Member postings for Marcus Bowman

I agree that knurling is a displacement operation and that flow plays an essential part. So we can't really say we are "cutting" a knurl. Calculations would be based around pitch and pitch circle diameter, and have their place, but only when calculating using PCD, as when calculating gear dimensions. It think speed of engagement and squeezing/crushing the depth is also essential, as is copious coolant and continuous cleaning/removal of slivers or swarf.

That being said, I am far from convinced that most combinations of knurls and workpiece diameters give really cleanly defined knurls on the work. I much prefer to CUT knurls. For me, the most convenient way depends on where the work is, and what the previous operation was. Sometimes that's in the lathe, but mostly it is on the CNC mill, where all manner of patterns are easily achievable.

I have sets of good quality knurls in two-wheel squeeze-type holders (as in the illustration in a previous post), and they generally work well. Narrow knurls do tend to have the disadvantage that a greater amount of sideways traverse is required for a given breadth of knurling, so it is more likely that the knurl will tend to wander a little, producing a slightly drunken finish. Any slight out-of-square alignment of the arms or the tool tends to make that worse.

Marcus

Sounds like the well-established electtronic leadscrew project (ELS):

**LINK**

for which there is a large Yahoo group.

There is also a version based around an Arduino; and there are youTube videos of that.

No-one has mentioned decent dust extraction as being a solution to most of the problems of dust and debris. A powerful extractor designed for wood dust transforms the experience by removing much (but not quite all) of the dust. The challenge is in arranging the nozzel near enought eh surface of the work, and making it traverse with the toolpost/carriage. I use an 2HP Axminster unit which operates on the "vacuum" principle. I have also used an earlier unit based on lower suction at the nozzle, but intaking larger volumes of air. The vacuum does the job for my kind of work, but must have a small nozzle positioned close to the work surface. That just leaves a bit of dust, which, while requiring clean up is not a great problem. Cleaning the bed of the usual oily film before turning wood is essential. Cleanu up of chuck etc is important, but no worse than when turning cast iron etc.

The comments on speed etc are valid, especially for small diameter work.

A lathe is a lathe, and I never could really understand how a woodturner could claim a wood lathe was better for tunring wood. To me (and I own a wood turning lathe too) the engineer's lathe has proper precise control of carriage and cross-slide, meaning one can turn wood precisely parallel and to size. Sure; it shrinks and moves later, but that's the wood, not the lathe. My wood lathe says under the bench, out of the way.

Boxford made two wood turning tool rests(short one and long one) to fit the old bench lathes (AUD, BUD etc) but ther are designed to fit the old-style rest-holding arrangements which use a tapered plug. It is easy to make a simple adapter to allow those rests to fit onto a plain surface or a tee slot etc. I suggest second-hand dealers (see G & M Tools, for example). It is also relatively easy to adapt other rests, and I often use a rest from a Record wood lathe to give me an extended rest which sits out a distance from the normal rest position, for larger jobs.

One other word of caution. It is worth pointing out the dangers of wood dust from some species of trees, as well as the general danger to the respiratory system from small wood dust particles. I have found this is not to be underestimated. The same is true for other materials, of course, but the species-related dangers are both real and well documented. Real woodworkers cheerfully ignore dust masks, goggles and ear muffs - but they are all dead, blind or deaf, so I guess they knew best.

Marcus

Calor bottles are paid for by a deposit, but the amount you get back reduces sharply as time goes on. After 3 years there is no residual return value. No problem filling any Calor bottle though. I've never been asked for ID or proof of purchase.

Marcus

Or there's Hobby Weld, who sell bottles and gas. One payment for the bottle, then you just pay for the refill each time. Argon; Argon-CO2 mix; oxygen; etc. Lots of stockists.

Marcus

Didn't BSA own Triumph at that time, which would technically make both engines BSA.

It was a great programme, although stretched out a bit. But it held the interest of myself and my 25 year old daughter who still remembers, vividly, being taken to a real Wall of Death when she was around 5 years old (at Flook airfield, at the Cumbria Steam rally). I recall being taken to a Wall of Death at a visiting fair, by my Dad when I was in my early teens. Unforgettable.

And yes; the cyclist's performance was most impressive.

Marcus

Ok. If the workpiece is flat, and mounted on a faceplate, you could use a vee tool attached to the vertical slide, but swivel the slide for the angled strokes. You could also use a spindle and an engraving tool (or something like a Dremel or Proxxon drill as the spindle).

For curved arabic figures, I wonder if you could use the same principle as a taper turning attachment, where both the cross-slide and vertical slide are freed from their feedscrews, and follow the guidance of a template, rather like an engraving machine (but turned through 90 degrees so that the template is vertical to match the vertical face of the faceplate. That would require a pointer attached to the vertical slide, aligned with the tool or spindle.

I tend to think an engraving machine (commercial or home-made) would be more efficient. That has the additional benefit that the template can be larger than the engraved numeral, so errors are reduced.

If the bands are already formed, I'm not sure I can see an easy way to do this in the lathe for the arabic numerals.

This is an interesting problem!

Marcus

I suspect that this is the same demographic for a wide range of hobby interests. It certainly matches several other areas of my own interests. Same grey hair (or none...)

Marcus

To quote Ajohnw:

To be honest I am surprised these magazines have not gone entirely web based even allowing single editions to be purchased.

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That would be the least acceptable format, for me. I spend a lot of time at the computer, but I am about to cancel the only web-delivered engineering magazine to which I subscribe. Web delivery just cannot compete with print. I can read a printed magazine over my meal, or in bed, or take it to the workshop, and I can delve into a huge collection of back issues, but I have found I hate reading technical magazines only on-screen. That came as a surprise to me, but there it is. Print is still king, for me.

Marcus

I have not engraved the bands for that clock, but have done some other dials, including dials like lathe feedscrew dials, which are orientated the same way, and I am familiar with the Merlin clock project. What's your specific question?

I have also dome some etching, although if I was making the bands I would engrave them by choice, as I think this gives a crisper finish to the sides and corners.

I would not make the bands the way that process is described in the book (page 50) but would either make the band from a strip and turn it, or, for preference, turn the band out of tube. I'm not sure if there is a convenient size of tube, but that would be the easiest way. Without removing the tube from the chuck, I would transfer the chuck to the CNC mill. Sorry if that's not your cup of tea, but it is the easiest way for me. That allows the engraving to follow the surface of the band, round the bend, so to speak. I have engraved plain flat dials mounted on a faceplate in the chuck, using a vee tool, but even if the bands remained in the chuck on the lathe, the problem would be the diagonal movements. Not impossible, I think, but very tricky to co-ordinate.

I believe a conventional manual engraving machine can engrave around a band, without much trouble, but I have no direct experience of that.

Marcus

Picking up the points by Harry and Daniel, perhaps there is another aspect of all of this we should perhaps think about.

When you know something, or you have developed a skill, continued practice takes you through a cycle where you begin as a beginner and are a bit lost. Then you get into it a bit and find you can see what this new world is all about. Then you begin to increase your skills and knowledge, until one day you discover that, in the case of, say, a model engineer, you have the confidence to be able to tackle most things in the workshop (I didn't say anything about the standard of the result...).

You begin to develop insights, and a deeper understanding until, finally, you become a Zen master.

Without the detail, this roughly follows a well-known description of the learning process.

But I would say that at each stage ME, MEW and EIM are a crucial aid to learning.

The small dissatisfactions with the magazines may simply be a reflection of the feeling that you are having to look down, from the Zen position, and see little new or challenging. There are, though, those occasional nuggets which provide a different view of this world, and introduce some new knowledge or techniques. For there is no Zen, really, just a continued journey.

Oh; and it is accepted practice for those who achieve enlightenment (at any level of the process) to return their knowledge to those who might benefit from it. None of us know, or will ever know, everything, and we all benefit from the knowledge and skills of others. For me, the Master in the early days was GH Thomas, and there have been two or three others over the course of many years. I have learned a lot from them; and would not have known any of it if they had not shared it in the magazines.

I said earlier, as did others, that I had been reading old copies of ME form the halcyon days of the 30s to 60s. Halcyon? Actually, no; I really don't think so. So much has changed that most of what is written in those early volumes seems somewhat lacking compared to what we have seen in, say, the last 5 years of current magazines. The technology has changed; the equipment in a typical workshop has changed dramatically; and the standard of today's average and best quality models is light years ahead of what was going on then.

All of that takes us much, much further and makes us much more capable. And it was all because of the magazines. So; while I might be disappointed in some of the content, some of the months, I know that over a period of time I will be able to look back and be satisfied that I learned something. In fact I will be glad. So I won't be failing to renew my subs.

Marcus

There are some interesting thoughts here...

Like J I too have been wading through a huge collection of early MEs, from the late 30s to the early 60s. I received all the copies after that, as a subscriber. I have every MEW, as a subscriber, and I have all the EIMs too. I also used to subscribe to Don Young's much missed Locomotives Large and Small which ran some absolutely excellent constructional series, all with full good quality drawings.

The UK has the world's most highly developed magazine market, and I too am amazed at the content of some magazines. There is a problem, though, both for the readers and for the editors. I believe the long-term reader of almost any magazine will meet the same problems.

1. The content does repeat itself, with the same topics being repeated at intervals, and, in many cases, with old articles being reprinted.

2. As readers, we change over the course of a lifetime's subscription.

We can see the same phenomena in television and radio; and in most of the media in fact. TV channels run the same old repeats endlessly, and tackle the same basic topics time after time, because they are short of good content. I got bored of most of it a long time ago.

Problem 1 is a reflection of the plain fact that there is a high churn factor, with many subscribers being new readers, new to the hobby. Magazines need those new subscribers just to survive. But it does mean there is an unceasing demand for articles for beginners. It also means the same topics can be revisited at intervals. The challenge is to present those topics in new ways, and to avoid boring the older more experienced readers. That's a tricky challenge, and I'm not sure there is really an answer to it. It does depend to a large extent on the skill of the contributors, and on the editor winkling out interesting contributions from those who might have something appealing to say.

Problem 2 is an inevitable consequence of our own experience, our increasing skills and changing understanding of what the hobby means to us. Given enough time, it seems inevitable that we find less that appeals in any magazine. And yet, we live in interesting times, with advances in technology and new accessible ways of doing things, so there is always something to learn.

It's interesting looking at the output from the current fad - the Maker movement. I subscribe to some of the electronic newsletters and websites which proudly proclaim themselves as being in the vanguard of this new movement. What's depressing is that although there is some really smart computer programming going on, and some tolerable electronics, the standard of 99% of constructed items is very poor. None of these people have ever heard of ME, MEW or EIM. I do wonder, though, if the long-term trend will be for Model Engineering to be subsumed within the Maker movement, as interest in steam railways gently declines.

There is, too, the strong trend, common to many other constructional hobbies, to move towards ready-made items or to assembly of substantially pre-made sub-assemblies. That approach has almost completely taken over in aeromodelling and has made significant inroads in model boats. Of what interest would that approach be to those of us who have been in Model Engineering for a long time?

I don't think there are any easy answers. In fact, I don't think there are any easy questions about this topic. And it is too easy to say that if you don't like what you read in the magazines you should write an article yourself. Still; I do think it would be a shame if the more experienced folks disengaged form the model engineering magazines, because they are an important part of the overall infrastructure which supports model engineering.

It's interesting that this website and forums are part of the magazines' efforts to promote themselves by helping us to be an online community. I think it's a very valuable thing. Given that one can now find a huge amount of ME-related and workshop-related user content on sites like youTube etc, I do hope the printed magazines can survive as part of the mix. I subscribe to a digital-only version of another magazine from far away, and I must say I hate reading only on the screen. I prefer the physical copy I can read anywhere. The other valuable thing about the magazine is that the content is vetted before acceptance, unlike some of the rubbish on youTube and other websites, much of which is either boring or just plain wrong.

I think that's more than my tuppence-worth...

Marcus

Buy a ready-made 2MT or 3MT taper with a large diameter blank end. Drill it right through along its axis, with a decent hole (maybe 10mm diameter). Get a good Jacobs chuck and turn an arbor to a sliding fit in the hole, and with a taper on the front to suit the chuck. Now you have a sliding, guided, version of Simon's method. Hand-hold tightly as you feed the tap into the work, then you can continue that way, forward and reverse in stages, or leave the lathe chuck stationary and turn the tailstock-mounted chuck by hand. Works a treat. Wouldn't be without mine. There's a photo in a recent ME. Photos also on page 59 of the Crowwood Screwcutting book. I can post a photo if you need one.

There is also a popular ready-made item which consists of a small chuck and body on a sliding bar which can be gripped in a chuck in a tailstock or drilling machine. Unfortunately, the range of grippable sizes is small, and the body is smaller than the body of a Jacobs chuck, so its not as easy to grip or turn.

Hemingway also sell a nice kit for a floating reamer holder and that can be adapted for taps. I made one and although it is a substantial item it does what it claims, and copes with minor axial misalignment, preserving the tap.

Marcus

Yes; ground thread HSS Dormer E500 series taps get my vote, but be prepared for severe financial pain in the larger sizes.

On a rainy day, if you are not using them, you can pull them out at tea time and just wonder at their beauty.

Above M10, I would suggest "progressive" "geometric" taps like the Dormer E105 series, but they are even more expensive. They make tapping large diameter threads a very low torque process.

I have quite a few Presto taps, bought locally many years ago. Again, they are ground thread HSS.

For less frequently used imperial, ME and MME sizes I have found Tracy Tools taps pretty good.

Sadly; despite what we all would wish, quality costs. But it can be a good investment.

One other thing: in general, I would recommend Trefolex tapping compound. In fact I don't think I have tapped a hole without it in over 50 years. Eases the process, lowers the effort, and protects the tap too.

It's wet here this morning; and its nearly tea break time; so I'm off to polish the contents of the tap drawer with a soft cloth. I think of it as cherishing my investments...

Marcus

Interestingly, Whitworth is still a commonly used threadform for threads in cast iron, because of its relatively coarse pitch compared to its diameter; and because of its nicely rounded root and crest profile which means there are no sharp corners to act as stress risers, and no sharp vee points to crumble. Whitworth is still used in the metric zone for that specific purpose. Compared to, say, M6 x 1, 1/4 Whitworth is 20TPI and has a pitch of 1.27mm, so it is significantly more coarse than the nearest readily available ISO metric thread. 5/16 Whitworth has a pitch of 1.41mm which is greater than an M8 x 1.25 thread. If you prefer to stay with metric, on the basis that the taps will be more useful for other jobs, I would be inclined to choose M8 x 1.25 instead of M6 x 1 in cast iron. It probably depends on the amount of metal left around the threaded hole, because too little leaves the uncomfortable prospect of cracks in the main casting; so M8 might be too large for your tailstock.

Marcus

Assuming this is a 26mm x 3mm pitch 30 degree Metric trapezoidal thread, 26mm is "second preference" from BS 5346:1976.

The basic pitch diameter should be 24.500mm

Fundamental deviation is zero for the internal thread

Other dimensions depend on the class of fit, but ....

On a thread of this diameter, the easiest way to cut the nut is to use a full-form carbide threading tip and use the existing screw as the gauge. That way you don't need to worry too much about measuring to achieve a particular the class of fit. If you are really picky, you will need a proper thread plug gauge (jolly expensive, but the proper way to do the job).

I'm not sure if that helps, but the full-form tip will certainly allow you to do the job accurately.

Marcus

Les, you are of course correct. Mea culpa. 30M/min is more realistic, and what I thought I was typing....

So; for a 60mm diameter and an HSS tool the speed should be around 160rpm, and for carbide perhaps 300 to 500rpm. And hot chips.

Marcus

Use a watchmaker/jeweller's loupe or a microscope to examine the tip. That will soon tell you if it is blunt. Chipping or ridges along the tip will indicate wear, and a build up of material behind the cutting edge will also produce a rotten finish and a poor cutting action. Normal HSS cutting speed would be about 30M/s, so a carbide tip will work best at 2 to 3 times that speed. Cut depth will vary according to the design of the tip, but 0.2 is fine, and 0.5mm might be ok, but might also be a bit on the deep side. If you took twice as many cuts at 0.25mm depth you might find the tip liked it better, lasted longer, and gave you a better finish. You need to experiment a bit, I think. There is a sweet spot where the combination of speed, feed and depth of cut wqork well (a small range, actually).

Carbide tips don't last forever, though, so I would examine it closely first.

Marcus

Thanks, Chris. That echoes other statements I have seen about not needing to balance wheels of 8 inches or less. Interestingly, the three weights on the hub which was fitted to the machine were not at 120 degrees, and I assumed that was because the positions had been altered to bring the assembly into balance. The performance of the wheel suggested that was not the case, and that the wheel assembly was out of balance. I shall try the 120 degree approach, with confidence.

Marcus

I have a 540 and the manuals (skinny things, but useful for their purpose). The lubrication is listed as:

Propulsion - Mobil Vacuoline 1405 (now VACTRA 1, viscosity 32)

Oil nipples - Mobil Vacuoline 1409 (now VACTRA 2, viscosity 68

Spindle (Note: Plain bearing spindle) - Mobil Velocite 6 (equivalent is ISO 10, but I have never used that). Mix, as stated on the wheel guard, is 50% Velocite 6 and 50% kerosene. J&S can still supply this mixture (or could a few years ago), but it is easy enough to mix. I think the kerosense just thins the oil. That's a different mix to David's machine, but perhaps the difference is in the viscosity of the grade of oil.

I have just fitted a new grinding wheel and need to balance it. I need to know the slope of the taper in the wheel hub, so that I can make a balancing mandrel. Does anyone know the actual figure?

I would also like to know why there are three balance weights on each of my hubs, instead of two, The J&S manual only mentions two, and gives the simple procedure for balancing using two weights. I feel sure there is some logic behind three weights, but need to know how they are used to balance the wheel, in a practical procedure.

Marcus