Thread: Lubrication for & sharpening of metal drill bits

Proficiency in this type of grinding drill bits only comes with practice and more practice.Observation and listening to the way the drill cuts.Even curls is what you want tells you whether the drill is even cutting. noise well its rubbing.is the old saying if at first you don't succeed try.....................again.
Another thing I do is put all the blunties in a tray or tin and on a wet day and all the H M Indoors chores are up to date.Retire to the shed and have a grind up. Spose it was old farm days training wet days are best spent in the shed '' make n mend''.Small drills can get a keen edge with a oil stone or a slip stone.There are drawings around for stone sharpening guides.
Free hand my method is 1 angle 2 chisel 3 back clearance.The old man liked to radius on the back cut , me sharp angle is close to 4 facet without the fuss.0.02 cents worth.Cheers John.ps one thing more on non super accurate holes I always sink a pilot hole first.Accurate stuff spot first with a centre drill.If you are well equipped can have pilot drill in one drill always and the other free with your size hole drill. J.

Originally Posted by Pete F

Here you go. http://www.oliverinstrument.com/MoreandBetterHoles.pdf

The material and explanation of how drill point grind affects accuracy is on pp 896-897 of the MH 29th edition.

Pete

Pete,

I looked up the oversize drill chart in the MH29 pg 897 for 1/4" All these dimensions are oversize from nominal:
Average Maximum 0.0065"/0.165mm
Mean of 0.004"/0.102mm
Average Minimum 0.0025"/0.064mm

I had an occasion to drill some 30 5mm holes in some 15 mm 4140 flat bar earlier today. My 5mm nominal drill bit needed to be re profiled as I had last used it to drill some sheet aluminium. So over to the grinder with the CBN wheel I took the drill and put a new tip on it completely freehand and by eye(no jig, no template) 20-30 seconds later I have a drill nice and sharp and good enough in my reckoning to do the job (M6x1.0 tap holes). The actual job did not need a precise diameter but precise location (better than 0.15mm) but I thought it was a good enough opportunity to test what kind of tolerance my free hand dill sharpening would produce.

After I had drilled all my holes I measured them all up with a 2 pin internal micrometer (I don't have a bore mic that small) and checked the spacing (positional variance).

As expected the holes was oversized with an average diameter of 5.05 -5.07, position accuracy was a little better at 19.33-19.39mm with most spot on +- 0.02mm.. They are all straight in-line and against the ground reference edge they are +- 0.02mm..

In other words holes produced by my freehand grind are all well within the specs that can be expected for a correctly ground drill according to MH29.

I could not be bothered to set up and test for cylindrical or straightness as I had to get on with tapping the holes and they where not critical metrics.

Data for thought....

-Josh

Great

Originally Posted by Brobdingnagian

Pete,

I looked up the oversize drill chart in the MH29 pg 897 for 1/4" All these dimensions are oversize from nominal:
Average Maximum 0.0065"/0.165mm
Mean of 0.004"/0.102mm
Average Minimum 0.0025"/0.064mm

I had an occasion to drill some 30 5mm holes in some 15 mm 4140 flat bar earlier today. My 5mm nominal drill bit needed to be re profiled as I had last used it to drill some sheet aluminium. So over to the grinder with the CBN wheel I took the drill and put a new tip on it completely freehand and by eye(no jig, no template) 20-30 seconds later I have a drill nice and sharp and good enough in my reckoning to do the job (M6x1.0 tap holes). The actual job did not need a precise diameter but precise location (better than 0.15mm) but I thought it was a good enough opportunity to test what kind of tolerance my free hand dill sharpening would produce.

After I had drilled all my holes I measured them all up with a 2 pin internal micrometer (I don't have a bore mic that small) and checked the spacing (positional variance).

As expected the holes was oversized with an average diameter of 5.05 -5.07, position accuracy was a little better at 19.33-19.39mm with most spot on +- 0.02mm.. They are all straight in-line and against the ground reference edge they are +- 0.02mm..

In other words holes produced by my freehand grind are all well within the specs that can be expected for a correctly ground drill according to MH29.

I could not be bothered to set up and test for cylindrical or straightness as I had to get on with tapping the holes and they where not critical metrics.

Data for thought....

-Josh

Sorry Josh but I have been told that's impossible unless you have a drill doctor
looks to me like your holes are nicely in spec.
Well done.

Phil

Originally Posted by Steamwhisperer

Sorry Josh but I have been told that's impossible unless you have a drill doctor
looks to me like your holes are nicely in spec.
Well done.

Phil

Really, by whom Phil?. Nobody on this thread has ever claimed any such thing so I wonder where you would get such information from. The discussion here was that a good quality machine, of which I personally wouldn't necessarily claim the DD as one, will sharpen drills more accurately than any human is capable. The more accurate drill will drill more accurate holes, hence why industry spends sometimes 10s of thousands of dollars equipping their toolmakers and other skilled employees with expensive drill sharpeners instead of a 200 buck grinder and an over-inflated ego. Immature pi$$ing contests not withstanding, I'm going to guess plants that run tons of steel through every day might know a little about the topic, but apparently not

Originally Posted by Pete F

Really, by whom Phil?. Nobody on this thread has ever claimed any such thing so I wonder where you would get such information from. The discussion here was that a good quality machine, of which I personally wouldn't necessarily claim the DD as one, will sharpen drills more accurately than any human is capable. The more accurate drill will drill more accurate holes, hence why industry spends sometimes 10s of thousands of dollars equipping their toolmakers and other skilled employees with expensive drill sharpeners instead of a 200 buck grinder and an over-inflated ego. Immature pi$$ing contests not withstanding, I'm going to guess plants that run tons of steel through every day might know a little about the topic, but apparently not

Ummm... I'm Pretty sure that was you Pete

Originally Posted by Pete F

It's why large large production shops buy drill sharpening machines costing many tens of thousands of dollars instead of some old bloke with a fag hanging out the corner of his mouth and a hanky with knots in the corners draped over his head who answers to the name of Guido! If a drill doesn't have nearly identical cutting surfaces it won't drill round or straight holes, end of story. Sorry Guido. Not that twist drills are especially good in that role anyway ... but that's another story.
Pete

I think the theogony of Guido - The Original Drill Doctor predates solid carbide, indexable/custom tooling in production and a modern supply chain.


I'll note here my drill grind was far from perfect, it was passable and by passable I mean that it cut without forcing it, uneven spirals and yet it still produced holes that are within spec but it is probably only a 100 (3xdia) hole drill bit. I'm fine with touching up a drill every 100 or 200 holes as I'm not chasing 100% efficiency or high repeatability with drilling.


Pete, I would suggest to you that in production cycle time and down time to change out worn bits are the more important metrics for determining effectiveness of drilling system. I believe this is what you mean when you say "more accurate drill will drill more accurate holes" but it is not explicitly clear that is what you meant. In that case it may well be better to use a high end drill grinder to re-sharpen twist drills to gain a %5 increase in production, or as is becoming more common (according to an engineer at Sutton) is to outsource the problem entirely to the original tooling maker eg Suttons or a third party that reconditions tooling to as new performance including coatings. The reasoning being that they don't need to spend time / floor space and production hours on resharpening or training and produce holes with less variance.


How much of this is applicable to a small/home shop where 99% of us are?.....


-Josh

I have said it, you have quoted it, and I don't even understand what the complete waste of time is all about. Inaccurately ground drill bits don't drill accurate holes. End if story. You want to believe differently, knock yourself out.

Originally Posted by Pete F

I have said it, you have quoted it, and I don't even understand what the complete waste of time is all about. Inaccurately ground drill bits don't drill accurate holes. End if story. You want to believe differently, knock yourself out.

Here are the relevant points for you Pete:

1. I don't have to believe it, I can measure it....

2. A drill does not have to be perfect.

3. Any skill should be cherished and nurtured as it will tend to give the person that persists a deeper more subtle understanding and sensitivity to the work not to mention an greater flexibility in its application.

-Josh

Ok guys,

Hopefully, we all now understand each others point of view on the pros and cons of grinding drill bits..
Now would be a real good time to stop,before further comments get out of hand. Let's put it behind us and we will agree to disagree.

Lets all play nice together.

OK?

Grahame

Well I am hardcore, I sharpen mine one the closest rock with just a bit of spit for lubrication...

None of this pansy fancy bench grinder or drill doctor stuff for me.. I am a real man...

Now back to work on my pink 10EE..

Originally Posted by Brobdingnagian

Here are the relevant points for you Pete:

1. I don't have to believe it, I can measure it....

2. A drill does not have to be perfect.

3. Any skill should be cherished and nurtured as it will tend to give the person that persists a deeper more subtle understanding and sensitivity to the work not to mention an greater flexibility in its application.

-Josh

plus 1

A drill that is not ground accurately will not drill an accurate hole.

For the record I just took a brand new Presto 5 mm drill. I had intended putting it in a collet pre-drilling it using the mill, but instead just chucked it in a POS Chinese drill press and went at it, straight through some 10 mm hot rolled. I was curious as to what would happen, so worst case, as I've never bothered measuring this type of thing before. So I then measured the results with a Mitutoyo small bore gauge. Result 5.03 mm, twice as good as the result above. I then took a P&N VERY worn 5 mm, as it's a size I use a lot. Result 5.06-5.07 strange I thought as I normally try to keep my bits sharp. No matter, I took the drill doctor, a device I'm not especially fond of by the way, but it was cheap enough and seems to get acceptable results. 30 seconds later including unpacking, as I keep it on a shelf in another room. Some more holes, 5.04-5.05. Not as good as a fresh drill but nor should it be I guess. However the previous version of it was clearly slightly blunt.

Did I mention a drill that is not ground accurately will not drill an accurate hole? Add blunt to that.

Quite why some see this as somehow a test of their manhood is beyond me. An inaccurately ground drill will not drill an accurate hole. It is the reason companies have very skilled people in tool rooms that are reduced to little more than machine operators, as they receive tooling in for resharpening and use their very expensive drill grinders to repoint the bits accurately, instead of freehand, as they are all perfectly capable of. Is freehand grinding a skill to be admired and "cherished"? You better believe it is! I have repeatedly said as much in this thread, and I take my hat off to those who can do it well. I can't. Further, is a Drill Doctor the "be all" that some may suggest it is? Absolutely not. Personally I'd consider it the entry level drill grinding machine that is only just up to the task in a home shop. Just. However it will almost certainly produce a more accurate grind than a human can, and the more accurate the grind, the more accurate the hole. Did I already mention that?

So once again, if anybody wants to believe that an inaccurately ground bit will produce an accurate hole they can knock themselves out. The moral of the story is Ya gets what ya pays for. The bottom line is that normally all this is moot anyway, as most of the time holes aren't required to be drilled this accurately, at least not in a home shop, but to suggest a drill can be ground any old fashion and produce an accurate hole is just plain wrong. End of story.

Pete

edit: yes a good suggestion Grahame I have no interest in pursuing the matter any further, as drilling pointless holes in perfectly good steel and measuring them to prove what is a well known fact is 30 minutes of my life I will never get back! I agree to disagree

I've haven't been following this thread too closely, so I'm sorry if this has been said already. If you require an accurate hole shouldn't you ream it after drilling?

Originally Posted by jack620

I've haven't been following this thread too closely, so I'm sorry if this has been said already. If you require an accurate hole shouldn't you ream it after drilling?

Give that man the Kewpie doll!

What we've now had demonstrated is:

a new drill bit drills a slightly oversize hole.

a machine-resharpened drill bit drills a possibly slightly more oversized hole.

a hand-sharpened drill bit, depending on operator, drills an oversize hole somewhere between the best a machine-resharpened bit will do, and a total mess.

I am sooooo enlightened that I have now seen restated information that I knew 30 YEARS AGO.

And, if I actually WANT a hole on size, I'll drill it undersize and REAM (or bore) it.

So have we finished all the posturing and pointless argumentation now? Because I for one am really, really over it.

Meanwhile I'll keep hand-sharpening my drill bits, first because I CAN and secondly because they drill holes quite accurately enough for my simple purposes.

Next topic - how many Deckel mills can be cut into pieces if you use a planer?

PDW