I got a SNAFU in my project...

I need to mount a 10 tooth .200 pitch timing pulley to a 3/8 shaft on my
servo motor. I bored the pulley yesterday before I noticed there's not
enough meat left for a key, let alone set screws.

Anyway, I'm looking for a way to mount this pulley. Press fit? silver
solder? I've got NO experience with silver solder, which kind? Other ideas?

Karl

"Karl Townsend" wrote in message
anews.com...
I got a SNAFU in my project...

I need to mount a 10 tooth .200 pitch timing pulley to a 3/8 shaft on my
servo motor. I bored the pulley yesterday before I noticed there's not
enough meat left for a key, let alone set screws.

Anyway, I'm looking for a way to mount this pulley. Press fit? silver
solder? I've got NO experience with silver solder, which kind? Other
ideas?

Karl

If you heat it enough to silver-braze, it will wind up dead-soft annealed.
If that isn't OK, then you might consider that the shear strength of
industrial-grade epoxies run upwards of 5,000 psi. It might do the job.

--
Ed Huntress

If you heat it enough to silver-braze, it will wind up dead-soft annealed.
If that isn't OK, then you might consider that the shear strength of
industrial-grade epoxies run upwards of 5,000 psi. It might do the job.

--
Ed Huntress

Now, there's an idea. Any particular product?

I could reinforce it a bit with a custom key that is only 0.025" high into
the pulley.

Karl Townsend wrote:

If you heat it enough to silver-braze, it will wind up dead-soft annealed.
If that isn't OK, then you might consider that the shear strength of
industrial-grade epoxies run upwards of 5,000 psi. It might do the job.

--
Ed Huntress

Now, there's an idea. Any particular product?

I could reinforce it a bit with a custom key that is only 0.025" high into
the pulley.

A tiny key and some good Locktite ought to do it. You could also cross
drill and use a roll pin which would be a lot easier to disassemble when
needed.

On Wed, 22 Jul 2009 08:09:18 -0500, "Karl Townsend"
wrote:


If you heat it enough to silver-braze, it will wind up dead-soft annealed.
If that isn't OK, then you might consider that the shear strength of
industrial-grade epoxies run upwards of 5,000 psi. It might do the job.

--
Ed Huntress

Now, there's an idea. Any particular product?

I could reinforce it a bit with a custom key that is only 0.025" high into
the pulley.


Depending on the hub design and load you might also use a tapered pin
to retain the pulley. They also make a tapered pin with the small end
threaded for a retaining nut.

Cheers,

Bruce
(bruceinbangkokatgmaildotcom)

"Karl Townsend" wrote in message
anews.com...

If you heat it enough to silver-braze, it will wind up dead-soft
annealed.
If that isn't OK, then you might consider that the shear strength of
industrial-grade epoxies run upwards of 5,000 psi. It might do the job.

--
Ed Huntress

Now, there's an idea. Any particular product?

No specifics, because I'm not up on the latest.

But here are a few general points. You probably can get away with a
room-temperature-cure product (which generally means amine-type hardeners),
because your application probably doesn't justify the complication of A-B
cures at two different elevated temperatures. I always try to ask an expert,
like someone at 3M, before committing to something like this. You'll want to
make clear to them all the details of your application -- metals being
joined, etc. You need shear strength but not much peel/cleavage strength. To
get the latter you generally sacrifice the former, so a general-purpose
epoxy, which usually is oriented toward a compromise, is not your best
choice. And you want to be wary of anything that has a fast cure time. They
may have that issue solved today, but any cure with epoxy that takes less
than 24 hours usually compromises performance.

Assuming both parts are steel, you may want more than extreme cleanliness.
You may want to use the scratch-in method for getting the best bond.

Anyway, I'd try epoxy first, because if it fails, no harm is done to the
parts.


I could reinforce it a bit with a custom key that is only 0.025" high into
the pulley.

I'd be wary of that because it could interfere with getting a good
scratch-in coating on the parts. But whatever works.

--
Ed Huntress

I'd be wary of that because it could interfere with getting a good
scratch-in coating on the parts. But whatever works.


What do you mean here? Don't know the term scratch in.

"Karl Townsend" wrote in message
anews.com...

I'd be wary of that because it could interfere with getting a good
scratch-in coating on the parts. But whatever works.


What do you mean here? Don't know the term scratch in.

Clean the steel conventionally as well as you can. Then mix up a small
amount of epoxy and apply a glob to a piece of sandpaper. Sand the spot
you're bonding to, "wet" with the epoxy, until you've scratched into the
entire surface. Keep the spot wet with epoxy; don't let air touch the metal
again once you've started.

If you want to be neat about it, apply another glob of mixed epoxy to a
piece of rag, and wipe the spot to wipe away the grit, oxide, etc. Again,
keep it wet; air should never touch metal.

Then do the same to the other piece you're bonding. Apply another small glob
of epoxy to the spot and stick the two pieces together. Let it cure.

This "scratch-in" method produces similar results to the chemical treatments
used in production -- phosphoric-acid anodizing on aluminum, and some acid
etches used on steel. It's used in high-grade repair work and some custom
assembly. Obviously, it's too labor intensive to use in production. It works
on most metals but it's particularly useful on stainless and aluminum. The
mechanical bond you get from the rough surface is secondary. The primary
objective is to produce a clean, high-energy surface to which the epoxy gets
a true adhesive bond. Scratching also produces more surface area for the
adhesive bonding.

The higher the strength of epoxy you're using, the more critical it is to
have an oxide-free surface to bond to. The difference is really large. Also,
keep in mind that you do not want a really tight fit in metal-to-metal
bonding with epoxy. You get the strongest joint with a gap of 0.002" to
0.005", depending on the epoxy. For that reason some people leave the
sanding grit in the epoxy and don't clean it off; it serves as a spacer.
It's easy to starve an epoxy joint and ruin its strength.

Doing the scratch-in thing to a hole or other internal shape is a little
tricky, but it works.

BTW, this is for a high-strength joint. If the torque load is light enough
that green Loctite would do the job, then this is all a waste of time.

--
Ed Huntress

How much torque is involved? Makes a huge difference.

Really quick & easy, and easy to undo (unlike silver solder): a tack of
weld on the end, bridging the shaft & sprocket. Quick & Dirty (tm).

Roll pin or taper pin. If high torque. Whilst drilling for a pin, I
assure the alignment by doing the tack weld above & drilling both at once.

Bob

Bob Engelhardt wrote:

How much torque is involved? Makes a huge difference.

Really quick & easy, and easy to undo (unlike silver solder): a tack of
weld on the end, bridging the shaft & sprocket. Quick & Dirty (tm).

Roll pin or taper pin. If high torque. Whilst drilling for a pin, I
assure the alignment by doing the tack weld above & drilling both at once.

Bob

Welding an aluminum sprocket onto a steel shaft would be an interesting
trick...

Pete C. wrote:
Welding an aluminum sprocket onto a steel shaft would be an interesting
trick...

Aluminum?

Bob Engelhardt wrote:

Pete C. wrote:
Welding an aluminum sprocket onto a steel shaft would be an interesting
trick...

Aluminum?

I've not seen any 10T .200 pitch sprockets available in anything but
aluminum or plastic.

"Pete C." wrote in message
ster.com...

Bob Engelhardt wrote:

Pete C. wrote:
Welding an aluminum sprocket onto a steel shaft would be an interesting
trick...

Aluminum?

I've not seen any 10T .200 pitch sprockets available in anything but
aluminum or plastic.

material is steel, don't know grade, soft and easy to machine

Karl

"Bob Engelhardt" wrote in message
...
How much torque is involved? Makes a huge difference.

1/2 hp. servo. I think this is at 3000 rpm. Torque*rpm* factor= hp. Don't
remember factor off hand.

Really quick & easy, and easy to undo (unlike silver solder): a tack of
weld on the end, bridging the shaft & sprocket. Quick & Dirty (tm).

Don't like this idea.

Roll pin or taper pin. If high torque. Whilst drilling for a pin, I
assure the alignment by doing the tack weld above & drilling both at once.

Bob

May try a roll pin if adhesive bonding don't work.

On Wed, 22 Jul 2009 10:20:20 -0500, the infamous "Karl Townsend"
scrawled the following:


"Bob Engelhardt" wrote in message
...
How much torque is involved? Makes a huge difference.

1/2 hp. servo. I think this is at 3000 rpm. Torque*rpm* factor= hp. Don't
remember factor off hand.

Really quick & easy, and easy to undo (unlike silver solder): a tack of
weld on the end, bridging the shaft & sprocket. Quick & Dirty (tm).

Don't like this idea.

Roll pin or taper pin. If high torque. Whilst drilling for a pin, I
assure the alignment by doing the tack weld above & drilling both at once.

Bob

May try a roll pin if adhesive bonding don't work.

If both the shaft and gear hub are soft enough, could you drill and
tap a couple split holes in the end of the shaft/side of gear, where
the screw would engage both? It would give you a key of sorts and
hold the gear in place at the end of the shaft. Maybe add Loctite.

--
Mistrust the man who finds everything good, the man who finds everything
evil, and still more the man who is indifferent to everything.
-- Johann K. Lavater

On Jul 22, 8:49*am, "Karl Townsend"
wrote:
I got a SNAFU in my project...

I need to mount a 10 tooth .200 pitch timing pulley to a 3/8 shaft on my
servo motor. I bored the pulley yesterday before I noticed there's not
enough meat left for a key, let alone set screws....
Karl

Could you make and attach a separate hub?

"Karl Townsend" wrote in message
anews.com...
I got a SNAFU in my project...

I need to mount a 10 tooth .200 pitch timing pulley to a 3/8 shaft on my
servo motor. I bored the pulley yesterday before I noticed there's not
enough meat left for a key, let alone set screws.

Anyway, I'm looking for a way to mount this pulley. Press fit? silver
solder? I've got NO experience with silver solder, which kind? Other
ideas?

Karl

If there is any hub, split it with a saw blade. Make or buy 2-piece shaft
collar with the ID the same as the OD of the hub and clamp it. Otherwise,
some green loctite.

If there is any hub, split it with a saw blade. Make or buy 2-piece shaft
collar with the ID the same as the OD of the hub and clamp it. Otherwise,
some green loctite.

I'd have to make a hub, do-able but not easy. I started with a six inch
length of timing pulley stock. green loctite or whatever Ed says will be my
first run.

On Jul 22, 10:39*am, "Buerste" wrote:
"Karl Townsend" wrote in message

I need to mount a 10 tooth .200 pitch timing pulley to a 3/8 shaft on my
servo motor. I bored the pulley yesterday before I noticed there's not
enough meat left for a key, let alone set screws.

If there is any hub, split it with a saw blade. *Make or buy 2-piece shaft
collar with the ID the same as the OD of the hub and clamp it.

This gets my vote, too. If (unlikely) the hub has enough
extension, one can also pipe-thread it with a die, and cinch
with a pipe-threaded nut (to make a kind of collet). The taper
on pipe threads makes a lot of circular wedging operations
do-able.

On Jul 23, 11:16*am, whit3rd wrote:


This gets my vote, too. *If (unlikely) the hub has enough
extension, one can also pipe-thread it with a die, and cinch
with a pipe-threaded nut (to make a kind of collet). * The taper
on pipe threads makes a lot of circular wedging operations
do-able.

Or run the pipe tap into the hub and bore out a reducer bushing to fit
the shaft, then slit the threaded end to allow it to compress. Iron
pipe fittings aren't always threaded very accurately, so I center a
machined brass one in the lathe and use it to center the threads of
iron pipe and fittings. Steel hydraulic fittings turned from bar stock
may be concentric enough inside and out.

jsw

On Wed, 22 Jul 2009 07:49:26 -0500, "Karl Townsend"
wrote:

I got a SNAFU in my project...

I need to mount a 10 tooth .200 pitch timing pulley to a 3/8 shaft on my
servo motor. I bored the pulley yesterday before I noticed there's not
enough meat left for a key, let alone set screws.

Anyway, I'm looking for a way to mount this pulley. Press fit? silver
solder? I've got NO experience with silver solder, which kind? Other ideas?

Karl

For a timing pulley on a 3/8" shaft, I think Loctite would more than
suffice. I'd use Loctite 609 or 680. These are anaerobic one-part
adhesives, not epoxies. I have both, use both and frankly can't tell
any difference between them. Tawm, they're both green.

Parts should fit snugly. They should be reasonably clean but this
isn't terribly fussy. A quick squirt of Brake-Kleen and a wipe or
blow off is quite sufficient. Better bonds are achieved if an
accelerator is used, but they work OK without it. Once assembled with
these compounds, after some cure time you'd probably need heat to get
the parts apart. About 400F would get it done.

Don Foreman writes:


Parts should fit snugly. They should be reasonably clean but this isn't
terribly fussy. A quick squirt of Brake-Kleen and a wipe or blow off is
quite sufficient.

I've always used starting ether for the final cleaning as the
residue from other stuph can bite you back.

Comments?
--
A host is a host from coast to
& no one will talk to a host that's close........[v].(301) 56-LINUX
Unless the host (that isn't close).........................pob 1433
is busy, hung or dead....................................20915-1433

"David Lesher" wrote in message
...
Don Foreman writes:


Parts should fit snugly. They should be reasonably clean but this isn't
terribly fussy. A quick squirt of Brake-Kleen and a wipe or blow off is
quite sufficient.

I've always used starting ether for the final cleaning as the
residue from other stuph can bite you back.

Comments?

I don't know how pure starting ether is, but commercial acetone, for
example, usually is recycled and contains some hydrocarbons. In good
fiberglass shops, they don't use the commercial grade, which is the stuff
you find in paint stores.

--
Ed Huntress

On Wed, 22 Jul 2009 18:51:42 +0000 (UTC), David Lesher
wrote:

Don Foreman writes:


Parts should fit snugly. They should be reasonably clean but this isn't
terribly fussy. A quick squirt of Brake-Kleen and a wipe or blow off is
quite sufficient.

I've always used starting ether for the final cleaning as the
residue from other stuph can bite you back.

Comments?

Brake-Kleen isn't supposed to leave a residue. I use it for final
cleaning of bearings after gross cleaning with varsol and acetone,
which do leave residues.

On Wed, 22 Jul 2009 23:49:59 -0500, the infamous Don Foreman
scrawled the following:

On Wed, 22 Jul 2009 18:51:42 +0000 (UTC), David Lesher
wrote:

Don Foreman writes:


Parts should fit snugly. They should be reasonably clean but this isn't
terribly fussy. A quick squirt of Brake-Kleen and a wipe or blow off is
quite sufficient.

I've always used starting ether for the final cleaning as the
residue from other stuph can bite you back.

Comments?

Brake-Kleen isn't supposed to leave a residue. I use it for final
cleaning of bearings after gross cleaning with varsol and acetone,
which do leave residues.

Yeah, I've used lacquer thinner, Brake-Kleen, and Berryman's B-12 carb
cleaner as non-residue cleaners for decades now. All work great.

--
Mistrust the man who finds everything good, the man who finds everything
evil, and still more the man who is indifferent to everything.
-- Johann K. Lavater

"Don Foreman" wrote in message
...
On Wed, 22 Jul 2009 07:49:26 -0500, "Karl Townsend"
wrote:

I got a SNAFU in my project...

I need to mount a 10 tooth .200 pitch timing pulley to a 3/8 shaft on my
servo motor. I bored the pulley yesterday before I noticed there's not
enough meat left for a key, let alone set screws.

Anyway, I'm looking for a way to mount this pulley. Press fit? silver
solder? I've got NO experience with silver solder, which kind? Other
ideas?

Karl

For a timing pulley on a 3/8" shaft, I think Loctite would more than
suffice. I'd use Loctite 609 or 680. These are anaerobic one-part
adhesives, not epoxies. I have both, use both and frankly can't tell
any difference between them. Tawm, they're both green.

Parts should fit snugly. They should be reasonably clean but this
isn't terribly fussy. A quick squirt of Brake-Kleen and a wipe or
blow off is quite sufficient. Better bonds are achieved if an
accelerator is used, but they work OK without it. Once assembled with
these compounds, after some cure time you'd probably need heat to get
the parts apart. About 400F would get it done.

I like the "booger green" for permanent installations and the "snot green"
if I might have to take it apart.

"Karl Townsend" wrote in message
anews.com...
I got a SNAFU in my project...

I need to mount a 10 tooth .200 pitch timing pulley to a 3/8 shaft on my
servo motor. I bored the pulley yesterday before I noticed there's not
enough meat left for a key, let alone set screws.

Anyway, I'm looking for a way to mount this pulley. Press fit? silver
solder? I've got NO experience with silver solder, which kind? Other
ideas?

Karl

Press fit and green Loctite

or

Drill and roll pin

or

BOTH!

Karl Townsend writes:

Anyway, I'm looking for a way to mount this pulley.

Finely thread the pulley ID and the shaft OD. Might require disassembling
the motor.

On Wed, 22 Jul 2009 07:49:26 -0500, "Karl Townsend"
wrote:

I got a SNAFU in my project...

I need to mount a 10 tooth .200 pitch timing pulley to a 3/8 shaft on my
servo motor. I bored the pulley yesterday before I noticed there's not
enough meat left for a key, let alone set screws.

Anyway, I'm looking for a way to mount this pulley. Press fit? silver
solder? I've got NO experience with silver solder, which kind? Other ideas?

Karl



Just clean pulley and shaft and then use Loctite 603 or a close relative. I
use it with no problems both on pulleys and to drive 5" dia 4340 blanks on
1/2" drill rod arbour. Works well enough to take .050" cuts with nice blue
chips :-)


Mark Rand
RTFM

"Karl Townsend" wrote in message
anews.com...
I got a SNAFU in my project...

I need to mount a 10 tooth .200 pitch timing pulley to a 3/8 shaft on my
servo motor. I bored the pulley yesterday before I noticed there's not
enough meat left for a key, let alone set screws.

Anyway, I'm looking for a way to mount this pulley. Press fit? silver
solder? I've got NO experience with silver solder, which kind? Other
ideas?

roll pin?