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4th Oct 2020, 11:19 PM #16I break stuff...
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127 is the most common used, and the ideal, but it's not the only way to get there. Interestingly, one of the more common alternatives involves 63... But if it's done in the change gears, my guess is the 117 is involved.
Given you have a metric/whitworth lever though, all bets are off in my mind. It's possible that the entire conversion is done at the lever, it's equally possible that part of the conversion is at the lever and part at the change gears... The latter seems more likely to me given the odd tooth counts available in the 63 and 117 gears, but they could just be for creating certain oddball pitches.
The way that box is laid out, there's multiple different ways that could go together... And I assume you have no idea of the machines history, so it's conceivable it was set up for some incredibly obscure proprietary thread - or equally possible it's correct.
WRT to finding a manual, or some more information - you could maybe try emailing Stefan Gotteswinter? It's a long shot, but he's fluent in English, and has an eye for somewhat obscure machines - he might know a guy who knows a guy?
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5th Oct 2020, 12:21 AM #17Golden Member
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5th Oct 2020, 06:11 AM #18Intermediate Member
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Hi Mk1
This stuff fascinates me.
Looking at the pictures from the UK, it looks to me that the cog (stud gear?) that drives the change gears is not on the same centre line with the spindle. It must be geared.
The other oddity is the 117 tooth gear. To me this is really odd. I have checked as well as I can the number of teeth. It is not 127
I think I get the gear selection panel and how to read it.
Can I suggest that you;
Check the gearing between the spindle and the drive gear. My gut tells me the Imperial/metric selection is done in the head stock.
Check the pitch of the lead screw.
Very often a 21 or 63 tooth gear is used to give a conversion factor for imperial/metric, in conjunction with a 20 or 60 tooth gear. 8TPI with a 20-21 combo gives a pitch of;
0.125 x20 / 21 = 0.11905" which is close to 3 mm pitch
3mm = 3/25.4 =0.11810" actual.
The error is less than 1 %, so for short threads say 10 turns or less, the metric pitch is OK.
I saw your post on another forum going back a couple of years so it seems you have been battling this problem for some time. Hope you can soon get a good result.
rumpfy
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5th Oct 2020, 10:48 AM #19Most Valued Member
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ok this is doing my head in.
Given your second set of numbers is nothing like you first and the "scared" part makes no sense. Not that the thread chart doesn't have some scary pitches, I mean unlike the other 6 tests, its ratio does change, but the ratio goes down between 10 and 6 and up between 6 and 1. Stand by Big statement coming... that's not possible with that gear box construction lol. So failing any help from Germany, or some better idea. I think I would start by Disengaging the change gears*. picking a random pitch, engaging the halfnuts, getting a feel for how hard it is to move the carriage by turning the 72 tooth gear, then lock the carriage and see if you can still turn the gear by hand(lets not break anything).
*not back gears if that is causing confusion. Back gears are used on some lathes to lower spindle speed.
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5th Oct 2020, 12:09 PM #20Golden Member
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5th Oct 2020, 12:37 PM #21Most Valued Member
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Yes, I thought I explained that. I understand that give the max pitch on the threading chart is 112mm there are some scary pitches in that gearbox. And that's if it is setup correctly
What I was trying to get across with the "the "scared" part makes no sense", is the that results of those three tests are different from the rest and that the apparent pitch changes when the only change is the "spring trigger" would seem to not be possible. The pitch should decrease moving from 6 to 1 but it has increased(aside from the fact that it didn't change in the other 6 tests)
1:1 (higher speed)
Lever III = Metric
Lever II = Lead Screw
Normal Pitch
Lever I A
1 scared
6 ~4.0
10 8.5
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5th Oct 2020, 01:53 PM #22Most Valued Member
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Wouldn't the columns on the far right be TPI rather than Pitch?
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5th Oct 2020, 02:01 PM #23Most Valued Member
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5th Oct 2020, 02:08 PM #24I break stuff...
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My initial suspicion way back at the start was that possibly a rollpin (or similar) has sheared in the linkage from the spring trigger, and occasionally it provides enough drag to move it, or something along those lines. There definitely seems to be something wrong there that needs figuring out first.
I was just taking another look at the threading chart, since you mentioned the max size of the pitch - hadn't really sunk in yesterday how ridiculously massive they were, was probably half thinking they were imperial TPI. And I noticed that Mk1_OZ said that 4:1 is a reduction in spindle speed, rather than an increase - for some reason I was kind of thinking it was the other way round.
All of which led me to the conclusion - I don't think the course/FINE lever does anything valid here. If we look at spring trigger 1, and check the 'NML' columns, 'C' gives a 4 times finer pitch than 'A'. If you then move across to the 'CML' 4:1 and 16:1 columns side by side - that ratio is preserved. Although 'A' and 'C' are outputting the same thread count (16mm), 'C' is being hit with a 4x greater spindle reduction than 'A'. And if you then go and compare the 'CML 16:1' figure to the 'NML' figure in the C position, it's different by a factor of 16... Same goes for 'A' - "A NML" gives 4mm, "A 4:1 CML" just gives a 4 times coarser pitch according.
So the only reason I can see for that coarse/fine lever is to account for the two different leadscrew pitches they were available with, but that seems absolutely illogical, unless you could buy the different pitch leadscrew as an option, and swap between them?
I suppose it could also be for some 'shifting' to get oddball pitches (maybe it's a factor of 2 or something, to give an 'in-between' to the spindle reduction?)
This machine's giving the noggin a good workout, nice to have a brainteaser to keep us busy over here in the penal colony of Victoria.Last edited by Jekyll and Hyde; 5th Oct 2020 at 02:24 PM. Reason: Stustoys pointed out I'm an idiot.
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5th Oct 2020, 02:11 PM #25I break stuff...
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You've got good eyes... And gees that takes some squinting.
And HOLD UP. What the...
Mk1_OZ, can you take a shot of the chart to the right of the metric chart - the 'Module' chart? Something looks really screwy here...
*edit* Think I may have just worked out what the fine/coarse lever does, but I'd still like that module chart....
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5th Oct 2020, 02:20 PM #26Most Valued Member
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typo. still taking in what you have said but course/normal or metric/whitworth?
Ok I cheated a bit on that one
C1 16:1 is pretty clearly 1, so I'm pretty sure A1 16:1 is 1/4 and it looks "about right" lol
I am wondering if the course/normal pitch lever works the reverse of what we would think, but need numbers that make sense. Now back to your post.
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5th Oct 2020, 02:27 PM #27I break stuff...
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Fixed - I meant coarse/fine (or coarse/normal as it's actually written.)
And I'm now thinking it may switch between the Module threads and the Metric threads. Just had a look at a TOS manual I have, and although the Metric/Module charts are identical, (which is why I suddenly went WHAT on this lathe, I seem to recall they normally are identical?), it requires different change gears to do that. But from squinting at the table for this lathe, it kind of looks like one row in the module column matches up to the metric column, which goes back to not making sense, unless the 16:1 ratio bypasses that coarse/fine lever.
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5th Oct 2020, 03:13 PM #28Most Valued Member
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Ok this is doing my head in and I am likely missing something simple. Been looking at this to long.
How can the direction of the ratio change of the box change?
nml A lever 2 on W
spring trigger 1 = 4 TPI 6.35mm pitch
spring trigger 10 = 7 TPI 3.63mm pitch
For the same input the output must decrease to go from 6.35mm to 3.63mm pitch.
nml A lever 2 on M
spring trigger 1 = 4mm pitch
spring trigger 10 = 7mm pitch
For the same input the output must increase to go from 4mm to 7mm pitch.
Right?
What am I missing?
Who's the idiot now? lol
And it doesn't really help anyway
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5th Oct 2020, 03:16 PM #29Golden Member
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It is possible that my first three tests had me playing with the course/normal lever at the same time giving weird numbers. Not sure but that day was my first day of threading so anything could have happened!! Forget those I think.
It is quite possible that you are correct in that the Course/Normal lever may change between metric/whitworth and Module but three types and a 2 position lever?
The lead screw is 1/2" pitch as I got 6 threads in 12". That provides a little more of the puzzle.
Pulled a cover off the gearbox and to be honest I am now more confused. This is what I can see;
Internal 1.jpgOverview.jpgFront_Cover.jpgInternal 2.jpg
To better explain what I see and feel;
- the pairs of gears on Shaft A spin freely on the shaft
- the pairs of gears on Shaft B spin freely on the shaft and constantly mesh with those on Shaft A
- Shaft C is an idler shaft used to take power from A-D out to either the Lead Screw or Feed Shaft
- the 10 change gears are permanently connected to the power in via the spring lever gears
- the change gear shaft is not connected to Shaft A and has the 63 tooth back gear on it (that then doesn't mesh with anything as said before)
Right, my investigations have led me to the following conclusions -
When the Metric/Whitworth lever is in Metric the following power flow occurs;
Metric Selected.jpg
The Metric selecting lever engages the dogs on shaft B meaning the input power goes through Shaft B. The change gears are not connected to anything and so 1-10 selection makes no difference (as proved by the numbers I previously reported). Only changing between A-D will change the thread size (as shown previously).
When Whitworth is selected the following power flow occurs;
Whitworth Selected.jpg
The lever engages the dogs on Shaft A which connects the input power to Shaft A via the change gears. Selection A-D then allows power to exit to the feed shaft or lead screw. Changing the change gears will make a difference to the thread size.
Something is clearly wrong with the Metric setting as the change gears have no effect. It almost seems that the back gears are set up for whitworth and to do metric does require them to be changed. This goes against the information found on lathes.co.uk by somebody earlier.
Me confused...........
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5th Oct 2020, 03:31 PM #30Most Valued Member
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Is it still in bits? What happens if you turn the 63 tooth gear in with change gears?
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