Dry grinder usage

[Bob Jones]

How do you know if you have dressed grinding wheels properly?

I have a regular speed 8in dry grinder with a 36 grit (stock) wheel. It seems to be taking me way longer than I think it should to grind LV and Hock plane blades. They are a mix of O1 and A2 steels. I suspect that perhaps I am not dressing the wheel enough, but I don't know how to tell this. Any suggestions or tips?

I have used 3 different dressers. The stock one has wheels with teeth. It makes plenty of sparks. The second one is a black bar that a machinist gave me. I don't know much about it, but he said it was the thing to use. It makes very little spark. The third is a Norton diamond dresser. To me, they all seem to work the same, but I know nearly nothing. I hold them to the stone with a light touch and move across the stone for about 60 seconds. Any help is appreciated. thanks

[Charles Bjorgen]

Dressing grinding wheels usually refers to removing any metal glazing left on the wheel from previous grindings. I prefer the t-shaped diamond dressers for this purpose. Dressing can also help correct some out-of-round problems with your wheel. I generally run some pencil marks on the wheel to check for this problem and then lightly apply the dresser until the marks are gone. However, you said you're using a stock wheel. I'd sure recommend replacing that with an aluminum oxide wheel for grinding plane blades. That's a whole other topic topic though.

[Tom McMahon]

A few years ago Joel Moskowitz wrote an article on the use of a dry grinder in Fine Woodworking, if you have not read it you should. He mentions it on his blog here.
http://www.toolsforworkingwood.com/s...ts+On+Grinding
There are two reasons to dress a wheel, first to clean and expose fresh abrasive for use, second to shape the face of the wheel which should have a slight radius. Properly shaped and used standard carborundum wheels work fine. The coarser they are the cooler they run. I bought a slow speed wet wheel grinder with a big white wheel, it is so slow I haven't used it in several years.

[Christian Castillo]

I know you want the issue resolved with your bench grinder, but I would suggest a belt grinder, team it up with a 36 grit belt and you'll never have ground something so fast or so cool without any water. I don't even bother using a cup of water when grinding new bevels. You wont wear out a belt in God knows how long unless you are making knifes and grinding down stock. Even then, a new belt is 5 dollars for a quality one, and you never have to dress it.

[Chris Fournier]

A few years ago Joel Moskowitz wrote an article on the use of a dry grinder in Fine Woodworking, if you have not read it you should. He mentions it on his blog here.
http://www.toolsforworkingwood.com/s...ts+On+Grinding
There are two reasons to dress a wheel, first to clean and expose fresh abrasive for use, second to shape the face of the wheel which should have a slight radius. Properly shaped and used standard carborundum wheels work fine. The coarser they are the cooler they run. I bought a slow speed wet wheel grinder with a big white wheel, it is so slow I haven't used it in several years.

The grit is only one factor that accounts for how cool a wheel cuts. The bonding agent and the friability of the wheel are also major contributors to the wheels ability to cut cool. I'm not sure why you would want a radius on the wheels face. This is counter intuitive to me and to standard practice in many grinding situations; a square face and a well set up jig would be my choice every time. Thsi is also the way that surface grinding is done.

[Chris Griggs]

The radius makes it easer to control where you are grind off material. It may not be a benefit with a grinding jig but for grinding freehand just using a tool rest it definitely makes it easier to get a nice grind. I agree that it is counterintuitive, but it really does help.

Bob, 60 seconds is much longer than you need to dress the wheel for. I dress mine for probably 2-3 seconds at most using the t shaped diamond dresser thatcame with mine. You just need to make sure the surface is clean and refreshed an when a wheel is spinning at 3600 rpms that only takes a few seconds. I'd say keep using the wheel that came on it until it gets too small, then get something more friable if you want. I use gray wheels, but white wheels are indeed faster

If you are grinding away a good bit of material it can take a bit of time. If you are just refreshing a hollow it will only take 30 seconds to a minute - sometime less. If your wheel is cutting slowly dress more frequently. When I'm grinding off a big chip or changing the angle, I dress the wheel as soon as it starts to cut slower and/or when I can tell that the steel is heating up faster.

My guess it also that you, to avoid overheating the tool are using a very light touch. This is a good thing, but I have found that if I frequently dress my my wheel I can actually use a good bit of pressure (relatively of course, don't go too hog wild) and grinding goes much faster. I only apply the extra pressure if I've blunted the edge first (say to remove a chip), and then lighten things up as the edge thins out. With practice you get a very good idea of how much pressure you can apply and not burn an edge. As you probably know, keep you fingers near the cutting edge when you grind, so you can feel the heat of the edge. You eventually get an idea of how hot is too hot - when it gets uncomfortable to hold at the edge that's when its time to dunk. Again, as you get a feel for this, you can start applying more pressure in appropriate situations and it really speeds things up.

Remember dressing is short, just a few seconds, but dress often. If your grinding a lot of, dress twice as often as you think you should.

[Tom McMahon]

I can't emphasize enough, how the Moskowitz article changed my ability the get a good edge. Dry grinding was one of the things I had the most trouble with. I burned a lot of edge corners. I threw a lot of money at the problem without getting very far. I bought a wet grinder with the big white wheel, a slow speed grinder, replacement white wheels, a new rest with a tool jig, nothing made much difference. The wet wheel stopped the burning but was very slow, the idea of the dry grinder is to remove a lot of metal fast when shaping or reshaping the cutting edge. I then read the article by Joel in Fine Woodworking, it changed my mental concept of how and why to use a dry grinder, and how to set it up. I have gone back to my old craftsman grinder with the original gray wheels, it's all I ever use and I haven't burned an edge since I read the article.

[David Weaver]

If you want to be conservative when you grind (I don't have a dip cup at my grinder for regular refreshing of hollows), take your plane iron or chisel or whatever and grind it and instead of putting it in a dip cup, every few passes pull the chisel or plane iron directly across your palm. Don't, obviously, grind something heavily until it's 400 degrees and then do that (it'll burn you, too), but it's a good way to see how hot the edge is without burning yourself.

You can pull something pretty warm across your palm, pull it slowly enough that you can feel it but fast enough that it won't burn you if it's hotter than you'd expect. If you use that method, you'll likely get to the point that you can fully refresh a hollow pretty quickly and still not burn your palm. I do use water, like everyone else, if I have to regrind something significantly.

(i still use the non-friable wheels, and would use a diamond dresser of all of those mentioned above. Just enough every several tools to make the surface fresh.)

[Tony Shea]

I used to struggle with my gray wheel that came with my grinder. It just loaded up and/or smoothed out too easily. But after changing my dressing stick from the square stone style to a cheap t-style diamond dresser I have much less issue. I did switch over to a friable wheel and have increased my grinding speed significantly. I agree that gray wheels do work but think they smooth out and load up to easily and cause speed to diminish. Even very coarse wheels will become smoothed over if dressed poorly. My best advise is to upgrade to a decent wheel and a cheap t-style diamond dresser (not familiar with the Norton, it may be fine).

[paul cottingham]

Sorry for the hijack, but is there a significant advantage to hollow grinding, as opposed to grinding with a belt grinder? Does the hollow really offer significant ease in sharpening? I know Leonard Lee kinda advises against hollow grinding, if I remember correctly.

[Derek Cohen]

Sorry for the hijack, but is there a significant advantage to hollow grinding, as opposed to grinding with a belt grinder? Does the hollow really offer significant ease in sharpening? I know Leonard Lee kinda advices against hollow grinding, if I remember correctly.

Hi Paul

I do not recall if Leonard Lee advocated freehand or guided honing, although I do suspect it was the latter (using the MK I honing guide). This would be of relevance in my logic since a hollow grind is especially helpful to those who freehand hone and use the hollow as a jig. By contrast, honing guides work by creating a secondary bevel. It matters less how the primary bevel was created, and a cool running belt grinder would make a lot of sense. That would create a flat bevel, and his can onl be stronger than a hollow grind (although I have never experienced an edge failing as a result of the hollow).

Regards from Perth (currently in Vegas)

Derek

[paul cottingham]

Hi Paul

I do not recall if Leonard Lee advocated freehand or guided honing, although I do suspect it was the latter (using the MK I honing guide). This would be of relevance in my logic since a hollow grind is especially helpful to those who freehand hone and use the hollow as a jig. By contrast, honing guides work by creating a secondary bevel. It matters less how the primary bevel was created, and a cool running belt grinder would make a lot of sense. That would create a flat bevel, and his can onl be stronger than a hollow grind (although I have never experienced an edge failing as a result of the hollow).

Regards from Perth (currently in Vegas)

Derek

He advocates a honing guide, the mk1 if I remember correctly. In fact, i don't believe he advocates a secondary bevel. At least he doesn't seem to in the material I've seen.

[Don Jarvie]

Suggest dumping the grey wheel and get a white wheel. It will run much cooler and cut faster. I switched and I rarely burn the metal anymore.

Also, if the grinder is slow speed it works much better.

[Bob Jones]

Thanks for all the tips and suggestions. There is lots of good information here being shared. I think I will just keep trying to dress the wheel. I think the problem is just me and my expectations.

To anyone suggesting that belt sanders are the answer, I will object. I have the really nice 1in belt grinder from LV with the super coarse belt and a strong Dayton motor. I'm slow at grinding with that too. I mean - put you to sleep and better to watch grass growing slow. Oh, and the blades still get hot - slow and hot, how does that make any sense????

It must be me. Tonight I counted up 5 different grinding methods that I have tried (sandpaper on granite, a super coarse stone by hand, belt grinder, 6in grinder with Norton 3x, 8in dayton with 36grit grey) in the last few years. I haven't been happy with any method. I'm considering buying a Tormek just to complete the loop of stupidity! I think that is the only option that I have not tried. Surely that could not be any slower in my hands and at least it should get good results. Hmmm...

Good news - I am pretty good at honing the blades once they are ground, so at least everything is sharp. Of course, I tried 4 different honing methods before I was happy with one. I'm seeing a pattern here that is bad for my bank account.

[David Weaver]

I'm considering buying a Tormek just to complete the loop of stupidity!

Yeah, that would do it. Buy friable wheels for your grinder (norton 3x) before you do that. It'll cost a tenth as much or less.

I don't have anything against the tormek, but if speed is the issue, that's not the answer.