The sows ear, a Clarke Metalworker Mill / Lathe conversion to cnc

[FatFreddie]

Some pictures from my conversion of a cheap and nasty Clarke Mill / Lathe.

I've called it the sows ear because I don't think any amount of effort will turn it into a silk purse. It's also a bootstrap project - I've had to keep it working during the process since it's the only metalworking machinery I've got. The Z axis is the best example of this.

It's very much an experiment / work in progress as you will see.

Starting point...

1685

X axis - doesn't look too bad but the coupler is pretty rubbish so it'll need remaking.

1686

The Y axis works quite well apart from the tendency of the axis to bind if anything other than the vice is bolted to the milling table.

1687

The Z axis will make you wince but it's accurate enough to make the proper brackets which would take ages by hand.

1688

It's actually working a lot better than I thought it would. Backlash is approx .016mm on the X and Y axes and about 1 mm on the Z (and it wobbles) but that should be sorted soon. The worm gear from the existing fine feed will never provide great accuracy though so I may need to go to an external leadscrew.

Electronics are a system 4 kit from DIYCNC and which has worked great with EMC2 as the controller.

Don't be afraid to take the mickey - I'm under no illusions :smile:

Mark

[Lee Roberts]

Looking good, next i would look at making a new mount for the last pic/motor. Maybe somthing that fits better to the shape of the machine, like the part you have made in wood but turned the other way with a flat to mount the motor to ?

[Robin Hewitt]

Backlash is approx .016mm on the X and Y axes and about 1 mm on the Z (and it wobbles) but that should be sorted soon. The worm gear from the existing fine feed will never provide great accuracy though so I may need to go to an external leadscrew.

Hi Mark

Nothing wrong with a bit of turd polishing :naughty:

Just a thought but you might be able to improve it a lot by changing one spring. A temporary fix perhaps so you can use it to remake the parts properly.

Usually the quill return acts on the pinion rather than on the quill.

If you put a plate on the bottom of the quill then replaced the quill return spring with a snogging great extension spring pulling up, well off centre on the plate that would have two effects...

1: The gear train would be in tension and more able to resist the tool pulling it down.

2: it would apply a twist to the quill and reduce the wobble.

If you have a sloppy quill, thick grease is your friend.

Happy polishing :smile:

Robin

[FatFreddie]

Cheers Robin :-)

I should have made myself clearer - the quill is fine (good even which is a surprise) it's the bracket that wobbles (very visibly when plunging). I've already used it to make another one in aluminium which I hope to fit tonight. There is a return spring on the quill which, as you say, could be stronger - I think machining grabby materials could be a problem but there is a lock on the quill I can use if necessary and the idea of a supplementary spring is a good one.

I should have done this years ago, it's converted a machine that was border line useful and a pain to work with into one that has many uses, is fairly accurate and is a joy to use. Turning accurate diameters was always a pain with it but now I can make a test cut, touch off to the measured diameter and press go and the jobs done - within 0.04mm first time.

Total cost for the conversion so far is about £400 - bargain :-)

Mark

[FatFreddie]

Well the Z axis bracket has made a big improvement.

1698

Though the exposed thrust bearing with one race missing is still a bit grim :-) Must get a needle roller equivalent.

1697

Running an 8mm spotting drill at far too slow a speed got me this

1699

Need to look into smaller bits and a Dremel adaptor for this sort of work but I'm quite impressed so far - the EMC2 anti backlash algorithm was very evidently working during the making of this.

Mark

[FatFreddie]

Well, I've decided to really put a shine on this turd so it's getting ball screws on the X and Y axes (the Z axis is probably beyond redemption so the plan is to use this to build a gantry mill and then just use it as a lathe).

The current Y axis leadscrew is in such a bad state it's missing steps even at very slow feed rates so I'm making some rough brackets for the Y axis and then I'll make some better ones when it's going.

During testing last night I was bitten by the ballscrew demon - ran the nut off the end of the screw and ball bearings dropped out of the end! I tried poking them back in but there are three separate loops on the ones I have so I had to stick them in place with grease and then gently insert the holding tube - much quicker to describe than do!

Hopefully get a metal cutting test in tonight - pictures to follow.

Mark

[m_c]

then just use it as a lathe


That's what I'd recommend!
I think I had the milling head on mine for about 1 month, used it once or twice, bought a proper milling machine, and the milling head has lived in a box under a bench somewhere since (I don't even know what bench it's been that long!).


Regarding the Y-axis (in lathe terms it's actually the Z-axis), have you ever had the carriage of?
I had lots of problems trying to adjust mine, and I eventually found out the gib strip was bent, which was causing all the problems. I made a new gib strip from a bit gauge plate, and it made a huge difference (could adjust play out, without it starting to bind). I also converted it to use a couple angular contact bearings at the handle end, to replace the cheap and nasty bush set-up.
I used to have a website which showed all the mods I'd done, but I fell out with the webhost and have never reuploaded them anywhere. If you want to see them, I should still have the pages on a disk somewhere.

However, I've got no plans to convert mine to CNC, as I find it ideal the way it is for what I use it for.

[FatFreddie]

I think I'm stuck with the milling head for now, no room for anything else - I'm probably going to have to extend the garage before I start the gantry mill :-(

The X / Y leadscrew bearings have already been replaced - the ball bearing ones will have angular contact bearings. The mounting brackets are very different to standard (the ballnut has to go at the back of the table due to space constraints). I've had the Y axis completely apart several times - the gib strip seems ok. The X axis is next but that is behaving better than the Y so I'll get that sorted first (may have to gear the stepper down as I've gone from 2mm to 5mm pitch).

Thanks for the offer of the web pages but I think I've already replaced most of the bits. Have you done any work on the lathe spindle? It's making an annoying clicking noise since I removed the power feed clutch (which never worked properly) - I've got a schematic but it's not very clear and I don't really want to strip that bit down unless I have to.

I'll post piccies when I've got it to a less than totally embarrassing state :-)

Cheers,
Mark

[Swarfing]

Mark

Don't knock your efforts on this as i keep looking at my cl430 and wondered if i could polish it enough to run as a cnc lathe? Even delrin nuts on the existing screws would make it run better. Whats peoples thoughts could we polish hard enough to have a super clarke turd tribe on the go?

[m_c]

The lathe itself is pretty good, and polishes up quite well.
I'd quite happily buy another one, however it would only be the basic lathe (CL430), just so I don't have to endure the mill drive bits endlessly rattling.

As for the spindle, I've never touched mine. It works, and the only noise I'm aware of, is the mill drive changeover rattling.

[Swarfing]

Well i have a choice either sell it for a lot less than i paid for it or convert it? Mines very quiet and runs smooth, not happy with the lead screws on the saddle and cross slide. The main lead screw is poorly fitted at the belt end but in general could polish up very well. I have a 13" southbend that does everything i need so was going to get rid of the small lathe but as a cnc machine would work out very well. It is all about justifying it?

Mark
Are you going to complete the rest to make use of it as a CNC lathe as well? would be interested on what you would do about the motor and control?

[m_c]

I'd convert it to CNC (I'm actually keeping a lookout on ebay in the hope I can pick one up cheap), as I think they're an ideal size. Not too big that a conversion is going to cost a fortune with big steppers/servos, yet large enough to handle dealing with big lumps of steel.

The main leadscrew should be poorly fitted at the belt end, as it should be free floating in the coupler. End float is controlled by the cheap and cheerful bush type set-up at the handle end, which as standard is useless. However, the collar on the leadscrew at the handle end, is the perfect size for mounting two angular contact bearing back to back in a new housing, which makes a huge difference to backlash.
And the main nut is a split nut, with a bolt to adjust out play, however you've got to maintain a couple of thou play in it, otherwise it just wears quicker and/or binds.

[FatFreddie]

Mark
Are you going to complete the rest to make use of it as a CNC lathe as well? would be interested on what you would do about the motor and control?

Yes, I've fitted cheap 16x5 ballscrews to the X and Y axes and it works fine as a CNC lathe.

The y axis ballscrew made a big difference, the original arrangement is poor in many ways, 12mm isn't big enough to take the cutting forces without binding so it was loosing steps. The X axis ballscrew is an improvement but not so much of one.

The ballscrews are the cheap chinese ones from Zapp - they seem pretty good for the money. The seals are rubbish so I've protected the leadscrew on the Y axis and on the X axis I've made seals from kitchen sealant which seem to work ok so far but not many cuts under it's belt yet :-)

[Swarfing]

Nice one Fred certainly given me food for thought now? Still what have you done about the motor control? DC motor? or large servo?

[FatFreddie]

Nice one Fred certainly given me food for thought now? Still what have you done about the motor control? DC motor? or large servo?

No mods to the spindle motor yet - I'm going to build a gantry mill from this next and then just use it it as a lathe so I may just leave it as it is.

[Kai]

Hey I have one of those in my garage when you have done yours can you pass me some plans and what to and not to buy lol.
I see you are in sheffield I'm just in hull not far unless there is a lot of snow hehe.
I have two other machines both denford a starmill and a starturn they are good for the stuff I want to do.
All I have to fix is the chair keyboard interface now then everything will be working fine