Frequently Asked Questions
- Advantages in the application of disposable blades over conventional knives:
- Substantial cost reduction
- Consistent section reproducibility
- Consistent section quality
- Support of all common microtome systems
- For all paraffin embedded samples
- For all cryosectioning applications
- Expensive resharpening no longer required
- No longer dependent on quality of selected resharpening service
- No downtime while knives are at the resharpening service
- Standard re-usable steel knives and disposable blades in comparison with standard microtome blades: In typical histology laboratories, 50-100 blocks on average per day and person will be handled. Depending on the type of specimen and the way of trimming, up to 50 specimens and more can be worked on. Assuming the laboratory is handling all the different types of tissues that are typically processed in a histopathologyl lab, up to 20 blocks can be cut with high quality microtome blades retaining the same sectioning quality.
- Conventional steel knife 16 cm c-profile: As a rule, no more than 80 to 100 blocks will be cut by a steel knife with consistent section quality. Thereafter, the steel knife has to be sharpened regularly to regain the required knife performance. Due to the design of microtome knife holders, only 70% to 80% of the total knife edge can be utilized for cutting. The remaining 20% to 30% are not accessible because of the clamping principle commonly used.
Spring balance system is not calibrated: Set the hand-wheel to the 3 o'clock position and let it sit. If the wheel drifts upward or downward then the spring system is not balanced and requires adjustment. If the hand-wheel does not drift, then no adjustment is necessary. If adjustment is necessary, the user can balance the unit by adjusting a flathead screw, which is accessible through the hole on the underside of the microtome base plate. Removal of the section waste tray is necessary. If the specimen head slightly rises, turn the screw counter-clockwise completing 2 or 3 full rotations.
- Check the specimen advance (micrometer) setting to be certain that it is set correctly.
- Activate the coarse specimen advance to confirm that the specimen head is advancing.
- Select trim setting (e.g. 20µm) and try sectioning.
- Check that the knife holder is firmly clamped.
- If all the above fail – call Technical Service.
- Linear bearings have moved in cage and are at their lower limits: Linear bearings need to be cleaned, exchanged, possibly re-greased.
- Alignment of bearing cage is incorrect: Open a service call.
- Retraction "ON" causes louder clunking sound: Turn the retraction off by turning flathead in back of the microtome.
- The specimen might not be cold enough: Cool the specimen again and/or select a lower temperature in your cooling device.
- The specimen surface is rather large: Trim the specimen parallel and increase the section thickness.
- The knife clearance angle is not correctly adjusted: Select an appropriate clearance angle.
- You might use a dull blade: Please use another area of the blade or a new blade.
- There might be too much paraffin: Clean the knife with a swab moistened with xylene. Stroke the swab in an upward motion away from the blade edge, not down on the blade edge.
- The pressure plate is dirty: Clean plate with a non-solvent containing cleaning reagent.
- The coating of the pressure plate is damaged: After the usage of xylene for a long time for cleaning the pressure plate, the coating is removed. Please replace the front pressure plate.
- Static: Spray static solution, increase humidity; ground the instrument.
- Leica RM2125, Leica RM2235, Leica RM2245
- Specimen orientation
- Knife holder base with lateral displacement function
- Knife holder E, N, NZ
- Reusable knife or disposable steel blades
- Universal cassette clamp or standard specimen clamp
- Optional accessories: illumination, magnifier, section waste tray, hand rest
The specimen is too cold: Warm up the specimen.
- The tissue might be incompletely dehydrated and/or poorly infiltrated: If possible, try re-embed the sample.
- The tissue has remained too long in the paraffin bath or the paraffin bath was too hot: In this case, the damage caused to the sample is irreversible.
- The tissue is too hard for the type of embedding wax that has been selected: If possible, try re-embed the sample.
- Paraffin might have accumulated at the rear of the back plate of the disposable blade holder or on the front or back of the knife edge: Please remove paraffin debris regularly from the pressure plate. Clean knife with a cloth moistened with xylene. Do not use xylene to clean any other microtome parts - use solvent free cleaning reagents, such as Paraguard. Stroke the cloth in an upward motion away from the blade edge, not down on the blade edge. Try to move blade or replace.
TIP: Use a wooden stick or a Q-tip and run it across the blade once and check again.
- Hard particles (calcium fragments, bone splinters, foreign matter) in the specimen or embedding medium: Please filter paraffin. Decalcify, disilicate, thoroughly wash out remainders of crystal.
- There might be nicks in the cutting edge of the knife or blade: Move to a new area of the knife or blade and observe if scratches move with it. If so, replace the knife or have the knife sharpened. Possibly there is a staple or a thread left in the sample. Remove the debris and use another area of the knife/blade.
- The clearance angle is too big: Clearance angle adjustment; systematically decrease the clearance angle until the optimum adjustment is obtained.
- A damage to the pressure plate exists (bent/nicked): Replace the pressure plate.
- An insufficient clamping of the blade, the knife holder, the specimen and/or the orientation might cause this problem. Please check the clamping points and repeat the clamping of levers and screws of the specimen and knife holder system. Check the front pressure plate for wear. If the round on the lever is worn, then replace the lever.
- You might use incompatible blades. The blade is possibly too thin, causing flex if the specimen is too hard: Try using a different brand or grade of blades.
- The high profile knife may be too thick: Try using a different brand or grade of blades.
- Wax is built-up on the back of the front pressure plate: Remove and clean the rear of the pressure plate.
- It might be an application issue, not a microtome problem: Infiltration, dehydration, decalcification, paraffin is too old, paraffin impurities.
- It might be a problem of the tabletop stability: Move the microtome or table to a more stable location, or replace table if table is flimsy.
- There might be vibrations in the specimen advance system: Check if orientation has been changed or incorrectly assembled. Re-install all parts, if necessary.
- There might be a too high sectioning speed: Decrease the speed.
- The edges of the block are not parallel: Please trim the block edges to be parallel.
- The block is not parallel to the knife edge: Align the block to the knife edge.
- There might be irregularities in the knife edge: Change to another area of the blade or use a new blade .
- The knife or blade edge has not been completely changed over the full length of the specimen: Please trim the block edges to be parallel.
- Insufficient clamping of the blade, the knife holder, the specimen and/or the orientation might cause this problem: Please check if all levers are locked and screws are tightened.
Cassette related problems?
Underfilling of the cassette body, overfilling (excess of paraffin on the outside of the cassette has to be removed prior to clamping. Wrong clamping system chosen: standard clamp instead of cassette clamp compresses weak cassettes.
- Locking levers are not well lubricated or cleaned, causing them not to be completely fastened or stuck in a non-locked position: Remove all locking levers, clean off all paraffin and debris, apply a sparing amount of the provided Leica lubricant. Use only manufacturer recommended lubricants.
- You might use a blunt cutting edge: Please use a new blade or adjust the knife holder laterally.
- The pressure plate is damaged or not correctly adjusted (applies only to the knife holder E for the RM2100 series): Insert a new pressure plate or use a new knife holder. Re-adjust the pressure plate.
- The specimen block is too large or too hard: If possible, trim the specimen. Soften the block by soaking it in iced water. Try knife with a different profile (d-profile instead of c-profile).
- There might be excess of oil on the blade: Remove the oil with soft paper towel or Q-tip.
- You might use a dull blade/knife: Please use another area of the cutting edge or a new blade/knife.
- The specimen might be too warm: Please cool the specimen prior to sectioning by using a cold plate, iced water or ice cubes.
- The sectioning speed might be too high: Please work at a slower sectioning speed.Thin sections require a slow cutting speed.
- The clearance angle is too high: Lower systematically the clearance angle.
- The clearance angle of the knife or blade is too small: Systematically change to higher clearance angle.
- The knife edge or back of rear plate of the disposable blade holder might be contaminated with paraffin: Please clean both with a smooth cloth moistened with a non-solvent containing cleaning reagent such as Paraguard. Stroke the cloth in an upward motion away from the blade edge, not down towards the blade edge.
- Choose a value of retraction.
- The front pressure plate of the knife holder is not clamping properly (applies only to the knife holder E of the RM2100 series) -> leaf springs on the inside of the front pressure plate might be worn: Replace the leaf spring. Replace the locking lever (a Technical Service call is required).
- The blade cutting edge is not parallel with the pressure plate (applies only to the knife holder of the RM2100 series): Adjust the pressure plate with set screws at bottom of knife holder. Turn the screws until the blade is parallel to the top of the pressure plate. When the blade is parallel with the pressure plate, the base line of the blade should line up with the top of the pressure plate after being clamped.
- The sectioning speed is too high: Please lower the sectioning speed.
- The sectioning thickness is too high: Please lower the thickness.
- The clearance angle is too wide: Please try systematically to reduce the clearance angle settings until an optimum clearance angle has been found.
- The clamping of the specimen or knife holder might be insufficient: Please check all screws and clamping mechanisms at the specimen holder system and knife holder and retighten, if necessary.
- The type of knife is inappropriate: Try and use a more stable knife (e.g. d-profile knife).
- The material to be sectioned might be too hard: Please soften the block by soaking it in iced water or softening agent.
- Static electricity charge may be built up on the knife holder or the specimen head: Adjust temperature or humidity level in the room. Use an ionizer to neutralize the static charge. Clean components of the microtome with alcohol. Check to see if retract is turned on or off.
- Adjustment of the retract value may be needed: Increase the retract value to a maximum of 50 microns. If you like to rock, then use rocking mode.