Metric Mini Lathe Leadscrew

[Sub MandrelParticipant @submandrel]

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

[Sub MandrelParticipant @submandrel]

Simple question

[AndyfParticipant @andyf]

1.5mm.

Andy

[Jens Eirik Skogstad 1Participant @jenseirikskogstad1]

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.

[Sub MandrelParticipant @submandrel]

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

[wheeltapperParticipant @wheeltapper]

The Chester Comet variable speed is 2mm.

Roy.

[AndyfParticipant @andyf]

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 7×12 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

[Jens Eirik Skogstad 1Participant @jenseirikskogstad1]

Posted by Andyf on 13/04/2013 00:37:58:

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.

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.

[John Stevenson 1Participant @johnstevenson1]

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

[AndyfParticipant @andyf]

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

[Michael GilliganParticipant @michaelgilligan61133]

Time to revisit all those Martin Cleeve articles ?

MichaelG.

[Jens Eirik Skogstad 1Participant @jenseirikskogstad1]

I has own made 127 change gear wheel with Mod 1 in my Sieg lathe 250×550. 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/ 50×75 to 70×127/50×75 ( 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

[Sub MandrelParticipant @submandrel]

Thanks all!

Yu've answered all my questions and more!

Neil

[anthony brooks 2Participant @anthonybrooks2]

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

[Neil WyattModerator @neilwyatt]

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

[anthony brooks 2Participant @anthonybrooks2]

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.

[Michael Cox 1Participant @michaelcox1]

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

[Enough!Participant @enough]

Posted by anthony brooks 2 on 27/11/2016 00:26:33:

Thanks Neil

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

 

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

[Danny M2ZParticipant @dannym2z]

Posted by anthony brooks 2 on 27/11/2016 00:26:33:

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.

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.

[Neil WyattModerator @neilwyatt]

Posted by anthony brooks 2 on 27/11/2016 00:26:33:

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.

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

Neil

[Howard LewisParticipant @howardlewis46836]

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

[not done it yetParticipant @notdoneityet]

I have several metric/imperial dials called 'Vickers inch metric conversion units'. There may be something in the box that would suffice? If interested, message me and I will check through them for anything that measures up. Not perfect, but all serviceable – and they are cheap!

[David Watson 3Participant @davidwatson3]

I inherited a Warco Mini Lathe from my late father. So far I have managed to carry out most of my projects within the lathes capacity.

As my father was orientated to Myfords and a Rivet lathe I assumed the mini lathe was imperial. The cross and compound dials are in duel increments. The change gear information on the end cover is not in English, Italian I think. Having recently found the invoice for the lathe it appears it is a metric lathe.

My latest project may require some screw cutting, Acme Thread. I am a bit stumped as to gear settings etc. Also I have found a small shaft that appears to be part of the lead screw indicator. Maybe I should be thinking metric Acme threads- 6mm instead of 1/4"

[Rick Kirkland 1Participant @rickkirkland1]

First of all metric Acme threads don't exist. Metric pitch threads of that appearance are called Trapezoidal threads and they have a 30 degree included angle as opposed to an Acme thread which is Imperial and has a 29 degree included angle. Also are you talking about 6mm/ 1/4" pitch or 6mm / 1/4"diameter ?

[David Watson 3Participant @davidwatson3]

Hi Rick, I was having a senior moment about acme threads, I am imperial orientated. I need a 1/4"- 2 start acme threaded rod and nut. This is could be some thing beyond me and the min lathe. I have found a gear to change from metric to imperial but its the screw cuttng that might throw me.

I started with a battered Myford ML4 until I closed the workshop due to other comitments. Inheriting a lathe seemed a good chance to start again.

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