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Member postings for Bob Mc

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

Thread: What Did You Do Today 2019
02/08/2019 17:50:37


Thoughts are with those people of Whalley.

Yes I live in Poynton some 12? miles or so down from Whalley Bridge and there is a small stream at the top of my road which has overflowed its banks washed a stone bridge away completely, the fields have flooded and factories on a nearby industrial estate have been inundated with water.

As I understand it .. if the dam at Whalley gives way the water will inundate the town centre and follow the path of the canal probably taking all the boats with it.!

There has been a concerted effort by greedy developers who have no connection with the Poynton area to put hundreds of houses on what is basically an area of natural beauty, perhaps they might be put off when it is realized that the fields are in fact flood plains.

Lets hope the RAF at Whalley can save the day again.!


Thread: TTFN
18/07/2019 20:53:09

Andrew I hope you will reconsider, I can only class myself as an amateur/hobbyist and rely on experienced people as yourself to let us know how a professional tackles some of the problems.... as stated previously I find your input quite interesting and well presented... Its sometimes the case that people say things they don't really mean. rgds for the future....Bob.

Thread: What do you use your lathe for?
05/07/2019 17:18:51

I can now grind the edges of milling cutters on my Arduino controlled lathe...the ones I have ground have a pitch of 80mm. Bob.

Thread: Sharpening Milling cutters
30/06/2019 18:29:01

Hi Paul...

I wrote an article for MEW in November 2015, No 235. The design uses 2 Arduino's which were coupled together so as to provide synchronism in providing pulses for the stepper motors, however it is not necessary to electrically couple them and I am assured that if the Arduino's have proper Xtal signal sources you can use them as they are.

The program could not be simpler for the Ard's ... it uses the Blink program and the article describes how to find the correct pulse times, there is also a circuit and explanations, someone with a small knowledge of Arduino programs could easily set it up. I can give you the progs no problems.

There is a Spindle speed program which just runs the Blink sketch continuously and there is a Leadscrew motor program which has an interrupt control to start the Leadscrew motor at a specific point in the spindle rotation.

I have used this lathe many times for making screw threads of various pitches, some quite peculiar for telescope eyepieces and suchlike, but the beauty of the system is that you can adjust the parameters for virtually any pitch you want, the only drawback is that my spindle motor is not as powerful as I would like, you could even vary the pitch within a pitch ... there is absolute full control over this.

The system however does not have any feedback and relies on the start pulse to set it running, if there is too much load for the motors there will be problems so light cuts are needed, in the case of a grinder for milling cutters there would be no problem.

Bob.. -.- -.- -.-

30/06/2019 15:18:24

Hi Paul...

Most cutters needing sharpening will only have part of the helix available, if they are anything like the ones I have! which were used in a machine shop and thrown out when they became worn on the edges.

In order to find what the pitch of the helix is, you can put the cutter in the lathe 4 jaw chuck and set the end of one of the cutting edges horizontal with a rule or straight piece of steel set in the toolpost holder, if you have an electronic Wixey angle gauge this is set on the chuck and zeroed, this could be magnetically fixed to one of the jaws, or you could use the jaws themselves as indicators of the spindle angle ... this is always 90deg or 180deg.

The chuck is then hand rotated 1/4 of a turn or 1/2 a turn (if you have that much left on the helix) and the rule is moved along using the leadscrew handle so that it lines up with helix cutting edge, the x distance is now 1/4 or 1/2 the pitch .... for example if the distance moved to line up with edge at the new position is 20mm and you have rotated the chuck 1/4 of a turn then the helix pitch is 4x20 = 80mm.

I have only used this method on 2 flute cutters and for the grinding operation will be making a fitting something along the lines of Harold Halls grinder cutter tool holder so I can rotate the cutter for grinding the other flutes without disturbing the electronic setup which indicates where the spindle will be when the leadscrew is started up.

I don't see why this method couldn't be used on a normal screwcutting lathe if large pitches are available which would provide the same pitch as the cutter helix, the only problem might be that the spindle speed is too great, I am using a spindle speed of 1 rotation every 8 seconds which gives the grinding wheel some time on the work.

Hope that helps....Bob -.- -.- -.-

30/06/2019 12:01:48

Additional to my post :- Sharpening Milling cutters...

Just a note of safety...

The Dremel resin bonded grinding wheels are easily damaged and bits of wheel can fly off at high velocities...PLEASE WEAR EYE & FACE PROTECTION .

Bob -.- -.- -.-

30/06/2019 09:11:39

Sharpening milling cutters in my Arduino controlled screwcutting lathe...trial run.

I made the Harold Hall cutter grinder which sharpens the end of the cutter quite well, however trying to sharpen the flute edges did not produce the clean edge you see on new cutters, so I decided to use the screwcutting facility of my Arduino lathe which can be programmed for virtually any thread.

Pic below shows an end mill I sharpened on H.H's grinder with cutter set up in lathe ready for a trial grind of the edges, you can see that the finish is a bit rough and unsteady due probably to not feeding the cutter against the grinding wheel with a smooth linear motion in H.H's fixture.


I used a Dremel fixed to the toolpost with a small grinding wheel, the pitch of the cutter is about 80mm and this was loaded into the Arduino's Spindle and Leadscrew program with the spindle rotating at 1 rev every 8 seconds.

I found that the secondary grind angle could be set up by starting the spindle rotating a little earlier relative to the Leadscrew motion startup, this was achieved by putting the grinding fixture a small distance from the initial start point of the primary grind set up so that the wheel hit the rotating cutter at a later time., ie no special measuring device needed.

I intend to make a jig which uses the H.H collet holding jig in order to re-set the cutter for each flute edge, however the results of the initial grind were quite pleasing with clean sharp edges and a nice finish.


I was surprised that the small resin bonded Dremel grinding wheel produced such a nice finish, I inclined the wheel at about 45 deg to the cutter axis, I finished the ends the normal way in the H.H grinder.

..Bob -.- -.- -.-

Thread: Pressure gauge help needed please.
27/04/2019 17:42:01

Thanks Jason/ John and all..... your comments have spurred me on to find something a little bit more involved to make.... will have to scour the ME mags.


27/04/2019 13:21:09

I have to say thanks again...this has got to be the quickest fix I ever did! thanks to forum members advice.

I now want to start another project but don't know if my skill level is up to making something more complicated or with a better level of craftmanship.... could any of you more experienced gentlemen give me your opinion based on the build of the Double Diagonal engine in the above pictures.... I really don't know what skill level I should place myself at and what project I should attempt next...

nb...all the parts excepting the globe valve and pressure gauge were my own work.


27/04/2019 12:19:20

Thanks to all....basically you are all right with the advice given! can't thank you enough !

I had already made a stand to fix the gauge on and by sheer luck I made it a cylindrical pillar, it seemed obvious to coil the small pipe around it as many turns as I could, 1/2 an hour later and I tried again.... the indicator needle was now steady... pics below..

Many thanks great people....Bob.


27/04/2019 09:52:52

I made Mogen Kildes double diagonal engine (ME4383) which is only my second engine and fitted a small air supply valve and a pressure gauge...see picture.

The engine works great and only needs a couple of pounds of pressure to get it going and I thought to put a gauge after the air supply valve in order to give some indication of what the actual air pressure was.

I was expecting that the pressure gauge might fluctuate a little but I think I will have to remove it due to the needle vibrating at an alarming rate and I don't think it will last long in its present situation.

Is there any kind of a damper I could make? or will it have to be removed? Can anyone help.....thanks...Bob.



Thread: Mogens Kilde's Double Diagonal Engine
13/04/2019 12:09:39

I just had to make one of these... Now nearly finished, wants a few more bits and a cleanup but it certainly goes ok..

I altered Mogens original design with triangular section crosshead slides and a different frame design with the cylinders having square end sections connecting directly to frames. I intended to get rid of the steam pipes to the cylinder and have a passage for the steam go directly through the frame and into the engine, but I must admit the U shaped pipes do look quite good,


Thread: Potty overcrank
29/03/2019 18:02:29

And this one.

The very first engine I attempted, gave me a good idea of how to build an engine... not got round to prettying up yet.... but it goes like a mad thing.


Thread: Scrollsaw for the occasional user
12/03/2019 11:52:22

Hi Ian S C ...

Are you saying you have an engine driving that saw! does look as if there is a boiler and a flywheel in the picture.

If that's the case its great if you have actually made and engine to do some serious work, would definitely like to see that running...!


11/03/2019 16:40:59

Hi Ian T...writes...

"Please don't take this as criticism Bob Mc - but I break a lot less blades when I use the saw vertically and just let it drop into the work on the down stroke (e.g. let the saw do the work) etc."

No I certainly won't take it as criticism and I am only glad to hear how others tackle these problems... I will give your method a try out and see if it does the job any better, my only concern is that you say you use this method for brass which is a lot softer than mild steel...nevertheless thanks for your post ... if it works I will give due credit.


11/03/2019 12:17:41

I am with Roy Entwistle on this one, re posting :11.03.2019.

"If you are wanting to cut thin metal occasionally then whats wrong with a piercing saw? If you want to cut thin wood then either a coping saw or a fret saw"


I will say however that the blades are inclined to break very easily because 'hand' control is not steady, but I found a simple way to help save the blades and I have cut 8mm mild steel for at least an half inch length before the blade had had enough.

It doesn't sound much but the alternatives are either drilling bashing and filing or going in for something expensive which could cause the 'Marital' arts to become the 'Martial' arts and the blades come in packs of about 10 and are quite cheap.

The saws do have a tendency to wander which doesn't help in keeping the blade in piece.

Picture shows piercing saw cutting two sandwiched pieces of 4mm mild steel for Mogens Kildes Double Diagonal Engine, the saw frame top rests on an engineers clamp which is inclined to give a guided cut in the right direction.


piercing saw.jpg

Thread: Atlas Sphere Lathe
04/03/2019 12:06:03

Hi Phil...

just seen a very similar lathe on ebay with what looks like a full set of gears... I can make out about 16 in all,

it is listed as an ATLAS 618 LATHE.

I've got one myself but made an electronic gearbox for it.

Hope its of some help....Bob.

Thread: print-offable and laminatable chart
05/02/2019 15:13:54

Micrometer...? dont know

Thread: Last Night's Astro Image
29/01/2019 17:19:11

Mick B1.... you beat me to it.... I don't know that one either..., but due praise to Neil, great pictures taken with a small scope.

Thread: What is this machine?
22/12/2018 09:44:46

John Reese says.....

" There must be quite a few seniors on this forum. I know what a comptometer is but I can't recall actually seeing one and I am 81."

Yes... in my first job at the Equitable and Cooperative Society in 1965... ie The Co-op...I had the pleasure of using one for a full week but not like the one shown in the picture, the one I used had a handle , when you put in the amount to be added you then pulled the handle towards you and this was added to the last total..

As there were quite a few other comptometer operators in the room, mainly young ladies,, wink there was a lot of noise from the little machines, it was difficult to keep your mind on the job .....due to the noise... honest...! I got sacked shortly afterwards....


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