I need to tap a hole in a 3d printed part to fit a pneumatic coupler. The coupler measures 9.5mm in diameter. The 1/8 BSP matches the thread but 1/8” is a little bit more than 3mm. I also found a 3/8 Whitworth tap that matches the size of 3/8” but obviously the thread does not.
What measures the 1/8” in the BSP standard?
1/8 BSP (British Standard Pipe) has a diameter of 9.7mm approx.
Dunc
Thank you Duncan,
I have already tapped the part and the coupler fits fine. I am still wondering what has a size of 1/8”, not the thread and not the internal diameter (4.5mm) of the coupler.
Pipe sizes are crazy. They are sized by nominal bore of one particular kind of pipe that originally fit in them, but the key size is the external size for fittings. Pipe walls have mostly gotten thinner as materials have gotten more consistent and manufacturing techniques more reliable, so because the external diameter is the controlled dimension, the real ID is basically always larger than the nominal ID.
So the answer is that when the fitting was invented, the thickest wall pipe that would be attached had a minimum bore of 1/8” (modulo whatever tolerance), but now the 1/8” is just a name.
What amuses me is that having emigrated from the UK (weird mix of Metric and Imperial) to the Netherlands I discovered that gas (*) fittings are all imperial threads on metric pipes.
Eg, here is a 1/2 to 3/8 inch adapter; 1 meter long, stocked by my nearby DIY superstore. Sanivesk flexibele slang PEX 3/8"F x 1/2"F DN8 100cm
(*) Domestic gas, LPG, which is still very common here but being phased out asap.
Not just here, also the UK has some strange mixes of imperial and metric. I spoke a builder in Devon UK, years ago and he told me that he used PVC 6 by 4 sewer pipes. 6 meters long and 4” wide. Maybe his tape measure was not accurate enough to see the difference between 100mm and 4” (101.6mm).
The difference in metric and imperial measures is often just a factor. Not really a problem when you are aware that it is the one or the other. More of a problem is the old English system of the coins. When I went to Britain in 1989 for the first time there was still a shilling coin in use. If I remember correctly it was in use as 5 pence, in size twice as big as the pound. Maybe an occasional visitor to the UK can get used to the old division system but I am pleased they now have just 100 pence to the pound.
Yes, I have a vague memory of my mum taking me to a shop and explaining that today was special because of the money. It was 1971 and the UK went decimal that day. The shilling became worth 5 pence, and coins circulated for a long time.
When I came to the Netherlands in 1998 I had first to adapt to Guilders (which used a 25ct coin) and then again when the Euro came in and the Guilder (and it’s ‘quarter’ value coins and notes) went away.
For nostalgia/reference.. there were 12 pennies to a shilling, 20 shillings to a pound. So 240 pennies in a pound. Also six and three penny (known as thruppence) coins. I have a jar with some of these in, also tiny 1/4 penny coins.
I remember my mother kept a jar of ‘farthings’ on the mantlepiece, because a loaf of bread was 3 farthings (4 farthings to a penny, 240 pennies to the pound) and my first weeks wages were £3-7-6 ( 3 pounds, 7 shillings and 6 pence.
The smallest I had ever seen was the ha-penny. Was there anything smaller in value than the farthing?
The set above was given to me by friends from Devon in the beginning of the nineties. They said that at the time all coins were still in circulation but I cannot remember that I have ever seen a crown or florin “in the wild”.
I remember traveling through Europe in the early eighties and having to stop at the borders and swap currencies from one country to another. It was very confusing for this American!
