Looking for (idler?) gear wheel of HP-46 printer unit

[Duane Hess]

You might want to look at this thread:
http://www.hpmuseum.org/forum/thread-5895.html
A forum user in that thread, Damaltor, provides a German site for the 68 tooth gear and a brass bushing. (thank God for Google translate)

The thread provides the source I used for the 68 tooth gear and brass bushing. Mixing Mod 0.4 & Mod 0.5 is not a good idea; teeth won't mesh correctly. I'm very sure the gear in your printer is modul/modulo/modulus/module/mod 0.4 (spellings vary). Further, the mod # is integrally tied to the gear diameter. A 17 tooth gear Mod 0.5 will be larger than 0.4. The Mod 0.5 gear is approx. 2.0 mm too large in diameter.

I ordered the 17 tooth gear from HPC Gears (England). You need to select "spur gears", then specify characteristics. The basic gear has a 2.0 mm bore (ZPG0.4-17), I special ordered it with a 3.0 mm bore (ZPG0.4-17-S03). However, I probably should have ordered it with a 4.0 mm bore, so both gears would fit on the bushing. http://www.hpcgears.com
part-list: http://www.hpcgears.com/pdf_c33/23.6-23.9.pdf
*** note this list will have metal and delrin (plastic) gears with & w/o hubs
---> you want delrin. I don't believe in mixing metal/plastic unless you know it will pass the test of time. Personally I'd be concerned about wear. Naturally, I'm sure, that depends on the amount of use.
** HPC has a 68 tooth gear. Pretty sure I ordered the 68 tooth from the German source, as if I remember, the German source was approx. 1/3 the cost.

The two gears together are approx. 0.5 mm thinner (assuming I can read a micrometer) than the original gear. In my case I'll have to file down the length of the bushing, so probably can use extra length to compensate. I doubt the total "teeth width" would be be an issue, but potential shimmy up/down the shaft the gears ride on would be. If nothing else a trip to the hardware store should come up with a 0.5 mm nylon washer for a spacer.
** don't forget to re-install the exceptionally thin metal washer under the "C" clip at the end of the shaft when you're done. It keeps the gear from rubbing on the clip & hence, the clip rotating and possibly popping off. (although its on tight enough, you wouldn't think so)

Even if I ordered the 17 tooth gear with a 4.0 mm bore, I'd still epoxy the two gears together. Rotating the drum doesn't take a lot of force, but the paper advance function (activated by a lever pushing on the drum gear), takes some power. At least rotating everything by hand makes you think so. I'd be concerned w/o epoxying them together eventually the 17 tooth gear would strip off the bushing. Just my guess.

Further, I plan on making sure the inside of the bushing (and smaller gear, in my case) will have a thick-(not stiff)/stay-in-place grease (not oil). Especially since there will now be a brass bearing rotating on the shaft. Too bad there was no 3.0 mm bore 68 tooth gear, at least that I could find.

When I find my notes, I'll post the measurements I made of the gear. My printer, an EP-104 (from a Canon calc), is a descendant of the EP-102 printer in the HP-46. Found some web pages describing both printers & I'm quite sure the two printers use identical gears; but would warrant you verifying your gear.

*** original post time + approx. 1 hour -- EDIT to correct typos & incorrect statement (paper advance).