[doorknob]

Thanks, Simon, that was very helpful.

I'm going through the decision process of whether to attempt my own mini lathe conversion or get a kit.

It looks like you have chosen ballnuts without a flange. Was that done because of limited clearance, especially under the cross slide?

I'm not sure that I understand the ballnut-to-slide attachment method - are those two tapped screw holes in the top of the ballnut that you either attach directly to the cross slide, or perhaps to an adapter plate that you attach beneath the cross slide? If so, the datasheet does not appear to call out the thread (but maybe I have missed it somewhere).

[Simon C]

Doorknob, Yes i chose flangeless nuts cos of the limited space particulary under the crosslide. the 8mm nut that i used under the crosslide fits nicely without haveing to make the slot in the saddle bigger and potentialy weakening it. thease nuts are mounted useing a thread on one end of the nut, the 2 taped holes you are refering to, are to hold the recuirculation tube in place to bring the balls in the nut back to the front, after they have gone round the threads on the spindle. the thread for mounting on the 8mm nut is M15x1 and the 12mm nut has a M20x1 thread for mounting. as for wether to do your own conversion or buy a comercial conversion kit, if you buy a kit you will save yourself alot of time and headaches, but if you convert one yourself useing your own design or similar to mine i think you will have a much more accurate rugged and longlasting machine in the end, all the commercial conversion kits i seen are full of compromises and "corner cutting" in the design and materiuls used. another option is to just buy an old cnc lathe like a Denford Orac or a Boxford 160TCL or an Emco compact 5, then just replace the outdated electronics with new drivers and stepper motors and away you go, most of thease type of old lathes come from schools/collages/universities and have had only light use, so mechanicaly they are in very good condition,

pic below you can see the thread for mounting, its the end that has a smaller diameter.


almost forgot, the way i mounted the nut under the crosslide is by useing the 2 holes that are already in the top of the crosslide that fix the original nut to the slide, i just machined a piece of aluminium about 20mm x 20mm x 30mm and just drilled and tapped 2 holes in one side to mach the 2 holes on the crosslide and then put it in the lathe and screwcut a M15x1 thread in the end of it for the nut to screw into. you can see a pic of it in the third post of this thread, its the pic on the far right,

regards
Simon

[doorknob]

OK, that clarifies things, thanks...

[Simon C]

Few pics of the Z axis stepper mounting and the steel cover for the X axis motor and ballscrew, il make a rubber "wiper" that will stop coolant and swarf getting under the cover as the crosslide moves back and forth, il mabe make it out of a rubber innertube from a bike tire, or hack up a pair of old wellington boots Next job is to turn the ends of the Z ballscrew to match the supports.

[bluelans]

Hello , everyone .

[RotarySMP]

Really nice conversion. Thanks for posting the order numbers of that 8mm ballscrew you used on X. I converted my 7x12 years ago, and was planning to use a little 3/8" ballscrew for X, but I would have had to really hog out the saddle to make it fit, and there is not that much meat anyway.

Have you mic'd your bed thickness? On mine there was quite a bit of variation, so I had to file and scrape the under side.

That Sieg gib strip system on the saddle is crap. I tossed the setscrew adjuster and just shimmed the gibs. Tapered gibs would be better.

The tailstocks are generally horrible on these lathes. I hope you got a better one than I did.

What sort of things are you planning to use it for? Since it is my only lathe, I tend to abuse with turning jobs near it's limit. Glad I did a cross slide travel increase mod.

What tool post are you planning to use? I have a Phase II AXA sitting on a steel riser block. This works really well (but probably needs the X travel increase).

I put a sheet metal cover over the Z ball. Some sort of expanding cover would be even better.

How do you plan to do the home/limit switches?

[doorknob]

What sort of things are you planning to use it for? Since it is my only lathe, I tend to abuse with turning jobs near it's limit. Glad I did a cross slide travel increase mod.

Is that cross slide travel increase mod documented somewhere?

Edit:

I ran across your post at http://www.cnczone.com/forums/830447-post8.html which contains some such links, however those links are not functioning (and your web site does not appear to be up and running at present).

[RotarySMP]

I need to find a new host, and haven't got around to it in the last few weeks.

Attached are the bits from my website.

Thelink is to John Morans write up.
MiniLathe, Cross Slide Travel Increase, Ball Bearing

[RotarySMP]

I guess you can't post HTML files here.

[Simon C]

Mark, thanks for your post,

The underside of my bed is very uneven aswell, theres about a 0.1mm diffrence over the whole length makeing proper gib adjustment impossible. i have never done any scrapeing so i dont realy know how to do it. I have the lathe bed bolted to my mill at the moment so i can use a fly cutter to true up the underside. while its on the mill i will fly cut the areas of the bed were the bearing supports will bolt to, and drill/tap for the mounting bolts.

I ditched the set screw set up aswell and made new gibs out of 20mm x 10mm steel bar, il use shims like you did for the adjustment.

As for the tailstock i got lucky. it has cam lock and looks quite meaty compaired to some i seen.

I only be useing it for fairly small diamiter parts but as i had to make a new hub at the front to hold the AC bearing i decided to make it 15mm longer than the original hub. How much longer than the original one did you make yours?

I been looking at those type of toolposts but the place im going to buy it from only say that the main block is 2 1/2" x 2 1/2" x 2 1/4" high. Is that the same size as yours?

Would like to use an axpanding type screw cover but havent been able to find any on the net.

Still not sure how or were to mount the X home. i want it to be under the metal cover at the back, but its trickey cos as far as i know a lathe has to home in the fully out position? would make it much easier if i could home with the slide fully in.

[RotarySMP]

Hi Simon,

Lucky you have a mill big enough. I had never done any scraping before either. It is easy enough, because everything happens in slow motion. Using a old file end and muscle power, it is more a patient training than anything.

That tailstock is a completely different design to the POS my lathe has, looks much beefier.

Yes the AXA QXTP's are about the dimension you gave. Since the top slide is redundant on a CNC lathe, you need a riser block to mount an AXA to the cross slide (a couple of photos added).

Travel increase stand off is about 50mm long, so the travel increase would have been about 25mm with a standard cross slide, but it got replaced with a T-slot cross slide which is a little longer, so the net travel increase is probably like yours. Heres an old pic with the old sheet metal X axis pulley mount, but you can see the cross slide. I recently scraped the slide as it was bowed like a banana.

The last photo shows the lathe at it's limits doing silly things. I was turning up a plug for an A5 crucible mould. That block of wood started at is about 6 1/2" across the edges. I'm using a wood router bit in the Proxxon grinder to knock it down the end square.

[RotarySMP]

The numbers on the cross slide are tenths (.0001") deviation from the upper right corner. I didn#t bother taking it down to the level of that dip on the RH (backside of lathe) end, as it never gets used.

[doorknob]

From where did you source the T-slot cross slide?

Is that a part that is available from the manufacturer, or is it an aftermarket part, or was it custom-made?

[RotarySMP]

I made it out of strip steel. The ledges of the t-slot were milled on the 7x lathe. The dove tail angle strips were filed by hand.

It was epoxied and screwed, then the edges milled, and finally (after a couple of year use) I got around to scraping the table and sliding ways flat.

[Simon C]

That crosslide mod looks alot better than the original, perfect for a rear mounted parting tool. I like the enclosure you made to, im hopeing to make something similar.

Is that an ER32 collet chuck you are useing or 5C? think il have to get one of those aswell.

I decided to order the QCTP, they call it "Model 100" about halfway down the page in this link Arc Euro Trade - Tool Posts

[RotarySMP]

Model 100 or AXA are the same size. That one is a piston type. The Wedge type supposed to be better. Don't know if it makes much difference on such a little machine. My Phase II wedge type repeats very well.

Shars in the states have really cheap extra tool holders. They cost about $12 each. I think I have nearly 20.

I use ER 32 collets, as they can pass 20mm, same as the spindle. You can't mount 5C collets on these machines (at least not with a draw bar) as theyx need a larger spindle through diameter. I made the collet chuck on the 7x. Used the proxxon as a tool post grinder to grind the taper. Cutting the thread (32x 1.5) is really borderline for these little machines.

An enclosure is one of the best things about CNC.

[doorknob]

I made it out of strip steel. The ledges of the t-slot were milled on the 7x lathe. The dove tail angle strips were filed by hand.

It was epoxied and screwed, then the edges milled, and finally (after a couple of year use) I got around to scraping the table and sliding ways flat.

Very clever...

Now you have me thinking along similar lines...

[RotarySMP]

It is an old idea. Martin Cleve published it in Model Engineer in 1958. Here are the dimensions I used.

[Simon C]

My first attempst at engraveing on my mill, the two letter "A" in "manual" screwed up a bit cos i didnt cnc the Z axis on my mill (was a temporary conversion) so i had to raise and lower the Z axis for each letter. the materiul is just 1.6mm PCB, this will be the pannel for spindel control, il also make another pannel for cycle start feed hold etc,

[RotarySMP]

Nice.