Lead screw for DIY lathe ??

[Naboo]

Hi all

Any recommendations please for lead screw assemblies available on the market. Struggling to find anything of high quality, quiet, with a 2mm pitch. Ball screws pop up a lot, but are apparently quite noisy..

Hoping to source a complete unit (screw with base and guides, with possibility to attach a pulley one end and maybe a hand crank at the other)

Cheers

[kostix]

Check out "linear stage" search on ebay:

https://www.ebay.com/sch/i.html?_from=R40&_trksid=p2380057.m570.l1313&_nkw=linear+stage&_sacat=0

There are these 8mm "T8 leadscrews", which you can probably find in 1, 2, 4, 8mm pitch sizes, maybe others too. Usually sold with the mating brass nut.

https://www.ebay.com/sch/i.html?_from=R40&_trksid=p2334524.m570.l1311&_nkw=t8+leadscrew&_sacat=0&LH_TitleDesc=0&_odkw=linear+stage&_osacat=0

[ilovedrums247]

i'm using this for my diy set up https://www.aliexpress.com/item/4000311275866.html?spm=a2g0s.9042311.0.0.27424c4dpchhoc

[Naboo]

Had a good hunt on there, but all seem to be ball screws which will likely transmit too much noise.
The VR T560 uses a brass lead screw and delrin type nuts to achieve a really quiet movement, but seems it's all custom made.

Capture.PNG

Hoping there's something like this out there, but with a base plate so it's all rigid..
And will run the DC motor belt driving the other end

[ilovedrums247]

Also, are you doing an overhead design?

i've added thrust bearings on both sides of the (1mm) lead screw, the 4080 aluminum profile is filled with silicone, and the motor mounted on 15mm rubber standoffs...it's silent and smooth, but also very heavy..so if your doing an VR-style overhead mount it probably wouldn't work.

[Naboo]

yeah, doing an overhead design currently..
was basing most my design off the VR, but his setup inside that tube is crazy clever so trying to go simpler with a normal lead screw assembly, control start position by a hand crank, and control lead out groove by the motor controls.

I have an open-builds brand one similar to that aliexpress link, but am unsure of the lead and find the carriage to be quite noisy

[soeffingodly]

Here are some pics of the overhead from the T560 I had stashed on my computer.

T560 PICS.zip

[Naboo]

Here are some pics of the overhead from the T560 I had stashed on my computer.

T560 PICS.zip

I'd come across these pics on another tread, great stuff sharing those, thanks
Thanks to that thread I have a Faulhaber motor on the way the same as T-560

Whoever machined that setup is very bloody clever !
From what I understand the steel rod goes through the lead screw and attaches to the motor,
Then the carriage is attached to the lead screw.. The motor turns the rod freely until the end collar is nipped up tightening them together ?
Struggling to understand though how you can hand crank it while the motor is running to do the lead out groove ?

Any chance you know the pitch of the screw please ?

[Dogtemple]

Here are some pics of the overhead from the T560 I had stashed on my computer.

T560 PICS.zip

I'd come across these pics on another tread, great stuff sharing those, thanks
Thanks to that thread I have a Faulhaber motor on the way the same as T-560

Whoever machined that setup is very bloody clever !
From what I understand the steel rod goes through the lead screw and attaches to the motor,
Then the carriage is attached to the lead screw.. The motor turns the rod freely until the end collar is nipped up tightening them together ?
Struggling to understand though how you can hand crank it while the motor is running to do the lead out groove ?

Any chance you know the pitch of the screw please ?

those pics are great, I was looking in to how to build an overhead but managed to buy a lathe with most parts except the head. although I will be making an overhead in the future and those photos are helpful.

the way the hand crank works is with a spragg bearing, its a one way bearing like a freewheel on a bike. you can see it in the last couple of pics in that set, its the small bearing pushed in to the brass coupling.

I need to make some bits for my lathe's overhead as its missing a motor to drive it and I will be making two pulleys and incorporating spragg bearings for this very purpose.

[Naboo]

ah, nice ! thanks mate
makes perfect sense.. looked into magnetic clutches a while ago but seemed like overkill.. will look into sprag bearings instead

[Dogtemple]

no worries, on the pitch thing, if it helps, its 1mm pitch on the leadscrew on my lathe. I also bought a 1mm pitch leadscrew when I was planning to build mine. a fine leadscrew is needed from what I could figure out and saw in photos of existing lathes, although the pitch of the 560 screw appears to be really coarse.

[Naboo]

sweet, yeah figured it had to be super fine

been hunting for a 2mm pitch one thinking that might be what the T-560 uses
trying to go with the same pitch as that, as I have the same DC motor on the way

[Dogtemple]

you would probably need to get a proper measurement on it but he's clearly cut that from a bit of brass tube to his own spec. curious to know what the thinking was behind it as there must be a purpose to it being that coarse.

[Naboo]

yeah, seems the easiest way to get hollow brass, rather than boring a solid rod.. hard to find brass tube with a super thick wall though I'd imagine...


How do you plan to use the sprag bearing in your setup ?
Having a think about it and it would allow the hand wheel to slip, then operate the opposite way to the motor..
So would be good for rewinding the head and maybe positioning the start point.. but not for doing the lead out groove ??

[Dogtemple]

so for mine, I am using two motors for the lead screw. one for the normal speed and one for the faster speeds needed for the lead in and out and the track dividing spaces.

my overhead runs off a small belt to a motor. the motor for mine is missing so I need replace it and the respective fixtures.

for each motor I will make a pulley and press a sprag bearing in to each, the two motors will be linked by a belt and the motors to the lead screw mechanism will be linked with another belt.

when the normal speed is running the faster motor pulley will just sit idle due to the sprag bearing and when the fast motor is needed it will kick in and the slower motors pulley will sit idle.

as you say, it wouldn't allow it to reverse. I don't need that necessarily as mine has a lever that disengages the lead screw and you just shift the carriage back in place. but should I want to do it off the motor, it would just be a matter of fitting another pulley to the faster motor but flip the bearing round the other way. I may do this although I don't think it would be much benefit; it will be another thing to fabricate, it would take longer for the carriage to travel back than doing by hand and cause more wear to the transport parts.

[Naboo]

I see, keen to see pics as this comes together if you want to post any here

Think I may be able to source a lead screw assembly with that quick release function, for returning the carriage back to the beginning..
So for the lead out, I was thinking have the motor controller circuit made so that the speed is adjustable for manual pitch control..
Then for the lead out groove, incorporate basically the same function as a stick blender's turbo button (which will also be settable).. to pretty much turbo the motor along then quickly flick it off to get the locked groove
Sounds good in theory so far

[Naboo]

managed to find something that looks like it'll do the trick..

https://nz.rs-online.com/web/p/positioning-tables/4886016/

Hardened aluminium screw, with self lubricating composite nut.. seems like it'll be nice and quiet.. and it has the quick release function
So could run this with the motor driving it via belt, then have a hand wheel on the outside of the lead screw's pulley, just for more fine start position tweaks

[Naboo]

Just wandering now whether a belt drive setup would actually add noise rather than reduce it..?
Needing torque I'd guess a toothed belt is best, but the teeth may create a chatter

[Dogtemple]

I wouldn't worry too much about torque, a pulley has a lot of grip (when under tension at least). a belt ought to be enough.

there seems to be a lot of prefab linear stages about, are you specifically wanting a nylon one? I bought a stainless screw with brass nut and it feels smooth. its just one off eBay, I was going to run two rails either side with bearings on the rails for the carriage.

I like your idea with the motor, thats essentially what I will be doing, I will be using two dc gear box motors, one about 15rpm the other around 400rpm and slowing them down to suit the correct speed. I still need to figure exactly what rpm I need but going higher and slowing down I think is the way to get it exact enough and maintain adjustment, whilst keeping it simple.

I ought to start a thread for it yeah, I will post photos, I've done a fair amount so far, bought it about a month ago and half the bits are missing and what was there didn't work or not correctly set up. so theres a fair bit more to do

[Naboo]

Ah yeah, like a smooth pulley will do, rather than a toothed belt ?

Turns out the positioning table in that link doesn't offer the quick release, so may still have to do the sprag bearing and hand wheel to rewind it instead...

Yeah plastic nut seems to be the quietest option

The motor I have on the way is 1100 rpm, reduced to 30 rpm by a planetary gearbox. Think that way gives lots of torque and minimal strain on the motor