A while back I had to drill out a bolt and went through several bits. Dulling them, snapping them and as a bonus I also snapped a misnamed easy-out. Buy new bits? Nah, they cost too much for a decent set besides I have probably 100 drill bits. I gotta figure out a way to sharpen them.
DAGS. Keeps coming back with buy a drill doctor. I find the thing from Lee Valley and others that holds the bit at the correct angle to bench grinder for $10.
formatting link
DD and the angle guide don't seem to be doing anything fancy so I think why can't I just do it myself. Here's what I'm thinking please tell me if you think it will work.
Cut a wedge at the proper angle Chuck the dull bit in my drill press Clamp the wedge and a stone or fine file to the DP table Lower the dull bit against the stone or file Keep bit oiled and cool Done
Unless I'm missing something doing it that way would give me the same results as the grinder jig and probably the DD too.
You might get a bit of flex in the drill bit by bringing it down on a slanted stone - especially with smaller bits.
I received a low end Drill Doctor for christmas last year. I hadn't bought one for myself because I was skeptical about it. After using it, I am completly sold on it - great product. Once you are familiar with using it, it only takes about 30 seconds to sharpen a bit and the bit is better than new. Definately worth the price (especially when it's free!!).
You are missing something, and that something is VERY Important.
What you would end up with would be a drill which would not drill into even butter, and would burn up if you tried to drill into anything harder.
On a properly sharpened drill bit, only the cutting edge touches what you are drilling into. That is, that cutting edge extends further out than the back of the flute that the cutting edge is on. The cutting edge is the front edge of the flute, and the back of the flute must taper away from the leading edge. If it does not, then the entire flute rubs and will not cut.
Like a knife, the cutting edge must be at such an angle to what you are cutting to dig in, while the side of the knife would just slide over without digging in to make the cut. The leading cutting edge of the drill bit works the same way.
The drill sharpening guides are made to automatically cause that angle to be ground on each flute of the drill bit evenly, and all flutes of a drill must be at the exact same level, else only one will cut and the other not touch.
Buy the drill sharpening tools and be happy with the results.
You're close Ray. Forget the wedge and all the other stuff. Take a look at a brand new bit and notice how the point is ground from flute to flute. Simply hold the bit against the grinder wheel to achieve the two correct angles (down and left), and then tail it up until you grind to the second flute. Easier demonstrated than explained. You don't need any jigs - besides, they would only be good for one size bit. Practice, examine your grind carefully, test it on some steel, and if necessary, practice some more. Forget the oil too. The amount of time a 1/4" bit should be on your grinder wheel is less than a second per side. If you don't have a grinder a belt sander will do just nicely.
I sharpen all of my own bits except for the very smallest.
Actually drill bits are not that difficult to sharpen on a bench grinder by hand once you understand the proper geometry. Apprentice machinists learn this skill early on.
A visit to your local machine shop with a six-pack in hand might get you a lesson or two.
When I'm working and come across a dull bit, I sharpen it and I'm back to work in less than a few minutes. If I had to go out and replace the bit, it would mean a trip to the store. Now, if you do any drilling in metal, you'd need to buy several bits per project. It might take a while to recoup the cost of the Drill Doctor, but over a year or two the machine would pay for itself.
Another downside to replacing bits when they get dull is that you'd be more likely to keep using a marginal bit until you get out to the store
- whereas with a DD, you can always use a _sharp_ bit every time. It makes a big difference.
After about the third snapped drill bit I think you'll give up on this idea. Moreover, as another poster has mentioned, you will be grinding a cone and a cone can't cut. Period. Not at all.
So let's get you trained to sharpen drill bits by hand so you can amaze your friends, confound your enemies and have a lifetime supply of sharp drill bits at your beck and call.
____________________________
Let's start with a two-flute, 118 degree twist drill. No carbide, nothing fancy at all. It's what you get when you pick up that Vermont American blister pack down at the local hardware store.
Looking straight down at a new common twist drill bit, you will see that the end is made up of three straight lines: two cutting lips and a chisel wedge in the middle. That is, in fact, what each of these edges do.
Notice that the chisel is centered between the two cutting lips. That's where it NEEDS to be. If its off-center, so are the cutting lips and all bets are off so far as the resulting hole geometry.
Now look at the drill bit sideways. Notice that the line running (mostly) horizontally from the edge of each of the cutting lips actually tilts down and to the left a tad. This is the cutting relief angle and controls how thick the waste can be. Low angle, slower drilling, stronger lip. High angle, faster drilling, weaker lip. The relief angle, also, benefits from being equal for each side although the rate of penetration is limited by the shallower side so 'close enough is close enough' (get close, but don't be obsessive about it.
To sharpen:
Dress your grinding wheel flat. Don't even think about skipping this step. If you don't do it now, you will in a minute as soon as you see what your drill bit does when bouncing off an out of round wheel while trying to sharpen a straight edge against a circle with a groove in it and chunks out of it.
Holding the drill bit up to the wheel, angle it so the shank is to the right (for the most common twist ... a right hand spiral). Hold it so that the edge is horizontal. This means that the shank will be dropped backwards to compensate for the lip angle.
JUST BARELY touch the lip to the stone to confirm that the stone is smooth and the drill bit is touching across the width of the cutting lip. Match straight line to straight line. If the drill bit isn't straight across, balance out the curve. If the wheel isn't straight across, you didn't do what I told you to in the very first step. Stop right now, go back and follow the directions. Sharpening drill bits is pretty easy if you don't try to take shortcuts. If you DO try to take shortcuts, it's darned near impossible to do a good job ... more so when first starting out.
Now, with light pressure (until you get a feel for the results) rub the drill bit against the wheel while simultaneously 1) applying increasing pressure (this will become your relief angle ... just about 3-5 degrees is plenty to start with) and 2) rolling the bit between your fingers while lifting the tip upward. This is the 'skill' part. You need to make these two motions in concert with each other so as to end up with a tapered cone / flat spiral that starts with the cutting lip and drops back slightly at the back of each flute. This is the part your jig could not do.
Now check to see how you did on this first lip. Be critical of your results. No slack. It probably looks horrible. See that flat spot right at the lip and that grind mark on the other lip where you didn't pull away from the stone in time? That's about par for the course. If it doesn't look like this, chalk it up to either lax standards or beginners luck. Experienced people will sometimes get these marks if it has been a while since they had to sharpen a bit. The key is to hold yourself to high standards and not quit until you achieve them.
Try again on the second lip. When you check the second lip, also look at the drill head on to see if the chisel is centered. If it isn't, re-grind the longer of the cutting lips, being certain to duplicate the angle on the shorter lip.
It is a good idea to have a water cup handy to quench / cool the tip after each pass over the grinder. HSS air hardens so we are not too concerned about the hardness of the steel, but ARE concerned about your ability to hold a piece of hot metal in bare hands. If it's too hot to hold comfortably, it's too hot. Cool it. It's a good practice to cool it after every pass over the wheel but if you are making light cuts, you may get a couple passes in before things get uncomfortable.
You can buy a cheap drill gauge at pretty much any tool outlet store ... the General brand is as good as any ... which is to say that none of them are anything more than approximate. Or you can use a pocket scale (machinist term for ruler) with fine gradations of at least 1/32 to measure the cutting lips (when they are the same, the wedge is centered) and the relief angle (hold the scale horizontally and check to be sure that the relief is the same -by eyeball- for both flutes. A protractor with a long arm (again, the General brand is fine) will help you determine the precise included angle of the lips. To use the protractor, align one edge with the shank of the drill and the swing arm with the cutting lip. It should be half of whatever angle you are looking to make AND the lip should be straight from corner to corner. Profile it against a good source of light.
Gotchas:
Make certain NOT to round off the corners of the cutting lips. No matter what the rest of the lip looks like, if the corners are rounded, the drill is dull. If the corners were rounded during use, continue grinding until you get past them while meeting all the other conditions above.
Make certain NOT to grind a flat at the cutting lip ... it MUST be the highest point on the flute. That is, if it is flat, it will rub, not cut. If it is flat and the other lip is good, you now own a 1-flute drill which will cut ovals for you. For a while.
You will probably be able to sharpen drill bits down to about 1/8" using this method. Below 1/8" things get iffy quickly so your best bet may be to simply purchase a new bit.
Nota Bene: If you snap a good-sized drill bit (oh, say, somewhere north of 1/4"), grind the shank off and then, while chucked in our drill press or lathe, grind a cone on the end. This simple device is useful for 1) marking where a drill bit will enter work on the drill press or 2) for hand tapping on the drill press.
To hand tap on the drill press, first drill a hole to the proper size for tapping then, without moving the workpiece, insert the tapping center you just made into the chuck. Then place the tap and handle between the workpiece and the tapping center. Many taps and T-handles have a recess precisely for this purpose. Then apply light pressure to the drill press quill while turning the tap with the other hand. Voila! A perfectly vertical tapped hole!
If the workpiece gets nudged before you can get everything set up, use the tapping center to re-locate it ... a hole will locate precisely on a cone.
When I first entered the machine trades I was given a thread gage and
100# or so of mixed bolts to sort. I can tell metric from English and the various sizes and thread in each group by sight to this day ... and I haven't worked as a machinist for nearly 10 years.
Right after that I was given about the same weight in dulled drill bits to sharpen ... and one good drill bit to copy. Total instruction consisted of "Hold the drill bit about like this ... move it in an arc about like this. Make it look like the good one. There ya go. Have at it. Let me know when you think you've got the hang of it."
So practice, practice, practice. And let us know when you think you've got the hang of it. ;-)
Bill
BTW, to make a flat-bottomed hole similar to one made by a Forstner bit but without the dimple in the bottom, startb with two drill bits the same size. Leave one as-is and grind ALL the cone part off the other one then grind the cutting lips back to get rid of the middle wedge and then grind a back relief behind the cutting lips. Set your drill press to make a hole to the finished depth with a regular drill but leave maybe
1/32 or 1/16 of material in the bottom of the hole. The resulting hole will have straight sides tapering to a point in the middle.
We are going to cut off the tapered part (only) wqith the flat-bottom drill.
Now change to the flat-bottom bit and reset the drill press to the FULL depth. With the press off, Lower the flat-bottom drill bit into the hole to re-locate it. Then turn the drill press on to the same speed as foir the first bit and finish the hole.
You can pull the same stunt with a tap to tap all the way to the bottom of a hole. Just keep in mind that when the tap hits bottom it's time to stop turning it unless you get some sort of perverse kick out of digging broken taps out of mangled holes. To each his own, I suppose. :-)
Each trade has its tricks. I've been a machinist. Now I'm learning woodworking.
My first job involved drilling little holes into stainless steel. The drill didn't stay sharp very long, so my first skill was to learn to sharpen them on a grinder, getting all those little undercuts just right. Ah, but that was 35 years since I last tried. How does the machine do it; I thought it was just a simple grinding wheel, but there must be more to it than that.
So buy some drill bits. They're not expensive, even for decent ones. If you're drilling something hard, then a set of real M42 cobalt bits is pricey but wonderful. NB - these are silver, not just a blue coating (those are worthless).
My experience: It was supposed to work except that they mis-moulded a chuck component making it useless. UK service backup was negligible -- maybe the US is better.
and you're working with bits of 1/4" and over.
OTOH, I don't often break 1/4" and I don't even wear them out that fast. The ones I go through are 3mm - 5mm that I've snapped in half. Sharpening those is from hard to impossible (if there's no length left).
Huh! I sharpen drill bits on my grinder too. Sometimes I get a good cutting bit, other times I get a good scoutmaster's fire starter or a great oval-cutter! This just may help with a little of that trial and error business I'm so famous for. I'm gonna put this up over my drill press for next time I need it. Now if I can only figger how to get that danged point to CENTER :-)!
Thanks for the explanation, I'll try it by hand this weekend.
So what is the DD and the grinder jig doing? Do they hold the bit at a compound angle or is it more complicated? The grinder jig doesn't appear to be doing more than that.
work on one side at a time, obviously the same hand position on each. when done the geometry on one side is the same as the other. When looking at the very end you should see a straight line, the "peak" should divide the geometry exactly, meaning both sides are the same. It needs the angle measured co-axial from the peak through to the cutting edge, what 118 for std material, and also some backard clearance, what 9 degrees. In practice for most wood, if it looks good, and equal, alls well. The cutting lip should be sharp along its entire path while spinning. Often easier by hand. Machinery's Handbook tells you how to make the tooling after doing the calculations for actually making all the geometry correct for something so simple.
start with the cutting lip, and sort of spin and up-shove if using a g-wheel. Its a minor movement. Google.. Actually I don't even know the right procedure. I use anything handy- like a ut-off wheel on a dremel. The geometry is gonna cut, or it ain't, precision ain't important for most. Its freakin incredidble the physics and math that make it what it is to be what it is though, cuting tools of any type.
I guess the point is, you can't use the drill press b/c of the stationary stone, or whatever ,would need to cam in and out while following the flute while spinning to sharpen. If you look a the construction of bit stock, though, there is actually a land on the outer edge , so the outside perimeter has clearance too.
Reading the DD manual helped out with understanding what it is doing. The bit needs to be aligned in the 'chuck' The chuck has a cammed ring that pivots the bit as you rotate it to create the relief angle. Pretty neat idea.
formatting link
can only assume the grinding jig does something similar.
I'm gonna try Bill's method and see if I can get the hang of it before I consider a DD.
There is a old trick I always use.... when there is no gage available you can hold two HEX nuts side to side touching between your thumb and forefinger for the right angle.( hold up to light with drillbit to see.) airbrush
HomeOwnersHub website is not affiliated with any of the manufacturers or service providers discussed here.
All logos and trade names are the property of their respective owners.