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Part built Allchin 1.5 inch

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derek blake07/01/2019 09:37:29
327 forum posts
97 photos

Many thanks Jason and Paul, I will mull over it all later and see if anything can be achieved.

my lathe would need a clamping jig made as I have no t-slots, but I could make a plate that fits over the tool clamp.

Thanks

Derek

Paul Kemp07/01/2019 11:00:18
283 forum posts
9 photos

Derek,

Given the 'non critical' nature of the annulus if you used Jason's 4 lobed method you could always use a small rotary burr carefully and gently after to clean down the high spots if you are concerned re any reduction of CSA.

Paul.

derek blake07/01/2019 11:09:59
327 forum posts
97 photos

Hi Paul

Its all very interesting, I need to take it all in and understand what the process would be and if I can clamp it to the cross slide.

I have to admit its giving me a lot more confidence to try it myself.

Regards,

Derek

derek blake07/01/2019 15:35:36
327 forum posts
97 photos

Sorry just another quick question, id like to make some valve glands but I cant find Gunmetal bar to buy, is phosphor bronze the same thing and be OK to use?

Thanks in advance

JasonB07/01/2019 15:51:30
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A nice bronze to machine is SA660 which can be used for bearings, glands etc.Should be able to get it from the ME suppliers.

Regarding the 4 lobed method restricting flow, you will get 68% of the original area but as this is almost twice the combined area of the two holes up to the regulator chest it should not be a problem

derek blake07/01/2019 15:56:42
327 forum posts
97 photos

ok thanks very much Jason, for answering both questions.

I was looking at the bore and I think the first task I will set myself is seeing if I can even clamp the casting to my small lathe, I mat have to make a plate up first.

then I will make a between centres boring bar and do the size to drawing all the way through, then look at add in the annulus part after.

if I can do a good bore in the first place I think I will be far more confident to do the next stage.

Regards,

Derek

Paul Kemp07/01/2019 19:51:58
283 forum posts
9 photos

Derek,

Just a thought, when you set it up try and clock it to the saddle radius so you ensure the bore is parallel to the boiler and square to the crank. When I did my 6" I had the luxury of using a horizontal borer so I was able to machine the saddle radius and the bore at the same setting guaranteeing they were parallel. We had the problem with my mate's full size Avelling which had a new boiler and the boiler maker didn't get the cylinder seating rivetted on true - lots of fun trying to correct that! Good luck, you will be pleased you did it when you have done it lol.

Paul.

derek blake07/01/2019 20:58:21
327 forum posts
97 photos

Hi Paul

I’m not ignoring your message but want to show you all this annoying flaw in my casting, spent 3 hours machining and a hole appeared in the liner, I guess it’s scrap?

There’s a valley in the middle I guess from this hard spot but possible I could take bore slightly bigger to take this away but I’m guessing there’s no way around the hole which will open up completely once the outside is machined.

So disheartening.7fad2302-1709-470f-bb18-3b8781d48fe3.jpeg

derek blake07/01/2019 22:04:43
327 forum posts
97 photos

There is actually 5 other little pits inside the bore, sadly this was a casting from an online auction so I will have to buy another new on sometime.

Paul Kemp07/01/2019 22:56:33
283 forum posts
9 photos

Derek,

Ooops! Sadly a hazard of the hobby. I don't think I would bother with another casting but get a lump of cored bronze of the right proportions and chew it out of that. You can get cored bronze in various O/D - I/D combinations and it will almost certainly be cheaper than a casting from a model supplier. I have bought from metals4u in the past, they sell by the inch. Doubtless there are other sources. I think I would bore the block first and then turn the liner to suit, needs to be a good fit so steam can't leak from the anulus, you probably need around a thou to thou and a half interference fit on that size.

Paul.

derek blake07/01/2019 23:25:05
327 forum posts
97 photos

I think Jason said Sa660 is a good bronze to machine, so I will look to get a piece ordered.

Thank you

JasonB08/01/2019 06:55:53
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Agree with Paul it will be better to use hollow bronze, M-machine are another source and Macc who advertise down the right of the screen

derek blake08/01/2019 08:00:27
327 forum posts
97 photos

Thanks Jason, will the SA660 be ok as I’ve found sound.

Regards

Derek

JasonB08/01/2019 08:07:57
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Yes that's fine for cylinders and liners as well as your other small items, the LG2 from M-machine is OK for the liner

Edited By JasonB on 08/01/2019 08:22:03

Keith Long08/01/2019 12:39:22
782 forum posts
10 photos

Just a thought after reading this thread that might help Derek.

As you've now got to machine a liner from scratch, would it be feasible to machine the cylinder casting right through at the bore of the designed annular space, and then machine the liner with ends that fit the larger bore but with the centre part waisted down a bit to make the annular steam space. Having a uniform bore through the cylinder casting would be easier than trying to machine the recess and machining the liner od down locally is just straightforward turning.

derek blake08/01/2019 12:53:52
327 forum posts
97 photos

Hi keith

I think I'm with you, basically put the annulus onto the liner.

the width for the liner should be 1 1/4 inch so increase this by 1/16. then turn a annulus in the liner 3.1750 approx. deep all the round obviously.

Regards,

Derek

derek blake08/01/2019 12:57:00
327 forum posts
97 photos

it does sound a much simpler way of doing things.

JasonB08/01/2019 13:08:53
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But it does mean the cover stud holes are being drilled right on teh joint line rather than going into solid metal.

Annulus is 1/16" each side so would need to be increased to 1 3/8" which is the same as the PCD of the studs

derek blake08/01/2019 13:23:26
327 forum posts
97 photos

do you think this would weaken anything? id imagine as the liner is a tight fit in cylinder the fixture would be pretty tight.

derek blake08/01/2019 13:36:39
327 forum posts
97 photos

Hi Jason

So are you saying liner would need to be 1 3/8 wide instead of 1 1/4 but with the 3.2mm deep annulus.

I would them bore the cylinder to 1 3/8 to match liner ends.

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