CBN on a Tormek?

[Phily]

Over the past couple of years there have been numerous discussions on the pro's and con's of the cost benefits and effectiveness of CBN wheels v's whetstones and the practicalities of using a CBN on a Tormek.

A common arguement against Tormek is the slow speed and consequent loss of time. So the arguements have tended to favour CBN on a higher speed grinder so more time can be spent at the lathe.

The debate reminds me of my old IT days when everyone argued for faster and faster computers, even though the reality was that if they did a typing course they could achieve a 200% efficiency increase without spending a cent on machinery upgrades.

Professional woodworkers invest a great deal of time and thinking into setting up their workshops and refining their production processes, for them the time savings afforded by a CBN makes sense. I remember watching Richard Raffin hollow out a bowl at least 10 minutes faster than I could ever dream of. He went to his CBN and sharpened his gouge to perfection without thought of using a jig.

But for mere mortals is the extra cost of a CBN realy justified regardless of the speed of the grinder?? Wouldn't it make better sense to invest instead into improving the setup of the workshop; improving technique; and, tool shaping/sharpening skills?

As my Tormek stone is in desperate need of replacement I would love to hear counter arguements in favour of CBN's.

Cheers
Phil

[dai sensei]

I have my CBN on my slow speed grinder, half normal grinder speed, and it works a treat. I have the Tormek guides though set up beside it.

Some others have set up their Tormeks with a CBN without any issues. It would certainly work as well if not better than the normal Tormek wheel. My understanding is the only issue of doing this is the higher weight of the CBN, but to my knowledge, this has been proven to not be an issue.

[Pat]

Phil, I have a CBN on my T7. Set and forget for the day . . .

If you want to see, touch and play, I'm only down the hill.

[Phily]

Thanks Pat, always good to meet up with fellow turners and check out set ups. I'm flat out with a big landscaping project atm but will PM you in the near future to set up a time :) Cheers Phil

[Phily]

I have my CBN on my slow speed grinder, half normal grinder speed, and it works a treat. I have the Tormek guides though set up beside it.

Some others have set up their Tormeks with a CBN without any issues. It would certainly work as well if not better than the normal Tormek wheel. My understanding is the only issue of doing this is the higher weight of the CBN, but to my knowledge, this has been proven to not be an issue.

Wonder why Tormek isn't offering a CBN? Maybe they don't want to undermine their replacement stone wheel business? Have you seen any numbers on respective wheel longevity? Cheers Phil

[derekcohen]

I use 80/180 grit CBN wheels on a half-speed grinder. I have a Tormek, which I have not used much in 18 months since installing the CBN wheels. If I was to replace the 10" x 2" Tormek wheel (which are available in CBN), I would get a 180 grit, and use it dry. That would maximise the grinding speed and still leave a decent surface (which is helpful in reducing the amount of work to be done in honing).

The only reason for wet grinding is to reduce heat. This is a non-issue with a 180 grit CBN wheel at 90 rpm.

Regards from Perth

Derek

[BobL]

CBN does have minimum recommended speeds for wet and dry grinding.
What's interesting is the recommended speed range for wet grinding is faster and outside the range for dry grinding.
For an 8" wheel the recommended dry RPM range is 1450 - 2850, for wet its 2850 to 3600 RPM

see http://www.graffdiamond.com/upload/file/speed_chart_and_sfpm_recommendations.pdf
The recommendations are for efficient grinding (most stock removal for minimum wear) and of course they will still grind outside these speeds but I suspect that the wear rate will be greater. Maybe that's only for an industrial situation. And maybe its why Tormek are not selling CBN, or they have a large amounts of wheel stock to off load.

[derekcohen]

Bob, I think that 90 rpm would work in regard to grinding effectively - it is possible to remove metal by just rubbing a blade on the cbn surface. What is more of an issue is that the CBN wheel is not friable (unlike the Tormek wheel), and truing it to the blade rest might be an issue. It took a lot of fiddling to set the Tormek tool rests up on my dry grinder.

Regards from Perth

Derek

[hughie]

I agree with BobL about the speeds for grinding wheels and these are optimum speeds. But very few companies from what I have seen would adhere to these sort of speeds unless its already there on the current grinder or equipment. Its just one of those anomalies based on the dollar, add to that some folk will always have a different idea to what is recommended. Which some times makes me wonder how optimum are the optimum recommendations.
Looking at CBN wheels I would doubt if the lower speeds would be substantially detrimental to the wheel, the biggest loss would be slow stock removal. Pretty much the way slower speeds on a buffing wheel lengthens the job but really doesnt effect the wheel negatively.

What I have seen over the years is tool selection driven by cost of the operation, engineering is very competitive and machine tools are priced accordingly. So we have all these numbers too encourage sales , by suggesting higher levels of machining efficiency etc.

So we end up with a slightly slower sharpening process but one that provides a better edge with minimal stock removal. The upside is if you have a Tormek already it should do just fine as its a well made piece of gear and accurate enough to handle a CBN wheel.

[Phily]

Personally, the saving time argument of having a higher speed grinder (I actually have 2 high speed grinders) doesn't really work for me for 2 reasons: firstly I'm not a production turner so a few seconds more at the wheel doesn't worry me; and, secondly I'm not that proficient in my sharpening skills, so a lower speed grind helps me avoid making big mistakes! However, what does bug me BIG time about the Tormek is how quickly the stones develop hollows that need to be ground out. I actually enjoy sharpening chisels, but I definitely don't enjoy having to diamond hone the wheel so that I can touch up an edge - especially when I'm in the middle of making something. For me therefore, the biggest argument in favour of a CBN is that it is set and forget (and from what I gather, set and forget for a long time).

Thanks for the advice on grit size - I was leaning more toward 300 to 400 - but more from gut instinct.

I have seen a few comments on CBN's loading up with filings when dry turning. Has anyone tried strategically placing a rare earth magnet near the wheel?

Cheers
Phil

[smiife]

I have seen a few comments on CBN's loading up with filings when dry turning. Has anyone tried strategically placing a rare earth magnet near the wheel?

Cheers
Phil[/QUOTE]

Hi phil,
I have a magnet under my cbn wheel , it, s amazing
how many fillings It collects !

[Phily]

Phil, I have a CBN on my T7. Set and forget for the day . . .

If you want to see, touch and play, I'm only down the hill.

Hey Pat, your mailbox is full. Cheers Phil

[Phily]

I'm thinking of inventing a rare earth magnet with a plastic sleeve. Easy to attach to a grinder, slip off the sleeve and the filings fall off. No more filings on the wheel. Ummmm



I have seen a few comments on CBN's loading up with filings when dry turning. Has anyone tried strategically placing a rare earth magnet near the wheel?

Cheers
Phil

Hi phil,
I have a magnet under my cbn wheel , it, s amazing
how many fillings It collects ![/QUOTE]

[Uncle Al]

I'm thinking of inventing a rare earth magnet with a plastic sleeve. Easy to attach to a grinder, slip off the sleeve and the filings fall off. No more filings on the wheel. Ummmm


I think they are called 'clip lock bags':D

Alan...

[Pat]

Woops, Empty now.

[hughie]

I'm thinking of inventing a rare earth magnet with a plastic sleeve. Easy to attach to a grinder, slip off the sleeve and the filings fall off. No more filings on the wheel. Ummmm
Hi phil,
I have a magnet under my cbn wheel , it, s amazing
how many fillings It collects ![/QUOTE]

They have something already along those lines for collecting swarf. If you use two rare earth magnets and set them up with opposing fields,this will extend the field of the magnets considerably. Allowing you to use smaller magnets at less cost. :)
6X Cylinder ROD Neodymium Rare Earth Magnets 5x20 MM N45 | eBay (http://www.ebay.com.au/itm/6X-Cylinder-ROD-Neodymium-Rare-Earth-Magnets-5X20-mm-N45/231939373543?_trksid=p2141725.c100338.m3726&_trkparms=aid%3D222007%26algo%3DSIC.MBE%26ao%3D1%26asc%3D20150313114020%26meid%3Dbbe0a159f7d5449288b598501db8db2d%26pid%3D100338%26rk%3D4%26rkt%3D17%26sd%3D321556563714)

Fit them into a piece of pneumatic hose and wrap around the back of the wheel this should increase your receiving area and being in plastic, easily cleaned

[Phily]

I think they are called 'clip lock bags':D

Alan...

Dar gon it. There goes another million $ invention opportunity 😢 still, I think it could be worth trying by those folk having problems with filings? Cheers 😄

[John Saxton]

Dar gon it. There goes another million $ invention opportunity �� still, I think it could be worth trying by those folk having problems with filings? Cheers ��

I'm thinking Jaw's from the James Bond movies.