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Member postings for duncan webster

Here is a list of all the postings duncan webster has made in our forums. Click on a thread name to jump to the thread.

Thread: THE NUMBER 9 !
24/08/2021 23:45:05

The 7 would be better as 9 - sqrt(9) + 9^0, which would be 9 - 3 + 1 = 7

The symbol for 0.99999......... in my young date was a dot above the 9, not a line

Anyone know where I can get one, apart from Journeyman's South American Rainforest, which I must admit I didn't get

24/08/2021 19:51:16
pressed the wrong button

Edited By duncan webster on 24/08/2021 19:51:55

24/08/2021 15:12:57

(sqrt(9))! - 9/9

3! - 1

3*2*1 - 1 =5

Does Bodmas cover factorials?

Edited By duncan webster on 24/08/2021 15:14:08

Thread: Unusual Go-No Go Tool?
23/08/2021 23:55:01

But the pointy thing would be aimed at the ceramic,

Thread: Engineering / Modelling Books for Winter Evenings?
22/08/2021 17:16:51

1956 is when the book wa published. The disaster happened in 1879 I think

22/08/2021 17:16:46

1956 is when the book wa published. The disaster happened in 1879 I think

Thread: How the crisis in container ships could ruin Christmas
21/08/2021 20:47:46

It won't ruin mine


E Scrooge esq

Thread: Making Tapered Castellations in Aluminium
20/08/2021 23:55:12

I have a 4" and a 6". The little one gets quite a bit of use rounding the ends of rods and valve gear bits, the big one very rare, but when you need it you need it. As Jason says for holes on a pcd coordinate drilling is quicker than setting up the rotary table, a pity the chinglish manual is incomprehensible, I use zeus and a calculator

Thread: Ploughing engine running on air
20/08/2021 23:49:05

When I see something like this I reckon I should take up knitting. It is so far out of my league.

Thread: Strange stain in caravan
20/08/2021 23:45:40

The stuff used for cleaning false teeth is reputed to shift tea stains and not leave everything tasting of bleach. Can't vouch for it as I still have most of my own gnashers

Thread: The "Lost art of hardening copper"
20/08/2021 13:18:41

I believe lots of tools used down coal mines were made from Beryllium Copper, not because it was better than steel, but it wouldn't create sparks to set off firedamp explosions

Thread: Chinese "K40" laser
20/08/2021 00:09:19

The windscale fire was burning graphite. Helped by them turning up the wick on the cooling fans in an attempt to blow it out. Only when a hero decided to direct a fire hose into the inferno did they put it out. Probably a matter of scale, I suspect a small piece would self extinguish

I think the guide vanes on V2 rockets were graphite but the hot gas didn't contain oxygen, so they did not burn away

Thread: Ruggedising a Type 17 Stepper motor electrical connection
19/08/2021 13:13:46

photo below, but mine is a much bigger motor. There is a slight bend in the plate to accomodate the draft angle on the plastic box, and 2 of the motor securing screws have been replaced with longer. Mine were tapped into the outer end plate, not recessed like the OP's. It's not the easiest place to take photos, can't get camera far enough away reallyimg_20210819_120001.jpg

Thread: Tailstock DRO
19/08/2021 13:02:36

I've found another Bill Gates inspired issue, at least I think it's him. I tried to upload a sketch to a fairly new nano (bought within the last couple of years) and my new computer couldn't find which port it was plugged into. Tried with a UNO same, then tried both on my laptop and both worked. It appears that the USB chip is 'obsolete' and Mr Gates has decided we shouldn't be using it, and so W10 cannot now find the drivers. I sorted this after much googling by downloading and installing CH341SER.EXE

This sorted mine out, but wasted a couple of hours

Thread: New Workshop Progress
18/08/2021 18:27:47

I've got a brand new 2 way distribution box you can have for the postage. If you're interested I'll dig it out and take a photo

Thread: Ruggedising a Type 17 Stepper motor electrical connection
18/08/2021 18:24:22

What I did was make up some longer bolts to replace those which hold the whole thing together and use them to hold a plate to the end. This plate protruded beyond the connector and supported a plastic box, in the side of which I had a grommet to support the 4 core cable. My motor didn't have a plug socket arrangement, so soldered connection inside the box

Not a brilliant photo, but it might help. I'll take a better one if it would help

belt guard 2 (small).jpg

Thread: Myford VM-C - Good machine
18/08/2021 14:31:18

I don't think it has a fine down-feed on the quill, which is a small drawback.

Thread: Converting fractions to decimals
17/08/2021 21:49:55
Posted by Michael Gilligan on 17/08/2021 15:19:06:
Posted by duncan webster on 17/08/2021 14:46:06:

But I don't have a ruler or a caliper that has 80ths of a millimeter on it. Decimals on a calculator is the way to go every time for conversions unless you are on the cad.



I presume that you write in jest, Duncan … But just in case: The point was that the fractional calculation is exact, and the decimalisation thereof is only done on the answer.


but 40.8625 is exact, because 1/80 = 0.0125 exactly, so multiples are exact at 4 decimal places (or 3 for even numbers off). I was just making the point that 42 + 69/80 is a fairly useless dimension. Actually converting any number of 1/128" to metric gives a decimal number within the precision of my calculator, 25.4/128 = 0.1984375 exactly. In reality I'd use 0.20 as my DRO doesn't do better than 0.005

Yes there will be some situations where the decimal runs out of decimal points, but not model engineers converting imperial fraction lengths to metric.

Edited By duncan webster on 17/08/2021 22:16:08

17/08/2021 15:09:10

I'm not suggesting using logs gives the wrong answer, but it takes longer for no benefit, and as it takes longer it costs more

17/08/2021 14:46:06

But I don't have a ruler or a caliper that has 80ths of a millimeter on it. Decimals on a calculator is the way to go every time for conversions unless you are on the cad.

SOD will have to explain where his fraction comes from, I make it 6858/160, which is of course the same as 3429/80

Log tables, I'm not surprised the previous contributor's boss raised an eyebrow, I'd have raised the roof, slow and more chance of error. I remember a chap in the design office doing sums on a mechanical contraption that you set up and wound the handle till it went ping, then wound it back one turn. It worked, but as soon as he got a calculator it went in the scrap. I'm surprised no-one has bemoaned the demise of the saggar makers bottom knocker

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