# Drill Bits Bending



## Garyg (Mar 31, 2015)

It doesn't seem what type of drill bit I use they seem to bend in the drill press or the lathe. Even large diameter 5/16 and greater bend.
They all seem to be made in China though. 
I even use a center bit to start the hole.


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## Micke S (Mar 31, 2015)

Check that the drill bit is perpendicular to the workpiece and that the drill bit is symmetrical at the end.


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## kd4gij (Mar 31, 2015)

Witch drill bits have you tryed?


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## JimDawson (Mar 31, 2015)

Maybe a little less pressure, more RPM?  But could be an alignment problem, or just really crappy drill bits.


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## Bill C. (Mar 31, 2015)

Try another brand. In the mean time take a small file and try filing a notch about half way up.  If it cuts a notch then the bits were not harden properly.  

I hate it when either drill bits or allen wrenches bend.  I had allen wrenches end up looking like drill bits.


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## G MORSCH (Mar 31, 2015)

I agree with Bill above.  I bought a cheap set of drills a few tears back and the are totally soft.  Stroke them with a file and see if they are hard.  They may only be good for wood and even then you will get extra practice sharpening them.
HSS must lose something in the translation between English and their dialect.

Good luck!

Gary


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## RJSakowski (Mar 31, 2015)

My wife bought some office furniture some years ago and I was pressed into service assembling it.  The screws were button head with 5mm hex sockets.  Each chair had a 5mm Allen wrench in the fastener packet and I was barley able to keep ahead of the wrenches as I assembled the ten chairs.  "Lousy tools" I thought.  When the assembly was done, A had a collection of 5mm wrenches.   I decided to to a little experiment.  I heated the wrench to a cherry red, until tit was no longer magnetic , then quenched in water.  I polished the wrench to a bright finish and heated it slowly from the middle until I had a dark straw color at the business end.  Guess what? It is now hard to a file and no longer twists in use.

Nothing wrong with the steel; they just do not know how to harden and temper.

Back to the original issue: bending drill bits.  I have observed this when hand drilling because the drill spindle is not aligned with the hole being drilled.  It usually precedes a snapped drill bit.  Is it possible that the spindle is not aligned with the quill so the drill is being fed off axis?   On a lathe, this would be indicative of a misaligned tailstock.


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## rsegars (Mar 31, 2015)

I have had good results even with the made in China bits, but I always start with a center bit and have the lathe at a very slow speed and drill with smaller bits first and gradually work up to the size I want. Not to mention lots of cutting oil. I was drilling a barrel bushing today and decided to see if some of the mess could be avoided. I placed a paper towel under the part that was being drilled and changed to a fresh one with each larger drill bit. The cleanup was very easy. Hope this helps someone.


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## Andre (Mar 31, 2015)

Real HSS bits would shatter before they bend (and hold a bend)!


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## RJSakowski (Mar 31, 2015)

Andre said:


> Real HSS bits would shatter before they bend (and hold a bend)!


Yes!  I was under the impression that Gary was observing flexing, not a permanent deformation.


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## Andre (Mar 31, 2015)

RJSakowski said:


> Yes!  I was under the impression that Gary was observing flexing, not a permanent deformation.


Now........ carbons steels will bend to some extent. I wonder if his were carbon steel.

I've REALLY reefed on a 5/16 drill, never had anything over say 1/8" bend while drilling.


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## Charcole (Mar 31, 2015)

Andre said:


> Real HSS bits would shatter before they bend (and hold a bend)!



Not necessarily.  HHS and carbide drills do have some flexibility. On the longitudinal axis of the body and from compression.  It's also why you see drills that are 10+ times diameters have more body clearance.


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## chips&more (Mar 31, 2015)

Charcole said:


> Not necessarily.  HHS and carbide drills do have some flexibility. On the longitudinal axis of the body and from compression.  It's also why you see drills that are 10+ times diameters have more body clearance.


I’m not too sure about carbide drill bits flexing and compressing and still being in one piece after the fact? HSS drill bits can and will flex when not used correctly.


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## Dave Smith (Mar 31, 2015)

make sure that your drill bits are sharp so they will drill without putting too much pressure on them---dull bits with excess force may want to flex----Dave


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## lowlife (Apr 3, 2015)

I have a high quality Chinese bit around here somewhere. I kept it because it bent 90 degrees and didnt break.......I was very impressed.


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## RJSakowski (Apr 3, 2015)

lowlife said:


> I have a high quality Chinese bit around here somewhere. I kept it because it bent 90 degrees and didnt break.......I was very impressed.


Must be a different manufacturer than the ones I have seen.  Most chip or break at the mere sight of the work.


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## X-RAY (Apr 3, 2015)

I had one actually untwist before. I'll have to see if I can find it and get a picture, it was pretty crazy looking.


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## savarin (Apr 3, 2015)

I just purchased a packet of 10 bits 3.3 mm from ebay,  only $3:00
Waste of time as every one is made slightly off centre, the point inscribes a circle approx 1mm.
They are not bent just made off centre.
Interesting as I've never seen that before.


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## markknx (Apr 3, 2015)

If all else mentioned is not the issue be sure your Chuck does not have a lot of run out
Mark


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## Garyg (Apr 4, 2015)

The drill bits bend/flex but spring back after pressure is taken off. My drill press does have a fair bit of run out but I try to use it  where acccuracy is not a problem. The tail stock on the lathe is quite good but for some reason I never thought about the chuck.  Everything seemed so tight. I will have to do some tests. The set of cobalt bits I bought do seem to be the ones I have the issue with now that I think about it. I hope not as it was a large set with all the numbered bits and the fractional ones.


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## mcostello (Apr 5, 2015)

Maybe Your stronger than You think!


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## darkzero (Apr 5, 2015)

Although a bit off topic but related to drill bit runout. I purchased a 29pc M42 cobalt drill set some time ago. It came in a nice Huot case but the larger bits have the 3 flats on the shanks. Well the flats are poorly ground & when using them there is a lot of runout. I clock the drills so the jaws grip on the full shank & there is minimal runout but it's annoying. Other than that they're fine but I'll never buy drills with 3 flat shanks ever again, US made or not. I don't trust them.


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## atunguyd (Apr 5, 2015)

I'll see your 3 flat shanks and raise you this.  A local manufacturer here makes some nice looking HSS bits with a single flat in the shank. Not a small flat like you see on some end mills but a flat running pretty much the length of the shank. I can't see how a drill chuck is going to grab that with no runout.


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## RJSakowski (Apr 5, 2015)

Drill bits with three flats from a reputable manufacturer are no problem.  For larger sizes, the three flats prevent the slippage which tends to chew up the shanks.  On the other hand, some of the junk bits out there will have the runout without the flats.  
I once bought a  full set of numbers, letters, and fractional for work.  We used them only occasionally but when we needed a particular size, we would have it.  The first use was drilling a a piece of steel channel.  The bit was thrashed after two holes.  At a later time, when using some of the smaller number bits, we found that several bits were the same size.  The bits also tended to break easily when pushed.


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## savarin (Apr 5, 2015)

Still on drill bits - What gets my goat is all the manufacturers that place the drill size right where the chuck grips the bit and only uses a light etch so it wears off almost in the first use.
I have a very old set of imperial bits where the sizes are engraved on a reduced band just above the twist. never wear off


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## markknx (Apr 5, 2015)

Bits are dull/sharpened wrong. or steel is harden have you tried the bits on different steel? Some thing like a piece of angle. Could also be you are feeding to hard for the speed of the drill. Like the spindle speed is to slow or you are forcing the bit to hard. Looking back at it being a 5/16 I would bet for sure you are feeding to hard. What is your spindle speed set at for the 5/16 bit?


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## markknx (Apr 5, 2015)

savarin said:


> Still on drill bits - What gets my goat is all the manufacturers that place the drill size right where the chuck grips the bit and only uses a light etch so it wears off almost in the first use.
> I have a very old set of imperial bits where the sizes are engraved on a reduced band just above the twist. never wear off



Yeah what Savarin Said! and could they make the number a little bigger. the type on everything is so small these days.


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## n3480h (Apr 6, 2015)

Last year I bought a drill set from a major US vendor, with lettered/fraction/numbered drills.  Many have snapped, many were never properly sharpened (no relief), and many were bent right out of the box.   I could get angry about it, but I see it as educational:  1. Never buy an "affordable" large set of drills, 2. Learn how to properly sharpen drills, 3. Roll every drill bit before use to determine if it is bent,  4. Measure every small bit to make certain it's the size the box says it is.  I've found several that are the same size.

Agree with the size stamp issue.  I now use a lighted magnifying lamp on all very small things.  Dang small numbers - what were they thinking? 

Tom


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## george wilson (Apr 9, 2015)

If your drill bits are bending in those larger sizes,like 5/16",you need to buy some better drill bits.

Will carbide bend? Probably a microscopic amount only. HSS can bend SOME,but should only be seen in the smallest size bits. I expect to see some flexing in a 1/16" bit,maybe a 1/8" bit.

I would NEVER,EVER buy Chinese drill bits. You are going to get what you pay for. And,some of those sets of bits only have the common fractional sizes hardened at all. They think the average American user,repairing some household item,will only ever use the common fractional sizes,like 1/4",etc.. So,they only harden those. Machinists need EVERY size hardened.


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## RJSakowski (Apr 9, 2015)

george wilson said:


> If your drill bits are bending in those larger sizes,like 5/16",you need to buy some better drill bits.
> 
> Will carbide bend? Probably a microscopic amount only. HSS can bend SOME,but should only be seen in the smallest size bits. I expect to see some flexing in a 1/16" bit,maybe a 1/8" bit.
> 
> I would NEVER,EVER buy Chinese drill bits. You are going to get what you pay for. And,some of those sets of bits only have the common fractional sizes hardened at all. They think the average American user,repairing some household item,will only ever use the common fractional sizes,like 1/4",etc.. So,they only harden those. Machinists need EVERY size hardened.


Carbide bits do bend quite a lot actually.  I work with a lot of small sizes (.014 -.060").  If drilling a hole with the lathe that was not accurately centered, you can watch the drill tip precess around the lathe center.  These bit have 1/8" shanks and a working length of about 3/8" and I would guess the amount of bend in some cases exceeded .020".  If the drilling was continued, it invariably would break the drill since the amount of bend got worse as  the depth increased.  I would view the start with a 20x magnifier and if I saw any wobble at all, it indicated a need to recenter the hole.  I would expect the same amount of bending with larger bits assuming the deflecting force was scaled as well.
In my experience, Chinese drill sets need to be avoided.  I would buy a house (= Chinese?) brand from a major machine tool supplier before I would buy a name brand from the local DIY or hardware store.  I can't imagine that MSC or TTC would knowingly sell junk.  Ditto for taps and dies.  I never ever buy cutting tools from HF.


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## george wilson (Apr 9, 2015)

Interesting bending of carbide drills. I only ever use them for drilling out broken taps,so don't have much real experience with them. And then,I only use the straight flute variety,or solid spade pointed ones. I haven't seen small carbide end mills doing any bending without shattering,and I do use them. But must bow to carbide drill experience.

I can see that small carbide drills would bend more than larger ones. I suppose they are thinner in diameter for their length,allowing more bending to take place.


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## kwoodhands (Apr 12, 2015)

RJSakowski said:


> Must be a different manufacturer than the ones I have seen.  Most chip or break at the mere sight of the work.




If I had a set of those drills I could retire my right angle drill.
mike


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