WARCO WM-180 thread cutting problem.

Hi guys,

I recently bought the WM-180 and would like to have a go at cutting an M6 x 0.5 thread. When I look at the threading data for 0.5 printed on the lathe it shows the change gears as [66-33] - 60 - 80, as in the first photo below. The manual has different data: [60-30] - 52 - 80. The spindle fixed gear has 40 teeth, the H in the photo is a spacer bush.

Which set of change gears is correct, the photo or the manual? There is an additional photo at the bottom which might indicate lead screw pitch but I don't really understand it, can somebody kindly explain this also please?

thank you,
Ed.

PS. Forgot to add, it's a metric lathe.

Edited By Ed Duffner on 03/10/2014 22:55:43

Oh I think I just started understanding the Indicator Table after staring at it for a few minutes. It's the thread indicator,  ...duh!.  I have two gears for it so I guess these are the 40T and 42T, the leadscrew pitch could be 2mm, I've no idea what Mn=0.6 is.

So for the 0.4, 0.5 etc threads I can use any number on the indicator dial as long as I use the same number on each pass? for 0.8 it's the 2,4,6,8 indicators and all the others I use either 4 or 8 with the 42T gear yes?

Edited By Ed Duffner on 03/10/2014 23:17:41

Edited By Ed Duffner on 03/10/2014 23:18:40

Ed,

With a 2mm pitch leadscrew and a 40T spindle gear, you just need to get a combination that will reduce the speed of the leadscrew to 1/4 the speed of the spindle for a pitch of 0.5mm. Therefore, the first cluster has a 2:1 ratio, and the leadscrew gear has a 2:1 ratio with the spindle gear, giving a total ratio of 4:1.

The middle gear is just an idler (transfer) gear, and is sized to allow good fitment of the other gear clusters on the banjo arm. It can go on either the first gear shaft or the second gear shaft on the banjo.

For example (from my C6 gear program):

Pitch, Spindle-(any)-1st Cluster-Leadscrew
00.500 mm, 40 - Idler - 50 : 25 - 80 Error 0.000%
00.500 mm, 40 - Idler - 60 : 30 - 80 Error 0.000%
00.500 mm, 40 - Idler - 66 : 33 - 80 Error 0.000%
00.500 mm, 40 - Idler - 80 : 40 - 80 Error 0.000%

Also, with the pitch an exact division of the leadscrew pitch, you should be able to engage the half nuts at any point on the leadscrew.

If in doubt, keep the half nuts engaged, and reverse the lathe for each pass.

Andrew

Edited By mahgnia on 04/10/2014 01:49:38

Andrew, many thanks for the clear explanation. I now have a much better understanding of gear ratios.

I'm still trying to grasp the idea that the idler can be different sizes. i.e. if I had the following two setups (using your format):

Pitch, Spindle-(any)-1st Cluster-Leadscrew
00.500 mm, 40 - 50 - 50:25 - 80 (50 is idler)
00.500 mm, 40 - 60 - 50:25 - 80 (60 is idler)

- These would give exactly the same result?

- Isn't one of these idler gears going to advance the gear train and leadscrew more than the other, per revolution of the spindle?

- If idler tooth count is irrelevant I could maybe have two small gears (20T) as idlers at the top on different gear shafts to allow for LH threads like the reverse tumbler setups?

Regards,
Ed.

Edited By Ed Duffner on 04/10/2014 13:28:12

Ed can you give the book ratios again as you have only listed two lines.

From the chart on teh front

40T drives 66T so 40/66 = 0.607

33T Drives 60T so 33/60 = 0.550

60T Drives 80T so 60/80 = 0.75

Multipy those three ratios together 0.607 x 0.550 x 0.75 = 0.25

This means the lead screw will rotate 0.25 of a turn per turn of the spindle, 0.25 x your 2mm pitch means the carrage will move 0.5mm per rev which is what you want.

If you do the same maths with a 50T in place of the 60T you will get the same number

J

J

Worked out how you have typed the figures

From teh book

40 drives 60 so 40/60 = 0.667

30 drives 52 so 30/52 = 0.557

52 drives 80 so 52/80 = 0.65

0.667x0.557x0.65 = 0.250

So same result

Matt,

I'm not going to answer your question directly but why not try both idlers for yourself ? One of the things you should have in your screw cutting arsenal is a pitch gauge so that when you do your first pass you can check that you have set up the gear train correctly. This will enable you to see the effects of the idler change if any. Screw cutting takes practise there are a lot of factoris that have to come together. I thoroughly recommend Martin Cleaves Workshop Practise 'Screwcutting in the Lathe' it contains a wealth of information on all of those critical factors. Whilst I encourage anyone who asks about carbide inserted tooling to learn how to use HSS, there is some advantage in using threading inserts. I often use the partial profile ones ( they are not pitch specific) . It means you can concentrate all of your attention on the threading. Some will say that you need high speeds for these , I use 52 and 120 rpm without issues and the threads are lovely in s/s , EN1a .

Regards

Tony

Hi Jason,

The book ratios for 0.5 pitch are 40 - 60:30 - 52 - 80

Mathematically:

40 drives 60 so 40/60 = 0.666

30 drives 52 so 30/52 = 0.577

52 drives 80 so 52/80 = 0.650

0.666 x 0.577 x 0.650 = 0.2497833 = 0.25

That's great, thanks Jason.

Thanks Tony, I will have a go. I'm Ed by the way.

For future reference I've just used the mathematical way to calculate a tumbler reverse with two 20T idlers.

These are with the middle idler in the gear train.

Forward.
40 Drives 20 so 40/20 = 2.000
#20 Drives 20 so 20/20 = 1.000 (not engaged)
20 Drives 60 so 20/60 = 0.333
30 Drives 52 so 30/52 = 0.577
52 Drives 80 so 52/80 = 0.650

2.000 x 0.333 x 0.577 x 0.650 = 0.2497833

Reverse.
40 Drives 20 so 40/20 = 2.000
20 Drives 20 so 20/20 = 1.000
20 Drives 60 so 20/60 = 0.333
30 Drives 52 so 30/52 = 0.577
52 Drives 80 so 52/80 = 0.650

2.000 x 1.000 x 0.333 x 0.577 x 0.650 = 0.2497833

----------------------------------------------------------------------

These are with the middle idler removed from the gear train depending on available space on the quadrant.

Forward.
40 Drives 20 so 40/20 = 2.000
#20 Drives 20 so 20/20 = 1.000 (not engaged)
20 Drives 60 so 20/60 = 0.333
30 Drives 80 so 30/80 = 0.375

2.000 x 0.333 x 0.375 = 0.24975

Reverse.
40 Drives 20 so 40/20 = 2.000
20 Drives 20 so 20/20 = 1.000
20 Drives 60 so 20/60 = 0.333
30 Drives 80 so 30/80 = 0.375

2.000 x 1.000 x 0.333 x 0.375 = 0.24975

Ed,

Sorry, I was emailing a Matt a few minutes earlier.

Tony

Ed,

Correct, these would give the same result, as long as they are both mountable on the banjo.

The idler connects the two end of the gear train in a 1:1 ratio, as both ends advance at the same gear tooth speed.

The tumbler reverse idea should work, this would be a novel solution. It may be helpful to have the facility to use different sizes of gears in the tumbler to allow for different space requirements when cutting different thread pitches. Remember that the tumblers do not need to be the same size as each other, as they are both idlers.

Some ideas for this can be seen in my photo gallery on this site.

Regards,

Andrew

Ed,

Link for more information on a Reversing Tumbler setup for a C6 lathe (may be helpful to you):

**LINK**

Regards,

Andrew

Hi Andrew,

Many thanks again, this is great info.

Regards,
Ed.