Astrodog 9th July 2011, 07:25 PM I have some questions about hollow grinding from the experts (and any other yahoos!).....
I accept that grinding is generally needed when you have chinked the edge of the blade.... but with a high speed grinder you don't grind to right to the edge, for fear of burning it....
So how do I grind out the chinks, if I don't grind right to the edge? Do I need to use a belt sander first or something??
cheers
Lee
China 9th July 2011, 10:53 PM You do grind to the edge in fact you grind the old edge away to "grind out the chinks" you prevent buring or over heating the steel buy frequently cooling it by dipping in a container of water
Howard Pollack 10th July 2011, 02:37 AM Another trick is to put a very shallow crown on the wheel with a wheel dressing tool. This makes the contact point the tangent on that crown and therefore very small. Start at the center of the blade and be very careful as you get to the edges. -Howard
msiemsen 10th July 2011, 10:07 AM Grind the chink back with the blade square on to the wheel, then re grind the bevel. I always grind right up to and past the bevel. You need to use a coarse wheel and dress the wheel so it isn't glazed. don't be heavy handed.
Mike
derekcohen 10th July 2011, 02:02 PM Mike is right, but his description may not be clear.
Lee, you are correct in identifying that a thin bevel edge will burn and de-temper if you grind it. So what you need to first do is remove the thin edge - thicken it by grinding back it to a blunt edge. This is what Mike means by "square".
Now regrind the bevel, leaving a 1/16" at the edge unground.
Hopefully this does not confuse you more! :U
Regards from Perth
Derek
Astrodog 10th July 2011, 04:51 PM Now regrind the bevel, leaving a 1/16" at the edge unground.
Thanks - So at this point I hone with whatever - correct?? wet/dry, waterstone etc....
derekcohen 10th July 2011, 05:10 PM I was not so clear either ..
When I wrote "Now regrind the bevel, leaving a 1/16" at the edge unground", I was referring to a hollow grind.
Once this is done, go to your preferred sharping medium (sandpaper, waterstones, etc)
Regards from Perth
Derek
rsser 10th July 2011, 05:17 PM You can go right to the edge with the right wheel and when you're approaching it, just do one or two passes before setting the chisel aside to cool.
Cooling by dipping into water is said to create microfractures.
The big risk when getting to the edge is that the corners blue. Not enough meat to dissipate the heat in time.
As Mike says, you need a deglazed wheel and a light touch. And patience obviously.
Astrodog 11th July 2011, 12:12 AM Thanks guys - that explains everything.... I do plan on getting a blu-max wheel, but am having difficulty locating them - any ideas??
Astrodog 11th July 2011, 12:24 AM Another question - I did put a nice burn on an old chisel today in practice - do I just need to grind some edge back and start again? How much usually, because this burn is on a corner, and projects a good 3-4mm up the (crappy) bevel....
rsser 11th July 2011, 09:49 AM Grind it all away, or learn to heat treat.
And consider Norton 3X (seeded gel) wheels: details (http://www.jimdavey-planes-sharpening.com/EShop/Product.aspx?EshopID=8607ccbf-fea8-48e0-a1d5-90600a129f1a&CategoryID=39bde3d8-f788-4228-80d8-fc8997ae1c66&ProductID=17065e81-093f-4ba4-8885-c8926cdf1b62)
Carroll's Woodcraft sell Blu-max.
Astrodog 11th July 2011, 12:52 PM ....
And consider Norton 3X (seeded gel) wheels: details (http://www.jimdavey-planes-sharpening.com/EShop/Product.aspx?EshopID=8607ccbf-fea8-48e0-a1d5-90600a129f1a&CategoryID=39bde3d8-f788-4228-80d8-fc8997ae1c66&ProductID=17065e81-093f-4ba4-8885-c8926cdf1b62)
Carroll's Woodcraft sell Blu-max.
Thanks - will check them out - what is the difference between the 3X and Blu-max - from what I've read the blu-max is softer and wider? Are there more reasons to part with a little extra?
As a novice I need all the help I can, happy to buy the best wheel around!
Any recommendations for the other wheel? should I leave a stock grey wheel on or replace it also??? Keen to hear what others have done....
rsser 11th July 2011, 01:21 PM It's a while since I used a Blu-Max. It's claim to fame is the honeycomb structure that helps it run cool, but I found the bond fairly hard. J rated. The plus is you have 40mm width.
Davey's 3X wheels are K bond so a little harder but the 46# cuts quite quickly and cleanly IME.
That said, a coarse white wheel will do the job well enough with patience and cleaning. If you only have a few tools to rehab it will serve.
Keep the grey wheel for rough work. Most folk say it's not good enough for high carbon steel.
HTH
Astrodog 13th July 2011, 07:30 PM On the right track now I hope - just had my Norton 46-grit SG blue wheel delivered - hats off to the sandpaperman (http://www.thesandpaperman.com.au).... (36hr from order to delivery - well done!)
Thanks for the advice Ern.
Lee
rsser 13th July 2011, 08:04 PM Good stuff.
Now I haven't tried this yet with this wheel, but I'd follow the advice of another forum member re cleaning the wheel and go in hard with a carborundum stick (while trying to maintain a flat and square face).
My impression so far is that using a diamond T-bar to unclog the wheel effectively reduces the grit rating to something like that of the diamond, which is finer than I want.
| |