perfect, no chipping after 8 holes.

My only concern in going faster with a carbide tool is thrust. The Z axis thrust was running in the 100-120% range. I'm not sure if an inserted drill would be any less?

Thanks so far guys. I'll keep posted and I'll check back for more suggestions.

MaxPrairie · Dec 23, 2021

0.9 feed is too low. My first choice would be thru coolant flat bottom indexable drill, second option is what I had to do the other day for a rush job. 3" deep 11/16 hole, drill 1.5" deep with 5/16 drill then 1.4" deep with 11/16 drill with 0.12 pecks. Drill 5/16 down all the way with IJK pecks then finish 11/16 with IJK pecks. Is it slow? Yes. Did I wear out a drill? No. 5/16 drill was 135 deg cobalt, 11/16 was just a HSS like you are using. I think 40 sfm is good, but if it's shitty stainless go to 35. I typically start with a feed of 2.5 ipm, but anywhere between 2-4 is typically good.

Edit: Saw your most recent post. We run a 1" Indexable Walter drill in 17-4 H900 without any issues. I can find the drill # if you would like.

Trevlaw · Dec 23, 2021

Why are you still pecking if you've got coolant through on the HSS drill. 40sfm maybe up to 50 with coolant through, .011" per rev, drill it in one shot and be done with it.

Chipping HSS drill in garbage 304SS; Want S+F advice going forward

Stainless

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Titanium

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