I too was wondering if what is really happening is just the lengthening of
the facets that occurs with continued sharpening, at the same angle, using
any knife sharpener. As Alan states the only way to prevent this is to use a
commercial sharpening service that has the equipment to reface the knife and
thus shorten the facets. With knives used for paraffin sectioning I've
always found that lengthened facets, within reason, do not cause problems.
However, for cryosectioning I always prefer to have as short a facet as
possible especially if using an anti-roll plate. Therefore, I have always
send cryostat knives for commercial sharpening, refacing to keep the facets
short even though this may shorten the useful like of the knife since it is
subjected to more grinding at each sharpening.

John E. Tarpley 5-1-A
Associate Scientist
Amgen Inc.
One Amgen Center Drive
Thousand Oaks, CA 91320 
These Opinions are my own and not necessarily those of my employer. 
--snip snip--

Please note that in time the facets get very large this can cause a problem
for removal of cryosections, and the edge is not as durable causing more
frequent sharpening. This can be over come by having the faces of the knife
reground ( refaced) this then will virtually bring the knife back to its
original condition when new, at a fraction of the cost of a new knife.

We can or alternatively Hacker Instrument or other knife sharpening services
may be able to carry out this regrind for you, it cannot be achieved on an
automatic knife sharpener.

Please come back to me if all is not clear.

Best Regards

Alan Bright

Bright Instrument Co.Ltd.
St Margaret's Way
Huntingdon
Cambridgeshire
PE29 6EU
England

Tel No:+44 (0)1480 454528
Fax No:+44 (0)1480 456031
Email: AlanBright@brightinstruments.com
Web Site: www.brightinstruments.com




-----Original Message-----
From: Marc Slotemaker [mailto:mslotemaker@yahoo.com]
Sent: 13 February 2001 16:14
To: histonet@pathology.swmed.edu
Subject: knife sharpening


Hello everybody,

I have a question about knife sharpening. It's a basic
question since we just started into histology. We have
our knives sharpened automatically, and the person who
is doing this for us increases the knife angle each
time time the knife is sharpened, for instance from 35
to 35.25 degrees. Other people say this is rather
strange and the angle should remain constant while
sharpening. Also, what exactly is this angle? is it
the total angle between the two facets of the knife?
thanks in advance

Marc Kropholler

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