View Full Version : Building on a lathe idea

10-08-2019, 10:27 PM
So, I really need a lathe with rigid tapping ability and live tooling, but workshop space is restricted, and power supply sufficiently limited to rule out any cheap (aka big!) industrial options.

I could upgrade my Denford Cyclone to get rigid tapping, but that would mean a period without a functioning lathe.

A few months ago, while stood threading some parts on my much abused Clarke CL500, I thought the nice flat topped bed would be almost ideal to mount a couple linear rails on, and combine it with a gangtool setup would be somewhere in the ball park of what I'd need.
But after a bit measuring/sketching, I came to the conclusion the bed would likely be too narrow once a reasonably sized cross slide is fitted and loaded up with my ideal amount of tooling.

So letting the idea roll around in my head, the big issue is a suitable base. I'm not sure when I had the eureka moment, but that's where my recent post about Epoxy Granite comes in. Why don't I cast one?

At the moment, I've got as far as sketching some rough spindle/bed shapes, and working on the list of things that will need to be allowed for in the base mould/cast I.e. ballscrew/motor mounts, cable routing, way cover mounting screws (aka the little details that could potentially cause big headaches!).
I'm probably going to go for a slant bed build, as although it makes the casting/machining a bit more problematic, the swarf management is far better in the long term.

I'm still very much undecided about the spindle mount. I'm likely to buy a spindle from China, but I'm not sure whether a steel weldment, or another EG cast would be better.

So this thread is going to be somewhere to list my ideas/thoughts, and for anybody else to add in comments/advise/criticism (I already know this could be very likely end up in a reasonably expensive stupid idea!)

11-08-2019, 08:18 AM
Can't offer anything other than the knowledge that I'll be following this thread with interest.

09-09-2019, 12:54 AM
I will certainly be following this. I'm in the same boat and just starting to retrofit my Boxford 250 for production and build a custom lathe for prototyping . Although I don't need such a large work envelope so looking at a Denford Orac as a base

09-09-2019, 08:30 AM
If you have a nice flat topped bed and the only problem is that it's too narrow why not fit a ground plate on top of that giving you the required width?

09-09-2019, 07:26 PM
Cant add positive advice.

But my "simple" saddle swap to linear slides has so far cost 300+ work hours.

Over 12 fits / fiddle to the ballnut mount, and now servo motor mount, and shear plate/z axis connection.
New limits, fiddle with servo mount size to the saddle plate to clear the motor mount, ...

None of it is very "hard" but all of it is slow and heavy (parts assy == 30 kg).

10-09-2019, 12:12 PM
If you have a nice flat topped bed and the only problem is that it's too narrow why not fit a ground plate on top of that giving you the required width?

I did consider that, but my big concern with that approach, is I think realistically I need at least 18" of cross slide travel, so by the time you hang that length of cross slide over the back along with a servo motor, it's an awful lot of weight pivoting around some bolts that would be around 5" between centres.

I'm still at the point of adding sketches/notes/ideas to the notepad, and I now have a pretty good idea of the main layout, but I now need to find some time to do some modelling and some calculations to see if my plan is going to work.

29-04-2020, 09:21 PM
So this project has been bumped back up the list, after a slight mishap with my Cyclone (all I'll say is running a 25mm boring bar into the chuck wasn't a good move), and as I'm still waiting to find out if the parts needed to fix the Cyclone are available, this project is getting a lot of attention, as even if the Cyclone is fixed, I'd like the extra capability.

The current status is an A2-4 6000rpm spindle has been ordered, and is now crudely modelled in Fusion for the purpose of figuring out layout/dimensions.

I'm currently fleshing out a couple options.
My main use for this lathe is for gang tooling, with live tools, however I have discovered turrets are available for less money than I thought.

For those unfamiliar with lathes, the big benefit of gang tooling (row of tools mounted directly to the cross slide) is speed of changing tool. The limitation is part size, and the number of tools you can mount.
The benefit of a turret, is you can machine relatively far larger parts, but the tool changes take longer.

In terms of machine design, gang tooling doesn't need much bed clearance as long as tools are on the spindle centre height, whereas a turret requires far larger clearance. To give an example, the 8 position changers I've looked at, typically require 200mm clearance below the spindle centre height.

I'm currently weighing up whether I want to go to the hassle of designing that high a headstock, for something I might never use.
If I knew I would still have the cyclone, I probably wouldn't as the cyclone can handle up to ~120mm diameter parts with a fully loaded turret, whereas if I only have gang tooling capability, I'd be limited to either only a few tools with limited Z travel, or small diameter parts.

I'm now off to model a turret in Fusion

19-05-2020, 06:22 PM
This little 45kg lump got delivered today

The basic design is slowly progressing. Not quite as quickly as I'd hoped, due to lots of distractions, and quite a bit of contemplation over what layout to go for, but I think I've now got the basic layout decided on. I just need to design it in Fusion to make sure it's going to work as I think it will...

19-05-2020, 07:10 PM
That looks expensive.!!!!!!

19-05-2020, 09:37 PM
That looks expensive.!!!!!!

Not quite as much as I was expecting, but the 4 servos, 1 three phase stepper drive, and 16:1 reduction gearbox for the mill were cheaper.
However I did opt for Japanese bearings, and air freight, which was a third of the cost. I did wonder why the air freight was as expensive, until I seen the weight on the delivery label. No wonder the DHL driver didn't want to lift it out his van :eek:

19-05-2020, 10:14 PM
Ye, I don't get why air freight as gone up so much when there's 1000's of planes grounded with nothing to do. I've just been quoted $2000 to air freight 198Kg which is crazy.!! .. . . looks like it's going on a slow boat.!

19-05-2020, 10:30 PM
International freight is currently screwed because of a lack of passenger flights.

Normally the freight companies buy up surplus cargo space in passenger planes, but they're mostly grounded. So they're facing the option of either flying partially loaded planes, or queuing the cargo up until they can fill a plane.
The situation's that bad, some companies are flying passenger planes cargo only, and Airbus have even approved a system for strapping cargo to passenger seats to maximise cargo load without having to modify interiors.

19-05-2020, 11:20 PM
Yes but surely they are better flying half full with cargo than sat on the ground which will still be costing them.? . . . I think they are just pirates.!

20-05-2020, 10:01 PM
It's not costing the freight companies though.

Anyway, anybody want to design a lathe for me?
Just when I think I've got something worked out, I realise I've made a complete a$$e off something else.
I'm currently sat looking at my cross slide assembly, which is looking quite good, with the carriage shaped nicely to give enough height to fit the ballscrew in with support for the linear rail trucks, and how the f*$*g trucks stick out an inch past the edge of the cross slide. I can't belief I've only just noticed. Where's that head banging smilie when you need it?

22-05-2020, 08:14 PM
Any chance of some screenshots of the CAD or a video walk around? Sounds like an interesting project.

I know from my own projects that when you are developing something new there are always going to be issues along the way!

22-05-2020, 10:43 PM
This link might work - https://a360.co/2ZFxRoD

Progress has been pretty slow, as time is being split behind keeping up with orders using the manual lathe (I'm getting a dab hand at spinning dials to DRO readings!), and working through the list of things needed to get the big mill working (I might update that thread at some point). However as off Tuesday, I'll have 3 weeks to hopefully make a big dent in both projects.

I'm still working on the basic layout.
My big issue is I want to maximise X-axis travel.
Most of the parts I currently make could be done with about 120mm of travel and suitable gang tooling, however I'm wanting to add live tooling. I'll likely only need two live tools at any given time, and my original plan was to use VDI holders for everything with two driven, but having received a CAD model of a VDI30 holder, the closest spacing before access to the clamping screw becomes a problem, is 100mm.

I'm now thinking some form of interchangeable gang tooling blocks, then have the option of either driven VDI holders, or more compact driven tools more often found on gang lathes. The issue with that is tool changing becomes a bit more time consuming.

At the moment the design has around 350mm of X-axis travel. I could increase that to about 400mm, before I reach the limits of what I can machine. Another item on the list to work out, is potential tool layout so I can work out what kind of clearance everything needs.

Although that model shows everything flat, my plan is to tip it all up 45deg. Hence why the trucks aren't stacked directly on top of each other, plus it avoids bolt clashes between the trucks.

The big thing I'm not entirely happy about with this design, is unless I go to the hassle of a rotating ballnut, the servo motor is going to be hanging on the end of the cross slide.

So, as you can see from all that, there is a lot of contemplation needed while trying to juggle all my desired features, into something that will actually work.