What I did was calculate the revolution of the lead screw for each rev of the chuck for a 1.25mm using a 3mm lead screw. = .416666666667 revs. I could not come up with that rev for any combination on the QCGB so it needed to have some kind of ratio change on the input gear train. I looked at my manual even though it has a imperial lead screw the QCGB used the same ratios as yours. One ratio that popped out was the 30/36 which is = .8333333333 which looked like it might be two times what was needed and .8333333/2 = .41666665
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Lathe threading
- Thread starter BenW
- Start date
I see. I have failed to find a chart for a lathe with the exact same setup as mine so I guess I'll simply make a chart for each of the diffrent combinations of gears in the input gear train. Thank's for the help.
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I'm guessing your machine is imperial. The reason for the reverse use of the compound gear is simply because my machine uses it to convert from metric to imperial and yours does the opposite. Thanks for the chart, I'll look through it later and see if I can find anything useful.
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Hi. Sorry for not answering, taptalk didn't show a new reply for some reason. Your chart appears to be for a lathe with an imperial leadscrew and thus the data doesn't directly apply to my lathe, but it could nevertheless be useful to someone.
I had gotten a bit sidetracked with other projects and threading wasn't something I needed, until yesterday. I wanted to cut a m12x1.75mm thread and could not figure out what gear combination and gearbox setting I needed, so I decided to finally write a complete metric chart for my lathe, which I said previously I'd upload, so here it is:
This 3-page chart contains all the thread pitches in mm for each possible combination of gearbox setting and changegear combination, rounded to three decimals for the long values, and I thought it might be useful to someone in the future that's missing a threading chart like me. The chart consists of 12 smaller charts, one for each of the possible changegear configurations, and each small chart contains the 58 possible gearbox settings for that changegear combination. Of course, 95% of the threads in the chart are useless, and I should (and will, some other day) probably compile the useful threads into a much more compact chart. To clarify, this applies to a generic Taiwanese 13something lathe with a qcgb that is of imperial design, but the lathe being "converted" to metric by putting a 3mm pitch leadscrew on it which seems like a bad approach since cutting metric threads still requires changing gears often, which is a pain. Nevertheless I can at least cut all pitches I've needed thus far. My handwriting isn't the best and I'm wearing a support glove-thingy due to some problems with my thumb which doesn't precisely help, so the chart might be a bit difficult to read, sorry about that.
I had gotten a bit sidetracked with other projects and threading wasn't something I needed, until yesterday. I wanted to cut a m12x1.75mm thread and could not figure out what gear combination and gearbox setting I needed, so I decided to finally write a complete metric chart for my lathe, which I said previously I'd upload, so here it is:
This 3-page chart contains all the thread pitches in mm for each possible combination of gearbox setting and changegear combination, rounded to three decimals for the long values, and I thought it might be useful to someone in the future that's missing a threading chart like me. The chart consists of 12 smaller charts, one for each of the possible changegear configurations, and each small chart contains the 58 possible gearbox settings for that changegear combination. Of course, 95% of the threads in the chart are useless, and I should (and will, some other day) probably compile the useful threads into a much more compact chart. To clarify, this applies to a generic Taiwanese 13something lathe with a qcgb that is of imperial design, but the lathe being "converted" to metric by putting a 3mm pitch leadscrew on it which seems like a bad approach since cutting metric threads still requires changing gears often, which is a pain. Nevertheless I can at least cut all pitches I've needed thus far. My handwriting isn't the best and I'm wearing a support glove-thingy due to some problems with my thumb which doesn't precisely help, so the chart might be a bit difficult to read, sorry about that.
Useful chart, and it represents a lot of careful work on your part! The only problem I had reading some entries was from the lighting on the second page. The general organization is good. You can make it a bit more readable by leaving the "uneven" thread pitches blank.
Then again, you can make a table, with pitch in the first column, gears in the next two, and QCGB settings in the last column(s). There will, of course, be some duplicates. You can either include these or just pick a single handy one to include. You can also eliminate some thread pitches that aren't ever used for standard fasteners. A spreadsheet program is handy for this.
I made the following chart for my Grizzly 12x24 lathe (inch lead screw), after noticing that the chart on the lathe had a lot of weird pitches on it and was missing some commonly used ones.
Then again, you can make a table, with pitch in the first column, gears in the next two, and QCGB settings in the last column(s). There will, of course, be some duplicates. You can either include these or just pick a single handy one to include. You can also eliminate some thread pitches that aren't ever used for standard fasteners. A spreadsheet program is handy for this.
I made the following chart for my Grizzly 12x24 lathe (inch lead screw), after noticing that the chart on the lathe had a lot of weird pitches on it and was missing some commonly used ones.
