Thread: Mars 5.5" lathe restoration

I happened across a Mars 5.5" lathe a couple of months ago at a local car wreckers and after some negotiation it is now resident in my shed awaiting some TLC. In all the research I've done, most of the information I've found has come from these forums and lathes.co.uk. I'd like to say a big thank you to thread authors neksmerj, onthebeachalone, Ueee, unixbigot and all the contributors who answered so many of my questions.

The lathe has been under a lean-to for a couple of years since it was last used, exposed to northern humidity and a little horizontal rain from Yasi. There's a light coating of surface rust over all the exposed surfaces that did not have paint or dried oil on them. It's going to take a while - probably the rest of the year - to clean up, but nearly everything appears straight and unbroken so I believe it's worth it.

The only structural damage I can see is the right hand support is fractured on the rear leg. There's evidence of the legs breaking completely off underneath the swarf tray support and being welded, but the rear leg has re-fractured across the top of the weld line. Most likely I'll plate and screw it since it's at the back and the weight if the lathe is pressing the broken faces together in normal operation.

The swarf tray is rusted through in the left rear corner but is still pretty solid overall. There's lots of rust flakes in it, but that'll clean up well with some electrolysis later. I'll either patch the hole, or perhaps turn it into a drain.

A couple of bits are missing, the handwheel handle on the tailstock, a screw/locknut on the toolpost slide and most of the change gears.

The gears are my main problem. You can see the 20t mandrel gear has two broken teeth in the photos, fortunately there is a "spare" 20t gear used as a spacer behind one of the larger intermediate gears and I can use it for the moment. Eventually, I'll need to buy all the missing gears and I'm having trouble working out exactly what I need to start looking for.

I can calculate with DP=(N+2)/OD that the gears are 14DP, and they match the 14DP profile printed in a gear catalog I have. What I don't have the skill to work out is if they're 14.5 or 20 degrees PA.

I'm also unsure on how many of each gear I need. Going by the brass plaque, I need a minimum of two 20t and 30t and one each of the others. More than half of the TPI combinations call for a pair of identical gears on the driver/driven shafts, but without working out the geometries of the shaft carriers I don't know the maximum or minimum size of the "extra" idler gear pair.

Can someone with a complete set of gears please let me know what "complete" is?

Regards, glen.


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Good project.

Should come up great.

Better stock up big on dust masks, you're gunna need them. Be eating rust for a while

Pity how people let stuff go without oil. Even late model virtually unused Asian lathes on Ebay are sometimes rust buckets - unreal.

Rob

Would think for the age it would be a 14 1/2 PA rather than 20 PA.

If you can take your 20 tooth gear and give it a clean.

Get your verniers and measure from the pitch circle to pitch circle (edge of the gear tooth) across 3 teeth,if you get a size somewhere around .547" ,give a bit for wear it will be a 20 PA.

If you do the same across only 2 teeth on the same gear and get a result somewhere around .322",give a little for wear it will be 14 1/2 PA.

Not doubting your counting but from what I can see from the photo that broken gear looks to have 22 teeth.

At a rough guess you might need a 60/55 compound,20,2x30,35,40,45,50 and 65.

I miscounted myself the first time, if you start from the first good tooth and go around clockwise it's easier to keep track of where you started. Here's a better picture, start counting from the top and you'll soon see.

Mars-20t.jpg

I've measured across what I think is the PC, and across three teeth I get 0.543 and across two I get 0.330. Since it's unlikely the tooth grows with wear, your 0.547 for 20 degrees is the best match.

...which is weird, as I had thought that it was old enough to be 14.5 as well. Of course, I could be measuring wrong, I'm taking it from just above half way up the tooth face where the shiny wear mark is.

I duplicated the brass legend in oocalc and used a formula to calculate TPI from the gears to double check my data entry, then counted each combination. I'll try to insert my table below:

TPI	8	9	10	11	12	13	14	16	18	19	20	24	26	28	32	36	40
Mandrel	30	40	40	40	20	40	20	20	20	40	20	20	20	20	20	20	20
Driver		30								38				35	40	40	50
Driven		20								20				30	30	20	30
Lead Screw	30	30	50	55	30	65	35	40	45	50	50	60	65	60	60	45	60

From this I see I need two 30t for 8TPI and 9TPI, and two 20t for 36TPI, plus whatever identical pair physically fits in the blank areas. The rest of the gears are all singles: 35, 38, 40, 45, 50, 55, 60, 65. The lathes.co.uk page mentions extra 63, 73 and 100 tooth gears to do metric and finer pitches as well.

Cheers, glen.

I would have plumbed for 14 1/2 degrees too, given the age of the lathe. Given the variation on both measurements it still may be. Another way to check is get a piece of plasticene (or blue tack perhaps), make it into a thin strip and then roll the gear along. With care (and luck) you should get the rack form of the gear. It will have straight sides so you can then measure the tooth angle.

It's worth pointing out that if you have to replace all of the gears, you can chose any pressure angle you like. Provided that all the gears that mesh with each other are the same it won't matter

Michael

Hi PA on teeth is 14 1/2 deg .I have to renew 2 tumbler gears on mine so will knock up some more when i make them be a couple of weeks got the cutter here and will make a longer piece cast.Keep in touch or p/m me John. ps must have been a weakness there with the idlers mine were sheared off about 10 on one 4or 5 on other. was abused by former owners. forgot same dp and pa as hercus myford drummond. got all the blank od measure here too.

Hi Glen,
Welcome to the small (but expanding) mars club. Your machine sure has seen better days but it will clean up. As John said, the gears are 14.5 pa 14dp. I can't help with the gears as mine has the bastardised metric leadscrew. What you are very lucky to have is the thread dial and all the guards, I don't think I have ever seen one with the change gear guard.
I have had mime for 8 odd years now, they are a good machine but like everything they have their faults. The biggest is the way the feed engages, like so many small lathes its a worm and wheel engagement, and under heavy loads it is very hard to disengage. The spindle bore is a bit small, and mine has a very course feed on the saddle handwheel (roughly 1 1/2" per turn).
Good luck with the resto, and please put pics up as you go, yours looks to be very early, I haven't seen the feed slot in the apron closed in like that, but your interlock is external. The later ones have the interlock internal.

Cheers,
Ew

Originally Posted by Ueee

Hi Glen,
Welcome to the small (but expanding) mars club. Your machine sure has seen better days but it will clean up. As John said, the gears are 14.5 pa 14dp. I can't help with the gears as mine has the bastardised metric leadscrew. What you are very lucky to have is the thread dial and all the guards, I don't think I have ever seen one with the change gear guard.
I have had mime for 8 odd years now, they are a good machine but like everything they have their faults. The biggest is the way the feed engages, like so many small lathes its a worm and wheel engagement, and under heavy loads it is very hard to disengage. The spindle bore is a bit small, and mine has a very course feed on the saddle handwheel (roughly 1 1/2" per turn).
Good luck with the resto, and please put pics up as you go, yours looks to be very early, I haven't seen the feed slot in the apron closed in like that, but your interlock is external. The later ones have the interlock internal.

Cheers,
Ew

Hi looks like these Mars like their name sake Mars Bars unhealthy for the dentition.Missing teeth seem to be the order of the day not sure to the reason ,my only opinion is sloppy and bad use.Material of gears I doubt as the rest is good stuff.Noted as quoted the thread indicator and bracket there missing on mine and gear cover too first one i've seen.also noted is it is a Hercules.Badges seem to be Great Scot Conrik.but they are 5'' C H.Also tail stock and apron traverse got ball type handles yours has filled in hand wheel and a spoked t stock wheel.Cheers John Mars club member.

I thought the Hercules model was much bigger, built in stand, thread gearbox etc.
Handwheels are odd, my t/s is the same (but my t/s is a ring in) but those solid handles are odd. Mine is also 5.5" center height, not 5".
Who knows how many were made, what's your serial numbers Glen and John?

Cheers
Ew

Edit my numbers are, front flat way DO338, rear flat way, L472.

Another thing I noticed is the rack for saddle travel goes either side if the gap [removable]piece right up to the gear end why who knows??? interesting as it doesnt do any thing I can see.

Originally Posted by Ueee

I thought the Hercules model was much bigger, built in stand, thread gearbox etc.
Handwheels are odd, my t/s is the same (but my t/s is a ring in) but those solid handles are odd.

Cheers
Ew

There was a Hercules sold on Ebay a few months back that had smashed handwheels (you may remember it) and they were the open web type (looking at the bits left on the machine).

If you look at the Hercules photo's on LathesUK for Mars, you will see that they did make solid handwheels, so it probably varies with the age of the machine.

Rob

Thanks for the warm welcome, I'm definitely going to hang around and update. My main hobby is restoring old engines and related machinery - Sundial, Champion, Fuller and Johnson, etc - so a rusty lathe is right up my ally.

I've taken an rack impression of the gear in modeling clay, and once it dries a bit more I'll section it for interest's sake, but since the consensus is 14.5 I'll work with that.

John, thanks for the kind offer, I'll pm you tonight.

I visited a friend with a Myford ML7 on the weekend, and was surprised how much smaller his teeth were than mine - roughly half the size on a similar diameter gear. I've been looking for "compatible" gears, and Hercus in Adelaide will supply them, though the cost is very high.

I don't actually need, or can probably afford, the entire gear set right now, but I have three mid-size gears and one 20. I'll post the pics and sizes later, but that'll be enough for a reasonably slow power feed. Thread cutting can wait, though 13TPI is one I'll need for the old engines.

The gears themselves are of varying quality. One in particular has huge voids in the cast iron and it's logical to assume that these faults are present in the tooth area as well as the rest of the gear.

The stand is similar to other Mars' I have seen, the left side completely enclosed with a cast door at the front for all the electrics and the right cast as an open pair of legs with bracing. Both are bolted through the swarf tray into the the bed. The electrics are all 3-phase, but the motor is a seized 1-phase with the cord snipped off flush with the grommet. There's a beautiful reversing switch in front of the changegear cover and it says 1 or 3 phase, so I'm going to try to salvage it. BTW, I only have a single phase supply.

Ew, I'd wondered where the serial number is, there's nothing visible through the rust. I take it they're either at the tailstock end or under the chuck? Other than that, there's a Queensland Education Department asset sticker. No idea if it was from a school or a TAFE, though.

The black knob on the tailstock lever looks a little out of place, it may be a replacement. I also just noticed that there's no knob on the back gear lever.

I already have a place picked out in the workshop, the biggest issue was the huge overhang at the back from the motor/belt assembly. I foresee a DC conversion in the (far) future...

Originally Posted by lgftsa

I duplicated the brass legend in oocalc and used a formula to calculate TPI from the gears to double check my data entry, then counted each combination. I'll try to insert my table below:

TPI	8	9	10	11	12	13	14	16	18	19	20	24	26	28	32	36	40
Mandrel	30	40	40	40	20	40	20	20	20	40	20	20	20	20	20	20	20
Driver		30								38				35	40	40	50
Driven		20								20				30	30	20	30
Lead Screw	30	30	50	55	30	65	35	40	45	50	50	60	65	60	60	45	60

From this I see I need two 30t for 8TPI and 9TPI, and two 20t for 36TPI, plus whatever identical pair physically fits in the blank areas. The rest of the gears are all singles: 35, 38, 40, 45, 50, 55, 60, 65. The lathes.co.uk page mentions extra 63, 73 and 100 tooth gears to do metric and finer pitches as well.
Cheers, glen.

Glen,

If you want to avoid making a second 30T gear, 20T gears on the mandrel and leadscrew will also give you 8 TPI
and
a 40T on the mandrel and 45T on the leadscrew will also give you 9 TPI.

Should you ever need to cut a 5/16 BSF thread, (22 TPI), a 20T on the mandrel and a 55T on the leadscrew will give it to you.

Frank.

Hi Glen,
The serial # is on the tailstock end.

There is a program download called lathe gears, it is programmed by a member called "vernonv", you punch in the gears you have, leadscrew pitch etc and it will give you gear combinations for whatever pitch you want. I'll find a link when I'm not on my phone.

Cheers
Ew (Ewan)