surely they are not that bad

[facthunter]

engine parts are generally in MILLImetres IF not inches.   Nev

[old man emu]

2 hours ago, Old Koreelah said:

Those measures would work okey if everyone was about the same size. My cubit is quite a bit longer than most.

 

That was the reason for engraving a reference set on a wall. The architect said, "These are the dimensions you are to work with." The building supervisor could then put a stick up against the engraving and mark the dimension. Then the building supervisor could go to where work was being done and have the foreman mark his measuring stick off the supervisor's and use it to do the layout and to check the work.

 

If you think about it, we still do the same thing, although the original prototype metres bar used from 1889 to 1960 has been replaced by definitions based on wavelengths which require the definitions of distance and time. Not something you can readily check when you are buying a length measuring tool at Bunnings. 

 

[facthunter]

It used to reference a Platinum- Iridium bar at one stage. kept in France.   Nev

[old man emu]

5 hours ago, facthunter said:

It used to reference a Platinum- Iridium bar at one stage. kept in France.   Nev

That was the Master one. The original and 29 copies in all were made in 1889 and one was given to each of the signatories to the Treaty of the Metre, an international treaty that was signed in Paris on 20 May 1875 by representatives of 17 nations: Argentina, Austria-Hungary, Belgium, Brazil, Denmark, France, Germany, Italy, Peru, Portugal, Russia, Spain, Sweden and Norway, Switzerland, Ottoman Empire, United States of America, and Venezuela. By 1889, Great Britain was a signatory, and ironically for the French, it was a British company that made the bars because of the high standard of their work. Australia became a signatory in 1947.

[Old Koreelah]

Being a contancerous Geographer, I prefer the original standard from which all metric messures were derived: one ten millionth the distance between the North Pole and the Equator, through France. 
 

 

[nomadpete]

1 hour ago, Old Koreelah said:

Being a contancerous Geographer, I prefer the original standard from which all metric messures were derived: one ten millionth the distance between the North Pole and the Equator, through France. 
 

 

Can you show us a piece of that sitting on the floor, to check my Bunnings tape measure against?

[Bruce Tuncks]

Have you noticed its hard to buy imperial drills at Bunnings these days? And as for nuts n bolts, the proper imperial ones are getting harder too.

I would like to buy a kit containing all the nuts n bolts that Jabiru use in their 230. I sent an email to Jabiru but alas they didn't reply.

Gosh it's hard to buy bolts because you need to know the grip length first. I quite understand Bunnings telling their guys to forget imperial stuff.

[old man emu]

5 hours ago, Bruce Tuncks said:

you need to know the grip length first.

That would apply equally to metric fasteners. 

[spacesailor]

GO buy " imperial taps & die's.

Plus extra Long bolts , measure the shank ( grip length) , plus thread length needed . Cut the desired size , then retread your new bolt.

spacesailor

[old man emu]

Let's talk about a fastening assembly consisting of a bolt, a washer and a nut. The bolt has several sections, each performing a specific job.

 

We use this assembly to join two or more pieces of material together, as illustrated.

 

The first thing a bolt does is replace what has been removed when the hole for it was bored through the material to be joined. Therefore, we need the diameter of the shank to be as close to the diameter of the hole as practicable. (Ignoring close-tolerance fittings at this point.) So, we want a smooth shank all the way from top to bottom of the hole through all the material. Grip length is the length of the unthreaded portion of shank. Choose a bolt with a grip length equal to or slightly greater than the thickness of the material that you will be bolting. 

 

The second thing this assembly does is clamp all the material together. This is achieved by applying a compressive force to the bolt. That is the job of the nut. When the nut is wound onto the thread so that the head of the bolt and the bolt itself are in contact with the surfaces of the materials, the compressive force begins to be applied. As the nut is wound further along the thread, the compressive force increases. The compressive forces initially react on the threads of the bolt, distorting them because the effective diameter of the threaded length (minor diameter) is less than the diameter of the shank (major diameter). The cross-sectional area of the bolt between two adjacent roots is insufficient to resist the compressive force introduced by the nut. At the same time, and for the same reason, the threads of the nut are distorting.

The friction between the nut and the bolt gives rise to the force we measure when "torquing a nut". That is why, when torque specification are given, it is also mentioned if the measurement should be taken with the bolt lubricated or dry. If no mention is made in the specifications, it is taken that the bolt is unlubricated.

 

The final part of the assembly is the washer. Here we will only mention the simple flat washer, as there are many other washers used for specific functions. If you have used a bolt whose grip length is a tad longer than the thickness of all the materials to be bolted together, then there will be some of the smooth shank protruding from the hole. You must make sure the nut isn't bottomed out on the last thread so you need a washer to cover the runout. The washer also acts as a sacrificial surface that the nut can rub on to prevent damage to the surface of the materials being joined. Usually where metals are joined, the washer is only slightly wider than the nut, but when bolting wood together, you need to disperse the force created by the tightening nut. In this case you use a washer with a much larger diameter than the nut. These are called "penny washers". In the UK, the name originally comes from the size of the old British penny, but in the USA they are called "fender washers".

 

Fastening materials together first involves applying a compressive force, which we can say is from bolt head to nut. Once the materials have been fastened together, the joint may have to deal with loads acting at an angle to the line between bolt head and nut. These are shear forces, and the ability of the bolt to resist them depends on the metallurgy of the bolt and its cross-sectional area. 

 

This assembly can be used to provide a pin as part of a hinge joint. When it is used in this way, a bolt with a suitable shank length is used, but the need for compressive forces is not as important, so the nut can be secured to the bolt using a pinning system.

 

 

 

showing two full threads when the nut is tightened.

[Old Koreelah]

Very clear explanation of a fastening system many of us use but never understand.

The difference between cut and rolled threads is another worthy topic.

[onetrack]

I work with a lot of older American-built equipment and it all uses inch measure fasteners and threads. I don't have any trouble acquiring them, but I don't go to Bunnings for my fasteners.

[spacesailor]

LEE Bros Engineering supplies 

6 Dunlop St

PARRAMATTA

nsw 2151

Always had whatever I needed .

spacesailor

 

[old man emu]

2 hours ago, onetrack said:

I don't go to Bunnings for my fasteners.

Horses for courses. Stuff from hardware stores is OK for jobs where the stresses on the fasteners are pretty insignificant, but for anything mechanical you want good quality. And the easiest test of quality in hardware is the price you pay per item. The stuff you see in the popular hardware stores can seem expensive, but when you are comparing prices you have to consider how much the monopoly of supply these chain hardware stores have contributes to the way they set their prices. 

 

If I want to buy hardware to stand stresses, I'd rather go to a supplier where I know that out the back they have racks of nuts and bolts in cardboard boxes, and will sell to me by the unit, not a half a dozen items in a vacu-formed cover stuck to a cardboard backing with multi-coloured text all over it. Also, suppliers like Lee Bros in Parramatta or Bolts & Industrial Supplies at Smeaton Grange (my go to) have counter staff who know why you need a fine thread for one situation and coarse for another, or know the difference between a screw that is corrosion resistant and one that's simply CAD plated.