Watchmaker's Lathe vs Vintage Hobby-lathe for making spinning tops

[blueice]

For a top to spin long, you want to maximize the amount of energy the top can start off with, minimize the rate at which it loses energy, and minimize the lowest RPM the top can sustain before toppling over. You maximize the starting energy by increasing the moment of inertia of the top about its rotational axis. You minimize the rate at which the top loses energy by, among other things, reducing air drag.
Increasing moment of inertia is simple, just add more mass and place it far away from the axis of rotation. However, more mass means a larger top with more drag, especially so if you add the mass to the top's width instead of its height. All this means, the denser the material, the more of an advantage you will have in spin time.
All of the longest spinning tops are made with a dense outer flywheel (Tungsten, Lead, Brass) and a light inner core (Magnesium, Aluminium, Wood). The core does not contribute as much to the moment of inertia of the top as the flywheel does per unit mass, and so it is best to make it light to reduce unnecessary friction at the tip of the top (which increases super-linearly with the total mass of the top).

I will keep an eye out for Atlas, but it is a bit big and unlikely to find for a reasonable price including international shipping. Things would be way easier if I lived in the UK or US hah. At this point I'm even considering getting a spindle unit, chucks, tailstock and motor and bolting them onto some steel plate. It will not be a lathe so much as a contraption used to make spinning tops alone, but it should beat pretty much anything less than 5x its cost in rigidity and power.

 

[Karl_T]

I am guessing you have no need for a tailstock?

If so, hardinge used to make some seriously rigid small lathes. They used to be used in industry strictly for second operations, not much use today. Would be able to turn tungsten like butter and hold tenths on tolerance. I have seen them go for scrap prices at auctions.

if this peaks you interest we could help find some model numbers to look for.

here's one quick example, not a good price here.

Hardinge 36" x 9" VBS Second Operation Lathe - Norman Machine Tool

HARDINGE 36″ x 9″ VBS SECOND OPERATION LATHE INVENTORY # 0784 MODEL: VBS S/N: V59-3731-3 SPECIFICATIONS: SPINDLE CAPACITY: ROUND HARDINGE 21SC COLLETS: 63/64″ HEXAGON HARDINGE 21SC COLLETS: 27/32″ SQUARE HARDINGE 21SC COLLETS: 11/16″ STEP CHUCKS: 1 1/16″ – 6″ JAW... Read More

www.normanmachinetool.com

here's another model that has a turret tail stock

HARDINGE DM-59 SECOND OP TURRET LATHE | eBay

6 POSITION TURRET. 440/3 PHASE POWER. QUICK RELEASE COLLET.

www.ebay.com

and another, more like what I was thinking about for you

https://surplusrecord.com/listing/acra-27afl-9-x10-second-operation-toolmakers-lathe-lever-5c-collet-closer-4000-rpm-1-hp-new-sm27afl-946289/

 

[blueice]

I am guessing you have no need for a tailstock?

It would help but I suppose it is not required. I need to hollow out the tungsten rod to make a ring, which I presumably could do by drilling a roughly centred hole into the tungsten with a drill and then finishing the job with a boring tool on the toolpost to achieve concentricity.

If so, hardinge used to make some seriously rigid small lathes. They used to be used in industry strictly for second operations, not much use today. Would be able to turn tungsten like butter and hold tenths on tolerance. I have seen them go for scrap prices at auctions.

Hmm those hardinges seem to be built like tanks that's for sure. Unfortunately they also weigh about as much, so they aren't an option. I need the lathe to be be small and portable, something that would not be a hassle to move. I am ever more coming to realize how big an ask that is when I also need to turn tungsten, with good concentricity at that.

I wonder how good the spindle slack on these bench grinders are:

800W Bench Grinder 4" Mini Polisher Lathe Metal Jewelry Polishing Machine | eBay

This Bench Polisher has pre-lubricated ball bearings and a dust-proof motor housing that makes it virtually maintenance free. load power：800W. 1 x Set of Bench lathe. Pure copper motor, load up to 2000W.

www.ebay.com.au

If these are any good, perhaps I could bolt one onto some metal baseplate, bolt on a compound cross slide with a toolpost, and achieve very good rigidity and power in a small and portable package, at the cost of versatility.

 

[Smithdoor]

I’m no help. But why tungsten?

Atlas made a little 6x12 metal lathe. They’re hard to find, but I’d keep my eyes out for one. I gotta believe it’s a step up from the unimat.

It was also under the name Sears
Most I have had name Craftsman.
I do think Atlas sold to many under there own name

Dave

 

[matthewsx]

It would help but I suppose it is not required. I need to hollow out the tungsten rod to make a ring, which I presumably could do by drilling a roughly centred hole into the tungsten with a drill and then finishing the job with a boring tool on the toolpost to achieve concentricity.

Hmm those hardinges seem to be built like tanks that's for sure. Unfortunately they also weigh about as much, so they aren't an option. I need the lathe to be be small and portable, something that would not be a hassle to move. I am ever more coming to realize how big an ask that is when I also need to turn tungsten, with good concentricity at that.

I wonder how good the spindle slack on these bench grinders are:

800W Bench Grinder 4" Mini Polisher Lathe Metal Jewelry Polishing Machine | eBay

This Bench Polisher has pre-lubricated ball bearings and a dust-proof motor housing that makes it virtually maintenance free. load power：800W. 1 x Set of Bench lathe. Pure copper motor, load up to 2000W.

www.ebay.com.au

If these are any good, perhaps I could bolt one onto some metal baseplate, bolt on a compound cross slide with a toolpost, and achieve very good rigidity and power in a small and portable package, at the cost of versatility.

Yes, it seems like your requirements will be difficult if not impossible to achieve with a "small and portable" machine. Perhaps it might make sense to have the rings you need produced by someone with a suitable machine and then add them to your lightweight core?

In my experience, building your own machine is harder than it first appears and having sufficient mass to make accurate cuts presents a real challenge.

Would tubing work?

Tungsten Tube | AMERICAN ELEMENTS ®

Tungsten Tube Product Information: Pricing Inquiry, Properties, SDS, Chemical Identifiers, Synonyms, Research, Related Products, Applications

www.americanelements.com

How about forming wire around your top?

.023” TUNGSTEN WIRE .58mm X 36”99.95% PURE!HIGH TEMPERATURE FILAMENT WIRE | eBay

99.95% PURE TUNGSTEN WIRE.

www.ebay.com

John

 

[silence dogood]

This morning, I was able to meet Gary and we discussed your situation. HIs first question was, are you going to be drilling? Then you need a tailstock that you can mount a chuck. Watch maker's lathes usually don't come with that type of tailstock. These type of tailstocks for watch makers' lathes are rare and expensive, if available. The Unimat could work, but it is really a hobbyist lathe. You could even use a small Chinese lathe. Whatever lathe you use, be sure to mount it on a rigid base. My 8x14 lathe is mounted on a heavy steel channel iron that is mounted on a very rigid bench. That does make a difference. The other things that both Gary and I agreed upon you need a wide speed control with adequate torque at slow speeds. Also make sure that you have good quality cutting bits and drill bits. Hope this helps.

 

[blueice]

I will need to hollow out the inside of the tungsten, for which I am planning to make a rough hole using an electric drill, and then use a boring tool held in the toolpost to finish the job. I watched the beginner lathing videos on Blondihack's youtube channel, and it seems that single point cutting tools are my best bet at achieving concentricity, which is ultimately the only type of precision I have to hit in a spinning top. As for cutting tools, I'll almost certainly have to use carbide with how hard tungsten is.
Your point about slow speed torque is interesting. I asked another topmaker who uses tungsten, and he said even his 550W motor sometimes has trouble with the material. Which means I probably have to mess with extreme gear ratios if these 100-200W hobby lathe motors to have any chance.
Or, I could just use a bench grinder with a chuck, and a compound slide with a toolpost, all bolted to some thick heavy base. That is probably the route I'll go with honestly. Do thank Gary for me, and thank you too.

 

[blueice]

Yes, it seems like your requirements will be difficult if not impossible to achieve with a "small and portable" machine. Perhaps it might make sense to have the rings you need produced by someone with a suitable machine and then add them to your lightweight core?

That is an option, but I don't know if it will be cheaper. I will be making several prototypes to find the optimal dimensions for spin time, and while I could outsource the tungsten machining, I will still need a lathe to machine the lightweight core, tune the outer shape of the tungsten flywheel with diamond files, grind the tip and polish the whole top. All while maintaining very good concentricity.

In my experience, building your own machine is harder than it first appears and having sufficient mass to make accurate cuts presents a real challenge.

Thankfully I only need to attach a headstock and compound slide onto some base, which I hope isn't too difficult to do. I can probably get away with not using a bed, given the limited scope of what I'm making.

Would tubing work?

Tungsten Tube | AMERICAN ELEMENTS ®

Tungsten Tube Product Information: Pricing Inquiry, Properties, SDS, Chemical Identifiers, Synonyms, Research, Related Products, Applications

www.americanelements.com

How about forming wire around your top?

I have contacted a couple suppliers, and they either don't sell in hobbyist quantities, or charge a ridiculous markup. And then there's international shipping, which is crazy high as they are not selling through amazon/ebay with whatever wizardry they do to keep shipping costs so reasonable.
But I will ask for a quote from the tubing supplier you linked. Wire is out of the question, no matter how good I am at winding, the finished top will simply not match the concentricity and balance of a solid flywheel. Not to mention the air gaps left between wound wires, which would reduce the average density substantially, at which point I might as well have used something like lead instead.

 

[Aaron_W]

Have you looked at Sherline? Their smaller 8" models are bigger than a Unimat, but a lot smaller than most of the other suggestions. They are more capable than a Unimat and accurate enough to be popular with watch and clock makers. I don't know about tungsten but I have heard of people turning titanium and stainless with a Sherline lathe.

There is a Sherline Dealer for Australia / New Zealand located in Aukland.

Precision Watch Company

Unfortunately a budget of $500 USD or AUD is not very realistic for any of the options you mention. In the US the lathe alone is close to your budget (if the $500 was USD), but the prices at the dealer above is significantly (20-25%) higher than the price direct from Sherline. I'm guessing that is just a part living in Australia though and something you are used to dealing with. Those prices do include some tooling, which it appears you have set aside additional budget for.

Sherline originated in Australia so you do have better odds of finding one used than some other options. Sherline also has an extensive range of accessories, far more than many small lathes. Something to consider when you have an unusual need.

 

[blueice]

Have you looked at Sherline? Their smaller 8" models are bigger than a Unimat, but a lot smaller than most of the other suggestions. They are more capable than a Unimat and accurate enough to be popular with watch and clock makers. I don't know about tungsten but I have heard of people turning titanium and stainless with a Sherline lathe.

I might have overlooked them as they look so similar to the chinese toy lathes made of extruded aluminium. Regardless, they are too expensive to consider. As for accessories, I have come to realize that I can get away with much less than a complete lathe, given my very specific use case. All I need is a headstock and a compound slide toolpost, held as rigidly as possible. I found out I have a very serviceable motor in my treadmill, so all that's left is the spindle in some housing, and the compound slide.