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Old June 20, 2018, 06:40 AM   #1
Hdonly
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4140 steel 80% 1911

Has anyone used a 3/32" end mill to cut the rails on a 4140 steel frame? I have done some milling over the years on my 3 in 1 mill/drill/lathe but never with this small of an endmill. HSS with flood cooling? Carbide dry? Or is a key way cutter the best way to go? My equipment is all manual.
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Old June 20, 2018, 09:21 AM   #2
BillM
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Keyway (Woodruff) would be the way I would do it. Cut both sides in one setup.
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Old June 20, 2018, 09:26 AM   #3
tango1niner
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I know your particular task but have never done it. Have done many like it... No clue as to the rigidity of the equipment you have but I personally I like the idea of the key seat cutter with coolant. Any size EM can pull to one side unless you are taking multiple light passes on one side at a time.
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Old June 20, 2018, 10:04 AM   #4
4V50 Gary
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Key cut it. Automatic feed set on slow with lubricant.
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Old June 20, 2018, 03:17 PM   #5
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Quote:
Keyway (Woodruff) would be the way I would do it.
Yep!
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Old June 20, 2018, 06:07 PM   #6
dakota.potts
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I would use a keyseat cutter but could probably be done with an endmill. Either way it will be key to have very accurate set up with regards to cutting the rails square and parallel with the rest of the frame.

Carbide is more rigid and resistant to heat but is less forgiving on making a nice finish if you're not pushing the speed. HSS is more forgiving in this regard but you'll have to be more careful with the heat. If you don't have a flood coolant system, I would use a heavy cutting oil like the Vipers Venom offered by PTG
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Old June 20, 2018, 07:03 PM   #7
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I have an older Shoptask 3 in 1 and a smaller tabletop milling machine. I was wanting to do it on the smaller machine, but I am limited to 1/4" collet. I have 3/32" endmills in 1/4" but I see mostly 1/2" shank key slot cutters. Guess I should do the job on the Shoptask with 1/2" x 3/32" key slot cutter. I have mist cooling setup, but it will flow pretty wet with the right settings. Thanks for all the good information.
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