# Sharpened large drillbits not cutting



## Ttrees (14 Mar 2017)

Hello all
I've looked through a few pages here and not found results,so I thought I might as well ask...
Having watched a good few youtube videos, I am managing to properly get the sharpening of drill bits 
under my belt.... however,
I am surprised not to stumble across the problems I have encountered.
I am not sure whats going on here, and am looking to find out what the problem is.

Having bought a box of Silverline blacksmiths drills and one or two extras I found them good initially.
I probably overheated these in the past, due to being afraid of grinding them down to nothing when practicing.
So I held it off, and slowly drilled the holes I needed taking hours ....

Recently I have been trying to drill a hole in 40mm thick stock that was welded to a thick plate.
I have been drilling out this hole to 22mm plus (damaged bit)
The hole has to be a tad less than my 24mm bit ...
it is for a sleeve on a motor shaft to fit into a pulley .
Anyway
I spent two hours... or probably far more than that drilling this hole 
During this time I managed to get my sharpening skills down and experimented with angle changes,
and was highly critical of my results, so strived for perfection .
End result was very sharp cutting edges , correct relief ground in a single swooping facet .
Still no cutting !
I was going up the bits in stages successfully until I got up to about 16mm and then the cutting stopped.

I don't think the tempering was at fault here, as I managed to cut with an overheated bit from grinding
easily ...evident from the blueing on the edges ,
Plus wouldn't the edge get dull on a bit which was annealed ?
Maybe my 40mm stock got work hardened or changed temper ?
Or was it that I should not be drilling these holes in stages of 2mm at a time, and try and get the drill to
bite into more meat to self feed itself and cut more aggressively.
My bits remain sharp after this drilling ceased .
Could the flutes be the problem here ?

Thanks for any advice 
Hope I can get some answers 
Tom


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## Bigdanny (14 Mar 2017)

That sounds like a lot of metal to remove with a drill. I am no expert but I would probably try a decent holesaw, make sure you keep the swarf cleared more or less constantly with an airline. Other methods might be if you have a friend with a plasma torch. I am guessing the hole will be covered by a bearing holder so doesnt need to be too accurate.
Hope this helps a little
D


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## Ttrees (14 Mar 2017)

Hello Danny 
The actual size of the hole is not the problem, I just need to find out why I am having this issue in the first place.

It defiantly needs to be accurate though, as I am making a sleeve for a motor shaft. 
This is for a tablesaw, so is a 2 pole motor and as you can see if it does not fit correctly it will wear the keyway.
I have since welded this and filed it, and now I'm just waiting to turn this sleeve on the motor once I get the 
hole drilled to an accurate size ... VFD in use so adjustable speed .
I might file this last sub 2mm actually, as my 24mm bit is too large and the motor shaft is not quite 24mm .
I have done this allready with the pulley .

Thanks 
Would love to read some link or something describing the issues I've been facing.
I would also like to know if anyone has taken 0.5 mm off a drills thickness also.
From what I've seen this is not possible ...although most are not as stubborn as I .
If my "final cut" cheapo 24mm drill is only a one time deal and is for the bin allready, 
then will it cut at all if I reduce the diameter ?, any less than the rest of them ?
Tom


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## sunnybob (14 Mar 2017)

You mentioned the dreaded "S" word.
Dunp them. Youre just wasting your life trying to cut through metal with them.

Buy some decent drills from a proper engineering shop (ebay works, just not the make you already have) Dont buy gold coloured ones either.

To drill a 24 mm hole through metal should done in at least 4 stages. start at 6 mm and go up another 6 mm each time as an absolute minimum.


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## Sheffield Tony (14 Mar 2017)

You mentioned welded - are you drilling near the weld ? That can leave the hardness a bit unpredictable.


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## Bigdanny (14 Mar 2017)

Ah now I see pics it makes more sense what you're trying to do.
On the drilling , sharpening thing not sure what the prob is, I watched a vid on youtube from Ave recently and as long as the flutes are clean and a drop of oil to lubricate then should be ok, if the angles of sharpening are good then its down to loss of temper. 
But seeing what you're doing I would talk to a lathist and use a boring bar or fabricate the pulley as one to fit on the shaft of the motor.

Good Luck
Danny


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## Ttrees (14 Mar 2017)

Yes I have heard of these things being referred to as the dreaded "S" 
I want to know why though, 
I know they wont cut now, but they did for a time....quite some time ..
Enough for me to get my moneys worth outta them.
The pack cost about 20something quid ...
And a single drill of say, more than 20mm would be in the region of about 30something pounds...

There was no titanium nitride coating or other kind from what I could see.
Why have these ceased to cut ?
Is it the flutes ....
Has there been a taper worn (insert correct terminology here) into the first inch or so ?
I have seen worn flutes on some drillbits on various youtube videos, with no mention of reduced 
effectiveness.

Thanks for reading 
Hope to get to the bottom of this :roll: 
Tom


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## Ttrees (14 Mar 2017)

Sunnybob 
I have been drilling these holes in stages ...
I was worrying that I was doing so in too many stages.

Tony 
Possibly you are onto something here 
As the larger the hole I cut, the closer to the welds I'm getting ...

This round stock that you can see is 40mm tall, and was welded to the plate in the same orientation as shown,
Plate was underneath ..It was some kind of prop ...
Big beefy 10 or 15mm plate with heavy round bar welded to it and a champfer on the top.
It might have got hotter again with me cutting it with an angle grinder

If this were the case though, would the start of each size bit used not be much faster cutting, 
as the weld was on the bottom of the stock .

Danny 
I'm the only machinist I can afford :lol: 

Thanks for the input guys 
Tom


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## Phil Pascoe (14 Mar 2017)

I needed a 16mm blacksmiths and got it on ebay from UKDrills for £2.56 inc. P&P. Sometimes their stuff is cheaper on ebay than straight from them. 15/16" would give you a minute amount under 24mm if you could find one.


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## Ttrees (14 Mar 2017)

Thanks Phil 
Will try and look for one 
It will save me thinking about possibly reducing the size of the 24mm one 
Gonna go searching
Cheers


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## lurker (14 Mar 2017)

What sort of speed (rpm) are you drilling at?
It needs to be really slow 

If the bit is not visibily cutting then all thats happening is you are case hardening the workpiece via friction


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## Ttrees (14 Mar 2017)

Lurker
I have not been adhering to this rule. 
My drill press is not equipped to run that slow.
I have been using loads of coolant and the drill is not hot, but the workpiece is very warm 
You seem to be correct.
I take it it's still possible though, as I think I have experienced a dull drill getting quite hot
eventually getting through the hole, and then change to a bigger drill and it sails through the work.
I think a new bit would sail through this ...
I could be wrong though ?
Tom


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## lurker (14 Mar 2017)

If you sure its not getting hot you could still be work hardening it.
A very common failing when drilling stainless steel (I realise you are not drilling SS)


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## CHJ (14 Mar 2017)

lurker":1ebjscog said:


> .....If the bit is not visibily cutting then all thats happening is you are case hardening the workpiece via friction




+1 for that. It was my first reaction.

Too high a cutting speed. (you probably need to be able to watch the flutes rotate)
Too little feed pressure.
Too little cooling/cutting lubrication.


The very fact that you are quoting such long times to drill the holes indicates the above to me.

Drill swarf should be hot, possibly Blue, Drill itself should be warm with no discoloration.

What HP and size of Pillar drill are you trying to do the job on? in my last shop to drill holes in steel plate of those dimensions we used a radial arm drill weighing several tons with power feed.

Sorry but personal reaction is to cringe at making a shaft sleeve that way, for something that is going to run at those RPM and requiring good balance. I'd seriously recommend asking for help from someone with a lathe.


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## wallace (14 Mar 2017)

My drill was too fast for doing large holes in metal so I found it worked better doing them free hand in a variable speed hand drill. If you can clamp the item on the floor and work above it exerting a reasonable amount of pressure whilst keeping the speed down.


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## Phil Pascoe (14 Mar 2017)

24mm holes in steel with a hand drill, Popeye? :lol: Really?


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## Ttrees (14 Mar 2017)

Thanks guys 
I managed to find a set of drills on eBay with a 15/16" one up to an inch.
I might go this route.
I have managed to drill steel up to 25mm with these Silverlines before ...
I think I might be able to get it done again.
I can always drill for a second and let it cool off and repeat.
Its not like I'm drilling multiple holes and am doing this to a deadline.

I might check what the shaft diameter is before I choose to go this route 
If the 15/16" hole proves too large, I will have to make another marking tool to file to 

Here is everything at present 
Was planning to bore the aluminum out now that the hole is centered ...
Either that or use the sleeve as a marking tool ...

Still curious if anyone disagrees with me about a new drill cutting this a LOT faster ?
Tom


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## Inspector (14 Mar 2017)

I would just hunt down a steel reducer bushing, shaft adaptor or shaft sleeve in your area. Or have a machinist turn it on a metal lathe. You've work hardened the steel (see if a file skates across your sleeve) because you can't remove the metal fast enough and if you get a quality new bit it may be dulled in seconds when it hits the hardened area. That would be better turned to size and then bored out on a metal lathe plus it would have the advantage of being concentric. what you will end up within a wobbly pulley that will wear out, possibly wrecking the shaft. You don't want wobbly pulleys on a table saw.

https://www.grainger.com/product/DAYTON ... ?$smthumb$

https://inverterdrive.com/group/Gearbox ... r-to-19mm/

https://www.fastenal.com/products/power ... pters%22|~

Pete


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## pcb1962 (14 Mar 2017)

You really should find someone with a lathe. If you tell people where you are perhaps someone will offer. If you're anywhere near me I can make you a reducer bush in 20 minutes. Cutting the keyway may take slightly longer.


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## Ttrees (14 Mar 2017)

So it seems theirs mutual agreement that the piece is work hardened ...

It wont bother me as its only less than 2mm to remove ....
It wont bother me regrinding the bit being dulled either...I've sussed that part.
I can make another center marking tool for the sleeve OD 
and I can rig up an angle grinder and turn the workpiece on the motor spinning at a low RPM and get it close 
And follow up with a file being jigged up or something similar.

I wont have a wobbly pulley and I can't see how I would destroy shaft as I can just weld it up again.
]I like challenges anyway  
Its the best way to learn 
Thanks 
Tom


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## -Matt- (14 Mar 2017)

Agree with all said. Where I work we have a big gear head 4 bank pillar drill and its slowest speed is 104rpm. Might still be a little quick in some ways but I've put an inch drill through 15mm plate no problems. Bit softer on pressure and a good feed of cutting grease, from pilot to finished in about 10 minutes.
I'm also interested in your sharpening, I assume you've the angles all right?


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## Ttrees (14 Mar 2017)

Ya, have even experimented with various angles and went back to the regular shape ...
Somewhere between 118 and 120 I believe.
Easiest way to see, is by getting two large nuts and putting them together to reference the tip against .
Using a disc sander, so a bit mire straight forward ...although not thinning the web....
Doesn't seem much point, as I am using the outer part of the drills for enlarging large pilot holes at 2mm stages.
Making sure to measure the cutting edges so they are the same length.
Started out grinding with the drill aimed to the left, but switched after that to the opposite orientation as I find it 
smoother to get a swooping single facet 

Have found these videos good watching ... in order of appearance. 
https://www.youtube.com/watch?v=xJtYBU2BAMY

https://www.youtube.com/watch?v=FgcESWoJ3CU

https://www.youtube.com/watch?v=y0SQkzScQk0

Tom


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## -Matt- (14 Mar 2017)

Thats how I was taught using the two nuts.
Can do it by eye now so it must work I guess!


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## novocaine (15 Mar 2017)

so you talk about your included angle, what are you grinding the relief too? 
for very hard stuff you want an included angle i the 125-135 region, especially on big stuff like that, although as you are step drilling it, the angle makes very little difference. 
can you take a few pictures of the tip of the drill bit, preferable straight on so we can see the angles a bit better.

have fun, and do as everybody says above, go slow. if you can't go slow, lubricate.


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## Ttrees (15 Mar 2017)

I will take a piccy or two of the bits later on tonight,
I have been getting good at grinding the relief as I mentioned that I switched orientation after a while.
I done this because I found I can get a nice swooping single facet easier, with the drill aiming towards the right and lifting up to
taper the heel as to not ride on the heel .
This was what I thought the problem could be at a stage.
I wonder how long I can remember this skill and sharpen a bit first time...say after a break..
I really felt I got it down now though 
Not that I'm going to be taking a break from drilling anytime soon (hammer) 
Have to measure that shaft today 
Tom


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## Ttrees (17 Mar 2017)

Checked the motor shaft today and the shaft isint as small as I thought it was...
Defiantly not 15/16", so I am quite happy as I don't have to spend 50 odd quid on imperial bits  .
If the shaft proves to small in spots it will get a bead of weld ....
So I just drilled the sleeve out to 24mm and it was easy and quick...
I had to sharpen it beforehand and take a lot off the heel for there to be an acceptable relief angle.

The metal piece was not hardened or hot or neither was the bit 
Guessing this bit was not used as often ..I can't remember 
So I am baffled as to why this drill was so quick .

I still suspect the others have a worn taper in them ?
The only thing I can think of is I ground more relief on this one and didn't do it in one facet as it would have been wasteful. 
,it was a mess before I started (angle wise)
I still think the relief on the other bits is more than enough though.

Now to make a jig that will score a line for the outside of the sleeve so I can grind and file to it.

This subject should be well discussed 
I can't be the only one using large cheap bits with a regular pillar drill .

Thoughts ?


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## Ttrees (17 Mar 2017)

Hi again folks 
Doesn't seem like there is folks who use cheap large bits in a pillar drill ...
Strange as I got my old drill for 40 pounds plus the petrol to get there, and the bits cost about 25 say ...
This kinda thing should not be uncommon.
I must point out that it is not necessary to have a real slow drill here with a half ton power feed unit.
You can drill slower than the drill RPM if you want to, by not allowing it to speed up again and feeding it into the work.
So on to measure how tightly this sleeve fits on the shaft ....
Fingers crossed its a good fit .
then its a case of grinding a down to the line, and then filing down to get a press fit.
I mentioned that the pulley is aluminum so I should be able to mark it with the sleeve and file/sand/scrape the high spots to 
get a nice press fit .
The jig I made for marking is not precise enough to trust. 
Made another score on the pulley, as I only scored the line to the edge of the out of center edge last time.
this one will make it perfectly centered .
I might wrap a bar around paper and sand it down to final dimensions .
Goin at the base for the saw today though, so I can clean the shop up a bit.
Will keep you updated 
Tom


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## Ttrees (29 Mar 2017)

Got back workin on the sleeve today after painting the mobile base I was making.
Nearly getting close ....Never filed on a turning piece before, quite fun  
especially after angle grinding for the last few days.
Will be getting close tomorrow and making the sleeve fit on the pulley, 
After that making a new key.

I think I might have to take this sleeve off to file the key slot ...that won't be easy.

Close to getting this tablesaw going
Wish me luck
Tom


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## AndyT (30 Mar 2017)

I think the reason why there weren't lots of responses from other people drilling big holes is possibly that many hobby metalworkers will have a lathe and use that instead, to bore big holes rather than drill them. A boring bar covers a wide range of hole sizes and costs a lot less than a set of large bits. Also, you don't need so much power as you can take a very fine shaving. 

I must say it's interesting to see someone problem solving to suit the tools available but I wonder if you have thought about getting a lathe - you might enjoy the extra scope it would give you for making bespoke parts.


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## DTR (30 Mar 2017)

AndyT":m6j4xpv0 said:


> I think the reason why there weren't lots of responses from other people drilling big holes is possibly that many hobby metalworkers will have a lathe and use that instead, to bore big holes rather than drill them. A boring bar covers a wide range of hole sizes and costs a lot less than a set of large bits. Also, you don't need so much power as you can take a very fine shaving.



Absolutely this. Despite having a vintage Walker Turner pillar drill and a jig borer(!), I still resort to the lathe for most things over 3/8" diameter. Boring has other advantage too, such as more accurately sized and shaped bores, better surface finish, and no wandering off course.

Edit: Just to clarify, I do use bigger drill bits in the lathe up to about 3/4". The lathe is quite comfortable with these due to the slow speed and high torque. My Walker Turner pillar drill has the option of an intermediate (third) pulley to gear the spindle down further; this is something I want to do one day.


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## Ttrees (30 Mar 2017)

I have thought about getting a metal lathe Andy, but there's a few more tools to acquire first before going down that rabbet hole. 
A Thicknesser planer might be handy... although, I am really set on making a large cyclone DC after working on this saw....
And the other one. 
I nearly bought a wood lathe not so long ago. that's on the list too

But you're right a metal lathe would open up a world of possibility's, never needing to buy anything again.
Other than tooling and everything else that you might "need" for it :roll: 

I'm always looking around, for an old lump needing work that can be fixed up, that's only weighing a moderate amount.
I have plenty of stuff to do in the meantime though.
Hopefully get this done today or tomorrow.
Tom


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## heimlaga (18 Apr 2017)

I occasionally drill holes up to 31 mm in diametre in my Arboga G2508 drill press. At 100 RPM for anything over 15 or 16 mm in diametre. With lots of coolant.
The biggest hole I have ever drilled was 30 mm in diametre and some 60 mm deep when I drilled out the shaft from a flat belt pulley. I think I was seriously pushing the limits of my drillpress doing that.

Though a 20 mm hole is very big for any ordinary belt driven drill press. 

The main downside with drilling out a hole in a pulley is that drilled holes usually aren't round. Particularly not if there is a key slot or a hole for a grub screw somewhere. Making the hole centered would be very hard too.
I always aske a machinist friend to bore out pulles for me in his lathe.


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