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By flintandsteel
#1315239
I've got 920, maybe from the 1980s
Just checking the box of bits that came with it and found a set of gear cogs.
Are these an optional extra for altering the gearing on the machine
By chaoticbob
#1316487
flintandsteel wrote:I've got 920, maybe from the 1980s
Just checking the box of bits that came with it and found a set of gear cogs.
Are these an optional extra for altering the gearing on the machine


If you haven't sorted this out already by reference to CHJ's useful link, they will be changewheels which allow you to change the gearing between the main spindle and the leadscrew, thus allowing to to cut screw threads of various pitches. The range of threads you can cut will depend on which wheels you have and whether it is an imperial or metric machine.
Robin.
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By CHJ
#1316489
chaoticbob wrote:... The range of threads you can cut will depend on which wheels you have and whether it is an imperial or metric machine.
...


The various clones may also be perverse in having a mix of Imperial and metric, or maybe it's a case of second hand ones have had a incorrect replacements* fitted but it's not been unknown in the various forum references.

*or the only ones available
By AES
#1316539
CHJ (above) is correct, BUT I read on one of the "Mini Lathe" web sites that with a bit of "fiddling" with ratios it's possible to cut Metric threads on an Imperial machine (and vice-versa). They don't come out spot-on, but often near enough for everyday/practical purposes (unless you're making a micrometer or something)!

The problem is, I can't remember where I found that info - it MAY even have been an article in "Model Engineers' Workshop" mag. I've had a quick search but can't find it in my "that'll be useful one day" files, so suggest you do a Google, etc. Sorry.
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By CHJ
#1316549
AES wrote:... I read on one of the "Mini Lathe" web sites that with a bit of "fiddling" with ratios it's possible to cut Metric threads on an Imperial machine (and vice-versa). T..


Quite normal practice AES, in the above mentioned links is the chart for my machine without any fudging.
(190.81 KiB) Downloaded 18 times


The problem comes in identifying which leadscrew is fitted (imperial or metric) and if the chart you have is suitable. There are so many variations of the 9 X 20 with part supplies coming from a wealth of different manufactures, if you look at the image of my lathe you will see that it has a totally different saddle configuration to the majority. (which I like as it happens as it keeps my hand further away from hot chippings coming off the tool and more convenient for leadscrew engagement)
My Machine.Image
Steves, which is the more common layout.
Steves.jpg
By AES
#1316551
Ah, thanks CHJ. I didn't think of looking within the links you already provided!!!!

Thanks for the lathe pix too. Mine's the smaller Mini Lathe (nominally it's 7 x 14) and just as you say, although all seem to be basically "the same" (apart from colour!) when looking closely there are differences between the various "badges".
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By CHJ
#1316572
AES wrote:...
Thanks for the lathe pix too. Mine's the smaller Mini Lathe (nominally it's 7 x 14) and just as you say, although all seem to be basically "the same" (apart from colour!) when looking closely there are differences between the various "badges".


I is my understanding that the 'format' was widely circulated as generic pattern in far eastern climbs much like several others such as the common reeves drive wood lathe, as a means of speeding up engineering uptake in the area, this resulted in numerous sources spread around producing parts to varying degrees of finesse eventually coming together with whoever was finally assembling them.
By AES
#1316582
Yeah, I've heard similar ideas too.

Interesting that the Chinese are trying to increase engineering uptake there - presumably amongst students - whilst "we" (in most of Europe I think) seem to have killed the idea of craft apprenticeships.

While I really do understand a need in today's conditions that we do need to concentrate students' minds on "stuff" like robotics, special computer programs, etc, etc, it seems to me that unless a student gains some idea of "basic engineering principles" (such as materials, fits & tolerances, etc, etc), he/she is going to find it pretty hard going to advance on to the really clever stuff. (Me? An old fuddy duddy? never!) ,-)

Anyway, thread drift, sorry.

NUSUB:
There'll be a PM on it's way to you very shortly on a completely different subject.