What are the effects of material on gear noise and wear?

[dabear3428]

like the title says what tradeoffs are involved in making a gear from brass vs steel vs plastic?

 

[RalphF]

If all the gears are cut properly to specifications, the difference would be in the strength and wear characteristics of the gears. You can find all this information in the current version of The Machinist Handbook. There is a section on gear loads and gear materials for different purposes, and heat treatment of various steel types relating to gears and what application you intend to use your gear on.

 

[WobblyHand]

Noise and life time are two. I've used plastic gears and they are much quieter. Haven't worn them out yet but they probably won't live as long as steel or cast iron. Plastic ones are easier to make simply because you can mold them or print them. Usually cheaper as well.

 

[Ulma Doctor]

Brass gears are mostly used for clockmaking and watchmaking or other low torque and low friction applications. They run quietly.

Steel gears are used for when high torque and high loads are required.
They run louder than brass gears

Plastic gears are used in low torque and low loads are required . They run quietly and are the least expensive of the materials mentioned

 

[francist]

Years ago, when things like hand cranked forge blowers were still being made, they often incorporated one synthetic gear in the train. At that time the material was a cloth-impregnated phenolic. Advertising of the day for these blowers often touted the “silent running” train due to the addition of this one gear.

Singer sewing machines did the same thing with some of their higher-end machines like the 201, 301, etc. In addition to regular steel bevel gears there was one phenolic gear to transmit power at the handwheel. Their material was called “Textolite”, but it was essentially the same cloth-impregnated resin. These gears, in addition to being exceptionally quiet, required little to no lubrication. Pulling apart a machine today, after 100 years of service, these gears are often in mint condition with little to no wear. I’ve got a number of machines with the Textolite gears and they all run beautifully.

So, in addition to load characteristics, you should probably consider noise and lubrication requirements when looking at gear materials as well. With modern plastics (acetal, eg) they’re quite happy to run dry but steel or bronze not so much.

 

[jwmay]

like the title says what tradeoffs are involved in making a gear from brass vs steel vs plastic?

You’ve gotten good responses so far, but it might help to know what you want the gear for.

 

[projectnut]

To add to Ulma Doctor's response, plastic gears are also often used in applications where there is a potential for a crash, such as in a lathe headstock. One gear in the mix is often plastic and is considered to be sacrificial. If/when a crash should occur the plastic gear will probably be destroyed, but the more expensive steel, cast iron, or brass gears will remain intact. My Sheldon lathe has a phenolic gear in the headstock for this very purpose.

 

[dabear3428]

You’ve gotten good responses so far, but it might help to know what you want the gear for.

I have a mini mill G0758 that has a H/L shift in the head and it has all plastic gears 1 outside of the head but 2 that are inside the head and a PITA to replace, I'm investigating upgrading the motor and will need to address the plastic gears since they break even with stock power. no one makes steel replacements and I think i can build them myself but just trying to get an handle on noise/wear/strength for the materials. there is one gear in the mix that is easily (relativity) to replace and i may make that one sacrificial. i'm also looking at changing the ratios. i could do a belt mod but i like being able to switch H/L on the fly.