More on sharpening

[Arron]

Scary sharpening just doesnt sound the right way for me to go. I saw in Brunnings a GMC bench grinder with one large white wheel with water bath, and one gray wheel: This is it (http://www.gmcompany.com/57_NTS2000A_BG150A_BG200A.jpg) .

I assume this is designed mainly for sharpening. I couldnt find out much about it. Can anyone suggest the role this plays in a sharpening system. My understanding is that the gray wheel spinning at 2800rpm would simply burn chisels or planes. The white wheel turns at 130 rpm which seems to be a good speed but has no tool rest or anywhere to fit your own. It is described as 'suitable for sharpening tools' though it also seems to be quite coarse at 100 grit. Is this really a good sharpening tool. Is it mainly just for coarse shaping, or can it go part-way to honing a tool as well.

thanks
Arron

[derekcohen]

Arron

I caught Norm on the New Yankee Workshop two Saturdays ago, the episode where he builds a Sharpening Station. His guest on the show demonstrated a machine which looks to my eye to be the Tormek Supergrind 2005 (on page 92 of the Carbna-Tec catalogue, price $799). I must admit that the demo was almost enough to turn me into a Normite from a Neanderthal. I really am sorely tempted! If I was looking at a machine, this must be considered near the top of the list. The Tormek does have very nice rests in fact, this is the feature that makes the machine so desirable - plus it has the ability to grade and re-grade the (one) stone from 220 to 600 grit and back.

The closest machine I have seen (in the Carba-tec catalogue, page 91) to the GMC is the Delta Universal Wet/Dry Grinder, which runs at 3450 rpm (dry) and 70 rpm (wet), and costs $349.
There is another Delta, the Delta Sharpening Centre ($399), which may improve in the area of tool rests.

What is the cost of the GMC? Where are the tool rests?

I did try a cheapish (Chinese?) machine like this a few years ago. It lasted about 15 seconds in my workshop. The wheel was out of alignment and would not run true. I didn't bother after that and have stuck with my Japanese waterstones. As an aside, I am now increasingly sharpening freehand and only using a jig (the Veritas in my case) to establish the initial bevel angle. It is sooo much easier and sooo much quicker than any machine.

Regards from Perth

Derek

[Arron]

Hi Derek,
the GMC machine is $115. I have only ever bought one gmc tool before and it didnt last long, but I would be willing to give this one a try if I could find out exactly what it did.

I'm having a look at page 91 in the carbatec catalogue now. The delta sharpening centre looks good but I notice its alu oxide wheel runs at 3600 rpm dry. I dont understand how that could be useful sharpening as when I tried a chisel on 2800 rpm once and it burnt pretty quickly, even though I was quenching it. Is that what others find, or is it practical to grind a chisel on a fast wheel?

Another option is to use a spare 2 speed electric motor (3/4 horse) I have at home, as well as a spindle mount I bought at a local fair for $12. It would hold two wheels nicely - possibly in some type of home made water bath. A chisel grinding jig like the one on page 91 would give me a good tool rest. My question is what sort of wheels should I use and at what speed? I was thinking of a 100 grit alu oxide dry wheel at 1000 rpm and a 220 or even 400 wet wheel at 100 rpm. From there I could hone on a diamond lap. I really have no idea about any of this stuff though. Any thoughts, anyone?

cheers
Arron

[derekcohen]

Arron

Have a look at the thread at http://www.woodworkforums.ubeaut.com.au/showthread.php?s=&threadid=5303

We covered most of these issues there. The concerns you raise about burning the metal are very real, which was one of the reasons I have begun to restore a hand grinder (yes, there were a few sniggers from the back benches when I first mentioned this). There is a pic of that there as well.

My 2 cents is that, if you plan to use a full speed bench grinder (about 3450 rpm), you must use a very coarse white or pink wheel (they are the same composition, just different colours) of about 60 grit. These discipate the heat better. Use very light strokes, remove frequently and quench in a nearby jar of water. I don't believe that a light touch only is all that is needed. It only takes one moment to blue the edge.

Regards from Perth

Derek

[ozwinner]

Hi all
I just ordered me a Delta sharpening centre from Carba-tec.
After a week of no show I rang them, was told the Delta sharpening centre is no longer available in 220v, so I switched for the cheaper Tormek, cant wait for it to arrive.
Cheers, Allan :D