GMC Bench grinder

[Jack E]

I am now the proud owner of 2 fixed base routers and also purchased a GMC 200mm bench grinder

I want to use the grinder to sharpen my chisels (not turning chisels)
Will this work and should I use Aluminium Oxide wheels. If so where can I get them cheap, will they fit on most grinders, and what grades will I need.

[Bob Willson]

Read page 7, line 14 of the grinder manual Jack. It specifically prohibits you from sharpening wood chisels. What it actually says is: "Wood chisles should never be grinded"

[scooter]

Gday Jack, bearing in mind what Bob pointed out in the GMC instructions ( :confused: ), if you choose to ignore this it will certainly work.
You need to have some means of presenting the chisel to the wheel at the correct angle, the standard toolrests on bench grinders are usually hopeless for this so it could be a good idea to make up a bigger (& adjustable)tool rest mounted either on the machine or on the bench in front. You can buy these from Carbatec or Timbecon, I scored one for about $25 at the T&WW show last year & it is solid and effective.
The grey silicone carbide wheels are more inclined to burn the steel than the more friable abrasive in the al. ox. wheels, this said I still use the SiC wheels on my grinder with no burning, just ensure that you grind fairly lightly & intermittantly so the steel doesn't overheat. Burning can be exacerbated by the wheels loading up with metal or other contaminants so keep the abrasive clear by using a wheel dresser, diamond dressers are supposed to leave the best cutting surface on the wheel but the star wheel dressers do the job OK for cheaper. Dressing new wheels can also be a good idea if they vibrate (ie out of balance) a fair bit.
Good luck.............cheers..........Sean

[scooter]

BTW to state the obvious, you will still need to hone the bevel (& flatten the back) on some other sharpening setup, this applies for either wheel type.

[Jack E]

Thanks for the tips guys, I think I will throw the manual away or use it to make sure my table is level.
I will see if I can get cheap Aluminium Oxide wheels and go with them as I don't have that "light touch".
I am wondering if I could modify the wheel guards to fit a wider wheel, maybe 30mm so I can sharpen a chisel in one go.
I will use wet and dry on a piece of glass to hone the bevel and the rear of the chisels.
Has anyone had any success sharpening plane blades on a grinder using the same technique to hone afterwards?
Still after tips on the grit for Aluminium Oxide wheels,4000, 6000 etc?

[Bob Willson]

I think I will throw the manual away or use it to make sure my table is level.

More seriously. If you are going to use wider wheels then you must first ascertain if the actual shaft is long enough to accept the extra width.

[Jack E]

Bob,

There is about 5mm of thread protuding from the locking nut with a 25mm wheel fixed. This will allow me to go to 30mm wheels and still have the nut fully threaded. The only problem with this is that the outside flange may the sit on the thread (just) rather than on the shaft.
Do you think this will be a problem?

[Bob Willson]

I would think that as long as part of the flange is sitting on part of the unthreaded shaft then it will be enough to centrally locate the flange and thereby hold it centrally and balanced. If this is not the case, then you may need to make up a little shim bush for the flange out of sheet brass or somesuch.

[scooter]

Jack, the tool rest I got (from Carbatec, but I think there are a few the same out there) has a small lateral mitre slot with a small mitre guage than runs in it. This lets you hold the chisel, plane iron or whatever where it is just touching the wheel then move the guage & iron together across the wheel, grinding the whole bevel uniformly. This lets you grind wider blades than the wheel would allow. Your idea of using a wheel the blades thickness I reckon would take much more frequent dressing to try to keep the face of the wheel dead flat & uniform.
I'd encourage you to get one of these toolrests & try it before you shell out for the wheels, I had no problems with this method and am no expert
I did this with some chisels and some block plane irons and used W&D on some aluminium flat to hone, then metal polish on MDF brought the edges up sharper than I'd ever managed before.
For the AlOx wheels, I read the grits go from 10 to 600, the guy used a 60 grit white AlOx wheel with a vitrified bond, apparently gave a good balance of grinding speed & fineness of finish. I think you can go too fine which can overheat the steel moreso. Don't forget to leave the cardboard disks on either side of a new wheel when you mount it to your arbor.
PM me with your email address if you like & I'll send you a scanned copy of the grinding wheel article I have from FWW.
Cheers........Sean

[Red neck]

Multi-tool belt linisher.

A little more expensive but bolts onto a grinder and will provide a two inch wide belt for honing chisels, plane blades or with the side mounted table will serve as a disc sander. Available from 'bunnies' for about $170 plus the attachments. The belts last for ages and cost a fraction of the price of aluminium oxide wheels. Probably the most used grinding device I have in my shed.