Re: I just spent a couple of hours making a $5 tool ...

Bob Engelhardt <bobengelhardt@xxxxxxxxxxx> wrote in message
news:h2h72i02r8p@xxxxxxxxxxxxxxxxxxxx
In other words, a typical evening in the shop.

http://home.comcast.net/~bobengelhardt/HandPuller.jpg

It's for pulling the hand off a dial indicator. A teeny tiny gear
puller. I should have included a size reference in the picture: it's
1/2" high x 3/4" wide. The tip of the pusher is .030" more or less.
It's a 1/16" drill bit ground down.

It was fun.

Bob


I'm not a mechanical engineer , but electronics and often need to
form splined slots to round aluminium potentiometer shaft, to take splined
insert knobs. Starting with a standard, neat little, pipe cutter
http://home.graffiti.net/diverse:graffiti.net/spliner.jpg
The pattern repeats for only one diameter and a certain
degree of intrusion. Aiming here for 16 around a nominal 6mm spindle.
Proof the concept works. Robbed the steel gripper wheel from a butterfly can
opener, sharpened the points a bit and opened out the central hole. Mounted
in the pipe cutter and produced a neat ring of indents. These were about 2mm
apart and 7 equally spaced around, when cutter advanced far enough in. So a
cog with 1mm spacing should work even easier as long as not too wide. Actual
splined shafts have a 1mm spacing and 16 around.
If nothing else a thin approx 1mm tooth spacing cog from a clockwork clock
mechanism would make an excellent way of marking pot shafts before making
axial cuts with a grind wheel.
I've opened out the slot in a Rolson pipe cutter from 3.5mm to just over 5mm
and it will now hold
neatly and freely rotating, a 16mm diameter x 5 mm ball race.
I know I can grind into the outer race with a Dremmel and thin disc
(freehand) and cutting 1mm spaced teeth is possible as proved by cutting
,freehand so rough, some 1mm spaced teeth around a steel washer. Running a
24 TPI hacksaw tightly around a pot shaft produced a ring of about 19 small
indents, so 1mm is about right for 16. Next a bit of trig to find a whole
number of rotations into 16 mm diameter to give about 1mm spacing.
Too many belts in the lathe drive train. Settled on a doubled large cable
tie around the chuck, clamped to the lathe bed, as a brake and
anti-backlash. And marking around the chuck 50 divisions covered with a
needle, as indicator, on an arm to a magnetic base. Pulling at the motor V
belt to step round. Mounted the Dremmel on 3 short pieces of Dexion to set
on the tool post with a 45 degree set. 3 rounds of cuts to get to final
profile.
Next time I will spend more time fiddling around DTI setting in the 4-jaw
before starting as there was eccentricity.
There is a lunate form to the cutting edges, maybe due to flexing of the
0.6mm thick grinding disc or I did not pay attention to changing direction
of cuts on "odd" and "even" teeth on each pass. Perhaps I should have done
another round of cuts but at the previous depth setting to cut into the
lunate form more. Perhaps it was due to axial play on the Dremmel. Anyway it
works well enough for this purpose. No more than 5mm splining or the
tightening force would be more than finger force on the knurled head bolt
and the aluminium of the holding frame would snap with anything more than
finger force. It is possible to re-engage the spliner further along, synched
with the first cut to form extended splines.
In use leave the pot spindle full length so the 2 round rollers of the
existing pipe cutter can react against the extended shaft, and
hold the free end of the shaft with moplegrips in case the
back torque is too high and the pot end stop breaks up. Afterwards cut to
length and the diametrical cut. Remember the length is back to the
mounting face, as bush length varies. For the slot
start with thin grindwheel in Dremmel and complet with a hacksaw.
If the slot needs narrowing place some strip in the slot before squashing
or you will have no control it and will fully squash.
16 evenly spaced cuts around the pot shaft
in the bottom view. If not deep enough then at least a good accurate guide
for starting some deeper cuts done freehand with a Dremmel. Didn't think to
measure the diameter of the cutting disc before starting and the others vary
in diameter, but by comparing to them, somwhere between 0 and 0.2mm erosion
of diameter in use
I like a challenge and may learn something along the way. A week ago , if
someone asked me - can you cut a 0.5mm wide slot in the steel of a ball
race, using mundane equipment, I would have said no.


--
General electronic repairs, mainly music equipment thesedays ,
but anything considered other than TVs and PCs
http://www.divdev.fsnet.co.uk/repairs.htm

Diverse Devices, Southampton, England


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