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Milling Slots

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crueby:
With my little Sherline I have combined the two on thick steel - chain drill, then do plunge cuts with a smallish end mill just to connect the dots, taking out just the narrow section between the holes. That lets me remove the center block, and come back doing side cuts to trim off the remaining scallop shapes to get a smooth edge.

internal_fire:

--- Quote from: vtsteam on January 19, 2023, 06:20:34 PM --- I'm going to stick with the end mill plunge method.

--- End quote ---

Something I have done a few times is to chain drill first with a smaller drill and then follow with an endmill plunge. Most endmills are much happier using a starter hole when plunging.

Gene

[I see Chris beat me by 31 seconds.  :Lol:]

crueby:

--- Quote from: internal_fire on January 19, 2023, 07:10:58 PM ---
--- Quote from: vtsteam on January 19, 2023, 06:20:34 PM --- I'm going to stick with the end mill plunge method.

--- End quote ---

Something I have done a few times is to chain drill first with a smaller drill and then follow with an endmill plunge. Most endmills are much happier using a starter hole when plunging.

Gene

[I see Chris beat me by 31 seconds.  :Lol: ]

--- End quote ---
I guess I must type just that little bit faster!   :Lol:

Jasonb:
The problem with using a similar size drill and then cutter is that you still end up with parts of the cut that mean full cutter engagement which is where lighter less rigid machines may struggle so end up having to use a shallow DOC for those parts which partly defeats the object of drilling first. I tend to use stitch drilling more for larger areas where there is a lump in the middle that can then be knocked out and you only have a max of 1/2 cutter diameter when clean ng up the edges. You can also find the cutter is pulled sideways in these areas of full width engagement

Faced with a similar slot I would tend to drill and plunge the ends to diameter and then run a smaller diameter 3 or 4 flute cutter down the middle which should allow a deeper cut and then finally offset until I get to width with full vertical depth cuts.

Recent example was this pair 80mm long x 8mm dia x 6mm deep.

First drilled 6mm at the ends and then milled out with 1.5mm deep ( 060" ) passes



These were actually part of a fabrication so roughing undersize also helped should anything move during soldering. They were then plunge cut at each end with an 8mm 3-flute cutter



Finally taken out to finished 8mm width with a pass down each side at full depth of 0.8mm and then 0.2mm stepover.

Charles Lamont:
"stepover" = climb milling?

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