Member postings for David Littlewood

Google is your friend.... **LINK** and **LINK**

David

Gary,

On the choice of collet chuck, be aware of this. A chuck on a morse taper shank will need to be held in with a drawbar (miling cutters do have a tendency to make cutters or chucks walk out of their locations*). The result of this is that there is no through bore, so you can only hold short lengths of material. The best ultimate position to work towards is this: a backplate fitting chuck for use on the lathe (such as **LINK**), and a morse taper (or R8, if that's what you end up with) chuck for the milling machine when you get one. Since the collets themselves are the expensive bit, this will give you the optimum utility for a moderate final outlay.

*This is why you should never use a drill chuck for milling. ER collets hold the cutters firmly enough to avoid this - but you must ensure you tighten them up properly.

David

Gary,

I would second Terry's advice, and add that the utility of the ER system is even greater than just holding milling cutters. You can hold material in a collet for turning; the advantages being that (a) it should give better concentricity than holding in a 3-jaw s/c chuck, and (b) as they grip the part all round, they are far less likely to cause damage as would the teeth of a chuck. For small-scale modelling work I use them almost exclusively.

David

Andrew,

Your view is not without some validity, but is somewhat overstated. There is no logic in the statement that development of the V-bombers "nearly bankrupted" the country, they were developed by private enterprise and I don't think their purchase cost would have been a major drain on the economy. True that high-level bombing soon became unacceptable (though it was the development of effective surface-to-air missiles which did that, but the Vulcan at least of the 3 V-bombers soon proved itself cabable of low-level missions.

I remember reading a story of how the US air force invited a Vulcan squadron (this must have been in the 60s or early 70s) to take part in its annual air defence exercise; the Vulcans, without telling the USAF, arrived over the US coast at a hundred feet or so and turned up at the air base quite undetected by the defence network. Mucho red faces of USAF air defence types. As the story went, they were not invited again.

But you are right; they may have been seen as necessary in their time, but I think we can all be glad they were never used for their original purpose. Some of the most bloody spectacular, impressive and memorable air displays I've ever seen though.

David

Edwin,

Try looking at these: **LINK**

No hit and miss AFAICS, but quite a decent range.

David

Kevin,

I agree with you that it is better not to rely on the saddle handwheel for applying accurate feeds; it is just too coarse. I also avoid using the topslide for parallel turning where possible; it is much too restricting to have to keep it parallel to the bed at all times. The best solution is to use power feed where possible, and where you need precise controllability a graduated handwheel on the leadscrew is ideal (see the one on the Super 7). I'm not sure whether it is feasible to put one on an ML4 as I've never seen one close-up.

If it isn't possible, then consider fitting a DRO to that axis, then the coarseness of feel of the saddle handwheel may become easier to live with.

David

Edited By David Littlewood on 08/10/2012 11:46:06

Jeff,

Thanks for the unwarranted sarcasm; I did in fact offer constructive suggestions, to which most of the rest of the discussion has only added refinements (except yours, which was frankly rather eccentric). The criticism of the design is perfectly valid and a relevant addition to the discussion. What's your problem?

David

Woka,

Not sure - I have an S7, which has a different (and much better designed) construction, but it looks as if someone has chopped off the spigot. If you remove the cross-slide you wil probably find that the remains of the spigot can be removed. Then you should be able to make a replacement which has the upstanding part a close sliding fit in the hole in the topslide.

Even with your mutilated set-up, it should be perfectly possible to fix the topslide firmly in place with the two locking bolts to allow you to machine a spigot.

The more I look at it, the more I find it hard to imagine what the designer was thinking of the day he designed that POS system on the ML7. If funds permit, one day you should consider replacing it with an S7 cross slide/topslide.

(ducks below parapet)

David

Edited By David Littlewood on 03/10/2012 22:28:44

Stuart,

Sometimes the only way to gauge small threads is to use a toolmakers' microscope; do you know anyone who has one?

David

On the subject of constant-width sections, it is worth noting that a 90 degree V-block will not always detect this deviation from roundness. For example, a 7-sided constant width section will show zero deviation in a 90 degree block as measured vertically above the V. (If you doubt this, those in the UK can try it with a 50p piece.) A similar false pass will apparently be recorded by shapes with 9, 15 or 17 undulations, though I haven't tried this.

There is in fact a British Standard setting out in great detail the tests required to establish roundness (BS 3730, 1987, if you are interested). You may need to use several V-blocks of different included angle to establish true roundness, though a block of 72 degrees will work for all symmetries up to and including 18.

There is an infinite family of constant-width shapes, of which the symmetrical examples are only special cases.

David

Chris,

Go to **LINK** and download the Bruce Engineering catalogue. On about page 70 (the pages are not numbered) you will see a 1/2" to 1 1/4" cylinder hone for about £15. Have one, works fine.

David

Edited By David Littlewood on 27/09/2012 23:10:59

Michael,

That in turn reminds me of the three prodessional men who travelled up to Scotland together for the first time. On crossing the border they saw several fields containing numbers of black sheep.

"Look" said the historian "it seems all the sheep in Scotland are black"

"No" said the engineer, "it only proves that some of the sheep in Scotland are black".

"Well, said the logician, " if we wish to state the position precisely, it only proves that not all the sheep in Scotland are [not black] on both sides".

David

Edited By David Littlewood on 27/09/2012 01:04:29

Dunc,

First, if you look at these masonry drills, even new ones, the included angle of the cutting edge is somewhere around 90 degrees or more, so will be much stronger than the edge of a metal cutting tool. Second - and this is a little more specualtive on my part - tungsten carbide tools are not pure WC, they are WC powder in a metal matrix; variations in the amount, composition and structure of the matrix will give a trade off between hardness and toughness, and I guess masonry bits tend to the latter. Third, even if blunted, the hammer action relies on battering the brick or whatever into powder and then scooping it out; I doubt if real sharpness is an essential for this.

They would be fairly poor at cutting metal without serious re-grinding; I'm sure they would scrape their way through, but it wouldn't be pretty. If you want to try, I suggest cast iron might be good, it quite likes a negative rake.

They are pretty good for getting through ceramic tiles - but don't forget to switch off the hammer action! Also, make a nick in the glaze to stop the point skidding around uncontrollably, or use a bit of masking tape for the same purpose.

David

Edited By David Littlewood on 23/09/2012 17:14:47

Surprising that someone who uses machinery but can't keep track of where his thumbs are has any left!

David

Jason,

Well, I wished I could have found one new, as I wanted one to have by each of two lathes! The one I referred to above which got sent back was actually a Mitutoyo one; the picture in the MSC web catalogue very clearly showed it to be an edge-button version not a face-button one, but when it arrived it was the latter. As it cost about a hundred quid, compared with the 10 or so for a cheap one, there was no reason to keep it.

I later found an old (=good) design Mitutoyo on eBay; slightly cosmetically imperfect but totally good in function. Agree with your point about the long-term value issue; buy the right stuff and the pleasure is experienced long after the credit card bill is forgotten.

It's the kind of issue that really gets my goat as I go through life - the number of times something is designed (or worse, redesigned) in a crap way just because some ignorant designer thought it looked nicer and no real user got to give any feedback (or it was ignored).

David

Edited By David Littlewood on 23/09/2012 13:07:09

Ergonomically, I much prefer a caliper with the buttons on the base of the slide; that way, they are exactly where you can most easily press them with your thumb. Putting them on the front means you have to move your thumb off the base. The early Mitotoyo calipers had this, and it was a retrograde step when they moved them to the front. My first caliper, a Mitutoyo, is the type I prefer; when I bought another one on the basis of a catalogue photo it didn't match the photo, and went back.

BTW, Ian - shops no longer have a choice about whether they take things back if you bought them online or by post - the Distance Selling Regulations oblige them to do it, within a certain time (IIRC, 14 days). All those (regrettably many) sellers who claim to make a charge for "restocking" are actually in brach of this law. They can require you to return the goods at your own expense though (unless they are defective)

David

Edited By David Littlewood on 20/09/2012 02:03:11

Jason,

I would add that in all the ones I have (not the ones in Martin's link, but from top-class named makers) the counterbore hole is also too big; there is a gap large enough for swarf. I suspect the sizes were standardised at a time when a lot of things were made to blacksmith standards on a pillar drill; with a mill used as a precision hole-maker (or a CNC mill of course) you can do much better fits and be sure the holes will match up. I generally find it more satisfactory to use drills and a slot drill to get a snug fit. You can get good location with a couple of dowel pins, but that swarf trap is too much.

Olaf,

I wouldn't worry too much about the true flat-bottomed bit (unless there is some special reason); for normal fixing use a standard slot drill will be fine.

David

Edited By David Littlewood on 13/09/2012 10:40:22

"Nice" fractions? Well, if you like them. Personally I bought a couple of sets of metric drills 25 or so years ago and now rarely use anything else, even when drilling tapping holes for imperial threads. And putting fractions on with a DRO is clearly not possible; I find myself reaching for the Zeus chart to see what 17/32" is in real numbers.

David

Hi Monk,

You could use stainless steel for the frames, but it's hugely more expensive and also hugely harder to machine; I suggest you would be better off with normal quality bright mild steel. You can buy frame steel from casting suppliers such as Reeves, or from the normal ME suppliers such as this one: **LINK**

I don't know enough about CNC to know if it is feasible to make wheels that way, but I suspect you would find it a whole lot easier to use castings, again from places like Reeves. The frames of most locos may be too big for your CNC setup; if you go for the manual method of machining them, then unless you have a big milling machine with DRO, you will need to mark out as shown in the books you referred to. The best coating for marking out IMO is a 10% solution of copper sulphate (easily obtainable on eBay) with about 1% of sulphuric acid (unfortunately it doesn't work at all well without the acid). Battery acid should work, but allow for the fact that it is already diluted somewhat. The copper coating, unlike most other methods of marking, will not come off with cutting oil.

David

Edited By David Littlewood on 10/09/2012 23:09:26

Bernard,

I think you have been a little unfortunate in the metal supplier you approached. I have found the chaps at Mallard Metal Packs, **LINK** and Noggin End Metals, **LINK** are both helpful and knowledgeable, and are often able to source specific grades of metal not in their normal catalogue.

David