Bench Grinder (or sharpening system)?

[Jacob]

discs aren't low friction. Anything hard behind an abrasive is high friction. ...

There is no friction between the sand paper disc and the aluminium disc behind it, unlike a belt sander where there IS friction between the belt and the platen.
erewego - D_W on ignore again, he never rests!

 

[D_W]

you're not understanding what creates the friction. You're literally trying to contend the heat goes through the platen, somehow doesn't set the paper on fire or smoking but can ruin the temper of the edge.

The friction is created by the contact surface and the abrasive. The reason a ceramic belt at very high speed doesn't trouble with it even on a platen (which is generally graphite covered or some kind of slick sacrificial surface to extend belt life, except in toy machines) is because the grit is shedded constantly, the contact points are not uniform with dull abrasive and the aggression of the cut sparks off most of the heat in shavings that literally will weld themselves together.

You're not grasping this, but the part about the platen is funny - that you can burn the edge due to the platen but the belt adhesive and tape is unaffected. Bizarre.

the problem isn't so much that you're not grasping this - it's that your not grasping it leads to terrible advice.

 

[Fergie 307]

One thing that always struck me as an issue with the idea of using a disc on something as wide as a plane iron. There will be a considerable difference in the speed of the abrasive over the work owing to one side being near the centre of the disc, slow, whilst the other side is at the outer perimeter, much faster. How do you compensate for that with any accuracy. I use a disc myself for putting the finishing touches to small metal working lathe tools, in my case using diamond lapping discs. I find it very handy, but the tips are of course very narrow compared to wood working chisels or similar.

 

[Jacob]

One thing that always struck me as an issue with the idea of using a disc on something as wide as a plane iron. There will be a considerable difference in the speed of the abrasive over the work owing to one side being near the centre of the disc, slow, whilst the other side is at the outer perimeter, much faster. How do you compensate for that with any accuracy. I use a disc myself for putting the finishing touches to small metal working lathe tools, in my case using diamond lapping discs. I find it very handy, but the tips are of course very narrow compared to wood working chisels or similar.

Imaginary problem. You move the thing about a bit, even have it at a tangent rather than aligned radially. The thing about freehand is that you watch what you are doing and adjust accordingly.

 

[Ollie78]

I really like the worksharp 3000. Its a motor with glass disks that you stick abrasive sanpaper to you can use the little andled bed to set the bevel underneath and then use th top to flatten the backs. Also it has these nifty wheels with holes in so you can see through to sharpen gouges and turning chisels.
Its dead quick to use, unlike the painfully slow tormach.
However, they have stopped selling them outside the USA now, I found this out when looking for some replacement sanding disks.

Might see one second hand though. I did see on ebay the other day a real old style veceroy sharpedge if you have the space for it.

Ollie

 

[Derek Cohen (Perth Oz)]

I've a significant number of chisels, turning tools, gouges & planes (mostly my late father's) which are in need of refurbishment as the primary bevels are all over the place.
Added to that, I need something to sharpen mower, strimmer & shredder blades.
I'm thinking a bench grinder will do most of this but is there any advantage in buying something like the Sorby or Tormek systems, or will a decent grinder plus my diamond sharpening stones achieve what's needed?
If so, which bench grinders do people recommend, especially as I'd rather "buy once, cry once" than spend on an inexpensive model which has "issues".

My current grinding system has been constant for several years. The write up is here: http://www.inthewoodshop.com/WoodworkTechniques/UltimateGrindingSharpeningSetUp.html

In brief, it is an 8” half-speed bench grinder with 80- and 180 grit wheels (the grit choice is for bench planes and chisels). The 180 grit gets 95% of the use. This is used with the Tormek BGM-100 tool rest.

What you get is a cool-running grinder which maintains its settings without needing adjustments, and has great accuracy for bevel angles (I use the Tormek angle setter).

I had a Tormek, but they are carthorse slow and the wheels require frequent squaring and leveling.

Regards from Perth

Derek