Metric thread sizes

[pgrbffParticipant @pgrbff]

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.

[pgrbffParticipant @pgrbff]

[BizibilderParticipant @bizibilder]

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

[pgrbffParticipant @pgrbff]

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

[not done it yetParticipant @notdoneityet]

Posted by pgrbff on 30/01/2021 16:24:53:

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?🙂

[pgrbffParticipant @pgrbff]

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.

[Anonymous]

Posted by pgrbff on 30/01/2021 16:24:53:

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

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

[pgrbffParticipant @pgrbff]

I'm guessing at the mid century.

[SillyOldDufferModerator @sillyoldduffer]

Posted by pgrbff on 30/01/2021 16:24:53:

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

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

[DC31kParticipant @dc31k]

Posted by pgrbff on 30/01/2021 16:44:18:

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.

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).

[SillyOldDufferModerator @sillyoldduffer]

Posted by pgrbff on 30/01/2021 16:46:37:

I'm guessing at the mid century.

Having seen the photo, which century?

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

Dave

[Dave HalfordParticipant @davehalford22513]

Posted by pgrbff on 30/01/2021 16:44:18:

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.

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

[pgrbffParticipant @pgrbff]

Posted by SillyOldDuffer on 30/01/2021 17:03:25:

Posted by pgrbff on 30/01/2021 16:46:37:

I'm guessing at the mid century.

Having seen the photo, which century?

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

Dave

Did they have 3 phase motors back then?

[pgrbffParticipant @pgrbff]

Posted by Dave Halford on 30/01/2021 17:04:06:

Posted by pgrbff on 30/01/2021 16:44:18:

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.

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

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

[JasonBModerator @jasonb]

Posted by Dave Halford on 30/01/2021 17:04:06:

Posted by pgrbff on 30/01/2021 16:44:18:

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.

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

Unless you buy the HT stuff

[pgrbffParticipant @pgrbff]

Posted by DC31k on 30/01/2021 16:57:46:

Posted by pgrbff on 30/01/2021 16:44:18:

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.

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).

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

[pgrbffParticipant @pgrbff]

Posted by DC31k on 30/01/2021 16:57:46:

Posted by pgrbff on 30/01/2021 16:44:18:

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.

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).

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.

[Jeff DaymanParticipant @jeffdayman43397]

"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

[DC31kParticipant @dc31k]

Posted by pgrbff on 30/01/2021 17:15:00:

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

This one any good?

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

[old martParticipant @oldmart]

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.

[SillyOldDufferModerator @sillyoldduffer]

Posted by pgrbff on 30/01/2021 17:06:34:

Posted by SillyOldDuffer on 30/01/2021 17:03:25:

Posted by pgrbff on 30/01/2021 16:46:37:

I'm guessing at the mid century.

…

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

Dave

Did they have 3 phase motors back then?

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

Dave

[pgrbffParticipant @pgrbff]

Posted by Jeff Dayman on 30/01/2021 17:40:04:

"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

I think it was the guy selling me the saw manhandling it into the back of his van that bent it, not the weight of the motor.

[pgrbffParticipant @pgrbff]

Posted by DC31k on 30/01/2021 18:34:04:

Posted by pgrbff on 30/01/2021 17:15:00:

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

This one any good?

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

Thanks. I don't wish to appear ungrateful but unfortunately many if not most websites in Italy list lots of items they don't stock with "request info". Many websites don't even have prices for the material they keep. In 8 years, I came to Italy in 2012/13 I have only had a reply from one, possibly two Italian companies when enquiring about their products through their website. And that includes huge multi national companies. At this point I have all but given up, except now we have Brexit, and buying anything from the UK has become all but impossible. Even tea.

[Jeff DaymanParticipant @jeffdayman43397]

One further thought, if the rod was bent by rough handling and would normally be OK – if thread is not needed all along the rod, could you buy a die and some medium strength unthreaded steel rod and thread the ends appropriately? this may be less cost and effort than finding hard to obtain "special" threaded rod ready made.

[Robert DoddsParticipant @robertdodds43397]

pgrbff,

Do you know how this 1/2" rod got "bent"?
Your machine is unlikely to have more than 5 hp driving it and it is difficult to imagine that a motor of that size causing the damage. It would be more in keeping with an accidental collision with a fork truck or similar handling equipment
Is the rod used as a belt tensioner?
Unless you are constrained by having 1/2" tapped holes in the motor or machine frame consider substituting M12 studding with appropriate nuts for the present rod. At least you should source that in Italy.. As far as strength goes, M12 studding should have the capability to carry at least 2 tonne, more than the motor weight and any belt tensioning that is involved bu obviously , if other outside forces are involved some damage may result.
I googled Antique bandsaws and the images that came up show a great variety of makers and sizes and some with the motor floor mounted rather than on the machine. Would this configuration help with your project?
Hope this gives you some food for thought.

Bob D

[Author]

Posts