Craftex CT089 Lathe

[fatal-exception]

Hi all. Well, I finally got my new Craftex BT089 lathe up and running in my shop. I just thought that I would share my thoughts on the lathe after only 3 days of using it. I've read both good and bad about the lathe.

Here's a link to it: http://busybeetools.ca/cgi-bin/picture10?NTITEM=CT089

First off, it's a huge improvement over the mini lathe I've had for a few years. This is no supprise, seeing as it weighs about 10 times as much.

For a Chinese product, I was suprised how well it was finished. Mine came basically ready to run. There was only light grease that had to be cleaned off, and the oil in the gearbox is very clean. I will probably change it after a month or so of usage. It looks like some parts were painted after the machine was assembled, since there was paint on things like the dials and spindle, but nothing that couldn't be cleaned off.

I've read that some guys have dials that are a mix of imperial and metric. Not the case on this one, all the dials are labeled correctly in imperial. The backlash on the carriage is .002" and .001 on the compound, which is very good if you ask me.

I've used the 3 jaw, 4 jaw, and faceplate. They all fit properly on the spindle and are easy to swap. (It's a PITA to change the chuck on the mini lathe compared to this lathe.)

Once you understand the diagrams for the gear changing, it's a pretty quick task to change them for various threads. The gears fit well on their respective posts, and the adjustments are easy to get to. There is quite a bit of backlash in the drivetrain, but it all works smoothly.

The carriage and compound ways are scraped flat, which is nice to see. The gibs aren't polished, but they do have a nice finish.

The tailstock is heavy duty with an MT3 taper. The handwheel is large and very free wheeling. I should have built a cam lock for the tailstock on the mini lathe years ago.

The ways are in perfect shape, no dings or scratches. Oh, and they are "Hardened and Grinded". I love the Chinglish... Speaking of which, the user manual is utterly useless. This wasn't a surpise for me since I downloaded it and read through it before the machine arrived.

I guess the only major problem I see is the shifter to switch from fine longitudinal feed to fine cross feed. If you are fine feeding towards the chuck and you take it out of gear, if you push too far, the carriage will start to cross feed into the workpiece! This has to be a design mistake. I'll just have to be ultra careful.

I don't know why there is no threading dial. I'm contacting Busy Bee right now to see if this was something that should have been on the machine. There's a sticker expaining the threading dial on the carriage, but no dial. Regardless, I've found a suitable way to thread without one, without having to stop or reverse the motor, although this also works. I can explain it if anyone cares...

All in all, I think that I got good value for my money. Like someone else mentioned, some new bolts and a file are required to touch up some things, but in general, it's pretty good chinese quality.


Hope this helps some of you that are looking at the same machine.

The pictures are of boring the QCTP body to fit the compound slide, and a new handle for the compound.

Take care,
Paul

[Alan]

Are you still happy with the CT089?

I'm thinking about buying one .. they're on sale now for $1888, which is $100 more than you paid but $600 off the regular price.

I currently have a 9" Southbend but I'm looking for something new, and something with a wee bit bigger capacity without being too much longer, as I'm limited for space.


Also, what sort of mount is the chuck?


Alan

[fatal-exception]

Yep, there have been a few issues, but nothing major.

It should have come with the threading dial, but they sell it separately. I have one on order, but they tell me they are backordered till the end of this month.

The carriage lock is nothing more than a bolt head that you turn to tighten a shoe that locks against the underside of the ways. This is obviously not well thought out, but it should be simple to either put a nice handle on it, or come up with a cam system.

I had a few problems with the centrifugal switch not working on the motor, meaning that the starting cap was not disconnected from the circuit when the motor was spinning. This happened a few times, but hasn't happened for several weeks now. Im thinking that it was just dirty.

The chucks are bolted on with 3 M10 bolts.

Add a QCTP with the money you save, and it's a good lathe.

Paul

[Alan]

Thanks for the reply.

I have a nice enough Southbend with a leadscrew gearbox and a bunch of accessories, a full set of collets probably being the most desirable.

And I have a VERY small space for a lathe, which the Southbend JUST fits into.

But it is old and is a bit worn (tailstock wobbles a wee bit, cross slide lead screw has a bit more lash than I'd like and so on)

Also, I have no steady rest or follow rest and these are REALLY expensive to come by. And mostly, it has a small spindle bore, and that's really the biggest problem.

The CT089 is about the biggest lathe that I could possibly fit, and even that's going to take some doing.

I'm a wee bit concerned about losing the gearbox and more concerned about the limited number of threads that can be cut. The good news is that metric threads CAN be cut, which is another expensive proposition on a SB.

I was THINKING that being a CNC kinda guy, I could convert the CT089 to make up for the lack of a gearbox and add the ability to let the machine do tedious things automatically, like boring a BIG hole in hard stock, .025" at a time.

I was just about ready to spend the bucks when I started reading about a nylon gear in the geartrain ...


Alan

[fatal-exception]

Nope, there's no nylon gear in the geartrain. I checked.

CNC'ing it would be pretty strait forward, and something that I plan on doing over the next few months. I'm just going to put an additional ball screw underneath the lead screw. Nothing else will need to be touched. There's ample room to put a servo or stepper at the back of the carriage, and it's already covered with a sheet metal gaurd. Mounting an encoder on the spindle might be the most difficult part, since there's no real good place to put it in the gear change box.

Paul

[Alan]

1. Yeah, when I saw one in the showroom, this was my thought as well; no room to mount a sensor. A guy might have to look to magnetic sensing options.

However, I plan to toss the spindle motor anyway and replace it with the lovely 1 HP DC motor I currently use to drive the Southbend. It would not be a stretch to then add an encoder to that motor and use it as a servo, powered by a Gecko.

I did exactly this to my Sherline and it works great. Sometimes I run it off a standard DC motor controller, sometimes off the CNC controller.


2. I was visiting my good friend Dan Mauch on Friday and he showed me a lathe that he's converted. What was VERY interesting to me, that I didn't even notice at first, was that his ball nut is PERMANENTLY attached to the carriage!

His choice of ball nut and ball screw means that he does not have to disconnect/reconnect anything; cranking the carriage along spins the nut on the screw!


Alan

[fatal-exception]

I'm using a large DC motor on my milling machine powered by a Gecko for the spindle. Works well.

I guess I would need a VFD to use the motor that came with the lathe. I would use the 0-10VDC provided by the BOB to command the speed of the VFD. It dosen't look like single phase, 120vac input controllers are a common thing. Mabey upgrading to 3 phase would be a better option.

Would mounting an encoder on the drive motor work? There would be the backlash of the belt drive to deal with... (This would be like mounting an encoder to the end of a ballscrew, rather than the servo motor) I think maybe a rubber wheel that makes contact with the spindle, with an encoder on that might be the way to go.

The Nook ballscrews on my mill can be backdriven pretty easily. I'm sure that with a large enough pitch, you wouldn't even know that you are turning a screw and motor when using the carriage handwheel. Even if this were a problem, it wouldn't be hard to make a quick disconnect for the ball nut.

[Alan]

Variable Speed:

I've never seen a VFD for a single phase motor, and I can certainly understand why.

With a single phase motor, there needs to be some way to start the motor in a particular direction, which is usually an extra winding or a cap. The VFD electronics would have all kinds of problems dealing with this added reactance and so would be VERY expensive as a result.

Your choices (for variable speed) are a 3 phase motor with VFD or a DC motor with suitable controller. I use both in my little home shop, and my experience is that the DC motors give more power at lower RPMs, which is in fact to be expected.

The DC controllers themselves are also considerably less expensive than a VFD, but this is offset by the fact that a GOOD DC motor is considerably more money than a 3 phase motor.

Note that there are all kinds of DC motors, from good to crappy. For example, my lathe uses a Pacific Scientific motor that probably weighs 25 pounds. The 2 HP "treadmill" motor I _was_ going to use (until I saw it) weighs about 5 pounds.

The only 3 phase motors you can buy are good ones, because they're only used industrially.

The good news is that sometimes 3P motors can be had cheap and sometimes VFDs can be had cheap too. I bought a 2 HP 3P Baldor off eBay for $35.00 and a 3HP Mitsubishi VFD for about the same.

I use this pair on my little drill press, in place of the 1/2 HP Chinese motor that it came with. Sounds like overkill, but not really. I set the VFD to run at 120 HZ, which spins the motor at double speed. Now, at 1/4 the nominal speed, I get 1/4 the power, or back to the 1/2HP it came with stock. So I end up with an 8:1 speed range and never less that 1/2 HP.

Two little gotchas in this.

1. The theory and the manufacturers both say not all 3P motors will run with a VFD. I haven't found any that won't, but that's what they say.

2. Most motors rely on the fan at the end of them to keep them cool, and a 3P motor with VFD under load at low speed can certainly heat up. On my mill with a 3P motor (no bucks for the DC motor), I just mounted a couple of big computer fans aimed at the case, one on either side. Seems to work.


Backlash:

You're correct, backlash could be an issue. On my Sherline, I use timing belt pulleys and a timing belt; no more lash than anywhere else in the system. I would expect to have to do this here as well.

There are a few encoder "strategies" for lathes. The first is used by Mach3, and uses a single encoder. This essentially provides speed information, as well as a starting point (rotationally) and by all accounts, seems to work to create nice threads (the only reason for requiring a spindle encoder).

EMC purports to use whatever encoder you have, from 1 CPR to many CPR. Not sure about this, though, as I'm not an EMC user.

And I believe that DeskCNC will thread, using a multi count encoder mounted on the spindle.

Finally, there's the Electronic Leadscrew project that a guy might want to look at.


For my Sherline, I cheat. I still use CNCPro for DOS, that knows nothing about lathes or spindles. I call the spindle the Y axis and report in the steps PER INCH config the steps for 1 ROTATION.

The (simplified) GCode to make a 1" long 20 TPI thread then becomes

X1 Y20

A 1" long 1mm metric pitch thread (which I admittedly have not yet cut) should be

X1 Y25.4


Ballscrews:

Yeah, no problem making a disconnect, but you have to admit, a system that does not require it would be pretty neat.


Alan

[ninefinger]

Hi,

Its been a couple of years now since you posted this and I was wondering how the lathe is holding up for you?
They have them on sale this week and I'm considering getting one to replace my 3-in-1 that is doing only lathe duty since I made my cnc mill.

Any major issues since you last posted?
Did you ever cnc it?

Thanks,

Mike

[Alan]

Never did buy one. I was thinking about it, as my old post indicated, but never did pull the trigger.

After lots and lots of looking and dreaming and humming and hawing, I ended up with an 11x25 Emco and am REALLY REALLY happy I did. This was my first "modern" machine not made in China and MAN is there a difference.

I'm afraid the Austrian quality has spoiled me and I can't imagine buying a Chinese machine again. Don't get me wrong, the Chinese machines are capable of good work and are certainly good value, but there IS a quality difference, and it's hard to appreciate just how big a difference until you've used one for a while.

Alan