When I was an apprentice, we used to bend 2" and 3" thin walled stainless tube filled with ROSIN which I believe is a product of Pine Tar. Once the tubes were bent on a hydraulic tube bender, a steel ball was 'hammered' down the tube by placing a slightly smaller ball or two behind it and shaking them down. Rosin can be found in musical instrument shops for treating violin bow strings. Once heated, it melts and flows like syrup, going hard when cold.

For smaller tubes, we used CERROBEND. A bit of a laugh to saw a teaspoon in half and join the two halves with a bit of cerrobend, and slip them into the mug on the tea trolley. Sit back and wait for the rude remarks !! Life were fun then.

What a 'blind' old set of bods we must be - does engineering send us prematurely sight impaired !!

Tracy tools do various sets of chasers - make sure you get the correct thread angle. Thread rounding etc may not be quite so important - what does the team think?

Look on E-bay for CERROBEND - I have seen it there sometimes

**LINK**

12 quid a kilo - seems cheap!

BobH

You may be interested in the attached photos, I am sure the owner of them would not mind me publishing them here. The new stays were placed here by a boiler manufacturer.

A really nice job !

BobH

I think the question was how are varifocals for model making? It may depend upon how much you pay for them. Mine do not cover the whole of the lower part of the lens and consequently 'straight' things are like a banana! I have just lashed out on some +2.5 safety specs for lathe and mill work, and use fixed focus for other workshop stuff. Enter w/shop, take off varifocals (as they are expensive) and use cheaper single focus (if they suit you).

Bob

Use a thread chaser, or make one from an old 3/8 BSF Tap?

You could try

Steam's Last Apprentice by Victor Penketh

or

Didcot Steam Apprentice (Working Lives) by Patrick Kelley

Have a look on Amazon

There is another, but I can't find it Think its called An Apprentice in Steam

I reccon the process could be good for making one off drilling jigs (bush the holes), milling wedges / fixtures etc. I saw on TV also, that they are developing metal deposition and ceramics, such that it could be possible to print electronic components.

Can you drill a hole thro the tube to provide an end of thread run-out ? - if you thread in reverse as Bazyle says, make sure the chuck doesn't come off.

I thought all engineering was BINARY - either it fits or it dosen't. Either it works or it doesn't !

Well Ian, 13/32 + could be 13/32 full and 13/32 - could be bare - "Simples!" - perhaps set the minimum fraction to be worked to - 32nds, 64ths, 128ths !!

Bob

So Ian, I guess there aren't any model loco drawings dimensioned in fractions, using the terms 'full' and 'bare' to indicate the fit required.

Bob

Looking at that mechanical/ digital mike, I wonder if any manufacturer has thought of adding this functionality to an electronic digital mike / caliper. Ie: readout in MM,inch, fraction,swg,etc etc. I guess the electronic wizzards on this forum could interface a std digital caliper to a 'buzz box' that could do just that.

There is the gauntlet, Anyone going to take up the challenge ??

Bob

Interested in John's comment - how do we know how accurate any measuring instrument is unless we have access to a standards room at the correct temperature. I guess most of us make sure that when the jaws are closed, the instrument reads zero. If the jaws can't be closed, then a standard piece (perhaps slip gauge etc) will be used, but how many of us test the accuracy along the measuring length ?

Personally, I like vernier calipers marked in both imperial and metric, although my 'fractional' vernier reading to 1/128ths" is a brain teaser. My cheapo digital caliper eats batteries, one every 6 months. My caliper with a geared dial is very readable, but only imperial.

It just depends upon the job in hand. Turning a metric piece on imperial equipment. It helps to have a dual scale or readout at the same time - a vernier (like a slide rule) lets you see what is comming up.

My Dad used to say when working out the stress in a bolt. If you use a slide rule, you could see the stress for a range of sizes by looking at the graduations. By comparison, using a calculator, you had to work it out for each bolt diameter.

Bob

I am suprised that a pair of calipers could cause such damage !!

Living in France, I listen to Radio 2 or 4 via the netbook and WiFi.

Bonjour Didier,

I hope your problem is resolved soon. Which department do you live in ? We are in Lot (46) and find it difficult to find small quantities of material in France at reasonable prices. Many UK suppliers will send material, but of course the postage can be a bit expensive. We would be interested if you know of some good vendors.

Bob Humphrey.

Just a thought - pink flux powder! My flux powder for silver solder is white, my pink stuff is for brazing (bronze rods) and melts at a much higher temperature which would be difficult with your torch on copper - pink and brazing may be OK on steel with your torch as steel is not such a good conductor of heat as copper.

It looks like the torch should have been big enough, did you have the torch too close to the joint. When you look at the torch flame, nearest to the nozzle there is a cone of blue gas. This area of the flame is 'cold' . Outside of this cone is the burnt gas which is 'hot', so the correct part of the flame to be using is probably about 5cm away from the nozzle. You are looking for about 750 deg C, and with suitable bricks will get this onto the joint. Just another tip, you said that the flat plate was placed onto a fire brick. It will take a lot of heat as you would have to heat the brick as well as the plate. Can you support the plate just 1cm above the brick? That way, all the heat will go to the joint. When I silver solder, I play the flame around the joint for some time bringing the whole area up towards the right temperature. You will see the flux melt and look like moulten glass. Gently put the silver solder rod in the flame to warm it up, but not melt and dip this into flux powder, do this several times to get the flux to stick to the rod. Now concentrate the flame onto just one area of the joint which should be at red heat and gently touch the silver solder into the flame, enough to melt a glob off the end of it and remove the solder from the flame. At the same time, move the flame around the joint. The silver solder should be flowing towards the flame - perhaps add a little more solder as you move around the joint.

It shouldn't take more than 2 mins to get your joint up to heat. Check what sort of flux you are using, because if it is for soft solder, your joint will be all black and no good.

Use the largest burner in the kit. I use propane for all my silver soldering and even use the small torches which screw onto the small gas canisters. Last week, I silver soldered some 1/4" brass lugs about 2" x 1" onto some copper tube 2.5" dia. using SilverFlo 55 - admittedly this stuff flows at 630 - 660 deg C. I used a smaller torch than yours and it took about 2 mins.

Copper EATS heat like nothing else, use your torch at maximum heat, a couple of fire bricks around the back and side of the joint, perhaps in a 'V' shape, so that the flame hits the front of the joint and licks around the back, reflected off the bricks.

Next time we hear from you, we want to hear 'Job done' Good luck.