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Member postings for Marcus Bowman

Here is a list of all the postings Marcus Bowman has made in our forums. Click on a thread name to jump to the thread.

Thread: Fusee Turning and Groove Cutting on my MYFORD
10/06/2018 23:05:15

How about using a milling spindle mounted horizontally on centre height, and a ball end mill. That way, you should be able to use your taper cutting method and template and achieve constant depth while 'screwcutting' using a spindle-mounted handle to turn the spindle and gearing slowly enough to suit the end mill.


Thread: Jones .605 Glow engine
10/06/2018 23:00:15

Lovely thing.

I particularly like the colour of the anodizing on the fins.


Thread: Aldi bandsaw
10/06/2018 22:57:48

One possible factor you might need to consider is blade speed.


Thread: small drill adaptor
12/05/2018 22:52:29

I have made several collet chucks based on the commercial Dremel closing nut, which is cheap to buy, and a home cut taper for the collets, with closing thread for the cap. Works a treat. The collet chucks are integral with shafts on accessories for a grinder, to allow me to hold tiny shafts, drills, etc.

One often quoted size for the Dremel nose thread is 9/32 x 40TPI which is an ME thread size. I have seen that thread spec quoted by a Dremel staff member.


Thread: Aluminium Car Bodywork
12/05/2018 22:27:32

+1 for the Lazze link. Search youTube for Lazzemetalshaping. Good stuff.

Also try Ron Covell, at Covell sells DVDs but there is also lots of information in his youTube videos.

I bought several pieces of equipment as a result of seeing the videos of both gentlemen (not from them, and not at the prices they suggest, either.)


Thread: Spiralux Drill Grinding Attachment
10/05/2018 20:52:40

One of the problems in using the side of the wheel is that frequent dressing thins the wheel. It is also a touch awkward to do the dressing on the side. Opinions differ, but I think it is important to dress wheels to keep them cutting freely. I have a little home-made accessory (effectively a small rest) which sits in the drill sharpening jig in place of a drill, and it allows me to quickly dress the face of my cup wheel.

I agree that it should not be necessary to press hard when grinding a drill. The heat is unlikely to damage a HSS drill, but if the grade of wheel is correct, it should grind without generating a lot of heat. If the wheel is too hard a grade, it will not wear, but will clog (sparkly bits of metal embedded in the wheel), and then it will not cut terribly well, but will generate heat as it rubs instead of cutting.


Thread: Picador Type Drill Grinding Jig Modifications
09/05/2018 23:14:12

First, I have a set of original Picador instructions, if anyone needs those. I have the original device, which I bought some 40+ years ago, and it works very well indeed. The instructions are peculiar to the Picador, and the projection of the drill bit beyond the front of the Picador is very different from other makes.That's because the geometry underpinning the jig is different from the Reliance-type jigs. So if you slavishly follow the Picador instructions with a Reliance-type jig, you will not get the intended result.

Secondly, my own opinion is that one should not grind on the side of the normal type 1 wheel which is found on most basic grinders, because the working face of a type 1 wheel is the front, curved, face. Yes; I know most people use the side, and that's what's shown in most drill jig manufacturers' instructions. I don't wish to start the usual argument, so I will leave it at that. My point is that the drill bit moves very little during its swing. If the drill jig was swung through 90 degrees, so that the drill lip sat horizontal, the drill could be sharpened against the curved face of a wheel. Some jigs are designed to do just that. I have a flat-faced type 6 'cup' wheel with a narrow face (8mm or so), on my grinder, so I use that, with the jig orientated in the 'normal' way, with its foot on the bench. I have a grinder and Picador set up permanently for sharpening drills. Each to his own.

Picador is Picador, and there is no real Picador-type, as the geometry of other makes varies either slightly or a lot, despite what are, at first glance, similar looking styles.

Picador made, I think, 3 sizes of jig. I have never seen the large one, which sharpens drills larger than 1/2 inch, if I remember correctly.

There are lots of other good drill sharpeners out there, of entirely different design, and I have a substantial collection of them. The geometry of the sharpened drill bit is similar, in the good ones, but the means of arriving at that geometry sometimes looks radically different. I understand the more recent Far Eastern pattern copies are not of the Picador, but are more like the Reliance, and they contain a built-in incorrect angle in the base unit. Graham Meek's article sorts that quite elegantly.


Thread: 1831
11/04/2018 07:48:55

I have read the original articles, and have the research material, but I am puzzled by the exact detail of the roof-mounted cooling arrangement. The published drawings for the model seem to me to represent this incorrectly, or at least too simplistically for my taste. Do you know of any really good photos or drawings which show full detail of the coolers?

Thread: John Wilding Elegant Scroll Skeleton Clock
18/02/2018 10:00:39
Posted by Michael Gilligan on 18/02/2018 09:30:08:

Blued pivot steel is a raw material, from which things are made

... It is not intended to be used 'as-is'

Yes; but my objection is that it is widely recommended for use in the as-supplied condition when making lantern pinions. If the surface is polished, that reduces the diameter, which then means the specified matching drilling diameter is wrong. Lantern pinions have merits of their own, but, when used instead of cut gears, the blued pivot steel is used as a convenience, so one would expect the drilling diameters to be correct for the finished diameter of the rod. That diameter is variable, if the rod is polished or turned.

More modern materials may be more expensive, but are dimensionally more accurate, and have a surface finish which means they can be used as-is. They are also harder than pivot steel. I guess pivot steel was the most convenient workable hard material 100+ years ago, but I am inclined to move with the times, except when restoration demands the use of age-appropriate materials.


18/02/2018 09:47:04
Posted by John Wallett on 18/02/2018 09:02:30:

the bit I am stuck on is fitting the strike components there is no mention in the book I have of how to fit them?

Does your edition have Fig 114 showing the bracket in which the hammer is to be pivotted? The bracket is to be fixed to the front plate with 2 screws. The 3 sections of the bracket can be pressed together or soldered.

The trip pin on the minute wheel should be approximately 4mm (5/32" in from the edne of the wheel, andf aligned with the minute hand. Make the lifting piece over length, then trim it so that release occurs exactly on the hour. I would take care to allow enough material to remain so that the arm can be given a final polish but still release on the hour. Longcase clocks often have bent pins to compensate for wear...

Fig 116 should show dimensions of the lifting pin. The pin is held on the shaft using an M1.8 x 0.35 (10BA) screw, bearing in a flat on the arbor (also shown in fig 116).

The tail of the hammer arm rests against the stop block on the bracket (shown on the un-numbered fig. entitled 'bracket components' and shown in the photograph Fig 115a. I am guessing that photo may have been a later addition, as it shows the assembled parts. Fig 115 itself shows the Parts of the "one-at-the-hour" striking gear.


Thread: BSB vs Cycle Threads
11/02/2018 09:14:03

As a motorcycle enthusiast, I have had many British bikes,and I certainly agree about the lack of sympathy in any restorer who attempts to convert British threads to metric simply to avoid finding or making a proper replacement Whitworth or BSF thread. Very nasty.

BSF threads are the same threadform as Whitworth threads but have finer pitches. BSF threads are specified in the same British Standards document as BSW threads, as the fine-pitch version of the Whitworth series. Hence the term 'Whitform' which covers all the thread series which have the same thread outline (55 degrees, rounded crests, tolerance classes, etc). You are right: 1/4inch BFS has 26tpi, whereas 1/4inch BSW has 20tpi. BSF extends the Whitform series by providing finer pitches for the corresponding diameters, compared to BSW.

I always felt the BSF fasteners where a more elegant thread series than the visually coarse BSW bolts. But that's just me. BSW is probably more appropriate in aluminium or cast iron, while BSF would be my preferred option for steel.


11/02/2018 07:37:57

Yes; the real world often deviates from tight standards, for practical reasons. It seems to be common practice in the USA to truncate the crests of the Whitworth threadform, presumably to remove the need to accurately form the crests of the male threads. That removes the problem of interference between Whitform crests and metric/UN roots, British Standards defines the dimensions of truncated Whitworth threads, saying that 'the rounded crests at the major diameter of the external thread and at the minor diameter of the internal thread [are] removed at their junctions with the flanks'. I did read somewhere that the original reason for truncating the Whitworth crests was because the standard of gauge-making in the USA, in the early days, lagged behind the accuracy of British gauge-making, so truncating the crests removed that problem from manufacturers. Truncating certainly makes a lot of sense. The clearance between mating threads depends on the tolerance class of thread (class of fit) but most commonly available threads are of the 'normal' class i.e. the sloppiest fit, so its no surprise that some 55 and 60 degree threads of the same pitch can be mixed. It's a bit like mixing BSW and BSCycle if they both have have 26tpi.


Thread: Scaling up
11/02/2018 07:16:26

There is an error in my last post, and I can't see how to edit it (logged out, then back in, and as noted by others this removes the chance to edit my post).

The area of a circle is pi x (radius squared). Swept volume = 3.14 x r x r x stroke. So scaling dimensions by 1.5 scales volume by 1.5 x 1.5 x 1.5 (one for each occurrence of radius and one for the stroke).

Given that the boiler volume scales in the same way (and I don't know if that's the best way to scale a boiler, fire grate etc), the cylinder and boiler volumes might still roughly correspond. Clive's answer is still the most practical, I think.


10/02/2018 20:41:20

Clive's answer makes good practical sense. But if you are scaling the bore, will you not also be scaling the crank throw, along with all the other dimensions? In that case, the swept volume will change as you scale the bore. It will change again if you scale the crank throw. Swept volume = 3.14 x diameter x stroke (or throw), so scaling by 1.5 multiplies the swept volume by 1.5 x 1.5 = 2.25

If you just want to scale the volume by 1.5, you would either need to keep the stroke the same as the 5" model, and multiply the bore by 1.5 or leave the bore the same and multiply the stroke by 1.5 (which you probably need to do if you are scaling the other linear dimensions). Intuitively, it seems wrong to scale one dimension without scaling the other. Then what about the dimensions of the valve gear? Surely that requires everything, including the stroke, to be scaled by 1.5. Then there is the power, which must depend to some extent on the swept volume, suggesting the bore and stroke should both be scaled. Surely the volume of the boiler will increase as its diameter and length are both increased, suggesting you would need a scaled bore and stroke to cope. It starts to get complicated.

Which is why Clive's advice seems sound.


Thread: BSB vs Cycle Threads
10/02/2018 20:28:04

British Standard Cycle threads use a 60 degree threadform, with a shape which visually resembles the Whitworth form. The 60 degrees makes the thread 'flatter', but the crests are rounded, like the Whitform threads, although the radius is different. The height of the BS Cycle thread from crest to crest is 0.5376p as opposed to the Whitworth at 0.640327p.The radius of the crest is p/6 (= 0.167p), as opposed to the Whitworth crest radius of 0.137329p.

So; BS Cycle threads are not Whitworth threads.

BUT, the author may have taken account of the fact that BS 811 : 1950 (still the current standard) provides the following note:

'It is customary practice in the cycle industry to use a 20tpi series of Whitworth form threads as an alternative to the cycle form thread series...'

That's not the same as saying that the BSCycle threads are Whitworth; and the practice seems only to apply to 20tpi threads.

Although, in general, BSCycle threads are 26tpi, the smaller diameters (1/8, 5/32 and 3/16 inch) are not. 1/8" is 40 tpi, while 5/32 and 3/16" are 32tpi. It would not surprise me to learn that the 1/8" BSCycle thread is sometimes used in place of the 1/8 x 40tpi imperial Model Engineer thread, especially where the focus is on the diameter and 40tpi specification in a mixed bunch of older taps or dies, but it is not the same thread, and should not be a fit for the proper Whitworth form ME thread. Mating the two will result in damage to the thread flanks even in a short hole.


Thread: Arduino Uno Programming Assistance Request
22/01/2018 19:13:07

I have just noticed the 'smileys' the site has added to the sketch. Wasn't me: honest.

If someone can tell me how to upload a sketch as an attachment, I can do that later tonight. If not; the smileys need to be edited out.



Edited By Marcus Bowman on 22/01/2018 19:13:33

22/01/2018 19:00:35

Testing the RTC is quite straightforward. Here's a sketch (below). As indiated in the comments, you will need to instal the RTC library from Adafruit (link inside the sketch.

// Date and time functions using a DS3231 RTC connected via I2C and Wire lib
// This example taken from Adafruit. Info at

// Wire.h is part of the Arduino IDE
#include <Wire.h>

// RTClib.h comes from
#include "RTClib.h"

// Connections:
// RTC SDA to Arduino A4
// RTC SCL to Arduino A5

RTC_DS3231 rtc;

char daysOfTheWeek[7][12] = {"Sunday", "Monday", "Tuesday", "Wednesday", "Thursday", "Friday", "Saturday"};

void setup () {

#ifndef ESP8266
while (!Serial); // for Leonardo/Micro/Zero


delay(3000); // wait for console opening

if (! rtc.begin()) {
Serial.println("Couldn't find RTC";
while (1);

if (rtc.lostPower()) {
Serial.println("RTC lost power, lets set the time!";
// following line sets the RTC to the date & time this sketch was compiled
rtc.adjust(DateTime(F(__DATE__), F(__TIME__)));
// This line sets the RTC with an explicit date & time, for example to set
// January 21, 2014 at 3am you would call:
// rtc.adjust(DateTime(2014, 1, 21, 3, 0, 0));

void loop () {
DateTime now =;

Serial.print(now.year(), DEC);
Serial.print(now.month(), DEC);
Serial.print(, DEC);
Serial.print(" (";
Serial.print(" ";
Serial.print(now.hour(), DEC);
Serial.print(now.minute(), DEC);
Serial.print(now.second(), DEC);

Serial.print(" since midnight 1/1/1970 = ";
Serial.print("s = ";
Serial.print(now.unixtime() / 86400L);

// calculate a date which is 7 days and 30 seconds into the future
DateTime future (now + TimeSpan(7,12,30,6));

Serial.print(" now + 7d + 30s: ";
Serial.print(future.year(), DEC);
Serial.print(future.month(), DEC);
Serial.print(, DEC);
Serial.print(' ';
Serial.print(future.hour(), DEC);
Serial.print(future.minute(), DEC);
Serial.print(future.second(), DEC);


Compile, then upload. Then open a Serial Monitor window. There is a pause before the first time reading appears, then an update every 3 seconds. Works very well.


21/01/2018 12:46:11

Updates are a pain. Updating to the current version caused the IDE to refuse to compile anything correctly, so it will not run on my MAC. Won't compile on XP of course, but does do the job nicely on W7.

Yes; I know my Mac OS is 'no longer supported' as is XP, but it is annoying when things like this are not at least backward compatible to the extent that they continue to work with existing sketches.


20/01/2018 07:19:44

You might look at AccelStepper, available at: **LINK**

That is a PWM library, designed for steppers, but giving a PWM output nevertheless. It accelerates up to a maximum, then, as nears the end of a sequence, decelerates. All, or part, of that might be useful.


09/01/2018 08:40:42

There are lots of ready-made programs for clocks and watches, but although using one of those MIGHT have saved time, we would not have learned as much as engaging directly with the problem and the code. I certainly learned a lot by studying the RTC chip structure and its internal registers and counters; which is something I had glossed over in other projects.

Thanks for the excuse for a mental workout!


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