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Member postings for Tim Stevens

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

Thread: Which suppliers are open for business?
08/04/2020 18:24:55

In the good old days, pre-WW2, Morris Motors was owned by William Morris. He then bought Wolseley, but kept it as a separate company in his personal ownership. Later he sold what was left of Wolseley to Morris Motors for a tidy sum.

So, it is clear (to me) that although two firms can be owned by the same chap (or several chaps) they still count as separate companies, but it can also be that a firm can become the property of a different firm even if both firms are owned by the same person.

Cheers, Tim

Thread: Guidelines for which steel to use for projects
02/04/2020 15:57:46

The answer is always going to be a compromise, so do bear that in mind. Work out the ideal stuff and you will find that:

the spec was changed 17 years ago

it is not readily available in the size or quantity you want,

but you can order a lorry load

with delivery in about 12 months

and you supply the crane to unload the lorry.

In practice, most model engineering designs are used for such a short time, under such small loads, etc, that unless you are building heart by-pass valves, or intergalactic rocket nozzles, the choice can be reduced to 'what can I get that size this week'.

But if you want a guide with a USA bias, try Machinery's Handbook. Added benefit - all sorts of other questions are also answered.

Cheers, Tim

Thread: Model of an epicyclic gear made by apprentices
02/04/2020 15:42:24

This is not the firm Allen which invented / patented/ introduced the hexagon socket drive and key - is it?


Thread: Problem with LED lights
02/04/2020 15:34:06

I have found that white LED lamps can show up the rusty colouration on steel. I suspect this is because the 'colour balance' of the LEDs is not exactly sunlight. The shine on the metalwork is just the same as it was, of course ...


Thread: Gear Cutting - Pressure angle.
01/04/2020 18:03:41

How few teeth? Well, as the gear gets smaller the shape of each tooth changes - the outside looks much the same but the sloping flanks become closer together. This weakens the tooth - there is simnply less metal there. Smaller still and the teeth can 'interlock' as the gear rotates, making a smooth drive impossible and promoting rapid wear.

It is the same with sprockets for roller chain - anything less than about 20 and you will suffer. Yes, chainsaws do it and that is why the chain and sprocket both need replacing about every tree (well, nearly).

Cheers, Tim

Thread: Inlaying silver in brass.
01/04/2020 17:13:11

PS It is useful, when hammering the wire into place, to do it on a firm solid surface, so the energy goes into the job and doesn't buckle the background. Secondly, don't use a hammer alone - use a punch with a smooth and slightly convex surface - rounded at the edges. A useful punch can be made from a coach bolt with a 'flat' filed in the middle of the dome, and then polished using emery, wet-&-dry, and finally chrome polish. If you can see your face in the surface that is shiny enough. You might need an assistant to hold the work against the support while you tap, tap, tap. Using a punch should avoid making half-moon marks around the surface.

And do a practice run first - copper wire will do for this.

Cheers, Tim

Thread: Digital Vernier gauge
01/04/2020 12:50:51

It might help if you could tell us what type of gauge. Never mind the fact that a digital vernier is a contradiction*, is it a depth gauge, a caliper, an indicator, or what?

* a vernier has two scales sliding against each other, and relies on the user identifying where the scales match. Digital, in this context, means an instrument giving a reading directly in figures, usually relying on an electonic counter and a finely divided internal scale.

Cheers, Tim

Thread: Inlaying silver in brass.
01/04/2020 12:18:27

Inlaying has 'always' been done by cutting a groove and hammering in a wire. Cut the groove so that the edges form a burr, and hammer the burr down onto the edges of a half-round wire. It is not 'engineering' in a modern sense, but it is certainly silvermithing. Gold inlay into silver is done just the same, as was silver into steel for posh armour.

Cheers, Tim
(the last apprentice of the Guild of Handicraft)

Thread: Fine Gauze
20/03/2020 23:04:10

DMB: No - the tubes used as internal tent-poles are made of fibreglass, and so are non-solderable and heat resistant. Just what you need to wrap a tube of gauze around for soldering. I make a distinction between fibreglass - a composite of resin and glass, and glass fibre - which has no resin holding the strands together.

Some types of greenhouse watering systems also use the same sort of fibreglass tubing.

Regards, Tim

Thread: Sanitizer
20/03/2020 15:52:05

No-one has suggested (or have they?) that if alcohol attacks the virus the best approach would be to take the alcohol internally. Single malt virus killer - sounds good to me.


Thread: Fine Gauze
20/03/2020 12:33:18

An alternative tube - unaffected by solder - is fibreglass - as used in the flexible tent poles which are threaded through slots in the tent.

Just a thought


Thread: Ideas to best hold blanks with out turning
17/03/2020 18:31:30

My only comment is about the aluminium backing.

As this is cut, the Al will tend (as it usually does) to stick to the cutting surface, building up a hard lump. This makes this surface a different shape, until the Al eventually drops off and the process starts again. But in the meantime it will cut the brass too, and you might not get teeth which mesh properly. It just seems an odd risk to take when removing burrs from the back of the gear is so simple.

There must be a way to do this without using Al, after all it was not discovered how to extract it until about 1850.

Cheers, Tim

PS: M$ is my favourite thread, too ...

Edited By Tim Stevens on 17/03/2020 18:32:37

Thread: Capillary gaps required for silver soldering.
17/03/2020 17:58:46

A simple experiment might help. Set up two small flat plates of your material upright on your soldering base so that one edge of each plate is touching the other, and there is a very small angle (1 degree) between the plates. Then apply your normal flux, heat the assemblage, and run your hard solder into the joint as you normally would. This will tell you how far into a narrow gap the solder will penetrate.

My money is on 'all the way' but others seem to have alternative ideas.

Regards, Tim

Thread: Cutting Parameters for Small Slotdrill
15/03/2020 19:42:49

Jason asks: Does the maker not give any indication ?

Jason, you clearly have never bought anything from e-bay.

My comment about the raised lettering is that it may be that the easiest way to get a plausible scale result is to use etching. With a laser printer to produce letters at the required size, but mirror-image, these can be ironed onto the clean flat metal. Then you add a surround created using varnish, or shellac in alcohol, etc, and an acid suitable for the metal in use. Some people prefer electrolytic methods, using a salt instead of acid and relying on elctricity to do the work. I'm sure a back issue covers this, but when ... ?

Regards, Tim

Thread: A free ride to hospital
13/03/2020 17:33:09

The answer, of course, is not to have a guard on the machine where dust can collect. Just in case this seems a good idea, remember that the hot sparks will then go straight into your eye.


Thread: What am i doing wrong
13/03/2020 17:27:15

A quick note about the ruler test for height of a cutting edge: The test will only give accurate results if the bar in the chuck is running true. If the chuck is worn (like they all are) this is not usually going to be the case, so to be sure, turn a small amount off the surface of the bar in the chuck so the ruler rests against bright new metal.

Cheers, Tim

Edited By Tim Stevens on 13/03/2020 17:28:03

Thread: Bending and shear force confusion....
13/03/2020 17:13:57

Can I throw in a minor comment? The device shown originally is clearly not a super-engineered product, but what might be called a cheapo press not intended for intense or industrial use. I suggest, then, that any attempt to 'improve' things by applying greater forces to parts that were only just strong enough to start with will cause a loud bang as something fails. My guess is that the cross-piece through which the screw passes is cast iron, and cast iron is not wonderfully strong in tension or bending. If it is cast aluminium much the same comments apply, but in that case the bang might not be quite so loud. I hope that these comments (along with what has already been said) will save a lot of wasted engineering effort.

Do let us know if any mods are made and how long the press then lasts - Regards, Tim

Thread: Fitting Chuck Jaws
28/02/2020 11:14:44

If you are dealing with rusty parts it would be an advantage to dismantle the chuck and give it a thorough clean. In normal chucks the front and back are held together by bolts - usually hex-socket headed - and there is nothing complex about the mechanism. Mark front and back before taking them apart so it all goes back exactly as it was. Once apart the mysteries of which jaw goes where will be obvious - but the main object is to allow for a thorough clean out. Not just rust but odd bits of swarf and crud. A good soak in paraffin (kerosene) will help, followed perhaps by a blast with a pressure washer and ten minutes on a warm stove to dry it all out. Then use (eg) graphite grease in the sliding surfaces as you reassemble, and fit the jaws in the order which you should now understand and perhaps, remember.

Hope this helps.

And PS - the time you need to swap jaws endways is with an independent chuck - where each jaw slides on its own and not as a set. Jaws for this type of chuck can be turned endways to change 'inside' jaws to 'outside' - but you can't do this with self centreing chucks. Exactly why will be clear when you have the bits in your hand.

Cheers, Tim

Thread: Copper Plating
27/02/2020 17:47:18

If you are plating with a copper electrode on one side and the workpiece on the other, the solution (of coppoer sulphate) will stay as it is during the process, so you can bottle it and use it next time. Using anything else (such as a paint brush) will have two effects - first the copper in the solution will become impure as metals from the brush etc are dissolved, so it won't work so well next time, and secondly, the plating will not be pure copper and so might not stick or look pretty.

Use distilled water (or de-ionised - eg from a dehumidifier) and avoid contacting the solution with anything metal (except pure copper) for best results. Do not, eg, use an old kitchen spoon to measure out the crystals; a plastic spoon is OK though.

Finally, do not use too high a voltage - best to use a charger or a torch battery, at 3 volts. 12v might look quicker but will it stick?

Cheers, Tim

Thread: ACDC Drives VFD
27/02/2020 17:24:53

Do remember in thinking about changes that as you alter the ratios to increase speed, you also reduce torque. Always.

Having said that, I wonder why you are having to help your existing system along, as with the reduction on a 1HP motor you have you should be able to tow tanks out of bogs, but slowly. It sounds as though you have a lot of friction somewhere. This is also a cause of squeaking V-belts - a common problem with old cars on cold mornings, as the alternator drive takes power to top up the battery but the belt is old, or slack, or usually both.

Using very low speed from a VFD does not just lead to lower torque than you might expect, it also reduces the cooling effect of any fan in the motor. So as well as poor torque you can get overheating, especially on jobs like yours which can go on and on for hours.

Regards, Tim


Edited By Tim Stevens on 27/02/2020 17:26:12

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