Rethreading screws (the search for replacement screws)

I am in a pinch ...

I think I need to replace a shoulder screw. It all looked like the sunny side of the street, that it would be a regular M5 screw. A slotted screw, but still ... no problem. Off to the local store, bought a box.

At home I tried it, and well ... no luck. Remeasured, still looks like it should be M5.

Waffling around on the internet, I happened to see references to M5 having a finer pitch (0.75 mm) earlier on (pre-1970). Short of trying to build a time-machine and go back in time ... what are the options?

Can one rethread a standard M5 screw? Would a machinist be able to make a bunch of replacement screws from an original one?

EDIT:

I am adding a photo of the screw, this should be in the swing mechanism of a Sinar Norma. I measure it as 17 mm long, with a diameter of 5,19 mm.

Attachment 207822

Seems McMaster Carr has special 5mm screws that don't fit normal pitch

"Fine-Thread Metric 316 Stainless Steel Button Head Hex Drive Screws

Closely spaced threads on these screws fit in holes with a fine pitch. They're not compatible with standard metric threads. Made from 316 stainless steel, they are more corrosion resistant to chemicals and salt water than 18-8 stainless steel screws. Screws may be mildly magnetic. Length is measured from under the head.

3D CAD models availableFor technical drawings and 3-D models, click on a part number.

Lg.,
mm Threading Head
Dia., mm Head
Ht., mm Drive
Size, mm Tensile
Strength, psi Each
316 Stainless Steel
M5 × 0.5 mm
10 Fully Threaded 9.50 2.75 3 80,000 90943A117 $4.45
12 Fully Threaded 9.50 2.75 3 80,000 90943A118 4.96
16 Fully Threaded 9.50 2.75 3 80,000 90943A119 5.50"

A machinist should be able to cut threads of any kind either with single point threading or with a thread cutting die after turning a blank.
How badly mangled is the screw ? if the screw is damaged there may damage to the threads in the screw hole.

Thanks Tin Can and Jim,

good to know where to start at least, and that it might be possible to get out of the bad situation. The screw is partly mangled - I guess it was galling. There was a large amount of lubrication residue, and traces of some dry, white powder. I may need to soak the parts and clean it out much better next time. The threads of the steel part are fine, as far as I can see, and I am able to thread a clean screw all the way through, with no obvious resistance.

A good few lessons learnt.

I always try my Thread Files on damaged screws first

Even if the thread and file mismatch, I use the closest possible

For small screws put file on bench or in vise and rub screw over the cutting edges

Here is one that has 0.75 mm pitch, I have at least 4 thread files, each with 8 different pitch

https://www.amazon.com/General-Tools.../dp/B0017R1DOM

are you sure its metric? a 10-32 is very close to that size.

What is the screw off?
This might help id the thread [ie whitworth, BA, unified, or metric]
The pitches of the various thread forms are:
Whitworth 1/4 - 20 - 0.0500 inch
1/4 - 26 - 0.03846 inch
Unified #10-24 - 0.04167 inch
#10-32 - 0.03125 inch
Metric 6mm 1mm OR 0.75mm
BA 0BA 0.03937 inch


Regards
Tony

[QUOTE=Jimi;156821M5 having a finer pitch (0.75 mm) earlier on (pre-1970).?[/QUOTE]

Assuming it is 5mm x 0.75 pitch then machine screws of this size are available from Amazon and others

regards
Tony

Metric pitch standards never changed, but in certain diameters there are both standard and finer thread options. Then you've got the oddballs like Whitworth, "British metric", or custom wholly nonstandard. I've never encountered a use for the strange ones except on certain Brit cars. Ironically, willy-nilly wholly nonstandard screws are more apt to be current Chinese or Indian junk screws, as are many of the hardware screws screws on the market now which are improperly made. Here in the US, I'd try McMaster first since they have actual specs for each item and are straight shooters. I have no idea about EU sources. Really specialized dealers without an internet profile are going to be tricky at the moment due to the virus issue. Normally, there's a superb nut n' bolt house here; but they aren't even open at the moment.

Thanks for your answers - I have been assuming that it has metric threads, but assumptions only go so far ...

I bought some tools to get a more exact measure, since a loupe and a ruler is too rudimentary in this case. I am going to see if I can make a photo of the screw too, just to show the damage.

Quote:

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Originally Posted by Drew Wiley

oddballs like Whitworth, "British metric", or custom wholly nonstandard., willy-nilly wholly nonstandard screws are more apt to be current Chinese or Indian junk screws,.

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Drew,
I think you are showing an unfortunate bias.
The ‘oldballs’ are in fact standardized thread forms that have or had a specific purpose. For instance, pipe, gas, cycle, microscope and instrument threads. Also there are left hand threads, multi-start threads, tapered threads, as well as industry- specific threads.
There are also differences in thread forms - for instance acme – and similar threads but with various pitch angles.
Your ‘ willy-nilly wholly nonstandard screws are more apt to be current Chinese or Indian junk screws’ tend to be cast– hence they do not [cannot] have the precision of machined screws.

Regards
Tony

Quote:

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Originally Posted by Jimi

I bought some tools to get a more exact measure, since a loupe and a ruler is too rudimentary in this case. I am going to see if I can make a photo of the screw too, just to show the damage.

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For pitch measurement a ruler can be sufficient if you measure over 'N' pitches the more the better, then divide that measurement by [N-1]. For diameter use a micrometer [without inferring anything 25.4mm = 1 inch so multiply or divide as appropriate].

Alternatively, if there is a second identical but undamaged screw take that to a hardware store and see if you can find a nut that fits.

regards

Tony

Thanks Tony,

I took one of the undamaged ones to the local store but no luck there, since they only have standard m5 nuts, which jams almost immediately - "sir, the threads on this screw must be damaged, I think". I'll go downstairs and see if I can measure it a bit better with the ruler again, otherwise the thread gauge will arrive tomorrow.

Somewhat unrelated, I happened upon a treatise about the finer details of JIS threads, and it amazes me how much there is to see and know.

Quote:

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Originally Posted by Jimi

otherwise the thread gauge will arrive tomorrow. .

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if I remember right, thread gauges are specific to thread forms - so a metric thread gauge will do metric threads, but will not fully identify the pitch of other thread forms.

Anyway have fun

regards
Tony

I still don't see anywhere where you tell us what the screw goes to (ie: what camera?)

Hi Tony. I once worked at a specialty supplier to machinists and mechanics that had an amazing selection of bolts, screws, taps and dies, etc. - all kinds of special applications almost impossible to find anywhere today - special antique lock threads, gunsmithing taps different from anything else, and yes, totally unique threads deliberately designed to prevent people from repairing their own import cars - even corkscrew left-hand pitches that no thread gauge will read. We did business with over fifty different car importers, and all but one had crooked repair departments; and many of the auto models themselves had all kinds of deliberately engineered flaws to keep dealers successful - repairs have always been more profitable than actual auto sales. That's still the case today. But the fellow in charge of that particular department back then was an ex-NASA optical machinist, so really knew his stuff. I guess you could say all of those things were somehow "standardized"; but my "standard" response to Brit machinists is that if Napoleon had won at Waterloo, everything would be a lot simpler today.

Quote:

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Originally Posted by Drew Wiley

but my "standard" response to Brit machinists is that if Napoleon had won at Waterloo, everything would be a lot simpler today.

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Hi Drew, in terms of what if
How about if the lower 48 and Hawaii were still part of the British Empire and Alaska still belonged to Russia

regards
Tony

I updated the first post to be a bit clearer - with a photo of the screw and where it is going (swing mechanism of a Sinar Norma). I am putting it here too, in case someone can't be bothered to read again.

As for the thread size, I have now tested it against my thread gauge, and it does not seem to be metric. The closest I get is Whitworth (24 G it says) but it still not correct, since there is space between the threads and the gauge. It is unlikely that I get any sort of answer from Sinar, so I may be stuck, unless someone else actually knows.

I once had a similar problem with missing screws on an Oschwald era Arca Swiss. It turned out that it was a JIS thread on that screw, even though the first assumption would be a DIN metric thread.

This is just leftover parts, so I can leave as it is, but it would still be nice to be able to return the standard to a functioning state. I could wrangle past this issue, by putting the screw on the swing lever side and get some thicker flanges to cover the bad part of the thread.

Now we know

Many here including me have Sinar Norma

That kind of damage may be 'fixable' to 'good enough' with a thread file, or even just a tiny triangular file

Thank you for a picture and description

It will be metric of some sort. Everything on my Norma is. A bit of slop can be taken up by Teflon tape if necessary. The Swiss hypothetically ever adopting Whitworth would be equivalent to them giving up chocolate and drinking tea with milk in it instead. The whole Brit system of 1/12 of a cubit-furlong-squiggle was originally based on how far a Druid priest drunken on mead could throw the head of an ox.

Thanks to everyone that contributed to the thread (pun intended, hah) this far.

I have not been able to recognize the thread gauge, but with the help of some guts, a loupe and a japanese needle file set that I bought almost thirty years ago, I have been able to clean up the damage. It goes in easily now and I am set to put it all back together. This "project Norma" has been quite the learning experience.

Quote:

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Originally Posted by Drew Wiley

The Swiss hypothetically ever adopting Whitworth would be equivalent to them giving up chocolate and drinking tea with milk in it instead. The whole Brit system of 1/12 of a cubit-furlong-squiggle was originally based on how far a Druid priest drunken on mead could throw the head of an ox.

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O dear me, Drew, you do have it bad, don't you!!!!!
Commiserations
Tony

Removable thread lock fluid can also be used in minor situations. I've told this story before, Tony, but when I was a kid in high school, it was right around that time the metric system was beginning to be taught in shop classes. Back then, allegedly smart kids weren't even allowed to take shop classes, but had to study Sophocles and Chaucer instead. That left shop teachers with the dummies. So he'd ask them, "How many pennies in a dime, how many dimes in a dollar?" "Ten", they'd respond. "How many millimeters in a centimeter?" ... "Duuh, twelve?" "Count your fingers, you dummy!!!" Sure enough, there would be some inbred hillbilly kid in the back row that had six fingers on each hand.

Quote:

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Originally Posted by Drew Wiley

shop classes. "How many pennies in a dime, how many dimes in a dollar?" "Ten",

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Drew, as George Bernard Shaw [is reported to have] said we are 'Two nations divided by a common language.

what is shop classes?????

In Britain and its empire a 'penny' was one two hundred and fortieth of a pound sterling [not avoirdupois]
In Britain's former colonies [eg the lower 48] a penny is slang for one cent or one hundredth of a dollar.
Other variations are a pint and gallon - 8 pints to a gallon, but in the UK one pint is 20 fluid ounces whereas you use 16 fluid ounces to one pint.
Similarly you use a short ton [2,000 lbs] I use a long ton [2,240 lbs]. Whereas the metric system uses 1000kg to 1 tonne
You use the hash mark [#] in different forms [#2 and 2#] in which the former is a number and the latter weight in pounds
Furlongs, pecks, perches, gills, acres etc are all measures that have, to some extent, be replaced by values in the metric system.
The cubit, you mentioned earlier, comes from the old Middle Eastern civilisations and was never part of the Imperial measurement system

Drew, we can continue this dialogue ad-nauseam, but I think it is of no benefit to the OP or others

regards
Tony

Quote:

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Originally Posted by Drew Wiley

It will be metric of some sort. Everything on my Norma is. A bit of slop can be taken up by Teflon tape if necessary. The Swiss hypothetically ever adopting Whitworth would be equivalent to them giving up chocolate and drinking tea with milk in it instead. The whole Brit system of 1/12 of a cubit-furlong-squiggle was originally based on how far a Druid priest drunken on mead could throw the head of an ox.

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Quote:

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Originally Posted by tonyowen

In Britain and its empire a 'penny' was one two hundred and fortieth of a pound sterling [not avoirdupois]
In Britain's former colonies [eg the lower 48] a penny is slang for one cent or one hundredth of a dollar.
Other variations are a pint and gallon - 8 pints to a gallon, but in the UK one pint is 20 fluid ounces whereas you use 16 fluid ounces to one pint.
Similarly you use a short ton [2,000 lbs] I use a long ton [2,240 lbs]. Whereas the metric system uses 1000kg to 1 tonne
You use the hash mark [#] in different forms [#2 and 2#] in which the former is a number and the latter weight in pounds
Furlongs, pecks, perches, gills, acres etc are all measures that have, to some extent, be replaced by values in the metric system.
The cubit, you mentioned earlier, comes from the old Middle Eastern civilisations and was never part of the Imperial measurement system

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Well Tony, after that you need to be honest and say that Drew is absolutely correct! And don't get me started on BA threads:

Quote:

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starting with 0BA at 6.0 mm diameter and 1.0 mm pitch and progressing in a geometric sequence where each larger number was 0.9 times the pitch of the last size. They then rounded to 2 significant figures in metric and then converting to inches and rounding to the thousandth of an inch.

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Quote:

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Originally Posted by tonyowen

Drew, we can continue this dialogue ad-nauseam, but I think it is of no benefit to the OP or others

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Indeed, sir. The thread is worn out, metric or otherwise.

I have interchangeable blades for my precision try squares, selector button for which kinds of readings on my calipers, quite a variety of rulers etc. The most useful of all are Fishermans tape rules, made of stretchable vinyl, so you can make the marks as far apart or as close together as you wish. Any outfit that sells metric Crescent wrenches sells those too.