Wc 8" slow grinder

[BrazosJake]

I Think the paper flyer said $89 at my local store.

What caught my eye are the 2 white wheels it comes with. Those run about $50-$60 if you buy them yourself
http://m.woodcraft.com/Product/20809...ROO&gdd=150780

[dbhost]

That's a REALLY good deal for a low speed grinder...

FWIW, I paid $45.00 for my Ryobi 8" on sale, and another $40.00 for the wheels, and then $15.00 for the bushings to stop the nasty vibration the OE Norton bushings caused...

I went with a full speed unit on OneWay's recommendation, and do not regret it, but it does seem that a large number of other turners like the low speed models. To each their own.

[gsmittle]

and then $15.00 for the bushings to stop the nasty vibration the OE Norton bushings caused...

I drilled a centered hole in a piece of dowel for a bushing. It's been a temporary fix for a year now…

g.

[Sweet Willy]

Electrical stuff has never been one of my strong points. Can somene tell me why you just can't put a speed controller, say from/for a router on your grinder to slow it down?

[jgrobler]

I had one of the WC slow speed grinders for a few years, and it's way better than the $45 whatever I had before then.

[woodturner]

Electrical stuff has never been one of my strong points. Can somene tell me why you just can't put a speed controller, say from/for a router on your grinder to slow it down?

The inexpensive speed controllers are typically for small "universal" motors. They probably would work on a grinder, if the grinder is within the HP rating of the controller and has a universal motor. You might notice some loss of torque, but on a grinder that shouldn't matter - we typically don't want to apply a lot of pressure to the wheel when grinding, because it heats the metal.

You might have to start the grinder at full speed to have enough torque to spin up the wheels, but once the wheels are spinning, it should be fine to slow down the speed.

So, I don't really see a technical reason why it would not work - but I haven't tried it, either. If you do try it, let us know how it works.

[Sweet Willy]

I'm sure going to try it, but not sure when. I'll let you know.

[BrazosJake]

I'm sure going to try it, but not sure when. I'll let you know.

It wonn't work, the speed control works on universal motors, bench grinders are induction.

Don'ask me the technical difference beteen the two. Induction motors are generally larger, queter, and produce much more torque per watt of electricity.

Universals have brushes, run at higher rpms, and are found in hand held tools.

Do a search as this question has come up in the past and our resident electrical engineer explained in depth.

[Joe DeFazio]

I have owned this WC slow speed grinder for about four years. I use it all the time, and I like it. It is solidly built and has been trouble-free. I can't compare its white wheels with, say, more expensive Norton wheels, because mine still has the original wheels (which have been dressed quite a few times). I am satisfied with the stock white wheels.

The slower speed is really handy for avoiding overheating carbon steels while grinding (which can ruin their edge-holding abilities). So, if you need a grinder for lathe tools, reshaping chisels and the like, I do recommend this grinder.

[woodturner]

the speed control works on universal motors

Agreed, as I said earlier in the thread. The speed controllers don't work on induction motors, because the speed of an induction motor is controlled by the frequency of the supplied AC power.

bench grinders are induction.
...
Universals have brushes, run at higher rpms, and are found in hand held tools.

Universal motors are used in more than just handheld power tools. For example, my jointer-planer has a universal motor.

The real question is whether the poster's grinder has a universal motor or an induction motor. Most grinders of recent manufacture seem to have universal motors - Delta, Ryobi, most Sears, virtually all the imports, etc. High end grinders such as Baldors often do have induction motors.

One potential clue to a motor being an induction motor is speed - common induction motors are available with speeds of 1725 RPM and 3450 RPM, and the 1725 RPM is more expensive. If motor has an "odd" speed, it is most likely a universal motor, but a 3450 RPM or 1750 RPM motor could be universal or induction.

our resident electrical engineer explained in depth.

You must mean a different resident electrical engineer, LCHIEN maybe, but I'm always happy to help.

BTW, Delta is now selling their universal-motor-driven grinder with the router type speed control already built into the unit.
http://www.deltamachinery.com/produc...ing/item/gr450

[LCHIEN]

...
BTW, Delta is now selling their universal-motor-driven grinder with the router type speed control already built into the unit.
http://www.deltamachinery.com/produc...ing/item/gr450

oddly the linked page describing the 8" GR450 does not state what type of motor it has but the similar 6" GR275 states it has an induction-type motor. Both have a speed knob in the base next to the power switch, so I'm not sure how they vary the speed (there are some ways -but not that cheap- to vary the speed of an induction motor) but its unlikely one is universal and the other is induction. The information seems to be contradictory at this point.

[woodturner]

oddly the linked page describing the 8" GR450 does not state what type of motor it has but the similar 6" GR275 states it has an induction-type motor. Both have a speed knob in the base next to the power switch, so I'm not sure how they vary the speed (there are some ways -but not that cheap- to vary the speed of an induction motor) but its unlikely one is universal and the other is induction.

Oops - I inferred from the cost that it had to be a universal motor - I didn't actually find a specification that said that. As you noted, VFD and other means to control speed on induction motors are usually rather expensive, so I assumed (I know, I know ) it had to be a universal motor.

Perhaps they have figured out a way to do a low-cost electronic VFD for smaller motors.

[LCHIEN]

Oops - I inferred from the cost that it had to be a universal motor - I didn't actually find a specification that said that. As you noted, VFD and other means to control speed on induction motors are usually rather expensive, so I assumed (I know, I know ) it had to be a universal motor.

Perhaps they have figured out a way to do a low-cost electronic VFD for smaller motors.

Like you said, variable speed induction motors usually involve a relatively expensive set of VFD electronics, not usually found in under $100 equipment.
In inexpensive variable speed lathes and drill presses with induction motors usually fixed speed motors are used with variable diameter pulley systems to make them variable speed machines. But looking at the standard grinders and these particular grinders the grinder wheel arbor is obviously also the motor axle, these must be direct coupled motors. So I'm curious how Delta designed them.

Maybe with advances in electronics and grinders being rather lower power motors, Delta has incorporated lower cost VFD electronics into the base of that thing.