The Shop > Tools
Bench Grinders & Lathe Tools.
Pete W.:
Hi there, again, all,
First of all, I apologise for starting a thread and then doing a disappearing act! Things cropped up!!
--- Quote from: DMIOM on June 09, 2017, 10:45:19 AM ---Pete,
I can't offer any definitive advice, but I have previously found the UK HSE's "Safety in the use of Abrasive Wheels" useful, you can buy the hardcopy, but it is also available as a free PDF download. I'd suggest you might have a look yourself; on a quick read the only pertinent reference I can spot is "....All organic bonded wheels for hand-held applications will bear a use-by date of three years from the date of manufacture....."
Dave
--- End quote ---
I confess that I hadn't been thinking of organic bonded wheels - in my experience, double-ended bench grinders have always been fitted with vitreous bonded wheels.
Am I right in thinking that organic bonded wheels are used when it's necessary to profile the wheel to grind some complex shape?
On an earlier thread, long, long ago, I got a hot (near incandescent) response when I broached the subject of 'to use or not to use' non-new wheels. Soon after I started this thread, Keith Rucker posted a video on his YouTube channel showing a table well covered with second-hand wheels that he had acquired as a job-lot. He said that he was going to keep some of the wheels for his own use but invited offers from viewers who might take the others off his hands (for a fair price). On page 5.17 of The Model Engineer's Handbook (third edition), Tubal Cain (i.e. the Brit, alias Tom Walshaw) writes 'the only safe speed for second-hand wheels of unknown provenance is zero.' I find that hard because I have, among my stash, a medium & fine pair of virgin vitreous bond wheels, a white saucer wheel and a white cylindrical cup wheel, any or all of which would enhance my tool-grinding capabilities. The provenance of the medium & fine pair is not unknown, I bought them several years ago, I've looked after them carefully, they are still in their original packing and they 'ring' healthily. The provenance of the two white wheels is more obscure - the saucer wheel also 'rings' healthily but the shape of the cylindrical cup wheel doesn't lend itself to the 'ring' test. Application of the 'precautionary principle' here might decouple authors (and forum posters) from litigation but it also promises to condemn a lot of potentially usable wheels to scrap (that can't be an environmental plus!!). I'll just add that, while going through my stash, I did find a nice new old stock fine green-grit wheel that failed the 'ring' test - closer examination revealed a Y-shaped crack and it fell into three pieces while being handled! I did scrap that one while weeping a little.
In addition to my original 7" Black & Decker double-ended grinder, I have a smaller single ended grinder. This has the wheel and rest on the left-hand end and is fitted to accept a flexible shaft on its right-hand end. I wondered about fitting the white cylindrical cup wheel to that machine but it would be turning the wheel the wrong way.
I recently made an impulse buy, a modern 150 mm double ended machine. It's rated at 370 Watts but with a 10 minutes ON, 15 minutes OFF duty cycle. The motor runs quietly enough but when I saw how the wheels turned, the expression that came to mind was 'swash plate'!! I've left it too long to ask the seller to accept a return and, besides, the purchase price was alleged to be reduced. In his book, Harold Hall describes mounting an entire double ended grinder on the bed of his lathe and using cross-slide and top-slide to true the grinder shaft ends while it revolved under its own power - I'll probably be trying that some time. The wheel mounting washers are pressings but look to be true enough.
Well, this has been a long post, and no photos!!!
Pete.:
It's the pressed steel side plates that cause the wobble. I turned some heavy duty ones for my grinder and the wheels run lovely and true. You only need do the back plate.
PekkaNF:
Safety is importat. I believe that information that answers on question "why not this way, and why this way" produces safer work habits than blaket "Don't do it" without any explanation.
If we just take the view that when something is dangerous, we better just stop convesation there is very little left in out hobby.
--- Quote from: gerritv on June 09, 2017, 11:38:50 AM ---If I recall correctly, Harold shows the tool being presented to the corner of the wheel, not the full side?
The exception is drill grinding where there is very little pressure.
The only sure way to get a flat side is to use a cup type wheel, where you are grinding on the side :-)
Gerrit
--- End quote ---
I second this one. I have used the double ended bench grinder that way and it saves whole lot of wheel. Prolonged use side of the wheel not only thins and weakens the wheel, but also makes rings, grooves, and stops on the side and it is not really good idea to true the sides of the wheel.
The idea of using corner is to feed blank from front and not to press on the side, this produces same effect (effect on the tool blank) that feedin the blank sideways BUT without excessive wear to side of the wheel.
I went a little furher and feed the blank at acute angle into rim of the wheel. You end up with somewhat rhombic wheel, but it is better than using pure side presure.
Downside is that the corner wears off, but good news is that you are not using pure side of the wheel. You eventually need to true the face to prevet the rim disapearing completely and to remove steps, but it did work pretty well to me. This way you completely avoid leaving a stop/step onto side of the wheel. The rim wears faster, but this is the direction the wheel is intended to work and you can true the rim of the wheel.
Pekka
vtsteam:
Grinding on the side of the wheel in my experience does not put grooves in the side of the wheel for the same reasons that grinding on the front of the wheel, in my experience, doesn't put grooves there, either. Reason: I move the part around to even out wear so it doesn't put grooves in the wheel.
Plus I use the side for light dressing of small pieces, not full out grinding to reduce mass, as I mentioned earlier.. And yep, I do mainly use the side of the wheel at the corner. Makes sense from a practical grinding point of view anyway since the surface speed is greatest there.
Why try to grind a groove in the side of the wheel, and locate that where the wheel is ineffective? To solve that possibiltity by a total noob, naturally a manufacturer needs a blanket statement: don't use the side of the wheel.
Incidentally, putting a deep groove in the front of a wheel isn't a lot "safer" than the side. The thin remaining groove walls can break off -- and if you think about it -- you ground on their sides in making it, didn't you?
In short, don't make grooves at all.
PekkaNF:
Good point of avoiding any delicate steps or portrusions on normal bench grinding wheels.
While I completely agree with you, you must admit that many "cllasic" parting out and boring bar designs lead themselves careless side grinding stockremoval process if you don't put though to it or don't have much experience - yet. Those shouders can easily produce grooving.
Often use of the side can be eliminated with alternative approach:
http://www.sherline.com/pages/images/grndfig9.gif
So...if someone would ask an advice, I would tell that generally it is better to avoid using the sides for any but the lightest finnish and see alternative methods like using the cup wheel or different approach, like this:
http://www.tascione.com/Sherlinelathe_ins/grinding.htm
Pekka
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