Thread: Lubrication for & sharpening of metal drill bits

Hi Jack,
For a long time the standard was 118 degrees included angle but in the last few years, angles of 135 degrees have been offered fairly often.
In conjunction with a 4 facet grind they centre fairly easily and are less inclined to walk off on you. The shallower angle seems less inclined to "bite" on sheet or thin metal applications on break through.I favour them for this reason.

My drill bits are not for precision drilled holes so I am quite happy to sharpen them myself.No number or letter drills for me ,just general jobber drills.

I hand grind my drill bits on a white aluminium oxide 100 grit wheel which gives a pretty respectable finish .When I work out how to photograph the sods,I'll post some pics.
By current efforts reflect too much light to see any useful detail.

For most DIY people I suspect that as a general drill angle 118 Degrees will do the job just fine in timber and wood.

Grahame

Hi Grahame,
are you talking about the angle that the chisel point makes with one of the cutting edges?
I only ask as that angle is typically 135 deg and I have never heard of the drill angle being that shallow...but then there is a lot i haven't heard about

Phil

Hi Steamwhisperer,
Its the angle that both the cutting edges make each to other ( the included angle).
On a proper split point there is no chisel edge. Its just a point that is the a convergence of the four grind edges.

I can only manage at the moment to produce a 4 facet grind where the chisel point is minimised in comparison to 118 degree bit.Not a true split point.

To do so I will have to dress my wheel edge square and I can't be sure until I try it.The trouble is it is the same wheel do my HSS lathe tools on

The graphics should explain it better than I am able to.

Handskills rule !

Grahame

Originally Posted by Grahame Collins

Hi Jack,
For a long time the standard was 118 degrees included angle but in the last few years, angles of 135 degrees have been offered fairly often.

Grahame,
thanks 118 was what I meant, not 114. I think I may have some 135s too. I recently bought a nice set of Aussie made Suttons. I must check and see what angle they are.
Chris

Originally Posted by Grahame Collins

Hi Steamwhisperer,
Its the angle that both the cutting edges make each to other ( the included angle).
On a proper split point there is no chisel edge. Its just a point that is the a convergence of the four grind edges.

I can only manage at the moment to produce a 4 facet grind where the chisel point is minimised in comparison to 118 degree bit.Not a true split point.

To do so I will have to dress my wheel edge square and I can't be sure until I try it.The trouble is it is the same wheel do my HSS lathe tools on

The graphics should explain it better than I am able to.

Handskills rule !

Grahame

Thanks Grahame,
got it now
A trick I use when grinding is to get two hex nuts and hold them together so the flat of one nut meets the flat of another nut.
This creates a 120 deg included angle for the cutting edge.
This thread has made me think (which hurts a bit) about what lubricant I have used over the years when drilling and it seems I rarely use any. When I was learning the trade the boss normally wouldn't let me. His idea was that the less I used the better I would get at resharpening a drill bit. He had the same idea on the lathe as well. He was right.
I once got called out to the local swimming pool as some guys from Bendigo were fixing it all up.
They were putting stainless steel handrails in and had to drill 3/8" clearance holes in a heap of brackets but had blunted every drill bit they had.
Of course my drill bits were back in the workshop so I grabbed the 9" angle grinder, got one of their blokes to hold it on the ground and used that to sharpen one of the bits.
I used that bit to drill over 100 holes without any lubrication in 316 stainless.
I guess what I am trying to say is, it has a fair bit to do with how sharp the tool is because no amount of lubrication is going to help a blunt tool.

Phil

Read with interest different ideas on drill sharpening & lubes.
I have always used a 118 degree included or 59 degree (each side) all done off hand on a white alum oxide wheel, with a straight cutting oil for smaller drills say 3/8th" & smaller & for larger drills that produce a bit of heat a squirt with soluble oil seems to work well.
The cutting oil does assist the cutting action & keeps things running smoothly.
Everyone has the own methods, but this works fine for me.
regards
Bruce

Originally Posted by Pete F

I'm keen to try 4 facet sharpening as from what I've read it is a far superior cutting process. Many of my drills are split point, and I've seen the advantages first hand of doing away with the chisel point where accurate location on a punch mark and easy of drilling is desired. I'm not sure if 4 facet geometry last as well between grinds, but I'm certainly curious enough to want to try it.

It doesn't but who cares - a split point is a lot easier to grind and re-grind.

My eyesight is poor enough to make sharpening drill bits less than 5mm a bit difficult these days but with a thin sharp wheel, I can do 4 facet split points down to maybe 3mm. Smaller than that, I don't bother really, they're cheap enough to treat as disposable.

As for automatic transmission vehicles, I've never owned one. I don't even like the push-button electronic switching into 4WD and low range on my Rodeo.

PDW

Originally Posted by Pete F

While not strictly related the the initial question, I think all the responses are in reference to drilling, and hopefully useful in their own right.
....

....
Given that it's a similar process (albeit different angles) for 4 facet drill sharpening, it will be interesting to see if I can achieve equally good results on the T&C grinder with drill bits, possibly using a similar setup.

Pete

You are absolutely right Pete, it is very hard/impossible to make anything perfect, but I always want to see the data and the methodology: ie how much effect does the grind really effect the hole geometry.
I have had a look around to see if I could find some data on the tolerance of holes produced by of hand ground drills verse machine/jig ground drills and I have not found any yet. Personally I can re-grind a drill to an acceptable level on a fresh dressed fine grit wheel. And by acceptable I mean can't recall ever having drilled a hole outside the permissible error that made it unsuitable for it's purpose unless you count drilling in the wrong spot. That being said I don't drill deep precision holes with twist drills and if it needs to be straight I'll bore it, small precise diameters or high level of circular I'll ream it and if it is high level of positional accuracy i'll spot drill on a mill first.
-Josh

Personally I can see and feel the difference between grinds of factory ground drill bits, so I'm quite certain there would be a similar difference to hand ground ones.

Originally Posted by Steamwhisperer

Thanks Grahame,
got it now
A trick I use when grinding is to get two hex nuts and hold them together so the flat of one nut meets the flat of another nut.
This creates a 120 deg included angle for the cutting edge.
This thread has made me think (which hurts a bit) about what lubricant I have used over the years when drilling and it seems I rarely use any. When I was learning the trade the boss normally wouldn't let me. His idea was that the less I used the better I would get at resharpening a drill bit. He had the same idea on the lathe as well. He was right.
I once got called out to the local swimming pool as some guys from Bendigo were fixing it all up.
They were putting stainless steel handrails in and had to drill 3/8" clearance holes in a heap of brackets but had blunted every drill bit they had.
Of course my drill bits were back in the workshop so I grabbed the 9" angle grinder, got one of their blokes to hold it on the ground and used that to sharpen one of the bits.
I used that bit to drill over 100 holes without any lubrication in 316 stainless.
I guess what I am trying to say is, it has a fair bit to do with how sharp the tool is because no amount of lubrication is going to help a blunt tool.

Phil

Phil have to agree with you that lots drill users out there can drill holes but sharpen? whats that.If you ever been to many auction sales and see the amount of blunt drills in tins and such especially cockies sales and old garages and workshops.Sutton etc never will go broke while the majority of users [drills] keep ''bluntin n buyin''.My 0.02 cents worth.

Originally Posted by Steamwhisperer; aka Super Guido

so I grabbed the 9" angle grinder, got one of their blokes to hold it on the ground and used that to sharpen one of the bits.
I used that bit to drill over 100 holes without any lubrication in 316 stainless.
I guess what I am trying to say is, it has a fair bit to do with how sharp the tool is because no amount of lubrication is going to help a blunt tool.

Phil

There is a parallel discussion about honing guides for sharpening chisels and plane blades, the story that sticks in my mind is the one about Tage Frid ( a famous craftsman furniture maker ) who used to astonish his students by sharpening his chisels on an upturned belt sander ** and touch up on a polishing mop, took him just seconds to get razor sharp edges. Never used a jig or honing guide...

I'm probably the worst off-hand drill sharpener around, ( I need lessons from Guido! ) I fall in a heap with anything less than 1/4" give me a 1" drill bit and I'll do a half decent job. But they always get the hole drilled and if it's accuracy that to job requires then I'll bore it, or ream it.. 99% of the time it's just a hole to put a bolt through.

Regards
Ray

** One of his students actually asked him where did he buy his ultra short bench chisels..

''Guido will live within this thread forever!

You guys sure must ream lots of holes. Personally I drill a $%^&-load of holes, many need to be relatively accurate, the majority don't need to be. On the other hand I can honestly say I very VERY rarely need to ream a hole, in fact don't even own a full set of metric reamers! The middle ground, an accurately drilled hole, is almost always quite good enough. Clearly I'm just a hack.

Pete

Originally Posted by Pete F

You guys sure must ream lots of holes. Personally I drill a $%^&-load of holes, many need to be relatively accurate, the majority don't need to be. On the other hand I can honestly say I very VERY rarely need to ream a hole, in fact don't even own a full set of metric reamers! The middle ground, an accurately drilled hole, is almost always quite good enough. Clearly I'm just a hack.

Pete

No, your standard of 'good enough' may just be a lot higher than, say, mine.

I can't actually, offhand, remember the last time I reamed a hole to size (probably back when I worked on guns many years ago) but keep in mind that a 12mm hole is small for a lot of what I do, and tolerances aren't that tight. Also if I need a hole pretty much on size I'll push an undersized hand-sharpened bit through then follow up with a factory sharpened bit to size. If it's over say 16mm I'll bore it to size if I want it spot-on.

Tap drills are where you need to be a bit more fussy but for a lot of the small sizes, I keep a tap drill, clearance drill and the taps in a little ziplock bag. Those drills ONLY get used for making holes to be tapped.

I have a lot of drill bits - my father couldn't sharpen them so I inherited boxes of blunt ones. I'm still using them up in sizes from 1/4 to 1/2.

PDW