Leica EM KMR2 User manual

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Leica EM KMR2Leica EM KMR2
Leica EM KMR2Leica EM KMR2
Leica EM KMR2
Operating ManualOperating Manual
Operating ManualOperating Manual
Operating Manual
Order Number 177032
Leica EM KMR2 - GA-E-06/03

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Table of contents
1. Safety instructions
2. Principles of knifemaking
2.1 The Balanced Break method
2.2 Scoring and breaking principles
2.3 The real knife angle
2.4 Length of useful edge
3. Unpacking and installation
3.1 Unpacking
3.2 Packing list
3.3 Installation
4. Description of the LEICA EM KMR2
5. Knifemaking
5.1 Hints
5.2 Making squares
5.3 Making knives from a square
5.4 Evaluation of the knife edge
6. Customised adjustments
6.1 Knife shoulder fine adjustment
7. Care and maintainance
7.1 Replacement of the scoring wheel
7.2 Adjusting the scoring pressure
8. Mounting troughs (‘Trufs’) onto the knife
9. Accessories and consumables
10. Technical specifications

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1. Safety instructions
Prior to the operation of the Leica EM KMR2 read the instruction manual carefully.
Always use safety goggles during operation to avoid eye injury.
Clean the instrument regularly with a brush to remove glass splinters.
Store broken knives safely in the knife boxes provided.
Do not leave knives laying around or on the Leica EM KMR 2.
Used knives should be put into a marked “sharps” box for safe disposal.
Symbols in this manual and their meaning
Warning:
take extra care.
Notes:
Important information for the user.

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Fig.1
Fig.2
Breaking pins
Fig.3
Knife edge
Counterpiece/
Knife shoulder
Counterpiece/
Knife shoulder
Knife edge
Fig.3a

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2. Principles of Knifemaking
2.1 The Balanced Break method (Fig.1)
In the balanced break method, an original Leica glass strip 400mm in length
(6.4, 8 or 10mm thick), is scored and broken into two equal halves, each 200mm long.
With an equal mass of glass on each side of the score the break is balanced and the
freshly fractured surfaces are plane.
By continuing to divide each piece produced into two equal halves, up to 16 squares
can be made.
All squares produced have straight sides and precise right angled corners
unlike squares produced from sequential breaking of a glass strip which have curved
surfaces.
2.2 Scoring and breaking principles
Producing good glass knives routinely depends on a supply of reproducible squares, an
accurately positioned score and controlled pressure precisely applied to make the break.
The LEICA EM KMR2 gives the user a choice of two different scores, each one factory set
to produce the optimum break.
The long score is used to break squares out of glass strips as well as to score squares to
break knives. As a general rule, the knife edge is straighter and the counterpiece (knife
shoulder) is small when the fracture occurs close to the corner.
The short score was suggested for cryo knives as the free break is longer resulting in the
sharpest, longest useable knife edge (Griffiths et al 1983: Tokuyasu 1986).
Each score is preset and equidistant from the corners of the square.
During the break the glass sits on two breaking pins and is also held from above by
two more pins (Fig.2).
Both lower pins are fixed and one of the upper pins is fixed too, the other can be moved up
and down by means of the breaking lever and actually initiates the breaking of the glass.
The break follows the score line as far as it goes and then a free break occurs. The
direction of this free break is determined by the mass of the glass on either side of the
break and the breaking forces.
The free break curves to the edge of the square resulting in one knife and one flat-edge
counterpiece (knife shoulder) opposite the knife edge Fig.3.
When the score runs centrally through a square a very small counterpice (< 0.2mm) is
obtained and the knife angle is very close to 45° (Fig.3a).
This is the optimal result for cryo knives. For resin sectioning we set the knife
shoulder a little larger (approx. 1mm), to produce a larger knife angle which is
more stable for resin sectioning.

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Fig.4
Scoring angle
Real knife angle
Fig.5
Stress line

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2.3 The real knife angle
When scoring the square all scores stop some distance from the corner.
When pressure is applied under the score, the fracture is initiated and is seen first as a
deepening of the score. The fracture extends towards the corners of the square
following the line of the score. Where the score ends and the break is ”free” the
fracture deviates from the line of the score to curve away from the corner, towards one
of the edges of the square.This results in the real included angle of the knife being
somewhat greater than the angle of scoring.
The real angle of the knife increases as the score is moved further from the diagonal.
This is when the knife shoulder becomes larger.
For example, when preparing knives from a square, the real angle of the knife is close to
45° when the knife shoulder is smaller then 0.2mm.
Increasing the height of the knife shoulder (> 0.2mm) results in an even larger
knife angle which can be over 55° (Fig. 4).
2.4 Length of useful edge
When a glass knife edge is examined under darkfield illumination using a stereo
microscope (or on LEICA Ultramicrotomes using the back light, chapter 5.4), it can be
seen that the central part is most useful for ultrathin sectioning. The right side of the edge
has visible marks (saw teeth) which reduce the quality of the knife, and the left corner is
also unsuitable for sectioning because of the stress line (Fig.5).
The useful knife edge starts where the stress line does not touch the edge until the part
where the stress marks (saw teeth) can be seen.
Note:
The useful knife edge is 30% longer on knives produced
from 8mm thick glass compared to 6.4mm thick glass!
Note:
When less force has been used to break the knife the
stress line falls away rapidly from the knife edge and fewer
saw teeth can be seen.

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Fig.6
Fig.7
Fig.8 Side view Fig.8