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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: Steam Engine Number One
23/04/2021 09:09:32

These last few days / weeks I've been working on connecting the eccentric straps to the stephenson's link.

Not too many pictures I'm afraid, but..

Here are the bits

valvegear 18 stevensons.jpg

And them (temporarily) connected

valvegear 19 stevensons.jpg

I@ve found that the straps no longer run quite as freely in the eccentrics. Not sure why that is - possibly some grit or could be orientation. I will have to tidy that up.

Also in this series of workshop trials, I've made the nut that connects the upper eccentric rod to the valve gear.

valvegear 20 reversing nut.jpg

This was quite a complicated bit of work and here's what I did.

Firstly square up a piece of bronze. The final item is about 12mm square with the spigot being 12mm long and 6mm thick, but faintly curved along a 120mm radius. The centre hole for the axle for the upward part of the system is 4mm.

So I have a piece 12 x 20 x 20 (or so). My intent was to use a superglue chuck on a fixture on the rotary table. I figured that the longer the piece the better the adhesion. The stock was 2mm to high at the top and 2mm too deep at the bottom to provide a raft for holding and some excess on the top to clean off.

So with my squared stock I drilled and reamed a 4mm hole in the centre and did the same on my fixture plate (at 120mm out from the axis. A 4mm pin and a try square oriented the piece whilst the superglue set. Next day a light tap drove the pin out.

Cutting the curves (and try fitting as the width approach 6mm worked well. Next I took the length of the spigot to 12mm. This also worked well.

The I started to take the based down to 12mm and took too aggressive a cut and, 'pop' off came the piece from the fixture!

valvegear 21 reversing nut.jpg

And it was going so well!

I'd originally intended to cut the round edges on the rotary table, but I gave up on that idea and, having trimmed the remaining top and bottom and sides in the mill, I (rather gingerly) rounded the ends with a small file. It's not something clickspring would be proud of, but it's good enough for me!

What I found interesting, was that the nut no longer fit the slot in the reversing link. I think that this is because I squeezed the base to hard in the vice in and it mushroomed. However a few strokes of the file in the slot and it runs nicely now.

Next step is the valve chest and D valve. Once that;s done I can check that the bits fit together and I'm nearly there!

Iain

Thread: Boring aluminium - What am I getting wrong
23/04/2021 08:41:33

Another thing which caught me out, is that these brazed carbide tools seem to come unsharpened.

I had issues with boring with a similar head until I read this in the forum previously. Sharpening them on a green wheel and then touching up with a diamond hone from time to time has made all the difference.

I also found that if you don't tighten the grub screws up well, the tool tends to rotate, so even if you have it aligned correctly (as described above) after a couple of passes it's twisted out of alignment and rubs rather than cuts.

Iain

Thread: Steam Engine Number One
21/03/2021 19:19:00

Will our intrepid novice manage to cock up his reversing link for the third time? Will any more carbide end mills suffer?

Read on to find out!

So I had a good deal of advice on this. Firstly I made the meat of the link a bit thicker. Then I tried to approach the outside and the slot a bit more gradually. Finally, I ran my carbide mill at top speed!

I took a different and more daring approach to this build. I decided that, rather than bond the fixture and piece and drill my marks through, I would drill and ream them separately and bolt together - no superglue chuck for this boy.

I started by marking them out on a surface table - not that I intended to use this to drill - I have a DRO and I'm not afraid to use it!

valvegear 10 marking out.jpg

Here I am having reamed out the salient items on the piece

valvegear 11 the plate.jpg

I was delighted (not to say a little surprised) that all my pins could push through both items at once!

valvegear 12 plate and fixture.jpg

Here we are (again) aligning the item up on the rotary table at zero degrees.

valvegear 13 positioning.jpg

for the outline I used an 8mm carbide end mill running at 2200 rpm (thanks for the chance to try again Brett of ARC!). The first cut was 2mm outside the piece and 2mm deep, the next cut the same at a bit over 4mm to cut through

valvegear 14 first rought cut.jpg

I then took 2 passes each 1mm closer to the finish dimensions. There was a bit of rattle at the outside arc which is quite a bit outside the support of the rotary table, but the finish was still decent.

Having done this, I think cut the slot. first cut in 1mm increments down the centre with a 4mm hss end mill. Then two passes of 0.25mm to the finish dimension. According to my calipers the slot is 6.03mm wide so I made it 1 though oversized. Amazing!

valvegear 16 with corners.jpg

Here we have the raw piece, the fixture and the drawing and, finally, this is what it looks like after some tidying up on the belt sander and a bit of time with some 320 grit .

valvegear 17 done.jpg

The astute reader will notice that the slot is a little higher than the end holes and that the eccentric rod holes aren't central to the meat of the legs.

Despite that I'm very happy with this piece and AT LAST, I can move on to another part.

Iain

Thread: What Did You Do Today 2021
18/03/2021 18:01:41

Today I managed to puzzle my way through the worst Chinglish I've ever seen to find out how to set the top pressure in my compressor. Previously, it would run hit the end stop and keep running as the overpressure valve cut in. Take of a nasty plastic cover and turn the nut counter clockwise till it turns off a bit below 8 bar. None of those words being in the instruction.

Also grew my compressor tools skills slightly, but finally ordering a coiled extension with the right (Euro) connectors on. I now have an air gun by the mill and by the lathe.

That and a little bit of tidying up left me with a feeling of progress. I also started on the 3rd version of my reversing link and have yet to mess it up. Plenty of time yet.

Iain

Thread: Steam Engine Number One
15/03/2021 21:08:35

Thanks, Jason.

'For the outside radius I would use the full height of the cutter and take say 0.5mm passes and if that is OK go up to 1mm working in to the finished radius.'

Do you mean to cut 4mm deep (depth of the metal) but start 1mm outside the finished edge of the piece, or do you mean to cut 0.5mm - 1mm deep on the finished edge - hence 4 - 8 passes?

I think one of the problems was that when I saw that the carbide cutter was cutting nice, I cut to full depth (4mm + 1mm inside the aluminium fixture) which I think dragged the cutter into the work.

Iain

15/03/2021 20:12:20

This post will not cover me in glory, but the truth must out!

The task was to create the reversing gear (drawing a few posts back) which I was intending to do by mounting (superglue with tape method) my raw material on a long fixture, attach this to my rotary table and mill the outside through cartesian co-ordinates.

The idea is to drill / ream / mill the 6 and 8 mm locating / mounting / starting holes in X/Y co-ordinates and then switch to cartesian for the cutting.

My first attempt at this failed, mainly due to the superglue / tape chuck loosing grip (the tape side) and the piece slipping to the detriment of all.

I discarded this and tried again. This time I was going to bolt through the holes for the eccentric rods to keep it in place.

valvegear 04 on fixture alignment.jpg

Here we have the aluminium fixture plate pinned to the centre of the rotary table and the first locating hole used to align the X Axis at 0 degrees.

Now, I bought the steel for the link from eBay advertised as mild steel, but that may have understated it's toughness. two 8mm HSS end mills pretty much refused to cut it and both had to be discarded. Also from eBay or equally suspect sources.

So I bit the bullet and ordered some quality mills from ARC. The 3 flute carbide cutter cut well (given that the first pass of the top had already been done by Mr. Dodgy mill). However, part way down the second leg the part started to vibrate something rotten and inspection revealed that the end mill had sheared.

valvegear 06 oops end mill.jpg

IN a call with Brett at ARC he suggested that I was running this too slow and it was clearly user error, but despite this he is kindly sending me a replacement.

I carried on with a 2 flute HSS (again from ARC) which finished off nicely.

valvegear 05 milling the outside.jpg

You can see the roughness from the original end mills along the top.

Next step was to mill the slot. In this case, I chose to follow some recommendations from Joe Pie and pre-drill (in my case with a slot dril) before a finishing cut.

This wasn't terribly successful, there was a lot of vibration (even with the table locked) and I had to finish off the slot by widening a bit.

valvegear 07 milling the slot.jpg

valvegear 08 milling the slot 2.jpg

Given all that had gone on I was reasonably pleased. I'd abandoned the idea of cleaning the ends with the rotary table and filed instead.

And then I took another look at the piece - spot the error?

valvegear 09 spot the error.jpg

Indeed! the slot goes right to the end and there is no hole for the control handle!

Argh!!!

At that point I stopped for the night and a nice cup of tea.

Now I have a question. Ignoring various machining errors, it seems to me that there is not enough meat around the slot and possibly around the eccentric rod holes.

The design has 3.5mm above below the 6mm slot. That should be 13mm, but in fact it is 11.9. The slot is actually about 6.3mm and the lower meat is only a bit over 2mm.

The design calls for the meat round the eccentric rod holes to be 2mm.

Firstly, I think I need to pay more attention to how I mill this out. I think I should probably rough mill 0.5mm outside where I want to finish and then take a finishing cut.

Secondly, I think that the meat needs to be bigger. I think 4mm round the slot and 3 round the holes would be better.

Finally, of course, I should avoid merging the slot with the control handle hole!

I think I might have a go at this with just some aluminium plate to get my measurements and skills up to scratch and then try it again.

I'll also have a couple of goes at different ways of doing the slot.

Any feedback on sizes (or technique) would be much appreciated!

Iain

Thread: Bandsaw overhang
11/03/2021 17:23:13

I have a little block just the height of the underside of the vice, which I use to support the part being sawn, just past the saw blade. Generally works OK, but I like the other ideas!

Iain

Thread: Compressed Air
04/03/2021 16:30:33

My wobbler (1cc capacity? Maybe less?) worked rather nicely with a tyre inflator that came with a car. Would not do so well on a quarter size traction engine.

Iain

Thread: Carbide Tooling
03/03/2021 17:10:14

Thanks all.

Jason: Do you buy the cheap ARC tooling or the sumitomo?

old mart: Most of my problems came due to my 10mm collet being a bit oversized so anything would just fall out. I've now replaced the collet, which now holds a 10mm end mill OK when relaxed. But a mat is a very good idea.

What I'm trying to get my head round is how a part can continuously bash into a cutter at 20mph (interrupted cut) and that is good, but if you bump it at a snails pace it breaks. How can this be?

Iain

28/02/2021 17:43:45

I like carbide tooling. Even on my CMD10 (X1) micro mill I got good results - and better than with HSS.

On the big mill (Amadeel VMR32L), it's a joy.

The lathe (CJ18A), I'm more uncertain about, but the insert parting tool is a wonder (depending on material) and aluminium inserts work well on steel as well as ally.

So what's my problem? Well, for the main part, I buy cheap stuff from eBay. I have learned my lesson about the eBay title. A tool which says it's carbide in the title, often says it's HSS in the description. If it looks too good...

I also buy inserts (cheap end) from ARC.

What I find is that most of my tools chip if I sneeze too hard. There are some exceptions. I've some reground name carbide end mills which I LOVE that I got from ebay and seen (relativey) indestructible. Also some indexed facemills (also from ARC) which work well and so far haven't given me any problems despite being worked hard (blue chips and all that).

My (other) carbide end mills seem to have a short life. If the fall out of the collet, they chip. If I take too harsh cut they chip. If there's a hard metal (e.g. a bolt or screw) in the piece, they chip.

On the lathe, the aluminium inserts chip if they look at a piece - the nice thing is they seem to still keep cutting well even when broken! The steel inserts last a bit longer, but don't always give great results (depending on material). In fairness, I probably can't push the lathe hard enough to work them.

My question is this. If I spend a lot more money, with the tools be more robust? How much longer will they last. Yes I probably am a bit cack-handed, so that needs to be factored in.

Should I spent twice as much on a sumitomo insert from ARC? 40% more for an ARC carbide endmill (vs eBay) or 3/4 times as much for a kenametal (or similar).

I'm not arguing that more expensive is better, but I'm more concerned about robustness than wear. It the more expensive ones chip as much, then I won't get the benefit them them in their old age as they still retain their sharpness.

Iain

Thread: What Did You Do Today 2021
28/02/2021 17:17:29

Today, I finally finished off the air plumbing for my compressor.

I've really struggled trying to understand the various incompatible standards, sizes and options - and that despite helpful feedback from forum members in another post.

IN the end, my project approach was one I call, 'muddling through. I started off by buying a cheap 5m air hose. Turns out it had a 10mm diameter, so I started buying small number of bits and bobs to see how they fitted together.

Here's what I've ended up with:-

From the compressor to a pressure valve, water remover

air plumbing 00.jpg

I should be able to pull out the compressor to drain water from time to time and I still have access to the second outlet at the front.

This feeds a Tee

air plumbing 00.5.jpg

Whose left spur goes to a point on my bench, near my old and tiny CMD10 (just out of the shot on the left).

air plumbing 01.jpg

To the right, it first pauses by my rather bigger mill.

air plumbing 02.jpg

Sorry about the picture - it's hard to get a good angle on it.

Before pottering round the back of the mill and then the back of the shed where it ends up at a point for the lathe.

air plumbing 03.jpg

Almost as much effort was tidying up the shed so I didn't look like a complete mess. Sadly, but the time I got to the lathe, my tidying hormones had completely ran out, so the lathe is in it's normal swarfy state.

One of the biggest challenges was working out how to hold the quick release points. A kind member suggested I mount each point with a drain valve to clear any excess water. I have done so, though in hindsight I wonder how much value that has with my rather sparse usage. Still, sometimes I like to do things 'right'.

I tried 1/4 BSP T connectors, but couldn't work out how I would mount the (without quite complex machining), so ended up using 4 way connectors (cross shaped) which I set into some milled ally pieces with a plate on top (said plates sliced out of a block with the slitting saw mentioned a few posts back)..

There's no apparent leakage and all points work. Unusual that something works more or less first time!

Iain

27/02/2021 20:32:21

Hi, Nigel. My table is 8 inches and there is still an inch of overhang. I think it will be fine though.

I've just used the arbour again to slice some 40 wide mm aluminium into 4 mm slices. With some luck I may show the results tomorrow!

Iain

Thread: Collet Chuck for my CL250M?
25/02/2021 18:06:48

I would be most keen to know more about Danny's widget (even the Howard version). Dropping nuts as I attach a chuck is a kind of hobby of mine. One I'd like to drop!

Iain

Thread: What Did You Do Today 2021
25/02/2021 18:05:20

Thanks, NIgel.

The sticky tape and glue goes as follows. Clear well both parts. put some masking tape (I went out and bought some blue philips because someone said so, but it turns out that was what they had not what was needed) on one both surfaces. Apply super glue to the non-sticky side that's up. Push the parts together (tape to tape) and let it set.

It's a variant of the superglue chuck, which is a variant of the wax chuck. I like the tape version (in principle) because you don't have to heat up the parts to break them free. In this case I suspect that the part got warm with the milling - or perhaps I should have taken a lighter cut. Who knows. But I think it's fine to drill / ream with and hten I can bolt it together

I do have a rotary table and started of by mounting the plate on some scrap aluminium and drilling / reaming / slot drilling some registration holes as can bee seen below

valvegear 03 on fixture.jpg

As you can see I'm a measure once drill twice sort of guy ....

I've cut another blank and we basically get to the same point and then I will bolt the two eccentric rod holes firmly to the ally. My other challenge is that the centre of the MT3 spindle and the centre of rotation of the table are not in the same place. We're talking 2 or 3 thou here which not going to affect this piece, but it's nice to be try and get it spot on.

The arbour cap has a 22mm protrusion onto which the slitting saw fits. This slides into a receiver on the main body and the two are clamped together with a cap head bolt in a counterbored hole.IN effect there is the same clamping force as on one of those arbours which are far too long and with a long thread protruding with a massive bolt.

This may make a bit more sense.

slitting saw arbor.jpg

Iain

Thread: Replacement lathe lamp suggestions?
25/02/2021 14:06:39

I have a couple of clamp LED lights which came from B&Q for around a tenner each.. They clamp to the shelf above the lathe and give a good light. May not suit you, of course!

Iain

Thread: What Did You Do Today 2021
25/02/2021 13:54:34

I've watched a lot of Joe Piezinski recently and find myself in awe of his pins - the metal bits not his legs, though no doubt they are fine too.

A quick tour of the usual supplies indicates that getting a suitable range of precision pins would require a moderate mortgage - and 0.01mm precision or better is not in my dictionary!

So I bought some silver steel (which seems to be generally ground 1 thou under nominal dimension), cut to size, trimmed in the lathe (with surprising accuracy!) and chamfered...

pins.jpg

This is scarcely what did I do today as it harks back to before the cold kept me from the shed (and camera), but here is a snap of my low profile slitting saw arbour (again inspired by Joe, though I think Quinn's done a you tube on it as well) in action.

slitting saw holder slitting.jpg

Finally, I have been attempting to mill the reversing link for my steam engine, which is not going well. Mainly because my masking tape and superglue arbour failed and the part got ruined. I need to start from scratch. Still at least it's almost warm again so I can actually get back in the shed!

Iain

Thread: Collet Chuck for my CL250M?
23/02/2021 17:17:01

I bought an MT3 ER32 collet chuck for my REal Bull CJ18A and it was horrid. The run out was bad. I bought another one. It was just as bad.

I then bought an ER32 collet chuck from ARC which fits on the chuck backplate (that may be the wrong word. The bit of the spindle that the chuck bolts to) and have been delighted with it.

Iain

Thread: Building a small bench
23/02/2021 17:13:54

I don't have any answers for you. I've built my benches out of 2 layers of 18mm marine ply on (mainly) 4x4 wood legs.

What I've done wrong is not to have treated the wood with oil or varnish or something. I'm not sure what the right treatment is, but it's certainly not nothing. My main bench is now rather dirty and it won't come off.

Iain

Thread: Looking to learn CAD
19/02/2021 16:08:56

I am an amateur with no CAD background.

I tried quite a bunch of 'free' tools but found the learning curve daunting.

What I've ended up using very happily is an online product called OnShape (OnShape.com) which is relatively easy to learn and use, capable of great sophistication (comparable more or less to the likes of Solidworks and other top end tools) and is free to use.

The drawback is that it's only free if your designs are visible to the public. I don't embarrass easily, so it's OK with me.

My current work in progress steam engine (see https://www.model-engineer.co.uk/forums/postings.asp?th=139184) is being designed in that, and I can even to animation to see if the parts fit (sadly, the don't do so all the time, but it's easy to sort out!). At the other end I can knock up a toolholder stand in a few minutes, download the STL and print it.

One of the nice things about it being 'online' is that you get updates pretty much weekly without complicated installs. I should say that I've barely touched 10% of what it can do.

OH and they have a decent help forum and documentation

Iain

Thread: Workshop/Garage Insulation/Space Heating
11/02/2021 16:33:26

I have been using a small electric fan heater to bring cool up to bearable, but I've given up for now.

Partly, it's not man enough to take -2 up to something bearable. However, more so because I noticed that I was getting A LOT of condensation on the bigger machines. They just don't warm up. Particularly the rotary table was attracting some rust.

What I really need is an attached double garage with central heating, or a decent cellar.

Perhaps the next house.

Iain

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