Small 2 flute deep slotting aluminum

Got a pic of what you're doing ? Sometimes its easier to lay out your part with Dykem and rough it out on a bandsaw before machining .
 
Yes, why do you need to do this as a slotting operation?
Also, I'm concerned you will snap the endmill- could you not use HSS?
Picture or sketch would help us understand
 
Using the excess material as grip stock. Once all the features are done on one side, I can flip it and deck off the extra thickness, freeing my part. This gives me access to the outer perimeter of the part, the inner bore, and the features around the edges all in one set up. This ensures concentricity of the important features. I could probably do it with a lot of moving of clamps, but I trust this method to pull off the critical features with lots of support and no leap frog. I'm not looking for another way to do this, but rather to adjust my methods to successfully slot the perimeter. I am getting there. This discussion has helped fire off the brain that was on strike and get the ideas flowing again.
 
I'm currently thinking I can cut the perimeter slot a little big, in multiple passes to get to full depth, then move in for a finishing pass at full depth giving me a nice finish and all around much less stress on the end mill. There are some areas that can be roughed with a larger end mill, and it's looking like the tool change would be worth the effort. As to the shape, it's a .625" thick part in the shape of a donut, with a couple of rectangular bump outs. The material is just larger than the finished part, and it is roughly .125" thicker than the finished part.
 
Here's the best sketch you are going to get from my hands lol IMG_20230904_101755.jpg
 
Lay it out . Machine the bore . Rough saw it if you have a band saw Clamp thru the bore and finish the profile . You can use any size end mill and you wouldn't be slotting . Go back in with a small end mill to get whatever radii in those corners . With a little math you could actually drill out those tangent points on the ears .
 
Roughers do a better job of breaking and clearing the chips, my experience with 1/4"/small end mills with slotting in aluminum with a manual mill is if you can't get the chips out fast enough and need some form of cutting fluid that you get aluminum welding to the end mill and it stops cutting. Loading up and chip welding is very likely to occur, you can use air or vacuum cleaning for clearing the chips, and some WD40 or similar fluid. slotting in aluminum can often result in a poor finish and an oversized slot, so best to slot with a smaller end mill and finish the wall with climb cutting. Most roughers are not center cutting so one cannot plunge down, but they are great for clearing a lot of material quickly. On a piece like you have, you could core the inside diameter to remove the bulk of the hole material.

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ProCut 1/4" Cobalt Roughing End Mill TiCN Coating 3 Flute Fine Tooth | eBay

•M-42 Cobalt - Fine Tooth Roughing End Mills •For high production milling in difficult to machine materials such as iconel, hastalloy, titanium alloys and other materials up to 40 Rc. Coating TiCN Decimal Equivalent 0.25″.
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1/4" Carbide Endmill 3 Flute for Aluminum Roughing .020" Rad | eBay

For aluminum roughing. TiAlN coated. Center Cutting.
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1/4" x 3/8" x 7/8", 3 Flute, Single End, Square End Roughing End Mill (M) | eBay

Interstate - 1/4" Diam, 3/8" Shank Diam, 7/8" Length of Cut, 3 Flute, Cobalt, Single End, Square End Roughing End Mill. Flute Direction. Square End. Single or Double End. Extended Reach (Yes/No). Material Grade.
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Milling 0.20 x 0.60 DOC 10 IPM passes with rougher.jpg
 
I'm more looking for advice on the slotting than I am a different way to do the part. There are plenty of considerations/features that have pointed me in this direction. All of them point me towards the simplicity of workholding and accuracy of this method. So what I'm thinking now is that a one pass ,deep, 1/4" slot is too big of a gamble for me. Perhaps not if I was using a cnc, or was better equipped with coolant and shop air. I'm considering doing multiple, progressively deeper passes just outside the part finished dimensions, then finishing with a pass at full depth right on the final dimension. This gives me the reduced stress on the mill and easier clearing of chips. It also makes for clearance during that light finish pass at depth. As I am working in Aluminum I am thinking I might be ok to take these passes just shy of one diameter deep. that would get me there in 3 passes. Is this too aggressive still?
 
Oh, and I usually use kerosene with a bit of oil in a squirt bottle when cutting aluminum. It has done a very nice job keeping my 4 flute mills clean, and I know they don't clear chips like a 2 flute. I'm thinking that should be good If I'm not constantly blasting it with air. The thought of atomizing that much fuel in the shop had me thinking something less flammable. If I don't go full depth in one pass, I think I am happy going with the kerosene. I'm still a bit unsure as to how to figure a safe depth of cut while full slotting.
 
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