Where to get THIS mechanical part?

Try

Ed,

Thank you for your prompt reply. Sadly, the URL did not work and instead went to their home page

and then to Gears [kinda like your URL] and then to delrin [cause the gear looks a little like a plastic] but from there, got lost.

plus the price !! some of those gears are $10+ Seems a bit much when you consider the original 10 years ago was $10 for the whole assembly.

But, what is "pitch"?

shaft diameter: I guess, but this shaft is "keyed", or flatted [don't know the term for having part of the shaft ground flat so a gear can't slip]

- Robert -

Umm, go to Staples and buy a new pencil sharpener for $10. Considering the time and effort wasted (3 days!) trying to source a gear for a 10 year old pencil sharpener, the expenditure is a pittance.

Go to?! Spend?! You don't know my financial controller! I've been reduced to a $1.25 "twisty" thingy normally used for sharpening crayons!

Just not allowed to spend money...There's wear and tear on the vehicle, there's gasoline, there's the hour to go, there's...

Also, the replacement cost has gone up a bit, like $40 to $60.

But worse, everything still works - except the gear. The motor's fine, the "sense" switch is fine, the sharpening blades are fine, etc. Just don't belong to a "throwaway" mentality.

Do I have to 'recast" the gear myself?

- Robert -

As you haveto ask about pitch it's clear you don't have the ability to correctly specify the gear. Gears like this are made specificaly for a job, and a generic replacement would need to be machined to fit. Alow for a machine shop charging 2 hours @ $40 / h on top of finding the generic gear. If the manufacturers can not supply a replacement part... Ring their customer services.. then your sharpener is BER... cheaper to buy new than repair. You might persuade a local colledge that teaches machining to take on the job as a project for a student.

Have you thought of investing in a propeling pensil....

Regards Jonathan.

Wow, talk about mircromanagement! Maybe you can order from a catalog, pay the $5 shipping and save the wear & tear on the vehicle. The hour to go is nothing compared to the 3 days you spent looking for the gear. Maybe you could educate your financial controller by performing a cost analysis to show the savings you'll make in buying new vs. trying to salvage the old. Also, maybe you can depreciate the old one ;-) or donate it to a 3rd world country.

ms, Don't you understand that Mr. Macy is trying to return a priceless antique pencil sharpener back to fully operational status? Some historical artifacts are so important that they simply can not be replaced! ;-)

Robert, The pitch of a gear roughly correspond to the number of teeth per linear inch. A fine toothed gear has a high number of teeth per inch as measured around the circumference of a circular gear. The basic definitions of gear terminology can be found at:

or at

Good Luck, Paul D Oosterhout (I work for SAIC)

Paul,

Thank you for the informative URLs. Very keen to learn.

After visiting both sites, I never figured out if the pitch meant number of teeth per inch along the "outside", or number of teeth per inch along the "inside", or something else.

The Glossary at the engineersedge did talk about involute circle diameter, but defined it as the involute circle diameter, so I didn't understand from that source what is meant.

diameter of the outside clearance of all teeth diameter of the inside cutout, like "missing" material diameter of the teeth mating surface, which seems to be the most useful since it more relates to what the gear is doing, but probably difficult to find.

Exactly where the diameter is selected affects the circumferential linear inches and therefore impacts the determination of pitch. Or is pitch pretty "standard" in the US and getting close puts you into the right number?

PS: What is SAIC?

- Robert -

Robert, Tooth pitch is based on the number of teeth per inch along a strait rack gear. On a circular gear, tooth pitch is measured along the circumference of a theoretical line defined by the "pitch diameter". The pitch diameter roughly corresponds to the line that runs through the midpoint of the teeth's mating surfaces. But it is not quite this simple.

As you are beginning to learn, the finer details of gear geometry are surprisingly complex.

But you don't need to learn all of that stuff. For your purposes, the only parameters that you need to know are:

- the thickness of the gear

- the thickness of the hub

- the diameter of the drive shaft (plus the details of any flats or key ways that are on the shaft)

- the number of teeth on the gear

- the tooth pitch

- the tooth pressure angle

The first three dimensions can be measured directly using a micrometer or a dial caliper. And counting the number of teeth is pretty strait forward.

Determining the last two parameters is more difficult. There are procedures that manufacturers use to determine the tooth pitch and pressure angle. But these procedures, which rely on careful, precision measurements, are difficult to use on small gears (especially if the teeth are worn or damaged).

The easiest way to determine a gear's tooth geometry is to use a a set of gear tooth gauges. Look up part numbers 2069A67 or 2069A12 on

You can purchase your own set of tooth gages. But this could get expensive, since you don't know if your gears have a 14.5 or 20 degree pressure angle. Nor do you know if you have a metric or inch based gear.

Many machine shops keep a set of gear tooth gauges on hand. I suggest you call around to some of your local machine shops and ask them if you can come by and use their gauges. It will only take you a couple of minutes to determine the pitch and pressure angle.

Actually, what I really suggest you just go purchase a new pencil sharpener. ;-)

Good Luck, Paul D Oosterhout (I work for SAIC)

SAIC = Science Applications International Corporation

So it is the circle defined by the point of contact for the teeth, more or less? That's what I figured, because those diameter ratios would be the important numbers for calculating speeds, torque, etc.

Yes, it looks like one could spend a lifetime exploring this science. Has someone has designed/invented "non-scrubbing" gears? Gears that mesh and don't require mandatory slippage.

..snip..archived info

ok.

Good suggestion. My main machine shop went phhht! for various causes. Mostly blamed by agencies on the business decline after 9/11. But more likely from jobs being shipped overseas.

Well, now that the financial controller has seen the effectiveness of the manual "twisty" thingy, it's unlikely. I sure miss that satisfying grinding noise, relieving frustrations on a hapless wooden pencil. But I'm afraid the use of the extra electricity and how the electric sharpener made such a long pointy slope to the tip causing the pencil to require more sharpening compared to the shorter/squatty point of the hand sharpener is going to breed resistance to purchasing *any* parts for repairing the electric sharpener. Don't think the fact that the rate of pencil consumption dropped to less than half the former rate of pencil consumption since converting to manual sharpener went unnoticed. Unless I literally stumble over a free gear; the treasured antique will never be resurrected and will never be maintained in its pristine condition.

Is that out of San Diego? I know some people there.

- Robert -

Friction losses due to sliding contact between gear faces is a serious problem. A problem that hundreds of researchers and engineers have spent entire lifetimes trying to minimize. All and all, the modern industry standard gear tooth forms are about as efficient as one can get. Typical transmission efficiencies for spur gears range from 97 to 98%.

Properly designed chain drives and flat belt drives can be just as efficient as spur gears at transmitting mechanical power. Typical transmission efficiencies for chain drive range from 95 to 98%. But these systems are not as compact as gear drives.

I prefer mechanical pencils. My personal favorite is my old reliable Pentel Sharp 0.5mm pencil. (See

My preference for mechanical pencils is a holdover from my days working as a draftsman. Yes, I am that old. :-(

That's my company. But I've never been to the corporate headquarters. I work at a tiny little government facility in Northern Virginia.

Paul,

Thank you for the tidbits. Enjoy gett> Friction losses due to sliding contact between gear faces is a serious

I did not know it was possible to get that good. Thought the maximum was more in the 90-95% range.

Yes, I have a collection of those, but they play havoc with the pencil sharpener. Sad that the US could never make the lead refills as good a quality as Japanese. One of my "witty" assistants once announced how he liked those pencils, too, but hated having to mess with that last half inch at the end of use. He thought I'd hate it too so he went through all my lead refills and broke the last half inch off each one to save me time.

Hmmm....yes, drafting is a lost art now. Remember those ink pens with the tubes? we used flat sanding pads [for sharpening pencil points, not for sharpening ink tubes] that as you used each sheet and it got clogged, you tore a sheet off. Is that circa the same? Age? In 1966 I designed the hardware computer interface for the L1011. Now THAT is a while ago.

If you need some really esoteric designs, ask me. I've invented some very unique magnetic field circuitry technology that has applications in "monitoring". The circuitry/design is very sensitive, makes products that pass Tempest testing look like leaky sieves. Actually, the circuitry rivals SQUIDs in the field for sensitivitiy and S/N, but the circuitry is a lot more user friendly, not requiring liquid nitrogen, etc. For example, using the circuitry, you can "tap" a phone line from three feet away. The circuitry intercepts so little power that it is impossible for anyone to detect that you're tapping the line.

- Robert - macy ..AT.. california ..DOT.. com

I have your absolute source . . . the people who now own Boston. I worked contract for them for a little while helping to redesign the 1900 and several other models. The company is Elmers -- yes, as in glue -- and the Boston brand has now changed to X-Acto -- yes, as in cutting blades -- which Elmers also owns. Their engineering is located in Statesville, NC and I'm pretty sure I can get them to send you a gear, although you'll have to tell me whether it's the large central gear directly behind the cutters or the smaller peripheral gear. You'll have to email me directly with your contact information (see my Web site for a good email address) which I will pass on to the right people with a request. But why not just go out and buy another pencil sharpener? They're pretty cheap.

Mark 'Sporky' Staplet>

Dear Sporkman:

"Sporkman" wrote in message news: snipped-for-privacy@bigfootDOT.com...

Agreed. I have a terrifying story about the use of "Marvel Mystery Oil" in air system lubricators too.

David A. Smith

Mark,

Thank you, thank you, thank you.

I went to your website and got your direct email address [info ..AT.. h2omarkdesign ..DOT.. com] using the same subject line as here. So you should get my contact information. If not, please email directly: macy ..AT.. california ..DOT.. com

The gear is the approx 2 inch diameter on the cutter blades. Broke in half and pretty bald on one of those halves, too. I never used any lubrication on this gear - never thought to do that. But thank you for the "heads up" on WD-40. I have noticed how it likes to gum up severely over time.

With the manual "twisty" sharpener working so well, it's not likely I can get the purchase order through now.

Look forward to confirmation you received my contact information.

- Robert -