Gear cutting question

Fritz Maurer · Feb 18, 2018

A guy on you-tube was cutting a gear about 2" in diameter on his lathe. He had what looked like a ring gear attached to the spindle with a locking device to enable him to lock the spindle in any position, like you would with an index head. He said that because the ring gear was "correct numerically", he was able to cut the little gear that was mounted in the chuck. He did not explain that little detail. How is a gear calculated to determine whether it will index properly for cutting gears of other diameters?

Mike(NEOhio) · Feb 18, 2018

I've seen that one. He uses a stock gear fastened to the back end of the spindle. As long as that gear has the same number of teeth, or a multiple number, it will cut the desired number on the new gear. The gear on the spindle only provides the degree of rotation. The new gear can be a different diameter and diametral pitch. Hope you understand this explanation.

JD Seller · Feb 19, 2018

How do you cut a gear on a lathe???? I have only seen them cut on a mill.

Moonlite37 · Feb 19, 2018

Just power the cross feed and use like a shaper, I do not think a shaper is used in a modern machine shop,

BarnyardEngineering · Feb 19, 2018

The number of teeth is what counts. Diameter doesn't matter.

This is because the dimension we are interested in is the angle. Each tooth of the gear rotates the spindle through a certain angle, and that angle will be the same whether the gear is 2" in diameter or 8" in diameter or 24" in diameter.

I've also seen people using circular saw blades as indexing plates on a lathe to cut gears. A 40-tooth saw blade for a 40-tooth gear, for example.

DR. EVIL · Feb 19, 2018

Cutting a gear on a lathe indexed off a smaller gear with the same number of teeth seems like a Very imprecise method of machining/manufacturing. Proper method of cutting gears is with a cutter called a hob. Mitsubishi also includes a very accurate gear cutting programming package in their wire EDM machines. You almost don't have to do any secondary gear tooth machining and finishing operations with the EDM gears.

We had a machine at FARMALL called a Shear-Speed gear former. Machine took a stack of gear blanks, already turned and center bore turned or broached. The machine had a specially ground cutter for each space between gear teeth. A cutter head held the cutter teeth, and the machine advanced the cutters about .001"/.002" into the gear blanks on each stroke. The gear teeth still needed finishing, normally "Shaving", oon a Red Ring Gear Shaver. We also had a bunch of small Barber-Coleman gear hobbers for small pump gears we machined from blanks supplied from West Pullman Plant. One machine ran one part number. We ran that machine when we needed that part number and it sat unused until we needed more.

Oliver 500 Wa · Feb 19, 2018

Cutting a gear on a lathe indexed off a smaller gear with the same number of teeth seems like a Very imprecise method of machining/manufacturing. ....

Absolutely. Would not work in a production sense. For a repair or restoration job it might be good enough and the only economical way to get the part made.

Sometimes indexing is done on the second change gear on the back of the spindle. Because of the ratio between the first and second change gears you can index the spindle to points that don't exactly match the count on the main gear.

Fritz Maurer · Feb 19, 2018

Thanks, Mike I picked it up after I read it a couple times. The "multiple number" was the clue I was looking for

Gear cutting question

Fritz Maurer

Well-known Member

Mike(NEOhio)

Well-known Member

JD Seller

Well-known Member

Moonlite37

Well-known Member

BarnyardEngineering

Well-known Member

DR. EVIL

Well-known Member

Oliver 500 Wa

Member

Fritz Maurer

Well-known Member

Similar threads