Gunner Asch wrote:

On Tue, 13 Jul 2010 08:13:59 -0500, Ignoramus3537
wrote:

Making of encoder mounting plates requires several accurately drilled
holes. I already made one plate and it seems to work, but I had some
problems/issues with placing holes precisely.

The material is brass (it was a great idea to use brass).

I calulated all hole positions using a spreadsheet. See "Encoder
Mounts" sheet he

http://spreadsheets.google.com/pub?k...en&output=html

To fit it over a 17mm motor shaft, I had to drill a 43/64
hole. (17.065mm).

I do not know of any way how I could drill that hole precisely, with a
huge (comparatively) MT3 drill bit, as any drill bit would wander away
at least somewhat, I think.

So what I did was, I drilled the 17mm hole aproximately where it
should be. Then, with DRO, I located the center of the hole and then
moved to what should be a point (0,0), based on the calculated
position of the center of the hole. (kind of a backwards thinking
process).

For smaller holes, all I did was start them with a center drill and
then drill with a drill bit.

It actually seems to have worked, as the encoder works just fine.

When making that mounting plate, I realized that there is a lot to
precision drilling, and want to ask now if anyone knows tricks for
drilling precise holes. I have two more plates to make.

The required precision for locating encoder base is 0.01". (which is
not that bad).

On a related note: to bolt the base to the motor, I had to drill four
holes for the mounting bolts. How can I precisely measure the distance
between holes. I tried using a caliper and it worked, obviously, but I
can not be totally sure how accurate I was. I would measure the
distance between two points in holes closest to one another, then
farthest, and average the two. But it felt that there was a lot of
wiggle room in those measurements. SEM has a manual for the motors in
question and it specifies the distance, but based on what I drilled,
the distance is slightly wrong. (the motors were made 20 years ago).,
I was lucky that I drilled the holes slightly oversize. For the next
pair of plates, I would really like to drill to-size holes in the
right place.

i

i

Something that may make life a bit easier for you are "helical couplers"

This is one of my clients..and the source for my helical couplers used
between motor and ballscrews, encoder and shafts and whatnot.

http://www.rocomcorp.com/

Tell em the OmniTurn guy recommened them.

Except for the fact that his encoders have no shaft to couple and no
bearings. His code wheel will automatically be centered on the motor
shaft, he just needs to mount the reader head within tolerance around
the code wheel.

The center hole he is drilling is just clearance for the motor shaft and
definitely does not need to be precision bored, it just has to not rub
on the motor shaft.

The mounting holes for the reader head, and the holes to mount the
adapter plate to the motor are the important ones, and all of those are
small holes that don't need to be bored either. With the tapered
centering tool that he'll either buy from US Dig or make, he can readily
center the reader head around the motor shaft and then secure the head
and mounting plate.