Use for Worn Out Grindstones

[Herman Trivilino]

Even when the old grindstone is officially worn out (190 mm diameter, I think) and is a pain to use for most purposes, it can still be used for things like cleavers and lawn mower blades that are so wide the Universal Support rods are not long enough.
This brings up the ad nauseum subject of the T4. The stone starts at 200 mm and you would junk it 10 mm later.

No. My comment about the 190 mm diameter applies to the T7/T8, not the T3/T4.

As Ken points out, the T4 has a smaller frame and water trough, as it's designed to work with grindstones that have a diameter of 200 mm or less, down to something far less than 190 mm.

And by the way, when you replace that 190 mm grindstone you might do the math and think that because 190/250 equals 76% you're discarding 76% of what you paid for. But since the area of the circular grindstone is proportional to its diameter, you're actually only discarding (0.76)² or about 58%. Still a bothersome amount, which is why we're so tempted to find uses for those old grindstones.

[Ken S]

Good thoughts, Herman. It's handy having a resident physicist!

Ken

[RichColvin]

A while ago, I asked about using worn T7/T8 wheels on the T4.  What I found is that the 250mm wheel is wider than the 200mm (T4) wheel.  Bummer.

[Ken S]

Rich,

If you buy a T8, the lifting water trough will allow you to get more life out of your grinding wheel.

Ken

[jeffs55]

Even when the old grindstone is officially worn out (190 mm diameter, I think) and is a pain to use for most purposes, it can still be used for things like cleavers and lawn mower blades that are so wide the Universal Support rods are not long enough.
This brings up the ad nauseum subject of the T4. The stone starts at 200 mm and you would junk it 10 mm later.

No. My comment about the 190 mm diameter applies to the T7/T8, not the T3/T4.

As Ken points out, the T4 has a smaller frame and water trough, as it's designed to work with grindstones that have a diameter of 200 mm or less, down to something far less than 190 mm.

And by the way, when you replace that 190 mm grindstone you might do the math and think that because 190/250 equals 76% you're discarding 76% of what you paid for. But since the area of the circular grindstone is proportional to its diameter, you're actually only discarding (0.76)² or about 58%. Still a bothersome amount, which is why we're so tempted to find uses for those old grindstones.

Great reply, Herman.

[Ken S]

I contacted support asking about the wear limit of the SG-200, the T4 grinding wheel. The answer is practical rather than numeric.

"As long as it runs in water you can use it".

Comparing a grinding wheel with another round object which wears slowly and is discarded before being fully cunsumed, is anyone driving on bald tires?

The first experiment I did using the Norton 3X wheels on my Tormek was with the not quite six inch (150mm) wheel I removed from my dry grinder. I had purchased the 46 grit wheel to grind away extensive mushrooming on two wood spliting wedges for a friend. The Tormek could handle very regular of just starting mushrooming; this mushrooming was the result of looking the other way for a very long time. A mushroomed head on a struck tool like a cold chisel is a safety issue due to the possibility of breaking off and causing injury.

I had thought of using 3X wheels on the Tormek ever since reading a one time post by a member who put his dry grinding wheel on his Tormek. He stated that it removed a lot of metal, and then he dropped out of sight. He used "a cheap Delta wheel". I thought, why not try a good 3X wheel?

The six inch wheel was just too small for the T7. The situation changed when I added a T4. I added some paper shim to reduce the half inch bore to twelve millimeter. I tried grinding a quarter inch bolt and was impressed with the amount of metal quickly removed. The six inch wheel is usable in the T8, but not ideal. I purchased eight inch 3X wheels in both 46 and 80 grits. Both work very well wet with the Tormek. Converting the bore diameter required drilling out a piece of plastic pipe. The 3X wheel removes metal much more quickly than the blackstone. When the 3X wheels finally become too small to "run in water"with the T4, I will return them to dry grinder duty with my dix inch grinder, thus lowering the wasted percentage. (Either the 46 or 80 grit is sufficient; there is no need for both. At either $40 or $50 US, a 3X wheel brings a lot of grinding fire power to the Tormek for a small investment. This is a very workable low cost solution for the woodturner who occasionally reshapes a turning tool.

In my case, I would start looking for nearby woodworking shows when my grinding wheel was appriaching 210mm. When the Tormek is being demonstrated at shows, one can often purchase jigs and accessories at an unadvertised 20% discount. The discount would sweeten the lost percentage. At 200mm, I would start using the new wheel, reserving the worn wheel for rougher projects. At 200mm, it has much useful life remaining, and would extend the useful life of the new wheel.

Ken

[jeffs55]

"As long as it runs in water you can use it".

That is actually the best answer that could be given. Brilliantly simple and totally accurate. If you could rig a raised water trough you could keep on using it until the curvature of the stone was so acute that it makes the edge of your tool too weak to be practical. Good job Ken.

[Ken S]

Thanks, Jeff.

I agree about the simplicity and accuracy of the comment. The thanks go to Stig and his support team.

Ken

[SharpenADullWitt]

"As long as it runs in water you can use it".

That is actually the best answer that could be given. Brilliantly simple and totally accurate. If you could rig a raised water trough you could keep on using it until the curvature of the stone was so acute that it makes the edge of your tool too weak to be practical. Good job Ken.

I've already got an easy (for me) way around that, when I get to that point.  My house still has one of the old metal laundry/soaking tubs, used back in the days with a washboard.  (drain hose hangs up top)
Presoak the wheel, then turn on the faucet over the wheel on a dribble and then drain into a pickle bucket for taking outside.
The machine will sit above the tub, so no electricity/water meeting.  I also plan that I will only use this for rough chip removal, to make the replacement stone last longer.
I have a LONG time to go to get to that point, and buy that time, I may no longer watch for and refurbish old tools, if I already have them.
I just would still prefer that, to a higher speed grinder and the heat involved.

[Herman Trivilino]

I contacted support asking about the wear limit of the SG-200, the T4 grinding wheel. The answer is practical rather than numeric.

"As long as it runs in water you can use it".

Interesting. My SuperGrind 2000 (predecessor to the T7) has a sticker on the side with a scale that allows me to easily read the grindstone diameter. The largest number on the scale is 250 mm and the smallest is 190 mm. Is there no such scale on the T4?

[Ken S]

Good question, Herman. Yes, the T 4 has such a scale with a range from 200mm to 165mm. The T7 has the same range as your SuperGrind. No surprise. The scale on the T8 has a range from 250mm to 180 mm. The lower limit is no doubt due to the adjustable water trough.

Let's approach this from a different view point. Herman, may we use you as our reference person? Looking back at your history with your grinding wheel and making your best guess for the future, how many more grinding wheels to you estimate you will wear out?

Do you anticipate doing much of the grinding which caused the most wear on your grinding wheel?

I have a similar question with my car, a 2011 Equinox with just under 100,000 miles. My mechanic tells me the brakes still have some life left in them. (I'm getting nervous, however, I am not a mechanic.) In the past, I have kept vehicles too long, and ended up paying too much in repair costs. I  plan to keep the car for another two to three years before we downsize to one vehicle. I anticipate replacing the brakes one time. my question is do I replace them very  soon and enjoy the benefit of new brakes or drive those miles with well worn brakes?

With a Tormek wheel, whether or not one squeezes the last micron out of the the grinding wheel, it will eventually need to be replaced. Do we want to use a new wheel, with the benefit of a larger diameter or a gallant attempt to capture a few more percent?

My gut feeling is that many of our individual answers lie somewhere in the middle. I welcome other thoughts.

Ken

[Herman Trivilino]

Well, Ken, I suspect my new grindstone will last about 7 or 8 years. I hope to last at least that long, myself. Hopefully much longer. So, maybe 2 or 3 more if I'm lucky.

Reminds me of my uncle. He wanted to replace a blown out light bulb in his vehicle. At the parts store they sold them in packs of two. He told the youngster behind the counter that he needed only one and didn't want to pay for two. He was told that's the only way they sell them, and that he could just hang on to the extra because he was bound to need it sometime soon. My uncle told him that he didn't suspect he'd be around long enough to be able to use the extra!

[Ken S]

Another good post, Herman. The story about your uncle gave me a good chuckle. My kind of guy.

Ken

[Airplanedoc]

I liked that story, I worked with a guy who lost the lower portion of his leg to a land
mine in Vietnam.  When the plant implemented safety shoes, he insisted he only should have to buy 1 since it didn't matter what happened to the foot he already lost, he could just put a new one on.  The plant safety guy finally convinced him to buy a pair of steel toe cowboy type boots.  On the second day of wearing the new boots he came in and requested medical leave to get his leg repaired down in St. Louis. Apparently he tried to take his boots off when he got home and ripped the foot off of his artificial leg not thinking that you have to be able to bend your ankle to put cowboy boots on or off. And he obviously has no control over what the joint in his artificial leg does.

The plant safety guy got harassed about that until the day he retired.

[bisonbladesharpening]

Does a SG250 for a T8 that is worn below 200
work like a new stone on a T4