[mrbaggins]

So I'm making my own CNC, but am struggling with finding lead screws. Google got me to the Cnc and cupcake world guy on eBay, which seems to be nearly the only option without paying out the nose.

Anyone got any more info or useful places to check?

[mikejohn37]

I got my mechanical Kit from a nice helpful Ben at:

All | 3DTek Contact him and see if he can help you.

Electronics kit from Bob, another nice helpful person, at:

Hobby CNC Australia

Mike, Ipswich, Qld.

[mrbaggins]

I'll send 3Dtek an email, they only have up to 500mm on the site as is though. I've emailed a couple more industrial places and hope to hear back this week. Looks like nuts are ridiculously expensive at 50-80 each though.

hobbycnc seems to be a defunct site too, last updated early 2014, and pretty much all of his stuff listed "no longer available"

Thanks for links though, the hobby site has good info, and 3Dtek has good stuff for other cnc type things, I'd stumbled on that with 3d printing as well before.

[sajurcaju]

McMaster-Carr has a good selection and prices.
McMaster-Carr

My router uses the 1/2-10 5:1 screws. I made nuts out of Delrin (~acetal). Here's a long thread, but it is pretty easy:
Making Acetal leadscrew nuts the easy way
Easy, but I'd count on a couple of practice rounds.

Steve

[InMesh]

I looked at buying a CNC and it would be 30 grand ,it was then i decided that the build would not be cheap so i bought all my screws bearings and mounts from CNC cupcake world ,there was no one to mach on price except in china eBay ,i have a really nice machine that I did spend a lot of money on an it was one of the best decisions I have made in ages .That is coming from the I always want it as cheap as I can get it guy in the world. At first I thought they were expensive then I engraved a letter 1 meter high and another 1mm high with accuracy .

[RCaffin]

Looks like nuts are ridiculously expensive at 50-80 each though.

That's not expensive for a good backlash-free ball nut.
Maybe you need to define your real needs and then be prepared to pay for them?

Cheers
Roger

[outtastep]

i have some leadscrew dont know if acme, i believe they were sourced in UK,
if i could find a matching one for my Y-axis 1200mm, i could redesign my machine to have 2 motor on Y, which may be helpful
the screws are 10mm, i count 13 treads in 1inch ? from photo
ps the guy who made my machine made his own nuts from plastic and they seem to work okay

[RCaffin]

I have never heard of a 13 tpi screw. The UK went metric a long time ago. Perhaps you could remeasure in metric?

cheers
Roger

[mikejohn37]

It is probably a high tensile ½” UNC 13 tpi threaded rod. Patrick Hood Daniel uses it in his machine plans. I built his machine but have since upgraded. I blogged it here:

Mike's CNC Routing Adventures: The Decision to Build the Combo#1 CNC Routing Machine from buildyourcnc.com designed by Patrick Hood Daniel

I have some links on the page above to his site, book etc.

You have a basic leadscrew and I do not think it is the ACME screw. If you google ACME leadscrews you will find they are lot more efficient. I am new at this myself and somebody could explain it better.

Mike

[outtastep]

thanks roger - approx 1 thread every 2mm?, 5 per 10mm i guess

[outtastep]

thanks mike its definitely 10mm (or maybe 3/8 )external diameter , will check out link cheers

[outtastep]

found this -
https://en.wikipedia.org/wiki/Trapezoidal_thread_forms
says acme 29 degrees and metric trapezoidal 30 degrees-
i think mine was spot on 10mm and approx 2mm per thread so
TR10x2 ?

hopefully my one is a proper 'lead screw' and not 'threaded rod'

threaded rod seems to have sharp triangular threads

p.s. search of ebay finds this-
X3PCS 1250mm TR10X2D Trapezoidal Leadscrew Spindle CNC XYZ Axis 3D Printer | eBay

cheers
ben

[sajurcaju]

I found making lead screw nuts to be pretty easy. Here is a good explanation:
Making Acetal leadscrew nuts the easy way
This is a long thread to read through, but the details are all in the first few pages.

What I do based on the above thread and making about six of these:
Cut off a 6" piece of lead screw. Bevel both ends on a grinder, making sure to clean up the threads. You have less cleanup if you align the rod to the grinding wheel tangentially, so that the grind marks align with the rod axis. On one end, mill, cut or file off half the diameter so you have a D cross section (maybe 1/2" long).
I used 1 1/4" acetal (delrin) plastic to end up with 1" OD diameter nuts (for a 1/2" rod). Drill a hole down the center the same size as the minor diameter of your lead screw. Split the plastic so you have two half-cylinders (plus the half cylinder bore).
Preheat the 6" piece. Last time I used 350F and it worked fine. Most convenient will be insulated gloves to handle the rod, you could use vise grips.
What you need to do is clamp the hot rod between the two halves of plastic in a vise. This is tricky, you probably want to practice with it cold. You will want rod sticking out both ends of the plastic at least 1". The plastic pieces tend to rotate so they have no gap on one side and a large gap on the other, have a blade screwdriver handy to make the gaps about equal.
Back to the preheated rod--clamp the plastic around it. You can apply some pressure, but the rod is not going to melt into the plastic much yet. Don't break your plastic.
Also don't turn your back on it--the plastic is slowly melting, taking the pressure off the vise jaws. If you don't mind the vise handle, pretty soon your work will fall on the floor.
Keep moderate pressure on the assembly, work on the gaps being similar, and heat each end of the rod with a torch. Be careful to not set your plastic on fire. Patience is key here, the melting happens somewhat slowly. I heat each side for a count of 20 and wait a bit, minding the vise. Do a second round of heat, same count. That will probably be enough.
You will probably not get both gaps filled with melt, at least I don't. Keep it clamped in the vise until cold (mind the pressure for 5-10 minutes after the last heat).

You now have something that is a bit of a mess. A little plastic probably came out both ends and the halves are a little misaligned and maybe elliptical. Clean it up on a lathe (this is why you need 1 1/4" rod to make a 1" nut). I just put the whole thing, rod and nut, in a 1/2" collet. This way I can reverse it and still have it concentric. You could do it in a 3 jaw chuck, with maybe a little misalignment of the thread and OD.

I don't use anything as a mold release. I clean up the ends, leaving the OD rough, then put the rod in a vise and unscrew the nut with vise grips. Put it back on the rod, chuck it in the lathe and clean up the OD to your required diameter.

Now you need to adjust the fit, you probably still need pliers to move the nut on the screw. This is where the half cylinder end of the rod comes in. Clean up any flash on the nut ends. Run the nut back and forth across this end a few times, adding some silicone lube. Reverse the nut and run it back and forth a few more times. You should be able to move it by hand at this point with a bit of effort. Do this some more while you have a beer. You don't want it to move freely, some friction is a good thing.

My nuts don't look nearly as nice as the ones in the above thread, but they work fine.
I recommend making a nut or two as practice, then do the ones for your machine. The main issue is learning how to not overheat the plastic.

You need some way to clamp the nuts in your machine, with the OD of the nut in a tight fitting hole. First time around I used a screw in from the side to hold the nut in place--this wasn't good enough for my router, it worked loose. Now I still use the screw from the side (like a set screw on a shaft), plus end plates to keep the nut from crawling out of the hole.

If this is clear as mud, I can make a couple of pictures. It's really not as hard as it sounds.

Steve

[RCaffin]

Looking at the thread profile, I would say it is a rolled ACME (ie not cut).
Yeah, a hard 10 mm OD does not sound imperial to me.

Cheers
Roger

[outtastep]

thanks roger, so acme can be metric or imperial?
thanks steve for explanation of making nuts

[A_Camera]

i have some leadscrew dont know if acme, i believe they were sourced in UK,
if i could find a matching one for my Y-axis 1200mm, i could redesign my machine to have 2 motor on Y, which may be helpful
the screws are 10mm, i count 13 treads in 1inch ? from photo
ps the guy who made my machine made his own nuts from plastic and they seem to work okay

If that rod is 10mm in diameter then it can have 1.25mm, 1.5mm or 2mm pitch per turn. Measure in metric all the way, especially if you are using a metric caliper. It is really easy, count 10 threads and measure that. In your picture it is not possible to exactly say that you have 13 threads or 12 plus little more. If the rod is a 10mm trapetzoidal, which it actually looks like it is, than it is most probably a 2mm pitch rod, and that would give you 12 plus a bit more threads per inch, but not 13.

[A_Camera]

So I'm making my own CNC, but am struggling with finding lead screws. Google got me to the Cnc and cupcake world guy on eBay, which seems to be nearly the only option without paying out the nose.

Anyone got any more info or useful places to check?

I have just recently bought this kit and started my CNC upgrade. I can tell you, the ball screw/ballnut solution is a HUGE improvement compared to my self made delrin nut on 12mm threaded rods. While the delrin nut works very well also, I am pretty sure that the end result will be much better using this kit. You can get this kit in other dimensions also, and if you only want the lead screws and the ball nuts they are not hard to find on eBay. A quick eBay search gives many hits.

[FastFarmer]

I don't know what your screw is off (i didn't read back that far..) but if it's 13 turns per inch then thats 25.4/13 =1.95 (close enough) which sounds like a 2mm pitch to me. Pretty dam common on small lathe crossbreads...

In relation to ballscrews,.. There are different grades of ballscrew and despite all the BS I read on these type of forums about backlash, your real enemy to accuracy is deviation over the screw. On eBay you will get C7 screws and they have unto a 0.05mm deviation over 300mm travel. Totally useless in any decent machine shop. Most Chinese CNC machines will run C5 ballscrew. Personally I only use C3, but it depends on your application and budget.

https://tech.thk.com/en/products/pdf/en_a15_011.pdf

Cheers