On 17 Jan 2016 02:44:58 GMT, "DoN. Nichols"
wrote:
On 2016-01-16, wrote:
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.
O.K. That 1x1" -- is that square solid stock, or angle stock?
Solid 6061T6
And the 1-3/8" deep suggests that the cuts are from the end, not
through the thickness, even if it is solid square stock.
It is through the thickness, from the end, to make a "fork"
I may have the use of a bridgeport style mill that used 3/8" shank
cutters,
It should be able to use a number of other different shank
diameters, presuming the availability of collets or end-mill holders in
those sides. Most Bridgeports will use R-8 sized collets or similar
end-mill holders (and the holders have the benefit that the end mill
can't be pulled down into the workpiece as sometimes happens with
collets.
Some (mostly old CNC Bridgeports) use NTMB-30 tool holders
instead, and those also come in a number of sizes.
This one only has the 3/8" tool holder - all that has ever been used
on it in over 35 years.
I'm not sure how common 1/8" end mills with 3/8" shanks will be.
I would expect those to be 1/4" shanks or smaller, though you can
probably get them with large shanks at extra cost.
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)
You're going to need a number of passes first off -- and are
limited to the 5/8" depth at best, so how you are going to get 1-3/8"
deep cuts is open to question. If you mean that the slots will be
1-3/8" *long* instead -- that is easier.
The cuts are through and through 1 inch, and 1 3/8" long, from the one
end.
In any case -- use something like WD-40 or kerosene as a cutting
lube, and make sure that your end mills are two-flute center cutting
ones.
2 flute center cutting is what I have
Yes, more flutes remove more material, but for slots, there is a
particular benefit to the two-flute end mills. Yes, the end mill will
deflect during part of the cut -- but that is when one flute is in the
direction of the cut, and the other flute will be in air behind the cut.
A four-flute or more end mill has flutes out to the side during the
deflection while the one in the direction of cut is taking its heaviest
cut, so the sides will show that deflection.
It is for this reason that the UK metalworkers refer to
two-flute end-mills as "slot drills".
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????
It might actually make things worse, as the flutes catch on the
back side of the holes and try to pull the work deeper. If the milling
machine has worn leadscrews and there is backlash this could be a
problem.
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.
Not *nobody*. I've got one. So does at least two other
persons that I know semi-locally. (All hobbyists, FWIW.)
Good Luck,
DoN.
The problem is nobody around here seems to have one. The one I know
that used to be around here could only handle 2 inch cutters - not big
enough to do the job (light duty mini hobby tool of some sort) - the
guy that owned it is dead ond gone - no idea what happened to the
tools.