chatter when drilling

dian · May 7, 2020

sometimes i get "vertical vibration", almost like hammering action when drilling in steel with manual feed. usually it goes away by adjusting the feed. but the hole is unacceptable anyway. and im not talking about some difficulty of the drill to start the hole, which is normal.

why is this happening and how to avoid it? i almost get the feeling the drill is too sharp. but that doesnt make too much sense.

michiganbuck · May 7, 2020

Until the drill's OD circle land gets in the hole the chisel point can make a drill wander.
A split point sometimes avoids this.
A small depth pre hole of a little smaller diameter sometimes helps.

A pre drill about the size if major drell's web can help with it being drrp enough to get some OD land if the larger drill in the hole..Guess the pre drill would be about one drill diameter deep. ( >.866xD)

cyanidekid · May 7, 2020

dian said:
sometimes i get "vertical vibration", almost like hammering action when drilling in steel with manual feed. usually it goes away by adjusting the feed. but the hole is unacceptable anyway. and im not talking about some difficulty of the drill to start the hole, which is normal.

why is this happening and how to avoid it? i almost get the feeling the drill is too sharp. but that doesnt make too much sense.

More information needed! (you know this!) Diameter, speed, type of steel and thickness, drillbit, machine, lube, the finish you are seeing and why it’s “unacceptable anyway”?

Sounds like regular chatter, going slower on a more rigid setup is usually the answer. Annular cutters, decent milling machine with variable speed, magnetic base drills, step drills for thin stuff, hand held cordless on slow speed setting, good cutting lube, all the regular answers.

DMF_TomB · May 7, 2020

dian said:
sometimes i get "vertical vibration", almost like hammering action when drilling in steel with manual feed. usually it goes away by adjusting the feed. but the hole is unacceptable anyway. and im not talking about some difficulty of the drill to start the hole, which is normal.

why is this happening and how to avoid it? i almost get the feeling the drill is too sharp. but that doesnt make too much sense.

.
if length to dia ratio too high its normal for extra long skinny drill bit to not behave as well as short ones.
.
not sure what you mean by unacceptable hole, if drill bit sharpened unevenly alot I have seen drilled hole over .040" oversize cause drill bit vibrating and bouncing around alot. even if resharpened on a machine if operator doesnt have drill bit in resharpener chuck correctly drill bit can be badly sharpened off center....... obviously guy resharpening should look at sharpened drill bit and check if resharpened evenly

dian · May 7, 2020

i see it happen occasionally and have not figured out what is causing it. no special circumstances, last time i was putting three 7.6 mm holes trough mild steel 10 mm deep. brand new drill, reputable manufacturer, regular lenght, 2000 lbs mill/drill, albrecht chuck. first hole chattered dry, second chattered oiled, the third i fed very aggressively and i was through in a split of a second. all holes were too big for a 8 mm reamer (i usually would drill 7.8 mm, but that drill was misplaced). the quill handle was getting shocks like somebody beating with a hammer on it. thats no good and can beat the work piece down in the jaws, if the parallels have to be removed, make the drill spin or even breake it.

and again, im not talking about starting the hole. and usually i have no problems drilling, even on the little, sloppy tabletop drill press. now i have to investigate if it happens with new drills only, might be the case. it almost looks like drill is taking too large a bite.

edit: i like to drill slow, around 30 ft/min for hss.

DMF_TomB · May 7, 2020

dian said:
i see it happen occasionally and have not figured out what is causing it. no special circumstances, last time i was putting three 7.6 mm holes trough mild steel 10 mm deep. brand new drill, reputable manufacturer, regular lenght, 2000 lbs mill/drill, albrecht chuck. first hole chattered dry, second chattered oiled, the third i fed very aggressively and i was through in a split of a second. all holes were too big for a 8 mm reamer (i usually would drill 7.8 mm, but that drill was misplaced). the quill handle was getting shocks like somebody beating with a hammer on it. thats no good and can beat the work piece down in the jaws, if the parallels have to be removed, make the drill spin or even breake it.

and again, im not talking about starting the hole. and usually i have no problems drilling, even on the little, sloppy tabletop drill press. now i have to investigate if it happens with new drills only, might be the case. it almost looks like drill is taking too large a bite.

edit: i like to drill slow, around 30 ft/min for hss.

.
.
got to look at drill point, if angles (rake/clearance) are off, drill wont work that good. even new drills can be badly sharpened. i have occasionally seen drills look liked were sharpened backwards or negative clearance. surprisingly if you force drill sometimes they still drill holes just not that well

dian · May 8, 2020

the drill looks very good, i checked it under the camera (200x). its very sharp. actually its a nice drill, having a secondary relief and a split point. today i took the same drill to the flimsy, chinese drill press and it worked well. it produced a clean hole, a little trilobed on entry, but thats normal. i was able to ream exactly to specs. i have to investigate this further, but it almost seems like the drill press is flexible enough to absorb the shocks from drilling.

any thoughts? does anybody dull their new drills? seems like a stupid idea.

thermite · May 8, 2020

dian said:
the drill looks very good, i checked it under the camera (200x). its very sharp. actually its a nice drill, having a secondary relief and a split point. today i took the same drill to the flimsy, chinese drill press and it worked well. it produced a clean hole, a little trilobed on entry, but thats normal. i was able to ream exactly to specs. i have to investigate this further, but it almost seems like the drill press is flexible enough to absorb the shocks from drilling.

any thoughts? does anybody dull their new drills? seems like a stupid idea.

MY "thought" is a resonance with your mill/drill's powertrain. It could be ANYWHERE, and probably a "perfect storm" of several contributors- motor itself, forward, drill the "tuning fork" of an active delivirer of Bad News.

That you do NOT have the problem on the El Cheapo Chinese DRILLPRESS, same material, drill, and sizes?

There's your 'tell'.

If you "must" make these holes on the mill, not the DP? Say for better control of location? Buy a "plunge" endmill with an ODD flute-count. Problem likely goes away.

dian · May 8, 2020

i got the mill/drill (its a fehlman picomax 50) to to make nice, precise holes. usually it works. occasionally not, but i cant be sure it only happens on this machine. to make it clear, im not really looking at vibration, its rather pulses of maybe 10 hz when going 500 rpm, so it might just be one or both flutes grabbing too much.

thermite · May 8, 2020

dian said:
i got the mill/drill (its a fehlman picomax 50) to to make nice, precise holes. usually it works. occasionally not, but i cant be sure it only happens on this machine. to make it clear, im not really looking at vibration, its rather pulses of maybe 10 hz when going 500 rpm, so it might just be one or both flutes grabbing too much.

"Might just be.." my "Maiden" Aunt who never married was not exactly a Virgin, too [1].

You are guessing .. even "rationalizing" - when you should be researching.

Or even setting up to conduct some controlled experiments to find "the REAL 'why?'".

THEN take corrective action that fits the need and consistently delivers a solution.

[1] "MARRY? Pshaw! When I wanted a man, I HAD one! When I didn't, I DIDN'T! Who wants to RAISE one of the troublesome things!"

DMF_TomB · May 8, 2020

dian said:
the drill looks very good, i checked it under the camera (200x). its very sharp. actually its a nice drill, having a secondary relief and a split point. today i took the same drill to the flimsy, chinese drill press and it worked well. it produced a clean hole, a little trilobed on entry, but thats normal. i was able to ream exactly to specs. i have to investigate this further, but it almost seems like the drill press is flexible enough to absorb the shocks from drilling.

any thoughts? does anybody dull their new drills? seems like a stupid idea.

.
hand stoning flats on cutting edges is commonly done when drilling soft brass so it doesnt grab and pull drill bit into hole suddenly. normally not done with steel. some steel has slag hard spots and drill can resist going through it and bounce vibrate trying to go around it.
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I would look to shorten drill stickout length. also some drills are made for cast iron, wood, aluminum, etc and might work poorly in steel. split point drills I have seen the split point badly done wrong angles cause problems too.
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if only happen on the one machine, that machine might have a mechanical problem

thermite · May 8, 2020

DMF_TomB said:
if only happen on the one machine, that machine might have a mechanical problem

One machine, a good machine, one narrow range of circumstances, and he can measure a stable Hz component as if it were "the mighty Wurlitzer" pipe-organ holding a musical note?

"Might"?

Bet your sweet ass there's a resonance contributor - not "just" the drill and its grind.

Not new. Lots of successful prop-driven aircraft have "ranges" as are forbidden to dwell in. They still got the job done by simple avoidance of that incipient disaster.

Slow TF down, this problem goes away as well. "Damping" thing. Inherent.

Not enough cooperative energy "in tune" with the resonance delivered into the "tuned object"?

It does't even start.

See antique hand-cranked blacksmith's "post" drill.

Less "offensive" to the Swiss sense of righteous than having yer mill's ass kicked by a cheap Chicom "drillpress-shaped-object", ain't it?

DMF_TomB · May 8, 2020

I have seen machines with servo oscillation and hydraulic oscillation and worn ball screw problems. they usually dont go away unless repaired by maintenance. if problem on a particular machine especially if all of a sudden, its often a mechanical problem
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I have also seen a cnc at certain rpm and certain tools vibrate bad enough to trip safety door switch on back of machine causing the rpm to drop and go back up roughly every second from door vibration. rpm drop enough vibration would stop and then rpm would go back to normal causing vibration again. easiest thing was to avoid that particular rpm 10 or 20%
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seen plenty of problems caused by drill bad sharpening and drill going in pilot hole close to drill size causing random vibration cause long drills often make bad reamers. extra long drills often vibrate badly at normal feeds and speeds
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could also be slag hard spot. drills often vibrate if hard spot is big enough

mike44 · May 9, 2020

Have you tried another drill bit? Could be the drill is slightly bent.
mike

number 2 · May 9, 2020

90ft/ min for HSS in steel is normal. Try speeding up a little. Could be thrust bearings even are stuffed in the quill, but they would have to be well gone to cause a real problem drilling I would think. I was going ask if the head is clamped securely but can’t see from any photos if that’s an option.

jrmach · May 9, 2020

Dull the bit with a diamond file about .005 perpendicular to the grind

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