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Member postings for Andy_G

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

Thread: Horizontal hit and miss engine
15/11/2020 21:48:05

Thank you!

Thread: Cutting Small Discs out of Glass
15/11/2020 21:41:30
Posted by Georgineer on 15/11/2020 16:10:54:

It occurs to me that it should be possible to mount a piece of glass to the lathe face plate with double-sided tape, or some other adhesive. Then an ordinary glass cutter could be mounted in the top slide and brought up until it touches the glass. A single turn of the chuck by hand should scribe the line, then the circle could be broken out in the ordinary way.

It can work - the same principle is used to cut out circles commercially. You need to start the break from the outer edge of the glass sheet and get this to run into the circle. It's likely to take quite a bit of practice.

For small diameters, the circles are broken out thermally - using cold metal cylinders roughly the same size as the circle which are placed in liquid nitrogen, then onto the glass (after scoring)

You might get somewhere using a metal cylinder from the deep freeze to get the circle to break out, but I still think you'd need to break the outer square of glass to release it.

Unless it's for entertainment value I would go to core drilling one out (very cheap diamond core drills are available on Amazon, etc. which will work fine, but *must* be used wet). Or trepanning one with a metal lap and loose carborundum powder - anything will do for a one-off: I used a boot polish tin to trepan out a secondary mirror for a telescope. Needs a fairly slow drive though (I wouldn't dream of doing it by hand).

Or just buy one!


(Edit - you need just enough pressure on the cutter for it to create a vent in the glass - it will vary with the type of cutter. You will need to take into account some movement in the glass surface - i.e. the cutter cannot be rigidly mounted - it needs to float.)

Edited By Andy Gray 3 on 15/11/2020 21:43:45

Thread: Cutting Microscope Slide Glass
15/11/2020 12:19:41
Posted by Dave Halford on 15/11/2020 11:59:14:

For some reason old glass does not like cutting cleanly

Cutting with a wheel or scribe relies on creating a vent (crack) in the glass surface that propagates through the thickness when that surface is put in tension.

Old glass becomes 'weathered' (even indoors) which both makes it harder to develop that initial crack, and also provides a plethora of microscopic defects which can lead a propagating crack to wander off.

(Sorry for 2nd message - can't seem to find how to include a separate quote).

15/11/2020 12:11:32
Posted by Robert Atkinson 2 on 13/11/2020 20:45:23:

If you want to cut the very thin cover slips try a sharp pair of scissors under water. Have a tray or similar underneaith to catch any fragments.

Posted by Howi on 14/11/2020 09:55:31:

i read somewhere that you could cut glass slides for microscopes etc, by using sharp scissors under water - lots of shattered slides and cut fingers, not one cut cleanly as i desired

Posted by Brian Wood on 15/11/2020 09:49:54:

Using a good pair of strong scissors, cut the slides underwater, thin sections like microscope slides responded well to the method.

I had read / heard the same thing (no idea where), but despite an almost unlimited supply of thin glass and repeated attempts, this never resulted in anything other than shattered glass. I would love to see someone actually doing it.

Thread: Horizontal hit and miss engine
14/11/2020 18:42:12
Posted by Simon Birt on 14/11/2020 15:31:16:

Very nice and runs well. What have you used for the ignition? I am building a Farmboy and am starting to think about making sparks.


Thank you


I used a "Replacement Complete Ignition Set for Single Cylinder Gas Engines" module from Hobby King:

Unfortunately seems to be on back-order now

It needed some careful shaving down in order to hide it inside the engine pedestal.

Edited By Andy Gray 3 on 14/11/2020 18:47:18

Thread: Lidl Portable Bandsaw
13/11/2020 23:47:57
Posted by Martin of Wick on 13/11/2020 20:47:41:

Afraid I weakened and after the dismal experience of Lidl's offering, decided to try the Aldi version (can always send it back, I reasoned and it might save me having to get a Femi!).

Arrived today, pleasantly surprised, substantially better made/finished than the Lidl version,

I also weakened, having missed out on the Lidl saw due to the Welsh lockdown ban on non-essential bandsaw sales, and ordered the Aldi one. It arrived the other day and I'm favourably impressed (apart from the comedy vice, but even that can be induced to work). It's quite gratifying to hear that it's "better" than the Lidl one, rather than being a dearer version of the same thing.

The threads in the three arm mounting holes on mine were also ridiculously tight - I thought I had cross threaded them, but I hadn't.

Other than that, the saw appears quite substantial and feels very solid. It's cured me of the urge to build a power hacksaw

Thread: Cutting Microscope Slide Glass
13/11/2020 23:24:38

A normal (tungsten carbide) wheel cutter should work OK down to about 0.5mm and give clean cuts. (Look after the cutting wheel - any chips out of its edge will be reflected in the glass cut quality).

You may struggle to break off the narrow edge of the slide - it might help to scribe all of the cut lines first (in a # pattern) then break the larger pieces, leaving the narrow edge until last. This avoids the tendency of the cut to run off at the start/end of the scribe line.

You may find that lubricant (white spirit, or similar) helps.

Keep everything clean...

Edit - if you can find a good edge on the diamond, that will work, too, but it does need to be a very sharp point to create a 'vent' in the glass. A worn diamond will scribe a line, but there won't be a vent under it and the glass won't break cleanly.


Edited By Andy Gray 3 on 13/11/2020 23:27:04

Thread: 7x12 Bearing Spacer
12/11/2020 18:36:05

Posted by woody1 on 11/11/2020 20:14:02:

I bought my angular contacts...

Posted by Neil Wyatt on 12/11/2020 11:36:06:

...I had to shorten the spacer by 4mm...

Just checking - if woody1 is fitting A/C bearings, there shouldn't be any need to shorten the spacer, should there? The A/C bearings are supposed to be the same width as the originals, I believe.

Just re-make in metal to the existing dimensions? (My 7X lathe is a different make with a brushless motor, or I'd offer to measure the spacer!).

12/11/2020 18:23:12
Posted by Neil Wyatt on 12/11/2020 13:41:09:

Slightly updated versions of my articles written about 15 years ago!


Very interesting - I've not been able to find (m)any objective before / after assessments of the effects of bearing replacement.

If you were to do it again, would you go with angular contact or taper roller?

Thread: How can a steel thermos drinks flask fail?
10/11/2020 11:00:03
Posted by not done it yet on 09/11/2020 22:51:56:

Easy - the vacuum leaked out devil

Where did it leak to?🙂

It'll be under the stairs, with the other one wink

09/11/2020 20:44:31

Just for the record, I have had a 'Hot Stuff' branded (Vango??) stainless flask for the best part of 20 years and it still keeps drinks scalding hot all day (remnants are still luke warm next morning). It is definitely all stainless & vacuum insulated. It's just a shame that the matching cup is somewhere amongst the boulders at the foot of Cenotaph Corner in the Llanberis pass :-/

09/11/2020 18:32:10
Posted by Andy Gray 3 on 09/11/2020 17:09:48:
Posted by Michael Gilligan on 09/11/2020 15:58:38:
So ... What do you think the failure-mode was ?

Easy - the vacuum leaked out devil

Blimmin' autocorrect...

09/11/2020 17:09:48
Posted by Michael Gilligan on 09/11/2020 15:58:38:
So ... What do you think the failure-mode was ?


Easy - the vacuum leamed out devil


Edit to add:

Fascinating details about how "the good ones" are made here, including several videos:

I would suspect a fault in a weld has resulted in gradual loss of vacuum, or some small fault in the raw tube (inclusion, lap, etc.) has opened enough to result in loss of vacuum

Edited By Andy Gray 3 on 09/11/2020 17:33:20

Thread: Heating copper boilers
25/10/2020 15:35:04
Posted by Bob Worsley on 25/10/2020 10:36:08:

... a couple of large cables, taking 200A at 5kW, so quite stiff.



Work out the resistance of your potential boiler combo, and then use the P=I^2 x R formula to figure out how many amps you'd really need to get 5kW dissipation.

It's likely to be 2 orders of magnitude higher than you've guessed

Making connections for this sort of thing is also non-trivial. (I've worked with similar technology - One needs to ensure that the current is delivered uniformly, as resistivity tends to increase with temperature, so any non-uniformity results in localised hot-spots which progress very quickly to a puddle of molten metal and a gap where it used to be.)

Thread: Diamond Drills
24/10/2020 11:15:05

When I did some work with diamond tooling years ago, machining steel was an absolute no-no (it reacts with the diamond under very high pressures, IIRC). CBN was needed for ferrous metals.

UK drills do tungsten carbide tipped drills which might be a better bet if cobalt ones don't work.

Carbide tipped

Cobalt for hardened steel

Thread: Why is this guys mini lathe parting off so well?
23/10/2020 12:43:27
Posted by Philip Antoniou on 23/10/2020 09:35:29:

I just shimmed the gibs on the underside of the carriage as they were riding on the edge of the ways. I used shim washers instead of cutting strips of shim that most people use, seems rigid. Fitted the Arceurotrade brass gibs; one has made an improvement, letting me tighten up the gib more while still letting the side move. But the other gib is the wrong size and just jams the movement.

Be slightly careful with the shimming - it cures a symptom rather than the cause. The gib shouldn't bear on the bottom of the slide (or the top). If it does, it is either not being held properly by the adjustment screws, or is rotating slightly, which forces the lower corner into the bottom of the slide.

In an ideal world, the pressure on the gib should be at right angles to the sliding face - it isn't on the mini lathe (and many other designs, too) so there is a tendency for the gib to be pushed downwards as the adjustments are snugged up. There needs to be enough engagement of the adjustment screw tips to stop this. Also, as the gibs are so narrow, the point of action for the adjusting screws needs to be close to the sliding face to reduce the tendency of the gib to rotate, not on the back of the gib as is the default.

After trying several internet solutions without making a huge difference, the thing that sorted mine was to depen the recesses in the gib to take the tips of the dog-point adjustment screws. These need to be angled to match the adjustment screws, not flat to the gib strip itself. I managed to do this by clamping the gib to the slide itself (with the hole location overhanging) and drilling them deeper. I also had to add clearance to prevent the threaded part of the adjusting screws fouling the gib. I managed this with a 4mm end mill in a drill press. (A bit hairy, but worked OK).

Thread: Overrating a power supply for a DC motor?
22/10/2020 22:43:31
Posted by Hollowpoint on 22/10/2020 22:08:22:

Need some help guys.

I have a small DC motor I want to use on a project. The motor is 24v 200w and "rated" 11 amps.

11 amps will be at the rated output (11 x 24 = 240W). It will use very little current with no load.

Thread: Why is this guys mini lathe parting off so well?
22/10/2020 20:19:29
Posted by Philip Antoniou on 22/10/2020 19:55:36:
This is the parting tool that Arc recommended:

I have something very similar, and don't find it very useful - I do use it on a quick change toolpost for small diameter brass / ali or for cutting grooves.

I found this type much less touchy and more useful:

22/10/2020 20:11:44
Posted by Philip Antoniou on 22/10/2020 07:08:55:

I've ordered some taper bearings and upgrade gib strips as I've read that these help with parting off.


As another fairly inexperienced mini lathe owner, I'd say don't rush into changing things (especially spindle bearings) - there may well be bigger improvements to be made through set-up and technique.

In addition to all the advice above, I'd say to run the spindle as slowly as you sensibly can (maybe 150RPM or less), at least to start with. My lathe has a brushless motor (no high/low gear) which might make this easier.

Check your compound slide for play (grab the toolpost and rock it across the direction of slide travel and look closely at the joint between the two halves of the slide for signs of movement.

[The main issue with my compound slide was that the gib strip was rocking as load came on the toolpost, allowing the slide to lift. The problem (in my case, and I suspect many others) was that the gib adjustment screws were acting too far back from the sliding face of the gib for it to be stable (the gib is too thick for its height). This was compounded by the shape of the adjusting screw tips and recesses in the gib.]

Bolt the lathe down to something (with care to avoid distorting it) - this helped a lot with mine - see here

I might have gone a bit OTT with truing up the base, but it does help a lot. My parting at the end is still a bit hesitant, because I was expecting bad things to happen, but I've parted off 42mm dia free cutting steel and 80mm aluminium since without any problems. I do use a decent parting tool in the original 'lantern' toolpost for parting anything tougher than (say 20mm diameter) brass or aluminium.

Edited By Andy Gray 3 on 22/10/2020 20:12:33

Edited By Andy Gray 3 on 22/10/2020 20:13:31

Thread: Stuart Twin Victoria: Advice & General Questions
21/10/2020 17:08:23
Posted by Dr_GMJN on 20/10/2020 21:22:09:

Does anyone have reference images of real-life twin cylinder mill engines as inspiration for perhaps adding a few other details?

Thanks very much all.

I can't remember if it's twin cylinder or not, but the Stuart Victoria always puts me in mind of the mill engine at the Manchester Science & Industry Museum. Some nice pictures of details on the museum site, but no general view of the engine:

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