change wheel selection

Gallery, Projects and General > How do I??

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John Stevenson:
I think we are missing some information here not given by Dave.

He says he has a 34 driving a 21 tumbler set up and then a 54.
If that is correct then that 54 cannot be changed or it will not mesh with the tumbler gears.

What I suspect is that the 34 runs with the tumbler gears and there is another gear behind the 54 that is always in mesh, possibly another 34 to cancel out the first set of ratios ??

Without a better explanation or picture we are flying in the wind.

John S.

DavidA:
JS,

Nope, It's as I stated at the beginning. 34 on the spindle, The tumbler (reverser) consists of three 21 tooth gears in a sort of tringular formation to allow for forward or reverse. But as they are all 21 tooth they can be treated as one gear; only the direction will be effected.
This 21 tooth gear drives the 54 tooth directly, nothing fixed to it.

As most of you mention, changing the 54 for a 34 will simplify things .
If it can be made to mesh with the tumpler gear, say using a banjo,then I could then use the constant trick to get

Leadscrew threads per inch X constant /threads to be cut per inch X constant.

If I use 5 as the constant I would get

6 x 5 = 30 and 8 x 5 = 40

or put another way, 40 teeth on the leadscrew and 30 teeth on the stud. The 30 would be driven from the back of the 34 already on the stud. i.e. keyed together.

I may have to add another 34 or 30 as idlers.

I think.

Dave.

andyf:
Yes, Dave, if you can equalise the spindle and stud gears, it would help a lot. Then, as you say, a 30T on the stud and a 40T on the leadscrew with an idler to fill up the gap between would result in one full turn of the spindle imparting three-quarters of a turn to the leadscrew, and give you 8tpi.

Whatever gear combination you adopt, the gears are going to be expensive if they are only for a one-off job!

As a matter of interest, what sort of lathe is it?

Andy

Fergus OMore:
Some of us have guessed what you are using but none of us know what gears are left to use.

Perhaps a bit more information is called for.

DavidA:
AndyF,

What kind of lathe. Now that is a good question.

The answer is, I don't know.

I did a piece on here about it some time ago where I covered my repair to the tailstock.. I think I entitled it 'Mystery lathe' or something similar. I'll try to find the article and link to it.

I'm going to have a go at making the required gears. Can't afford to buy at the moment. I'm sure I can dig out some suitable scrap from work. may have to be made from steel and aluminium alloy though.

Fergus,

I'll have another root around my bits to see what other gears are available. Whatever shakes out in the end it will be a mixture of half 20 dp and half 18 dp gears. Obviously not running together.

I definately will be trying to adapt to having equal gears on the spindle and the stud. No point in struggling.

Thanks for all the help so far guys,

Dave.

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