Lathe for capsule making

[Murdock]

I'm fascinated by capsules and would like to get into manufacturing some myself. I'm not interested in mass producing or selling. Just for myself.
I've read a few things here and there but would like to ask some of the veteran capsule makers or experienced machinist what the main criteria would be for a good capsule making lathe. Or maybe even some models they can recommend.
I know rigidity is key for precise working.
But how much precision in the machine is really needed? Especially if I'm not into mass producing, so speed of work or repeatability is not so important. I'm patient and kinda pedantic ;D
Ideally I would also manufacture some mic bodies myself and I think a thread cutting capability would be a great plus.
So do I really need a 500KG 5000,-Euro precision lathe for prototypes or are there "workarounds"with "cheaper", less precise lathes?
I've read about a few "tricks" like turning between centers for better accuracy.

Let's say I would like to make a 12mm diameter brass backplate with a machined 10 micron gap. Would that be possible with a hobby lathe a la Wabeco or Emco?

Eager to read your experiences and recommendations!

PS: I will also get a mill but that's another story.

 

[soliloqueen]

Anything is possible on any lathe if you're willing to do it 20 times!

The issue is, things like cutting the gaps on a backplate require facing precision, that is to say precision "front to back" along a tubular workpiece. Most lathes are not designed to be as precise this way as they are around the circumference, by design. Even as you go up in advertised precision, they mean circumference. Depending on the design of the capsule, machined gaps are more of a "look what we can afford to do" detail than a necessary part of the design...

I've heard of people using all sorts of stuff to do capsule work. You might be able to do some mods to a cheap lathe to get better facing precision, like commission tighter screws. Not my area of expertise. Hope someone more knowledgeable can chime in.

 

[Murdock]

Anything is possible on any lathe if you're willing to do it 20 times!

The issue is, things like cutting the gaps on a backplate require facing precision, that is to say precision "front to back" along a tubular workpiece. Most lathes are not designed to be as precise this way as they are around the circumference, by design. Even as you go up in advertised precision, they mean circumference. Depending on the design of the capsule, machined gaps are more of a "look what we can afford to do" detail than a necessary part of the design...

I've heard of people using all sorts of stuff to do capsule work. You might be able to do some mods to a cheap lathe to get better facing precision, like commission tighter screws. Not my area of expertise. Hope someone more knowledgeable can chime in.

Thanks soliloqueen, hoped you would chime in!
Yeah, I also thought about just using chims but still, the backplate surface has to be quite flat, doesn't it?
So are you saying getting it flat is "easy" but cutting a precise amount is the hard part?

 

[soliloqueen]

Thanks soliloqueen, hoped you would chime in!
Yeah, I also thought about just using chims but still, the backplate surface has to be quite flat, doesn't it?
So are you saying getting it flat is "easy" but cutting a precise amount is the hard part?

Getting it flat is done with lapping. You don't even use the lathe for that. Ideally, it's mill, anneal, cut, lap I should think? Someone else should jump in. You can heat the stress from the milling out so that the plate doesn't bend when you cut the face. I've never actually checked how necessary this is if you're going to lap it anyway, that's just what seemed most reasonable and it worked immediately.

 

[molke]

I’m neither a veteran capsule maker nor or an experienced machinist, but I did some research in this area as well. I got a cheap Proxxon PD250, that kind of works if I try hard enough, but I wouldn’t recommend it. For capsule making, I would probably go for a well equipped (older) watchmaker’s lathe if I had to start all over again, but that’s mainly because I’m very limited in space. Note that even the most basic tools and attachments will most likely cost at least as much as the lathe itself. Actual recommendations for models would depend very much on size, weight, and price requirements.

From what I’ve read and tried for myself, cutting just 10 µm may not be the best option since tools seem to cut better if there’s a minimum depth.

Getting it flat is done with lapping. You don't even use the lathe for that

Maybe it’s just a language problem (as for almost everything in Germany, there’s a norm for the definition of “Läppen”), but does lapping in capsule making refer to actual lapping (as e.g. in the second type here) or just grinding flat?

 

[soliloqueen]

I’m neither a veteran capsule maker nor or an experienced machinist, but I did some research in this area as well. I got a cheap Proxxon PD250, that kind of works if I try hard enough, but I wouldn’t recommend it. For capsule making, I would probably go for a well equipped (older) watchmaker’s lathe if I had to start all over again, but that’s mainly because I’m very limited in space. Note that even the most basic tools and attachments will most likely cost at least as much as the lathe itself. Actual recommendations for models would depend very much on size, weight, and price requirements.

From what I’ve read and tried for myself, cutting just 10 µm may not be the best option since tools seem to cut better if there’s a minimum depth.

Maybe it’s just a language problem (as for almost everything in Germany, there’s a norm for the definition of “Läppen”), but does lapping in capsule making refer to actual lapping (as e.g. in the second type here) or just grinding flat?

Actual lapping. You could also do flat honing. You could grind flat provided you have a very fine grinder but only if the backplate is all metal. You can't traditionally grind composite materials flat because of thermal and mechanical stress.

 

[blue_luke]

Amateur machinist and mic builder here.
I own a pretty decent Chinese lathe and I tried to build a capsule according to an old wireless world article about a DIY microphone.
(Here is the original article: http://www.sdiy.org/oid/ldc/Debenham-StereoCondenser.pdf)
The plans are complete and the schematic (tube) is very well designed.
I have built one mic but quite a few capsules and found that the main problem is not the tooling or the fabrication, the problem is of repeatability and consistency....
The capsules I have built are all sounding somewhat OK, but all different... I ended using Microphone parts CK12!
But it was a lot of fun! and very educative.
The lathe I used is a Precision Matthews PM1228, which is nice hobby machine, quite riggid and stable. And someone said that you will invest as much, if not more in tooling than the actual cost of the machine, way more in my case!
Good measuring instruments are very expensive, then all the cutters and all the other accessories... I have more invested in my little shop that it would cost for a nice new pair of Neumann U-87!!

 

[Tim Campbell]

 

[Rusan]

I have about 7 years of full-time professional machinist experience, plus another few years of mixed machining/welding/fabrication. During my 5 years in tool and die, plus-or-minus .0001" (.00254 mm) was an "everyday" tolerance, and occasionally it was only half of that: .00005"/.00127 mm.

I've used dozens of lathes over the years, including the Enco brand you referenced. Enco and other relatively inexpensive Chinese lathes are okay when new, but you'd be wise to avoid the temptation to save money by buying a used one. Like other similar brands made in that same Chinese factory, they wear out quickly with daily commercial use and become loose and sloppy, hence there are many on the used market for cheap. New is much more expensive, but well worth it. And, as blue_luke and molke noted, don't forget that tooling and measuring instruments will cost you a LOT of additional money.

He mentioned the Precision Matthews brand he owns, which is also available under the Grizzly brand name here in the U.S., and I'm sure with other brand names in Europe. They're perfectly good machines with more-than-adequate rigidity and accuracy for what you're wanting to do, especially since you'll be turning brass, which machines very easily. No matter which machine you get, you'll first want to learn about proper feed and speed (chip load and surface speed), then make various cuts to verify the machine's stability and accuracy. Sometimes, the gibs on even new machines will need to be tightened, or even removed, flat-stoned and reinstalled. Gibs are the long, tapered wedges of brass used to adjust the tightness of the carriage/saddle, cross-slide and compound slide atop the ways they ride upon.

If it's available in Germany, you'll want to use what's sold as "360 Brass annealed" here in the U.S., which is a basic 60/40 copper-zinc alloy with 3% lead added to make it extremely free-machining. Plus, it has no internal stress and doesn't work-harden, and is a dream to work with.

If your turning tool's carbide insert has the proper, very small radius and positive rake angle, and the lathe's carriage and compound are locked in place before you begin your facing cut, with 360 Brass you should have an extremely flat facing cut with zero visible machining marks. If necessary, to get your backplate absolutely perfectly flat after facing, lap it with an India stone (a very fine aluminum oxide stone) lubricated with WD-40 before removing it from the lathe chuck. With the spindle turning at about 200-250 rpm, lightly hold the India stone flat against it, slowly moving it back and forth along its length, stopping a few times to wipe clean and relubricate. It shouldn't take but about a minute. After parting it off and drilling it, you could then lap the finished backplate between two India stones or a plate of glass and a stone.

 

[soliloqueen]

A capsule backplate would indeed be child's play for a tool and die shop or a watchmaker. The tolerances required are the broad side of a barn for T&D. The biggest issues come from bringing costs down at volume. My advice up there is how dozens or hundreds of them are done at once and with different alloys. If you're doing it as a hobby, there's nothing stopping you since that's not necessary. You will just need to do a lot of trial and error, research and advice-seeking.

 

[Tim Campbell]

I built this K67 type with aluminum backplates using just a drill press, hand lapping and foil from a capacitor about 2001. Though it is sloppy it worked very well.

 

[Murdock]

Thanks for all the input so far!
I know about the tooling cost. That's one thing you read over and over when searching for lathe recommendations.

I have about 7 years of full-time professional machinist experience, plus another few years of mixed machining/welding/fabrication. During my 5 years in tool and die, plus-or-minus .0001" (.00254 mm) was an "everyday" tolerance, and occasionally it was only half of that: .00005"/.00127 mm.

I've used dozens of lathes over the years, including the Enco brand you referenced. Enco and other relatively inexpensive Chinese lathes are okay when new, but you'd be wise to avoid the temptation to save money by buying a used one. Like other similar brands made in that same Chinese factory, they wear out quickly with daily commercial use and become loose and sloppy, hence there are many on the used market for cheap. New is much more expensive, but well worth it. And, as blue_luke and molke noted, don't forget that tooling and measuring instruments will cost you a LOT of additional money.

He mentioned the Precision Matthews brand he owns, which is also available under the Grizzly brand name here in the U.S., and I'm sure with other brand names in Europe. They're perfectly good machines with more-than-adequate rigidity and accuracy for what you're wanting to do, especially since you'll be turning brass, which machines very easily. No matter which machine you get, you'll first want to learn about proper feed and speed (chip load and surface speed), then make various cuts to verify the machine's stability and accuracy. Sometimes, the gibs on even new machines will need to be tightened, or even removed, flat-stoned and reinstalled. Gibs are the long, tapered wedges of brass used to adjust the tightness of the carriage/saddle, cross-slide and compound slide atop the ways they ride upon.

If it's available in Germany, you'll want to use what's sold as "360 Brass annealed" here in the U.S., which is a basic 60/40 copper-zinc alloy with 3% lead added to make it extremely free-machining. Plus, it has no internal stress and doesn't work-harden, and is a dream to work with.

If your turning tool's carbide insert has the proper, very small radius and positive rake angle, and the lathe's carriage and compound are locked in place before you begin your facing cut, with 360 Brass you should have an extremely flat facing cut with zero visible machining marks. If necessary, to get your backplate absolutely perfectly flat after facing, lap it with an India stone (a very fine aluminum oxide stone) lubricated with WD-40 before removing it from the lathe chuck. With the spindle turning at about 200-250 rpm, lightly hold the India stone flat against it, slowly moving it back and forth along its length, stopping a few times to wipe clean and relubricate. It shouldn't take but about a minute. After parting it off and drilling it, you could then lap the finished backplate between two India stones or a plate of glass and a stone.

Thanks alot for your input!
It's encouraging to hear, that those cheaper lathes are more than adequate.
I'm based in Germany so don't have access to these Grizzly/Precision Matthews brands but there are probably similiar or the same machines with a different brand name on it here like you said.
I thought about getting older lathes like those highly praised Schaublin 102. But their condition probably varies quite a bit and I'm far from knowledgeable enough to discern a good or a bad machine...

I’m neither a veteran capsule maker nor or an experienced machinist, but I did some research in this area as well. I got a cheap Proxxon PD250, that kind of works if I try hard enough, but I wouldn’t recommend it. For capsule making, I would probably go for a well equipped (older) watchmaker’s lathe if I had to start all over again, but that’s mainly because I’m very limited in space. Note that even the most basic tools and attachments will most likely cost at least as much as the lathe itself. Actual recommendations for models would depend very much on size, weight, and price requirements.

From what I’ve read and tried for myself, cutting just 10 µm may not be the best option since tools seem to cut better if there’s a minimum depth.

Maybe it’s just a language problem (as for almost everything in Germany, there’s a norm for the definition of “Läppen”), but does lapping in capsule making refer to actual lapping (as e.g. in the second type here) or just grinding flat?

About watchmaker lathes. Most of these are pretty small. Sure, the parts they have to turn are pretty small, but aren't these smaller lathes less ridig and therefore also less precise? Or is it about the turn speed?

I built this K67 type with aluminum backplates using just a drill press, hand lapping and foil from a capacitor about 2001. Though it is sloppy it worked very well.

So you're saying you milled the gap in to the backplate with your drill press? Or is there no gap in the first picture? Just a trench?
And what about the picture of your lathe? What do you want to tell me with that?

 

[Tim Campbell]

No I used mylar spacers for all the gaps. You can easily make a capsule with just hand tools.
The lathe is one that I use these days sometimes. You asked about lathes. This one is overkill. I have used cnc machines the last almost 20 years.

 

[molke]

I'm based in Germany so don't have access to these Grizzly/Precision Matthews brands but there are probably similiar or the same machines with a different brand name on it here like you said.

These are presumably the same rebranded Sieg machines (with some minor modifications) and are available in Germany as well.

I thought about getting older lathes like those highly praised Schaublin 102. But their condition probably varies quite a bit and I'm far from knowledgeable enough to discern a good or a bad machine...

About watchmaker lathes. Most of these are pretty small. Sure, the parts they have to turn are pretty small, but aren't these smaller lathes less ridig and therefore also less precise? Or is it about the turn speed?

Weight certainly helps, but it’s not the same as rigidity or precision. I guess it would be easier to get precise parts from a 50 kg Leinen WW83 than a Mini Lathe or even larger Chinese lathes. Turning speed is one consideration (2000 rpm max might be a little on the low side for 12 mm brass); nice collets are another. Overall build quality usually doesn’t make it into the feature list. Since you mentioned Schaublin, a 65 or 70 would probably suffice as well. All of these are quite expensive when new and even when used, and then you’d somehow have to judge their condition. There used to be other options in this weight class. In Germany, a Saupe DMT 160 can sometimes be found cheaper.

 

[AUDIO FREQ]

I thought about this when I watched Soyuz capsule manufacturing video on youtube. Such a satisfying image, of a brass cylinder being machined down to precision flatness. But then again, i've watched too many lathe accident videos on reddit...I have issues.

 

[soliloqueen]

I thought about this when I watched Soyuz capsule manufacturing video on youtube. Such a satisfying image, of a brass cylinder being machined down to precision flatness. But then again, i've watched too many lathe accident videos on reddit...I have issues.

I love that video because they make a big hullabaloo about the special Russian lathe cutting and then completely gloss over the lapping that happens afterwards which is what actually makes the capsule work properly.

 

[AUDIO FREQ]

I love that video because they make a big hullabaloo about the special Russian lathe cutting and then completely gloss over the lapping that happens afterwards which is what actually makes the capsule work properly.

I don't think it was meant to educate lol.