another 80% question

[fortdick]

Getting ready to finish off a lower paperweight and wanted to know if a 5/16 end mill will work or must I use a 3/8? I ask, because the trigger slot is 5/16 on the schematics for the lower and need to know if I need two different end mills.

Thanks

[yari]

It depends on the length of cut, finding a 5/16 with a long enough loc Is the problem. Rigidity is also a concern. Best to buy the 3/8 and go by the book.

[fortdick]

I am not being cheap and am quite willing to buy a second end mill, but is there any reason why the trigger slot can't be 3/8 instead of 5/16? I find a lot of 5/16 end mills have a 3/8 shank and that isn't good for following the jig.

[yari]

Wasn't implying you were being cheap, you can make the slot whatever size you want. I haven't used a jig in years so I cant remember the dimensions, I do remember using cheap harbor freight endmills, pretty sure they had 3/8 shanks and worked with the TM jig.

[Drew Eckhardt]

Getting ready to finish off a lower paperweight and wanted to know if a 5/16 end mill will work or must I use a 3/8? I ask, because the trigger slot is 5/16 on the schematics for the lower and need to know if I need two different end mills.

Thanks

1) The fire control pocket is 1.250 +/- .010" deep. As yari noted that may be a problem with 5/16" end-mills (mine has 1" flutes).

2) The drawings call for a .218" radius in the vertical corners which matches a 7/16" end-mill. A maximum radius of .030" is allowed horizontally. A 3/8" end-mill is 70% stiffer than a 5/16 and 7/16" 170% stiffer which should make a better surface finish.

I find a lot of 5/16 end mills have a 3/8 shank and that isn't good for following the jig.

3/8" shanks are common. All my end mills under 1/2" have 3/8" shanks except for a cheap 1/4" Chinese solid carbide mill.

[fortdick]

Thanks for the advice.

okay, so a 7/16 end mill is best? I want to get the right stuff before I start this. Also, I saw some high helix end mills for aluminum. 45 degrees and what not. Are these, or coatings of any use or just a waste of money?

[Drew Eckhardt]

Thanks for the advice.

okay, so a 7/16 end mill is best?

If it will work with your milling setup. I'm guessing (I use a vertical mill where I can navigate by coordinates and don't need a jig) that most jigs have you run the lower around an end-mill with the shaft rubbing on a cut-out shape and size top plate.

A 7/16" end-mill with a 7/16" shaft would work great in that situation, but may not be common.

A 7/16" end-mill with a 3/8" shaft will not because the flutes extend 1/32" beyond the shaft. I'd expect this configuration which probably won't work for your setup.

I want to get the right stuff before I start this. Also, I saw some high helix end mills for aluminum. 45 degrees and what not. Are these, or coatings of any use or just a waste of money?

30 degrees works great.

High speed steel works great.

Center-cutting 2-flute mills will plunge straight down to the bottom.

[slosurfer]

Are you using a TM jig? If so, they call for the 5/16" w/ 3/8" shank because the jig opening is 3/8". If you use a 5/16" shank, then you will have to center the 5/16" in the 3/8" opening, using the 3/8" shank makes it really easy on the TM jig.

[fortdick]

I appreciate the input. Y'all have cleared up many of the questions I had. Thanks again

[paratroop]

Just to add for any new guys, you dont really need a jig for the trigger hole. I have always eyeballed it and drilled two 5/16 holes, then cleaned up the sides with a dremel and file. Sure, I never got it perfect, but once the trigger is in place, you would never know. If the jig I bought several years ago had that feature, I probably wouldn't have done it my way, but just so you know.