Member postings for David Littlewood

John,

Would you not be better off making the body of the chuck from scratch? You can use the same nut (which would be harder to make) and an M12 x 1.0 finishing tap would make getting a good finish on the holding thread easier. Turning the female taper for the collets need not be that tricky once you get the angle set on the topslide - a test piece might be worthwhile here - and the external thread for the nut is not critical to the accuracy.

One of the main points of using a collet chuck is the guarantee of concentricity; cutting the M12 x 1.0 thread (on any lathe) and then turning the taper on your own Unimat will give you the very best chance of concentricity.

As to material, I think you would find that FCMS would give you decades of use, for anything but the heaviest user.

David

Edited By David Littlewood on 19/08/2012 18:32:20

Dave,

For not that much more than £300 you could buy a 3-phase motor and a VFD, and you would find that was very much better than a 1-phase motor.

David

Good advice - I have found Rotagrip excellent at sourcing chuck jaws, and from a much wider range of chucks than that. You might find the price surprising though.

BTW, for anyone who wnats to search, the correct name of the maker is Pratt Burnerd; see **LINK**

David

If you are prepared to use slotted grub screws, these people have them down to 12 BA:

**LINK**

David

Alan,

On the few occasions I have needed to machine a large radius face, I have used co-ordinate turning. It involves taking a series of very small cuts at calculated depths, followed by smoothing with a fine file. I have an Excel spreadsheet for calculating the coordinates, and it can do parabolas as well as circles, I think it also does hyperbolae but these involve a bit more conceptual struggling to decide the parameters.

Sounds complicated, but in practice takes a small fraction of the time you would spend making an attachment and template unless you need to make lots the same size.

David

Neil,

Not when your tools have graduations in decimals (imperial or metric).

Miller,

Thanks.

David

Deltic,

You have to realise that, even if you launch a thread, you don't "own" it. Sometimes the debate raises points which, though not directly relevant to you, may be of help to others in a smilar position. Get over it.

David

Edited By David Littlewood on 16/08/2012 12:07:35

Neil,

All just confirms my view that metric is just so much easier! Personally I'd rather spend 10 minutes just converting the dimensions on the drawing before I start.

Len,

The American Tubal Cain - not heard of him, did he also write articles in ME?

David

Harold,

For really fine work - in my case, O gauge loco building - I find one of these mini-thin grooving and parting sets: **LINK** is the best thing I have used. Eye-wateringly expensive at normal catalogue price, but no-one pays those, you can get a good discount by entering a simple code (which I can't remember offhand!) but even better, they are on special offer at around half price about every other month in the sales flyers.

David

PS The sets are on page 523 - link seems to go to the previous page whatever I do.

Edited By David Littlewood on 16/08/2012 11:51:08

Andy,

Welcome to the forum.

I have not had any problem putting 10 mm tools in my Dickson holders on my S7. However, it is fair to say that the margin before the toolholder bottoms out is a hair's breadth in some cases.

Some thoughts which may (or may not!) help:

(1) First - and forgive me if this insults your intelligence, but you did say you were a beginner.... I assume from your question that you know how to adjust the tool height by moving the clamping nut on the holders, but have you checked that there is no trace of swarf at the base of the toolpost which stops the holder bedding down as far as it will go? I have had this happen to me before now.

(2) There can be some slight (fractions of a mm) variation in centre height between different examples of the same lathe. Measure yours, and also the height above the cross-slide and top-slide, you will find these are very useful reference figures to have noted down anyway (write them down on or in the instruction book if you have one). I'm not aware that there is any difference in the height over topslide between ML7 and S7, but I supppose it is possible.

(3) There is also a slight variation in the thickness of the bottom part of the Dickson holders I have from various sources, maybe 1/4 - 1/2 mm. Examine yours and see if some of them work.

(4) There is no reason why you should not take half a mm off the bottom of the tool shank; the indexable holders are AFAIK made of reasonably-machinable steel.

David

PS - One final gentle suggestion - it may be better, when you have a new question, to start a new thread rather than append your question to one which petered out 5 months ago. Makes it easier for people to see what you are asking about, for one thing; not everybody reads every thread.

Edited By David Littlewood on 16/08/2012 11:39:48

These people: **LINK** sell Tufnol sheet, though the thicknesses are 1, 2, 3 etc mm, so you might have to do a bit of re-calculation.

David

This book:

**LINK**

has a very useful guide to zapping NiCd batteries which appear dead; involves passing a very high current through them for a second to reform the crystal structure.

Li-ion batteries are totally different and need very specific management of their charge/discharge cycles; they can be terminally damaged if they are charged above about 4.2 V (from memory, do check!) or discharged below about 2.5 V (ditto). The above book has the correct figures, but it's not to hand.

David

Neil,

I agree, I was thinking in terms of a few years... My current No 4 has been in use for over 20 years, but it is no longer any use on brass and is getting a bit tired now, but still works OK on MS

David

A bit out of your price range, but the best parting tool I have used by a country mile:

**LINK**

If it's too much for you, well, might help convince some other readers!

David

Bob,

Two things that haven't been mentioned are the type of tool you are using and the depth of cut. For example, if you use a carbide tipped tool and try to take a very fine cut you maye get a poor result as there is a tendency for the tool tip to rub. I find I can get down to about half a thou before this starts happening, but if the tool is just slightly above centre height this will happen sooner - and this isn't as easy to spot by the centre pip method. See what happens with cuts at various depths; if it gets worse for deeper cuts then it is more likely to be a bearing issue.

You will also find a great resource for advice on Harrison lathes on the Yahoo Harrison lathe group: http://groups.yahoo.com/group/harrisonlathe/

David

Edited By David Littlewood on 15/08/2012 20:03:38

Just remember, if doing the finger test suggested by Ken, that the motors are coreless; having no core laminations, the thermal inertia is very low, so they can overheat to the point of destruction very quickly.

In general, permanent magnet motors are not killed by too many volts unless they go so fast as to cause mechanical failure; the no load speed rises until the back emf cancels the current flow. It is excessive current flow which kills them, and this is almost entirely dependent on the load. However, it is possible that a coreless motor could overheat while the motor is reaching no-load speed if you cycle it too frequently.

David

Edited By David Littlewood on 15/08/2012 20:05:41

Mike,

Thinking back to when I made my S50 - about 25 years ago - the con rod is tapered at both ends, fat in the middle, and is made leaving a small parallel section in the middle. Then working on it with a very fine file (6" No 4 Swiss Vallorbe, with handle, soaked in cutting oil) blend the centre section so you get a smooth curve. Very little needs to be taken off to get a lovely flowing curve.

How you do the taper depends on what you have. Best: taper turning attachment - you can use power feed and get the best good finish. Worst: set-over topslide (you can't use power feed, and it may not be long enough) closely followed with set-over tailstock (takes forever to get it back correctly). If you must turn between centres, far better to use a small boring head in the tailstock, with a small centre in place of the boring tool; you can then set it over to your heart's content without worrying about resetting the tailstock. Take light cuts and ensure the boring head does not rotate in the tailstock though.

David

Mike,

I believe you can get calipers which show fractions, but quite honestly I think it is a barking mad idea, you have little or no idea how close you are to spot on. I don't think any of us have any difficulty down to eighths, maybe sixteenths for those who use imperial all the time, but there can't be many people who can mentally convert 29/64 ths into decimal on the fly. My solution has always been to have a Zeus data booklet next to the machinery, the table at the front gives me all the dimensional assistence I need, and the laminated finish means they are virtually indestructible. Just take the ISO metric tapping drill sizes with a large dose of salt though.

The other approach would be to sit down before you start and pencil in the decimal equivalent of all the dimensions on the plans.

David

Sid,

If you only need it because of its accurate sizing, then you should consider using PGMS (precision ground mild steel). It is, here at least, considerably cheaper than silver steel; the latter has no advantages unless you need to harden it. Like Graham, I have never found silver steel too difficult to turn, but it does need more care than MS.

People sometimes use silver steel for things like axles in preference to PGMS because they think it is stiffer, but in its unhardened state this is untrue, both have the same Young's modulus, though silver steel has a higher UTS (ultimate tensile strength). I'm not sure what the position is for hardened and tempered silver steel, but then that is a different beast altogether and much less suitable when resilience is required.

If you do need to produce a hardened component, then you need to take into account the slight expansion which takes place on hardening. It's slight, from memory a few tenths for say a 1/4" piece, but enough to turn a perfect fit into a no-go. Tempering will reverse the increase slightly but far from completely.

Sorry if the UK terminology is not entirely right for you; I think Graham must be right about the air hardening grade of drill rod, but it's simply not a terminology which we see over here.

David

Edited By David Littlewood on 15/08/2012 12:14:58

A Google search on "drill rod" threw up this useful-looking reference as the first hit:

**LINK**

Perhaps you found it and it didn't answer your question, but it does at first sight seem to contain the details if you explore. Hint: click on the "Tool Steel Guide" link.

David

Edited By David Littlewood on 14/08/2012 19:11:37