More on Grinders

[Dennis J Gooding]

There has been quite a bit of discussion lately about the choice of grinders for sharpening woodturning tools. One candidate favored by several, including myself, is the Rikon 1/2 HP low-speed grinder. Others are doubtful that it has enough power. I would like to explore the pros and cons on a technical basis. If the concern is that the 1/2 HP Rikon grinder will bog down under heavy tool pressure, then I offer these facts. First, the 1/2 HP low-speeed grinder will produce the same maximum torque as a 1 HP high-speed grinder. Second, the tool pressure required to stall either is far far greater than one would ever use for tool sharpening or even rough shaping.

This latter statement is based on actual measurement of the performance of my Rikon 1/2 HP grinder with an 80 grit CBN wheel. I have measuring equipment that can measure the actual input watts to a motor for any given load. From the input wattage one can calculate the output horsepower, ( Actually, this number will be a few percent larger than the actual output power, because of heat losses in the motor.)

I took a a very heavy round nose scraper and applied it to the grinder and noted the force and the power input in the motor as I pressed the scraper into the wheel. At a tool pressure of 10 pounds, the motor was developing only 0.34 horsepower, about two thirds of the potential horsepower! In the few seconds that it took to make the measurement, the scraper was badly defaced.

I believe that the normal pressure used to sharpen turning tools is measured in ounces, not pounds. I did not attempt to determine the ultimate pressure required to stall the motor, because I did not want to sacrifice any of my turning tools nor the CBN wheel to the extreme pressure it would require.

One could argue, based on these results, that a low-speed grinder of 0.25 horsepower would we adequate for this purpose. However, the start-up time with massive CBN wheels probably would be a problem.

 

[GRJensen]

I have had one of the Rikon 1/2hp grinders for 4+ years, running with 2 CBN wheels. No issues at all.

I do give one of the wheels a spin when I turn on the switch ... gets the wheels up to speed much faster, and supposedly lengthens the life of the start capacitor.

 

[Don Wattenhofer]

The only problem I have with the 1/2 HP Rikon is the slow starting otherwise once up to speed they do not bog down.

 

[Bill Blasic]

I know I've written this before about the 1/2 HP Rikon that I had (when I set my daughter up with a lathe the Rikon went with it.) it would run for somewhere around 12 minutes after I shut it off. It intrigued me so I sat and actually timed it and wrote it down somewhere. It had 2 1" CBN wheels on it, yes it took about 5 or 6 seconds to turn up but that is no biggie.

 

[Rusty Nesmith]

I also have the Rikon low speed grinder. I turn the grinder on first. By the time I get the Vari-grind attached to my gouge it is up to speed.

 

[Glenn C Roberts]

My one horse Rikon with two 1.5" cbn wheels from Ken will get to full speed in about 1.5 seconds. However, the centrifugal switch does not engage on shut down until the motor is at a very low rpm (?), or almost stopped. If I power on at that low rpm, the motor takes almost 6 seconds to come up to full rpm because it is starting on the run winding. Don't know if they are all like that. Maybe some day I'll get around to playing with spring tension or replacement. Or maybe not... I always thought Rikon was an entry level quality brand anyway. Knew that before I bought it and sure enough...

 

[john lucas]

I have been using the rikon for a very long time. When I first bought a steel.cbn wheel I noticed the slow start up. Then i added a second Ken rizza nylon or whatever they are wheel. I honestly dont even notice the start up time. I turn on the grinder put my tool.in the jig or change.my Roborest setting and start sharpening. It's always up to speed by the time I get the tool.to the stone. I worried about possible damage to the motor due to the struggling start up but that's simply been a non issue.

 

[John Torchick]

I vote for the Rikon. Had one for several years and it does a good job. Don't have CBN wheels, just the factory wheels.

 

[Aaron Harris]

One could argue, based on these results, that a low-speed grinder of 0.25 horsepower would we adequate for this purpose. However, the start-up time with massive CBN wheels probably would be a problem.

FWIW, I don't have the Rikon, but an old Baldor .25 hp motor, on which I run two 1" CBN wheels without issue. Whether I remember to give it a hand-spin or not before grinding, it spins up strong and true very quickly.

Now, granted, I am just barely kissing the tool edges to the wheel surface as I roll them around, and it's an old Baldor, so it will probably outlive me, as it did the now-deceased knifemaker whose shop I bought out from his family some years ago. I'd like to think that he would be pleased that his sturdy old tools are still being used.

That said, I have nothing against modern tools, and in fact just last week bought Rikon's well-reviewed 14" bandsaw, which cut a bunch of heavy green walnut logs yesterday on the stock blade without issue. Just another data point.

 

[robo hippy]

Well, I prefer over built rather than under built. While the 1/2 hp Rikon does work, given how I use my tools, it won't last as long as my 1 hp Rikon grinders. Now the test is to see if the Rikon will last as long as my Baldor 3/4 hp grinders. I expect the Baldor to last at least as long as me, and if I am going to be like my dad, that is another 30 or so years.... I did time the 'come to a complete stop, on my Rikon the other day with 2 steel D Way wheels on it. Almost 3 minutes. The Baldor 1:25. Not sure that it makes any difference, but I feel like I have to stop the Rikon before I walk away, but not the Baldor.

robo hippy

 

[Dennis J Gooding]

Assuming there is no dynamic braking built into the grinders, and the same wheels on both, longer stop time probably means less bearing friction.

 

[Karl Loeblein]

Well, I prefer over built rather than under built. While the 1/2 hp Rikon does work, given how I use my tools, it won't last as long as my 1 hp Rikon grinders. Now the test is to see if the Rikon will last as long as my Baldor 3/4 hp grinders. I expect the Baldor to last at least as long as me, and if I am going to be like my dad, that is another 30 or so years.... I did time the 'come to a complete stop, on my Rikon the other day with 2 steel D Way wheels on it. Almost 3 minutes. The Baldor 1:25. Not sure that it makes any difference, but I feel like I have to stop the Rikon before I walk away, but not the Baldor.

robo hippy

I’m confused. Why do some turners want their grinding wheels to come to a stop quickly? Is there a danger that I should be aware of?

 

[Dennis J Gooding]

I’m confused. Why do some turners want their grinding wheels to come to a stop quickly? Is there a danger that I should be aware of?

Generally because you want to adjust a setting to match an existing bevel to the wheel or you want to use a setting jig that requires contact with the wheel. My CBN wheels are perfectly smooth on the inner rim and the sides, so I just rub the side with a finger to stop it quickly.

 

[Tom Gall]

Generally because you want to adjust a setting to match an existing bevel to the wheel or you want to use a setting jig that requires contact with the wheel. My CBN wheels are perfectly smooth on the inner rim and the sides, so I just rub the side with a finger to stop it quickly.

I've also rubbed the side of the wheel with one of those gum rubber type sanding belt cleaners. Extra friction and saves my finger. Especially when I used to do that with my matrix wheels.

 

[Emiliano Achaval]

Well, I prefer over built rather than under built. While the 1/2 hp Rikon does work, given how I use my tools, it won't last as long as my 1 hp Rikon grinders. Now the test is to see if the Rikon will last as long as my Baldor 3/4 hp grinders. I expect the Baldor to last at least as long as me, and if I am going to be like my dad, that is another 30 or so years.... I did time the 'come to a complete stop, on my Rikon the other day with 2 steel D Way wheels on it. Almost 3 minutes. The Baldor 1:25. Not sure that it makes any difference, but I feel like I have to stop the Rikon before I walk away, but not the Baldor.

robo hippy

Best Buy ever, over 20 years ago was my 3/4 Baldor 8 in grinder. Makes the Rikon next to it look like bad Chinese toy.

 

[robo hippy]

For me, wanting the wheel to come to a stop before I leave it is to make sure I don't accidently bump into the still spinning wheel. Since I grind off most of the bevels on my tools, I use that to bring the wheel to a stop. I figure it is a good habit for when I have play dates so some one else doesn't have an accident.

robo hippy

 

[john lucas]

That's exactly tly what I do Reed. After I vrind I turn off the grinder a d the round off the bottom.of the bevel with the wheel.with no power which almost completely stops it.

 

[Karl Loeblein]

Best Buy ever, over 20 years ago was my 3/4 Baldor 8 in grinder. Makes the Rikon next to it look like bad Chinese toy.

Ok, I‘m game. What do these two look like side by side?

As for me, I just installed two Spartan CBN wheels on my 1/2hp Rikon yesterday and can’t imagine many turners needing anything more powerful. Granted the Rikon platforms are dinky, but many turners use something else like the Wolverine jig anyways. The one item my grinder is missing is a light so it’s obvious when I forget to turn it off because it’s so quiet now. Guess I need to wire an led light to the grinder’s switch next.

 

[Tom Gall]

Ok, I‘m game. What do these two look like side by side?

As for me, I just installed two Spartan CBN wheels on my 1/2hp Rikon yesterday and can’t imagine many turners needing anything more powerful. Granted the Rikon platforms are dinky, but many turners use something else like the Wolverine jig anyways. The one item my grinder is missing is a light so it’s obvious when I forget to turn it off because it’s so quiet now. Guess I need to wire an led light to the grinder’s switch next.

......or, you can mount a switched power strip (6-outlet) below (or near) the grinder and plug in your light, grinder, and in my case, a dedicated shop vac with attached collector for grinding dust. However, I don't usually plug my grinder into the power strip.

 

[Karl Loeblein]

......or, you can mount a switched power strip (6-outlet) below (or near) the grinder and plug in your light, grinder, and in my case, a dedicated shop vac with attached collector for grinding dust. However, I don't usually plug my grinder into the power strip.

Tom, I like the idea of using a power strip that turns everything off when the main item gets turned off. What does your attached collector look like? Something homemade or purchased?

Edited: I realized a basic power strip would work as long as it can handle the current of the grinder and dedicated vacuum.

 

[robo hippy]

Hmm, never thought about using the off/on switch on a power strip to start up grinder and DC. I won't use my big shop DC system for metal dust. I have a Shop Vac air scrubber that could work nicely for a metal dust collector... Hmm, more ideas!

robo hippy

 

[Dennis J Gooding]

Well, I would not consider anything smaller than a 2 HP dust collector for this purpose.

 

[Gary Beasley]

Im not so sure your average power strip will handle the power of both those units, or even one of them. One of these power switches would be safer with a splitter plugged into the end.

Safety Power Tool Switch

No need to panic with our hands-free panic button.

www.rockler.com

 

[Tom Gall]

Tom, I like the idea of using a power strip that turns everything off when the main item gets turned off. What does your attached collector look like? Something homemade or purchased?

Edited: I realized a basic power strip would work as long as it can handle the current of the grinder and dedicated vacuum.

Karl, just went to the shop to check on your concerns. As stated above, I have my grinder plugged in separately, but it works with no problems with two lights when plugged into the same power strip. With the added small ShopVac there is a slight delay, but I also have a plug in switched outlet (from an old track light set up) to turn on/off the noisy vac if not needed.

Re: the collector you can easily make something to adapt. I use a Veritas Magnetic Dust Chute (Lee Valley) which is mounted just below the wheel(s). My current stand is metal so no problem. Previously I screwed a piece of metal (mending plates in my case) to the wood stand under each wheel....easy to move when needed. Bought mine in 1998 for under $20 - a little more now. https://www.leevalley.com/en-us/sho...0041-veritas-magnetic-dust-chute?item=05J2110

 

[Tom Gall]

Hmm, never thought about using the off/on switch on a power strip to start up grinder and DC. I won't use my big shop DC system for metal dust. I have a Shop Vac air scrubber that could work nicely for a metal dust collector... Hmm, more ideas!

robo hippy

Reed, I have a small ShopVac that I bought at a club swap for $5. It's only about 12" Ø and maybe 18" tall.

 

[robo hippy]

I still think some one needs to make a home shop sized DC system for picking up the metal dust. Every shop should have one because the metal dust will float around in the air like wood dust does, and especially with these exotic metals we are using, that is not good stuff to get into your lungs. Best guess is that just about anything will work as long as you have filters that won't catch fire from sparks. I wouldn't use my centralized DC for metal dust. Don't want any fires, other than in the wood stove... I do have one of the Festool vacs for sanding, and you plug the vac into the wall, and the sander into the vac. Start the sander and the vacuum turns on.

robo hippy

 

[Phil Hine]

I have been trying to come up with a good way to corral that dust. The CBN wheels without the guards seem to spread it very well. I tried some magnets under the wheels and it gets some of the shavings but not all by a long shot. I need to look at our maintenance shop setup. I think they have some sort of collection.

Phil

 

[Timothy Allen]

I wonder whether one could use their main Dust Collector system as the suction source as long as there is a dedicated cyclone and/or filter system inline right after the source of the metal dust, before getting to your wood dust duct work?

And @Tom Gall, I also wonder whether the magnets in the Veritas Magnetic Dust Chute collect some of the metal particles?

 

[Emiliano Achaval]

Ok, I‘m game. What do these two look like side by side?

As for me, I just installed two Spartan CBN wheels on my 1/2hp Rikon yesterday and can’t imagine many turners needing anything more powerful. Granted the Rikon platforms are dinky, but many turners use something else like the Wolverine jig anyways. The one item my grinder is missing is a light so it’s obvious when I forget to turn it off because it’s so quiet now. Guess I need to wire an led light to the grinder’s switch next.

I will post a picture. I believe you can see them when I posted about my new lights above them.

 

[Doug Freeman]

I wont use a shop vac or dc to catch metal dust off the grinder of sander due to sparks/fire - I’ve dealt with industrial dc fires. Industrial systems use spark traps and some are wet dc systems. Not sure either is available for small dc systems.

I guess the cbn wheels dont spark, so are probably safe.

 

[Tom Gall]

I wont use a shop vac or dc to catch metal dust off the grinder of sander due to sparks/fire - I’ve dealt with industrial dc fires. Industrial systems use spark traps and some are wet dc systems. Not sure either is available for small dc systems.

I guess the cbn wheels dont spark, so are probably safe.

Not if the shop vac is dedicated to the grinder. Besides, most sparks I've ever seen come off a grinder extinguished themselves within 6" or so. I have a 4' hose attached to the grinder collector.

 

[robo hippy]

Another concern, for me, would be how there have been several instances of turners finding glowing embers of metal dust under their wheels. Adding wind to that would fuel the flames. This is a safety issue that hasn't been properly dealt with yet. If the hose and hood are back 2 or so feet, probably not an issue, but I still wouldn't want to take any chances, no matter how well my shop is insured...

robo hippy

 

[Doug Freeman]

Not if the shop vac is dedicated to the grinder. Besides, most sparks I've ever seen come off a grinder extinguished themselves within 6" or so. I have a 4' hose attached to the grinder collector.

I agree most sparks do burn out quickly. You could go a long time and one day, you have a fire, that smoldered for several hours and didnt turn to flames till 3 am. As I stated, I’ve dealt with them in an industrial setting that had safeguards in place. I highly recommend a spark trap and minimum annual cleaning of the hose/ducting and spark trap. Piles of small particles can be ignited by an ember.

 

[Al Chavez]

I have a different solution rather than using my dust collector. I have an outdoor workbench and I set up my grinder there. While I do have to carry it in and out to use it I find that I can not worry as much about metal dust and sparks in the D.C. and after I am finished using it a leaf blower makes short work of clean up. This solution might not be a good fit for everyone but it works for me.
I also have much better lighting outdoors and plenty of fresh air. My workbench puts the center of the wheel about 52 inches up from the floor so I can easily sight the platform angles to match bevels on my tools. My lathe is also used mostly outside in the same work area but on a different bench. Total set up takes me 10 minutes and tear down takes me 15 or 20 minutes.
I'm using a Rikon 1 HP with CBN wheels.

Al in Texas

 

[Tom Gall]

I agree most sparks do burn out quickly. You could go a long time and one day, you have a fire, that smoldered for several hours and didnt turn to flames till 3 am. As I stated, I’ve dealt with them in an industrial setting that had safeguards in place. I highly recommend a spark trap and minimum annual cleaning of the hose/ducting and spark trap. Piles of small particles can be ignited by an ember.

That my be true, Doug ...especially in an industrial setting. As stated, I bought this small shop vac at a club swap for $5 more than 15 yrs. ago (and it was old then) and I have been using it exclusively attached to my grinder ever since.....no problems. It's so old it even has a metal canister - but I don't think that matters. Turners that have their grinders close to their lathes (near dust & chips) probably have a much greater chance of fire.

 

[robo hippy]

Doug, so, what is a 'spark trap'? Is it a specialized filter that will get the micro particles and is not combustable? Magnetic? Readily available? Available for specific cfm airflow? I am brain storming for a sharpening station for my shop. There will be days when there will be several turners in the shop at once, and possibilities of several turners sharpening at once....

robo hippy

 

[Doug Freeman]

@robo hippy do a search for spark trap and spark arrestor. You will find some for motorcycle and other exhausts, and larger commercial/industrial dc’s. Design is either a fine screen (engines) or impact plates inside to knock particles out of the airstream. Not sure what to use for smallish home size dc’s, which is why I havent done anything. It has not been a priority, but I could see the desire to have sharpening dc with students and several stations.