Gears...

[vimes1984]

Hey all,
I own a mini conquest lathe:
https://www.amazon.co.uk/Chester-Machine-Tools-Hobby-Store/dp/B079S9KRNW

And I have broken two gears that connect the spindle to the autofeed, these are the exact replacements:
https://www.arceurotrade.co.uk/Catalogue/Machine-Spares/C3-Mini-Lathe-Spares/C3-39-Pinion-25T
https://www.arceurotrade.co.uk/Catalogue/Machine-Spares/C3-Mini-Lathe-Spares/C3-41-Pinion-20T


I have two questions regarding this:
1) I'd prefer not to buy these but make my own, is there a jig/rig I can purchase for the mini lathe to cut gears? ( I've been reading they are called "hobbing" machines but I can't seem to find a place to either buy or a detailed build tutorial.
2) If I do have to buy them I'd prefer to buy them in steel rather than nylon, does anyone in europe know where I can get them?

Kind regards
Chris

P·.S I'm REALLY new at this go easy

 

[markba633csi]

You may want to stick with nylon since the factory often intends them to be "sacrificial" gears; if you crash the machine they break first rather than something else more expensive. They don't look that expensive- 6 pounds or so is a relative bargain I would say
Gears are usually cut on a milling machine, it's possible on a lathe but more difficult especially if the lathe is small and lacking rigidity.
I believe hobs are used for helical gears not straight cut gears? Check the internet for more information
Aluminum gears would be much easier to make than steel.
Mark

 

[RJSakowski]

Cutting gears requires some specialized tooling as well as advanced machining skills. It is possible to cut the gears on a mill with the hobbing cutter or with a form tool bit in a fly cutter but you will need an indexing tool such as a rotaey table, or a dividing head to precisely rotate the blank to cut each tooth. There have been a number of articles in various forums and on You Tube which should give you an idea as to what is involved.

You should be able to find gears from other sources although you will need some additional information. namely, the module and the pressure angle.

I would reconsider replacing the Nylon gears with steel or other metal. By doing so, you have moved the weak link to another component in the drive train and most likely a much more expensive one to repair or replace. The cost of the gears from your suppluer isn't that great. If you are concerned about the inconvenience3, you can buy some spares.

 

[markba633csi]

Oh by the way, how did you break them in the first place? Might you have too much friction in your carriage? Gibs too tight?
Or was this the result of a crash?
mark

 

[coherent]

You may want to stick with nylon since the factory often intends them to be "sacrificial" gears; if you crash the machine they break first rather than something else more expensive. T
Mark

I'll second this advice. When I got my very first mill I also just assumed that getting some metal gears would be better and that the plastic ones were just included to save money building the machines. I later learned that they include plastic or nylon gears so that in the event of a crash or excessive friction they go instead of damaging a shaft, spindle, bearings or other part that would be much more trouble and expense to fix. If you really want to make them, make them from a similar material, or if you can, find a cheap source and keep a few in stock. If you are having to replace it often and you didn't have a crash, you most likely have an issue with something else causing the excessive wear.

 

[vimes1984]

that makes perfect sense!
They must be sacrificial gears, I switched it from high to low whilst it was running.... STUPID idiotic mistake on my part....
I'll buy the ones from this source now
I did assume that they where just cheap since the threading gears beneath them are also plastic and I've seen those been replaced in multiple places online but I have never seen these been replaced...
I am VERY interested in being able to create/hob gears on lathe though, what would be involved ?
I've seen indexing wheels and hobbing / flywheel cutter, to be honest I've seen LOADS of different setups for gear cutting on the lathe but I haven't been able to find what seems like a tutorial on how to do it from scratch...
Nor what the pro's/ cons of each method are...
Thank you guys so much for pointing me in the right direction, I was about to make another stupid mistake !!!

 

[ttabbal]

The people I've seen cut gears on a lathe do it with a milling attachment and some way to index the work. Some of them are pretty simple and work well enough. I think the biggest reason you don't find a tutorial on it is that it's not commonly done. There are some videos on YouTube that show the process.

 

[francist]

This takes away from your fun do-it-yourself project, but there's been a few guys lately fooling around with 3D printing replacement change gears for smaller lathes. Can't remember how they held up, but I'm wondering if your original gears are plastic (nylon) anyway would a printed version be somewhat comparable? Just a thought, I know extremely little about 3D printing.

-frank

 

[vimes1984]

@ttabbal is there any reason for this: "that it's not commonly done" ?

 

[silence dogood]

Another reason that plastic gears are used is that they are quieter and they generally are self lubricating. On the larger and more expensive lathes, a shear pin is usually place in the lead screw.