Stuart Twin Victoria (Princess Royal) Mill Engine

A simple pin set on centre line of the arc and another in the cylinder wall will locate the feet accurately enough while the JB sets, though I was underr the impression the mating area was going to be machined too.

Yes another way this op can be done, but as Jason says it would be best to machine the lower surfaces after bonding - done with the cylinder held on a mandrel the dimension would be both identical over both parts and importantly parallel with the cylinder bore too

You can make a simple 'tween centres boring bar of any size you want to suit the job. I have some made many years back from silver steel. They have a small flat on them where the cross hole for the 1/4 HSS cutter goes. By making the hole blind the flat area can be drilled and tapped for say a 6ba screw which helps move the cutter when very small movements are required. Remove screw, mic across flat and tool tip - simple maths gives the radius. There are other ways - inset adjustable carbide tips for instance but that above has served me well for a long time now - I much prefer to use 'between' centres for bores to eliminate taper.

Soft solder will be sufficient!

Ramon

This pic should help explain it better. The turned portion is to ensure the diameter is true to the axis of the centres.  Radius required is dimension plus .462 across tool tip and flat

Edited By Ramon Wilson on 11/11/2020 08:52:42

Yes just soft solder them together for machining.

As Ramon says a between ctrs bar is easy to make, mine are not even solver steel.

Thanks guys.

The setting up of the cylinder and feet is a challenge. I'll have to re-read the article. The plane of the feet faces has to be parallel to the nominal cylinder axis, and the valve face at the top, and they have to be aligned laterally with the cylinder axis. Also, so that when the cylinder is bored, and the valve face and feet are finally machined, they are the same thicknesses, and the cylinder walls are consistent.

I suppose the boring would be done last, resting on the finished feet. Then the valve face would be machined in the same way, parallel to the feet?

It's not so easy. I can imagine getting everything done nicely, then finding the cylinder is offset in the casting. I suppose the final boring could be done to the best-fit in the cylinder casting, but then the cross-slides would have to be adjusted to suit. That sounds all sorts of wrong.

Ramon, can you direct me to where the cutters are for the bar please? I'd prefer to use carbide inserts. Is it a round section tool holder that would fit into the cross-hole?

You will be hard pushe dto find an insert holder to swing that small a radius, A piece of 3/16" dia HSS would be about the right size, maybe upto 1/4" dia. Old ctr drill or milling cutter shank will do nicely. I do habe an insert tool but that goes into my little 35mm dia bar

There are three ways to go with the cylinder. 1. bore it out and face the piston end first then hold it on an arbor to machine the feet and port face. 2. Machine the feet, then portface on the mill before setting up on the cross slide to bore the cylinder. 3. Bore and face then set up in the mill using the face as the ref to do feet and portface.

A good range of bits there; if you don't mind me asking, who was your local supplier?
As you know, I'm not far from you myself.

Bill

Well Doc, we all have differing ways to approach this subject and getting the feet true and parallel along with the valve face is critical as you surmise. Cat skinning is to the fore on this one.

Personally I always do the bore first then use that as the datum to bring all other surfaces including the ends true to it - take a look here post 28 onwards or this one here post 24. The latter a much more complex casting for getting several surfaces and axis truly in relation. It's down to choice but I have always worked on the basis of what ever op is being done it should, if possible, lead to an accurate means for doing the next. Pays, money choice etc.

I use HSS bits in my boring bars - somewhere though I have no idea where I have a few carbide tips set in a holder similar to Jasons but the tips are not replaceable. As said before I use discarded throw away cutter shanks for such purposes - excellent material and easily ground. I broke a 1.5 mm one this afternoon - the shank went straight in the cutter tin.

You are seeking advice on here and you will recieve much - it is down to you to decide which suits your purpose best and choose accordingly. I offer mine based purely on my own previous personal experience which I hope will be of use - if not to yourself then perhasp some one looking in.

Regards Ramon

PS Cut short by tea time !! I have more cutter shanks than I require - if you want some just say so and I'll send you some.

Edited By Ramon Wilson on 11/11/2020 19:22:04

Thanks Ramon, I’ll fully digest all that later.

What I’m trying to do is get some options together and go with the one(s) I feel most comfortable with. I stuck the 10V cylinder in a chuck and bored it out, simple! I know a between centres approach is probably better for these longer cylinders, so I’ll go with that despite it being totally new to me. I suppose fear of the unknown, and potentially scrapping a casting. Having said that, one of the 10V Cylinder faces was a bit out of true, so even that wasn’t so easy!

Boring the cylinder first makes sense. I can put a mandrel in it and use that to get the axis, and offset from that vertically and horizontally for subsequent operations on the valve face and feet. I guess for the initial boring operation I could sit the casting on the cleaned-up valve face?

Thanks for the kind offer of the tools. I do have some scrap milling cutters from my first attempts at milling earlier this year! Thanks anyway - I’ll see how I get on.

Yes, it’s Metals Procurement in Rotherham. Mark is the owners name. I think he is an ex steel works metallurgist. He knows his stuff and is very helpful. I did ask him if many customers are model engineers. He said that many years ago he put an advert in a M.E. Magazine and was inundated with requests for tiny amounts of material! I guess predictable, but I don’t think he bargained for the amount of calls. He said he still gets calls from the same advert - these people don’t throw magazines away! There are a few bits of round bar he couldn’t get, but the majority was no problem. The fact he’s only about 20 minutes away makes it very useful too! The whole lot shown there - stainless, silver, mild, aluminium, brass, gunmetal, cast iron) was about £70/£80.

You are at what I was faced with 45years ago - early days, so much to learn, so much to take in. The major difference of course was that the only way I could get help was via a monthly model club meeting - I well remember going from person to person asking if anyone could help me with trying to cut a thread on silver steel - each in turn referring me to someone else. Finally I gave up getting nowhere and struggled on with this most trying of machining but it would be quite a few years before I realised that the persons concerned probably didn't actually know anyway.

I became so enarmoured with machining I gave up a lucrative offshore career and retrained as a milling machinist. From that point on I until I retired I worked in three 'jobbing' shops and one in a factory environment, building up and running a machine shop. In all that time I never, save one item, machined anything that I couldn't lift on the machine myself. Every day was different in the jobbing shops and as you can imagine it was a steep learning curve - time is money and mistakes highly unpopular.

I say this because I have seen both sides of the fence - first as a rank amateur and second as having to earn a living. I have not forgotten how difficult it is to find your way in the early stages of ME hence my interest in helping those in similar circumstances but there are always many many ways of going about something - some good some not so - but the choice of how is very much down to the individual.

So, with regards to the cylinder - if the bore goes in first then yes you do need a good datum face and yes the ideal one is usually the valve face. (that face should not be taken down to finished dimension at this stage - merely cleaned up flat) Once that bore is finalised then all other faces are brought to it ideally by holding on a close fitting mandrel (not like the cylinder in the first link where it can sit slightly off set). It's far easier to check these faces to the bore and have time to make allowances if not quite right than by finding your bore is out to them if machined first and the only way it can be rectified is by making it larger, possibly having to sleeve it.

Expanding mandrels are very easy to make - they can be held in a chuck but if the back face is faced first and drilled and tapped it can then be bolted square to an angle plate if transfering to the mill is required and you don't have a means to support the chuck eg dividing head.

The discarded cutters I have all have 6mm or 1/4 inch shanks - offer's still open if they suit your purpose

Regards - Ramon

Edited By Ramon Wilson on 11/11/2020 23:21:44

Cheers for that, see also Phoenix Steels in Attercliffe for silver and tool steels, Canal St just off Effingham Rd.

and also AMB for stainless and alloy; their yard prices are better than the web prices; again not far away, a non descript gate on Washford Road.

Bill

Thanks all.

Thinking about the between centres boring bar: what’s the most accurate way of centering the ends, assuming it’s too large a diameter to fit through the spindle?

Ive not done anything between centres before, but I do have a drive plate/carrier. Should I mill a flat on the end for the carrier?

I realise at the moment there are a lot of questions and no progress on the model - I’m trying to get things worked out and tools ready before starting. The drawings for the bases are done and I have the material for them, they will be started first. Just waiting for the JB weld to arrive.

When i bought some JB weld they had various ones on the shelf. This one was rated the strongest, but not sure as it is the 1st time i have used it. It was the figures they gave that prompted me to go for this one.

Steve.

If the bar won't go up the spindle its best to use a fixed steady if you have one. If not insert it in the chuck as deep as it will go and nip up but not over tight. Gently tap the outer end to tweak the concentricity - it's not that important as long as it's reasonable - and gently start the centre drill - once it has a start then drill as normal. Reverse and do the other end and yes ideally mill a small flat for the carrier. Set between centres and where you intend to have the cutter placed turn down the minimum to achieve a concentric surface about an inch wide. Transfer to the mill for the cutter hole and grubscrew hole - as said before make the cutter hole blind if you want the means to adjust the cutter in very small amounts.

Getting started on the model isn't a factor at the moment. Keep on doing what you are - preparing the ground and asking questions so when you do you are ready for it

Stevie - that is the strongest (and the slowest cure) the other versions do not have the same strength or temperature characteristics.

Regards - Ramon

Edited By Ramon Wilson on 13/11/2020 23:15:06

OK. So in terms of aligning the cylinder on the cross-slide, ready for boring, I'm thinking of turning a hardwood plug, and centering each end of that, then tapping it into the cast bore. I can then use the vernier points to make sure the outside of the casting ends are more or less concentric with the bore (as with teh 10V). It will make machining the cast O/D's more consistent for fitting whatever cladding I decide on. I can then use the head and tailstock centres to make sure it's aligned before clamping everything down. I suppose it would be good to tighten the cross slide gibs as well?

On the cladding - I'm not sure whether to stick with aluminium, or try wooden strips. I like aluminium better, but it seems like a tricky job to cut it to the cylinders, what with the feet and valve blocks etc.

How do you intend to hold it ? Do you have an angle plate or vertical slide?

Yes lock the gib screws

I was just going to remove the top slide assembly, and block it up directly from the cross-slide t-slot table. It would sit either on it's feet, or on the valve face (I'd have flatted it with a file and on the surface plate, ready for final machining later). Then clamp it with a bar (or two) over the top.

If I've understood correctly, I progressively move the cutter out from the bar until I get to the right diameter - The cylinder itself only moves left to right by means of the saddle?

That sounds to be the way Westbury did it on packing clamped to the cross slide a method I have used on several cylinder. Do think ahead as to how you will machine at least the piston end of the cylinder's end flange square to the bore and also how you will do the final finishing of the feet and port face.

Don't know if I dare suggest flycutting the end of the cylinder while it's still undisturbed and attached to the topslide

If I did the fabricated version I would hold in 3 or 4-jaw (not sure which will fit) to bore and face one end and then machine everything relative to those surfaces.

Edited By JasonB on 14/11/2020 13:42:28

I'm happy to do the bore and facing in the 4 jaw chuck, as with the 10V.

I thought the whole point of the boring bar between centres was that it's more accurate for longer cylinders? Then again is it really that different than the 10V - it appears to work fine? Seems far easier to do in the chuck assuming it can be held in there.

I'll still use fly cutting for as much as I can - I really dislike the look of a milled surface, at least the ones I do!

I didn't know there was a fabricated version. Do you mean as in milled from solid bar?