I've got a little job I need to do/get done. I am working on the wing
strut fittings for the bush-plane. There are 4 struts - so 8 strut end
fittings. They are made of 1X1 6061T6 - 4 abot 4 1/4 inches long, and
4 about 5 1/2 inches long.
2 need 1/4 inch slots, 4 need .195" slots, and 2 need 3/16 " slots -
all 1 3/8" deep.

I may have the use of a bridgeport style mill that used 3/8" shank
cutters, and I have located a 3/16" end mill that has 5/8" cutting
depth (end mill)

How close to 3/16 will I likely be able to get? (thinking the cutter
is going to want to "walk" a bit in the cut) Would it help a lot if I
drilled a row of 1/8" or 5/32 holes down the center of the slot first
to reduce the chip load????

Or do I just farm it out to a CNC shop??

If I had access to a horizontal mill it would make life a lot easier,
but nobody has them any more.