Have a mini-lathe, am making a gadget to pun on the toolpost so I can use
the lathe chuck as an indexing head and mill sections/slots whatever.

All my mills have a 3/8" shank with a flat.

Is a 3/8 hole bored in the spindle and a set-screw good enough?

Or should I make some sort of collet and holder?

If I make a collet, what keeps the mill from slipping - just friction, or is
there supposed to be some sort of method involving that flat?

Bear in mind there's not a lot of room...

jt:

I'm pretty sure the flat on the shank of the mill is for the set screw - as
in an end mill holder. The flat would resolve any issues that would come up
with scoring the shank.

After years of following this newsgroup, it seems that an end mill holder
has an edge over a collet for milling. I just made some 3/8" end mill
holders for my CNC mill using 23/64" drill & 3/8" reamer.

The "not a lot of room" was the bugger for me. I modified an Atlas milling
attachment for my SB10k and managed to mill a couple of pieces. Fixturing
and rigidity were a constant problem. The lowest of the low end mill/drill's
was a gigantic leap forward.

"jt" wrote in message
...
Have a mini-lathe, am making a gadget to pun on the toolpost so I can use
the lathe chuck as an indexing head and mill sections/slots whatever.

All my mills have a 3/8" shank with a flat.

Is a 3/8 hole bored in the spindle and a set-screw good enough?

Or should I make some sort of collet and holder?

If I make a collet, what keeps the mill from slipping - just friction, or
is
there supposed to be some sort of method involving that flat?

Bear in mind there's not a lot of room...

"John Hofstad-Parkhill" wrote in message
news
jt:

I'm pretty sure the flat on the shank of the mill is for the set screw -
as
in an end mill holder. The flat would resolve any issues that would come
up
with scoring the shank.

After years of following this newsgroup, it seems that an end mill holder
has an edge over a collet for milling. I just made some 3/8" end mill
holders for my CNC mill using 23/64" drill & 3/8" reamer.

Should I use an exact 3/8 reamer, or one that's oversize?

"jt" wrote in message
...

"John Hofstad-Parkhill" wrote in message
news
jt:

I'm pretty sure the flat on the shank of the mill is for the set screw -
as
in an end mill holder. The flat would resolve any issues that would come
up
with scoring the shank.

After years of following this newsgroup, it seems that an end mill
holder
has an edge over a collet for milling. I just made some 3/8" end mill
holders for my CNC mill using 23/64" drill & 3/8" reamer.

Should I use an exact 3/8 reamer, or one that's oversize?


Or could I just plunge a 3/8 endmill into a 23/64 hole?

I'd use a 3/8" reamer, not over or under.

Failing that, I'd bore it out, which is not unlike plunging the endmill.
However I'm not sure what size hole you'd end up with. Nothing is perfect,
but most of the end mill holders I have are close enough to give a bit of
resistance (compressing the air) when inserting the mill.


"jt" wrote in message
...

"jt" wrote in message
...

"John Hofstad-Parkhill" wrote in message
news
jt:

I'm pretty sure the flat on the shank of the mill is for the set
screw -
as
in an end mill holder. The flat would resolve any issues that would
come
up
with scoring the shank.

After years of following this newsgroup, it seems that an end mill
holder
has an edge over a collet for milling. I just made some 3/8" end mill
holders for my CNC mill using 23/64" drill & 3/8" reamer.

Should I use an exact 3/8 reamer, or one that's oversize?


Or could I just plunge a 3/8 endmill into a 23/64 hole?

jt wrote:
"John Hofstad-Parkhill" wrote in message
news
jt:

I'm pretty sure the flat on the shank of the mill is for the set screw -

as

in an end mill holder. The flat would resolve any issues that would come

up

with scoring the shank.

After years of following this newsgroup, it seems that an end mill holder
has an edge over a collet for milling. I just made some 3/8" end mill
holders for my CNC mill using 23/64" drill & 3/8" reamer.


Should I use an exact 3/8 reamer, or one that's oversize?



The commercial units are hardened, then ground true. Maybe using the
reamer would work, though. The shanks are generally .0005" to .001"
undersize. Mike a few of your shanks to see what size they are.
If you have something you can set up as a toolpost grinder, you might
ream first, and if the shanks are too tight, then you can do a very
light ID grind on it. Otherwise, you could make up a barrel lap
and lap the ID slightly larger.

Jon

On Mon, 1 Dec 2003 11:51:51 -0400, "jt" wrote:
Or could I just plunge a 3/8 endmill into a 23/64 hole?

Don't do that. It'll be oversize. Bore it or ream it.

Gary

"Gary Coffman" wrote in message
...
On Mon, 1 Dec 2003 11:51:51 -0400, "jt"
wrote:
Or could I just plunge a 3/8 endmill into a 23/64 hole?

Don't do that. It'll be oversize. Bore it or ream it.


That's what I thunk, but thanks for confirming...

The chip load per tooth in milling steel with hss is only a few thousands,
so if the hole is off center by just a few or the hole is on center but
oversized (mill will then be pushed to one side by the set screw) a multi
flute mill will not mill with all flutes.(not the end of the world if you
don't need max mill life, speed or accuracy of size).
If you are using a single flute mill like an indexable one then it isn't as
important.
Having the hole dead center is probaly first concern, if oversize you may be
able to wrap the endmill in shim stock but this can be a pain especially if
you don't have shim stock.

"jt" wrote in message
...

"Gary Coffman" wrote in message
...
On Mon, 1 Dec 2003 11:51:51 -0400, "jt"
wrote:
Or could I just plunge a 3/8 endmill into a 23/64 hole?

Don't do that. It'll be oversize. Bore it or ream it.


That's what I thunk, but thanks for confirming...