I was reminded of plunge cutting with an end mill today...no pics...sorry

I had 2 pieces to make for a customer. 1" x 2" x 10" solid bar with a 3/4" x 3" slot (located on the 2" side, extending 1" deep and out the other side...did I explain that right???)

Anyway, I chain drilled 4 x 5/8" holes leaving 1/16" - 1/8" between the holes in both pieces to take out the worst of the metal.

I then proceeded to cut the slot by plunging with a 3/4" end mill about 0.200" and then cutting over the 3" required. Plunge another 0.200", cut back...repeat... The problem was I went through 3 end mills! Ran about 1000rpm (too fast???). I can't remember the feed, but I don't think it was excessive. (The mill has a 5hp motor.)

On the second one, I scratched my head a bit and decided to start with a 5/8" end mill and plunge cut the web remaining between the drilled holes. I then ran the full 1" deep cut to clean out the remaining metal. Switched to 11/16", (yeah, I was chicken...I only had a single 3/4" 2-flute end mill left!), and ran the slot full depth again. Then 3/4" and run the slot again.

Cut the time in half (including tool changes) and burned up 0 end mills using the second method vs 3 for the first run (2 cheap china 4-flutes & 1 USA-made roughing 4-flute cobalt).

What I learned:

1) I gotta remember this for next time...

2) I'm gonna hafta order some more 3/4" end mills too!

Andrew

I had 2 pieces to make for a customer. 1" x 2" x 10" solid bar with a 3/4" x 3" slot (located on the 2" side, extending 1" deep and out the other side...did I explain that right???)

Anyway, I chain drilled 4 x 5/8" holes leaving 1/16" - 1/8" between the holes in both pieces to take out the worst of the metal.

I then proceeded to cut the slot by plunging with a 3/4" end mill about 0.200" and then cutting over the 3" required. Plunge another 0.200", cut back...repeat... The problem was I went through 3 end mills! Ran about 1000rpm (too fast???). I can't remember the feed, but I don't think it was excessive. (The mill has a 5hp motor.)

On the second one, I scratched my head a bit and decided to start with a 5/8" end mill and plunge cut the web remaining between the drilled holes. I then ran the full 1" deep cut to clean out the remaining metal. Switched to 11/16", (yeah, I was chicken...I only had a single 3/4" 2-flute end mill left!), and ran the slot full depth again. Then 3/4" and run the slot again.

Cut the time in half (including tool changes) and burned up 0 end mills using the second method vs 3 for the first run (2 cheap china 4-flutes & 1 USA-made roughing 4-flute cobalt).

What I learned:

1) I gotta remember this for next time...

2) I'm gonna hafta order some more 3/4" end mills too!

Andrew

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