# Technical term please?



## GrahamRounce (5 Feb 2018)

Hello.
Can someone help me with the proper name for threaded rod?
I don't mean the cheap studding stuff (useful though that is), but with a standard gear profile on the threading, to accurately mesh with a gear that rotates or moves as the rod is spun. 
Not a worm gear - longer, thinner, and no hole down the middle!

While I'm here, a point to a not too expensive supplier would be great, too...

Thank-you,
Graham


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## Retire2004 (5 Feb 2018)

Hi Graham,
Sounds like you may be referring to a "LEADSCREW" as on a metal turning lathe.
Tudor


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## GrahamRounce (6 Feb 2018)

Aha! Maybe you're right. Not that big though - I'm thinking of about 5mm. 
I'll re-google, thanks.


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## novocaine (6 Feb 2018)

still a leadscrew and try our friends in the far east, they are used on 3d printers and little CNC machines.

https://www.banggood.com/500mm-Lead-Scr ... rehouse=UK


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## DTR (6 Feb 2018)

Leadscrews tend to be an Acme thread, which is available in rod form in various sizes. So maybe try searching for Acme threaded rod?


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## Brandlin (6 Feb 2018)

Leadscrew is the general term.
Acme thread is a specific profile of thread and a subset of leadscrews - as DTR says its the most common profile.

We could probably give more specific advice if we knew what the application was.


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## GrahamRounce (6 Feb 2018)

Thanks. The application's nothing esoteric. The rod wants to be about 10cm x 5mm, threaded at say 1mm, with a spur gear contacting it at one end, and a 1cm long "nut" running up and down as the rod turns.
The gear might take some force, so it needs to mesh properly with the rod, which might entail the spur teeth being angled?
(Pity you can't just go into a suitable shop these days and look at what they've got, and ask questions of the knowledgable assistant! I'm in the East End, where there are many buildings with "ENGINEERING WORKS" etc set in stone above the pizza parlours, kebab shops, and estate agents'. /moan)


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## Brandlin (6 Feb 2018)

Hmm. If you are expecting your 'threaded rod' to mesh with and drive the spur gear - then that IS a worm gear. The tooth profile on a worm gear is different to that on a lead screw.

Your explanation suggests to me that what you need is standard threaded rod onto which your nut will thread. Standard M5 thread pitch is i believe 0.8mm. M6 thread pitch is 1mm. 

You then need to mount a worm gear onto the end of this to drive your spur gear. You should be able to but a worm gear with an through hole to fit on your threaded rod and lock in place with grub screws or solder it on (depending on the load expected.

What kind of torque, speeds and loads are you expecting to be applied?

I don't believe you will find a single common thread type that will satisfy the needs of both the spur and the threaded nut. 

If you already have the spur gear then you need to know the modulus of the gear so that you buy the correct modulus of worm to mesh.


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## GrahamRounce (6 Feb 2018)

Ok, thanks very much, again.
I wonder what's the longest and thinnest worm gear you can get..


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## Brandlin (6 Feb 2018)

Worm gears aren't long compared to their lengths. Nothing moves along them. They only need to be long enough to mesh with the spur gear.


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## GrahamRounce (7 Feb 2018)

Well, I suppose I could do it myself...
This looks pretty cool (though I'd want a much smaller wheel)
https://m.youtube.com/watch?v=XIzlg_uObwQ
...BUT assuming the diameter of the wheel is such that the tooth spacing of the tap divides exactly into the circumference of the wheel at full depth, it's not going to go exactly at the edge of the wheel when the cutting starts! And vice versa!
Yet the result looks pretty good.
Has anyone tried it?


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## novocaine (7 Feb 2018)

I have the feeling that what you are trying to achieve is a linear actuator. 
turn your motor through 90 and do away with the worm drive, instead use a pair of cogs. 


I have hobbed a wheel like that before, it really isn't a good idea without the right tools, 1 slip and you're ruined. if you want to do it, have lots and lots of spares, I'd don't think you'll do it at 5mm to be honest, I think you'll snap a fair few taps. also don't expect it to withstand much load once done, the deflection on a 5mm shaft will be pretty bad.


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## GrahamRounce (7 Feb 2018)

Yes, I'm sure you're right (now that I've tried it! A kludged mock-up, but enough to see it wasn't going to work..)
If I had half the equipment some of the guys on youtube have, I'd be a happy bunny. Probably never see daylight again 
Thanks all.


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