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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: Using a brick garage as a workshop
18/05/2015 00:22:49

I did my walls much as you second link, floor with mastic asphalt. You have to pay someone to do it, but it's very quick and very good, flat and damp proof

Thread: 5" Lion
14/05/2015 12:43:20

Have any of those who slag off the Australian boiler code actually read it? I have, and have compared it to relevant British Standards. It is a well written document which compares well with BS, and is not over-conservative. Why we in UK do not have a similar document, or simply adopt the Australian one is a mystery to me.

Thread: Help required re: centec 2b motor replacement
05/05/2015 10:18:56

2B motor is mounted inside the cabinet under the machine. When fitted with single phase motor they tend to be very noisy as the cabinet acts as a sounding board. When mine died I fitted a three phase motor and it transformed it, sweet as a nut now. Fitting the motor is something else, I eventually managed it using loads of wooden packing and a car scissor jack.

I still have the old motor, its centrifugal switch is blown otherwise it's OK. It could be made to work with a manual start button, if it's any interest give me a PM

Thread: Basic electronics help
02/05/2015 01:42:05

I found this very helpful to get me going on Arduino. Very much easier than PICs

Thread: triple start tap die
21/04/2015 22:12:04

why not screw cut it?

Thread: Colchester capstan tooling queries
21/04/2015 22:01:59

Just an idea, which might not work. Make your cotter with it's scollop, but instead of a turned down bit at the top, drill it right through on the axis, tap the bottom end and drill the top end clearance. Then cut it in half so you have 2 bits with 1/4 circles cut out. Then on your 1" shank cut out a half moon to clear the bolt which you are going to pass through the top bit into the bottom bit. It means you have to fully remove the bolt to change tools.

Otherwise, can you make up a bush and loctite it in to restore the 3/4" dimension

Thread: electric boiler water pump
21/04/2015 20:13:19

That last post is rubbish! I can say that because I wrote it. I'd forgotten that the pump is single acting, and even then has a very non constant torque during delivery. The calculation of energy input is correct, but you need a motor which will deliver a torque of piston area * pressure * stroke/2. Use consistent units metres, and pascals. Thus 10mm bore and stroke working to 0.69 MPa is (0.01^2*pi/4) * (0.01/2) * 690000 = 0.27 N.m. Then add bit for inefficiency. If you want to be sophisticated you can put a flywheel on the hight speed motor shaft, or use a multi ram pump.

Thread: EN STEELS and their uses
21/04/2015 19:53:06

EN standards for steel is long obsolete. BS 970:1991 is what I used when still employed, EN3 would be 070M20. Very useful site giving equivalents and typical use at

Thread: electric boiler water pump
21/04/2015 19:44:56

6mm bore 5mm stroke seems a tad small even for an Invicta, but you can scale it up from the info on the advert.. Power required (watts) is (simply feed rate in cc/sec) * (boiler pressure in MPa). 100 psi is 0.69 MPa. A big pump going slowly works better than a little pump going quickly, the balls have time to get back on their seats properly. You need a bit in hand to cover mechanical losses.

Thread: captive gauge glass valves
21/04/2015 19:34:26

If your inspector is failing a boiler because it doesn't have captive valves he is exceeding his authority. This was discussed in ME some time ago.

Thread: Harold Hall Simple Dividing Head
21/04/2015 19:20:07

Was this published in MEW? I'm too mean to buy the book!

Thread: Thomas Bending Rolls
18/04/2015 11:26:49

Using EN8 won't make any difference to deflection, it has the same Young's modulus. Unless you're bending it so much that it yields of course, but then it would be permanently bent.

Thread: EMG-12 Endmill Re-sharpening module
13/04/2015 19:45:32

I hope this isn't too stupid! If using and end mill correctly it is actually cutting on the side. Apart from restoring the corners, sharpening the ends seems like only half the story. Surely I want to sharpen the sides.

Thread: top feed and pumps
13/04/2015 19:25:38

why? It doesn't make any difference to steam raising whether you put it in under water or just let it fall through the steamspace

Thread: Taper turning
13/04/2015 19:20:20

ring up Mr Arrand, who makes loads of taper tooling, he will probably make you one. Won't be cheap, but will be top class. 01664 454566

Thread: Regulator
03/04/2015 17:43:43

2 off 5/16 holes is huge, you will get away with a lot less gives recommended speed for high pressure saturated steam, work it out from there.

Thread: How to machine a flywheel ?
31/03/2015 15:46:24

I just gripped it in the 4 jaw using external jaws, face, bore for crank. then bore a register into the rim and take a skim as far as you can on OD. Turn round and grip using register, clock to skimmed OD, turn OD and face other side. trying to do it off a mandrel is hard work, chatter and ringing as the rim is not well supported

Thread: Stainless steel
31/03/2015 15:37:04

Sharp tool with about 20 degrees top rake, I use High Speed Steel as it is sharper than carbide, reasonable depth of cut, reasonable feed rate. If you try to take a small cut at low feed it won't work. I've had really good results with tangential toolholder. Watch out for the long ribbons of swarf it will cut your hands to shreds.

Thread: Regulator
29/03/2015 17:31:20

Could John Baguley be persuaded to post drawing of his Tich regulator, save me dreaming up my own?

Thread: Height of your lathe
29/03/2015 16:12:40

I reckon cross slide handle should be level with your navel. To achieve this I mounted my last lathe (Colchester Chipmaster) on 6" solid concrete blocks. Put a bit of grout underneath to increase the surface contact area. Worked a treat, no rocking, why should it?

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