Gear Cutter Questions

Martin W

Martin W

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I am making a spur gear for a friend for a 100 year old sausage maker/ meat grinder. I thought it would be fun and gain experience, as I have never cut a gear before. An old guy I know says you don't cut a gear you hob one. I have seen videos of hobbing but I think I will just start out by cutting one on the mill and dividing head.
My gear will have to have a pitch diameter of 3.250" and 18 teeth. I want to order a cutter. I figure I need a #6 cutter? Some cutters from the Ukraine and USSR and China are # 3. They also have a 22mm dia. bore. There are a couple of Butterfield cutters on Ebay that are reasonably priced.
Has anyone ordered a China or USSR cutter before? Are they cheap because of cheap materials? I can make a 22mm arbor.
Are all gears 14.5 degree pitch? I have seen 20 degree cutters also?
Thanks
Martin W
 
Most of the older machines used gears with 14.5 pa and 20 degree gears are more modern. Should be able to measure the angle on the mating gear, though if it's 100 years old you can bet it's 14.5. Many gears have been cut on dividing heads. I'd say a Chinese cutter would be ok more so if you're cutting only one gear. Are you making it out of ductile or cast? If so, that cuts pretty easy anyway.
 
Get you some good cutting oil such as Mobilmet 766 or good old dark smelly cutting oil and keep the cutter soaking wet with it. The foreign cutters should work fine. Just don't cut dry. Ken
 
I have not seen many bad reviews of Chinese gear cutters, and the ones I saw were refunded or replaced. I have not seen bad reviews of USSR tooling at all. You absolutely need to know what diametral pitch and pressure angle you have if you are matching an existing gear. You also need the tooth count. Machinery's Handbook has the information you need, including full size tooth profiles in my 22nd edition.

Not all gears are hobbed...
 
Watch out for numbering systems. I have seen Chinese cutter sets that were numbered backwards from the standard in this country.
 
That can not be a DP module gear if the PD is 3.25.

Pitch Diameter is the number of teeth divided by the Diametral Pitch

An 18 tooth 6 pitch gear will have a pitch diameter of 3", an 18 tooth 5 pitch gear will be 3.6"
The pitch diameter may be measured over wires using the handy tables in Machinery's Handbook.
I suggest that you do so before starting.

186dpgear_zpsewofpi63.jpg
 
Last edited:
Thanks, I will do that
Wreck™Wreck said:
That can not be a DP module gear if the PD is 3.25.

Pitch is the number of teeth divided by the Diametral Pitch

An 18 tooth 6 pitch gear will have a pitch diameter of 3", an 18 tooth 5 pitch gear will be 3.6"
The pitch diameter may be measured over wires using the handy tables in Machinery's Handbook.
I suggest that you do so before starting.

186dpgear_zpsewofpi63.jpg
Click to expand...
 
Good luck with it that will be around 3/8" depth at the root, I hope that you have a stout machine.
 
in general russian cutters are okay, chinese might be
you might want to consider taking out the heart of the tooth with a regular cutter before using the gear tooth cutter
 
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