Question on gear change to slow feed rate.

[GreggC]

Hey guys,
So, my feed rate is too fast, its .0047 and if I want a really nice finish I have been hand feeding.
I got to thinking,
Gear "B" drives the gear box that drives the lead screw.
Gear "B" is a 60 tooth gear,
My question,
If I increased the size of gear "B" wouldn't that slow down the lead screw in turn slow down the feed rate ??

 

[rgray]

Most certainly. That or A gear smaller.

 

[GreggC]

Most certainly. That or A gear smaller.

Way easier to change the "B" gear,
In fact the parts list shows my lathe came with a stack of gears and one is a 80 tooth
Item 123, Im gonna try it when I get off work.

 

[British Steel]

If the compound gear (120/127?) shown as intermediate is two separate gears, you could swap the B gear and its mate around and get a pretty substantial reduction - they may be permanently attached, though (if you could do it, you wouldn't even have to fiddle with the banjo...)?
That does suppose that they're on identically sized shafts, with identical keys...

Dave H. (the other one)

 

[GreggC]

If the compound gear (120/127?) shown as intermediate is two separate gears, you could swap the B gear and its mate around and get a pretty substantial reduction - they may be permanently attached, though (if you could do it, you wouldn't even have to fiddle with the banjo...)?
That does suppose that they're on identically sized shafts, with identical keys...

Dave H. (the other one)

Yeah, fitment might be an issue.
But, yes, big time reduction.

 

[RJSakowski]

On my G0602, I run a 27 tooth gear in the a position, replace the 120 tooth gear with a 36 tooth, and put the 120 tooth gear in the b position. My gear box is run in position II C. This gives me the slowest possible feed rate using stock gears, .00139"/rev.

 

[GreggC]

On my G0602, I run a 27 tooth gear in the a position, replace the 120 tooth gear with a 36 tooth, and put the 120 tooth gear in the b position. My gear box is run in position II C. This gives me the slowest possible feed rate using stock gears, .00139"/rev.

I tried Dave's idea trading the 120 and the "B" gear,
Didn't work, the 120 was too big and hit my bench.
I ordered a 80 tooth gear for the "B" spot.

 

[savarin]

On my 9x20 if I want slow feed I just do as you have suggested.
Swap the 120 with the gearbox gear and the banjo does not need re-adjusting, if I want slower then I use the smallest change gear in place of the 120 with the 120 on the gearbox, this usually needs a banjo adjustment.
I cut a lot of M# x 1mm threads so I usually leave those combinations set up and swap to the lower feed as required.

 

[GreggC]

On my 9x20 if I want slow feed I just do as you have suggested.
Swap the 120 with the gearbox gear and the banjo does not need re-adjusting, if I want slower then I use the smallest change gear in place of the 120 with the 120 on the gearbox, this usually needs a banjo adjustment.
I cut a lot of M# x 1mm threads so I usually leave those combinations set up and swap to the lower feed as required.

Does the 120 hang below the lathe and hit the bench ??

 

[RJSakowski]

I'm guessing that you have a G4000 or clone. If you run the 60 tooth gear in place of the 120 tooth gear and the 80 tooth gear in the b position, you should get down to .00176"/rev. You may be close to hitting the bushing behind the 80 tooth gear with the 127 tooth gear. If you have interference, swap the 120 tooth gear for the 127tooth gear and you should be good. That would increase the feed rate to .00186/rev.