• It's time to cast your vote in the January 2025 Turning Challenge. (click here for details)
  • Conversations are now Direct Messages (click here for details)
  • Congratulations to Alan Weinberg for "Elm Burl Bowl" being selected as Turning of the Week for January 27, 2025 (click here for details)
  • Welcome new registering member. Your username must be your real First and Last name (for example: John Doe). "Screen names" and "handles" are not allowed and your registration will be deleted if you don't use your real name. Also, do not use all caps nor all lower case.

8" Slow Speed Grinder ?

Doug Rasmussen said:
If you're taking the guards off as it seems a good many do, wouldn't the 7" grinder be adequate, or even the 6"?
Click to expand...

It looks like most of the 7" Baldor grinders in that price range are ½ HP and 3600 RPM. The main issue with single phase two pole motors (3600 RPM) is torque ripple which can be a significant vibration source. Also, the half horse motors may be marginal on providing initial pull up torque although they are no doubt better than the Rikon half horse grinders in that respect (which might not actually be half horse). I would much prefer an 8" four pole (1800 RPM) grinder where I can leave the shroud in place because the metal dust is just as much of a problem as grinding wheel dust. I believe that some of the Baldor 8" grinders have sufficient clearance in the shrouds to accommodate CBN wheels.
 
Bill, The 7" and 6" 1800 rpm grinders I mentioned are on Amazon.

I understand about vibration of 3600 rpm motors being worse than 1800 rpm, but by that argument you could also say that 3600 rpm grinders, which most bench grinders are, would be unsuitable for tool grinding. It isn't all that unusual to have 3600 rpm single phase motors on precision tool and cutter grinders with wheels mounted directly onto the motor shafts. Two that I know of are Cuttermaster and KO Lee.
 
Looking at the Baldor catalog, there is a huge price jump each time the grinder goes to a larger wheel size. CBN wheels have a very large mass and I don't know what their maximum safe RPM is, but I would like to have ample safety margin.

I think that there has to be some reason that it seems like woodturners prefer bench grinders with more expensive four pole motors over two pole motors. The high speed bench grinders used in industry are mostly three phase which means that torque ripple is very low ... probably lower than a four pole single phase motor. Also, I don't believe that the requirements for sharpening tools in metal machining has a lot in common with creating a knife edge for slicing wood. Actually, I hardly ever use my slow speed bench grinder anymore since I started using my Tormek about fifteen or so years ago.
 
You owe it to yourself to look at Woodturners Wonders, Ken Rizza the principal is a great guy and he is a Rikon dealer. Look here: https://woodturnerswonders.com/collections/rikon-grinders
I have a friend who manufactures Knifmaking Grinders, and he has told me there was a huge price jump in Baldor Motors due to some govt involvement--so his go to motor now is Leeson--he also told me that the Rikon grinders will last most people many lifetimes for grinding wheel spinning duty. I have both the 1/2 horsepower and 1 HP Rikon, I bought without all the guards and gunk since I use CBN wheels on mine--the special washers Ken sells are the shiznit--the wheels run beautifully true and grind cool and precise--I like Tradesmand stuff but it is designed for industrial use where cost is not such a factor.

I highly recommend Ken and Rikon--if I was just buying one today, it would be a Rikon 1 HP with a 220 grit and a 650 grit wheel.
 
Don C Davis said:
You owe it to yourself to look at Woodturners Wonders, Ken Rizza the principal is a great guy and he is a Rikon dealer. Look here: https://woodturnerswonders.com/collections/rikon-grinders
I have a friend who manufactures Knifmaking Grinders, and he has told me there was a huge price jump in Baldor Motors due to some govt involvement--so his go to motor now is Leeson--he also told me that the Rikon grinders will last most people many lifetimes for grinding wheel spinning duty. I have both the 1/2 horsepower and 1 HP Rikon, I bought without all the guards and gunk since I use CBN wheels on mine--the special washers Ken sells are the shiznit--the wheels run beautifully true and grind cool and precise--I like Tradesmand stuff but it is designed for industrial use where cost is not such a factor.

I highly recommend Ken and Rikon--if I was just buying one today, it would be a Rikon 1 HP with a 220 grit and a 650 grit wheel.
Click to expand...

For what it's worth, Reliance and Dodge were acquired by Baldor a few years ago and more recently Baldor was acquired by ABB a Swiss conglomerate. Beginning this year the plan is to rebrand Baldor motors to ABB.

Meanwhile, A.O. Smith, Marathon, and Leeson were acquired by Regal-Beloit.

Big fish being swallowed by huge fish.
 
Hmm.... The wheel guards, to me should be left on. Mostly to contain dust, and the metal dust floats around in the air just like wood dust, and some of the fancy metals can be toxic. There have been instances of glowing metal dust in the piles under the grinder wheels, possibly in the wheel guards, but can't remember. Long thread about over at SMC. With my 8 inch Baldor grinders, I can remove the outside wheel guard, but the inside one has to stay in place as it seals the inside from dust.

Looking at the 1/2 hp Rikon, I would never put the CBN wheels on it. Main reason is that it just doesn't have enough power to run them for any one other than the monthly weekend warriors. If you turn, and sharpen a lot, you need some thing more powerful. Comparing my old blue no name grinder from Woodcraft and my Baldor, the WC one had a higher wattage rating, but the difference in available power was about the same as the difference in weight, about 2 to 1. Probably about the same with the 1/2 hp Rikon and the 1 hp Rikon.

We do need an effective dust collection set up for the grinders and CBN wheels.

robo hippy
 
I looked at the Woodturnerswonders site....... WOW....Selling grinders without guards would keep me awake nights. All it'd take is a single accident to clean the owner out. Unguarded spinning things are so against established safety rules there'd be no defense for it. Rikon would likely be drawn into any court action too if they have knowledge of this situation.
 
robo hippy said:
We do need an effective dust collection set up for the grinders and CBN wheels.
Click to expand...

I have been using neodymium magnets inside of ziplock bags and placed under the CBN wheels (no guards) and they work surprisingly well.

20181028_145550.jpg 20181028_145613.jpg

The magnets are nickel size rounds, 3 for $6, which were what was available locally. There are a wide variety on line in various sizes and shapes, but these have turned out to be sufficiently effective.

The magnets collect most of the metal dust right as it flies off the wheel, but any over spray is easy to collect by "sweeping" with the bagged magnet.

Then hold the bag over the trash can, fish out the magnet with a screw driver or such, and the metal dust falls straight into the can. Drop the magnet back into the same ziplock and put it back on the grinder.

The magnets will want to stick to the motor housing, but an inch or two is enough distance for these small magnets and puts them under the wheels which are aluminum.

Today I touched up a bowl gouge and tried a varriation using an aluminum pie pan to extend my reach out in the front of the wheel.

20181028_153008.jpg 20181028_153029.jpg

I only used one of the magnets and this also worked well.

Here's an after shot showing the particles on the bagged magnet.
20181028_155211.jpg

I took it out carefully then swept the pan with a second magnet. There was more dust in the crevices. But overall great collection.
20181028_155441.jpg

I doubt any method will be perfect, but I submit this for your consideration.
 
You must log in or register to reply here.
Back
Top