My straight router bit came in a little plastic box that has a hole that the shaft of the bit fits into.

The other half of the bit (i.e. with the two cutting edges) was covered in some transparent gel. From the way the gel looks it is obvious that the gel was applied in liquid form and then cured on/around the bit.

I suspect that this gel is there to seal the bit from air, especially moist air, to prevent corrosion. Please correct me if I'm wrong.

Does it make sense to reapply the gel when storing the bit?

I found many images of bits being stored without such gels in simple wooden boxes. Does it depend on the bit? Hardening steel changes its properties possibly making it more prone to corrosion. Does it depend on the material of the bit?

  • The "gel" is commonly called cosmoline.
    – rob
    Commented Apr 21, 2015 at 17:16
  • 1
    Oh, so that's cosmoline? I always wondered when i heard about the mythical surplus Jeeps packed in the stuff...
    – keshlam
    Commented May 16, 2015 at 5:26

4 Answers 4


The gel is something similar to Stripcoat (http://www.evanscoatings.com/). Prior to the bit being placed in individual packages, they can be bumped together. The hot melt coating on them keeps the edges intact during handling. Some of the coatings also have a layer of oil to protect against rust.

I have a few pounds of this stuff I keep in my shop for when I need to make a cover for a chisel or something that I want to protect the edge on. It is handy stuff that can be re-melted and reused several times. If you spend any time in a machine shop, you will see most finished parts dipped in this or something similar.

  • 4
    Good answer! The waxy "gel" is commonly called cosmoline. I've always thrown it away and hadn't thought of remelting it and reusing it.
    – rob
    Commented Apr 21, 2015 at 17:18

Don't worry about it- for most bits other than straight bits, you won't get the protective gel off without tearing it up anyway.

I keep those little packets of silica gel that seem to accompany many products today and throw one in any closed drawer or enclosed space. In my portable toolchest, I keep a piece of chalk or two, which also absorb moisture.

  • To add I have heard that silica gel can be restarted by drying them in an oven.
    – LosManos
    Commented Apr 22, 2015 at 13:36
  • Microwaving silica gel packets (carefully) is very effective at driving out the moisture so they can be restored to full strength. I found this YouTube video very instructive: youtube.com/watch?v=3twxGjGRE-A
    – scanny
    Commented Oct 18, 2016 at 23:50

Does it make sense to reapply the gel when storing the bit?

No. That gel is some sort of wax that protects the bit before sale. I guess it helps protect against corrosion (especially if the bit has a bearing), but it also prevents anyone handling the bit from being cut, and it prevents the bit from being chipped or broken if it happens to bump against other bits, fall on the floor, etc. The coating is not meant to be reused once removed.

When you're ready to use the bit for the first time, you should remove the coating. After that, keeping the bits clean and storing the bits in a dry place in a rack or in the container they came in should provide sufficient protection.


Couldn't hurt, but honestly I wouldn't bother. Anecdotal I know, but where I work we've never bothered and I've never known of any issues with corrosion on bits. It might be an idea if you have a particularly damp environment like a barn or something, and you think you're likely not to use a bit for a year or something, but overall I wouldn't worry about it.

Edit: I would recommend that if you WERE to replace the coating by using the original stuff, that you also apply oil to the bits. All of the bits I've ever seen that have come in this plastic coating have also been slightly oily so that's the assumption I was working on.

  • Actually, re-applying the coating could hurt if it happens to trap moisture inside. I agree that it's unlikely to be a problem, but the coating certainly isn't meant to be reused.
    – Caleb
    Commented May 16, 2015 at 17:42
  • You're right. Have updated.
    – WhatEvil
    Commented May 17, 2015 at 21:48

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