TROUBLESHOOTING: Loose Knife Clamp Arm

Rolling the cryostat over bumpy cobblestone or tactile pavement can loosen the pins that hold the knife clamp arms. The microtome will probably look something like this:

Assuming everything was working just fine at the last job, all the parts should be rolling around somewhere at the bottom. Put the knife clamp arm back where it belongs. 

Now find the pin and insert it into the hole.

Use your heat sink to tap the pin all the way in. 

All fixed! 

The next time you need to go over bumpy pavement, ROLL THE CRYO SLOWLY. 

TROUBLESHOOTING: OCT mount falls off the disc

Sad mount misses his disc.

Sometimes, when you're making rough cuts or even just regular cuts, the OCT mount gets knocked off the disc. This can be caused by several things, the most common reason being:

-You took too much time putting the mount together.
Once you get the disc onto the cold bar, you need to apply OCT immediately, before the disc has a chance to get too cold. If you take too long, the pre-chilled disc will freeze the OCT before it has a chance to ooze into those tiny nooks, crannies, and holes.

You can preheat your discs on the hotplate to give yourself a few seconds leeway and some burned fingers.

The most reliable way to make sure your mounts stay on the disc is to touch the tip of the OCT bottle to one of the holes and give it a good squeeze to force the OCT into the hole.

In figure A, the OCT froze before getting into the holes, making it the type that's likely to fall off the disc. You want the OCT to freeze inside the holes as shown in B, C, or D.

Other reasons why your mounts are getting knocked off the discs:

-The surface of the disc needs to be roughed up. Refer to the post below. 
-There are loose screws.  Check the knife screws, blade screws, etc. Check everything!
-Your cryo has been off for several hours and is too warm to cut on.  The OCT block isn't frozen solid enough to hold on to the disc. Bend a Freeze-It straw so that you can freeze the backside of the disc as well as the front.
-Your rough cuts are too aggressive.  When you're advancing the wheel by hand (e.g. cutting through the safety layer), avoid cutting too deeply with each turn.

How to Rough Up Your Discs

Roughing up your discs provides extra grooves for the OCT to cling on to, hopefully preventing the OCT block from falling off when you're cutting sections. There are a few different types of discs that we work with:

Copper discs without holes: This type is excellent at gripping the OCT. Personally, I've never felt the need to rough these discs up, as they do a perfectly good job as they are. They DO, however, take more time to get cold.

Aluminum discs without holes: This type freezes quicker than the copper discs. The circular ridges seem to grip the OCT relatively well, but you might want to rough up the surface for added gripping power, just in case.

Aluminum discs with holes: These are the discs that give techs the most problems. I absolutely recommend roughing these up.



There are two ways to rough up a disc (plus one extra that I'll explain later but won't recommend):

Method #1 - Rub the surface of your disc against cement.  You'll probably find a suitable surface in a parking lot.

Method #2 - Use a screwdriver and your body weight.  This is my favorite method, since you can do it in the office and don't need to remember to do it on the way home. Place your disc ON A CARPETED FLOOR ONLY with your screwdriver at the center of the disc. Lean your body weight into it until the screwdriver slides down to the edge of the disc.  Turn the disc and repeat until you get several grooves radiating out from the center.

Method #3 - Garbage disposal. Obviously, I can't recommend putting your disc through a garbage disposal. I only discovered this method by accident. Ironically, it transformed a problem disc into one of the best discs I've ever worked with. Again, don't do this!