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| Calculate thread pitch and feed rates... |
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| John Hill:
My lathe has the usual table of feed rates and thread pitches but it by no means covers the whole range of available combinations, not that that is a real issue as there are more than enough listed to meet my needs. My problem is the way they are listed as it seems to take ages for me to scan all over the tables to find what I am looking for. My Chinese lathe has two three-position levers for changing the spindle speed and a single speed belt drive from the motor, thats easy enough, 9 speeds and the associated table is not too difficult to handle. The lower gear box that drives the feed screw and another drive rod has four levers (big knobs actually), one of these levers has just two positions 'M' and 'S' which as far as I can tell select drive to the feed screw or the drive rod. One other lever has just two positions 'I' and 'II' which I think is only effective when the drive rod is selected. The feed screw cuts metric threads (as far as I know) and the drive rod (when the feed screw is not being driven) provides power to the saddle for both 'X' and 'Y' feeds. That leaves just two levers which each have five positions '1'..'5' and 'A'..'E'. By my reckoning thats 25 combinations on those last two which means 25 metric threads and considering that the 'I','II' lever is effective when using power feeds thats 50 'X' and 50 'Y' feed rates and of course 50 thread pitches in addition to the 'native' metric threads. All this is before changing gears (cogs). Has anyone ever tried to write software that would list all these combinations and sort them into some convenient order? If they havent I might just give it a go... |
| Darren:
Good grief, with that lot I'd be confused too. Didn't it come with a :lol: "manual" :bugeye: Sounds like it needs a hardback..... :bang: |
| bogstandard:
Darren, The manual that came with mine is perfect bum fodder for the outside khazi. John's lathe is basically the same as mine, but I have 18 spindle speeds instead of 9, so is a little more complicated, but not all that beneficial, as the range that I use only uses half of them. I personally, once I had the code broken, have not found any problem getting what I want. But if someone could make it a little easier to find the correct combination, there would be no complaints from me. Bogs |
| John Hill:
John, did you notice any errors in your lathe tables? For instance, when I compared the 24 to 48 tooth feed rates with the 48 to 24 rates I expected one would be exactly four times the other but on the table they dont always seem to be. They are mostly very close and can be explained by decimal rounding but some seem to be more than that. Of course these tiny rounding errors are of no practical consequence but they will somewhat complicate the calculation of intermediate speeds and ratios. We have a little project going in Saudi Arabia but once I bat the ball back over the net to their side, which will not take much out of the day, I expect there will be time to think about how to do this. |
| bogstandard:
David, To me, the feeds rates don't need to be that exact as all they are used for is for finish. As long as they are near enough, that is close enough for me. It is the accuracy of the threading charts that worry me, and I have yet to start to cut any. But when I do, I will do a sample of every thread that can be done, and go over them with a microscope to see just how far out they really are. I still have the suppliers in my sights if anything is too far from what they state. John |
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