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Well, this dosen't look safe!
- Thread starter Finster
- Start date
- Joined
- Nov 15, 2016
- Messages
- 943
O.H.S.
NOTHING IS SAFE!!!
NOTHING IS SAFE!!!
I wonder if the 'no side loading' is just a disclaimer by the grinding wheel manufacturers anyway....
I have several cup type wheels (clearly made for side loading only) and I can't see any difference in manufacture or construction of these at all, except that the mounting portion of them is significantly THINNER than most of my grinding wheels.
I have also seen wheels explode, and have a friend who is permanently disabled as a result of getting hit in the forehead by a large fragment. In every case they were either newly mounted wheels with a fault or a 'crash' where something hit the wheel that was not intended to. In one case a piece of metal getting jammed into the grinding rest gap to the wheel, stopping the wheel in an instant and throwing a piece out.
I still grind things on the side of the wheel regularly, with normal grinding pressure. On both cup wheels and parallel wheels. Have been doing so for around 55 years....
The drill bit sharpener in question is indeed a useful tool I have had from new around 45 years ago. It's pretty well worn out now. The amount of pressure or force on the wheel is near nothing.
Jamming something into the wheel - face or side - is asking for trouble, no matter what kind of wheel.
Just my 2 cents worth....
I have several cup type wheels (clearly made for side loading only) and I can't see any difference in manufacture or construction of these at all, except that the mounting portion of them is significantly THINNER than most of my grinding wheels.
I have also seen wheels explode, and have a friend who is permanently disabled as a result of getting hit in the forehead by a large fragment. In every case they were either newly mounted wheels with a fault or a 'crash' where something hit the wheel that was not intended to. In one case a piece of metal getting jammed into the grinding rest gap to the wheel, stopping the wheel in an instant and throwing a piece out.
I still grind things on the side of the wheel regularly, with normal grinding pressure. On both cup wheels and parallel wheels. Have been doing so for around 55 years....
The drill bit sharpener in question is indeed a useful tool I have had from new around 45 years ago. It's pretty well worn out now. The amount of pressure or force on the wheel is near nothing.
Jamming something into the wheel - face or side - is asking for trouble, no matter what kind of wheel.
Just my 2 cents worth....
- Joined
- Jul 2, 2014
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- 7,571
A cup wheel on a bench grinder will also either leave the wheel sticking out beyond the safety guard, or require removing the entire guard or the side cover of the guard. It would of course be possible to make a new guard for a cup wheel, but how many would actually do so, and with an adequate design, and well built? Then again, many machinists use cup wheels on tool grinders and surface grinders without any guards at all. Many thousands of home shop guys have ground drills on the side of the wheel with these grinding jigs for at least five decades that I know of, and I have not heard war stories of problems with doing so. In the 33 messages so far on this thread, no one has posted a first person account of seeing a wheel explode from using this tool on the side of a bench grinder wheel. Both Joe in Oz, and I (40 plus years each), and countless others have used them in the same way they are configured on the manufacturer's packaging, without any issues. Let's spend more time championing safety where there are known, documented, and recurring safety problems that cause injuries. Machining and metal working have lots of inherent dangers that are simply part of the processes, and we ignore them at our peril. There are plenty of common injuries occurring daily for us to get the word out on...
- Joined
- Jan 28, 2016
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- 253
That's how I've always done it. I have a drill doctor coming in the mail now though.
- Joined
- Aug 4, 2015
- Messages
- 291
OK, I am not gonna get into the safety discussion.
Instead I will talk about sharpening drill bits and what you can and can't get away with.
There are 4 basic methods of sharpening twist drills, and each has negatives, I will only discuss the bad here because the good part is you end up with a sharp drill bit if the stars align and you do in either right or as accurate as the method allows.
Now bear in mind that a properly sharpened drill bit will have two cutting faces, of equal angle, size and shape. They will have a specific amount of rake to keep just the right amount of the face against to work so it will regulate the speed of the cut and not just dig in as a chisel would.
First method is hand sharpening.
This by far is he worst way of sharpening a drill bit. Only pure luck and planet alignment will get a drill bit properly sharpened with this method.
There are TOO MANY angles that all have to be controlled, depths that have to be matched and the list goes on.
Figure that a good professionally sharpened twist drill will be accurate flute to flute and cutting face to cutting face to the point that an optical comparator would be needed to see the error in the bit. Firing up the grinder and free handing the bit until the burs and chips are gone from trying to force the wrong size bit at too fast a speed through metal that is almost as hard as the twist drill is NOT EVER going to be 100% right.
Second is the low grade stuff like pictured. These are at least an attempt for consistency, but due to quality still fall short and will also generate bits that want to drill triangle shaped holes.
Then you have the drill doctors.
These are loosely based on the other product the company makes, being DAREX, which make very high quality and expensive tool bit sharpeners.
These are better than the first two methods but fall short in the fact they use a very small abrasive drum to sharpen with. The small diameter means that a surface that should technically be flat have a very small radius that is imposed into the bit as it cuts it. This coupled with plastic parts that flex which leads to errors make them much better but still not great.
Lastly is the high end high buck stuff. Now we are talking air bearings, DAREX units similar stuff.
The biggest drawback to a DAREX is it's 3200 bucks. But they can sharpen not only the tips of drill bits accurately but also the flutes. Try freehanding that.
Air bearing end mill fixtures fit into this category as well. These can be used with a quality bench grinder and proper abrasive wheels to sharpen any round cutting bit. They can also be used to create odd ball bits from drill rod blanks if you feel the need to do so. Ultimately price again keeps these out of the hands of most hobbyists.
Any of them will work to some degree. And I know I will get flamed by the old guys that have been free handing for years with claims that their bits cut just fine. But I would still put my air bearing sharpener up against their free hand work any day.
Instead I will talk about sharpening drill bits and what you can and can't get away with.
There are 4 basic methods of sharpening twist drills, and each has negatives, I will only discuss the bad here because the good part is you end up with a sharp drill bit if the stars align and you do in either right or as accurate as the method allows.
Now bear in mind that a properly sharpened drill bit will have two cutting faces, of equal angle, size and shape. They will have a specific amount of rake to keep just the right amount of the face against to work so it will regulate the speed of the cut and not just dig in as a chisel would.
First method is hand sharpening.
This by far is he worst way of sharpening a drill bit. Only pure luck and planet alignment will get a drill bit properly sharpened with this method.
There are TOO MANY angles that all have to be controlled, depths that have to be matched and the list goes on.
Figure that a good professionally sharpened twist drill will be accurate flute to flute and cutting face to cutting face to the point that an optical comparator would be needed to see the error in the bit. Firing up the grinder and free handing the bit until the burs and chips are gone from trying to force the wrong size bit at too fast a speed through metal that is almost as hard as the twist drill is NOT EVER going to be 100% right.
Second is the low grade stuff like pictured. These are at least an attempt for consistency, but due to quality still fall short and will also generate bits that want to drill triangle shaped holes.
Then you have the drill doctors.
These are loosely based on the other product the company makes, being DAREX, which make very high quality and expensive tool bit sharpeners.
These are better than the first two methods but fall short in the fact they use a very small abrasive drum to sharpen with. The small diameter means that a surface that should technically be flat have a very small radius that is imposed into the bit as it cuts it. This coupled with plastic parts that flex which leads to errors make them much better but still not great.
Lastly is the high end high buck stuff. Now we are talking air bearings, DAREX units similar stuff.
The biggest drawback to a DAREX is it's 3200 bucks. But they can sharpen not only the tips of drill bits accurately but also the flutes. Try freehanding that.
Air bearing end mill fixtures fit into this category as well. These can be used with a quality bench grinder and proper abrasive wheels to sharpen any round cutting bit. They can also be used to create odd ball bits from drill rod blanks if you feel the need to do so. Ultimately price again keeps these out of the hands of most hobbyists.
Any of them will work to some degree. And I know I will get flamed by the old guys that have been free handing for years with claims that their bits cut just fine. But I would still put my air bearing sharpener up against their free hand work any day.
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- Nov 15, 2016
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- 943
O.K. Keith you've made the point, none of the old guys can sharpen a drill bit like you can with your air bearing sharpener. The real point is that no human is capable of replicating the accuracey of a machine. That is why we humans build machines is it not, to actualy do a job better than we animals can physicly do? CNC is a stark reminder of just how inaccurate humans are.
Here is something to think about though, a bit that drills a good hole is something that most can learn to grind freehand by several different methods and having been taught by people who started their learning in the early 1900's I believe that the ability to recognise when a bit is not cutting right and the ability to quickly make it good is a valuable skill.
Staying in the real world I cannot remember ever needing to sharpen the flutes of a bit. I'm not so old I ever had to make a twisted bit from scratch.
We all love the brand new factory sharpened bit but that falls way short of the ideal. In the real world a bit that cuts clean and round and very close to the nominal size works just fine,(reamers were invented for proper round holes). Some of us still hand grind on the job because it expedites the job and also because all that time learning to do the job of sharpening drill bits was not wasted. As a 1st year apprentice I had to collect every bit not in use after Friday arvo smoko and inspect them, sharpen all that needed it and have a tradesman inspect my work. To this day I cannot put a bit back in a rack if I know it is defective. A quick lick,(only if nesacery), after use means it will at least be 'good enough' for the next guy who is in a hurry.
Just for the record I regulary go through all my bits and every now and then take any I think are sus to a friend with an expensive purpose built commercial grinder and beg ,(wheel),face time.
- Barry.
Here is something to think about though, a bit that drills a good hole is something that most can learn to grind freehand by several different methods and having been taught by people who started their learning in the early 1900's I believe that the ability to recognise when a bit is not cutting right and the ability to quickly make it good is a valuable skill.
Staying in the real world I cannot remember ever needing to sharpen the flutes of a bit. I'm not so old I ever had to make a twisted bit from scratch.
We all love the brand new factory sharpened bit but that falls way short of the ideal. In the real world a bit that cuts clean and round and very close to the nominal size works just fine,(reamers were invented for proper round holes). Some of us still hand grind on the job because it expedites the job and also because all that time learning to do the job of sharpening drill bits was not wasted. As a 1st year apprentice I had to collect every bit not in use after Friday arvo smoko and inspect them, sharpen all that needed it and have a tradesman inspect my work. To this day I cannot put a bit back in a rack if I know it is defective. A quick lick,(only if nesacery), after use means it will at least be 'good enough' for the next guy who is in a hurry.
Just for the record I regulary go through all my bits and every now and then take any I think are sus to a friend with an expensive purpose built commercial grinder and beg ,(wheel),face time.
- Barry.
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- Aug 4, 2015
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- 291
Yes that is all true. You can get it done free hand and it will work to some degree. The biggest issue with hand sharpening is the faces not being equal and one cutting harder than the other. That will bind a bit and break it quick. As far as sharpening flutes. No sharpening flutes is not common. One use for it is when you need a .485 bit and you only have a draw full of .500 bits. An air bearing fixture will allow you to reduce the diameter of the bit to what you need
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I know people who break drill bits on a regular basis, reground or new. These same people also have problems with burnt tips, chipped and wiped outer edges ect. This they do with a continual feed of new bits and their problems are to do with no lube when it is needed, wrong speed, using the bit as a punch,(huge axial force),and not having the work or drill secure. Hand drilling is particulary bad.
On the other hand I know people that very rarely break a bit, most of their bits just get worn out then get used as stub bits,
You have me envious now of your air bearing sharpner, I had not given thought to the number of times I have needed a particular size and for one reason or another have not had the exact size I've needed. 'Close enough' usually works but never feels good.
We use Imperial and metrickery here and between whole number, fractions, number and letter sizes and metrickery sizes which come in 0.1mm steps
just about all bases CAN be covered if you have time to obtain the size you need.
I'll still stick to a reamer when I want an accurate hole though.
The points summed up by Bob Korves pretty much says it all about equipment used by the average Joe though. Common sense liberally applied usually gets the job done and done well and that is where knowing how to use machinery in general comes into play. I sometimes hand grind on the side of a wheel, most times the face. Different techniques same result. A drill gauge I made in 1973 still helps with the edge length and watching the swarf lets me know how well the bit is cutting.
While I am well known for having serious tool envey issues I also have to deal with all the variables that makes life interesting and at the end of the day finding something that works and works well, safely for the individual is the most important thing.
On the other hand I know people that very rarely break a bit, most of their bits just get worn out then get used as stub bits,
You have me envious now of your air bearing sharpner, I had not given thought to the number of times I have needed a particular size and for one reason or another have not had the exact size I've needed. 'Close enough' usually works but never feels good.
We use Imperial and metrickery here and between whole number, fractions, number and letter sizes and metrickery sizes which come in 0.1mm steps
just about all bases CAN be covered if you have time to obtain the size you need.
I'll still stick to a reamer when I want an accurate hole though.
The points summed up by Bob Korves pretty much says it all about equipment used by the average Joe though. Common sense liberally applied usually gets the job done and done well and that is where knowing how to use machinery in general comes into play. I sometimes hand grind on the side of a wheel, most times the face. Different techniques same result. A drill gauge I made in 1973 still helps with the edge length and watching the swarf lets me know how well the bit is cutting.
While I am well known for having serious tool envey issues I also have to deal with all the variables that makes life interesting and at the end of the day finding something that works and works well, safely for the individual is the most important thing.
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- Jul 2, 2014
- Messages
- 7,571
Making a drill bit smaller diameter than original does not require an air bearing. It can be done on a spindexer on a surface grinder, or on a basic tool and cutter grinder, and perhaps on other setups as well, not quite as accurately, but then drills are not tools for producing precision holes. Regardless, removing the margins from drill lands will take away any real hope for smooth finished, accurate holes anyway. I think that is a great idea for a reduced custom sized diameter hole, but it is still a drill, which is a material remover, not a precision hole maker. Followed by an on size reamer, yes, at the custom size and a smooth and round hole. Then again, a reamer can do that without the custom size drill...
