Are microbevels necessary for bench chisels when you have a Tormek?

[Mooney755FM]

Hello,
I'm new to woodworking and I've been working on my chisel sharpening skills with the Tormek.  Question - is the primary reason people use a microbevel - they do not have to sharpen the entire face of the chisel?  Is it to save time?  I have read many threads on this topic and I do not agree that it preserve's the lifespan of the chisel - I only see it as a way to reduce the sharpening time - this becomes unnecessary with a Tormek - because it's so fast.  I've also read that it strengthens the cut of the chisel, but again I don't agree with that reasoning either.  What am I missing?

Curious to know what others do, thanks!
Tracy

[Ken S]

Welcome to the forum, Tracy.

The short answer is, No, micro bevels are not necessary with a Tormek. Microbevels are useful expedients for bench stone sharpeners. The idea is that you grind the entire bevel once and do touch up sharpenings with only a small fraction of the bevel. That is a good consideration for hand sharpening, but not necessary with the Tormek; the Tormek does the work. The other consideration is heat with the grinder. The thinner the edge, the less metal is present is present to draw away the heat. In other words, the closer you come to doing the whole sharpening with the grinder, the greater the danger of overheating the blade. Stopping just short of completion and finishing by hand lessens the overheating danger. Again, this is not necessary with the water cooled Tormek.

As to a microbevel strengthing the edge, this also is not necessary. If you want to end up with a 28° or 30° bevel, do not start at 25°. Set your imitial grinding angle where you want your final angle to be.

Related to this is a longstanding "hollow grinding" argument. This goes way back to when the standard home grinder was a six inch diameter dry grinder. (probably worn to nearer five inches). At that diameter, the hollow grind is obvious. With a ten or eight inch wheel, the hollow grind is more of a theoretical than practical issue.

Start sharpening. Your chisels will let you know if you need to adjust your bevel angle. There is no "Thus saith the Lord" correct angle.

Keep posting!

Ken

[cbwx34]

One thing I tell others in knife sharpening... the beauty of sharpening your own knives is, you get to experiment... and find what works best for you.

[RichColvin]

Tracy,

The answer is, for the most part, microbevels are very highly recommended. 

The reason is this:

• The ground surface (the primary bevel) is quite large on a chisel (in relative terms)  This can be done quickly on a Tormek with the SG or SB grindstone, but the edge produced by that will not be sharp enough for most chisel uses (e.g., bench and paring chisels).
• Sharpening to the needed sharpness requires use of a stone that is 4,000+ grit.
• If you try to take the primary bevel angle sharp using a 4,000 grit stone, you will be grinding for quite a while!  (This is far worse if you finish the sharpening on a 12,000+ stone.)  The microbevel makes that activity faster as you are only grinding a small surface area to make the microbevel.
• When resharpening, you only need to update the micro bevel, not the entire surface.
• After a certain number of times resharpening of the microbevel, even that will start taking too much time.  That is because you are increasing the surface area of the microbevel each time you grind it.  When it starts taking too long (usually around the 5th or 6th time), that's when you go back to regrind the primary bevel and add a new microbevel.

Now, there are exceptions to the need for microbevels.  These include corner and scraping chisels. 

You can see pictures and more information at www.SharpeningHandbook.info.  Hope that helps.

Kind regards,
Rich

[Ken S]

Rich,

I do not doubt the sharpening expertise of your sources. Their advice is orthodox bench stone sharpening. I don't detect any Tormek familiarity in their opinions.

Fortunately we have the words of the foremost Tormek authority, Torgny Jansson, inventor of the Tormek and author of the handbook. Creating a secondary bevel would have been a simple matter of raising the support bar slightly, either by feel or by the microadjust. Torgny insisted that it was not necessary with the Tormek.

For thirty years, the SG -250 was THE Tormek wheel. I don't recall complaints about dull chisels post Tormek sharpening. The SG has a grit range of 220 to 1000 with the stone grader. This was followed up with the leather honing wheel with honing  compound. The SG-250 preceeded the 4000 grit SJ-250 by thirty years.

We have always had posters who preferred to finish with bench stones rather than the leather honing wheel. I may be wrong, however, I always questioned if these posters had really mastered the leather honing wheel.

The 4000 grit wheel is designed to polish an already sharp edge. It removes scratches left by coarser grinding wheels. It is not designed to remove metal as a sharpening wheel does.

I used micro bevels for years when I sharpened with water stones. The technique worked well for me. When I switched to the Tormek, I left the micro bevels behind. I suggest you do the same.

Ken

[RichColvin]

Ken,

I don't use bench stones for the microbevel.  Rather, I use the SJ stone on my Tormek.  I haven't found the need to go beyond the 4,000 grit.  I find it works really well, and like how fast I can touch up the edge.

Rich

[cbwx34]

I rest my case!   

[Ken S]

Touché, CB.

Rich, you have found a practical method which works for you. There are certainly many ways to successfully use the Tormek. For someone just beginning with the Tormek, I would suggest carefully following the techniques recommended in the handbook. They will get you up and running with a well proven technique. That technique may or may not be what you choose to use most of the time. It will give you a starting point of reference. Do not be afraid to underline, highlight, or make notes in your handbook. Use it as your personal reference.

Ken