FWW article - always hollow grind chisel / plane blades?

[Will Blick]

This months FWW magazine had an article for sharpening.... the author had an interesting take on the subject. His position was, always hollow grind chisel and plane blades. His reasoning is, with a hollow grind (on a grinding wheel), you should have a nice recess between two exposed surface areas, one at the edge, and the other where the iron meets the start of the angle for the edge. Then, you can sharpen free-hand on water stones, as you always have two reference points, which keeps the blade from rocking.....which is what often happens if you only use a micro bevel, which a honing jig does nicely. But the authors point was, with a hollow grind, no reason to waste time jigging up the blades in a honing jig, as its just as fast and accurate to free hand.... makes perfect sense to me... I thought this was a brilliant contribution, which I have never seen before..... at least the "reason" for the hollow grind. Anyone agree? Anyone do this now?

[Mike Henderson]

The woodworking school I attend teaches the same thing. The problem is getting the hollow grind. If you use a medium or high speed grinder (1725/3450 RPM) grinder, you risk overheating the tool, making the edge soft. The other alternative is to purchase one of the slow speed water cooled grinders but they're expensive. The other problem is space. If you don't have room to leave it set up all the time, it's a real pain to get everything out and do the sharpening. The school has a "sharpening room" where everything stays setup - and they have a bunch of the low speed water cooled grinders.

I use a hand jig (the LV MKII) and put a 25* bevel on my chisels, then free hand hone to a higher angle as needed in use. For me, with limited space and money, that's a better solution.

But the hollow grind idea is not new - it's been around for a long time. In fact, I was surprised that they were publishing it because I thought it was very well known among woodworkers.

Mike

[Also, I don't know if he says this, but you should not hollow grind Japanese chisels.]

[Will Blick]

Hi Mike, I too use the LV MKII for plane blades and chisels, a very well made jig.

I realize the hollow grind concept has been around forever, but the part I never heard before was.... produce the hollow grind to free yourself of using the honing jig every time you need a tune up on the edge....

He did mention in the article about the risk of over heating..... I never found the jig that time consuming where I thought it was an issue....but, free hand with equal results would be nice....and encourage me to tune-up more often...

I wonder if a round metal file would be a safer way to gain a hollow grind. Interesting how there is always a con for every pro...

[Mike Henderson]

Will - I think you can ignore the jig for honing once you have established the original bevel. The reason I start with a 25* bevel is that I can then add a secondary bevel of greater than 25* just by free hand honing.

So after I do my original sharpening (at 25*), I start using the chisels. On hard use, the 25* edge dulls quickly. I take the chisel and hone it on a fine waterstone, drawing it backwards freehand, until the edge is smooth and sharp. Then I go back to work with a bevel that's greater than 25* - I don't know what it is and don't care. When that edge dulls, I go back to the fine stone and do the same freehand honing. When the microbevel gets too long, or the secondary bevel too steep, it's time to go back to the jig and re-establish the original 25* bevel.

Anyway, that's the way I work and it works out well for me.

Mike

[Will Blick]

Mike, I follow you..... but the argument in this article, which I seems very sensible... is.... with only a micro bevel, free-handing becomes hit or miss....why? Because it may seem like you are holding that micro bevel flat to the stone when free-handing, but in reality, it doesn't have enough surface area to provide sufficient feel to keep it flat... hence the authors recommendation of the hollow grind, which gives you, in essence, two micro bevels, (one on each side of the hollow grind) so you have a long platform of surface area that hits the stone, making free-handing easier and supposedly a more accurate micro bevel.

I am not suggesting your method is not sufficient for your work, I was just exploring this article.... before doing something dumb :-)

[Mike Henderson]

Mike, I follow you..... but the argument in this article, which I seems very sensible... is.... with only a micro bevel, free-handing becomes hit or miss....why? Because it may seem like you are holding that micro bevel flat to the stone when free-handing, but in reality, it doesn't have enough surface area to provide sufficient feel to keep it flat... hence the authors recommendation of the hollow grind, which gives you, in essence, two micro bevels, (one on each side of the hollow grind) so you have a long platform of surface area that hits the stone, making free-handing easier and supposedly a more accurate micro bevel.

I am not suggesting your method is not sufficient for your work, I was just exploring this article.... before doing something dumb :-)
Yep, I understand. That's what the school teaches, also. My problem is getting the hollow ground (because of the issues discussed earlier).

I don't in any way disagree with you. I was just offering an alternative.

Mike

[Robert Rozaieski]

I hollow grind and hone freehand. Works great even for thin Stanley plane blades. I use a regular old high speed ginder with no problem. Just dip the tool in water every couple passes over the wheel. If it starts to feel warm, dip it. Once I started using this method, I sold off my honing guide as I quickly was able to learn to go without it. I hone much more often now as well and tend to work with sharper tools as I don't put off touching up a slightly dull edge since it now takes mere seconds to do. No more time wasted setting up the training wheels. I highly suggest you try it.

[Will Blick]

Ahhhh, a supporter of this system, thanks Rob. I think we would all hone more often if we could avoid the jig....

Question: what is the "ideal" diameter grinding wheel to create an optimum hollow grind on chisels and plane blades?

[Robert Rozaieski]

"Ideal" is a personal preference. I use a stanard 6" high speed grinder. A cheap one at that. No fancy do-dads and a shop made tool rest. Other people like 8" but they are a lot more expensive so 6" works just fine for me. I use oil stones as well but with this method of honing, stone type doesn't matter because you aren't taking off a lot of metal with your stones. All types of honing methods work; oil stones, water stones, sandpaper. Like Nike says, just do it! You'll like it ;).

[Michael Faurot]

The other alternative is to purchase one of the slow speed water cooled grinders but they're expensive.

I think that would depend on what you consider expensive. If we're talking Tormek--I'd agree those devices and most of the clones seem expensive to me also.

Grizzy has two slow speed wet grinders that don't seem all that expensive to me. The G1036 (http://www.grizzly.com/products/Slow-Speed-Grinder/G1036), which looks to be a clone of the Delta 23-700 (http://www.amazon.com/Delta-23-700-Universal-Horsepower-Sharpener/dp/B0000223ZT) (which also isn't all that expensive) and the T10010 (http://www.grizzly.com/products/10-Wet-Grinder-Kit/T10010) which looks to be a Tormek clone. Harbor Freight (http://www.harborfreight.com/cpi/ctaf/displayitem.taf?Itemnumber=95236) also has a Tormek clone.

One potential issue with any of these wet grinders is they all have 10" wheels, except the Harbor Freight model which has an 8" wheel. With the larger wheel the hollow grind will be less.

I have the Delta 23-700 myself and like it for putting a fresh grind on things and then finishing things up with water stones.

[Jim Becker]

I just read that article today and frankly, it makes a lot of sense to me. I do sharpen free-hand and it's pretty clear that the hollow grind reduces the work a bit, etc. Do note the comments around working the back of the blade...stopping before lifting clearly can be pretty important to avoid an unwanted back bevel.

[Raney Nelson]

I am a very strong proponent of this system. I'm one of those guys who bought and tried every jig and device you can find. I've used a Jet SS grinder, a LV MKII flat disc grinder, three or four different jigs, sandpaper and glass, and on and on. Once I started turning, and got somewhat comfortable with my grinder (a Woodcraft 8" 1725 RPM) I tried the hollow grind and freehand - which is a very common technique. Honing the blade is incredibly fast, and touching up is as well. I would say it takes me 2 minutes to refresh a grind and hone the blade. Touch-ups take under a minute. Literally. I would say I re-hone five to ten times before re-grinding, and then only because the bevels are beginning to get larger and honing takes longer. I usually go from the grinder to 10 strokes or so on 4000 waterstone, then 10 strokes on 8000, a few back and forth strokes to remove the wire edge and voila!

The one thing that I think is a possible barrier for this, as Mike rightly pointed out, is that you really need to be able to leave your grinder set up. I bit the bullet and devoted a small utility table in my shop to sharpening - I keep my grinder, space for stones, and an inset tupperware tub of water. This makes it seriously easy and quick to touch up an edge, which I find is really necessary for me - otherwise I tend to 'push' longer between honing than I really should.

I cannot recommend hollow grinding and freehand honing stronly enough. WIthin a month of beginning to experiment with it, I sold my Jet wet grinder, all but one of my honing jigs (I kept an eclipse-type for the occasional use - I still use it for some of the narrower plow plane blades, and for a couple of my paring chisels.).

[Peter Quadarella]

You guys have faster mail than me :(. The technique is tempting, but I'm not sure I'm willing to dedicate space to a grinder yet. It may come to that though.

[Don C Peterson]

I'm a fairly recent convert to hollow grinding. I just picked up a couple of old hand powered grinders on ebay and was pleasantly surprised at how easy it is to hollow grind (once I made a decent tool rest) and then how much easier it was to get a razor edge on all my tools.

[Greg Campbell]

The school I'm attending teaches hollow grinding for both plane blades and chisels. Plane blades are honed using the hollow grind to register as described above, but we were told to hone chisels with a secondary bevel. This way the grinder can be set up for 25 degrees (for both chisels and plane blades), then the secondary bevel raises the chisels grind to 30 to 35 degrees to make the edge more durable.

I have japanese chisels and have hollow ground without chipout problems as longe as I keep the secondary bevel at 30 degrees or above. I ground them around 25 degrees once and they cut great for 2-3 hammer blows, then chipped out badly.

At school, each bench has a sharpening station and we are taught to hone freehand. Takes a while to learn, but makes resharpening really easy and quick. They also use hand crank grinders with 6" white/pink grinding wheels. Hand grinding also takes a while to get used to, but you get good results pretty quickly and overheating is much less of an issue since the grinder speed is low. This is the setup shown in the Krenov books.

[Ron Dunn]

I've never ground plane blades or chisels.

I use wet-and-dry paper for sharpening, with one of the first-version Veritas sharpening jigs for alignment.

Thinking about the mathematics of the problem I probably use my plane irons and chisels more quickly using this method, but I'm a casual hobbyist so that isn't an issue for me.

[Pam Niedermayer]

Even though one could consider every hand tool a kit, this and other such manipulations make one wonder why the makers bother to provide full flat bevels and flat backs. There's something in me that recoils from the waste. Maybe I need to buy cheaper chisels? :)

Pam

[Robert Rozaieski]

Even though one could consider every hand tool a kit, this and other such manipulations make one wonder why the makers bother to provide full flat bevels and flat backs. There's something in me that recoils from the waste. Maybe I need to buy cheaper chisels? :)

Pam
Actually, my AI chisels were hollow ground at the factory. The first time I honed them, the hone only came up on the edge and heel of the bevel. It was a very slight hollow grind however, probably done on something like a 12" wheel. I didn't even know they were hollow ground until I honed them as the hollow grind was not obvious from just looking at the bevel. The backs were flat, as they should be.

[Raney Nelson]

Even though one could consider every hand tool a kit, this and other such manipulations make one wonder why the makers bother to provide full flat bevels and flat backs. There's something in me that recoils from the waste. Maybe I need to buy cheaper chisels? :)

Pam

I can't tell if you're serious or not, but the amount of 'waste' here is so negligible that I really cannot possibly imagine anyone balking at this for that reason. I know Japan has a different tradition regarding this, but in the western world this is far from an unusual or radical proposal. To be honest, I am pretty shocked that this is a new idea to anyone - I am under the impression that it is the most common sharpening technique there is - it certainly seems to be among the professionally trained folks I've met...

Again, I know this is not true for japanese blades, which I believe is the tradition you are more situated in, correct?

[Derek Cohen]

..the authors point was, with a hollow grind, no reason to waste time jigging up the blades in a honing jig, as its just as fast and accurate to free hand.... makes perfect sense to me... I thought this was a brilliant contribution, which I have never seen before..... at least the "reason" for the hollow grind.

Good grief, Will, that is as old as the hills!

Perhaps I might interest FWW in this idea I have about sandpaper for honing ....

Regards from Perth

Derek

[Chris Padilla]

For those of you lamenting the "old as dirt", it may be for you but not for everyone! I appreciated the article very much. There are babies and newbies born every day!! :)

[Brian Kent]

I need a better tool rest than the one that came with my grinder, but I'm in a no-cost mode. (I would far rather donate my hard earned money to the oil industry than waste it on fine tools).

Could we see a photo of your shop-made grinding jig? I know it's probably simple, but I'd rather learn partly by your mistakes.:rolleyes:

Brian

[Dave Anderson NH]

Remember that just about every magazine technique article on almost any topic except a new tool coming out has been done before in some magazine. Friends in the magazine publishing industry have told me that the "half life" of a subscription is about 4 years. Hence every 4-6 years articles get redone by different authors on the same subject but with a slightly different twist to them to make them appear fresh. We as Neanderthals, more than anyone, should appreciate that there is rarely anything new under the sun.

As for the hollow grind. I use it more on turning tools than on chisels and plane irons, but I do use it on them occasionally too.

[Tim Sgrazzutti]

For the people who have not read this artice, there are a few things that nobody has mentioned. Of course hollow grinding has been around for a long time, but Joel points out some modern improvements that make it easier to do without overheating the edge. These improvements are the type of wheels he uses (norton 3X blue wheels on a 6" 3450 rpm grinder), and profiling the wheel to a radius with a multiple point diamond dresser.

[Raney Nelson]

For the people who have not read this artice, there are a few things that nobody has mentioned. Of course hollow grinding has been around for a long time, but Joel points out some modern improvements that make it easier to do without overheating the edge. These improvements are the type of wheels he uses (norton 3X blue wheels on a 6" 3450 rpm grinder), and profiling the wheel to a radius with a multiple point diamond dresser.


This thread is relating to a different article - Joel's article on grinding was in last month's issue. This one is in the newest issue, and is entirely about freehand honing. The author recommends a HG (I believe he calls it 'indispensible') to facilitate the honing.

[Bob Smalser]

This months FWW magazine had an article for sharpening.... the author had an interesting take on the subject. His position was, always hollow grind chisel and plane blades.

Hollow grinding has been the school solution since grinding wheels became common in the 19th Century. When there's less to hone, honing goes faster. But hollow grinding is also why there are so many stubby chisels on eBay. Between grinding and honing you remove 4 or 5 times the amount of steel that you need to.

[Will Blick]

> Good grief, Will, that is as old as the hills!

But Derek, I am younger than the hills? To me, it was new.... I am an admitted newb Neander, but loving it....


Anyway, I am glad I started this thread, I learned some different view points. I think the poster who spoke of waste, was only referring to the total amount of metal that must be removed by honing as the grind wears down..... making the honing task longer.... It seems some people perceived it as a waste of metal in terms of $ ?


I think the length of the blade angle is signficant here. The shorter the length of the blade angle, the less metal needs to be removed during honings... hand plane blades fit this category well, at least all the LV ones I have. but for some chisels the blade angle encompasses a lot of area, and therefore a lot of grind, and therefore a lot exposed metal surface areas when honing, specially when the grind is wearing. So maybe this technique is more useful for short edged blades vs. longer edge blades.... am I making any sense?

[Joel Moskowitz]

Hollow grinding has been the school solution since grinding wheels became common in the 19th Century. When there's less to hone, honing goes faster. But hollow grinding is also why there are so many stubby chisels on eBay. Between grinding and honing you remove 4 or 5 times the amount of steel that you need to.

Moxon in the 17th century describes hollow grinding in detail and in those days with much softer honing abrasives hollow grinding was important for all the same reasons it is today but even more so.

[Mike Dyer]

Something that's critical to this article, but evidently easy to miss, is the author's recommendation that the grinding wheel be dressed with a rounded grinding edge rather than flat across. The purpose of this rounded grinding edge is that it greatly reduces the chance that you will burn the edge.
For me, this was a breakthrough, as it has virtually eliminated my tendency to burn the corners of chisels and plane blades.

[Johnny Kleso]

Yeah but in the 17th Century they had peddle powered wheels 3 feet round :)

So there was not much of a hollow as compared today..

Brian Kent said:
"Could we see a photo of your shop-made grinding jig? I know it's probably simple, but I'd rather learn partly by your mistakes.:rolleyes:"

Here is a pic of the ones I made for y 10" HF grinder

https://home.comcast.net/~rexmill/sharpening/MKIII/2.jpg

[Derek Cohen]

Will, when you reported that an article you read recommended hollow grinding as if it were a new method, per se, then the reaction of others is laughter. This is understandable as the method is, as Joel points out, as old as the hills.

The light goes on when Mike makes reference to a rounded grinder wheel face. Now I know that the article is one written by Joel Moskowitz, who has responded in this thread, and I would say that his contribution here is an important one. Joel writes not simply about hollow grinding, but how to improve the method of hollow grinding.

I believe strongly in hollow grinding blades. I do so because it facilitates easier freehand honing. Hollow grinding will not have the same allure for those that prefer to use honing guides. Nor will it be a factor for those using blades that are not recommended to be hollow ground, such as laminated blades for planes and chisels.

Honing guides are generally important when it comes to honing BU plane blades since the bevel angle is a vital ingredient in determining the cutting angle (unlike blades used BD). In the past I have recommended that BU plane users who wish to camber their high angle blades work with low (e.g. 25 degree) primary bevels and use a high secondary bevel. Thick blades with high angle bevels require too much effort to camber, so the aim is to reduce the thickness to a manageable level. Do this via a microbevel or a secondary bevel. It is too difficult to get the angle right freehand. It is straightforward using a honing guide.

My article: http://www.inthewoodshop.com/WoodworkTechniques/TheSecretToCamberinBUPlaneBlades.html

Personally, I would rather freehand all my blades, and I find the use of a honing guide intrusive. I would like to hollow grind the BU blades as well. So I have started experimenting with this - can I achieve the same ease of honing a camber if the bulk of the material is removed via a hollow? Keep in mind that my BU smoothers use a 50 degree secondary bevel. On a straight bevel this is a lot of steel to remove even for a mind camber. Will a hollow grind make it possible?

Regards from Perth

Derek

[Raney Nelson]

I would like to point out again that we are now discussing two separate articles. Last month's was by Joel Moskowitz, and related to grinding... (it contained, among other things, a suggestion to crown the grinding wheel - this was a new idea to me, and I've found it a brilliant piece of advice.)

This month, there is a second article, by Hendrik Varju, regarding freehand honing rather than using jigs. In this piece, he suggests that hollow grinding is an important part of success at freehand honing. (I believe this is the one that was the motivation for Will's post - though I could be wrong...)

[Will Blick]

> This month, there is a second article, by Hendrik Varju, regarding freehand honing rather than using jigs. In this piece, he suggests that hollow grinding is an important part of success at freehand honing. (I believe this is the one that was the motivation for Will's post - though I could be wrong...)

Raney, you are NUTZ-ON right, thank you. I thought I made this clear, but for some reason, my Aussie friend keeps hammering me ....


I have always been familiar with hollow grinding on bench grinder to achieve an edge, I have done it for years, it's been around since the dawn of time. I have always been aware of honing on a stone with a honing jig, I do it often. I have always been aware of free hand honing on stone, I try it a lot. (admitted not very good though)


However, I never saw that keen relationship of using a hollow ground away from the edge, for the sole purpose to create two surfaces which will enable much easier freehand honing. And, I am not embarrassed by it, as I am an admitted neander newb. I also have read two books on sharpening, AND NEITHER of them suggested this technique....so, I wonder how many people were really aware of this clever technique.


However, it's hard to be upset at Derek for long, as he always comes through with such informative neander posts. Since most all my planes are BU, I can appreciate his position of the blade itself producing the angle....vs. BD, where the frog produces the angle. In which case, I may stick to using my Veritas MKII honing jig to insure straight and consistent edges, which the honing jig assists in.

I also like Dereks suggestion of reducing the blade angle for blades that will be cambered....another very valid point, which obviously escaped my thinking.

[Raney Nelson]

However, I never saw that keen relationship of using a hollow ground away from the edge, for the sole purpose to create two surfaces which will enable much easier freehand honing. And, I am not embarrassed by it, as I am an admitted neander newb. I also have read two books on sharpening, AND NEITHER of them suggested this technique....so, I wonder how many people were really aware of this clever technique.



Will,

Try it out and let us know how you like it. For me it was a revelation. Sharpening went from a chore to a non-issue in about 30 seconds... about as nnoying or trying as having to clean the shop from time to time, or stop to make a pot of coffee :) .

[Derek Cohen]

Hi Will

My apologies if my response to you appeared condescending. That was not my intent. I have not yet received my copy of the latest FWW mag and have, therefore, not read the article. My reaction is to what is implied, and this may not be an accurate perception of what is written. What I find amazing is that an article could be published that infers that that the relationship between hollow grinding and freehanding is a new discovery. While I accept this may have been a revelation to many readers who are making the jump from guides to freehand honing (as it was for me in my own time), this method goes back many, many generations of woodworkers. I do hope that the article stated this and that the author is not claiming ownership of the concept. That is what is laughable (not the method, per se).

Several months ago I purchased a Tormek. Believe me I was as surprised as anyone! I came to the realisation that I would like to grind a hollow as close to the edge of the bevel as possible. This is not recommended on a high speed grinder (viz. over-heating the edge). The Tormek grinds cool and makes this extreme hollow grind a doddle.

With the grind at the edge it is possible to freehand a true microbevel - not simply a secondary bevel. Following the primary bevel, one only requires a couple of strokes on a 1000 (for the camber), then same on a 5000 and a 8000 Shapton to have a razor sharp plane blade.

Rehoning is an equally speedy process since there is so little steel to hone.

In January I definitely had a brain storm. :) I can only blame this on the fact that my workshop moved outdoors owing to an addition above the garage/workshop. Call it sunstroke! I went out and bought another highspeed grinder, one to match the radius of the Tormek to speed up grinding of new or restored blades. In other words a 10" grinder! (You think yours is a grinder - THIS is a grinder!!). The Thing terrifies me, so it has not had much use.

http://i13.photobucket.com/albums/a262/Derek50/Sharpening/GrinderandTormek.jpg

Regards from Perth

Derek

[Raney Nelson]

Derek,

The article does not in any way imply that this is a new, or unusual, process.

On a related note, though - I have taken to grinding right up to the edge on chisels and plane blades, and haven't had an difficulty yet. I am fastidious about dunking in water, and I have also recently switched to the Norton 3x wheels that Joel is selling. In this particular case, the hype about these wheels is true. They run very very cool. Well worth the slight premium they command over white/pink friables.

A 10" grinder and Tormek? You, sir, have way too much free time and an obviously overactive mind. Forget losing temper - you should be more concerned with melting! Is is a full 3800-ish RPM model?

[Derek Cohen]

Hi Raney

The wheels on the 10" grinder spin at 2800 rpm. This is the equivalent to a high speed (3800 rpm) 8" machine. I run a 46 grit white Norton wheel. I actually got it to grinder D2 plane blades.

I plan to add an 8" 3X wheel. What I need to determine is whether these are also known as "Blu-Max" (sold by Norton), as this is what I believe to be the version sold locally ..

http://www.timbecon.com.au/assets/images/products/lhgw-200.jpg

Regards from Perth

Derek

[Will Blick]

Raney, if I start using chisels more, I will buy the right grinder and wheel and try it.... for plane blades, since almost all mine are BU, I rather spend the few extra minutes with the honing jig...

but I hear, touching up the blade is such a huge benefit.... and removing any hindrances can only encourage you to do it more often...

[Raney Nelson]

Hi Raney

The wheels on the 10" grinder spin at 2800 rpm. This is the equivalent to a high speed (3800 rpm) 8" machine. I run a 46 grit white Norton wheel. I actually got it to grinder D2 plane blades.

I plan to add an 8" 3X wheel. What I need to determine is whether these are also known as "Blu-Max" (sold by Norton), as this is what I believe to be the version sold locally ..

http://www.timbecon.com.au/assets/images/products/lhgw-200.jpg

Regards from Perth

Derek

I can't help much with the wheel identification, other than to say it certainly looks like the 3x wheel I have. Good luck with that behemoth!

[Will Blick]

Derek, no hard feelings, your reputation is solid, your intentions always seem to be genuine.... sometimes words in a post don't accurately represent what we would say in person. You are a wonderful contributor to this forum, I always enjoy reading your contributions, as well as your web site.... You are truly a Neander x10.

[Alan Zenreich]

I hope folk don't mind me waking up this old thread.

I can use some opinions here about grinding plane blades.

I'm in an unusual (and fortunate) position in that I have a piece of equipment that most woodworkers don't have in their shop. It is a variable speed Bader III 2"x72" 1.5hp belt grinder. I can configure it several ways... but the two most interesting are with an 8" hard rubber wheel, or with a flat vertical platen.

I bought it originally for knifemaking, and now I'm repurposing it as the grinder of choice for sharpening turning tools, flat chisels and plane blades.

I've only recently started acquiring hand planes (I'm a power tool kind of guy), and I'm restoring several (a Stanley Bailey No.7, No. 6, No. 5, and Millers Falls #9 and #14).

The No 6 had a chip in the blade and I decided that this would be a good one to test out hollow grinding using the 8" wheel. I shortened the blade slightly using a 120 grit belt to remove the chip, then started sharpening using 120, 180, 220, 400, 600 (Trizec) and 1000 grit (aluminum oxide) belts. I used light pressure, never let the blade get hot, and dipped it in water every few seconds just to make sure.

My questions are:


Do I stop at 1000 grit (15 microns) or get some 2000 grit belts (6 microns)? Does it make much of a difference? With this equipment, I can either touch up on the grinder, or on a stone... not much difference to me. I also have leather belts that I can use on the grinder for power stropping.


Should I grind to 25 degrees and then set a secondary bevel to 30 degrees and use this as the honing surface?
Too many options make for lots of of potential questions, but this is a start. I beg your indulgence and opinions while I sort out what's best for my little shop.

Granted this is the neanderthal forum, and we are talking about hand planes. But I have some pretty non-neanderthal ways of sharpening!

http://www.stephenbader.com/assets/images/b3full.jpg

[Joel Moskowitz]

That grinder is a great gadget. Will it work - sure!!! is it optimal - not really.

With a regular grinder and wheel I can easily walk up to the grinder, turn it on, and grind to a hollow grind in 1- 2 minutes. THen another minute or two on a standing setup for waterstones and I am done.

Changing belts seems a lot slower. and using so many grits seems a lot slower. THis is a great grinder for shaping knives and tools but just for putting in a hollow grind it seems overkill and slower.

that all being said - you already have it so you might want to just try using a coarse belt to get to the wire edge and then go to stones. - unless you have to do a huge number of tools - then belt changing makes a little more sense.

[Alan Zenreich]

Changing belts is very quick. You simply press down on a lever on the left side of the machine to release the tension. It takes about 4 seconds to remove a belt, about 10 seconds to put a new one on.

Depending on the belt I chose, I could hog off metal at an incredible rate... I could have gotten a hollow grind in a few seconds :).

But I wanted to take it particularly slow with this first test.

Generally I leave the grinder set up with a 240 grit belt.

[Alan Zenreich]

Oh, and it's clearly overkill for the task. I'm not advocating this as folk's next purchase :)

The question is at what point to stop using the grinder (if any), and move to a stone for honing. Or do it all on the grinder.

Folk use one or two grits on their bench grinder because that's all the machine will handle, and changing wheels is not trivial. So, I could have used one or two belts to mimic what is done on the bench grinder, but I decided to go through more steps to a grit that most folk don't go to on a bench machine.

For touchups, it would take only a few moments to put the 15 micron belt on and ressurect the mirror finish.

I know there's no one right way to do this, so I'm soliciting opinions.

Thanks for the feedback so far.

[Wilbur Pan]

My questions are:


Do I stop at 1000 grit (15 microns) or get some 2000 grit belts (6 microns)? Does it make much of a difference? With this equipment, I can either touch up on the grinder, or on a stone... not much difference to me. I also have leather belts that I can use on the grinder for power stropping.


Should I grind to 25 degrees and then set a secondary bevel to 30 degrees and use this as the honing surface?


That is a cool looking tool. I've never seen anything like that before.

As to your questions:

Most people would advocate going to an 8000 grit waterstone or green rouge on a leather strop as your final stage of sharpening. Those methods have abrasive particles on the order of 0.5-1 microns, which is considerably finer than the 6 micron particles on your 2000 grit belt. I would keep a finer sharpening device of some sort after your 2000 grit belt.

As far as secondary bevels go, a lot of people like the 25/30 degree setup. Personally, I don't like secondary bevels, but that's just me. You can get excellent results either way.

[Derek Cohen]

Hi Alan

A belt sander is a wonderful machine for grinding steel. It definitely has a place in the list of options. I have not been using mine for some time, tending instead to use either a 10" Tormek or an 8" half-speed dry grinder (with a 3X 46 grit blue wheel). ... that 10" Monster in the thread earlier on is no more - it went to live with a machinist. (some changes in 18 months between posts).

I have come to hollow grind the primary bevel for all my plane blades, BU and BD, and of course chisels (including some Japanese ones, these on the Tormek). This facilitates easy freehand honing.

My belt sander can only produce a flat grind. I would use it for BU plane blades, since the secondary angles were (still are) added with a honing guide. Now it tends to gather dust. Still, it has a feature that you might wish to adapt to yours, a blade rest across the belts.

This is Mk I: http://www.woodworkforums.com/showthread.php?t=14908&page=1&pp=15

This is Mk II: http://www.woodworkforums.com/showthread.php?t=16156

In the beginning I used the belt sander as a complete sharpening machine. I had Trizec belts up to 2000 grit! The edge off this was amazing!! This could be followed with a powered strop (with green rouge), or just used to renew the edge.

The downside was that changing of belts takes time. After a while it took too much time. Eventually I only used either an 80 or 120 grit belt to create or renew a primary bevel, and then went to a honing guide (to create a micro secondary bevel) on waterstones for the rest. Much, much faster.

Regards from Perth

Derek

[Alan Zenreich]

Wilbur,

I like the idea of going down to the sub micron level.

I just ordered an assortment of PSA 3M Micro Abrasive sheets.

Let's see how that works for final honing. The sheets in the assortment are in 40, 15, 5, 1 and .3 microns. It will be interesting to see how scary sharp technique does as a finish for the belt grinder.

I'd really like to do a good job on these plane irons. I'm taking my time, weighing the options.

Thanks for the continued input.

[Alan Zenreich]

Derek,

Thanks for your reply. I'm using a TeknaTool Sharpening Centre as a tool rest, and will be modifying it to include a guide for plane irons (it already has a sliding guide for skews).

Actually, I have a few toolrest options, including making a jig to hold a Trend Diamond Honing guide.

For now, however, freehand on the TeknaTool platform seems to work fine.

I'll try to make a couple of photos soon to show the setup.

[Jim Koepke]

Alan,

That is a nice looking machine. My only thought is each time you change the belt and return the blade to the abrasive, you are taking a little more metal off the tool being ground.

I think the advantage of hollow grinding is it only takes a few strokes on fine stones to get to a sharp edge.

Think of it as the area of blade that has to be removed. With a hollow grind, just 0.010 inch at both ends of the bevel would be more than enough to be good to go and only be 0.010 square inches of metal polished on a half inch chisel. If one was doing a flat bevel on the same chisel at 30° it would be about 0.140 inches of metal area to be polished. (This was calculated using the area on one of my straight sided chisels.) This may not seem like much until one considers it is volume of metal being removed. Polishing through a thousandth of an inch of 0.010 square inches of metal will be a lot faster than polishing through a thousandth of an inch of 0.140 square inches of metal.

jim

[phil harold]

Question: what is the "ideal" diameter grinding wheel to create an optimum hollow grind on chisels and plane blades?
I was always told ten inch diameter was the best

So I have a big ten inch water wheel to do hollow grinding on

[David Keller NC]

"The question is at what point to stop using the grinder (if any), and move to a stone for honing. Or do it all on the grinder."

Alan - You're sure to get a bunch of opinions on this. What follows is just mine.

Generally speaking, you do not want to leave a hollow grind as the only edge on a plane or chisel blade - at least a hollow grind of 6"-8" radius or so. Even if you achieve a high polish and excellent sharpness solely on the grinder, the edge may be quite weak because it's considerably shallower than the overall measured bevel angle.

Generally speaking, you want the first 1/32nd or so (at least) of the edge to have a bevel of 30 degrees for the best wear/chip resistance. Anything shallower tends to either give and roll over (softer blades) or chip (harder blades).

I used to progress through hollow-grinding, then 1000, 4000, and 8000 grit water stones on the bevel before I figured out that was a tremendous waste of time and in some cases messed up the bevel geometry due to inconsistency in the various stone's flatness, or my inability to hold a consistent honing angle.

I figured out after a while that I could take the blade straight from a hollow grind directly to an 8000 grit waterstone. Because the hollow grind gives you a very narrow contact point at both the back and front of the blade, very, very little steel needs to be removed, and the resulting 1/32nd or so of polished metal at the front of the bevel after about 4 strokes on the waterstone is unbelievably sharp, so long as the back's been properly prepared to a flat, mirror polish.

You might wish to try this when you get your sub-micron paper - just go from a hollow grind with one of your 120 grit belts to the sub-micron paper. This assumes, of course, that you've polished the back, which generally cannot be done on a power-grinding/honing system to the necessary precision - it requires a series of grits in flat stones or sandpaper on a flat substrate.

[Danny Thompson]

I agree, this is old news. Derek and others have said for some time now that hollow grinding makes free-handing a breeze, and is the prefered method for BD blades.

Likewise, his advice about bevel-up blades should not get lost in this discussion. It remains the drum to march by--i.e., jigging produces the most desirable results for BU blades.