Metric thread sizes

I need to replace a piece of threaded rod on an Italian bandsaw probably mid 20th century. The rod measures 12.46mm diameter and when I put a metric thread gauge on it it comes out somewhere between 2 and 2.5. If I put a whitworth 55 gauge on it the 12G fits.

i know nothing about thread sizes and have no idea where to start. The piece of threaded rod is used as an adjustement point for the motor.

That is a half inch 12tpi Whitworth thread. Google Whitworth threads for a table of all sizes. You can find 1/2" W studding on your favourite auction site - and probably others as well.

Edited By Bizibilder on 30/01/2021 16:09:09

Is it possible that a large Italian engineering company used Whitworth threads on their machines?

Possibly, but more likely that part has been replaced previously? Or it’s not actually an Italian machine?🙂

Definitely an Italian machine, still in Italy too. I feel it is unlikely to have been replaced here in Italy, finding 1/2" would be impossible unless you were a big manufacturer.

I have been trying to find some high tensile 1/2 threaded bar in the UK and I haven't found any yet. It has rather a large 3 phase motor hanging off it and has bent. I don't think mild steel would last long.

Quite possible - mid 20th century would have been just after WW2, and with material in short supply there would have been a lot of US and UK war surplus available.

Andrew

I'm guessing at the mid century.

Not likely, but not impossible either. Possibly the band-saw was made for export to the UK or made to a British design.

Or it's been repaired in the past by someone who had Whitworth to hand. For adjusting a motor 1/2" Whitworth, M12 and 1/2" UN are all similar.

Dave

If it has bent, it has been subject to bending forces.

Are you of the opinion that high tensile bar will resist bending forces better than low tensile bar?

The clue is is in the name. High tensile bar has a greater tensile strength than low tensile bar.

The ability of any structural member to resist bending forces is a function of its geometry and its Young's modulus.

Try:

https://www.grampianfasteners.com/product/653 (but shown as out of stock)

https://www.tfc.eu.com/product/high-tensile-threaded-rod-grade-en8-bsw/

https://www.ebay.co.uk/itm/BSW-Threaded-Bar-Screwed-Rod-Studding-S-C-Black-12-1-Foot-Long/191971076705 (admittedly, the grade is not shown, but it is hard to buy self-colour in anything but grade 8.8 so ask the seller).

Having seen the photo, which century?

That's a classic Victorian design. They might still be making them!

Dave

I'm not surprised, threaded bar is not high tensile

Did they have 3 phase motors back then?

I'm willing to learn. If a bolt can be high tensile why cant threaded bar?

Unless you buy the HT stuff

If I was unclear I apologise. I am replacing it because it is bent. The weight of the motor hangs on the threads, I imagined the threads on a high tensile bar would better resist being distorted.

Edited By pgrbff on 30/01/2021 17:12:50

I found grampian but being in Italy with an Italian IP address my search results will be different to someone searching with a UK IP address.

"If I was unclear I apologise. I am replacing it because it is bent. The weight of the motor hangs on the threads, I imagined the threads on a high tensile bar would better resist being distorted."

If the motor weight is bending its' mount rod it would be wise to modify the motor suspension so it is not putting bending load on the threaded rod, only tension. If in tension only, normal low carbon steel threaded rod should be fine. If the rod sees bending load, even in high strength steel it may not be strong enough. Again, review the way the motor is suspended if possible.

Just FYI high strength and medium strength threaded rod is available in USA at McMaster.com but only in metric and UN threads. Shipping to UK or Italy may or may not be possible but certainly would be expensive.

Edited By Jeff Dayman on 30/01/2021 17:42:02

This one any good?

https://www.bbpadova.it/viteria-e-bulloneria/barre-filettate/barra-filettata-passo-bsw-14010317/

I wouldn't be surprised if the saw had that thread from new. I had an Italian made Aspera motor in a mower that had Unified threads throughout. It was made under licence from Tecumseh motors, from the USA.

Though the first one appeared in 1890 a 3-phase motor makes it 20th century!

Dave