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Member postings for SillyOldDuffer

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

Thread: VFD Choice
16/07/2018 19:49:11

Is your mill on the end on a longish cable? Like an extension cord, or perhaps a shed at the end of the garden. If so, the voltage drop on the cable when you draw current to accelerate might be contributing specially if the mains happens to be on the low side anyway.

One of these will tell you how many volts are actually available when the mill is running. If the volts sag noticeably when you power up and accelerate increasing the size of the cable might help.


Thread: How to machine an ellipse
16/07/2018 19:29:17

Alternatively, if an approximation is acceptable, this lozenge shape can be created on a milling machine with 4 straight cuts and 4 rotations. Easiest to do to a rod held vertically in a rotary chuck.

The shape, at least on a small scale in brass, can be quickly made with a file.


True ellipse shown in red for comparison. Construction based on circles and straight lines shown in orange.


Thread: Microsoft Windows 10S - One to Avoid?
16/07/2018 17:42:03

If you're thinking of buying a new computer, you may want to check which version of Windows 10 it comes with. There is a new kid on the block.

Windows 10S (Note the S) is a slimmed down go-faster version of Windows 10. It is claimed to be more secure.

By default 10S only runs software downloaded from the Microsoft Store. This may not be what you want or need : many applications are not available via the Microsoft store, and you are obliged to provide personal details. 10S also locks you into Edge, imposes other constraints, and may not be compatible with existing equipment:

'Many hardware accessories and peripherals (such as printers) that work with Windows 10 today will work with Windows 10 in S mode, but might have limited functionality.'

Early reports suggested that 10S would be permanently unable to install programs other than those made available via the Microsoft Store. However, the current version of the FAQ says it will be possible to switch 10S out of S mode one-way. Unfortunately it is not clear what effect rejecting 10S has on other features.

I thought Microsoft's FAQ on Windows 10S was unsatisfactory. It starts with a caveat: 'Details subject to periodic updating; check back here for the latest information.'. This is unhelpful if you are trying to make a fact based decision. More worrying, I do not think the FAQ unambiguously confirms that 10S can be made to behave like an ordinary unrestricted Windows 10 installation.

If about to buy a new computer with Windows 10S I suggest first reading Microsofts FAQ and then searching the web for up-to-date reviews. The product may not be for you!


Thread: Lathework for Beginners
16/07/2018 13:38:20
Posted by Ron Laden on 16/07/2018 12:48:51:

Thanks Dave,

I need to make some guide rollers for the loco using 1 inch Nylon 6 bar, I have read that a very sharp HSS tool with a 1/16" tip radius makes a good tool for the job. What about speed..? I can experiment of course but wondered what would be a good starting point.


Not cut Nylon myself. I'd guess high-speed with a sharp knife-like tool.

Cutting steel it's the tool tip that gets hot, loses it's edge and rubs. With plastics it's the material that gets hot, deforms, sticks and behaves badly. You may have to experiment, I'd start by slicing off the plastic quickly and letting smallish chips carry off most of the heat.

Perhaps someone who has done it will advise please?


Thread: Digital RPM Display Problem
16/07/2018 13:04:45

Can you provide a link to the actual unit please?

Looking at your circuit, I think Blue (signal out) should connect to 5 (Measuring+). That would explain why you don't count revolutions but not why the sensor lights up.

Black ('Test +'?), is probably DC- for the sensor but I'm guessing!

Anyway, with luck, you have Black and Blue the wrong way round. Your diagram looks correct apart from that.

Signal Earth and Power ground are likely to be connected together inside the box. Best practice is provide a signal cable with its own earth to avoid the possibility of picking up noise from the power line or spark leads in an engine. In this application you can probably use either.


PS John Rudd types faster than me, at least it's the same answer!

Edited By SillyOldDuffer on 16/07/2018 13:05:55

Thread: 1.1mm hole in brass
16/07/2018 12:38:42
Posted by Steve Crow on 15/07/2018 18:38:17:

Albion Alloys make micro brass and nickel silver tubing with a 0.1mm wall. You can get it from Chronos and others.

They make a 0.5 OD x 0.3 ID - three foot long lengths for 6 quid. This isn't even their smallest! They also sell selection bags of telescoping sizes.

Could you use it as bushing for your existing 0.5 holes?

I've used this stuff in all different sizes as bushes etc.

Thanks Steve, I've ordered some!


Thread: Political views within the forums
16/07/2018 09:29:09
Posted by Michael Gilligan on 16/07/2018 08:51:11:
Posted by Clive India on 16/07/2018 08:34:15:

I just read 3 pages of this trying to find any relevance to model engineering - so why is it here?


Think of it as a midden ... It's serving to keep the rubbish in one place.


Edited By Michael Gilligan on 16/07/2018 08:51:33

The statistics suggest the people want a midden. Of the current 40 threads, this one is the 8th most read, and is 4th in terms of active contributions.

In my own defence, I did have a go at defining 'Model Engineering'.


Thread: 1.1mm hole in brass
15/07/2018 18:09:20

Posted by SillyOldDuffer on 15/07/2018 16:17:12:


Putting it another way, you can squeeze thirteen 0.3mm diameter holes inside a 1.1mm diameter rod. Now that's a challenge!


Who is this clot? You can only drill nine 0.3mm diameter holes inside a 1.1mm circle. Thirteen would overlap.

Ho hum...

15/07/2018 17:42:44
Posted by clogs on 15/07/2018 16:23:49:

Mr Duffer, what are u making that needs drill's that small.......?


Long story cut short I'm making:

A Pendulum Clock Analyser:


That needs a pendulum clock thingy to test it:


The test clock has a standard steel bob and I'm experimenting with different materials for the rod. I started with polyester cotton thread, then 1mm carbon fibre rod, currently testing 0.5mm carbon fibre rod, and I have 0.3mm diameter carbon ready for the day I manage to drill a couple matching holes:


Another reason I may be in trouble drilling tiny holes in brass could be work hardening? It's likely that out of fear of breaking drills I'm pecking too softly, rubbing rather than cutting, and thereby toughening up the brass such that the tiny drill isn't strong enough to push through. Quite a lot of bother in my workshop is caused by poor technique.


15/07/2018 16:17:12

No sympathy from me - your excavations are all whoppers by my standards. (I'm currently struggling to make a 0.3mm diameter hole 10mm through brass.)

Down to 0.5mm diameter, easy peasy. Below that I'm finding life gets tricky with drills less than 0.5mm. I think the reason is because the strength of a drill is proportional to the square root of its diameter.

A 1.1mm drill is 14 times stronger than a 0.3mm drill allowing much more room for clumsiness. A 0.5mm drill is three times stronger and even I have a chance of not breaking one.

Diameters illustrated  are 1.1, 1.0, 0.8, 0.5 and 0.3mm:


Putting it another way, you can squeeze thirteen 0.3mm diameter holes inside a 1.1mm diameter rod. Now that's a challenge!







Edited By SillyOldDuffer on 15/07/2018 16:18:40

Thread: Lathework for Beginners
15/07/2018 13:30:45
Posted by Ron Laden on 06/07/2018 10:58:13:

Thanks Dave, the 10000 divided by diameter is easy to remember, that will be stuck in my head now.



It's more respectable guide than it might first appear.

All materials have a recommended cutting speed which is determined by a combination of chip formation and how hot the tool gets. It happens that mild steel and HSS cut best at about 30metres per minute.

So RPM = 30 / pi * diameter (in metres)

By converting metres to mm and taking pi = 3, you get the easy sum:

rpm = 10000 / diameter(mm)

Other common materials cut a bit faster or a bit slower than steel and the sweet spot for a particular job can usually be found nearby by experiment. Multiply rpm by 3 to 6 if using carbide rather than HSS.

A professional shop would find it worthwhile doing a more sophisticated calculation, but for amateur use the shortcut is good enough. It's unusual for an amateur to maximise production rates. We live within the limits of our skills and machines, and have time to tweak for best results from what we have.


Edited By SillyOldDuffer on 15/07/2018 13:31:55

Thread: All things Beaver Mill
15/07/2018 12:51:44
Posted by Peter_H on 14/07/2018 22:31:25:

So what is the grid?. Is it a 1mm grid or a 10mm grid?. If I want to snap the cursor to a specific grid multiple, I want it to be defined by me. The whole idea of a grid that changes is an anathema to me. If I want to snap to a 1mm grid, I want exactly that, I don't want it to change to 10mm or 0.1mm depending on zoom level. I cannot see how there is any application for that. The only thing that comes to mind is that maybe you see the grid as some sort of visual aid, where the normal in my experience is that it is something to magnetically snap the cursor to.

The snap settings don't seem to be very stable either. I have twice lost application grid settings between program runs, and whether the grid icon and the auto icons, under the snap menu, are on or off at any particular time seems completely random. However many times I turn Auto off and click Grid on under that menu, they just revert at what feels like random intervals. Either there are some big bugs around this area, or, more likely, I'm missing some setting.

Other than that quirk, it's the best 33EU I ever spent. Excellent piece of software, I'd use it for 2D work by preference.


That's interesting. I thought it was possible to lock the grid to work as you describe, but the application settings sort of but don't quite work as I expected. It may be worth raising on the qcad forum.

Could be an example of horses for courses - you use the tool differently to me! I'd not spotted before how the grid behaves because I rarely use the grid as my main snap guide. I use it to establish the base point and it's convenient for drawing lines that happen to fit the grid. But quite often my lines don't snap to the grid.

My typical mode of working often requires a construction layer, maybe several. They contain the lines, circles, intersections and dimensions that establish snap points to suit the object I'm drawing. And, the more complex the drawing, the more likely it is that lines must be referenced from drawing features rather than a fixed grid.

Try drawing this object with the grid:


While qcad's approach to scaling the grid happens to suit me, it's not good for what you're doing. It may help to keep an eye on the grid scale at bottom right:


10 < 100 means the dots are 10mm apart and the tiny dotted lines 100mm.



Edited By SillyOldDuffer on 15/07/2018 12:54:54

Thread: Macgregor digimac transmitter receiver crystals 3
15/07/2018 11:02:50

Try googling for 'Radio Control Crystals'.

Crystals of this type aren't as readily available as they used to be because technology has moved on. ebay may be your best bet. I found this RC seller disposing of unwanted stock. RS Components sell crystals

Also Farnell and others. You can have them made to order, but that's expensive for one-offs. This chap in the USA specialises in older crystals.

The important thing is the frequencies of the crystals, for which you need to read the manual. The transmit crystal and receive crystal are off-set from each other by a gap that suits the receiver. I don't know if radio control offsets are standard or peculiar to each model. Perhaps another forum member knows?

The other issue with crystals is the package. They come in various sizes with pins spaced to fit various types of socket. I'd guess an old transistor unit would be HC6/U or HC48. Some are soldered in. If a crystal doesn't fit the socket the connection can be bodged to make it work, but this isn't for everybody.

Obviously hubby has a good reason for wanting to revive an antique radio control unit. But, if he just wants to use it for bog standard radio control, tell him it's far less stressful to buy a new one. Disheartening when you have gone to a lot of time, trouble, and expense sourcing crystals to switch on and find that the transmitter, receiver, or both are faulty.


Thread: Political views within the forums
15/07/2018 10:19:33
Posted by pgk pgk on 15/07/2018 09:25:53:
Posted by JasonB on 14/07/2018 15:09:21:

You also need to bear in mind we have an international membership and some contries have different views to what can be done in the home workshop. For example one equivalent to Warco have a range of "gunsmith" lathes! Also home blade smithing has a large following even with it's own TV programs.

Suprisingly my wife enjoys that TV show - mostly the turning of a hunk of old metal into a shiney object. She now even appreciates my wandering into the shed with a bit of rusty hot roll and coming back with a finished item ( so long as it looks nice - function is irrelevant to her)


My daughter likes it too. (The programme is 'Forged in Fire', currently showing on Freeview Blaze in the UK.)

It has quite a following:

John Gomes liked the show. He liked it so much that he decided to forge a sword in his own backyard. It took firefighters the better part of six hours to quell a fire caused by his attempt. The fire burned through almost 30 buildings, leaving as many people displaced in Cohoes, New York.

Gomes' public defender said "this is just a terrible, unfortunate accident, but it's not a crime." Still, he was charged with fourth degree arson and reckless endangerment. The lesson here? Don't try this at home.

I was surprised that the weapons they make appear to be legal in the USA. Seems they're not. At the end of each programme the knives & swords are surrendered. For legal reasons they're classified as film props and they aren't street legal.


15/07/2018 10:00:52
Posted by XD 351 on 14/07/2018 11:50:15:


My question is what do these threads have to do with model engineering and why were they allowed to be created ?

Motorcycles - except model onesAirplanes -except model ones
Household electrical work
Anything to do with firearms
People wanting to know what is wrong with their car
People who are having issues with thier internet connection
Etc etc .


'Model Engineering' is a clever title for our hobby because it covers so much ground.

Model can mean:

  • 'a three-dimensional representation of a person or thing or of a proposed structure, typically on a smaller scale than the original' or
  • 'a person or thing regarded as an excellent example of a specified quality'.

Engineering also has two definitions:

  • The branch of science and technology concerned with the design, building, and use of engines, machines, and structures, or
  • The action of working artfully to bring something about.

Within those permutations pretty much anything goes.

'Engineer' is even more vague. In the USA it includes locomotive drivers. No better in the UK, almost any technical job from 'bloke with tape measure' to Isambard Kingdom Brunel can be an 'Engineer'. Not easy to define what a real engineer is. The professional associations insist on a degree level qualification involving maths. I'm not so sure, because really good engineers are creative. To me, it's the ability to design rather than copy or apply rules of thumb that sets the engineer apart from the artisan. (Nothing wrong with artisans, they're the ones who build, use and maintain technology, which requires a different skill set.)

The only item on XD351's list I would reject is Astrology. Even then I suspect it's a typo - Astronomy is definitely legitimate in my book.

Once the door is opened on creativity, another group of subjects become valid. I'm usually content with functional brutalism. Others find joy in doing a good job mending and restoring things. Hats off to crafts-persons making aesthetically pleasing items like clocks, pens, miniatures, well-made tools and other objects of desire.

Finally, the social and educational aspect of the hobby. Understanding what the other guy is up to, and how he does it, can be useful. Buying new vs second-hand, identifying materials, problem solving, separating fact from opinion, risk management,  etc. Above all, none of it should be dull. Ideally all posts should end with a joke. Shame I don't know any...



PS Definitions from the Oxford Living Dictionary

Edited By SillyOldDuffer on 15/07/2018 10:06:38

Thread: All things Beaver Mill
14/07/2018 20:01:22

Posted by Peter_H on 14/07/2018 13:17:23:


Auto grid setting sounds insane. I've worked with CAD for decades and always used the grid as something to snap the cursor to when needed and I've never seen it used any other way by anuyone I've worked with. What would you use an Auto grid for?. I fail to see what use it is if it's size continually changes.


Method in the madness. The grid scales appropriately as you zoom in and out.

Here I've drawn a 10mm square. The grid has dots at 1mm.


If I zoom in on the top left corner:


the grid scales to a more helpful resolution. The dots are now 0.1mm apart, which is helpful for working on a detail.


Thread: helical lathe prototype - choice of components
14/07/2018 10:09:50
Posted by john constable on 13/07/2018 22:17:15:

So GRBL is a piece of software - like an OS - that runs on the arduino board and controls the controller board by interpreting gcode that is sent to it by usb from a pc which is running one of many user-written GUIs?

Do the GUIs generate code from instructions you give it or do they convert from a CAD image?

"So GRBL is a piece of software - like an OS - that runs on the arduino board and controls the controller board" - exactly right. It translates G-code commands into the motor steps needed to move a tool or print head to an X,Y,Z coordinate.

grbl will respond to commands typed into a character terminal, this is the best way to test your configuration to prove the motors respond correctly to simple commands. For production work that simplicity gets tedious, hence the GUIs. They do the same job but - once properly set up - are slicker, more helpful and whatever else the designer has thought of.

What the GUI's do varies a bit, but there look to be three levels of sophistication:

  • An improved version of a character terminal, tailored to support 3D, with easier connection.
  • A 'sender', allowing lists of g-code commands to be sent from files, providing access to folders, with buttons allowing grbl to be reset, jog, or otherwise positioned.
  • A 'sender with previewer', these can display the tool-path on screen, allowing the operator to see obvious mistakes before sending them to the machine.

A picture's worth a thousand words, this example is grblgui. (I've not used any of them and can't comment on installation, ease of use, or bugs.)

Do the GUIs generate code from instructions you give it or do they convert from a CAD image?

As far as I can see none of the free GUIs convert from CAD, you either type the code in by hand, or load it from a file. The file is usually created by something else; either a conversion program, or by the drawing package itself. Jason's post shows how Fusion360 does it.

A superficial read suggests OpenSCAD can't produce g-code directly, rather users export the model as a DXF file and run that through a DXF to G-code converter. At this stage it's worth mentioning a potential booby trap! The g-code files needed to print a 3d object are additive, that is the object is built inside-out by depositing layers until the shape is finished. The g-code instructions needed to mill the same 3d object are subtractive, that is the tool removes material from a solid block until the shape is finished, outside in. grbl doesn't care, but it's possible that software written specifically for 3D printing might not support milling and vice-versa. Your lathe is subtractive and the g-code you send to grbl needs to be that way round. It may be necessary to try a few alternatives to find what suits you best.



Thread: VFD Choice
13/07/2018 21:29:15

Could it be they've sent you a log potentiometer rather than a linear? Log types change value rapidly at one end and slowly at the other. Does it have any markings?

Thread: helical lathe prototype - choice of components
13/07/2018 20:41:37

Posted by john constable on 13/07/2018 18:35:21:..


So, is there a way to send your complete G-code to the arduino from the pc without using the sd card?

Yes, it's easy, perhaps easier than getting the SD Card working. Have a look at this Getting Started page.

It also recommends 'that you use one of the many great GUIs that users have written to stream your G-code programs to Grbl and to fully harness all of Grbl's capabilities. NOTE: Check out ShapeOko's Wiki. It has the most up-to-date and comprehensive list of Grbl GUIs.' Following the link reveals loads of options.

The way you're approaching this is very sensible. Making use of kits and existing software will save lots of time and brain ache.


Thread: How can I drill a deep, non-standard, small diameter, hole?
13/07/2018 19:11:31

Ho hum, commercial twist drills arrived today with mixed results.

With a gentle touch and many withdrawals to clear swarf I was able to drill a 0.5mm hole 10mm deep with my screw-type tailstock without too much trouble.

Not managed to drill a deep 0.3mm hole though. Drill started OK then seemed to hit a hard spot in the brass rod. I can't feel if the drill is making progress or not and the first warning of trouble is the drill whipping.

The drills are tiny and they bend and break easily:


My lathe has a top speed of about 2500 rpm. Seems this is a little on the slow side - one website recommends 40,000rpm for 0.3mm HSS and 'if available' more than 100,000 rpm for carbide.

All my home made drills are now broken. Thank goodness I didn't give up my day job!



Edited By SillyOldDuffer on 13/07/2018 19:12:35

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