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Member postings for Iain Downs

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

Thread: Big lumps of Cast Iron
26/03/2020 21:46:19

I think Metals for U also do cast iron in large sizes.

Iain

Thread: Screwcutting on the lathe
23/02/2020 17:08:45

Right. So, the first thing I did was to take Mr JOhnstone's advice and re-think my thread size.

I've got some 10mm x 1mm taps and dies and made a 10x1 nut and bolt as standards.

The lathed bolt was OK and fitted in the tapped nut nicely.

The lathed nut was a bit wobbly so I'd clearly over cut, but I thought it worth having a go with the part I'm trying to make (piston gland).

The nut for the piston gland (external thread) went OK despite having to turn the thread up to a corner.

The gland itself was more daunting as I had to thread it up to an internal corner.

The idea was to cut it up to the rough depth and then try the nut, cut a bit more, try the nut and so on. Not terribly professional, but then I'm not.

I found I was tapping much deeper than I should and the nut still wouldn't go on. I also started to loose track of the depth and at one point the half nut slipped and I had to find my way back into the thread. I also noticed that the QCTP had slipped a bit so that wasn't helping.

In the end I tried a little harder to thread the nut on and - hallelujah! went on. Wobbled a bit, mind you but I thought I was there.

Unfortunately, when I tidied the internal thread up with a light touch from a scraper the nut stopped screwing in and started pushing in.

I think I have to scrap that part and start again. But not tonight - there's only so much I can take!

The lesson seems to be to be a bit firmer about trying the nut - and I might make a non-hardened thread cleaner - a sort of poor man's tap as my try nut. The idea is that it will both try the fit and clean up the threads a bit. Sort of tap profile, but in mild. Or if I go mad I might have a go at making a tap. I have some 20mm silver steel I could cut down. We'll see - all these digressions take away from actually building things!

Thanks for all the help so far. I'll post again when I've had time to try again.

Iain

Thread: Upgrading to Stephenson Gear
23/02/2020 16:56:30

Thanks to all for your feedback. I shall have a think!

Iain

22/02/2020 20:57:39

Regular readers know that I'm in the (slow) process of building a (mainly) self designed vertical engine of about 2 inch bore.

Originally my idea was to do the least possible and then upgrade bits once it works. So I have a simple eccentric in my design with the idea of upgrading to Stephenson linkage later.

However as I approach the point where I can see eccentrics on the horizon (and not just in this forum!), I'm starting to think it would be easier to design and build it in now.

As I understand it, I need to run 2 eccentrics which are 'out of phase' each attached to a bar with the slide valve attached to a slot which it can be moved along to go from full forward to full reverse (with a bit in the middle where I guess it does nothing at all).

I have an assumption I want to check and a question to ask.

The assumption is that the lead of each eccentric must be set individually, that is they two are not (for example) 90 degrees apart but 90 + 2* lead or something like that. At some point I will be asking for help in understanding how to optimise the lead angle, but not today! So the two eccentrics need to be fixed individually to the crank and not fixed together. It would be easier if I can fix them.

The second question is if the attachment to the expansion link affects the throw of the eccentric. In fact I think I've answered this. In my book (Valves and Valve Gear for Steam Locomotives by Lake and Reidinger) the first pictures I saw (47) had the slot to one side of the pivots for the eccentric links. This would mean that the spindle would move a little less than the eccentric.

However Fig 58 shows the slot above the pivots so the range of motion will be the same.

Any Internet resources (or plans I can copy find 'inspiration' in) would be most welcome

Iain

Thread: What sort of things inspire you?
22/02/2020 09:33:51

I like the idea of 'models' that can actually do something. So my current attempts to build a large model / small reality vertical engine.

Once that is done (in some decade in the future) I am toying with either a clock or a watchmakers lathe. Which will disappoint the OP of the converse post, no doubt. I had a bit of a flirtation with the idea of a watch, but, having watched (sorry) some You Tube videos, I suspect is beyond my competence - my manual coordination is not the finest.

I also want to do some casting at some point, but lack the space and facilties.

My final 'inspiration', I suppose, is some jewellery for SWMBO. Perhaps that might soften her heart towards the Art...

You will notice a common theme in all of this. I'm inspired by things I've never done, don't have any evidence of the skills required and which are rather hard.

Perhaps I'm not alone in that?

Iain

Thread: Screwcutting on the lathe
15/02/2020 10:28:07

I just realised. I've had lots of good advice on tidying up an external thread (files etc), but how do I tidy up an internal thread?

Iian

13/02/2020 17:00:40

Here's the thing. I want to make a steam gland with the insert having an 18mm external diameter screwed into a larger piece (25mm from memory). I've decided to use 1.5mm pitch for the thread.

Apparently this is a spark plug thread so I could actually buy a tap and die set for this. But I don't want to (a - I'm cheap and b) I want to learn how to DO this!).

I'm practicing on 10mm bar because a) I have some and b) I have some (professional) nuts and bolts which fit this.

Once I find I can make an internal thread which matches an external thread, then I will whoop with glee and stick some 18mm bar in the lather and make the actual piece.

5 bob well spent!

Iain

12/02/2020 21:21:02

Thanks for all the comments guys.

It looks like the weekend before I get back in the shed, but I will have another go at a 10mm bar and then work on an internal thread to match (shudder). If that all goes smoothly, I will thread the piece that I actually want to make!

Iain

Thread: What Did You Do Today 2020
09/02/2020 20:07:45

Yesterday was the 'York and District Mode Engineering Society' Auction.

Apparently I was clearly a new boy owing to the amount of stuff I bid on. The 15mm Carbide endmill (11 quid) was nice, but my star purchase was a Clarke Turbo 150EN MIG welder at £30.

A mig welder has been on my wish list for some time, but other things have been higher up. The Clarke ones seem to be almost universally regarded as the best in the hobby price range.

When I got home, I discovered 3 things. a) the welder (machine) is quite good. b) the welder (person) is not. c) don't try and weld with the fan heater on. It seems that a 2kW fan heater and a Mig welder don't play nicely with a 13A fuse...

Iain

Thread: Screwcutting on the lathe
09/02/2020 19:50:00

Right now I am totally at a loss. And apologies for the gap - a new mill got in the way.

I had another go.

The first thing i did was to compare the cutting tool against an M10 bolt (1.5mm pitch).

threading tool against m10.jpg

Apologies for the quality of the photo - it's one of many things I'm no good at!

by eye and even here, the tool matches the profile of the thread quite well.

Then I set up the lather to screw cut - centre in the headstock and all.

threading setup.jpg

Then went straight in. None of this angled nonsense.

What I found was that at 0.9mm or so a nut would not go on the thread. this is the theoretical depth of the thread. I kept going in 2 though (0.05mm) increments. The first point at which the nut would go on was at a depth of 1.3mm.

Even at that it was a bit of a struggle. And when I ran a M10 die over it there was still swarf coming off.

So. It looks like I've misunderstood the various postings and I need to cut about 1.3mm deep not the 0.9mm I'd understood from reading).

Incidentally, applying O Level maths the depth of a 1.5mm wide 60degree angle triangle works out to be 1.299mm - roughly in accord with what I've found.

The other thing I found was that I was cutting in increments of about 2 thou (0.05mm) all the way up from about 0.8mm or the lathe would stall. Even at that I hard to run a little faster then I was comfortable with (250 rpm) to be sure to get the cutt - which meant more of a struggle to get it to stop at just the right place.

I remain confused about why ALL the books I've read on screwcutting seem to miss out the the depth calculation as it it were easy.

Any advice welcome - as always.

Iain

Thread: Steam Engine Number One
02/02/2020 17:49:50

The latest addition to the Steam Engine parts is the bottom cylinder plate. This supports the cylinder, holds the piston gland and will be supported by 4 columns from the base.

Starting off with a piece of 100 x 130 x12 EN1A.

bottomcylinderplate-plate.jpg

This superglued to my base plate and then skimmed - as well as wanting to get it flat, the plate is also 12mm and needs to be 10mm - Metals4U had no 10mm in stock.

bottomcylinderplate-facedok.jpg

Next, to mark the position of the holes required for the pillars using a transfer punch

bottomcylinderplate-transferpunch.jpg

And then complete the marking out - the bearing block isn't exactly central so I bodged what will be the centre of the cylinder a fraction to the right.

bottomcylinderplate-markedout.jpg

Next to mill recesses at the top and bottom, drill 8mm for the support columns and a centre drill in the middle which will be used to locate the piece on a wax chuck to turn down the outside leaving a spigot for the cylinder to locate.

bottomcylinderplate-recesses cut.jpg

ACtually, the drilling didn't work so well. I was trying to line up the centre drill with the punched dot by eye and I'm not convinced I managed it at all well.There was quite a bit of vibration at the start of all the holes, though I'm also wondering how accurate the chuck that came with the mill is. Something to investigate another time.

Now to try and make it look a bit less rough. To round the corners off at (I think ) 15mm radius.

How to hold the plate on the rotary table? After some thought I found a MT2 stub which I'd used earlier that I'd tapped 10mm in the centre. Actually, I suspect it was only mainly in the centre, which led to the corners not quite coming out as I expected - or the holes are more off from the punched dots than I thought.

bottomcylinderplate-centering.jpg

What marvelous things co-axial indicators are! You can see the MT2 'blank end arbor' fixed into the table with an M10 bolt and being centred nicely.

Then attach the plate at one corner and turn!

bottomcylinderplate-rounding.jpg

This worked surprisingly well, though I had to have two goes at it. The first time I'd not tightened the drawbar bolt enough and the MT2 slipped.

Oh you may notice that the guard has gone. Simply put it stopped the piece moving sensibly. It was encouraging to know that I can take the guard off just by slipping it out and the microswitch defaults to 'closed'. Obviously Weiss expect this! Not sure if I'll bother putting it on, though I will re-evaluate next timing I'm facing with the 63mm face mill which chucks hot swarf EVERYWHERE!

This is the final result of the milling

bottomcylinderplate-milled.jpg

And with the cylinder more or less as it will be

bottomcylinderplate-withcylinder.jpg

The next task for this piece is to mount it on the lathe and skim off all bar the centre spigot to locate the culinder. Also to bore the hole for the piston gland. Thinking about it, though I think I need to make the piston gland first so that I can try fit it. the way I'm thinking I need to make the gland may not be as accurate as I would like - so that first, then complete the plate.

It's starting to feeling like at least the end of the beginning!

Iain

Thread: Superglue chucks
01/02/2020 09:28:33

Thanks NDY.

The time period was mandated more by the lengths of episodes of House than any scientific approach. I've been working on the 1 hour per inch which I've read in this forum when soaking metal.

However, it would be nice not to have to wait for an hour or risk the wrath of you know who if there is a smell. So the Blue Scotch Masking tape is an approach I would like to experiment with. Or beige b&q masking tape if anyone thinks that will work.

Iain

31/01/2020 16:36:11

The heavier hammer was, naturally, my first thought. But the glue was too strong - or I was too weak.

I tried the testing approach, but I'm not sure what my results meant. I started at 110 centigrade and after an hour tried to knock the part off sideways. Didn't move. Then another hour at 140. Also didn't move, but when i lifted it, it came off fairly easily. So 110 might have worked if I'd levered it up.

I will however, try the blue scotch masking tape approach which seems to be much less cumbersome - does anyone know if colours other than blue or brands other than scotch will also work? My local B&Q doesn't stock it.

Iain

Thread: I my goodness
31/01/2020 16:29:45

45 quid though.

Iain

Thread: Old Computers - why do people bother
31/01/2020 16:24:42

Oh and they were probably faster as well despite the 3 orders of magnitude of performance gain of the hardware.

Signed

Bitter Old Techie.

31/01/2020 16:23:49

A Thumbs up for Ron.

I have 'virtual' machines going back over 20 years - just in case I have to fix something I broke in the dawn of time (I was / am a sort of software developer).

All running on a machine that's *only* about 8 years old.

There is a con here. The word processor I was using in (say) 1985 did all the things I needed, as did the spreadsheet and presentation tool. Just what real value has the last 35 years brought?

Iain

Thread: New computer possibly required
31/01/2020 15:23:21

you can use the free SeaTools to test the disk. this seems to work on non Seagate drives as well.

I would endorse Martin and Old's idea - to get a cheap (ish) SSD and clone. No only will your hard drive work again, but it will feel like you have just bought a new modern PC - everything will seem much faster!

Iain

Thread: Superglue chucks
26/01/2020 19:31:55

I've been using superglue wax chucks recently (mainly on the mill) and it works well most of the time.

The first couple of goes I tapped the piece from the side and it came off nicely. Not happened since.

Now I use heat. Specifically the oven, but I suspect I'm overdoing it. I've been running the oven at 200+ centigrade which certainly does the trick, but it stinks (and SWMBO isn't keen).

I'm struggling to work out how hot it should be. I've used a blowtorch and the oven, but suspect I'm overdoing it. I like the idea of the oven (particularly for big parts) as it is more controllable.

Iain

Thread: Painted T Slots
26/01/2020 11:22:18

The consensus seems in favour of removal. But is it best to use paint stripper (and do I need to consider the type of stripper) or scrape? Scrape has been suggested, but that sounds like a lot of work and of course impossible to get into the slot proper...

Many thanks.

Iain

26/01/2020 09:55:41

I recently bought a new mill (Amadeal VM32L - pretty much like a WM18) and it came with the T-Slots having a thick layer of paint.

So thick that the T nuts had trouble entering the slot. A mild bit of brute force sorted that out, but of course the paint is chipped in places.

I wanted to ask if the paint had any real value. I imagine the idea is to prevent corrosion, particularly in the parts of the T you can't easily get to to clean.

However, I had in mind to use the slots for lining things up. There was an article in one of the mags recently about a vice aligner which I quite fancied.

I might also add that this mill seems to attract condensation more than my CMD10 did, though it's hard to compare like with like.

So, should I strip the paint off to expose the metal? If so what kind of stripper should I use?

Or is the paint a necessary protection?

Thanks as always.

Iain

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