Thread: Wedge blade from microtome

Hi guys, some not every day advices needed

Microtome is device that is used to cut very thin pieces of tissue. That samples of tissue are then looked under a microscope (more info on wiki).

Recently I was given a blade from microtome (from veterinary lab) to sharpen it. Here are the pictures:









As you can se it is simply a over sized wedge razor. Dimensions: length: 21 cm, width: 1 cm and height around 3,5 cm.

Problem with a blade is that it is dull and cannot be resharpened by technicians in the lab.

It has uneven and too big secondary bevel. Back of the blade has 1 mm sori and flat primari bevels are not that really flat (on flat glass surface, they tilt a bit - around 0,25 mm).

I have some general idea what to do but If someone had similar case of repairing or knows more about this and it is willing to share it I would appreciate it very much, especially before I start removing large amounts of metal.

Thank you for reading.

Hi Karlo,

Try having a look here - an article from the Clinical Journal of Pathology. Might give you a few ideas.

Professor Roy Ellis also has a good reference manual - here.

Regards,
Neil

That is certainly a wedge and what an interesting article Neil. Much food for thought in that one. I had thought that fashioning a handle of sorts for the microtome would be step one but a fixture to maintain a correct angle never occurred to me. The problem of the fixture wearing more quickly than metal from the bevel necessitating the tungsten carbide feet is also so interesting.

The instruction to use circle honing was also surprising to me. No new thing under the sun apparently. Now, on SRP, we are going to see posts about guys taking abrasive powder and impregnating it into bronze lapping plates to polish their edges with corresponding photos at high res to show the glistening surfaces of their bevels .....

Best of luck on that Karlo, it seems to me a daunting task.

As Jim Says,a daunting task for sure.No help but for refferance most state of the art path labs have gone to disposables used in computor operated machines.
The blades are made by feather.

There are machines made to do it. Interesting things. The blade is run on a piece of glass or other hard,flat surface, charged with compounds. I have not seen one in action, but It would be interesting. I think you should be able to affix a handle and hone it, but the angle would have to be determined and the spine taped accordingly. Older ones, which look like straight razors, are flat on one side and concave on the other. Yours surely seems to be a simple wedge. Good Luck!

Thank you all for quick response and good luck.

Neil Miller, thank you for the article, those angles are one of the things what I was looking for.

JimmyHAD, I will definitely make some sort of handle for my own safety, after all one part of the process will probably involved fast rotating water stone so no need to risk flying oversize wedge razor.

pixelfixed, at the moment they are using those disposable blades but the woman operating machine said that they don't make nice and clear cut as the wedge one from the first post (of course - if it is correctly sharpened). some sort of lines from cutting are visible in the sample when looked under microscope. so she wants the wedge one as soon as possible.

I’m playing with a thought to make it fully flat with no secondary and then they can easily put on some secondary if the blade is chipping or similar.

In some 10 days I’ll post pictures of the oil stone they bought along with blade. It would be nice to hear your thoughts on that.

Hmm... Very interesting. Seeing the pictures of the blade, it made me think of another kind of honing. The katana sword. The technics used here most be almost the same, and you doesn't need a handle.

I've found this video of a master honer http://m.youtube.com/watch?feature=relmfu&v=kD3CuLRs5tQ

You are going to LOVE that microtome hone! Feel free to sneak a few of your straight razors on it, and report back to us how they shave!

I have some premade handle for santoku knives and the hole in them is 6 mm diameter and it is the same as that little tang from microtome blade so one drop of epoxy and handle is done. It looks like some japanese kitchen knife and feels like koshinata in the hand.



I did concave bevel on stone wheel (exposition was long so there is ten times less sparks in reality).



...and now it looks like this.



Now is time to lay it flat on some 180 grit and grind it to zero and then to some 1000 or so. After that I’ll use it’s original hone at 10 degrees per side.

I could have done that without stone wheel with just flat belt grinder but I think this is easier for maintaining it in future.

As they need really clear cuts I would do the last of the polishing of the edge along the edge, that's the way wood workers do it to get shiny cuts.

Edit; I would use lapping paper for the final polish.