peck drilling good or bad ?

so had a job the other day running program as programmed.
1) drill bit new used less than 20 minutes
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2) 10" deep horizontally drilled .375" dia hole, feeds and speeds in normal range with shorter drill depths has 99.999999% success rate per 100,000 holes
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3) programmed to enter 4" deep .375 dia pilot hole at low rpm once in hole rpm goes higher and a G1 at feed given to 10" depth, when done spindle shuts off and it pulls drill out.
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4) as often happens at high or low feed and 500 different in between feeds and speeds on a deep hole no coolant getting to drill tip and flutes hard packed with chips. no coolant ever getting through to the drill tip coolant. so drill breaks 9" into hole. happens about 5 to 20% of time based on data from last 100,000 holes drilled
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5) 10 hours labor into machining part, broke drill often takes longer than 10 hours to remove. the drilling without pecking maybe trying to save 5 to 10 minutes drilling. at end of year broken drills taking at extra 50 hours of labor per year (removing broke drills or remaking parts) that was trying to save maybe 5 hours per year by not peck drilling
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6) data from last over 10,000 parts and easily over 100,000 holes show peck drilling if done carefully like slowing rapids and having machine stop rapids and go into feed at least 0.1" away (parameter setting) to stop slamming into chip bur sticking up at hole bottom at rapids speeds. having peck not have drill tip come fulling out of hole but stay a 1" in hole to save drill tip whipping hurting drill tip on hole rentry with drill tip..... the failure rate peck drilling carefully is less than 0.01% the failure rate of trying to deep drill without pecking
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7) just a observation that not pecking when deep drilling has cause 10x to 100x more problems than peck drilling. so who is one who figured not pecking is better when data from last 100,000 holes says other wise ?? .....and yes over 500 different speeds and feeds tried. failure mode 99.999% of time is hard packed chips clogging flutes increasing turning resistance til drill breaks. many materials like cast iron do not flow chips through flutes any better at higher or lower feeds from data on last 500 different settings tried
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just observing its one thing to talk theoretical peck drilling is bad, its another thing dealing with broken stuck in hole drills and remaking parts which normally are causing 100x more problems based on last 100,000 holes drilled. maybe drill bit salesman says pecking is bad cause he wants broken drill bits so he can sell more drill bits

Who is telling you peck drilling is "bad"? I would say it is the goto method, with the exception of coolant thru carbide and insert drills. And like you said (without as much detail) at 20x(+) diameter you can't usually rely on the "regular" methods anyhow....

Mike1974 said:

Who is telling you peck drilling is "bad"? I would say it is the goto method, with the exception of coolant thru carbide and insert drills. And like you said (without as much detail) at 20x(+) diameter you can't usually rely on the "regular" methods anyhow....

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programmer says peck drilling is bad based on what drill bit salesman says and what drill bit catalogs say.
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but that does not agree with data from last 100,000 holes drilled. sure when pecking you got to use common sense. slow rapids, often not have drill tip peck fully come out of hole if tip is whipping at high rpm, make sure parameter of drill bit return peck stops rapids 0.1" away or more and go into feed to stop slamming into chip sticking up at hole bottom at rapids
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program with 15 different drill bits used and 3rd drill in program got the deep hole with no pecking, hear drilling noise but not bad got less than 1" to go (10"depth) but drill snaps. always a will drill break or will it finish the last 1" of depth judgement call. still frustrating having broken drill, 10 hours labor already into part and often takes over 10 hours to get drill out of hole. all cause somebody trying to save 5 minutes drilling time ? cause being told peck drilling is bad ?
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when actual results are recorded and not opinions, data says peck drilling carefully done saves 10x or more time than the results of not pecking by the end of the year and over 100,000 drilled hole actual results

A 99.999999% success rate is one broken drill per 100 million holes. You can't get that number from a sample of only 100,000 holes.

5%-20% failure rate is 1 in 20 or 1 in 5 holes. If you have data from 100,000 holes you should know which it really is.

If you've done 100,000 of those holes, you should have switched to a gun drill 99,999 holes ago...

DMF_TomB said:

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programmer says peck drilling is bad based on what drill bit salesman says and what drill bit catalogs say.
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salesman makes more money when you break drill bits

Sometimes you have to go with your gut, no way I would go that deep without pecking. I peck at 4xD, then 2xD, then 1xD after that. Drill bits are cheap, not too concerned if they wear out sooner. I prefer a reliable process.

I peck drill all the time. Even with coolant thru drills. Sometimes even with coolant thru drills you can get some long chips in alloy steels. So to keep everything running nice and reliable I still throw in some pecks. Generally when using coolant thru the first 3 or 4x diameter I go one shot. Then I peck every 1 or 2x diameter. Depending on application and what machine ( some machines have high thru the tool coolant pressure). By doing this I can't remember the last time a drill failed on us. Darn, I shouldn't of said that, murphy is listening....

You don’t peck with single-flute deep drills, you always peck with two-flute drill bits into the full, you don’t peck with three-flute enlarging drills. You don’t peck with carbide inserts drills, either.

i peck often even with spade drills (easily over 1000 spade drilled holes) and other drills that some say never to peck with
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obviously and maybe needs to be emphasized a billion times you usually when pecking
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1) slow rapids
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2) make sure parameter that controls where peck rapid back into hole stops from last peck distance and when it goes into feed. 0.100" gap or larger is common to not damage drill from burr sticking up from hole bottom with rapid moving drill.
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the other reason is when pecking usually some chips still in the hole if you rapid fast back in hole too close to where last peck stopped chips get pushed to end of hole compressed and its like drill hit something solid. literally i have moved a B axis rotary table cause drill compressing chips still in hole fast to hole bottom its like hitting part with a ton of force, big spade drill can hit part fairly hard pecking at fast rapids. slow rapids and it doesnt happen or hit the part so hard when drill pecks back rapids slowly into hole
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3) longer lengths you keep drill tip in the hole by getting over 90% of drill out of hole it gives coolant time to wash chips off flutes and a drill with only a 1" or 2" of flutes full of chips will have more room for more chips to get pushed along drill. no way tightly packed chips in flutes going to move over 8 to 20" along a drill. many a broke drill literally so tightly packed full of chips cannot turn drill easily but once chips out of hole it turns easy
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in over 40 years i have never not once broke a drill by pecking and have drilled maybe a million holes by now, i have broken over 100 drill bits by not pecking. obviously if you peck the correct way it will work 100x better than someone who doesnt know how to peck drill.
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what i dislike is program with no M0 warning the drill just comes out and breaks, even if operator notices a noise it often is not noisy enough where you think you got a problem but will still just snap or break drill bit off suddenly. and many a long drill used same feed as a short drill and you can see drill bit bending and eventually breaking cause same feed used for a 3" long drill is being used for a 20" long drill. even if drill doesnt break the hole can be curved and the far end of hole out of position easily over 0.1". kind of annoying when running as programmed you break drill bits or hole position out of tolerance even 10% of the time. its like taking a car trip and crashing the car 1 out of 10 trips. them odds are not acceptable. you generally want near 100% success or not break a drill bit in many decades reliability
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literally when recording times to machine a part including dealing with problems like broken drill bits, not peck drilling is one of the greatest time wasters recorded over the decades. literally by end of year it can be (for just one part type)
20 hours rework caused by trying to save
2 hours time not peck drilling at the end of the year

I use a lot of Harvey < 1/8" solid carbide drills in 17-4 and Ti, and Harvey recommends pecking with them.

mhajicek said:

I use a lot of Harvey < 1/8" solid carbide drills in 17-4 and Ti, and Harvey recommends pecking with them.

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obviously you use what works best.
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pecking is not fool proof. it does have certain factors that need to be aware off. for example pecking and rapids are so fast the coolant does not have enough time to wash the chips off the drill flutes. that obviously creates a problem going back into hole and loose chips at hole bottom get hit or compressed hard from fast rapids

DMF_TomB said:

99.999999% success rate

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Now that's funny.

Peck drilling can be a disaster for larger insertable drills. Shock loading the inserts can break them. Peck drilling is an age old way of getting coolant in and chips out but not applications should use it.

Are you using a gun drill with 1000psi TSC? If not, then you're going to break shit not pecking that deep.

Mtndew said:

Now that's funny.

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He's drilled over 100000 3/8 holes.

He didn't mention speeds and feeds, but lets say he's using a 10" long drill at 5 inches a minute. For simplicity, we are negating any time lost during pecks and tool change to drill the pilot hole.

100000 holes * (10" / 5ipm) = 200000 minutes of drilling = 3333 hours of drilling

What does he pull, 50 hour work weeks or so? that's 66 weeks of work, he's only drilled 10" deep holes. Not even done any other milling on that machine. Just drilling.

Lets let that sink in...

DMF_TomB said:

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obviously you use what works best.
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pecking is not fool proof. it does have certain factors that need to be aware off<-- extra "f"??. for example pecking and rapids are so fast the coolant does not have enough time to wash the chips off the drill flutes. that obviously creates a problem going back into hole and loose chips at hole bottom get hit or compressed hard from fast rapids

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My 2 cents.. And my disclaimer.. I tend to be conservative when drilling.

Peck drilling.. Its fricken great. pull all the chips up, get some more coolant
going down in that hole.. Fantastic..

The bad part, and Tom has already said some of this. Rapids.. Retracting.. You are cutting
this beautiful chip.. the tool is in compression.. You try and rapid out of that hole,
especially if running a high chip load and even WORSE in a work hardening material, and you put that
whole cutting edge in tension, along a fairly thin section.. You literally can easily RIP the cutting
edges off of your drill, and I've done it quite the number of times, especially with carbide (HSS
is more forgiving).. the worst culprit has been 13-8, at least for me.

Turning the rapids down is one way I've tackled this problem (for a few holes).. but I usually just
hand code the whole cycle when I know its going to be an ugly hole. Feed out about .010" and then
rapid out, or fast feed, sometimes going far above the clearance plane to allow any chips to get off
the drill, and a lot more coolant down in the hole. And then come back in a bit above where you stopped
cutting. Rinse and repeat..

What I just mentioned above is why I believe that many people say to never peck with carbide drills, you literally rip the cutting edges off by rapidly retracting. You are trying to shear the thickness of the chip, while the cutting edge is in tension, and carbide doesn't play that game, at all.. Some say to dwell before retracting, but doesn't that just feed into the whole work hardening thing?? I just feed back out about .010" or .020" and slice that chip off clean. No rubbing, no pushing... Its worked for me so-far.. sometimes the differnce between 2 holes and a 100 holes, and being able to put the drill back in the drawer, ready to fight another day.

Bobw said:

My 2 cents.. And my disclaimer.. I tend to be conservative when drilling.

Peck drilling.. Its fricken great. pull all the chips up, get some more coolant
going down in that hole.. Fantastic..

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I am the same way. Never had any issues. I drill 5/16 diameter holes 5" deep in H-13 steel with a standard cobalt parabolic drill. No coolant thru. Runs like a champ. Maybe takes 30-40 sec longer than if I used a carbide coolant thru. But the problem is I don't exactly have enough pressure for a 5/16 coolant thru drill at that depth. So I need to peck even the coolant thru drill. So the cobalt actually is the way to go. More reliable, hell of a lot cheaper. You have to look at the big picture sometimes.
Using a $20.00 drill and replacing it when 60% of its life is used up is better than using a $400.00 coolant thru drill and running it to 90% of its life ( because you want to get every penny from this drill) and it ends up buring up inside the part and crashing a few more tools.

broke a .166 drill today, only going about 1.1" deep, still no peck and it broke about 1" deep into the 1st hole. took about 3 hours to drill it out and replace drill and rerun and replace tap that broke (no tap hole) and rerun tap on the 4 out of 6 holes that were tapped
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so out of 6 holes with that .166 drill bit and round it off lets say its
3 minutes drilling with no peck and 6 minutes drilling if done by peck drilling
facts are trying to save 3 minutes (not pecking) cost 3 hours in labor.
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i might drill 30 holes a day and about 10,000 holes each year, so in 40 years that comes out to 400,000 holes but i never said i drill that many holes the whole 40 years. i probably drilled only 100,000 to 200,000 holes as a machinist so far.
i have broke one more drill today not pecking so thats at least 101 broken drills not pecking (not just 100) in 40 years

Bobw said:

What I just mentioned above is why I believe that many people say to never peck with carbide drills, you literally rip the cutting edges off by rapidly retracting. You are trying to shear the thickness of the chip, while the cutting edge is in tension, and carbide doesn't play that game, at all.. Some say to dwell before retracting, but doesn't that just feed into the whole work hardening thing?? I just feed back out about .010" or .020" and slice that chip off clean. No rubbing, no pushing... Its worked for me so-far.. sometimes the differnce between 2 holes and a 100 holes, and being able to put the drill back in the drawer, ready to fight another day.

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I'm 100% with you on this. Anything that needs pecking gets long handed to retract 1x the per rev feed before rapiding out, and rapids down to that safe location before resuming drilling feed. It's such an obvious problem with such an easy solution that as far as I'm concerned it's seriously negligent for it to have not been implemented in the typical peck drill canned cycles from the get go. I assume (and sincerely hope) that the control manufacturers who actually give a damn have got this figured out by now, but all I have to play with is a Fanuc.

I wonder how many people who drill all these holes bother to cut and cross section a few looking at the actual walls.
Perhaps doing so will quickly tell you that rapid retract is not a great idea.
Not such a problem for the cutting lips but the outside corners are not going to be happy.
Where do your drills die? Chisel, cutting lips, outside corners?
Bob

CarbideBob said:

I wonder how many people who drill all these holes bother to cut and cross section a few looking at the actual walls.
Perhaps doing so will quickly tell you that rapid retract is not a great idea.
Not such a problem for the cutting lips but the outside corners are not going to be happy.
Where do your drills die? Chisel, cutting lips, outside corners?
Bob

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Hey Bob.. Any chance you can have a cocktail or 2 and get a little chatty and expand on this a bit.
I'm interested to learn more.