Do you guys sharpen your twist drills?

Patrice Lemée

Patrice Lemée

Joined
Aug 13, 2002
Messages
5,703
I bought a Drill Doctor 750X some years ago. Never worked any good. Did some research to try and troubleshoot it but still doesn't work. :(

I thought I'd try to hand sharpen. I don't have anyone close enough to show me so I downloaded a bunch of info and videos from the net and gave it a try. Only thing I do is shorten drills :grumpy:, can't get the hang of it. :( I can grind an ok knife, you'd think I could grind a twist drill.:grumpy:

As you can see, this is more a post about me whining :grumpy: :o but if any of you guys do your own sharpening and want to share a tip or two, that'd be great.
 
Pat-


I wonder what's up with your Drill Dr... my Dad has one and it works really well. But it's at his shop. ;)


A close inspection of my Nathan Carothers disc grinder pics will reveal a twist drill grinding gauge (118 degree) next to one of the discs. It was our first project in the machine shop program. There's another one on that bench for 135 degree bits.

I sharpen bits all the time. Once you get a feel for it, it's very quick and easy. The belt grinder works great too, as does a decent quality bench grinder... I just like the discs for this. I don't use the guages much anymore. Only if I'm having a hard time getting one to look right with my micrometer eyeball. ;)

I have managed to sharpen 1/16" bits, but it's hard to get right, and at $1-2/bit, I just chuck them when they get dull. But around 1/8" and up is cake.

IMHO, the easiest way to learn is with big bits. At school they had us use a pretty large, oddball size, 'cuz a lot of the bits get toasted by kids with very short attention/patience... it was like 37/64 I think. The teacher got them really cheap at a surplus outfit.


I'm sure there'd be 100 guys lining up to tell me how wrong I do it, if they were to watch me, but I can take a bit that doesn't want to cut, hit it on the disc, and it will cut nice and clean with even chips flowing off the flutes... so it works.

I saw a video a while back of a machine shop teacher showing his method, and it was exactly how I was taught. I'll see if I can find it.
 
This is what I was thinking of... there are two parts. I think part 1 is important because he points out some typical problems in poorly sharpened bits, and explains using a grinding/sharpening gauge.

[video=youtube;QbRPPxyw1hw]https://www.youtube.com/watch?v=QbRPPxyw1hw[/video]
 
I freehand bit on my 8" wheel with a 120 or 220 belt depending on how dull. I have had pretty good results, just takes practice. Slow speed lots of water. I usually dunk the belt in water to help with overheating the bit.
 
I just bought a drill doctor 750x and took a new 135 degree bit and ground it 118 then back to 135 with relative ease. If you are having issues don't give up yet. Watch the DVD, read the manual and call tech support. There are many many good videos of drill sharpening on bench grinders on YouTube. You will need a gauge to help you and they are 118. I have seen 1 135 gauge. Or without the gauge you can test drill holes, look for equal curl production and then measure hole for diameter.

What issues are you having with the drill doctor?
 
Thanks, Nick, that is a great video. I have a drill doctor. It came with a video. After watching the video, I found it easy to sharpen bits on it. I have more than paid for the drill doctor in saved bits. One problem with the drill doctor I have is it takes a lot of time to do 1/2" and larger bits. I think I will watch the video again and see what I can do freehand.
 
I'm dong it by hand and was thinking about getting a drill dr.

:)



There are some videos in the youtube sticky also.

I was shown in person, it's a pretty complex movement.

I'm not that consistent though
 
I do it by hand.

There is more than one way to do it. In fact there is more than one way a production drill is ground, if you look at the web of a really good spot drill it has a bit of twist to it whereas a regular drill is straight.

It's quite simple once you think about it. All you're doing is cutting a cone that is angled back a little bit from the cutting edge.

Set the edge so it is aligned with your grinding wheel. Rotate the drill around its axis and as you're spinning it around you're pushing the bottom down (angling the tip up) to cut the clearance you need behind the edge, so it's a twisting rolling motion. If you started with the edge perpendicular to the wheel (or actually just a hair above center) and cut clearance behind the edge as you go, it will work.

A drill that you have hand sharpened you can control that clearance angle and make it less grabby making it better for your use than a new drill which has enough clearance behind the cutting edge for quite a bit more feed per rotation than you will want hand feeding in knife steel.

Edit to add: this is a lot easier than straight grind lines and even bevels. If you can grind a knife blade you can grind a drill.
 
I love my Drill Doctor. Chance are if it is not working for you then you might be chucking up the drill in the wrong position. I did it a couple of times over the years not paying attention and it does suck if that is done :)

It works great otherwise
 
I sharpen number drill bits using a separating disc in a flex-shaft machine.
On the tiny ones, I just use a fine diamond file.
 
I've been sharpening them lately (1/8 and up), freehand, as I learned online. I use the bench grinder with the fine(r) wheel. I wish I had a pink wheel....or a blue one. Those are supposed the be the cat's meow for keeping heat at a minimum while grinding, from what I hear.
 
Trust me, you ever mess up a 1/2" or larger premium drill bit, you won't stop trying to sharpen it until you either figure it out, or there's nothing left. 1/8" and below like Nick said, I just buy new ones. My local supply house they cost like $1 a piece, buy a couple dozen at a time. I do occasionally sharpen a 1/8 bit but half the time they shatter beyond repair.
 
I free handed approximately 200 drill bits per day in one job I had in a manufacturing facility. I had a machine to use but it was slower than by hand.
 
I've been sharpening by hand since I learned how in high school shop class 30+ years ago. I don't use a gage too often but on smaller drills I will sometimes check them under a magnifier. If the grind is not equal on each side, the drill can walk in the hole and exit in a different location or even snap if the material is thick enough. I also fine tune drills for different materials. For example, I often use a diamond file to put flats on the cutting face for drilling in brass. I've never used a Drill Dr. but it seems most are pretty happy with them.

Bob
 
Patrice, I sharpened drill bit by hand for 30 years before I ever saw a drill doctor. The first time I tried to use a drill doctor the drill bit came out looking like crap, but sense I all ready knew how to sharpen a drill bit I could see what was wrong. The two little spring steel flute guides held the drill bit out of phase with the cam if you let it find it's own center. I corrected this by forcing the drill bit clockwise as I tightened the collet and could grind a good drill bit.

I ground about a dozen bits to make sure it was repeatable and haven't touched a drill doctor sense.

Now as far as sharpening drill bits by hand, remember there is a flat across the point of the drill bit. You cant get this by a rotating movement only. You need to make a compound movement, sweep as you rotate. I don't know how else to describe it, it just takes a lot of practice.
 
First of all thanks for the links and tips guys. Those videos are very clear and easy to understand Nick. :thumbup: If I can't do it with this, might as well give up. I'll give it another try. I need to buy or make a drill gauge. Been using a protractor and it doesn’t have markings for the length of the lip.

Using some cheap drills I have lying around to practice on is a good idea. Been practicing on the actual drills I use and the stress of not wanting to mess it up doesn’t help.

Note: After looking at the videos a few times, I think I was not putting enough positive rake on the primary clearance. First thing to try and improve.

As far as the Drill Doctor, I did look at the video and read the instructions a bunch of times but something is not working and as it was suggested, it must be with the way the drill is indexed. Looks like I am the only one having issues though so it must be operator error. :o But for the life of me I can't figure out what I'm doing wrong. From reading many threads about it on the web, it's a “works great” or “POS” kind of thing. Guess I am on the POS side. I'll try indexing the drill by hand but hopefully like Nathan said, I'll be able to master grinding by hand instead.

One of the things I AM doing wrong is using the 135 degree setting. How is it that I thought this was the right angle for steel?:confused::confused::o
 
I started working in my dad's shop when I was 16. I quickly learned to sharpen bits using our crude bench grinder. We were drilling conventional mild steel so all it took was angling the edge of the bit back enough to create a cutting edge ("positive rake" is what he calls it in the video). This was very intuitive to a 16 year old, I figured out what I thought needed to be done, I did it and it worked well.
 
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I have a drill doctor 750 and it works great. My friend has one and he said it would never sharpen a bit. I took a handful of his dull bits and sharpened all of them in ten minutes with his "useless" drill doc. He was clearly doing something wrong, because it worked just fine for me. He said he tried it again after I left and still couldn't get it to work right. I observed him using it on my next visit and now he sharpens his bits like a pro. His biggest problems were:
1) He was pushing in hard all the time as he was sharpening the bit. I showed him how to follow the cam on the clamp and told him to try and visualize the bit face as it cut against the internal wheel. I also told him to let the tool do the work and be more gentle.
2) He was going round and round many times. I showed him how to make a first pass on each face, and then to make a second pass with a lighter pressure to clean up the first cut.

See if you can get someone who is familiar with using a Drill Doctor to demonstrate sharpening it on your unit for you. The key is to get the drill clamped right, and only apply pressure against the grinding wheel as the bit rotates off the cam on the clamp. You can hear when it is cutting a face and when it is rotating to the other flute. Don't grip the bit, but only grip the clamp knob assembly. It helps to know how the machine works. The clamp will change angle and alignment as the cam moves the bit into position on the wheel. Don't try to force it hard or you will be fighting what the assembly is trying to do.

That said, you don't seem to be a cafouiller-touche' godiche. Your machine may have something wrong with it. The cutting wheel may not be properly attached, or may be worn out if it was purchased used.
 
Patrice, I would recommend getting some drill rod and chuck that up and use the drill doctor. You won't be able to chuck it up wrong since it is a perfect cylinder. You will have to readjust and extend the rod out a bit but you would end up making a useable bit out of a blank. If you don't have a blank, then take a bit and use the other end as a blank. Prior to readjusting and extending the tip, you would be able to see how the dd cuts the material and how the bit is oriented in the chuck. This is how a pre made bit should be oriented in the chuck. I think that if you have too much bit extended by having the MTO, material take off setting, set too far back (away from the drill tip), problems could arise.

You could take off the grinding wheel and reverse it and start with a fresh side to take that variable out of the picture.
 
I will try those tips Stacy. Looks like I am doing it pretty much like this but maybe not with a soft enough touch. PS: I am no idea what a "cafouiller-touche' godiche" is.:o

Doc, I.ll give that a try also. No drillrod but I do have enough old drills lying around. One of the first thing I did was to reverse the wheel like you suggested but results were the same.

Thanks again for your help guys.
 
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