About as sharp as sharp gets

[not2sharp]

This is a classic microtome knife used in the preparation of tissue slides for microscopic analysis. Todays these have largely been replaced with more advanced technology. But, you may still find some of these in use in the field, or by less well equipped labs.

The modern Microtome


If anyone is curious about what kind of performance can be coached from a block of steel, then you should take a closer look at an old microtome. These are close to the definition of sharp. There are many countervailing properties that are desirable in a good knife; and, these are but at one extreme. Just be careful; these are traditionally among the most dangerous instruments found in the lab.

n2s

 

[tom19176]

a long ago X girlfriend of mine use one of those in a skin cancer unit in NYU Medical Center. She had given me a old set the glass stones and oil they used to sharpen them.....I did not do too well using them to sharpen a knife...

 

[not2sharp]

a long ago X girlfriend of mine use one of those in a skin cancer unit in NYU Medical Center. She had given me a old set the glass stones and oil they used to sharpen them.....I did not do too well using them to sharpen a knife...

Try a strop. In the old days you would strop them and then eventually send them back to the factory for reconditioning. They were very expensive instruments. My 1924 Spencer lense set, of two Microtome blades, probably sold for around $27 ($10-15 per blade + a few bucks for the handle and case - in 1924 dollars!) ~ nearly a month's pay for the average worker.

n2s

 

[dpimpc]

I think this is sharper... http://www.aip.org/png/2006/264.htm ...sure it's a needle, but technically it's pretty freakin sharp!

 

[HoB]

Well, I have sharpened several microtome blades and really there is nothing special about them (we are talking microtome, not ultra-microtome, which is really a different instrument all together). I have knives that are actually sharper than microtome blades. The reason is simply the steel and the geometry. Microtome blades have a resonably thick geometry because they are made to work at a specific angle. The steel, is very nice and fine grained as far as I can tell but it also feels pretty soft, which means it is not likely to support a very low angle geometry. Their edge finish is very high though as they are meant to be push cutters so on edge refinement they rate very high. However, there are blades that easily beat a factory sharpened microtome knife: Japanese woodworker hold cutting competions with their low-angle planes. The top competitors will cut sub-micron thick shavings of hardwood . Those planar blades approach pretty much the limit what you can get out of a steel edge.

 

[PB Wilson]

Those handmade Japanese plane irons are something else. Very hard edge steel (mid 60's hardness) with a softer iron back in an oak plane body sharpened up to 8000 grit. Amazing what a skilled woodworker can do with them.

Here's a pic I found online to demonstrate what can be done. Look at the size of the shaving and the width of the plane! I'm not sure of the wood they are planing, but it's impressive nonetheless.