Advice needed: Lathes

[jsdemar]

Bill, care to share some of your bolted nozzles and closure ideas? Not imagining how that can be accomplished.

See my post above. And several discussions in the research forum. If you’re a Tripoli member, see my presentation on the Tripoli website for making motor hardware. It’s under the media tab, TRATECH 2021.

 

[mjennings]

I picked up a used 12" Craftsman lathe that was a later model. Atlas made the lathe which Sears sold as a Craftsman. So far it's done pretty much what I wanted a lathe for. And the price was right, a friend gave it to me. It used to belong to his Dad I when his Dad died they decided to sell the farm, so my friend took the lathe apart and took it home. For years when I would visit him we would usually go to his workshop in the basement to see what he was working on. And for years it sat there still not assembled. So one day I suggested he give it to me, I'd put it back together, and when he wanted to use it he could drive to my place & use it.

Here's a link with lots of good pics about the later made Craftsman 12" Lathe.

http://www.lathes.co.uk/craftsman/page4.html

Nice I picked up a mini craftsman from the estate sale for a friends grandpa. He had one of those too, but I don't have the realest/cash for it. Beautiful machine still working, super quiet too. I got to figure the motor wiring for the one I bought.

As to the OPs question I have no recommendations but I learned in college working in the school's shop from too good machinist. Metal working takes lots of practice.

 

[TonyL]

I built my 54 and 75 mm hardware on a 7x10 mini lathe, purchased used. I did a number of modifications to it [including the longer bed]. Part of being a machinist is knowing how to use the tools one has. Buying a big bad machine does not make one a better machinist. The cheap Seig lathes work just fine if one knows how to use the equipment. I like my 8.4 x 16 Seig C4 much better than my 12 x 36 grizzly for fine work, but the grizzly can hog out metal a lot faster.

If you are new to machining I would recommend the 7x10, the mistakes are smaller, less costly, and less dangerous than some large machine. The Sherline seems like it should work, but never seemed a good enough value. Smaller than a 7x10 seems too small to me. Aluminum is pretty forgiving, so one can learn to cut smaller parts 'by feel' if one is generally conservative.

Little Machine Shop in Pasadena is a good resource and they support their products. I did my 8 inch parts on their high torque bench lathe [the original 16 inch C4, wish I had the 20]. The lesson is always go longer than you think you need, as tooling takes up space.

They told me I probably would not like the milling head attachment on my Seig C4. They were correct, however it served a purpose at the time, and I still use it for some things that are just easier to set up on it.

If you are concerned about cost, I would suggest that you farm out any long tube machining or find a way around it [see J DeMar's designs]. I have abandoned snap rings as not worth the trouble for my purposes.

One principle I have found remains true: you can expect to spend as much or more on tooling as you do on the lathe, so budget accordingly. The good news is that the tooling comes as you find you need it, not necessarily all up front.

br/

Tony

 

[prfesser]

See my post above. And several discussions in the research forum. If you’re a Tripoli member, see my presentation on the Tripoli website for making motor hardware. It’s under the media tab, TRATECH 2021.

I sat through John's presentation in 2021 and smiled and nodded my head throughout. Simple, but it works. His design is outstanding for those not wanting or not able to cut threads or snap ring grooves. In fact it's outstanding for those who ARE able to cut threads or grooves. On anything over 98mm you'll probably skip threads/grooves and go with bolted closures anyway. The idea has just been extended to smaller motors as well.

The design can be constructed with a drill press, or with considerable care, a hand drill.

 

[Zbench]

It’s pretty clever. Wondering why the motor stop wasn’t machined into the aft closure by making it .100” thicker than the case diameter? Would seem to be a very simple mod and not require turning down the exterior of the case. Which isn’t difficult but is one more step that could be avoided. Of course that places all the thrust on the closure but if the steel really is as strong as reported, shouldn’t matter. Perhaps instead of spending $1000 for my level 3 attempt in hardware this would be a worthy method.

 

[prfesser]

It’s pretty clever. Wondering why the motor stop wasn’t machined into the aft closure by making it .100” thicker than the case diameter? Would seem to be a very simple mod and not require turning down the exterior of the case. Which isn’t difficult but is one more step that could be avoided. Of course that places all the thrust on the closure but if the steel really is as strong as reported, shouldn’t matter. Perhaps instead of spending $1000 for my level 3 attempt in hardware this would be a worthy method.

Well...you can't use homemade or non-certified hardware for a cert attempt anyway. OTOH....who's gonna check?

 

[Rocketjunkie]

If you are looking for a lathe with an extra large spindle bore, look for oil field lathes. Usually about double for the same size as a standard lathe of the same size.

 

[OverTheTop]

I have a lathe that is 40" between centers. Will swing about 14" diameter if I remove the gap in the bed. Lots of tooling, DRO, quick-change toolpost.

My recommendation is to get the biggest lathe you can for the money. Bigger is stiffer and allows you to take bigger cuts which can save a heap of time on smaller parts. The DRO and quick-change toolpost are also fantastic for productivity and convenience. Buy them if you can afford it.

I also have a full height knee mill, and associated tooling etc.

FWIW I get far more use out of the lathe than the mill.

 

[Jim Green]

I am considering adding a metal lathe to my shop. As it will primarily be a hobby tool (for now), I do not want to spend a fortune. But I also do not want to spend good money on a piece of junk. i.e. Buy cheap, buy twice.

Experience? I get the concepts, but have never actually used a lathe (wood or metal). I do have lots of experience with other types of tools/trades incl woodworking, electrical, plumbing, auto repair, electronics repair, etc. I.e. I'm not that guy who owns one small tool box that I use to hang pictures.

Uses? It will primarily be used in research motor making. But I'm an avid DIYer so I can see where it could come in handy for other purposes. Like my brake rotors that currently need flattening.

@prfesser - I saw that you made a Gingery lathe. That project very much appeals to me, but the reality is that I have so many projects going that it'll never get done. Maybe when I'm retired.

Let's hear it! What advice do you have?

When I got a lathe I took a machining class at night at the local community college and learned at lot about how to use it. I took the class a second time and they let me make snap ring motors on their lathes. I even learned how to make a tool bit to cut the groove for snap rings. I bought a lot of used tooling on ebay.

Jim Green

 

[rharshberger]

Well...you can't use homemade or non-certified hardware for a cert attempt anyway. OTOH....who's gonna check?

Most of us who handle rockets frequently doing pre-flight safety checks aka RSO'ing a rocket are going to spot Research hardware almost immediately as currently there are only a couple of commercial certified snap ring vendors out there and their hardware is distinctive. Clones are a bit harder to spot especially if the person cloning the hardware has gone to the effort of anodizing the parts that are visible to the inspector. Here lately we have been seeing more of the AT-CTI cross loads both certified and non-certified ones it seems, those are harder to catch unless you really know your motors and their manufacturers.