As you might know, I'm fitting an aluminum tube (6061 .065" wall
thickness) over the gear sticking out of a motor shaft. It fits
perfectly IMO. So now I either glue it or key it (if "key" is the
right terminology). I'm confident that my glue will do the work, but
I'd like to key it to make removing and replacing the aluminum tube
easier.

The motor and its gear have been pressed and glued against a 2 x 4
so that it is secure during drilling.

I need to know what size hole. I plan to drill with a cobalt bit and
then fashion the shank of an inexpensive equal size bit for the key.

I'm planning to go all the way through the gear/shaft/gear so that
the key will stick out from both sides and the aluminum tube will be
torqued on opposite sides.

By the way. Would there be an issue with just drilling a shallow
hole into the motor gear and using a key to turn the aluminum tube
from one side only? Does that throw things off balance? The motor
will be spinning at 5,000 to 10,000 rpm.

The motor shaft diameter is 1/5". The gear diameter is about 1/2".
The gear length is .3".

Should I use a 5/64" or 3/32" drill bit? I might be able to do the
drilling with a smaller 1/16" bit, but is a 1/16" key diameter
big enough to turn the 6061 .065" wall thickness aluminum tube?

Will that drilling risk loosening the gear on the motor shaft?

Thanks.



--
the key will be flush with the outer surface of the aluminum tube
on both sides and it will be covered by the inner race of a ball
bearing that goes around the aluminum tube so the key cannot come
out (it will probably be glued too)

I think what you are doing is "pinning" the tube to the gear/shaft. I
think the pin will quickly enlarge the hole in the tubing. At any
rate, you will want the hole in the aluminum to be smaller than the
pin, so it is a press fit. That means initially drilling the whole
assembly with a drill bit slightly smaller than your final size. Then
remove the aluminum tube and drill the gear and shaft to your final
size.

Also, the size hole made by your drills will be slightly larger than
your drill bit. Otherwise you could not get the bit out of the hole!
That is why you should get a reamer for the exact final size you want
and use it after drilling. This lets you use a regular smooth pin. A
"roll pin" should be used if you cannot ream the hole. It will shrink
to fit the hole and expand to hold tightly.

Good luck,
Paul

On Oct 16, 6:07*pm, John Doe wrote:
As you might know, I'm fitting an aluminum tube (6061 .065" wall
thickness) over the gear sticking out of a motor shaft. It fits
perfectly IMO. So now I either glue it or key it (if "key" is the
right terminology). I'm confident that my glue will do the work, but
I'd like to key it to make removing and replacing the aluminum tube
easier.

The motor and its gear have been pressed and glued against a 2 x 4
so that it is secure during drilling.

I need to know what size hole. I plan to drill with a cobalt bit and
then fashion the shank of an inexpensive equal size bit for the key.

I'm planning to go all the way through the gear/shaft/gear so that
the key will stick out from both sides and the aluminum tube will be
torqued on opposite sides.

By the way. Would there be an issue with just drilling a shallow
hole into the motor gear and using a key to turn the aluminum tube
from one side only? Does that throw things off balance? The motor
will be spinning at 5,000 to 10,000 rpm.

The motor shaft diameter is 1/5". The gear diameter is about 1/2".
The gear length is .3".

Should I use a 5/64" or 3/32" drill bit? I might be able to do the
drilling with a smaller 1/16" bit, but is a 1/16" key diameter
big enough to turn the 6061 .065" wall thickness aluminum tube?

Will that drilling risk loosening the gear on the motor shaft?

Thanks.

--
the key will be flush with the outer surface of the aluminum tube
on both sides and it will be covered by the inner race of a ball
bearing that goes around the aluminum tube so the key cannot come
out (it will probably be glued too)

Nevermind, too difficult drilling through the gear.