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Drill flutes break off, cutting tip intact

Karl_Kunkle

Aluminum
Joined
Mar 3, 2011
Location
Wilmington, delaware
Running solid carbide twist drills
Various brands including shop ground

Length 2-3 diameter of depth various sizes.

Holes are blind x cross, picture drilling a t.

Materials drilled are a625, 304/l, 316, c276

Machine is a 10 year old mazak pallatech

Problem comes and goes throughout job but basically the first 1-2 inches of flutes chip off behind the cutting edges which stay intact.

It does not trip a load sensor but the finish go bad very quickly. So if a long running job and some crew doesn't check parts leads to a lot of rework .

Looking for advice on how to troubleshoot this issue.
 
Running solid carbide twist drills
Various brands including shop ground

Length 2-3 diameter of depth various sizes.

Holes are blind x cross, picture drilling a t.

Materials drilled are a625, 304/l, 316, c276

Machine is a 10 year old mazak pallatech

Problem comes and goes throughout job but basically the first 1-2 inches of flutes chip off behind the cutting edges which stay intact.

It does not trip a load sensor but the finish go bad very quickly. So if a long running job and some crew doesn't check parts leads to a lot of rework .

Looking for advice on how to troubleshoot this issue.

Breakage is on the SECOND hole, not the first? Chips are probably catching the edge of the cross gallery and trying to wedge.

Suggest an experiment:

Plug the first hole drilled before drilling the second. See if the problem goes away.

That may not be a solution you can use, long-term, but it should confirm the cause so you know where to look for one you CAN use.

High pressure coolant-through might be on the radar?
 
Running solid carbide twist drills
Various brands including shop ground

Length 2-3 diameter of depth various sizes.

Holes are blind x cross, picture drilling a t.

Materials drilled are a625, 304/l, 316, c276

Machine is a 10 year old mazak pallatech

Problem comes and goes throughout job but basically the first 1-2 inches of flutes chip off behind the cutting edges which stay intact.

It does not trip a load sensor but the finish go bad very quickly. So if a long running job and some crew doesn't check parts leads to a lot of rework .

Looking for advice on how to troubleshoot this issue.

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need to know feeds and speeds of course. also tool life. often on long runs, tool is deliberately put away so next tool change if tool expired it will not come out.
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often (normally) feed and speed recommendations are max recommendations. normally you reduce settings til tool life is acceptable. not unusual to reduce to 50% or less
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not unusual to go from 20 to 200 minutes tool life by reducing settings
 
....
Problem comes and goes throughout job but basically the first 1-2 inches of flutes chip off behind the cutting edges which stay intact.
..
Looking for advice on how to troubleshoot this issue.

Pictures?
What does behind the cutting edges mean?
After the tip with it's outside corners intact? Margin still good but secondary getting beat up?
Not sure if surface is bad from chips wrapping around and wedging or the outside tips are going to poop.
Drills have a back taper and if the chip is too thin it will get into this clearance and make a mess of things.
Would you consider your feeds aggressive or light? What do your chips measure in thickness with a caliper and what is the drill range size?
Bob
 
I'm in the ''cross hole'' camp, as I've had similar problems, ..........if it's not the chips taking the drill out it's the chips damaging the edges of the cross hole.

Normally I would have plugged the cross hole, but sometimes you can't.

I've got over it by reducing the feed, I reasoned thinner / finer chips would break up easier when getting caught in the cross hole, anyhow with extra pecking and coolant aimed up the cross hole to wash out the chips, it worked for me.
 
boy THAT'S a weird one.
what is your peck depth/ cycle look like?
what run-out limit (.005"/.001"/.0005"????) is your acceptable standard prior to loading new drills in the machine? Is it checked at all (i'm guilty of this one)
 
I think knowing wether the machine is running TSC or not is going to make a difference. Basically it has to be chips in one form or another, the only other problem would be breaking through, then starting again at an elliptical surface (but then the corners would be done for).

TSC yes or no?
Diameter of drill?
Hopefully not using peck drilling, if so cut that out first.

R
 
Feeds and speeds depends on material

Last job. Was c276 material. Tried speeds between 100 and 200 sfm, .004 to .008 ipr. Peck depth .50 to .125

Run out of shrink fit holder and tool less than .003 tir

Trying to add pictures but haven't figured it out
 
Feeds and speeds depends on material

Last job. Was c276 material. Tried speeds between 100 and 200 sfm, .004 to .008 ipr. Peck depth .50 to .125

Run out of shrink fit holder and tool less than .003 tir

Trying to add pictures but haven't figured it out

Honestly I was waiting for a response that was like "Oh it;s 1045" or something. If anything you are right in the zone or maybe the upper end for Hastalloy. Good job.

BUT don't peck drill!! At all. I mean 3x diameter is not deep at all even if you don't have coolant through.

Although knowing wether or not you have it would make a difference in response. When drilling super-alloys that little tid-bit of information is crucial to success and problem solving.

Your chip thickness is pretty thick for a super alloy---meaning those are already some hard ass chips before they are machined out. What you are dealing with is chip control in one way or another. That is what is fracturing the drills. The cross hole may come to benefit, or it may be what the chips are getting caught up in.

R
 
With coolant through the drill, chips are pushed up the flutes and lubricated UNTIL the tip breaks into the cross-hole. Then coolant drains away through the cross-hole, chips jam and break flutes.You could try less ipr for thinner, frailer chips, might help. Best would be to plug the cross-hole so coolant does not leak out, but still must exit by flowing up the flutes. Maybe your fixture can incorporate rubber plugs for the open end(s) of the cross-hole.
 
Okay I think I know what is going on. I would be willing to bet there is NO problem with the drilling of the first hole. I think what is happening, is when the drill gets through the cross section of the second hole, the chips are coming up the flutes and catching on the edge of the cross hole. Those are already some bad ass chips.

I would TRY drilling all the first holes. Changing drills for the second holes (cross holes) and using something like a Spade drill, because the cutting tip is much larger than the body of the holder, so the chips don't get caught. And if they do get caught it's Steel not Carbide, so less failure. Iscar has the Sumocham drills that are high performance drills with indexable heads and reduced shanks.

Or if you are not into that idea, I would drill all the first holes, move onto the second holes drill them all through to the cross section, insert M0 here (blow out all chips) then go back to the start and finish the depths.

R
 
It sounds as if a K-land on the flute would help your situation. A K-land is essential a dubbing or slight back bevel of the flute land. It is used for just this situation where the edge of a drill is getting beat up prematurely. We have made them a couple of times for customers having this problem. I don't have a picture currently, but could possibly mock up a PDF for you to look at if you like.

Mike
 
Drill the head of the T first, then the stem. I think the flute breakage is from chips being caught by the flute and jammed against the cross hole.
 
Beat us to it.

If it is the cross hole drill the top of the stated "T" first.

Then on the second hole you should know exactly where it will break through so normal drilling process until that point then change to tiny pecks to insure tiny chips that get blown through with coolant or change to smaller drill to pre drill hole then come back with correct one to make size.

Sent from my SAMSUNG-SGH-I337Z using Tapatalk
 
if drill is over $100. and if it breaks and you cannot get drill out and part is scrapped and remade taking considerable time and money you might find it is faster to use a HSS or cobalt drill going a slower sfpm and feed.
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basically if breaking drill is causing scrap and rework of 20 hours a year and if using a hss or cobalt drill going slow is taking 4 hours longer going slower the math can prove going slower is faster.
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just saying often with carbide even if you drilled 10,000 holes in 1 second if that cost you $100,000 in scrap and rework and if using hss drill takes 10 hours longer or $1000. what is actually faster or slower
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use math and look at the long term data
 
I think someone mentioned it earlier but with a Carbide Drill you should never Peck Drill especially with a Coolant Fed Drill as you should have no issues getting the chips out. It will only work harden the material in C276 and beat up the drill point.

If you can drill the T first that would solve all of your problems. If you can't then I'd look at a 3 Flute, Flat Bottom or Straight Flute Drill as they will stay truer in cross hole applications and keep the backside of the flutes from chipping out.
 
I think someone mentioned it earlier but with a Carbide Drill you should never Peck Drill especially with a Coolant Fed Drill as you should have no issues getting the chips out. It will only work harden the material in C276 and beat up the drill point.

If you can drill the T first that would solve all of your problems. If you can't then I'd look at a 3 Flute, Flat Bottom or Straight Flute Drill as they will stay truer in cross hole applications and keep the backside of the flutes from chipping out.
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i often use G98 or initial Z rather than G99 go to R
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you can drill 4" deep with one G81 and then use another G81 with R value -3.9" into part. drill will rapid down into hole and drill deeper as much as programmed
G98 G0 G43 H1 Z2.0
G81 X0. Y0. Z-4.0 R0.1 F6.
G81 X0. Y0. Z-8.0 R-3.9 F3.
between holes moves at initial Z of Z2.0 but when drilling rapids to R value
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its basically a long peck only done once to get chips out. and 2nd G81 can be a different feed rate what ever you want
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i often do when short pilot drill goes 4" deep and long drill goes in and continues drilling. obviously longer drill at high feed will bend too easily and need reduced feed
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if you got a cross hole then at cross hole you can choose your feed at that problem area
use as many G81 as you want you want 2 pecks each with different feed not a problem
 








 
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