Where to find spur gear

I picked up a old canedy Otto drill press with a gear drive system on the electric motor. The gear itself is trashed, I want to keep this as original as possible as I rebuild it and was wondering if anyone can point me in the direction for a replacement gear for the electric motor?

Below are some pics that I uploaded so you can see the gear.

3 B43 B2 F 4962 4 E98 ACA7 9255 CFC EEE2 — imgbb.com
115 EB E8 FA5 4 E7 8 C67 43 FAAC75 A976 — imgbb.com
59 C69 A68 6 EB3 4334 A925 1 A5 A454727 A5 — imgbb.com
3 EBA3 C1 49 A4 44 D4 A259 F444354 A1 F6 — imgbb.com
FDB7 D AA 34 E7 4146 9 B9 C 5 DBA57 C B2 C2 — imgbb.com

Amazon sells Boston brand gears. You have to get the diametral pitch and number of teeth, then see if Boston makes one the right face width.

Larry

A good selection at Boston Gear:

Spur Gears & Rack | Open Gearing Products | Boston Gear

I’ve been tearing my hair out trying to figure out pitch etc, here is what I have so far.

1.2 inch face
1 inch bore
2.8 outer diameter
24 teeth
And that’s where I get lost, I still can’t figure out how to get pitch out that.

im in a similar situation right now working on a planer, the pinion driving the bull gear has been pretty trashed at some point and (poorly) repaired, with the repairs now failing I decided it was new gear time, so today I measured the gear and found the pitch and figured the pressure angle, counted the teeth and went looking, eventually I found the part numbers for the needed gear both from Boston gear and from Martin, I’m sure browning probably makes it too, I went looking online and have found one for about half the price of most other places.

This machine is over 100 years old and I can get an off the shelf gear for it! How cool is that?

Once you have the part number do some googling and scour eBay and Amazon, you can often find gears as surplus for much less than list price, I got some bevel gears for a machine for less than 1/4 the list price a few years ago, spur gears have been pretty standard for a long time now and those don’t look like anything special. Only other thing to say is expect to have to bore it and cut a keyway if needed, or bush it if it’s too large, but hey that’s a lot simpler than repairing the old gear or making a new one.

This seems close, but too small an OD: Boston Gear YF241 Spur Gear, Steel, Inch, 1 Pitch, 1." Bore, 2.6" OD, 1.25" Face Width, 24 Teeth: Amazon.com: Industrial & Scientific

Can you get some additional measurements, like width of the root of an individual tooth, height of a single tooth, etc.? Any adjustment on the motor mount so that a decent mesh might be made with a slightly smaller gear? You'd have to be sure you're not risking the driven gear...

To find the pitch is easy, add 2 to the number of teeth and divide by the diameter then round to the nearest whole number, in your case 24 teeth +2 is 26 divided by 2.8 = 9.285 round that down and it’s a 9 pitch gear

So you need a 9dp gear 24 teeth and a 1.2 face width or wider you can face it to length, you can probably get away with a bit narrower too, your new gear will probably be steel while the old one was likely cast iron.

Pressure angle is another matter could be either 20 or 14 1/2 this can be told usually by just looking at the tooth profile, 14 1/2 half will usually have a more square root while 20 will usually be more rounded and a more pointy looking tooth.

Thank you Rusty old tools! You just saved me hours of hair pulling!

I'm pretty sure you need to measure the center distance to calculate the pitch. I use metric (module) for clockwork and the module = (2 X CD) / (total number of teeth in both gears)

Rusty tool's method for calculating the pitch is, I believe, an approximation as you can't measure the pitch circle diameter directly.

Appears to be what's left of a "fiber" gear. This was done to cut down on noise

To make this less of an "approximation" also apply the counting, measuring and math to the large gear

As far as finding pitch, not an approximation - assuming what is there to measure is in good shape - and is actually a gear and not a sprocket

Is the last photo showing us a gear guard or is that perhaps a chain?

rusty old tools said:

To find the pitch is easy, add 2 to the number of teeth and divide by the diameter then round to the nearest whole number, in your case 24 teeth +2 is 26 divided by 2.8 = 9.285 round that down and it’s a 9 pitch gear ...

Click to expand...

The 'rounding down' part can be a problem. It should come out right on the number or at least very close, like 9.02 or 8.985 or something, then you can be confident it's really 9 DP. When it's this far off it's a 'maybe' -- maybe spread teeth, maybe actually a different pitch, maybe the od got butchered somewhere along the way, maybe maybe maybe.

But it gives a good starting point and if you don't have any other measuring tools and the replacement part is cheap, you can go for it.

You can actually measure over the teeth with wires, similar to threads, and for this the wires don't have to be very accurate. The formula should be on the internet somewhere, it's also in my calculator but I've totally forgotten how to retrieve it. Anyway, you can use that as a check against your initial guess.

If you have to do this more than once a year, a set of gear gages was only about $25. Got mine from Browning, you roll them against your gear and that will give you another check point. They are also good for 14 1/2* vs 20* estimating. (Sorry if they are more now, everything is more now. A lot more now )

(I can't see your photos so kinda feeling the elephant here but ... )

edit : here, like these. But $65 ? Maybe they are cheaper direct, fleabay people sometimes love their stuff too much :

BROWNING STAINLESS STEEL GEAR TOOTH GAUGE 15 LEAVES, 12 SIZES, 2 PRESSURE ANGLES | eBay

John Oder beat me to the punch. A lot of the older open gear drives as used on this drill press used gears made of "Micarta" ( a composite material made of layers of canvas & phenolic/aka Bakelite resin). The pinions were often made of this material, or sometimes stacked and laminated rawhide was used. This eliminated some of the noise of open spur gears, took shock loads, and served as the "sacrificial" gear. Instead of wearing out an expensive bull gear (usually made of cast iron or cast "semi steel"), the pinion was deliberately designed to wear out first.

If you change gear materials on the pinion, particularly if you go to steel or stainless steel, you will likely wear out the bull gear at an accelerated rate.

I'd look for a bronze pinion if you cannot find one made of "Micarta" (Westinghouse's name for this material) or "Ryertek" (Ryerson;s name for the same material).

Spur gears are designed using simple formulas, and if you do not own a "Machinery's Handbook", you should be able to find these gear design formulas on-line. The big "if" in this matter is whether the gearing is 14 1/2 degree or 20 degree pressure angle. Both pressure angles are pretty much commonplace for spur gearing tooth design, and without knowing which pressure angle your gearing is, you can do some real damage by getting a pinion for the wrong pressure angle.

My old Cincinnati-Bickford camelback drill has the original motor drive on it, using a pinion on the motor and a bull gear on the lower cone pulley shaft. The motor pinion looks to be either laminated paper (commonly used in the 20's for pulleys and some gearing), or possibly laminated rawhide. It makes for quiet running gearing.

I am fortunate in that I have a stash of cutoff chunks of 2" thick Micarta. This is the stuff to make a new pinion out of, should the need arise. Cutting a spur gear pinion is not difficult if you have the right machine tools and tooling. A dividing head and tailstock, and the right gear tooth cutter along with a lathe and milling machine are needed.

As I said, I would not be in a rush to put a steel or stainless steel pinion on your drill's motor. The material is too hard for the application. It will work, but the price will be noisy operation and accelerated tooth wear on the bull gear.

If you figure that some may have been worn off the gear, and that the OD may have been bigger by 50 thou, then the 9 looks better.

The picture links do not work.

But depending on where the gear is, there is also the possibility that it is a "stub tooth" profile, which means the OD will not correspond to a relevant pitch. Those are often used for better strength, and may not even have been per a standard.

The PD is the same, but the tooth is not as tall, so the usual formulas do not apply. The tooth height might correspond to the next smaller DP, so the DP might be called a "10/12" meaning an otherwise 10DP gear with a tooth height appropriate for a 12DP (smaller tooth).

I believe stub tooth are generally 20 degree gears.

JST said:

I believe stub tooth are generally 20 degree gears.

Click to expand...

For future reference, you are correct. Not just generally but always (as soon as you say that someone somewhere will come up with an exception but ...) Fellows invented them, I think, and they are now considered to be the wrong idea.