New Carriage Spur Gear

Has anyone reproduced the carriage drive gear for a Round Dial 10ee? I don't know how many models take the same gear but I would guess quite a few. I am needing one and was about to get a quote on a gear cutter to make one but if someone made a few I would rather buy than make. Just to clarify I am talking about the gear sticking out the back of the carriage apron that engages the rack. Apparently the rack teeth are quite hard and the spur gear is softer because the rack teeth look like new but the gear not so much. Mine is a 1945 Round Dial and the gear in question has 15 teeth. Outer diameter (tooth to tooth) is approx. 1.28". The root diameter is approx. .954". Also if the exact specs for this gear are known that info would be helpful to get the cutter quoted.

I could make you that gear, but if the round dial is the same as my square dial the rack pinion is integral to the shaft. You could always turn the teeth off the shaft and press a new gear over the shaft. If you can convince yourself that the actual circular OD, which is difficult to measure on an odd tooth gear, is 1.214 the it would be a 14 Dp, 15 tooth gear. Easy to make on the Barber Colman. The next size up would be 13 Dp, which is an OD of 1.307, but 13 Dp is a oddball size. Ash Gear does have 13 pitch hobs, but its going to be harder to find a shop who already has a 13 Dp hob.

I have one of the gears here, I cannot remember if it is the one out of my 10EE or the second hand replacement I got from a square dial that was being wrecked. But it is just a gear on a plain stub shaft with a woodruff key in it. The thing will be what pressure angle the gear is. It could be an odd bod DP as well. Pressure angle is easy to measure if you have the rack off as it is the rack angle. You could measure the rack angle on an optical comparator for best results. I have a rack here that might be off a monarch lathe. If it fits the gear I have, I could measure the rack angle.

The square dial rack is 14dp, I'd bet that the round dial is the same. Not sure about interchanging the saddle pinion between types but I've got one beat to hell you can have if you want to check things.

This is actually a HIGHLY modified tooth profile 14DP gear. I have to make a few but have been holing off for not having had the time to properly measure the center distances or have an unadulterated sample to interrogate. If someone is willing to lend a good sample for the interrogation, I would be happy to compensate them for the effort. Monarch used standard gears where they could, but they were not shy at all about using MTPs or Profile Shift. ( which is more common than not in the larger world )

Here is mine. Note the unworn portion of the gear inboard of where the rack contacts, that is where I have the calipers. Since 15 teeth have 24 degrees between them, easy to take the measured 1.2805 and calculate a radius of .6473 and a diameter of 1.2946.

Since standard 15 tooth 14 pitch has an od of 1.2143, the profile shift is .0402, which is, as ZK says, is pretty significant. I don't have a 14 DP hob, maybe ZK has one.

If he doesn't have one or have the time right now, I would be willing to make one for you if you bought the hob and the material.

I measured the rack I have that I was told was to fit a 10EE although it is a bit different to the one on my lathe in that it is one piece and the tapered pins and cap screw holes are opposite. Other then that it looks the same and fits the gear I have.

The pressure angle of the rack is 14.5 degrees and the pitch is 5.7mm which is 14DP. So you will need a 14DP 14.5PA cutter.

bll230 said:

Since standard 15 tooth 14 pitch has an od of 1.2143, the profile shift is .0402, which is, as ZK says, is pretty significant. I don't have a 14 DP hob, maybe ZK has one.

Click to expand...

Not one. We have Three 14DP Hobs. Too easy to get caught with one needing sharpening while a job sits waiting. All of our Hobs are ClassAA or ClassA. ** Typically, I will not purchase anything less.

**- There is One ClassB and One ClassC Hob in the building. They were purchased solely because the customer insisted on using them because their prints specified them and explaining the irrelevance of the choice was proving futile. They sit on the shelf for that customer's jobs and I don't use them for anything else. I prefer to use the best I can for a given part.

And, not to be arbitrarily pedantic, but my calculations show that if we accept the assumption of a 1.2805" Tip Diameter, then the resulting Profile Shift is actually .0331". ( still significant ) Tooth thickness on such a sample would be 1.2932" and MOW would be 1.27543" using .1234" wires.

This is important because we don't want to create a situation where the Pinion ends up in tight mesh with the Rack, causing pressure and stiff operation. Nor would it be desirable to go through all the work and effort only to have it end up being sloppy...

Late to the party, the gear and rack are completely interchangeable between round dial and square dial machines. The racks actually look like they were made on the same machine, as I butted up a pristine round dial front against the unworn back half of a square dial and they matched perfectly. The original spur gear is indeed one piece with its shaft and don't remember if that includes the large internal apron gear, but this is also identical and can be swapped complete.