Steel used in bolts

During recent discussions on different steels, repurposing steel bolts was mentioned.
Does a particular grade of steel bolt e.g. 8.8 correspond to a particular steel, or do different manufacturers use different steels and treatments to meet the grade requirements. I remember some years ago being offered some approx 12" bolts at a steam rally for a low price, and was told that many bought them to repurpose. I have often regretted not buying some, but at the time had no use for them.e
Is there a difference betwween old and newer bolts
I have also aquired a large collection of brass bolts nuts and screws. Is a particular grade of brass used for these? How does their strength compare with steel?
Thanks
Happy New year to everyone
Keith

I don't know about steel bolts but brass ones I have found are not generally free machining. I think the threads are rolled so a different grade is used - I think CZ121 is best for machining, the stuff used in bolts etc is more sticky.

I cannot comment on the strength of brass bolts, but I was impressed with woodscrews when I modified some for a particular job, much stronger than expected, close to mild steel.

 The spec for bolts is for the finished bolts, so the materials may differ from make to make slightly.

Edited By old mart on 01/01/2023 16:21:04

Bolts are made to a specification, and any metal that does the job can be used to make them. The steels found in different bolts is likely to be similar, but there are no guarantees. Might machine OK or be difficult. An obvious example is 8.8 stainless steel bolts aren't made from the same alloy as ordinary 8.8 steel bolts.

Brass is different again. Main advantage is low corrosion with good heat and electrical conductivity. Brass isn't first choice for strength. There are a multitude of different brasses. Common 60:40 has a yield strength of 95MPa, compared with steels which range between 200 and 1200MPa. I'd expect a Brass bolt to be only half as strong as steel at best, and considerably weaker than a 8.8 or better bolt.

Dave

The trick for putting brass screws into oak without them breaking was make the hole with a steel one first

When making jigs and fixtures for RR we had to use unbrako made socket screws where required and proof was supplied. We found other makes had slightly different head sizes and somtimes the socket was a diferent size for the Allen key. We didn't have any tests for materials.

David

"8.8 stainless steel bolts" is an oxymoron.

Robert.

Hi Keith,

Ordinary 8.8 bolts are often made from (unalloyed) steel with 0.35 to 0.45% C, the 10.9 and 12.9 bolts are usually made from steels alloyed with Chromium or Chromium and Molybdenum.

Thor

.

Oh dear … that’s unfortunate:

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https://www.navstarsteel.com/grade-8-8-bolts.html#sizes

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MichaelG.

Edited By Michael Gilligan on 01/01/2023 17:58:52

Years ago I tried turning down some shanked M10 bolts from the local DIY supermarket. The material was horrible. It was not a substitute for mild steel bar (free cutting or not).

One could say "What was I to expect".

JA

A friend of mine who is a lifetime boatbuilder says that brass and bronze wood screws should be screwed in with a waterproof grease or fat to make them easier to fit and protect them from internal corrosion. I have tried the grease bit and it seems to work but don't know about the corrosion bit although it sounds logical if you are screwing into something like oak.

This was to avoid the blue stains from steel ones that react with the tannin in oak creating a blue stain.

Lubricating any wood screw makes insertion easier. Wax is another lubricant, some do come prewaxed.

Come back to me when you have a tracable source. That table is titled "stainless steel" but the content says "carbon steel". ASME SA324 does not exist. It is a supplier website of dubious veracity.

An 8.8 bolt is by definition high tensile steel. Minimum tensile strength 800 MPa. Stainless steels are lower than this, typically 500 to 700 MPa for common grades. A4 is used for some fasteners and is available in 800 MPa minimum tensile strength (A4-80). However this does not meet the 660 MPa minimum yield strength of the 8.8 specification.

Robert.

My grandfather and my uncle, both master cabinetmakers/carpenters, swore by Brylcreem hair grease back in the 60s. Run the screw through your hair before screwing it in and all was well, apparently.

As for using bolts as stock to turn things out of, seems like they are frequently lousy material to machine. Part of the problem is the thread has been rolled on there, so it is work hardened and not easy to machine. The head has been cold formed out of the original round bar the size of the shank, so it is well work hardened too. The plain shank in between the thread and the head is sometimes OK.

I suspect the effect would be worse on brass bolts and screws.

.

Hence my comment, Robert

I have no intention of ‘coming back to you’ … I was simply quoting something unfortunate.

MichaelG.

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P.S. __ You might find further entertainment on this page:

https://www.steelmetind.com/high-tensile-grade-8-8-bolts.html#chemical

Edited By Michael Gilligan on 02/01/2023 09:23:15

In the 1960's the chippies who worked alongside me at a shop fitting company always kept a bar of hard soap to lubricate screws, it something I've continued doing myself, My father was taught this in the RAF as well

'Dubbin' was the lubricant of choice for woodscrews  by my Grandfather.

Regards Ian.

Edited By Circlip on 02/01/2023 11:39:23

Hand soap is likely to cause corrosion in some combinations of wood and metal due to it not being PH7 (neutral) and including water in it. I have seen this myself so I would avoid soap and stick with wax or some other plain lubricant.

Martin C