Planning to by a lathe for a conversion, But what one!!??

[prcdslnc13]

When taxes get here, a lathe will soon be following. Ive built a CNC router but I have always wanted a lathe . Im trying to decided between the usual suspects

HF 7x10 (I like this one because I can buy it locally and its on sale for 350 right now)
Grizzly 7x12
Big Dog 7x14
HF 8x12

Now I know the second two are generally cleaner lathes even though they all come from the same floor. And now Im reading good things about the 8x12. What Im concerned with is the convertability of the lathe. I would like to keep manual function so Ill most likely be using dual shaft motors with handles on them. I would also like to keep the ability to thread, so how would I go about that?

Opinions?

[blades]

A better question might be related to your intended use and size requirements. An 8x12, although not substantially bigger in rated capacity to the 7x12, is a substantially better machine, if for no reason than it outweighs the 7x10 by a factor of 3:1. That in and of itself makes it a more stout machine. Also to consider is if you want or need to be able to move the lathe by yourself. The 7x10 is no problem, but the 8x12 requires equipment to move safely.

Regarding conversion, member roncat (I think?) did an amazing conversion on an 8x12. However, I don't recall if it was capable of running manual or not.

I am working on a 7x10 budget conversion that retains full manual control. My conversion is one of the only I've seen that doesn't utilize ball screws. MY BUILD
Threading is doable on a cnc converted lathe, but you'll need a spindle encoder and the appropriate software to run the lathe. Apparently the free version of Mach does not support threading.

[prcdslnc13]

I actually think your video was the one I saw on youtube that made me decide to go ahead and do this lol. What did you use for the encoder for your spindle? I was thinking of getting the bigdog because it already has a tach built in so Im assuming it has an encoder somewhere, But If I need something specific Ill save the 150$ and get the grizzly and add my own.

Work wise any of the above lathes will suit me perfectly. I am mainly going to be working with wood, plastic, and aluminum. Maybe steel later. What puts me off of the 8x12 is the lack of a variable speed motor. I am also planning to go with acme screws and delrin nuts, because I have them laying around. May go for ball screws later.

[blades]

Lol, glad to hear it was an inspiration!
That's all I really plan on cutting on my lathe is plastics, hardwoods, and aluminum. Given that's all you're planning on machining, the 7x should suit your needs just fine. Ballscrews are awesome, but completely unnecessary for my intended purpose right now. And that's exactly what I used: acme screw and delrin lead nut for the Z axis.
The encoder is no big deal at all. In fact, I may still have a spare encoder wheel sitting around I could send you if/when you start a 7x build. The optics for the encoder consists of a $26 board from CNC4PC (it's their C3 Index Pulse Card) and it interfaces with the G540 controller ( if you go this route, you need to specify if you will be using the device with a G540, so they send you the proper revision level board). I still have not yet completely finished my project, as I still need to put all the electronics in a housing. Had this done once in a PC case, but the PC took a dump. Now I just gotta find time to put it all back together again.

[prcdslnc13]

What are you using to control the spindle speed? Are you still using the change gears, and using the encoder so that mach see's your spindle speed and compensates accordingly? Or did you setup a closed loop driver so that your spindle is actually controlled through mach3?

I like the bigdog and grizzly because they both come with variable speed setup's and the big dog comes with a tach built on. If the tach isn't necessary I would rather save the 100 bucks for my conversion though

If you aren't going to need the encoder wheel I'd gladly take it off your hands. Im planning to start this in the next couple weeks. Depending on what lathe I get I'll probably order the lathe next week or the following, just depends on how the government takes with my refund haha.

I am most likely going with the 7x lathes just because of the crazy after market support for them, unless I can pick one of the 8x12's at my local HF.

[blades]

I'm going to hook up the spindle control to a switch so I can switch between full Mach spindle control or full manual. My HI-LO range gears are still in place, nothing there will change.

Here's a thread (more like a cry for help) I posted awhile back relating to Mach/G540 spindle control. Within that thread I posted a link to a very helpful thread regarding spindle control, which should tell you everything you need to know. Depending on how you did with Uncle Sam, seriously consider the G540 controller, as it's a very good unit and has lots of support.
http://www.cnczone.com/forums/mini_l...rol_-_can.html
The lathe with the built-in tach would be nice, but I wouldn't count on being able to hack it to the extent to actually be able to use it for program spindle control. The C3 index pulse board is cheap enough. Put the extra savings towards the G540

[prcdslnc13]

Thanks for the links! lots of info. Im still confused, but less not. So are you using the standard driver for your motor? like the one that came with it? And are you controlling the speed through software? Or are you just monitoring through software.

I have new kink in my decision. I was offered a 9x20 for the same price as a 7x12,and this one has already had all the rebuilds and kinks worked out. Its owned but one of the maintance mechanics that I used to work with. I think I will probably end up with that lathe, but Im still planning to cnc.

[blades]

Yes, still using the factory motor speed controller. And the Gecko G540 will also use it as well, I just have to wire into it at the speed control pot. The software will control the spindle speed, it is not really capable of monitoring the speed because it only outputs info (to the best of my understanding, anyway).

Sounds like a great deal on the 9x20!

[prcdslnc13]

I ended up getting a 9x20. Its looking like Im going to be getting a 2hp treadmill motor with a KB driver to convert it to variable speed. I am also looking at the encoder card you showed me with a PWM card also from cnc4pc that works with my driver to drive the speeds from the PC. Ill update more as I go!