Metric Mini Lathe Leadscrew

Can someone with a mini lathe tell me if the leadscrew is 2mm pitch or 1.5mm, please?

In return I can reveal that the imperial leadscrews are 1/16" pitch/16 tpi.

Neil

1.5mm.

Andy

Stub Mandrel, there is not named which brand is the lathe..

My Sieg lathe has 2 mm lead screw, MJ-358 has 1,5 mm lead screw and Emco Unimat 3 has 1 mm lead screw.

To learn out pitch of lead screw: Place the caliper ruler between the head stock and the cross slice, then rotate the lead screw one turn while you are reading how much is the mm or inches the pitch of the lead screw.

Thanks botg,

Jens, I mean what the Americans call a 7 x 12 mini lathe.

I have an imperial CL300M. After the last week or so, I am not surprised if there are both 1.5mm and 2mm metric ones out there!

It would be helpful in particular to know what pitch the Warco and Chester versions are.

Neil

The Chester Comet variable speed is 2mm.

Roy.

Though I've never owned a 7x minilathe, I know a fair bit about them because, for reasons known only to the Almighty, I'm one of the moderators of the largely US based 7x12 Yahoo Group.

The imperial leadscrews on both the Sieg and Real Bull 7xs are 16 TPI, and the metric ones are 1.5mm, which is in the same ballpark.

Though described as imperial, the only imperial thing about them is the leadscrew; the feedscrews on the slides and tailstock are 1mm pitch and the dials work on the approximation that 1mm = 40 thou. There is an exception in that those sold in the US by Micromark have "true inch" feedscrews.

If you want to switch from an imperial to a metric leadscrew, Machine Mart sell a kit for about £30, part no. 060720720, though it's currently out of stock.

The Chester Comet is a larger lathe - I think it's an 8 x 18 in American terminology - and the metric version has a 2mm leadscrew. It's probably a safe bet that the version sold in the US is 12TPI.

Andy

Instead to replace the lead screw to imperial or metric, use change gear with 127 tooths for accurate treading of the pitch of imperial or metric. It is cheaper to buy or make a change gear with 127 tooths than to buy the new lead screw.

Firstly can you buy a 127 gear for one of these machines and secondly will it fit ?

Not to my knowledge, John, and I think it's because the diameter is too large for the lathe. Sieg do a 127T for the C4, which is probably Mod 1 with the same bore and keyway as the C3, but there isn't room for it.

I suppose a pair of transposing gears, one being 127T, could be made up in Mod 0.6 or 0.7 (or a similar size DP) and used in conjunction with the rest of the change wheels.

You can get tolerably close to metric threads using an imperial leadscrew with the standard gear set, as this calculator shows.

Andy

Time to revisit all those Martin Cleeve articles ?

MichaelG.

I has own made 127 change gear wheel with Mod 1 in my Sieg lathe 250x550. As compound gear set up is not problem, in case the 127 gear wheel is difficult to place there, replace the 127 with other gear wheel such as A gear wheel with C gear wheel or B gear with D gear To example 127 x 70/ 50x75 to 70x127/50x75 ( A x C / B x D = Gear ratio) without changing gear ratio in compound gear wheel set up in lathe.

Some Sieg lathe has 127 and 120 cange gear wheel as B/C or C/B in compound gear wheel set up. Some lathe has 100 instead 120 change gear wheel

Edited By Jens Eirik Skogstad on 13/04/2013 09:41:53

Thanks all!

Yu've answered all my questions and more!

Neil

A question for Andyf.

Are there any US vendors who sell metric mini-lathes?

I called Big-Dog(Real Bull machines) and was told very definitely that they would NOT bring in a metric machine. I spent $450 on a 1951 South Bend instead. I really wanted a metric machine(I grew up in Rhodesia) but the likes of Harbor Freight etc only take orders.

I have a Grizzly mini-mill. The 1/16' movement per dial rotation is a pain. I would have thought making the screw 1/10 or 1/20" more logical. Again a metric option would be good.

Cheers

if you click on Andy F's '298 forum posts' link, you'll see he hasn't posted for over three years, I'm afraid.

All mini lathes except a very few sold as 'Tru-Inch' actually have 1mm pitch screw threads on the cross and top slides.

A 63-tooth gear will let you cut metric threads on an imperial mini lathe.

If you really want a metric one, why not buy an imperial one and iget a conversion kit? Little Machine Shop sell one on your side of the pond.

Neil

Thanks Neil

If the cross / compound screws are metric , are metric dials available?

The forums are my only source of info other than a friend in S.Africa. There are no model engineering clubs around here(Albany GA). Most seem to be 'up-North.' My co-workers see me as 'strange' because I try to fix and make things.

Andyf sadly passed away in 2013 which is why there are no recent posts. Andy was well known on many machining groups and was a moderator for both magnifier and the 7 x 12 miniature group

Dials aren't metric or inch per-se they are simply a given number of divisions which may be appropriate to one or the other depending on the leadscrew pitch.

LMS has 50-division dials here.

Edited By Bandersnatch on 27/11/2016 01:38:09

Metric leadscrews and dti's to match are available including suitable gears for the minilathe.

As for the cross and compound slides, get a calculator and remember that 25.4 is your friend.

Fixing things is good.

The dials are marked in 0.025mm increments which are also close to 0.001"

Neil

The screwcutting chart in the handbook for my Chester Conquest Super quotes 40 - 60 - 40 to cut a 1.5mm pitch Metric thread, which implies a 1.5mm pitch Leadscrew. I think that that was what I found when I checked, when I bought secondhand, a year or so ago, but memory is not infallible.

In the R H bottom corner of the front sheet of the handbook, it says "C3" so I take it to be a Seig C3.

For anyone wanting to cut Imperial on a machine with a Metric leadscrew, or vice versa, there should really be a 127T gear in the changewheel train.

However, for the C3, Arc Eurotrade offer a 63T gear, and apparently the error is small enough to be ignored for most purposes, something like the fourth decimal place? (but possibly not if you are manufacturing allthread!)

Must  get round to installing a graduated Handwheel on the Leadscrew, with 60 divisions, (0.025mm/div'n) which I calculated to equate to something of the order of 0.00098 inches per division

Being a Super, the Cross and Top slides have DRO, but these Leadscrews were definitely 20 tpi when I checked!

Howard

Edited By Howard Lewis on 27/11/2016 20:42:53

Edited By Howard Lewis on 27/11/2016 20:45:30