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Building a better mousetrap: Drill bit sharpening jig

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strantor

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I'm needing a way to sharpen twist drills (lots of them) quickly and consistently. I won't be doing the work myself; I have an unskilled helper doing the chore. I've tried to teach him how to do it by hand but I suck at it myself so I can't hold it against him, but his results are less than stellar. I've looked into purchasing a jig/machine but there seems to be only two kinds: 1. Cheap crap that doesn't work, and 2. Really expensive production-oriented fixtures that have more axes than a CNC robot and more adjustments than two lathes together. They also mostly use a collet system so I would need a drawer of doodads, one for each size of bit I would conceivably want to sharpen. I don't like my options. I want something of acceptable quality (or at least acceptable results) and simple enough that a Liberal Arts major can use it. Necessity is the mother of hairbrained ideas and ultimate folly. Here's what I'm thinking...

(By the way, I'm posting this for peer review. Any and all criticism is welcome. Shoot holes in it, don't hold back. I can't find examples of anything close to what I'm about to describe so that means it's either a horrible idea or revolutionary. Most likely horrible. But at the same time, the pictures are just conceptual; only enough detail convey the point. the end result wouldn't look anything like this.)

I drew inspiration for this from knife sharpening jigs such as this:



The stone is held at the end of a long rod which pivots about (and slides through) a fulcrum of adjustable height. The long distance between the knife's edge and the fulcrum point allows the setting of precise angles with relatively crude hardware.

My jig is the same concept but in reverse. The "stone" (grinding belt) is held stationary and "knife" (drill bit) is mounted on a mobile rod. The slot plates are interchangeable and with the plates shown, should produce general purpose 118deg 4-facet bits.

1.PNG

The image above depicts the jig fitted with a 1/2" 4-facet drill bit, grinding the relief edge.
The image below depicts the jig fitted with the same bit, but grinding the cutting edge.

2.PNG

Below is a top-down view from above the grinding belt. The drill bit is held in a cordless drill chuck which is mounted on the end of the paddle pole.
The belt is mounted to the plate behind, at an angle of 118 deg. This angle is adjustable. The belt assembly is mounted to its backing plate with linear slides, so it can be moved side-to-side for even belt wear.

3.PNG

The sequence of operations would be as follows:
[with belt off]
1. Loosen the locking collar and place paddle pole into slot plates A and B (cutting edge grinding position)
2. Insert bit to be sharpened in paddle pole chuck, with cutting edge 90deg to belt.
3. Slide paddle pole forward until bit touches grinding belt, slide locking collar forward until it touches slot plate A.
4. Back locking collar off [some small distance*] from slot plate A and tighten.
* this small distance sets the amount of material to be removed. it will depend on the size of the drill and condition. If only a touch-up resharpening is desired, then maybe use a few thousandths of shim stock to set the depth.
5. Back paddle pole away from belt, energize belt.
6. Slide paddle pole gently in towards belt, and continue to apply gentle pressure until locking ring bottoms out against slot plate A and the belt stops cutting.
7. withdraw paddle pole away from belt, carefully remove paddle pole from slots, and without adjusting the chuck or locking ring, flip it over and put it back in the slots.
8. Feed paddle pole forward, gently grind 2nd cutting edge until locking ring bottoms out and belt stops cutting.
9. Withdraw from cut, remove paddle pole, place in slot plates A and C (Relief grinding position). loosen locking collar.
10. Paying close attention to cutting edge thickness, feed paddle pole into grinding belt until desired cutting edge thickness is achieved.
11. Set locking collar up against Slot plate A and tighten.
12. withdraw paddle pole away from belt, carefully remove paddle pole from slots, and without adjusting the chuck or locking ring, flip it over and put it back in the relief grinding slots.
13. Feed paddle pole forward, gently grind 2nd relief edge until locking ring bottoms out and belt stops cutting.


So, by utilizing the locking collar to feed forward to precisely the same distance on both sides, this should ensure precisely the same length of cutting edge on both sides, if my logic is correct. A perfectly symmetrical grind at precise angles. And with taking most of the "art" out of the task, maybe it now makes sense to sharpen smaller drills rather than replace.

The slot plates B and C are drawn appropriately for a 1/2" drill bit, but would be made to extend in both directions (up & down) with multiple stops within the slots, to achieve a variety of cutting edge & relief angles for different sized bits (and those stops could be marked in drill bit sizes for simplicity, ex: "use this position for 5/32 & 4mm bits")

Ok, take your shots. Why won't this work?
 
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T Bredehoft

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Maybe I missed it, but what provision is there for keeping the cutting edges the same length?
 

Bob Korves

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I think you are over thinking this, but of course, that is what we do as Hobby Machinists, and are proud of it!

Get yourself a sharpening jig and a bench grinder, and learn how to use it. This type:
1547223780626.png
They are quite inexpensive new, and can often be found dirt cheap, lightly used by people who did not read the instructions and think beyond them.

Has been sold by many companies under different brand names, and it works just fine after you understand how it works, including beyond the dumbed down instructions that come with it. You seem to understand the concept, and have skills good enough to post a very nice graphic post of what you have in mind. The jig above will do what you want, with a whole lot less investment in time and effort. It is designed to do what you are trying to do in your post, and it gives nice results -- if you are smarter than it is... It also has adjustments for several drill point angles.

I have ground several hundred drills in this type of jig before buying a Drill Doctor, which also works very well after you understand how it works and how to get there. They all turn out fine once you understand the setups and adjustments and know what you are looking for with various drilling operations.

Edit: By the way, the setup in the photo above is wrong, WAY too much overhang of the drill beyond the end of the holder...
 
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Liljoebrshooter

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Why not try a drill doctor? I don't have one but have heard they work pretty good.
 

Latinrascalrg1

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My first thoughts on your design were as follows.....Why does it need to be so big, are you sharpening Industrial Giant sized drill bits?
By trying to simplify it in the manner you have outlined with the plates and multiple positions, I think you will end up with an over complicated settup (at least not something a Lib Arts major wont have trouble with, lol).

Wouldnt a few "protractors" somehow attached to a few adjustable "Joints/Knuckles/shaft assemblies" be much more effective without the need to take up half of your floor space?

Edit: lol i started typing when there where no replies and by the time i finished i I was beat to the punch....I really Suck at typing, lol
 

strantor

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Maybe I missed it, but what provision is there for keeping the cutting edges the same length?
When you feed in on the first side until the locking collar bottoms out, and then you flip it over and again feed it in until the locking collar bottoms out, that's where you get your symmetrical grinds. In (my) theory, anyway.
 

strantor

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Why not try a drill doctor? I don't have one but have heard they work pretty good.
I think you are over thinking this, but of course, that is what we do as Hobby Machinists, and are proud of it!

Get yourself a sharpening jig and a bench grinder, and learn how to use it. This type:
View attachment 284552
They are quite inexpensive new, and can often be found dirt cheap, lightly used by people who did not read the instructions and think beyond them.

Has been sold by many companies under different brand names, and it works just fine after you understand how it works, including beyond the dumbed down instructions that come with it. You seem to understand the concept, and have skills good enough to post a very nice graphic post of what you have in mind. The jig above will do what you want, with a whole lot less investment in time and effort. It is designed to do what you are trying to do in your post, and it gives nice results -- if you are smarter than it is... It also has adjustments for several drill point angles.

I have ground several hundred drills in this type of jig before buying a Drill Doctor, which also works very well after you understand how it works and how to get there. They all turn out fine once you understand the setups and adjustments and know what you are looking for with various drilling operations.
I've spent an appreciable amount of time reading & watching reviews for Drill Doctor and the inexpensive sharpening jigs. I have no doubt that I could make them work with enough practice and figuring out the finer points of how they work. But I don't intend to do any of this myself. I've already wasted enough time teaching myself (with marginal success), and then my apprentice (unsuccessfully), how drill bits work, the geometry behind them, and how they should be sharpened. This is 50% personal and 50% business (I own a small business and it isn't a machine shop but we do use drills) so I can't treat it the same way I treat my pet projects. It has to make sense money-wise. I want something I can hand off to someone else, who doesn't have the same technical background as I do, and have it "just work" (idiot proof). If I can't have that, then I need to just move on. Maybe send the bits off for sharpening. Or forget about them, hang on to them for the next 35 years until I retire.

I don't even intend to build this jig myself. If I can believe in it enough to go forward, I'll model some patterns and have my apprentice cut out his own sharpening jig and assemble it, probably out of plywood.

Edit: By the way, the setup in the photo above is wrong, WAY too much overhang of the drill beyond the end of the holder...
Point taken. I'll address that before I make anything. Maybe put a V-plate up by the belt as the final resting surface for the end of the bit.
 

strantor

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My first thoughts on your design were as follows.....Why does it need to be so big, are you sharpening Industrial Giant sized drill bits?
By trying to simplify it in the manner you have outlined with the plates and multiple positions, I think you will end up with an over complicated settup (at least not something a Lib Arts major wont have trouble with, lol).

Wouldnt a few "protractors" somehow attached to a few adjustable "Joints/Knuckles/shaft assemblies" be much more effective without the need to take up half of your floor space?

Edit: lol i started typing when there where no replies and by the time i finished i I was beat to the punch....I really Suck at typing, lol
It doesn't need to be big, it's just that... ok, so the angle of the drill, the angle of the sanding belt, and their relation to the floor form a triangle. The more distance there is between the 3 points of the triangle, the more accurate the angle can be, utilizing crude materials and construction methods. Also, it minimizes error in setup and use. This is probably going to be made out of plywood and built by my apprentice. I can't justify spending any time on the clock machining parts for it. No machining, quick & dirty. That's why it's big. If it works as I hope, and I find there to be any market for it than anyone would be interested in purchasing something along these lines, I could make machined versions much smaller.
 

Bob Korves

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Point taken. I'll address that before I make anything. Maybe put a V-plate up by the belt as the final resting surface for the end of the bit.
On that 'specific' drill grinding jig, the overhang should be about half the drill diameter beyond the "tooth" that engages the flute of the drill, for a 'standard' 118 degree drill, so the drill has the correct clock orientation to the grinding wheel for making a proper grind. However, different point angles, different twist rates of the drill, and what the drill is intended to be used for, all come into play and require changed settings for best results.
 

Bob Korves

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There are at least dozens, if not hundreds of differently designed drill jigs available on the new and used market, from under $5 to thousands of dollars. They all work if used properly, some better and more quickly and easier than others. Drills are used in many industries and in many home shops, so there is a huge market, but it is already pretty saturated with products that do the job if the operator does his job correctly. Drills can also be ground to a proper point without any jig at all, just eyes, brain, tool rest, and bench grinder. It is done all the time, some far better than others. I grind all my drills 3/4" and above by hands and eyes to a good result, checking them with a drill gauge. Drill bit grinding tooling has been studied, better mouse trapped and improved, and new products put on the market for well over a hundred years now. The market is mature, and may well be considered saturated. Please keep us informed with what you end up with. There is always room for a better product at the right price.
 

strantor

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different point angles, different twist rates of the drill, and what the drill is intended to be used for, all come into play and require changed settings for best results.
This is where all the knobs and axes and adjustments of the commercial sharpeners come into play. I don't want all of that confusion in my design. I can teach my guy to recognize standard jobber bits (95% of what's in my bum bit bucket) and "anything else." "Anything else," I can sharpen myself.
 

strantor

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There are at least dozens, if not hundreds of differently designed drill jigs available on the new and used market, from under $5 to thousands of dollars. They all work if used properly, some better and more quickly and easier than others. Drills are used in many industries and in many home shops, so there is a huge market, but it is already pretty saturated with products that do the job if the operator does his job correctly. Drills can also be ground to a proper point without any jig at all, just eyes, brain, tool rest, and bench grinder. It is done all the time, some far better than others. I grind all my drills 3/4" and above by hands and eyes to a good result, checking them with a drill gauge. Drill bit grinding tooling has been studied, better mouse trapped and improved, and new products put on the market for well over a hundred years now. The market is mature, and may well be considered saturated. Please keep us informed with what you end up with. There is always room for a better product at the right price.
Perhaps I'm putting the cart before the horse. Perhaps my first step should have been to ask around on this forum about commercially available drill sharpening solutions that fit my requirements. If what I want is already for sale, I would be more than happy to pay for it. Here's what I need (in order of importance):
1. operable out of the box by someone who knows little to nothing about drill bit geometry and has no technical intuition (but can follow simple instructions).
2. Produces repeatable and accurate results
3. Fast one-step or no-step setup change, going from large bits to small bits and back again.
4. Extremely simple interface, very few adjustments. Even if only suitable for sharpening general purpose bits; that's fine.
5. Decent quality, American made preferably
 

benmychree

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Just buy the damn Drill Doctor already! I had one at my shop, and nearly anyone can learn to use one quickly and accurately they have very few adjustments necessary, mostly the one for spiral angle of the drill flutes; if you are using ordinary drills, likely no adjustment is necessary. I he one that I had also did split points, which makes drilling more accurate and faster with much less feed pressure being necessary.
 

strantor

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Just buy the damn Drill Doctor already! I had one at my shop, and nearly anyone can learn to use one quickly and accurately they have very few adjustments necessary, mostly the one for spiral angle of the drill flutes; if you are using ordinary drills, likely no adjustment is necessary. I he one that I had also did split points, which makes drilling more accurate and faster with much less feed pressure being necessary.
The reviews I've read are very hit-or-miss. I don't if it's QC or model-dependent, or what. People either love them or hate them. I think it comes down to whether the Dr. "speaks" to you or not. Plenty of mechanically intuitive people can't make the contraption work. I've not tried it myself but maybe I will. It costs less than the week of minimum wage I'd have to pay for my own contraption to be built, so probably worth the experiment. What model do you recommend? Also, is there any way to dress the grinding wheel or does it have to be replaced? I'm talking about probably 50lbs of bits here, of all sizes.
 

mikey

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I own a Drill Doctor. It works well for me and if I can use it then pretty much anyone can. The how-to is on video so I don't see how you're going to mess it up. It uses replaceable diamond wheels to sharpen the drill with so you will need to change it when it dulls. It tends to overheat the drill when it dulls so you'll know. I changed my wheel once after about 20 years of hobby shop use.

You put a lot of thought into your design but I would just buy a DD and move on to more important things.
 

ddickey

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I have heard people having good luck with their Drill Doc. Not me.
 

bhigdog

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The only thing wrong with a DD is it's too light. If it was heavier it would make a good boat anchor...................Bob
 

cathead

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Long ago, way back in olden days in a time before all these contraptions and doohickeys existed, machinists simply used a grinding
wheel to sharpen their drills and it wasn't a problem. Maybe try learning a new skill and try off hand sharpening. It's really not that
difficult to do. I use a disc sander for sharpening but a grinding wheel works too.
 

strantor

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Long ago, way back in olden days in a time before all these contraptions and doohickeys existed, machinists simply used a grinding
wheel to sharpen their drills and it wasn't a problem. Maybe try learning a new skill and try off hand sharpening. It's really not that
difficult to do. I use a disc sander for sharpening but a grinding wheel works too.
Yeah I get it. I did that. I can hand sharpen drill bits. I'm not great at it and I'm not fast, but I can do it. With more practice I could get better and faster. But I have a business to run, and no matter how fast or good I get, I won't be able to justify my time sharpening drill bits. I could forward your advice to my helper and make it a job requirement to teach himself to sharpen bits, but even at minimum wage, I can think of better uses of his time. He's burned up two days already "learning" how deform HSS with a grinder. At the end of the day, all I need is bits my bits sharp. Well I need more than that, but you know what I mean. I'm responsible for making that happen indirectly by whatever means.
 

madmodifier

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So much dislike of the drill doctor. I have a 750x and I think it does a pretty good job. It will not however fix the crappy steel in import drill bits. As long as you are working on under .750 drills they are an OK way to go imo.
 

strantor

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So much dislike of the drill doctor.
See what I mean?
The reviews I've read are very hit-or-miss.... People either love them or hate them.
This is what I was talking about...

:)
Drill Doctor... works very well after you understand how it works
:)
Why not try a drill doctor? I don't have one but have heard they work pretty good.
:(
I'll pay you to take my Drill Doctor.
:)
Just buy the damn Drill Doctor already!
:)
I own a Drill Doctor. It works well for me
:(
I have heard people having good luck with their Drill Doc. Not me.
:(
The only thing wrong with a DD is it's too light. If it was heavier it would make a good boat anchor
 

Bob Korves

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It is not really so much that the DD is difficult to use, or that many operators have trouble with getting good results with it, or indeed with any other drill grinding machinery. It is about learning how a drill is made, in detail, learning about the geometry of a drill, in detail, learning how the machine they have in front of them does the work of grinding the drills, in detail, and also understanding, in detail, how changing one part of the setup changes some or all of the others. Then, going to work at learning how to deal with variations of various kinds of drills, in point angle, clearance and relief angles, flute helix angles, and web thickness. Beyond that, what alloy the drill is made of, and how it interacts with various work materials -- and the properties of those materials. It is really necessary to know that information -- and how it changes the way the drill cuts -- before you can apply a well thought out plan for what drills to purchase; making drills sharp again; maximizing production while making holes within tolerance for size and for surface finish (if required) -- at the highest possible cycle rate and with a near zero rejection rate. Some times it makes more sense to just use new drills until they get to a certain amount of wear and then just toss them.

Of course, I morphed on purpose into writing about how things work in large production plants rather than a small job shop, much less a hobby machinist shop. But really, that is who you are often in competition with if you are doing commercial work. You might be doing jobs with far less quantity for a local clientele, but working smart and efficiently, and having happy customers, is still what wins the game. One "OH ****" cancels out MANY "atta boy's" in business. You must be smart, skilled, involved, efficient, and a people person.

All that is why I am nearly always the only person in my shop, and is also why I only have to deal with myself...
 

strantor

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Some times it makes more sense to just use new drills until they get to a certain amount of wear and then just toss them.
That's what I've been doing all along, hence the bucket of reject bits. It's never been worth my time to sharpen them. I thought now that I have a helper, it would be worth his time (my money). So far it's not. There's only one person around to teach him, and that's me. If I stop my billable work to teach him, I'm losing more money than if I just did it myself (his pay plus my pay). And I can't even mentally write it off as an investment in training, because the tutoring he would get from me would be subpar. I've been leaving it up to him to learn on his own from YouTube but I don't think he has to intuition or maybe the experience to pick it up that way.

Everything you said after the "in detail" punctuations, has me thinking that maybe I need to just keep filling the bit bucket and revisit this later. Once my helper learns how to actually drill a hole, what bit to use, what speed to use, etc. then he'll be ready to learn to sharpen drills. This guy put my trailer's lug nuts on backwards. Me asking him to sharpen drills is like a chemist asking me to keep his lab stocked; I don't know what any chemicals are or how often they're used or anything.
 

mmcmdl

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I'm just not sure what to think of this ! :grin: ( other than I have a knife sharpener like that )
 

ddickey

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The big problem with a DD is the collet that holds the bit. As you tighten the collet the bit turns slightly. Very annoying.
 

coffmajt

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Have you looked at gadgetbuilder.com website = there you can find a four facet drill sharpener that will sharpen up to .5 inch diameter bits and is simple to use (not necessarily to make) Just more ideas to consider
 

P. Waller

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If you are going to go through the work of adding human figures to a rendering at the very least give them eyes.
Or at least title the thread "featureless humanoids using a tool" (-:
 

strantor

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If you are going to go through the work of adding human figures to a rendering at the very least give them eyes.
Or at least title the thread "featureless humanoids using a tool" (-:
It's sketchup. Each time you create a new model they drop this faceless creep "josh" into the center. My first step is usually to delete him but I decided to keep him around for scale this time.
 
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