Slow Speed Bench Grinders in the UK

[ps.harris80]

Hi all

I have been using a standard bench grinder, to sharpen my turning tools, but am aware that a slow speed one would be better suited, especially given that I am using CBN wheels.

Given that they are popular across the big pond with even budget models available, why are they are rare as hens teeth over here in the UK.

Sofar only found two and of those two only one is small enough for my little workshop.

Other than those two, which are from Hope Wood turning and Axminster anyone know of any other makes available over here.

And why did they not catch on over here ?

Thanks for any input on this.

Paul

 

[Inspector]

Our 60 cycle motors are 3460 and 1730 RPM give or take and your 50 cycle is 2800 and 1400 RPM give or take. That puts your high speed right in the middle of ours. Doesn't really scream get a slower grinder unless you have a 10" or bigger wheel, which would be extreamy rare in a home shop. That's my theory anyway.

Pete

 

[Derek Cohen (Perth Oz)]

Hi Paul

I have this one ...

https://www.axminstertools.com/glob...7671?queryID=8d40843745683b5ea5288687dd2eeebe

It has been in use for over a decade without missing a beat. And nice and quiet. I run two cbn wheels on it.

I was possibly the first to write about using CBN wheels for plane and bench chisel blades, and my set up is described here:

http://www.inthewoodshop.com/WoodworkTechniques/UltimateGrindingSharpeningSetUp.html

The Axminster half-speed bench grinder is on the right (re-badged Carbatec in Oz). The other bench grinder, on the left, is also half-speed, from Rikon.



The tool rests have been removed from both. The CBN wheels use the Tormek BGM-100 tool rest, and this is superb. The Rikon is used for power buffing.

Regards from Perth

Derek

 

[BC'er]

You might want to consider the Makita 98202. The hard ~red stone is probably the one you would use most and one way to dress it is to buy a couple of rectangular water stones of the same grit and lap those against each other and the rotary stone to maintain flatness. They do tend to splash the surrounding area if you're not careful so putting the whole unit into a basin deep enough to catch what is thrown off the sides is a good idea. Even better would be sitting it on a couple of bricks or something else that is moisture-proof and putting a very small pump in the bottom to recirculate the cooling water.

 

[Sideways]

Look at the technical info provided by manufacturers of CBN wheels.
They are all well within SF/M recommendations running on a standard 3000 rpm 8" grinder.
CBN has good thermal conductivity. There's no need to get a slow speed grinder.

 

[ps.harris80]

Thanks for all the most helpful replies.

Think I may as well stick to the one I have, especially taking into consideration what Pete said about the different speeds between the US and UK frequencies, that makes sense.

 

[mr_offcut]

If one grinder is sufficient, a cheap VFD can make it run at any speed.

 

[Duncan A]

Not quite as simple as that; it would need to have a 3 phase motor

 

[gregmcateer]

These look well made

https://www.shentonwoodcraft.co.uk/sharpening-system/

 

[ps.harris80]

If one grinder is sufficient, a cheap VFD can make it run at any speed.

I did look into this but from what I found it seemed to indicate VFD's do not work on single phase induction motors.

 

[mr_offcut]

I've just done some further reading, and it CAN work, but it won't have very good torque at slower speeds. You also have to rewire and deal with the start capacitor. Looks like it would be way better to use a 3p motor.

I'm considering a large grinding stone wheel. Their usually over 1' and rotate slowly. Old carpenter I knew swared by them.

 

[ps.harris80]

These look well made

https://www.shentonwoodcraft.co.uk/sharpening-system/

I contacted them for price and availability etc, but didn't get a reply, so that scrubbed them off my list.

I have been doing some more sharpening today, and now convinced my full speed grinder is not giving me any issues, so will be sticking with it. The CBN wheels I use are rated upto 3000rpm so not in any danger of damage.

 

[TRITON]

If you have/get a machine that doesnt have a no volts release switch,and just a simple on/off, you can use a lamp dimming adaptor to adjust the speed.
https://www.ebay.co.uk/itm/15539593...NAGNPQ&hash=item242e51c8a8:g:xqEAAOSwHmBjobiS

 

[ps.harris80]

Thanks for the link

But it's my understanding that these things only work with brushed motors, my grinder is a brushless induction motor, which apparently run a full speed even when fed with quite low voltage levels.

Unless you know different. would love to hear it confirmed by anyone.

 

[Duncan A]

...and the item linked to is only 280W.

 

[SVB]

I use a crusen 6” wide wheel slow speed grinder with 180g and 80g cbn wheels. Realise cbn can be run faster but I find this gives me so much control - as tormek slogan, sharpen not shorten!

 

[Spectric]

You can use these

https://www.motorsandinverters.co.uk/product-category/inverters/single-phase-inverters/

 

[Agent_zed]

If you want cheap and cheerful https://www.toolstation.com/einhell-250w-200mm-8-x-150mm-6-wet-dry-bench-grinder/p28104 I have a SIP version that looks pretty similar. If you look in the reviews you'll see someone has made a jig and seems happy with the results.

I've used mine many times to refresh chisels etc and find it works nicely and leaves a much better finish that a high speed grinder.

 

[Sideways]

With a CBN wheel on a record 8" grinder, 500 Watts, light, controlled, cuts don't slow the wheel. If you want to remove metal and lean into it, you can slow the grinder down.
Running at half speed, which also means more of less half power, on any sort of electronic speed control will just make the grinder easier to stall. I really don't see the point when the wheel doesn't care.

 

[mr_offcut]

You could chuck the stone in a cheap brushless drill held in a stand for a low-tech option.

Pulley reduction on one end of the grinder?

Old carpenter I knew had a big slow 12" stone, It was geared from an induction motor.

I've not tried a single phase VFD, do they have a seperate leg for a start/run capacitance? May be worth contacting the company in the link above, though 139 is not cheap