Leroy Brown re Microtomes

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From:bbracing <bbracing@silk.net> (by way of histonet)
To:histonet <histonet@magicnet.net>
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Leroy   I also have a 330, a couple of 2040's and a couple of AO's all with
the low profile knife holders, and they all suffer from the same problem.
The holders are quite often damaged by the staff while cutting, or when
cleaning, as they will drop the parts as they disassemble/assemble the
holders, or they will "clunk" them on the table, edge down, or their
favorate, is to slide the carrage too far onto the base plate and drive it
into the chuck holder.  This always causes damage to the lower blade holder
face, and they wonder why they get thick and thin sections and/or chatter
the next day.  So I am forever dressing the face of the holders.  The
amount of material removed is extreamly small, and some of my microtomes
are 20 years old and the holders have been dressed more times than I care
to think but still work fine. The problem also exist with the high profile
blade holders but only manifests itself when the damage is sever.  This is
because high profile blades are very ridged, and if clamped in only one or
two places will not vibrate or deflect as easily, so the problem is not
The problem of the upper plate holder, not clamping the low profile blade
at anything but the upper most part of the blade is a problem that should
be solve by the manufacture. From what I have seen I don't think that these
holders are sold in matched sets, where the clamping pattern of each holder
has been check against a blade of known thickness. For example, if you have
a holder that will clamp a thin blade correctly, that is by the toe of the
upper plate holder, but it has insuficent heal to blade clearance, when
replace by a slightly thicker blade, will now be clamped by the heal of the
upper face plate, and the blade will now distort or vibrate when
sectoning.(Blades sold by different manufacturers all have a different
thickness)  I have clearanced all of my face plates so that when clamping a
blade (feather) there is a two too three degree clearance angle between the
the face of the blade and the heal of the clamping face plate. This has
solved all our problems with thick and thin sections, chatter and
washboard. Some holder do not require clearancing as they come with
sufficent clearance built into them that blade thickness is not a problem,
and they will always clamp the knife properly( except when damaged), others
do not, so it is a bit of a crap shoot, as to what you get.
Thanks for the note
Kerry Beebe
Kelowna Gen Hospital
Kelowna B.C.

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