Thread: CBN Wheel Details

Hi Graeme

I think 200w is too low power for a steel wheel. The shaft can be made to match the hole, but the grinder sounds underpowered. Woodworkers Wonders (USA) are selling wheels with composite bodies, which would be much lighter. And cheaper. Have a look at those.

Regards from Perth

Derek

What are you intending to sharpen Graeme?

If its just small metal work lathe bits the small grinder will be marginal but if its wood working edges I agree with Derek in that it might be underpowered.

FWIW I'm using an 8" wheel on a 1HP (true output power) grinder.

Hi Derek and Bob

Thanks for the quick and considered responses.

I want the CBN wheel for doing the initial and maintenance hollow grinding on chisel and plane blades (mainly) and to a lesser extent on spokeshave blades and turning tools. Probably want to stay with 150mm as this puts a little more hollow - but I will always listen....

Also thought that the 200 watt looked a bit small, but I missed that disclosure that your Carbatec grinder has the 750w motor on your website, Derek - the current Carbatec model is 200w and looks like just yours and mine, except for the colour scheme!

Had a look at the CBN wheels at Ken Rizza's Woodturners Wonders, Derek; they have 150mm radiussed wheels (US149.95 plus postage) and 200mm "Mega Square" (ie flat) wheels ($170). Even with these lighter aluminium alloy the wheels still weigh 2.1 kgs each. The 200w must still be marginal ????

I think I am starting to think about a bench grinder upgrade.



Fair Winds

Graeme

Originally Posted by derekcohen

Hi Graeme

I think 200w is too low power for a steel wheel. The shaft can be made to match the hole, but the grinder sounds underpowered. Woodworkers Wonders (USA) are selling wheels with composite bodies, which would be much lighter. And cheaper. Have a look at those.

Regards from Perth

Derek

https://woodturnerswonders.com/colle...inch-5-8-arbor. It appears that the composite wheel is only 25mm wide and that might put some off using it. It might be worth an email to see what Ken thinks the minimum power requirements are for the nylon wheels. I have always found him obliging to say the least.

Thanks Chris

Derek had previously referred me to cheaper composite wheels at Woodturners Wonders, but when I searched their website I could only find the more expensive and much heavier 6081 aluminium wheels. Found their composites now - thanks.

On consideration, there are possibly a number of difficulties with their composite wheels:

• their website lists only 8" wheels, and I have a 6" bench grinder,
• their composite wheels are radiused which Derek found sub-optimal - refer his website - I want it for chisels and plane blades.
• Price of US$99 translates as AU$135 plus freight which is about what Jim Carrol charges for steel wheels,
• I am wary of the longevity of composite. The plastic lacks the heat sink advantage of aluminium and steel wheels - will it still transfer heat build-up away from the blade?

The more I think about it, the more I think it is time to upgrade the grinder to one with more power.



Fair Winds

Graeme

Good points Graeme. The "heat sink" factor is especially important, in my opinion.

Regards from Perth

Derek

I read somewhere that CBN is 44 times more conductive than conventional al oxide wheels at removing heat.

On looking up thermal conductivity I found a wide range of values - it's strongly temperature dependent, and alloy and physical form dependent

At room temperature;
Steel ranges from 16 W/m ºC for SS to ~ 70 W/m ºC for some steel alloys.
Single crystal Al2O3 is around 12 but Porous Al Oxide is only 2.3 W/m ºC
CBN powder is 180 W/m ºC while single crystals are 1300 W/m ºC
Interestingly diamond is 2200 W/m ºC
Al ranges from ~60 for MgAl to about 250 for pure Al

Either way the CBN does not act as any sort of barrier to the transfer of heat - the limitation is thus the steel of the wheel itself.

Originally Posted by BobL

.........Either way the CBN does not act as any sort of barrier to the transfer of heat - the limitation is thus the steel of the wheel itself.

Thanks for the eloquent analysis, Bob.

The point that I was clumsily making is that the composite plastic would not conduct the heat away from the CBN as efficiently as an aluminium or steel wheel - and this could lead to a heat build up in the CBN and heance the blade, and essentially negate or reduce the advantages of the CBN over an AlOx wheel.

All good debate.



Fair Winds

Graeme

I use a CBN wheel for sharpening flat blades so my comments reflect that. I doubt if a nylon wheel would heat the blade to any great extent as the process happens so quickly there is not enough time to generate more heat that a finger touch would find uncomfortable.

I blame Derek Cohen for this disease I have been inflicted with, I am a total convert to hollow grinding and a mini bevel to finish the cutting edge. It is simple, does not require jigs on the stones and takes literally a few minutes. I wouldn't have a clue what angle I sharpen the final bevel at but Fletty can attest to how sharp my chisels are and Simplicity on how long it takes to reclaim an edge that looked like someone had been driving the chisel into nails. I now have a whole lot of sharpening stuff I no longer need.

Composite wheel idea is dead.

Woodturner Wonders just quoted $99.95 for a 180g 8" Spartan composite wheel 1" wide with radius edge, plus US$72.15 international shipping (Ouch!). Total US$172.10 which equates to AU$227 plus bank charges.

For once, best deals seem local.


Fair Winds

Graeme

Yep, pays to shop these days with the AUD where it is. It is interesting to observe that local prices have not moved much since the AUD dived so who is/was having a lend of who?

Indeed Chris. Funny how when the Aus dollar starts diving against the greenback they bump our prices but when it's going the other way they don't drop.

Complaining to retailers doesn't do anything either, from my experience in retail and logistics it's the distributors taking the extra off the top usually.

Originally Posted by bueller

Indeed Chris. Funny how when the Aus dollar starts diving against the greenback they bump our prices but when it's going the other way they don't drop.

Complaining to retailers doesn't do anything either, from my experience in retail and logistics it's the distributors taking the extra off the top usually.

I know this is more than slightly off topic, but this is the ABC's take on the brave new world of on-line retailing
Dynamic pricing: Retailers using artificial intelligence to predict top price you'll pay - RN - ABC News (Australian Broadcasting Corporation)

Hi Ian

Sorry, but dynamic pricing ain't new. (Just some tardy reporting!) It has been used by the major retailers - supermarkets, department stores, hardware stores, deep discounters, servos, etc - for at least ten years. The basic concept is that you constantly churn (their word) prices so that the customer no longer has a concept of a "normal" price, so it makes comparison pricing more difficult to impossible.

I know one deep discounter who not only churns prices but they also churn stock. After an alotted time they simply remove all of a given line from their shelves and actually move the stock to a different branch. The implied message is that you have to buy the item when it is available, BUY NOW, or you will miss out.

Their is a masssive library of publications on shelving strategy and pricing strategy in the business/commercial professional literature.


Fair Winds

Graeme