[Histonet] cutting angle

Tue May 3 17:31:23 CDT 2005

Vinnie,

I agree with you.  We have several diferent vintage Leicas and the markings
for the "angle" are in fact reversed.  One reads 0-20 top to bottom the
other 20-0 top to bottom.  Like you I have told the microtomists to use the
angle which for them produces the best ribbon.  I have spoken to several
mictotome manufacturers over the years and they agree these marks do not
mark "angles" as such merely a guide to where you should set your knife.  We
have several Cryostats (different brands) and there is no consistency
amongst these either, two have no numbers on the knife angle guide.
As I have been a histotechnologist for over forty years and have cut many
sections in wax and other substances (including resin, celloidin etc) using
many types of knife (Ralph, Tungsten carbide, carbon steel and disposable) I
have found that for most conditions the "perfect angle is one where the
block only just clears the back of the knife.  Even using a sledge microtome
for the celloidin sections (whole lobes of lung and hemisheres of brain) the
same rule applies.

There is some great material written about knife clearance angles and the
facet angles of knives.  Baker and Silverton in Introduction to Medical
Laboratory Technology suggest 1-6 degress clearance.  Bancroft and Stevens
in Theory and Practice of Histological Techniques recommend a clearance
angle of 3-4 degrees.

When teaching students microtomy we begin by setting all the mictotomes at 7
on the scale then do minor adjustments according to the tissue being cut.
However, the choice of "angle" is the users if the sections come off the
knife well.

Bill Sinai
Laboratory Manager
Tissue Pathology, ICPMR
Westmead NSW 2145
Australia
Ph 02 9845 7774

-----Original Message-----
From: histonet-bounces <@t> lists.utsouthwestern.edu
[mailto:histonet-bounces <@t> lists.utsouthwestern.edu]On Behalf Of Vinnie
Della Speranza
Sent: Wednesday, 04 May 2005 7:22 AM
To: histonet <@t> lists.utsouthwestern.edu; godsgirlnow <@t> msn.com;
JWEEMS <@t> sjha.org
Subject: RE: [Histonet] cutting angle

Of course, Joyce's remark is right on target.

when I first saw your post Roxanne, I wasn't quite sure if I understood
entirely what you were asking.
for example, do you use the same blades in your new job as you used in the
previous lab? if the answer is yes, then it is very unlikely that the angles
used could be so different and both yield acceptable results.

the angle set on the microtome is directly related to the facet angle on the
blade and of course this can vary between manufacturers.

in essence, you must find the correct angle to a degree through trial and
error until your sections  have minimal compression. if the sections are
rolling off the blade smoothly and with little compression, you are at the
correct angle for that brand and model blade.

I am also not convinced that the angle setting between microtomes,
especially between different brands of microtomes, are all that precise.
what I mean is that if you used an angle of 10 on a Leica for example, you
might need an angle of 8 or 12 on a microm. I don't know what the actual
angle settings should be but you understand my point. even with a number of
microtomes from the same manufacturer I've seen it occasionally necessary
where the optimal setting on one might a  degree or two away from another. I
believe these settings are intended as general guides. the ultimate proof is
in the ease of sectioning and the quality of the sections you are getting
from a particular machine.

back to Joyce's remark. as long as you are able to attain the quality
required by your new employer, it matters little what angle setting you are
using.

Vinnie Della Speranza
Manager for Anatomic Pathology Services
Medical University of South Carolina
165 Ashley Avenue  Suite 309
Charleston, SC 29425
Ph: 843-792-6353
fax: 843-792-8974

>>> "Weems, Joyce" <JWEEMS <@t> sjha.org> 05/03/05 03:48PM >>>
I think you should be allowed to cut at whatever angle you produce the best
sections!
My 2 cents....Joyce:>)

-----Original Message-----
From: histonet-bounces <@t> lists.utsouthwestern.edu
[mailto:histonet-bounces <@t> lists.utsouthwestern.edu]On Behalf Of Roxanne
Soto
Sent: Tuesday, May 03, 2005 11:45 AM
To: histonet <@t> lists.utsouthwestern.edu
Subject: [Histonet] cutting angle

What angles does everyone out there cut at and what kind of blades do you
use?  I have always cut at 10 with high or low profile blades, but I have
recently changed jobs and they cut at an angle of 21.  They were told that
with high profile blades they should use an angle of 21.  I am having a hard
time cutting at this angle.......
any thoughts?
Roxanne

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