AO 820 knife holder question

[Fred F]

I posted this to micoscope@groups.io but hope to widen the search.
Greetings:
I found another rabbithole to ponder.
From D. A Johansen Plant Microtechnique 1940 page 122-123 he states that the AO 860 sledge microtome is to be used for harder specimens but then goes on to state that the AO 820 had a special knife holder that was similar to the variable angle knife holder on the AO 860. Since I have a rotary AO820 and have some projects that would be better addressed with the AO860 I am interested to learn more about a variable angle knife holder for the AO 820.
Reviewing the AO 820 Rotary Microtome brochure from 3/75 shows various knife holders but had none that allowed variable knife angle setup at the time of publication.
Granted the reference is 80 years old but I am curious as to whether anyone has any information (and/or examples) about the various knife holders for the AO820.
thanks for any pertinent information you might have to offer in this quest.
The eBay AO820 has been yet another vertical learning curve in order to produce 5u ribbons consistently but progress is being made.

fred

[apochronaut]

I recommend you go to Steve Neeley's site and look in the AO Blue Book. In the section on the 820, which is 4 pages with 5 photos, there is mention that " the knife may be tilted through an exceptionally wide range of cutting angles ". My copy is from 1946, pges. 100 to 103.
https://user.xmission.com/~psneeley/Per ... oscope.htm

[wabutter]

One other aspect to keep in mind is the type of knife that is employed. Typically the 820 used a C' profile knife for cutting paraffin embedded samples. When harder materials were cut such as bone or plastic embedded materials oft times a D' profile know was used. The C' profile used beveled edges on both sides of the edge where as a D' profile used a single beveled edge. Knife angle presented to the sample is adjusted accordingly. The standard 820 knife holder can support either type of knife. BTW, this would be true on the 860 as well, although a slip angle can also be adjusted on the 860 knife holder .