Member postings for David Littlewood

This may be so - but how many of us have machines which can actually take a 5C collet in its spindle?

David

John,

You can pass long work through an ER collet - provided the chuck is of the right type. The ones on a morse taper shank are (usually) solid, but the ones which screw on the spindle nose, or fit on a backplate, are (usually) capable of passing long work.

I have both types; the MT shank one is ideal for holding milling cutters in a milling machine, the others are ideal for use on a lathe.

I would certainly agree that the ER ones are more versatile (apart from the square/hex bit); I certainly use mine a lot more than the 5C ones.

David

Edited By David Littlewood on 08/05/2013 14:23:09

Chris,

I second Olly's recommendation to use EN24T; I have used it for quite a few parts, and it does machine well for a high tensile alloy steel. Noggin End Metals and Mallard Metals both suply it, among others.

David

You also have to bear in mind the possiblity that the bar you use to test runout could well not be perfectly round. Well, to be pedantic, it definitely won't be "perfectly" round, it's just a quetion of how far off it is. Generally speaking, silver steel and PGMS (precision ground mild steel) are both pretty good, ordinary mild steel may not be. For best certainty use a properly ground test bar, which should have a guaranteed specification of its roundness.

David

Edited By David Littlewood on 23/04/2013 23:00:56

Tony,

I don't recall seeing any counterbores specifically for BA sizes, though I have not searched for them very hard.

I would go along with Jeff's suggestion about the slot drills - though you need to make sure they are configured for plunge cutting. Four flute end mills generally are not; two flute slot drills and (most) three flute disposable cutters are. I find that many commercial counterbores are rather too large for the sizes they are marked for; metric ones give much too much space for the heads of capscrews, it just makes a gap for swarf. I find I get better results using the correct size of slot drill.

I bought a set of counterbores from Tracy Tools about 20 years ago which have served quite well in the smaller sizes; they work better than slot drills in doing couterbores in delicate items (such as O gauge coupling rods) as the pilot helps to stop the part bending under cutting forces. Don't know if they still do them. Bear in mind if the pilot is too small you can often pad it out with a bit of tubing for such delicate work; if it's too big you are stuck.

David

Edited By David Littlewood on 23/04/2013 22:55:32

Andy,

I have used a set of ER25 collets from Emco for over 25 years with complete satisfaction. Also, a few extra sizes of ER25 from Arc Euro Trade and a full set of Vertex ER32 collets from Chronos have proved totally satisfactory. You need to take care over the chuck you use; the Emco one is spot on, but some of the far East import lathe chucks have slightly high runout. This can be corrected with care.

ER collets are good for holding milling cutters, provided you tighten them fully; if you don't there is a risk that the cutter may walk out of the chuck and spoil the work. I've only done this once in 25 years, a lesson you don't forget. The ball bearing closer from Gloster tooling are reputed to make this much more reliable, I bought one a few weeks ago but have not tested it yet.

The huge advantage of ER collets is their versatility. Each collet has a closing range of 1.0 mm (0.5 mm in the smallest couple of sizes) so is good for gripping material as well as cutters (BMS in particular is often a few thou undersize) and if you have a complete set you can hold anything in the size range.

David

Edited By David Littlewood on 21/04/2013 23:24:31

Michael is quite right; these retainers are not strictly speaking adhesives. They have rather poor peel strength (at least they did when I tested them); they work by polymerising in the absence of oxygen to form a plastic similar to perspex, which forms a firm interference joint inside the shaft/hole gap. Even a couple of mm is enough to give a fierce grip in a small diameter hole.

One thing to check though is the temperature. As you will appreciate from the above description, the interference fit depends on the polymer formed on curing. This will melt above a certain temperature, and you shoud check the manufacturer's specification for details of this.

David

Neil,

Good point; I was guilty of being slightly tongue-in-cheek. It does not seem to be entirely clear exactly what the Act means by "privately". If it simply means "not for profit" then it seems to be redundant as "purposes which are not commercial" covers that. If you paid someone to do it for you, then surely they would be doing it for commercial purposes, and woud thus be infringing. Subsection 5(b) exempts acts done for research and does not include the "privately" bit. Sometimes it can be hard to fathom the subleties of parliamentary draughting, it seems to be designed to create work for lawyers.

David

Mark,

When you ask a question which involves legal issues, it is essential to specify where you live, as the laws may vary.

In the UK, the law on patents is covered by The Patents Act 1977. S 60 (5) provides a list of acts which will not be regarded as infringments of a patent, and item (a) applies to the case you raised:

(5) An act which, apart from this subsection, would constitute an infringement of a patent for an invention shall not do so if -

(a) it is done privately and for purposes which are not commercial;

You should be fine to make a version of a patented device at home for your own use. Note that both things must be true: the act is done privately and for purposes which are not commercial. However, I doubt you would get into trouble for showing it to your friends!

You can find the legislation (including all later amendments) at **LINK** if you are feeling the need to cure your insomnia.

David

David

Missed this one earlier. The problem with using salt solution to neutralise strong acid, in addition to the very slight* risk of chlorine generation, is that salt is not alkaline and will do nothing to neutralise the acid. For small quantities, sodium carbonate (washing soda) or even sodium bicarbonate (baking soda) is fine - though be careful not to add too quickly or it could start climbing out of the container. Avoid sodium hydroxide (caustic soda) as it is highly corrosive, extremely dangeroous to the eyes (worse than acid) and dissolving it is very highly exothermic (i.e. it gets very hot - will boil the water and spit).

I also strongly recommend you avoid using hydrochloric acid as a pickle; it is a solution of hydrogen chloride (a gas) in water, and unfortunately it gives off HCl gas when exposed. The rapidity with which this will rust your precious machinery and steel stocks is breathtaking. Sulphuric acid is fine in this respect as it is not volatile, though all the other precautions (acid to water, slowly, with careful stirring) apply.

If you are not used to handling strong acids, probably better stick to the citric acid.

* Acid and sodium chloride is unlikely to produce significant amounts of chlorine unless something else is present, but could give off HCl if heated. People have been killed by inadvertently mixing strong acid and hypochlorite bleach - very rapid Cl generation - but sodium hypochlorite is quite different from sodium chloride.

David

Edited By David Littlewood on 04/04/2013 11:41:42

Graham,

If the above was aimed at me, then I must strongly deprecate your comment, and its personal nature. In my opinion, clarity and certainty of expression is fundamental to any discussion which has any claim to be scientific and rational. If participants have different views as to what words mean, communication is hampered. Then unless the meaning of a word can be agreed, it is best avoided, and a non-contentious alternative should be used. I hate to think how many beginners have been confused by this particular example in the past.

David

Andrew,

Apologies, I obviously misremembered the source of the quote; I couldn't find it in my dictionary of quotations.

David

Well, if one uses a word in a way totally contrary to the way the other 99+% of the English-speaking world understand it, confusion is inevitable. There is a certain Teedledum/Tweedledee approach here.

David

Responding to Trevor's point about the torque produced by VFD-powered 3-phase motors, I believe that at low speeds the motor is operating at constant torque. At a certain point, somewhere in mid-range, the motor moves into constant power mode. Certainly I have always found the torque is perfectly adequate even at low speeds; though you do have to be careful not to operate too long at very low speeds, the system has a cut-out to protect against overheating.

And as for motor voltages, the great majority of modern 3-phase motors can be wired in delta or star configuration by a simple shift of links on the terminal block; the former works at 415 V, the latter at 220 V. Older motors may need you to dig out the star point to convert to 220 V, which is a lot more fiddly but you can find instructions on the web. Of course if you buy a kit this is all taken care of for you, and if you are not comfortable with mains electricity I would say this would be the way you should go.

David

A Google search on "age hardening of brass" threw up two previous discussions of this subject on this very site, I suggest you look for them. Both seemed to suggest that many grades of brass do age harden but some high-zinc grades might not. Never studied it myself, but I know copper age hardens, quite quickly too.

David

I'm with Paul on this one. When my 1/2 HP motor packed up 5 years ago I replaced it with a 1 HP 3-phase motor and VFD package from Newton Tesla, and I wouldn't go back. I set the pulleys to the top speed of the lower range (i.e. the external pair of pulleys on low, the ones inside the headstock on high) and I can't remember when I last needed to move the belts. The motor is a little more powerful than standard, but that means there is plenty of power at low speeds. The NT package comes with proper connectors, and the motor is the correct one to slot straight into the lathe's cradle with minimum fuss. It's quiet and smooth.

I liked it so much that I had no hesitation in fitting a VFD from the same source when I bought an M300 a couple of years later.

David

Stew,

The material you saw labelled "silver solder" is in no way equivalent to "real" silver solder as used for silver brazing at 600 deg C plus. It is just a lead free soft solder which has a tiny amount of silver added to give it the desired properties.

David

Well, I suppose that explains why they do supply fitted plugs. Pity really, it removes the possibility of a little Darwinism...

David

If you have trouble finding one, you can get them (at a price!) from Slater's Plastikard; they are the standard size for fixing Slater's wheels on to O gauge locos.

**LINK**

I'm sure you could find them cheaper somewhere else though.

David

Silver steel is not the only grade which can be hardened. You may find it worthwhile to phone one of the metal retailers who may know where to source a suitable hardenable grade in hexagon form. From past experience the guys at Mallard Metals and Noggin End Metals are both very approachable and can get stuff not normally stocked.

David