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Member postings for john halfpenny

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

Thread: WHY THE TANG?
16/09/2020 16:48:16

Patent documents can be a good starting point. Be aware, however, that whilst everything written in a patent document must be true, the whole truth is not a necessity. Likewise, the necessary features must be shown completely, but other related but inessential features may be omitted, to another scale, or adjusted to avoid disclosing helpful aspects unrelated to the invention as such. I would always take care, especially with seemingly detailed drawings of which the victorians were great exponents. (Speaking as a 40 year veteran of this stuff)

16/09/2020 09:04:02

Can't we agree that the tang can serve both purposes. I was taught that the taper should be enough for drive, but clearly some machine tools use the tang (also).

Thread: BSF and Whitworth "Across the flats " sizes.
12/09/2020 12:16:00

Morris were notorious pre- and just post-war for using metric threads with imperial heads, owing to the parsimonious Bill Morris acquiring some metric threading tools with the Hotchkiss engine plant in Coventry.

Thread: Bench block for small parts - ice hockey puck
11/09/2020 20:49:07

I have use them for years as jack packers on my car lift and trolley jack (in a sensible and appropriate manner)

Thread: BT
14/08/2020 08:32:46

And Virgin 'upgraded' me last year from payg to a monthly contract. They took my balance without asking to pay tge first mon the - theft by another name. Needless to say I am no longer a customer.

Thread: Centec mill cutter speed
10/08/2020 17:32:00

Or use a cycle computer. I have an £8 one. Set the wheel size as 1667mm, and the km/hr display is an analogue of rpm - ie for 24.4 km/hr read 244 rpm. The pick-up is small enough to put just about anywhere accessible on the spindle. A bit of maths on wheel size will accommodate a reduction gear.

Edited By john halfpenny on 10/08/2020 17:33:37

Thread: Training school auction
06/08/2020 15:24:33

Nevertheless Dave, we cannot all wash each others windows.

Thread: Make your own Tokamak
02/08/2020 21:21:34

Have a look at Iter site tour videos on you tube. The latest, from a day or two ago, shows the massive engineering effort as assembly starts. The magnetic field confined within the Tokamak is alleged to have power sufficient to lift an aircraft carrier. I can't help thinking we shall more likely rely upon windmills and solar panels.

Thread: Sieg SC4 Carriage travel limited by collision with splash shield
02/08/2020 16:33:46

James, probably not an immediate issue, but make a plan to fix it - otherwise it will get in the way when you least need a problem

Thread: Lathe turning speed in relation to different metals
01/08/2020 10:42:02

Mr Wheeler, I thought it was incisive and excellent advice-but it disappeared.

Thread: 33mm Spanner
26/07/2020 08:40:33

That's a good spot for a large mouthed, slim spanner that is not too long. I'll be getting one to keep by my mill.

Edited By john halfpenny on 26/07/2020 08:44:29

Thread: Kennedy Hacksaw
23/07/2020 22:48:28

Half a turn clockwise opens the valve to allow the blade to drop more quickly. In other words it gets the blade quickly down to the workpiece , then turn it back to reinstate full damping. With 160 weight oil, the fully damped downward movement is very slow, so the valve speeds things up.

21/07/2020 16:59:59

You'll have to make one. Here's a simple version I made last weekend; single bolt mounting underneath is ok. 160 weight oil ( like treacle) works well in the dashpot; much better than engine or axle oil, which is far too thin.20200721_165138.jpg

Thread: Attempting To Make My (new to me) Zyto Beautiful
18/07/2020 15:21:49

At least link rhe bottom of the leg frames, and put in a diagonal to stop lozenging. No much work, but a big increase in lateral rigidity. The toppling risk is not insignificant.

Thread: Interesting bike ride today
17/07/2020 19:33:59

We have bats, and when building a new workshop the local authority insisted on a bat brick, with a narrow slit as entrance. I put a bat box on the inside, with viewing panel normally covered by a hinged flap. But when I look, all I have ever seen is a startled blue tit. The bats are happy in the house loft, judging by the piles of droppings at one end.

Thread: Fiber change gears
17/07/2020 12:08:15

Henry Ford used layered tufnol for camshaft gears on millions of cars. Later he used macerated tufnol, and later still a type of nylon. No problems from engine oil.

Thread: How to join?
16/07/2020 19:00:05

Well, it's got two chances. Not very helpful I know, but an unknown.

Thread: Nivellator
16/07/2020 09:56:05

I think 'Nivellator' is a trade mark, or at least an invented word -not uncommon in German. The title of the patent document translates as 'Level (surveyors) and measuring device'. Knowing this I suspect it belonged to my wife's grandfather, who was a sewage works foreman in the 1920's, no doubt with an interest in the flow of fluid through pipes, probably without the assistance of pumps in his home location.

15/07/2020 22:35:54

See my post above about language. Thank you Neil

15/07/2020 21:07:56

I think you are right Robert. The scale allows for 1-10 yards, which would fit with drainage works. The spring is very very strong; not sure why that is so, but suspended from the loop, the scale reads 0 degrees with the bubble level. Thank you.

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