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Hukshawn
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Gordon Livingston
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Hukshawn
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On the money, sir. 64 turns in 16tpi came out to 4.200... give or take a few thou...
While we are on a roll, could we try the same 64 turns but at 10 TPI settings and measure carriage travel?
Needless to say that all backlash has to be taken up before marking the start.
Anybody want to predict the result?
Sorry about the comma's, I am still having trouble with my French keyboard but as Red Green would keep telling his wife ''I can change, I think''.
Needless to say that all backlash has to be taken up before marking the start.
Anybody want to predict the result?
Sorry about the comma's, I am still having trouble with my French keyboard but as Red Green would keep telling his wife ''I can change, I think''.
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Hukshawn
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There would be a comma between I can change, and, I think. hahaha....
Yur right!
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Hukshawn
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Sorry... lol
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Short version:
Tozguy is spot on. Replace the 51T gear with a 54T gear and you will get Imperial threads so close to perfect you won’t know the difference. Without altering the gear box or the leadscrew.
Long version:
When the metric leadscrew (3mm pitch) was replaced with an Imperial leadscrew (8 TPI = 3.175mm pitch), the carriage moved farther for each revolution of the leadscrew than it did originally, which means it also moved farther for each revolution of the spindle than it did originally. To correct that error, the original 34T gear was replaced with a 32T gear to slow the leadscrew down when cutting metric threads. With the 32T gear, the 3mm gear box setting actually results in a 2.988 mm thread. The 1mm setting will produce a 0.996 mm thread. And so on. Plenty close enough for government work.
The original 51T gear hasn't been changed, hence the lathe still cuts Imperial threads with too much pitch. To get it back on track for Imperial threads, you need to replace the 51T gear with a 54T gear. That will result in a thread with so little error that it’s practically immeasurable. Something like 15.99+ TPI for the 16 TPI gear box setting.
I think the thread dial, as is, will be useless for both metric and Imperial. You might cut an 8T or 16T gear and get it to work for Imperial threads, but I think you're stuck with leaving the half nuts engaged to cut metric threads.
Tom
Tozguy is spot on. Replace the 51T gear with a 54T gear and you will get Imperial threads so close to perfect you won’t know the difference. Without altering the gear box or the leadscrew.
Long version:
When the metric leadscrew (3mm pitch) was replaced with an Imperial leadscrew (8 TPI = 3.175mm pitch), the carriage moved farther for each revolution of the leadscrew than it did originally, which means it also moved farther for each revolution of the spindle than it did originally. To correct that error, the original 34T gear was replaced with a 32T gear to slow the leadscrew down when cutting metric threads. With the 32T gear, the 3mm gear box setting actually results in a 2.988 mm thread. The 1mm setting will produce a 0.996 mm thread. And so on. Plenty close enough for government work.
The original 51T gear hasn't been changed, hence the lathe still cuts Imperial threads with too much pitch. To get it back on track for Imperial threads, you need to replace the 51T gear with a 54T gear. That will result in a thread with so little error that it’s practically immeasurable. Something like 15.99+ TPI for the 16 TPI gear box setting.
I think the thread dial, as is, will be useless for both metric and Imperial. You might cut an 8T or 16T gear and get it to work for Imperial threads, but I think you're stuck with leaving the half nuts engaged to cut metric threads.
Tom
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Hukshawn
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Awesome explanation.
So the magical solution is a 54t gear.
You guys that have all this figured out, can you design a gear? I will have it made somewhere. the shop I bought this lathe from (he said he never used it, just sat there) could likely do it, time pending.
So the magical solution is a 54t gear.
You guys that have all this figured out, can you design a gear? I will have it made somewhere. the shop I bought this lathe from (he said he never used it, just sat there) could likely do it, time pending.
Sitting here wondering where did the 32T gear come from and where is the 34T gear at.
Scratching my head here wondering where the original metric dial gear is and where did the 14TPI gear come from.
Why would someone modify a metric lathe that does both mm and inch threads, to one that only does metric pitches?
Would the previous owner let you rummage around his shop looking for any spare gears that belong with the lathe?
Re the thread dial gear, 16.0T or 32.0T would be my choice. Either one will get your nuts to work for inch threads.
Agree about no half nuts for mm threads, the 8.0 TPI lead screw just does not sync with metric. There might be a convoluted way to use the half nuts for metric threads but I'm too old for that.
Scratching my head here wondering where the original metric dial gear is and where did the 14TPI gear come from.
Why would someone modify a metric lathe that does both mm and inch threads, to one that only does metric pitches?
Would the previous owner let you rummage around his shop looking for any spare gears that belong with the lathe?
Re the thread dial gear, 16.0T or 32.0T would be my choice. Either one will get your nuts to work for inch threads.
Agree about no half nuts for mm threads, the 8.0 TPI lead screw just does not sync with metric. There might be a convoluted way to use the half nuts for metric threads but I'm too old for that.
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Hukshawn
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those are very good questions. its not missing any other parts, so to say it was a parts machine doesnt really fit.
i just wrote to the guy i bought it from asking if there are any parts left behind.
Id like to note, when i took apart the thread dial, i did notice a spacer ring under the gear. about the width of a gear... so i wonder if it originally had two gears or could have two gears.
given the space within the thread dial housing, a 32t gear might be a bit big. however, the dial has 4 numbers. which would be preferred with 4 numbers?
if i can get this machine to do inch threads, i can say with a reasonable amount of certainty, i will not be making any metric threads unless i have to for some reason. so, not being able to use the half nut in metric is not a concern.
if i cant find a gear via the previous owner, how can i sort out the dimensions of a new gear? i wouldnt even know where to begin designing a gear. but I'm sure I could make one.
would the use of a indexer help? i saw a local guy on kijiji selling one for a decent price. im sure i could fandangle onto my lathe some how...
http://www.kijiji.ca/v-power-tool/o...ck/1219283821?enableSearchNavigationFlag=true
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