metric or imperial

[SCOOTER]

Hi guys, i hope this is in the right section, but here goes i am going to buy a mini lathe but dont know what would suit me best metric or imperial i know that they will cut both threads on most lathes but its the dials on the lathe, the lathe i am thinking of is the Warco wm180 lathe so which do you think i should go for metric/imperial
all the best
scoot

[dickda1]

I would go with metric.  Plans in hobby mags like Model Engineer or Model Engineer's Workshop gave up on imperial quite a while ago.  Modern digital measuring devices switch between the two easily.  I have an imperial lathe, but work mostly in metric without a problem.  Issues with lead screws, change gears and screw cutting dials are discussed nicely in this forum.
-Dick

[andyf]

Scoot, I have an imperial WM180, but wish I'd got a metric one. In fact, the only truly imperial thing about mine is the leadscrew; the feedscrews on the slides and tailstock ram are actually 1mm pitch, and the dials are calibrated on the approximation that 1mm = 40 thou. That's about 1.5% out. The dials themselves involve some mental arithmetic; say you want to advance the topslide by 110 thou. The dial is calibrated with 0 - 40 thou * , so you need to give it two full turns plus another 30 thou, and even then you will be about 2 thou short, because of the 1.5% error.  

And I ran into problems in making a dial for the handwheel I fitted to my 12 TPI leadscrew, one turn of which shifts the carriage 0.833", and had to use a geared dial to avoid use of the calculator - see http://andysmachines.weebly.com/leadscrew-handwheel-and-dial.html .

Older plans are imperial, and newer ones metric, so you will often have to convert from one standard to the other before making swarf. With a metric lathe, you will need to convert imperial to metric, but once you have done that your dials will not introduce any errors. When I have to convert metric to imperial, I then have inaccurate dials to contend with.

Andy

* In fact, my topslide dial was actually, and completely wrongly, calibrated 0 to 50 thou and I had to re-engrave it 0 - 40 as shown at the bottom half of this page http://andysmachines.weebly.com/miscellaneous.html .

[SCOOTER]

Thanks Dick and thanks Andy, so thats it metric all the way, thanks for the advice it was only last night it dawned on me there was a choice.
i cant wait to get started now after reading some of the posts on madmodder, and i noticed that there are quite a few vids on the tube from madmodder members
all the best for now
scoot

[andyf]

Good choice, Scoot. Wish I'd had the sense to do the same 

Andy

[saw]

Good choice and good luck with youre new lathe. 

[Stilldrillin]

The final, finishing passes are the most important ones......

Consequently, the most important thing is to understand the amount the machine removes per division, whether imp or metric......

My imperial mini lathe removes 1mm/ turn. 40 divisions gives .00098", close enough to 1 thou/ div....... Or .025mm.

My metric mill moves 1.5mm/ turn. 75 divisions gives .0008"/ div..... Or .02mm.

David D

[andyf]

The final, finishing passes are the most important ones......

Consequently, the most important thing is to understand the amount the machine removes per division, whether imp or metric......

David D

That's true, David. And at least the error on the imperial dials is on the safe side, in that the depth of cut is slightly less than they indicate.

But the chances are that Scooter is younger than me (most folk are!), and so more likely to "think metric" than someone of my age.

And as a matter of personal preference, if something is supposed to give me a measurement, I'd rather it gave an accurate one.

Andy

[SCOOTER]

Thanks dave, i have been thinking of that
say i want to take a final pass and the amount is 1mm do i take 1mm off or would that take 2mm off as it cuts both sides so to speak
i suppose that will be first on the list to try.

[saw]

Yes that is correct, if you take 1 mm it will take 1 mm at both side. It's the very same with inch. 

[SCOOTER]

Thankyou saw
scoot

[andyf]

Thanks dave, i have been thinking of that
say i want to take a final pass and the amount is 1mm do i take 1mm off or would that take 2mm off as it cuts both sides so to speak
i suppose that will be first on the list to try.

1mm is a lot for a finishing pass, Scooter! But you raise a good point. Though my cross-slide advances 1mm/80ish thou per full turn of the handwheel, its dial is marked with 80 divisions, each pretending to be 1 thou. As is the case with many lathes, the dial shows what will be taken off the diameter, rather than the depth of cut. Your metric version will probably be similar.

Incidentally, you can get the same lathe from Chester UK as the "DB7VS" and from Amadeal as the "AMA180V". Their offerings may be a bit cheaper, but AFAIK they only come with a 3-jaw and an MT2 centre for the tailstock, whereas the Warco version also includes a 4-jaw, faceplate, fixed steady, travelling steady and an MT3 centre for the spindle.

Do bear in mind that out of the box, unlike the more usual Sieg or Real Bull mini-lathes, you can't reverse the leadscrew with respect to the spindle, so LH threading is out. Also, changing speed range is really fiddly by comparison with Seigs and RBs. I fixed these deficiencies, as you may have seen from the website I mentioned in my first post.

Andy

[SCOOTER]

Thanks andy
i did see your site and have added to my favourites as there is some good information that i will need as i get my lathe.
i have sent you a pm hope you dont mind
regards
scoot

[lordedmond]

yes to cunfund things further

my lathe is metric with 2mm screws and the dials are calibrated for the did not the radius

i.e. if I set 1 on the dial it removes 1mm from the diameter and so on

makes it very easy with a digi calliper set the size on the cal. then zero it with out moving measure the part in the lathe the measurement is the amount to be removed then just dial in the required ( which you lathe is happy with of course ) re test and repeat


Stuart

[SCOOTER]

Hi lordedmond
thanks for the reply