Thread: MARS Atlas Lathe restoration

I have just taken on a project of restoring, reburbishing or at least getting in working order, an old Mars 'Atlas' metalwork lathe. I'll try to post information and pictures as the project progresses.

Mars details here.

Interesting because these were manufactured in Brisbane in the early 1900s. The Atlas is quite a large, commercial model. It looks like the one to the right in the picture of the Mars stand at an Australian machine-tool exhibition during the 1950s at the bottom of the above link.

The first problem is that someone has stripped the teeth on the low-ratio back-gearing lay-shaft gears, presumably by engaging the gear and failing to disengage the direct drive. So my first task is to find someone who can fix that.

If you cant find someone in Brisbane to do it for you I may be able.
I would need to have some dimensions of the gears in the headstock that are not damaged ,unless you allready know the DP and PA of the gears.

Thanks for that.

I do have a local gear cutting outfit looking at it. The challenge is that the layshaft is cast in one piece with a large gear (OK) on one end and a small one (with about half it's teeth missing) on the other end. We are still considering whether to machine a complete new layshaft out of a solid block, or machine the damaged gear back below its root diameter, shrink a sleeve over it and cut new teeth in that. The other damaged gear is the large one that drives the chuck and engages with the small gear on the layshaft (when back gearing is engaged). It also has a few teeth missing as a result of the same incident. We will probably have to get a complete new one machined because one face has a substantial rebate and would not provide sufficient backing for a shrunk-on sleeve. Anyway we'll keep poking at it. I am checking out the other various gearboxes and gear trains so we understand the full magnitude of the task.

The easist way is to turn the damaged gears off and shrink a piece of cast on recut the teeth,the sleeve should also be pinned just to be sure it dosent move.

With the larger bull gear I normally shrink a steel ring on ,pin it and then recut the teeth.

You dont really require a great deal of material on the bull gear when shrinking the ring on,but it is better if you can have at least 3mm below the bottom of the tooth.

Would probably expect that the PA is 14 1/2 degrees.

Depending on the size of the gears just as a rough guide to repair both gears is around $140.

Can only echo Pipeclay's response.

I have a Mars Great Scot, and went through the same process albeit a while ago. Great to see (yet) another Mars being restored. (I recently came acrosss an invoice for grinding the bedways for $310 in 1979.) Other Forum discussions at http://www.woodworkforums.com/f65/adjusting-replacing-babbit-bearings-mars-great-scot-lathe-brisbane-134688/ Seems many of these lathes were used in armament production and were marketed as a precision lathe in their time. ie adverts in SMH (1941) http://trove.nla.gov.au/ndp/del/article/17764634?searchTerm=Great Scot lathe&searchLimits=

Mark

I used to have one of those, Probably the same as yours, Mine was ex Australian Defence Force.
Matt

Thanks. Sounds interesting. I'll put some photos together and post them.

Originally Posted by matthew_g

I used to have one of those, Probably the same as yours, Mine was ex Australian Defence Force.
Matt

That's exactly the same. Thanks for posting the picture.

Originally Posted by pipeclay

Would probably expect that the PA is 14 1/2 degrees.

Would you mind expanding on what PA means? I'm a bit of a novice at this.

PA= pressure angle

Originally Posted by .RC.

PA= pressure angle

Thanks for that. Looks like I'm going to learn a lot about gears through this project.

Gear geometry can get complicated. Diametric pitch and pressure angle are the two main things you need to google/wiki.

I've added a few pictures a friend took to show the scope of the problem.

Looking at the Bull Gear picture it appears that there should be enough meat to remove the existing gear teeth and replace with a new ring.

A lot of the damage to the Back Shaft and Bull Gear on these lathes is caused by the removal process of Chucks etc from the Lathe spindle.

In most but not all cases users will engage Back Gear so as to LOCK the spindle to make it easier to remove chucks etc,at times these may be very hard to remove and sometimes a lot of load is put on these gears,causing them to shear teeth off.

Not saying it dosent occur,I dont believe it is generally caused by someone trying to engage the gears whilst the spindle is turning.

Originally Posted by pipeclay

A lot of the damage to the Back Shaft and Bull Gear on these lathes is caused by the removal process of Chucks etc from the Lathe spindle.

In most but not all cases users will engage Back Gear so as to LOCK the spindle to make it easier to remove chucks etc,at times these may be very hard to remove and sometimes a lot of load is put on these gears,causing them to shear teeth off.

Which leads me to wonder if there is a better way of locking the spindle to remove the chuck. I'd hate to get the gears fixed only to have someone strip them again.