If you are doing a Polymer80 pistol build, they recommend using an end mill to remove the top tabs and/or cut out the barrel block they cast in the barrel channel of the frame.  They used to include end mills and I always wished they were a tad longer to help remove the barrel block.  I used nippers, files and sand paper to remove the top tabs but I did like using an end mill to slowly remove the barrel block.

Because I like Polymer80 pistol frames and knew that a slightly longer end mill would help people using a drill press, I sourced these specialized end mills to help and let me explain the features:

• 9mm (0.393") diameter is ideal for the channel work and is the same diameter of end mill that Polymer80 used to provide.
• The overall length of the end mill is 95mm (3.74") and can make it easier to reach down into the barrel channel with a drill press with a big spindle.
• The end mill is a four flute design to enable a smooth surface cut.  Normally you use 3 mill end flutes for the finish machining plastic but since the Polymer80 frame work is very light, I opted for four flutes.
• It has a square head with a center cutting design which means you can do plunge cuts as well as sidways cuts with the mill.
• It's made from HSS-A1 steel - W6Mo5Cr4V2Al to be exact - and will hold up just fine for doing these frames

When using an end mill, please understand they are not the same as drill bits.  The work piece needs to be secure and you remove a little bit of material at a time or your frame is going really want to jump all over the place.

The price is per end mill and includes a plastic storage case for each.