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View Full Version : Chisel Sharpening - Grinder Size



smidsy
5th January 2005, 12:37 AM
Hei Guys,
My club uses 200mm bench grinders for chisel sharpening, I have just made my sharpening jigs but my grinder is 150mm - the size difference is not an issue for the jigs because I've made them to suit my grinder.

What I am curious about though is that the smaller wheel means that the curve of the wheel is sharper.

Is this going to make a difference in terms of the sharpening - especially when I'm sharpening the same chisels on both the 200mm and 150mm grinder.

Cheers
Paul

macca2
5th January 2005, 01:29 AM
It will make a slight difference to the shape of the bevel. Whether it will be enough to cause you some concern only you can tell when you sharpen them on the 200mm after using the 150mm at home.
The same would apply if you were sharpening them on a new full size wheel and then on a worn down wheel some where else.
I would rather stick to the one wheel to save myself any hassles.
If all else fails replace your home grinder with a 200mm. they do better job any way.

Macca

vsquizz
5th January 2005, 02:00 AM
Hollow ground Paul, we did this awhile back and I remember Derek (the dark side) Cohen putting his case for using a smaller wheel. Have a search around.

Cheers

silentC
5th January 2005, 08:09 AM
Woodturners usually recommend an 8" wheel. I use a 6" and it seems to work OK but then I'm not a woodturner's armpit. With the 6" wheel, the hollow grind will be deeper and there will be less metal behind the cutting edge, so it might go blunt quicker. The included angle is effectively sharper, which can be a good thing for cutting but a bad thing for edge durability. Maybe you need to lift the handle a bit more when using a smaller wheel.

gatiep
5th January 2005, 09:06 PM
Paul


It wont make any difference to performance of the tool, but each time you change to different wheel diameter you loose unnecessary steel, mate!

200 mm stones grind cooler due to the bigger circumfrence and all 200 mm grinders can handle a 25 mm vide stone. Most 150 mm grinders take 13 mm or 19 mm stones and it makes it tricky to grind gouges on them with the jig you are using, as the gouge tends to slip off the wheel. Incidently there is absolutely no difference in the jig you use for 200 mm or 150 mm, so whatever you adapted was not necessary.

I have posted pics that are in the instructions with the commercial jig under a post "Grinding Jigs"

:)

smidsy
5th January 2005, 09:53 PM
Hei Joe,
I saw that other thread and I have posted a couple of comments.
The main issue for me is that I sharpen my chisels when I feel they need it, so that means they will be sharpened sometimes at Liddlelow and sometimes at home.
Given that two of my chisels are hamlet (my babies) I certainly don't want to take off more than I need to so I will have a look around for an 8 inch grinder, although as usual money is tight.
I may look at a GMC and use it exclusively for sharpening and nothing else, I figure they couldn't stuff up something as simple as a grinder.
Cheers
Paul

powderpost
5th January 2005, 11:28 PM
I have been woodturning for about 40 years and taught woodturning for about 15 years. Grinding a hollow simply makes the tool easier to hone. I only grind a tool when the bevel becomes flat, or is no longer hollow. Then I take care not to interfere with the cutting edge or the back of the honed surface. With this in mind, it doesn't really matter if a 6" or 8" grinding stone is used. I once used a 4" hand operated bench mounted grinder. Hardly the optimum, but it did get me out of strife with no long term damage to the chisel. After all that, my preference is still for an 8" grinder fitted with an aluminium oxide wheel. Dressing the surface of the grinding wheel with a diamond dresser, lightly and often, certainly helps... and use light pressure when grinding. I no longer need to quench tools in water and do not burn the edge, which by the way, will not draw the temper on high speed steel, or so the manufactures tell me.
Jim

gatiep
5th January 2005, 11:56 PM
As Jim says, Al Ox wheel, 200 mm, very light pressure, dress wheel often and I hone with a diamond lap. Been at is for a while too. ( lol )

:)

Ben from Vic.
7th January 2005, 12:57 AM
200 mm stones grind cooler due to the bigger circumfrence :)

Jo,

You are probably right, but as an intersting thought, I was wondering if the increase in dia. which reasults in an increase in stone speed (as seen by the object to be sharpened) from 1627 meters per minute for the six inch to 2170 meters per minute for the eight inch (both at 3,450 rpm), would heat the cutting edge any faster?

Ben.

gatiep
7th January 2005, 02:43 AM
I don't know about the theoretical stuff but in practice, having both a 150 mm and 200 mm grinder with the same grit stone, it just seems that the 200 grinds cooler, as it doesn't overheat the steel as quickly. It is purely a practical observation.

Cya

Jigsaw
7th January 2005, 08:12 AM
With regard to chisel sharpening, is there any reason why you can't use a belt sander. The belt sander could be mounted upside down in a jig.
I have heard of this before but have not tried it, I thought I would throw the idea to the masses for comment.

rsser
7th January 2005, 08:21 AM
Darlow and others speak favorably of using a belt sander - eg. the kind you can mount in place of a wheel on your grinder or one of those narrow vertical mount jobs as part of a combo. Virtues are flat grind and cool running.

I favour regular touch ups with a hone rather than a wheel - quick and saves metal. And also polishing the flute on gouges with a slipstone or diamond hone - takes two good surfaces to get a good edge.

gatiep
7th January 2005, 09:55 PM
Paul


I really would like to make a money saving suggestion to you. Sharpen your turning tools on your 150 mm grinder. Buy yourself a diamond lap, either medium or fine, ( blue code or red code ) not extrafine ( green code ) then when at the club you just hone the bevel and cutting edge of the tool, like your instructor Reg there and myself does. I hone about 6 times, before the flat is big enough to slow the honing too much, then I regrind ( do not read that as reshape!!) The lap will cost you from $25 tot $69 depending on the size you get. It will outlast you, so it is a cheap option. You are welcome to ask Reg about this one. He will also tell you that each spark on the grinder is your valuable tool steel being ground off. Diamond laps are quick, efficient and saves your tool steel heaps.

:)

RETIRED
7th January 2005, 11:50 PM
I was going to stay out of this one but I can't help myself. :D

Paul, I have been turning for longer than I care to remember. I am a production turner and I use a 6" grinder and have the same $25 grinder that I started with.

It is an el cheapo Taiwanese one that is set up properly every time I put a new wheel on it. It is only used for grinding tools, has no jigs or rests.

As Joe says, save your money.

smidsy
8th January 2005, 02:09 PM
Hei ,
The problem I have is that I have a 6 inch grinder (I think I actually have 2 maybe 3 of them) but my club has an 8 inch.
The concern I have and the reason and I'm thinking about upgrading my grinder is because of the different cuts between the two. I want to be able to sharpen my chisls at home or the club and not worry about taking excess metal with a different grinder.

I will check out this diamond lap Joe mentioned, and see where I go.
Cheers
Paul

RETIRED
8th January 2005, 07:09 PM
Paul. I read the original reason before replying.

I have used 4".6",8" and even a 24" sandstone. Fast grinders and slow ones, wet ones and dry ones at various demos and the amount of difference it makes is nil, nada or zilch.

The amount of steel removed in the different sizes is negligible.

Save your money and keep your 6" with good wheels.

powderpost
9th January 2005, 09:52 PM
Geez, I got ripped off, my taiwanese grinder cost me $75 in 1980, But then it is still working so I had better cut my losses?????? :)

Jim