Sieg C6 Lathe new threading possibilities

Alan,

If you give me the full list of change gears that your lathe has at the moment, I'll run the numbers and give you some combinations to try. The software that I use has the geographical limitations of the C6 programmed into it, so depending on what size the banjo is on the WM240, some combinations may not fit.

Alternatively, if you have the following gears, hopefully they will fit.

17.96 TPI = 80 (TOP RIGHT) meshed with 60 (MIDDLE RIGHT) and 70 (MIDDLE LEFT) meshed with 66 (BOTTOM LEFT)

24.00 TPI = 66 (TOP RIGHT) meshed with 42 (MIDDLE RIGHT) and 50 (MIDDLE LEFT) meshed with 90 (BOTTOM LEFT)

These came from the work Ian did in the following post which is based on the standard set of change wheels for the C6,.

http://www.woodworkforums.com/showthread.php?t=181303&p=1746357#post1746357

Graham

Edited By Graham Wharton on 17/07/2015 19:25:14

Steve, that information is also in the following thread

**LINK**

Hope it helps

Graham

Hi Graham,

That is a very kind offer. Thank you. I'm sure there are other 240 owners that would also be grateful for a list of extra threads.

The magic gear that is absent from the 240 range seems to be the '66'; bit of a cheapskate omission if it could provide such a range of other common thread pitches. (Anyone from Warco reading this?) The full set of gears I have includes: The resident 40T on the spindle plus 40T idler; the actual 'change gears are 25, 30, 33, 40, 42, 52, 60, 70, 75, 80, 90, 90.

Comparing your solution above for 24tpi to the standard gear set also shows that '50' is also not included. Both of the omitted gears are available from HPC in Mod 1 size at reasonable prices. The banjo size would also not be too much of a problem because a redesigned replacement would be simple to manufacture. I've been there before adding an extension to my Hobbymat banjo to extend the range. That, though, was simply to add a 30:60 or 35:70 cluster to double or halve existing threads.

I have tried to access the thread on Woodworkforums.com but ,even after registering, it won't allow access.

I look forward to seeing what your calculator comes up with.

Alan

Thanks Graham, I saw that, I was just trying to avoid registering for yet another forum...

Steve

Graham,

I forgot to note in the earlier post that the leadscrew pitch, being a metric lathe, is 2mm. At least that is how I see it with the non-ganged gearing for 2mm pitch showing 40T on spindle and leadscrew.

Alan

Hi Alan,

Well using your set of change gears I've run the numbers and I get the following.

http://gwharton.com/wm240.html

There's a whole load of data there as it basically runs every imperial pitch from 5TPI to 80TPI in 0.5TPI intervals and then from 0.01mm to 0.2mm pitch in 0.01mm intervals and 0.25mm to 6.0mm in 0.05mm intervals.

Should probably explain in the geartrain column,

• a - means that the two gears are meshed. i.e 10-20 is 10 meshed with 20.
• a : means that the two gears are on the same shaft. i.e 10:20 is 10 and 20 gears on the same shaft.
• Sometimes you might get 90:90 where both gears are the same on that shaft, in this case, just install the one gear, you dont need to use two.

It lists the desired pitch, the achieved pitch, and the % error in what was achieved.

From the chart I now get

17.95 TPI = 70 (TOP RIGHT), then 90 (TOP LEFT) meshed with 42 (MIDDLE LEFT) and 52 (MIDDLE RIGHT) meshed with 90 (BOTTOM RIGHT)

24.04 TPI = 70 (TOP RIGHT), then 80 (TOP LEFT) meshed with 75 (MIDDLE LEFT) and 52 (MIDDLE RIGHT) meshed with 60 (BOTTOM RIGHT)

I dare say, there are probably a few standard pitches that you will be able to pick out the charts that will fit straight off. I don't know whether manufacturers down play the amount of threads that their machines can cut out of the box in order to tempt you into going for higher models. I could certainly cut many more threads than advertised with my C6B out of the box.

Obviously all of these numbers are based on the physical limitations of the C6B, so I may be throwing away more accurate combinations because of this.

If you wanted to go one step further, you could make the following measurements and let me know the results and I will rerun with the limitations of the WM240 instead of the C6B

• Distance from the centre of the feedscrew shaft to the bottom of the 40T idler gear + 2mm. C6B = 156mm
• Put your largest gear in the top shaft of the banjo at the furthest extent so it still meshes with the 40T idler and measure the distance from the centre of the feedscrew to the top of the largest gear you fitted (inline with the axis of the banjo, not where it meshes with the idler). There might be obstructions that stop you putting a large gear at the very top of the banjo. C6B = 181mm
• Move the lower shaft of the banjo to the lowest position with no gear fitted and measure the distance from the centre of the feedscrew shaft to the centre of the lower banjo shaft C6B = 43mm
• Place a gear in the top shaft on the banjo and engage with the 40 tooth idler. Now, if you were to put a gear next to it on the top shaft, how much bigger in diameter can that second gear be, before it fouls on the end of the 40T idler shaft. C6B = 20mm. i.e For module 1 gears, 1 tooth = 1mm diameter. So in my case, if I put a 60T gear to mesh with the 40T idler, I cant put anything bigger than an 80T next to it.
• How much air gap to leave between gears so they don't mesh. C6B = 1mm
• What is the diameter of your spacers. C6B = 21mm
• Place the upper shaft on the banjo at the top position as far as it will go. Place the lower shaft on the banjo at the lowest position, and measure the distance between the two shaft centres. C6B = 100mm
• Whats the smallest size of gear that you can fit on the top banjo shaft and still engage the gear with the 40T idler, without the gear securing bolt fouling on the spindle Vee Belt pulley. C6B = 60 teeth. You might not have this limitation if the drive pulley arrangement is different on the WM240.

Hope this helps.

Graham

Edited By Graham Wharton on 18/07/2015 16:01:58

Edited By Graham Wharton on 18/07/2015 16:05:50

Alan'

Using gears that I have made for my C6, including supplied gears:

18TPI:

18.011 TPI, 40 - Idler - 52 : 55 - 60 Error 0.061%
18.011 TPI, 40 - Idler - 60 : 55 - 52 Error 0.061%
18.011 TPI, 40 - 50 : 55 - 90 : 75 - 52 Error 0.061%
18.011 TPI, 40 - 52 : 55 - 90 : 75 - 50 Error 0.061%
18.008 TPI, 40 - 75 : 80 - 66 : 60 - 55 Error 0.046%
17.995 TPI, 40 - 75 : 80 - 70 : 66 - 57 Error 0.030%
18.011 TPI, 40 - 80 : 75 - 65 : 55 - 45 Error 0.061%
18.011 TPI, 40 - 65 : 55 - 90 : 75 - 40 Error 0.061%

18 TPI can be done with the standard supplied gears with a high degree of accuracy only with certain mods to the gear quadrant or gear assembly to allow spindle clearance from the gears.

24TPI:

24.003 TPI, 40 - Idler - 42 : 25 - 45 Error 0.013%
24.003 TPI, 40 - Idler - 42 : 50 - 90 Error 0.013%
24.003 TPI, 40 - 42 : 40 - 90 : 75 - 60 Error 0.013%
23.993 TPI, 40 - 70 : 66 - 75 : 60 - 57 Error 0.030%
23.993 TPI, 40 - 70 : 66 - 65 : 52 - 57 Error 0.030%
23.995 TPI, 40 - 70 : 65 - 80 : 57 - 50 Error 0.022%
24.003 TPI, 40 - 90 : 75 - 70 : 50 - 45 Error 0.013%
24.003 TPI, 40 - 45 : 50 - 90 : 75 - 70 Error 0.013%
23.993 TPI, 40 - 57 : 60 - 70 : 66 - 75 Error 0.030%
23.993 TPI, 40 - 57 : 60 - 75 : 66 - 70 Error 0.030%
23.993 TPI, 40 - 65 : 66 - 70 : 52 - 57 Error 0.030%
23.993 TPI, 40 - 65 : 66 - 57 : 52 - 70 Error 0.030%

The second listed gear train uses only standard supplied gears.

These have all been calculated by my program to be installable on the C6.

They may also work on your lathe.

The gears that are not standard on the C6 were made from aluminium using plastic gears from the C3 lathe as indexing templates, with a fly cutter ground to similar size MOD 1 gear tooth profile, in an indexing fixture. This gave me additional gears 35T, 45T, 55T, 57T and 65T.

Andrew.

Edited By mahgnia on 18/07/2015 16:34:53

Thanks very much Graham and Andrew.

Wow! What a lot of combinations, just from the standard gears. Now to do a cull to the smallest % error. I wonder why the manufacturers won't give this sort of information to make life easier for their customers.

Graham, when I'm let free this afternoon, I'll measure the space as you so clearly explained in your post. I'll then get back to you if that is OK.

Many thanks

Alan

Hi Graham,

I have measured my WM240 as you detailed and obtained the following:

a) Distance from feedscrew centre to bottom of 40T idler 152mm (150mm measured +2mm)

b) Distance from feedscrew centre to top of largest (90T) gear 185mm

c) Distance from feedscrew centre to lowest banjo lower spindle centre 39mm

d) Maximum size differential between gear diameters on top banjo spindle 8mm (52:60) *

e) Air gap between gears 1mm (boss on all gears except 25mm)

f) Spacer diameters 22mm

g) Maximum distance between upper and lower banjo spindle centres 100mm

h) Smallest size top banjo gear in mesh with 40T idler smallest gear (25mm)

* This distance seems disappointing when compared to the 20mm for your C6B and, reading down the top banjo spindle combinations, it looks as though quite a few selections would be prevented with the idler as is. The limitation is caused by the second gear fouling a large washer/cover plate over the idler gear bearing. More space could possibly be gained by replacing the ball race with either a plain or needle roller bearing. I tried several combinations of adjacent size gears but couldn't better the 8mm. 60:70 just rubs on the offending bearing cover, preventing complete meshing.

Other than the lack of gear size differential, most of the WM240 measurements are not vastly different to your C6B.

I appreciate the time you must have put into this for me. Thank you.

Alan

Alan,

Have a look at my album for some ideas, which shows various modifications to the C6 which now allows me to mount nearly all of the most accurate gear combinations available to the C6.

**LINK**

Mods include:

1. Selectable spindle idler gear to allow better top cluster clearance from the idler.

2. 3-deep gear clusters that allow mounting of clusters that would otherwise interfere with each other.

3. Reverse tumbler incorporating the above modification number 1.

4. Longer banjo (quadrant) arm with slot extending further towards both the leadscrew end and the far end.

Andrew

Edited By mahgnia on 20/07/2015 09:31:37

Hello AlanW,

At the risk of upsetting someone, and only because you said you were going to do a cull to get the smallest error, I played with the numbers that mahgnia printed out for you

18 tpi is 55.6 thou per pitch taken to one decimal place and 0.061% actually represents a real error of 0.033 thou per pitch.

Over say 10 threads that is still a total error of 1/3 thou which can be isafely ignored completely. There is a real misconception amongst model engineers in particular that the pursuit of threading perfection is a holy grail; this is just another example.

I would select the simplest gearing arrangement that you have gears for rather than make or buy ones that you may never use again.

Regards

Brian

Edited By Brian Wood on 20/07/2015 10:13:50

I fully agree with your analysis and conclusion.

Andrew.

Hi Andrew,

An interesting collection of parts. Unfortunately the selectable idler would make no difference. The idler on the WM240 is clearly different from the C6; my idler is a nylon ring gear that is a sliding fit on the outside of an unshielded ball bearing. The large washer that baulks the outer gear on the top spindle probably serves the additional purposes of shielding the bearing AND preventing the gear from sliding off the bearing. More thought needed, I think. Thank you for your suggestions. In fairness to the lathe, most of the gears I am likely to cut will be metric and the lathe covers the range adequately. However there will be occasions when imperial will be needed. For example, last week I was able to cut a 1/4BSP (parallel, thankfully) which is 19tpi; I also needed to cut 1/4 and 3/8 NPT but the 18tpi is conspicuous in its absence. As it happened I chose to buy dies because I didn’t want the complication of cutting tapered threads on the lathe.

Brian,

Point taken. Rest assured, the Holy Grail is safe from me! I was actually too hastily referring to the solutions provided by Graham (all eight pages of them when pasted directly into Word). On closer inspection of the list, what I thought were multiple solutions are actually intermediate pitches as well.

Alan

Edited By Graham Wharton on 20/07/2015 23:15:56

Edited By Graham Wharton on 20/07/2015 23:16:55

Thanks Graham, all very useful. I didn't notice at first that intermediate pitches are generated, thinking that they were just different combinations for the same result.

If you have read my previous replies, you will have gathered that I need to make some changes to the lathe for quite a few of the gear combinations to work, owing to the lack of distance between the second gear on the top spindle and the idler gear retainer. Having given it more thought and seen Andrew's modifications, I will probably make new, slightly longer, spindles and spacers of around 3mm thick so that the second gear clears the end of the idler spindle completely. That should allow quite large gears to fit.

Woodworkforums.com has now let me download the calculator posted there but I haven't had a chance to try it out yet. Then again, thanks to you, I have a comprehensive list so I may not need to.

Thank you.

Alan

Further to my last post, I made a couple of extended length spindles and spacers to allow larger gears to clear the idler spindle. I haven't tried many of the combinations but the new arrangement worked fine for 26 and 27tpi and also for a 30.5tpi screw for a Victorian sewing machine. With some combinations, it puts the last but one in the train in half mesh with the leadscrew gear, so I need to lok into solving that issue.

Thanks for your input folks.

Alan

Hi all, as a newbie to this hobby, this site and this topic, and at the risk of slightly derailing the current thread, i have recently (as in Christmas 2015) bought a new C6 from Ausee and am now starting to use it for what it was intended. My previous lathe (a 1929 vintage light-duty machine which i have kept for sentimental reasons) has a handwheel on the leadscrew which i have found particularly useful in providing a finer feed than using the handwheel on the carriage, and i would like to provide a similar facility on the C6. Has anyone carried out this modification and if so could they provide some advice on the best way to approach it?

Thanks in anticipation, Geoff P.

Hello Geoff,

It doesn't look as though many readers are monitoring this thread any longer. You may be better off creating a new thread specific to your question.

I'm not a C6 user but I don't think my Warco is so vastly different in general design. There is a powered leadscrew article coming up in the April edition of MEW; from the photo it looks as though the subject lathe is a Warco, so the method of attaching the pulley to the leadscrew will certainly interest me, for the same reason as your query re the C6.

The standard mod for a C3 is to drill and tap the end of the leadscrew M6 and add a stub extension, screwed and loctited in place.

Neil

When working out errors in pitch, remember that when a bolt is tightened, the bolt stretches and the nut is compressed. So, any errors could usefully be apportioned so that the error is reduced by tightening - bolts should have threads a bit close, and/or nuts a bit wide.

Just a thought

Tim