Milling a groove

[ironwrx]

Hi. I have to mill 3 grooves in mild steel. I am using a two flute hss end mill 1-5/16” diameter with a 1” shank. I’ve got to use my Kerney-Trecker horizontal mill and the work will be held in a heavy 90° angle fixture with machine vice tipped up perpendicular to the mill table. I’m planning on milling approximately 262 rpm. Basically I am milling a round-bottomed groove which has a width of cut of 1-5/16”, and a depth of 21/32”. Two of the pieces I have to do this to are 1” square bar, the third is 2” square.
My question is this; as far as I can tell, there would be 3 ways to do this - #1, to use the edge (perimeter of the milling cutter),to mill with a side milling motion. #2 - to end mill cutting the whole groove at once by plunging. Or #3 to end mill (plunge cut) across the 1” or 2” bar a little bit at a time (not full width of cut at once like #2). What would be the best way to do this operation?
I realize that my drawing numbers were incorrect. Fortunately, you commenters were reading my text, and ignored that error. Here is the corrected drawing.

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[mmcmdl]

#3 . It would also be easy to set a boring head to your diameter and step plunge to depth . I would go with a 4 flute EM if you have one also .

 

[ChazzC]

#3 . It would also be easy to set a boring head to your diameter and step plunge to depth . I would go with a 4 flute EM if you have one also .

100%: I have done this with a vertical mill several times, although in Aluminum:


These "channels" were reliefs with spot-faces to clear washers & SHCS in a 2-1/2" x 2-1/2" (outside) 6061 Angle, using a 3/8" x 2-1/2" CL (4-1/4" OAL) 4-flute end mill; the length necessitated small DOC to prevent deflection.

 

[tjb]

I agree with #3. One possible modification you might want to consider is to start by using a smaller diameter four flute end mill for the initial passes. If you have one - say a 1" or up to a 1-1/4". The roughing passes may allow for a smoother finish on the final couple of passes with the 1-5/16". I tend to think using the two flute end mill on every pass may be pretty aggressive.

Regards

 

[ironwrx]

Thanks for the helpful suggestions. I definitely agree with the general consensus of using #3 plunge milling with step advancement for depth of cut. I also decided to cut a vee out with my roll-in saw to reduce the amount of material that had to be removed. Fortunately a nearby machinist friend happened to have a 1” welden by R-8 mill adapter, so I will be able to use my BP after all. I’ll post pics with progress.


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[brino]

I'd also consider starting with a bigger block, drilling most of the hole and then splitting it and finish with the boring head or end-mill.
If you have a suitable bandsaw......

Brian

 

[ChazzC]

I forgot about this project (finished the project & submitted article in February 2022, published Jul-Aug 2023), which is actually more applicable:


1-1/4" 6-flute x 2" CL (4-1/4" OAL) x 3/4" Shank, 6-flute knob that sleeved over a plain knob (easier than re-creating the funky partial circular groove & detents in the back of the original knob)

The plunge cuts were in three passes:

1st Pass


2nd Pass


Finished knob over existing plain knob

 

[ironwrx]

Success. I don’t have a DRO, and my mill has a fair amount of of backlash, so after cutting the “V” out with my bandsaw, I just plunged down with first a 1” mill, then went to my 1-5/16”. Aside from initially cutting a hair too deep with my bandsaw, I am very pleased how they came out. The extra groove in the bottom of the 2” block will be fine, as this is just a backup block for my bender.

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