Member postings for Andrew Johnston

Philip,

It is not possible to harden 316 using heat treatment. You have to use cold working methods instead, which may not be practical for a shaft. See this link:

**LINK**

Regards,

Andrew

I was hoping for an insight into contact stress theory, and an overview of ball bearing theory would have been interesting.

Regards,

Andrew

Aw, go on, try us. If we're too dumb to understand so be it, but if we don't try we'll never know.

Andrew

Dean,

Ah, readily available, that's the catch. You may find the following link giving magnetic properties of materials useful, although it's a bit weak on remnance:

**LINK**

The material RM4550 is available from the following (search under nickel iron alloys), although I'll bet it is not cheap:

**LINK**

I assume that your application is DC or low frequency, in which case some silicon steel transformer laminations are probably as good as it is going to get. When I was looking for silicon steel a few years ago I failed to find any companies prepared to sell small quantities.

Regards,

Andrew

Edited By Andrew Johnston on 14/12/2012 11:41:05

Transformer laminations are normally silicon steel. The addition of silicon reduces the remnance of the steel, but does not eliminate it. If the steel had zero remanance then the B-H curve would go through zero in each direction and the area under it would be zero, which would imply zero hysteresis losses. Steel is actually a misnomer as the material contains almost no carbon.

So transformer laminations will be much better than mild steel or soft iron, but is not perfect.

Regards,

Andrew

Excellent phrase, made me smile anyway.

I've never bought anything from the 'new' Myford as I don't have a Myford lathe, but I have occasionally bought from RDG. I have always been satisfied with the items.

Regards,

Andrew

Normally I would agree with the above. For anything 'imperial' I reach for my father's copy (1943) first rather than mine (1992). However, I was recently looking for detailed dimensions of BSF full nuts, as I need to make some for my traction engines. Nothing in the older version, but my version has complete details, most odd.

Regards,

Andrew

I got my unit today; excellent service from Axminster, ordered yesterday morning and it came this afternoon. I'm in the countryside, so the post almost never comes before lunch!

I've measured the current consumption; 82µA running and 6µA off. Given that an el cheapo AAA cell probably has a capacity of around 300mAh you can work out the expected lifetime yourself.

Regards,

Andrew

Edited By Andrew Johnston on 07/12/2012 20:54:08

Oh dear, I'm being a complete idiot, I do have issue 4444 after all. Looks like it's off to the funny farm for me.

Idling around this evening I logged in for the first time to the digital editions. I looked first at issue 100 of MEW as I seem to be missing several issues around that time, although I definitely remember getting issue 100. I thought it might jog my memory in case there were some special articles which meant I'd put them on one side, or lent them to some-one. No bells rung though. Then I looked at 4444 on line; surprise, surprise I recognised some of the articles, and eventually found the magazine in the great pile on the floor. My only excuse is that I must have got it the best part of two weeks ago, and the last issue I actually read, just before this thread was started was issue 4443.

Ah well, at least I might be able to claim my pension early on the grounds of mental incapacity.

Andrew

I don't seem to have received issue 4444 yet, despite having a subscription. Have other people got their copies?

Regards,

Andrew

If you're just flattening the top of a boss why bother with a special tool, just use a normal milling cutter? In the picture the bosses on the small casting were cleaned up with a standard slot drill whereas the holes on the larger casting need a recess to provide a clean mating surface:

Regards,

Andrew

I have seen it, and I'm none the wiser. So either the reference isn't to me, or, more worryingly, I posted something which I've completely forgotten about.

I'd either file an oval gland by hand or use the CNC mill. If I was filing I'd do it by eye rather than bother with buttons.

Regards,

Andrew

Correct. For a three phase motor connected in delta there is, by definition, no neutral point. For a motor connected in star the star point is effectively the neutral. However, if the system is balanced, ie, each phase has the same impedance, voltage and hence current, the current into, or out of, the star point is zero. So no need for a physical wire. Small three phase motors are generally considered to be balanced loads.

I've just wired up my Britan lathe to the three phase supply in the workshop and there is no neutral connection, just three phases and earth. The main drive motor clearly runs in both delta and star configurations, but still no need for a neutral.

Regards,

Andrew

Couldn't resist it, that's spot on John - Andrew

Oeeeer, I think my rotary table is 90:1, ie, 4° per turn of the handle - Andrew

Blimey, I must be lucky, I'm surprised if I get more than 1 or 2 spam emails a week. Mind you my home email address looks like a collection of random letters to most people. However, my business email uses my name, at least in part, and I don't get very many on that either. May be I'm considered too poor to be worth spamming.

Both spam emails and 'phone calls seem to go in phases. I haven't had any annoying 'phone calls in the past week about PPI, solar energy or 'free' home insulation, but had 4 or 5 the week before. It's possible that telling them I live in a 15th floor flat, or a caravan, might have something to do with it.

Regards,

Andrew

Dave,

Thanks for putting me right on changing the collets; that'll teach me to wing it instead of reading the manual first.

Regards,

Andrew

I ordered online from IKEA as a 'guest', no registering hassle and no user IDs and passwords to forget. Delivery was £5 plus VAT. No brainer really as my nearest IKEA store is Milton Keynes, which is well over an hours drive away, and my one visit there wasn't a pleasant experience.

Regards,

Andrew

They'd better live up to expecations, because I've just ordered three of them! One for the lathe, one for the vertical mill and one for general use. The lathe does have an industrial low voltage (25V) light on it, but I gave up using it because it eats bulbs, and they're not cheap.

Andrew

Dave: I haven't counted up the studs, but it must be several dozen at 1/4" BSF and slightly fewer at 5/16" BSF. Fortunately I have both 1/4" and 5/16" collets. Changing the spindle collet yesterday seemed easy enough. Unscrew the nose piece, swap the collet and replace the nose piece. Clearly the more you screw the nose piece in the tighter the collet gets on closing. Presumably the idea is to have the collet just tight enough to grip the work, but no more or the closing fingers might get damaged?

Norman: As Dave says 8BA is no problem. I've also got a 5/16" (8mm) Coventry diehead for the Britan. Currently it has 4BA dies in it, but 8BA is readily available. You can even get new dies for the ME 40 tpi series. As an aside there was also a 3/8" (10mm) diehead, but there are far fewer dies available in this size, so presumably the 3/8" diehead was much less popular?

Neil/Ken: Yes I know, but it's still depressing. Mind you not only will my studs be better I'll have some fancy washers too with a nice chamfer on them instead of commercial stamped out washers.

Regards,

Andrew