Part built Allchin 1.5 inch

[Jon LawesParticipant @jonlawes51698]

That's looking superb. I can't help but think if you are skilled enough to do that its not a big leap to do the boring etc.

By the way is Naim still in Salisbury? I work just over the hill in Amesbury.

[derek blakeParticipant @derekblake72550]

Hi Jon

That’s very kind, I just don’t have the right size lathe and to be honest I’m not totally sure how the bore should be and I’d the steam annulus needs boring into the casting before the liner etc.

Yes Naim is on Southampton road in Salisbury

regards

Derek

[Paul KempParticipant @paulkemp46892]

Derek,

I would second Jon's comments, looks like you have made a very nice job of the parts you have done, in a relatively short time too. Don't forget you don't have to mount the cylinder in a chuck or on a faceplate but you can mount it on the cross slide of your lathe to do the bore. If final dimension of the bore in the casting is a worry you can make it a nominal size and turn the OD of the liner to suit! Steam port drillings between the port and the cylinder can be fraught! I am just about to embark on that job on my 6" scale cylinder in the next week or so. I am planning to make a jig to assist in getting the angle right. As Jon says looking at the rest of the parts you have done you shouldn't have any trouble doing the cylinder, just take your time and think it through. Size of available machinery can be a problem but I managed to make the complete water pump for my 6" between a mini mill, Hobbymat and an ML7, where there is a will there is a way! You can put the £600 you save towards a bigger lathe for the next project!!

Paul.

[JasonBModerator @jasonb]

Unfortunately mounting on the cross slide and using a between ctrs bar won't really work in this case as the anulus needs to be bored out larger in the middle so that steam can pass around the liner and up to the regulator, apart from that it is a good way to do it.

If it can be done on a vertical slide then it is possible to move the casting up, down and sideways while the bar in spinning in the casting and produce a lobed anulus but needs care to not put too much of a cut on in one go. Or a boring head can be used as per the book.

Edited By JasonB on 04/01/2019 07:17:03

[derek blakeParticipant @derekblake72550]

Hi Guys

Many thanks for your comments, Paul your comments are very kind and I think you are right if I had the correct setup I probably could try and machine myself.

however if I was to attempt in on my small lathe id have to make up a fitting jig especially to hold some studs etc for clamping, nothing I couldn't do but as Jason says I have no movement for the steam annulus.

I just don't feel confident enough to risk ruining the casting, and with the work ive done on the trunk guide and front back covers I may reduce that £600 quote.

many thanks for taking the time to respond, I will update when ive moved on to the next stages.

Regards,

Derek

[derek blakeParticipant @derekblake72550]

Good afternoon

just a quick question, if I decide to try and bore the cylinder myself I’d at least like to understand how it’s to be done, looking at the attached drawing and the annulus, would some of you drill the steam port with the liner left out? I would imagine this would be safer so you don’t drill into it.

im not sure I will be able to set my lathe up to do it yet but it’s still interesting to know how things should be made.

Kind regards

Derek

[derek blakeParticipant @derekblake72550]

[JasonBModerator @jasonb]

I would drill it after the liner is fitter as the holes pass through both, as you will need drilling in from the ends you should not have any problems with the drill going astray.

Mill the ports before drilling then you can feel/see when the holes meet them rather than risk drilling too deep and joining up with the exhaust.

The hole up from the saddle and the angled hole to the regulator should be drilled before fitting the liner

[derek blakeParticipant @derekblake72550]

Thanks Jason that pretty much lined up with what I was thinking especially the holes from the saddle as these were the specific ones I meant.

Many thanks.

[derek blakeParticipant @derekblake72550]

Hi Jason

I understand how to bore a basic through hole but how do you bore the bigger hole down inside the core of the cylinder, is the adjustment made on the cross slide when at the correct depth?

Many thanks

[JasonBModerator @jasonb]

What method of boring are you intending to use?

[derek blakeParticipant @derekblake72550]

I think I’d have to clamp the cylinder to the crossslide I guess with the small lathe I have.

[JasonBModerator @jasonb]

If you set it op with what will be the rear of the cylinder facing the chuck then you can do the main bore with a between ctrs boring bar and also fly cut the end of the cylinder so that the cover goes on nice and true to the bore.

To do the annulas really needs a change to a boring head where you can put on a couple of thou cut and rotate the cutter round by hand then start the lathe and traverse along and back and keep repeating that which is the way Hughes suggests doing it in his book.

[Paul KempParticipant @paulkemp46892]

Derek,

This is a bit like watchmaking to me with the size of the cylinder! However considering that the actual diameter of the annulus is not critical within a few thou and the surface finish is also relatively unimportant your main considerations are making it big enough to get sufficient steam flow without conflicting with the drillings. If you don't have a boring head you could in a rough and ready way replicate Jason's suggestion with careful use of a four jaw chuck. If you mount a decent square shank boring bar in the chuck you can advance it with careful adjustment of two opposing jaws on the chuck. As I said a bit rough and ready but if you are careful and take it slow you can use Jason's suggested method of doing the cut and advance the tool in the jaws. There is another way of making a boring bar with a tool you can advance with a tapered screw in from the end under the toolbit but that would be more difficult with the small size of the hole. Half the challange (and fun) of making these things is finding a way to do it with whatever resources you have. I have had a bit to do with in situ machining to repair large Diesel engines and line boring of bushes on ships and steam engines in the past and it's surprising the results you can get with some really Heath Robinson equipment in terms of accuracy and finish!

Paul.

[JasonBModerator @jasonb]

I've just thought of another way it could be done.

If you change the boring bit of your between ctrs boring bar to a more pointed one you can gradually offset the tailstock a bit at a time which will make the tool swing a slightly larger radius. Then just proceed as with the boring head little tailstock feed, cut back and forth then put on another cut and so on

If you can't offset your tailstock or don't have a boring head to fit it then a home made centre in the 4-jaw can be offset instead of the tailstock as Paul describes.

Edited By JasonB on 07/01/2019 06:58:42

[JasonBModerator @jasonb]

The other method I mentioned earlier if the cylinder were on a vertical slide so that after boring to 1.25" you just move it up, down, in and out by 1/16" to get a 4 lobed cut would work quite well. I have sketched it out and there is very little loss of cross sectional area so a viable option. I suppose if you did not have a vertical slide you could do front and back at the same set up on the cross slide as the main bore and then rotate the casting 90 degrees and repeat to get the 4 offsets.

[derek blakeParticipant @derekblake72550]

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 KempParticipant @paulkemp46892]

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 blakeParticipant @derekblake72550]

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 blakeParticipant @derekblake72550]

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

[JasonBModerator @jasonb]

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 blakeParticipant @derekblake72550]

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 KempParticipant @paulkemp46892]

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 blakeParticipant @derekblake72550]

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.

[derek blakeParticipant @derekblake72550]

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.

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