Help identify leadscrew on EMCO compact 8 lathe

mfisher · Jun 5, 2009

I don't have all my reference books here, and I can't find anything quickly.

Looking at the leadscrew for the Austrian (1970's) EMCO Compact 8 (the inspiration of all the 9x20 lathes out there).

Half nuts are stripped.

A quick measure of the leadscrew diameter read 0.582 inch (toolbox caliper, not a good one, so it might be off some). Threads meshed up seemingly perfect with a 3/8-16 tap, did not seems to be any difference over the length of the tap.

'Tony's Site' (lathes.co.uk) says the machine used a metric 60 degree thread profile, but it certainly didn't look like that to me.

The Grizzly site (which supports their machines which are copies of this one) shows a SAE 9/16-16 thread.

Any thoughts as to what I have here?

Thanks.

Matt

Dr. Rob · Jun 5, 2009

Pitch was 1,5 mm on mine. Don't recall thread form, sorry. Think it was sorta trapezoid. Trapezoid, ie a european acme with 30° angle.

.

bcstractor · Jun 5, 2009

French manual and sales brochure both say standard feed rates are .09mm and .18mm. So knowing what gears are used to get that.....

Almost everything is quoted in metric too - so 1.5mm is probably it.

Chris P

mfisher · Jun 8, 2009

I would have guess metric as well, except over nearly 1" of length of a 3/8-16 tap, the threads were still lining up properly. If it was a 1.5mm, and 16 tpi is 1.59mm, that is a 5.8% difference, and over about 12 threads = 0.7 threads, so I should have easily seen that.

It definatly looks to be a trapezoid form, certainly not a 60degree thread like it shows in Tonys site (mind you I do not have any manual, so I am guessing here).

The 0.582 inch diameter is 14.78mm, so it would be close to a 15mm, except I have found no standard 15mm trapezoid to exist. Could be a special one, but DIN frowns on that.....

I better take a better look at the thread count, see if I misled myself there with the 16 tpi...

Armenius · Jun 8, 2009

First things first:

Can you identify it as an inch or metric machine???

Arminius

mfisher · Jun 8, 2009

It is an inch machine.

I just ran home and laid a 12" piece of 3/8-16 all thread along the lead screw. Although the thread shape is different, it is clearly a 16tpi thread. Over 12 inches the threads lined up from end to end.

It does measure in at 0.582 inch outside diameter.

Phil Burman · Jun 8, 2009

Go and talk to cba_melbourne on:

http://groups.yahoo.com/group/9x20Lathe/

He's a bit of a buff on Emco 8 lathes.

Phil

Armenius · Jun 8, 2009

mfisher:

I would opine that your lead screw is indeed 16 TPI with trapezoidal thread form. It may also be a left hand thread. Check the threading table for your lathe; if the spindle speed is that of the lead screw (1:1 ratio) for 16 TPI threading this would confirm this. The OD of the screw is chosen by the designer for this application.

You could make an epoxy impression of the thread and slice a thin section from this for examination on a shadowgraph to measure thread angle plus root flat.

Grind a thread boring tool to match and bore a solid nut with the requisite thread. Split and finish machine the outside after the thread has been tested for fit.

Mind you, I'd try to find replacement parts first, especially if your lathe is out of action and you have to rely on outside services for this job.

Arminius

mfisher · Jun 9, 2009

Anyone have a Grizzly 9x20?

I am fairly sure it is a trap. form. I was hoping it was some sort of standard so that I could get a tap. Half nuts are available, but BlueRidge (? I think it is them) wants $150 plus shipping for the original Zamak version. I was thinking about a short production run of brass/bronze if it could be done easily.

Grizzly lists for their 9x20 (which is almost a direct copy of the EMCO machine) half nuts that are SAE 9/16-16, but I don't think this is exactly right for the thread form.

Anyone have a Grizzly G4000 9x20 that cares to measure the lead screw. Half nuts from them are back ordered (big surprise there) until end of July. One report is that they are brass, and are $24. If the casting is the same, might be able to use them as a 90% complete part and just chase the proper threads?

Unka' George · Jun 9, 2009

Given that the problem is that the half nut is stripped, you may be better off to repair the half nut. The old machinists books describe "babbiting" the half-nut after "smoking" the leadscrew for release.

The newer solution is to use a castable teflon containing bearing material such as Turcite, Garlock or Moglice to do the same thing. [Be sure to use release agent on leadscrew!]

see
http://www.moglice-turcite.com/
http://www.cnczone.com/forums/archive/index.php/t-17946.html
http://www.moglice.com/articles/replication_techniques/wrotethebook.html
http://homemetalshopclub.org/news/apr03/apr03.doc

for general rebuild see
http://www.practicalmachinist.com/vb/showthread.php/turcite-teflon-159382.html

RioDPax · Jun 9, 2009

I'll sell you the half nuts for $2K. And throw the rest of the C8 in for free. LOL. I'm just down the road from you.

Actually I have a Clausing that I use most of the time and am going to sell it anyway when I get around to posting it on the web. It's embedded in this folder.

http://s201.photobucket.com/albums/aa28/RioDPax/Lathe Clausing 5936/

pmzielinski · Apr 15, 2021

Has anyone found a source for half nuts that work? Mine are crumbling.

lionelt · Apr 18, 2021

Emco Compact 8, 8E, V8 Lathes

You could try here.

Scottl · Apr 18, 2021

These were sold in both inch and metric versions.

The inch version was also sold under the Sears Craftsman label. They listed feeds as "Feeds via Lead screw .0035, .007, Per Rev." so if you can count the teeth on the feed gears you should be able to confrm the lead screw pitch.

Here are the full specs as listed in an ad I saw for a used Craftsman version.

Technical Data
Swing over Bed 8.2"
Center Height 4.1"
Swing over Cross Slide 4.6"
Hole Through Spindle .8"
Feeds via Lead screw .0035, .007, Per Rev.
Distance between Centers 17.7"
Head Stock Taper No. 3
Spindle Speeds 6 120/300/400/600/1000/2000
Thread Pitches Via Change Gears Inch: 10 - 44 --- Metric: .04 - 3.0
Tail Stock Taper No. 2
Tail Stock Travel 1.57"
Compound Travel 2"
Cross Slide Travel 4"
Spindle Motor HP - Voltage .5HP Forward and Reverse 110V Single PH.
Weight 152 Lbs

Bill D · Apr 18, 2021

I understand my Harrison m300 lathe was designed around 1970 as an all metric machine. But they made english versions with wierd leadscrews and cross feed screws.
Rather then make any changes to the main body they made the leads screw diameter the same metric diameter but the threads are english pitch. I think the lead screw is 18mm/ 6tpi or something like that. The half nuts are different to match the leadscrew. Other then that and the gear train no changes.
Bill D

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