My little DIY benchtop mini lathe

G'day all!
Thought i would post my little lathe project I've been putting together.
I'm purely a hobbyist so this project is something to do in my spare time
I built myself a cnc router bout a year ago and use it very regularly for all sorts of from stencils, engraving, 3d relief to 6061 aluminum rc car parts etc...
But there are times when i wish i had a small lathe which would be quicker and easier for certain parts than the cnc.
So being a cheap ass and chronic tinkerer, i set about making my own.

I'm about halfway thru so far. I started with a 4th axis unit i bought off ebay which i used initally as a 4th axis on the cnc and removed the stepper.
I came across an old electric scooter at the recycler, it had a 200w 24v motor in it so decided it will do for a start, at $5 cant go wrong.
I made up a ~36v linear supply to power it thru my homemade pwm controller.
All the ally in this project is recycled from a local boat builders scraps bin so kept costs low and selection of thickness of plate was great, 6,7,8,10,12,15,25mm plate of various sizes and its all 6061 marine grade
I haven't really followed any plan either, its all been sort of on the fly design inspired by other designs on google and my own ideas with my available materials.

I went with the square cross slide as opposed to a dovetail because i don't have a dovetail cutter, maybe later on if the lathe performs the way i want.
i plan on having some sort of cover over the slide to stop any chips getting in and some felt wipers on the rails.
The rails are polished hardened steel 8mm rods from old printers and the blocks running on them are made from 25mm thick hdpe, the fit is quite firm with no movement what so ever. I may end up getting some bronze bushings at a later stage and making the blocks from aluminum, but the hdpe will do fine for now.
the tailstock is made from an old drill chuck and shaft threaded to take the m12 nut and will also ride on rails with hdpe blocks. i am still to come up with a method to lock the chuck in place for boring holes, thinking of a pin thru the shaft somehow.
the leadscrews are just 1/4" brass all thread polished up to get rid of any rough spots on it and lead nuts are hdpe again (just because i have it)
Oh and the headstock will get raised up to suit the toolpost and tailstock height, 25mm i think will do if i worked it out correctly :p

I have also entertained the thought of making it cnc as well as i already have steppers, couplers and driver board. But i think ill see how it goes manually first :)

Anyway ill let the photos do the rest of the talking
Any questions or suggestions, feel free!

hi,

sorry no one commendted on this

but i think this is very neat way or making a lathe ..

i have a similar story ... started with a 3 axis cnc router ... but now looking at adding a 4th axis and making a simple but effective table top lathe ..

pls keep the pictures and videos coming ..

thats some fine work

chX

Great job! There's nothing better than using stuff you have on hand to create a useful machine...very satisfying! You going with Mach3 or LinuxCNC?

You may need to redesign your z-axis ways though at some point though. Those small, unsupported rods will most likely allow too much flex & vibration when the cutting forces are applied. Hopefully I'm wrong though.:)

You should be able to find some inexpensive supported rods with linear bearings for a reasonable price that'll be far more rigid. Here's one example a quick look-see turned up on ebay so you can see what I'm referring to. Free Shipping for Linear Rail Support SBR12 500mm Shaft Supported for CNC | eBay

Keep posting pics as it progresses; CNC lathes are so cool!

thanks for the comments!
I may end up shortening the rails as they are much longer than needed ( they go past the headstock a fair way and is not needed)
hopefully the 8mm rails should do, i dont plan on doing any heavy cuts but will see how it goes.
i just so happened to have about a dozen of these 8mm hardened rods from a large laser printer i dismantled :)

im using mach3 as thats what i use on my cnc router plus i know nothing about linux.

progress is coming along nicely, ive been drawing up the tailstock supports and rails as im looking to make the rod supports all one piece with the z rod supports (it is the z axis right? i thought it was the x :p )
any way, more pics to come later
stay tuned!0

Yup, the Z-axis is lefty-righty and X is inny-outty as viewed from the standard lathe operating position. One must learn all the highly technical jargon before operating CNC lathes!;)

Alrighty progress has been a little slow with work and family commitments but managed to get out to the shed today and make a few more parts.
Pretty well finished the X slide, just need to make up new handles for the leadscrews.
Z is also complete for the most part.
I am very close to actually cutting stuff, will start off with something soft like wood or plastic and depending on how well it behaves, move up to aluminum and maybe steel...
I did raise the headstock with a 6mm plate, might be enough, time will tell. I can always swap the 6mm plate for 8, 10 or 12mm depending on how much more height it needs.
Anyway i'll let the pictures do the rest of the talking, any questions or comments feel free :-)

Wow, looks great! Betcha you're tired of drillin' & tappin'!:eek:

What kind of electronics goodies do you have planned for it?

oh yes the tapping... i may have gone a little overboard with the 12 m5 screws holding the tool post together but nothing wrong with over doing it! :p
Drilling was easy as i did all that with the cnc router but tapping was all by hand... wish i had a tapping head for me drill press :)

Electronics will eventually be my old tb6560 3 axis board driving couple of nema17 steppers. I have some nema 23 size steppers too but i think the smaller ones will do fine.
I will be running it manually for a while just to make sure it will hold up mechanically before going to cnc.
The spindle motor is a 24v 200w electric scooter motor, ive built a pwm speed controller for it and 36v linear psu tor run it. The motor will handle the 36v no problems, already ran it for quite a while varying loads and it barely got warm.

Whee! it cuts!
Finished off the crank handles and fitted them up.
I dont have any tooling as yet, waiting on some from ebay. so in the meantime I ground a couple of old allen keys as temporary test tooling.
first try was a piece of 25mm pine dowel, worked a treat! surface finish not the greatest probably the dodgy tool or the pine dowel itself.
Even parted it off with a allen key parting tool :)
Next try was a piece of 10mm aluminum bar which actually cut surprisingly well!
I dug out an old hss 8.5mm drill bit and proceeded to cut, grind and shape it to resemble a standard cutting tool and tried that out, not too shabby.
seems to handle light cuts pretty well (like less than 0.5mm) any deeper and it starts to chatter and the guide rods begin to bow a smidge (you were right Dickeybird, the rods are too small :p lucky i have some thicker rods which should help)

Should have better success once i get proper tooling, looking at getting this set - 11PCE 8mm 5 16 034 Mini Metal Lathe Carbide TIP Tool SET Free Postage | eBay

First test cuts video, never mind the "dunka dunka" noise in the middle of the cut, theres a chunk missing out of that ally bar :)

http://youtu.be/gNfeqjju8pI

Great job, I'll bet you're happy as a camel on hump DAY!:wee: Nice work on the home-ground tooling. Most folks won't even try that!

Take your time with v1.1 & see if you can come up with a way to support your larger rods. The flexing due to the lack of support is what's causing the heebie-jeebies, not the size of the rods.

Thanks Dickeybird!
Oh yes i reckon happier than a camel on hump day!
That feeling when i fired it up and fed that tool into the stock and saw swarf curling off so nicely was awesome, i played around for about an hour just trying different materials and cut depths.
Brass was actually quite nice and so was aluminum.
I googled around for a while and found a few sites that outlined the basics of lathe tool grinding so that gave me a good direction when grinding up my own tools, not the greatest but god enough to play.
It performed better than expected given the dodgy ground tooling. :cheers:
I am looking at replacing the rods for supported rails, its deciding which type now..
I have looked at the sbr rails which i currently run on my cnc router but i dont like how much vertical height they take up.
I did however find some hiwin "style" rails on aliexpress for a reasonable price.
This is them here - NEW:Square linear guide 2 X MGN12 L=300mm with 4pcs MGN12C linear blocks(can be cut any length)-in Linear Guides from Industry & Business on Aliexpress.com
Will 12mm rails do the job?
Given the size of my machine i suspect they should be fine, i mainly want to use it for turning special bushes, spacers and that kind of thing from aluminum and maybe brass.
Steel would just be an added bonus but i know at the moment with unsupported rails that probably wont be possible without very shallow cuts or nasty chatter.

anyone?
hmm all quiet.
anyhoo, I've been starting to look at how to make it cnc.
I have a decent selection of stepper motors on hand in the nema17 and 23 size, nema17 should be fine i think, at least for the x axis.
May go with a bigger nema23 for Z seeeing as it has to move the x around as well.
I'm still tossing up whether to mount the steppers offset and drive the screws with mxl belts or mount them inline with the screws and use flexible couplings.
What are peoples thoughts?
Inline and direct drive is cheaper and easier but offset and mxl timing belts and pulleys will give more torque... something like 18 tooth to 30 tooth or around that..
Opinions?
Heres a couple of pics of a mockup if i were to mount the steppers offset and use timing belts
First pic is how it sits now

That looks like a great price for those rails if the quality is OK and the 12mm size should be fine. I'm tempted to pull the trigger on some of those myself as I've been gathering parts for a 3rd (milling drilling) axis for my lathe and my old router could use some of those too. Thanks for the link!

Your timing belt mockup looks good and should work very well. Your 1/4"-(I assume)20 pitch screws won't need much, if any reduction though if you use 23 size motors with average muscle.

Yeah a friend of mine got me onto aliexpress, he's used them a lot and has had good dealings with the sellers and good postage speeds.
I am now in a pickle as to which type of rails i want. There is the mgn12 12mm rails with carriages in a C and H type (H being the heavier duty carriages to the C) and then theres the mgn15 15mm rails with C and H type carriages too.
What I'm unsure of is how much force would be exerted on the rails and which rails will do the job...
Here's the specs on the rails I'm looking at.
Attachment 246004

Haven't done much else with the lathe at this point, been playing around with the cnc router since i got my shipment of endmills from drillman :)

I looked at your chart but I'm afraid my engineering skills are strictly "seat-of-the-pants" and my eyes glaze over looking at rows of numbers.

Bigger is usually better when dealing with machine rigidity so if the price isn't out of your budget, I'd go with the bigger, heavier choice if you have the room.

I think either choice will be many many times stiffer than your unsupported rod, I would say pick the larger for ease of installation, I hate working with tiny bolts,
Though it appears 12 or 15mm rails of that brand both mount with m3 screws. Either would work just fine I think.

They are all too small for lathes working in metal.
Suitable size start at 20-25mm and up.