Metric thread sizes

[Michael GilliganParticipant @michaelgilligan61133]

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

[…]

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.

[…]

.

The two are not unrelated

This is about packaging materials … but worth viewing for the excellent diagram : **LINK**

https://www.researchgate.net/post/What_is_the_relation_between_Tensile_Strength_and_Youngs_Modulus_of_a_material

MichaelG.

[Roger BestParticipant @rogerbest89007]

That's a fabulous bandsaw, it is very reminiscent of early 20th century steam toy accessories and very different to my 60s Italian bandsaw which uses a heavy pressed box construction.

Either way its well worth some TLC and possibly some sensitive technical enhancements.

[duncan webster 1Participant @duncanwebster1]

All steels have much the same Young's modulus, it's all about chemistry, but they don't all have the same proof stress or UTS.

Within the elastic range how much it bends is down to Young's modulus and geometry, but how much it will bend without taking on a permanent deflection is down to Youngs modulus, proof stress and geometry.

The photo looks to be a machine which would originally be driven by line shafting. Has the electric motor been grafted on? A photo of the motor installation would help

[pgrbffParticipant @pgrbff]

Posted by Robert Dodds on 30/01/2021 20:13:32:

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

The rod screws into the cast iron body so it would be easier to stay with 1/2".

The image is of the motor mounting plate folded up, at the top you can see where the 4" rod is threaded into the body of the saw and regulates the position of the motor to tension the belts. The 4 bolts hold the motor on to the plate. The plate also has a crack which will have to be reapaired.

There is no great strain on it, but obviously some vibration which I thought might damage the threads over time if I used poor quality mild steel threaded bar.

[pgrbffParticipant @pgrbff]

Edited By SillyOldDuffer on 31/01/2021 12:53:57

[David George 1Participant @davidgeorge1]

Have you thought of using a set screw and cutting off the head. And Cromwell tools sell 8.8 Din 976-1A 1 meter length for £10.48 .

David

[pgrbffParticipant @pgrbff]

I have found a couple of sources but it still costs £10 for a single 4" set screw when including postage. Then I have to have it posted on to Italy.

I'll keep looking

[Howard LewisParticipant @howardlewis46836]

If it is 1/2 BSW, could you not screw cut (or use a Die) some bar to make a bespoke adjuster? (Presumed to be an adjuster for the belt tension )

Even if you have to turn down some bar to 1/2" diameter. Hexagon bar will even provide the means of fixing the adjuster into place, as well as for making any nuts that may be required.

After all we are supposed to be Engineers who can make things with machines.

Howard

[pgrbffParticipant @pgrbff]

Unfortunately, I no longer have access to a lathe and I am primarily a woodworker. If I could I would, promise.

[Robert DoddsParticipant @robertdodds43397]

pgrbff,

Your motor mount picture clarifies the configuration quite a lot.
Have you still got the 1/2" rod? Seeing the type of motor mount you have I suspect that the bend in the rod is intentional to accommodate the curved movement of the adjusting lug as the motor and plate pivot on the hinge at the bottom.
It may well be a cheap compromise to avoid using an eye bolt and clevis that would, in an ideal world, enable the screwed rod to be held square to the face of the adjusting lug.
In service there is no way that the forces involved with tensioning the vee belts would over stress your 1/2" rod, unless of course, the threads are badly damaged to start with. With that proviso I suggest you do a trial assembly and stop worrying about high tensile rod replacements.

Regards

Bob D

[Howard LewisParticipant @howardlewis46836]

If you could find some 1/2" round bar, you could cut the thread by hand. It will need care, lubrication (for the work and for you ) and some effort, but will mean buying a die and die holder if you do not already have them.

Failing that if you are prepared to depart from absolutely prototype, could you convert to M12 studding and nuts?

Howard

[Tim StevensParticipant @timstevens64731]

Once more, a problem which cannot be addressed properly as the information given is simply not there. Try to put yourself in the position of the person reading your request, and think 'Would I really understand this problem?'

If the rod you need attaches to the hole behind the slot in your second picture, and the plate pivots around the bottom hinge, it seem inevitable that any rod, whatever it was made of, would have to be bent – or no adjustment would be possible.

And I wonder about the use of a 'heavy three phase motor' on a device which looks – well – almost delicate. Especially the single hinge which has to cope with the weight, and the belt tension, and with a plate which is already well out of line…

Not the news you want to hear, perhaps.

Regards, Tim

[Roger BestParticipant @rogerbest89007]

If we are just talking about a tensioning knob between those forks it looks an easy job.

Sorry i can't post anything over as my lathe is out of action.

[Roger BestParticipant @rogerbest89007]

quick positive comment:

I found, when trying to measure some threads on my lathe, that if I took a high resolution photo of the thread with a tape measure lying along it, If I zoomed in on the picture I could measure the features far easier than I could by eye. It seemed to be adequately accurate too.

[Tim StevensParticipant @timstevens64731]

A further thought has occurred to me:

In use, the tension of the belt would pull the motor towards the column. [Unless I have totally misunderstood the photo.]

This means that the 'tensioning' bolt needs to push outwards, as any real load on the machine would otherwise loosen the drive belt. In which case, the bolt is really loaded in compression, and tensile loads are only relevant when the motor is not in use and the belt is off.

Or not – can the original poster please explain?

Tim

[pgrbffParticipant @pgrbff]

Posted by Tim Stevens on 31/01/2021 14:39:43:

Once more, a problem which cannot be addressed properly as the information given is simply not there. Try to put yourself in the position of the person reading your request, and think 'Would I really understand this problem?'

If the rod you need attaches to the hole behind the slot in your second picture, and the plate pivots around the bottom hinge, it seem inevitable that any rod, whatever it was made of, would have to be bent – or no adjustment would be possible.

And I wonder about the use of a 'heavy three phase motor' on a device which looks – well – almost delicate. Especially the single hinge which has to cope with the weight, and the belt tension, and with a plate which is already well out of line…

Not the news you want to hear, perhaps.

Regards, Tim

 

Once more, and it never ceases to amaze me, criticism, but you clearly haven't read the original question, which was a simple request to determine if it was possible that a machine manufactured in Italy had imperial threaded rod and what size it may be.

Edited By pgrbff on 31/01/2021 16:02:52

[pgrbffParticipant @pgrbff]

Posted by Tim Stevens on 31/01/2021 15:45:14:

A further thought has occurred to me:

In use, the tension of the belt would pull the motor towards the column. [Unless I have totally misunderstood the photo.]

This means that the 'tensioning' bolt needs to push outwards, as any real load on the machine would otherwise loosen the drive belt. In which case, the bolt is really loaded in compression, and tensile loads are only relevant when the motor is not in use and the belt is off.

Or not – can the original poster please explain?

Tim

I'm not an engineer and I got a dismal E in physics A level.

The weight of the motor falling away from the column puts the belt under tension. So the threaded rod is being pulled, which to my mind is putting it under tension?

[pgrbffParticipant @pgrbff]

Thank you all.

As with so many threads, this one seems to have taken on a life of its own and no longer relates to the original question, which was simply to determine if it was possible that an Italian machine manufactured approximately, and here I'm only guessing, 50-70 years ago could have imperial threads'#.

Having determined it may be imperial I simply thought buying a high tensile bolt or threaded bar from an engineering or quality fixings supplier rather than a mild steel threaded bar from everyone's favourite auction site would hopefully ensure a better quality product. It was not intended to discuss whether HT rod was strictly necessary.

As I have to have it posted to Italy the difference in the price of the fixing would be small in relation to the cost of posting it to Italy, especially after Brexit.

Thank you all again.

Edited By pgrbff on 31/01/2021 16:19:01

[Howard LewisParticipant @howardlewis46836]

Looking again at the picture of the motor mounting plate, these thoughts come to mind.

1 ) It looks as if the motor tensions the belt by swinging outwards, so that any adjuster would be under compression.

Having said that, the compressive load needed to bend a 1/2" BSW thread would be likely to bend shafts, ruin bearings, if the belt did not fail prematurely.

2 ) Since the adjuster engages in a slot , the angular position of the motor mounting plate will tend to exert a bending moment on the thread, but only if a nut was fitted on each side of the slot.

maybe the way to avoid such problems in the future would be to hinge the adjuster thread to a mounting point screwed into the main body. A clevis end on the adjuster pivoting on an eye in the main body would suffice.

Departing from prototype, and presumably being in Italy, the obvious choice would be some M12 studding as raw material

Howard

[Tim StevensParticipant @timstevens64731]

Ok, let's go back to the original question – which was headed 'Metric Thread Sizes'. The first question is asked in the second message from pgrbff. The answer to the question does not relate to Metric Threads at all, but let's have a go. Could the makers have used a Whitworth thread? Yes.

The rest of the debate has been intended to be helpful, and to increase the understanding of the questioner and those answering. If that is not the point of this sort of forum, then I am not the only one to have misunderstood.

My question to the original poster is this – Does the answer 'YES' meet your needs?

Cheers, Tim

[Author]

Posts