Stuart Twin Victoria (Princess Royal) Mill Engine

[JasonBModerator @jasonb]

Here you go, rough and ready video. Imagine the bit of MDF is your cover with it's cast gland boss drawn in blue and that is sitting on the rotary table.

Line up the cover with the spindle however you want and zsro X & Y

Then with a rod in teh chuck/collet offset to suit your spacing in my case 18mm as the holes are 36mm ctrs

Bring down the quill so the rod enters a hole and lock the quill ( I had to put the phone down for that)

Then either rotate the cover in your jig or turn the table until you get the best looking alignment and either tighten the cover to the jig or note the table angle.

Your cover is now lined up in X and Y ready to drill the holes

[Ramon WilsonParticipant @ramonwilson3]

Not a short cut just easier ways of going about matters for the same result. Working to a paper template is not on other than for a guide. Establish the centre – move out to drill and tap the gland holes and mill the profile if desired

Well yes you still could – both Jason and I are saying the same thing. He suggests a drill bit – I prefer to use the more precise location of a cone.

Running as truly as possible just turn a short piece of say 8mm dia steel to a 60 degree point. Providing the R/T is truly centred it's just a matter of moving the plate holding the part on the R/T with the centre you've just turned held in the drill chuck locating which ever hole you wish to work to. You allow the plate to float until happy with the position then clamp up. Very simple and easy to position.

Obviously set the R/T to a 'zero' and align the centre line by eye or a square off the back column for radiusing the outer points. Bear in mind that a full size engine would be very unlikely indeed to have the glands the identical shape of the casting.

I have a very quick way of machining diamond shaped glands so will do a separate thread on here later for you and others rather than put more images on your thread – must water the garden first though!

Best – R

[Dr_GMJNParticipant @dr_gmjn]

Jason – thanks for taking the time to explain your method – I think I’ve been on the right lines, but the sequence, and aligning the r/t vice/chuck has thrown me off a bit.

Ramon – thanks for that. The paper template was just a quick method of making sure I could get the final shape out of the casting. The aluminium piece was to familiarise myself with the process again, and as an orientation jig for drilling the mounting holes in the castings. The two screw holes were co-ordinate drilled first, then aligned on the r/t, actually with an upside-down drill. Then the profile was milled.

So the idea was I could temporarily glue the aluminium in place on each boss. Align the central hole, then align one of the screw holes (again with a drill bit). Then I can drill the tapping holes in each boss. Then, when I replicate the brass blanks for milling, they will also have pre-drilled holes which will align precisely with the corresponding casting holes. Then screw the brass blanks in place and mill the assembly.

Thanks both.

[Dr_GMJNParticipant @dr_gmjn]

Set up the covers in the mill to get the gland clamp holes correctly lined up dead horizontal:

Centred the r/t to give zero runout:

Mounted the chuck, and placed a cover and a tight fitting spigot I turned from aluminium. The spigot was then clamped into the collet chuck with the 4-jaw chuck loose, and then nipped up:

This should have got we very close to everything concentric, but try as I might, a 0.0095” runout remained:

Even by adjusting the 4-jaw on the rotary table, or trying to measure direct to the inside of the housing, I couldn’t get better than 0.0095” according to the dti and revolved in the spindle.

Anyway, it was then a simple matter to fit the gland template and rotate the r/t until the mounting holes were in a line, 8mm offset each way in x:

Then with the r/t table locked, drilled all the holes using the DROs:

At the end of the day, they both fit, the holes are aligned and the bosses should be in their optimum positions for the profile milling:

Next job is to drill and tap the milling fixture hole array, then mill the boss profiles.

Re the runout issues: I don’t have enough height clearance to easily fit the dti in the collet chuck, and it’s tedious to have to constantly swap collets to do the various setups. I guess I could do with a dti mount that clamps around the spindle. I think part of the problem is the clunky dti mount I’ve got, that’s not easy at all to set up zero by hand, especially when I don’t have the use of the x/y table as in this case.

Edited By Dr_GMJN on 18/06/2022 18:53:47

[Ramon WilsonParticipant @ramonwilson3]

Good result Doc – your 9 1/2 thou is a fair old run out but as you appear to have done the boss bore and holes at the same setting irrelevant really so everything should be fine.

Don't know if you've checked my thread I put up for you yet but you'll see that a simple plate will do just as well as the chuck and give you a lot more head room to boot. That's my biggest issue on the Linley when the RT and chuck are together.

I have a small DTI articulated mount that fits directly in the drill chuck – a real boon when space is at a premium.

Heavily distracted into a 32nd scale Phantom at the mo but your posts are having the opposite effect!

Keep it coming

 

Edited By Ramon Wilson on 18/06/2022 19:10:37

[Dr_GMJNParticipant @dr_gmjn]

BTW when I was making the aluminium spigot, I mounted the caps on it and checked o/d, cylinder spigot and piston rod hole runout with the dti and all were negligible. So it’s not a hole form error. Bit puzzled about the runout on the r/t, since I was effectively lining up round holes on an axis known to be concentric with the spindle.

Edited By Dr_GMJN on 18/06/2022 19:10:01

[Ramon WilsonParticipant @ramonwilson3]

Ah, I didn't read that right.

Once the R/T is positioned under the spindle and running true that's finite so if the spigot is running out – and you are confident that it's true to the OD of the cover – then the four jaw must be influencing it in some way – slightly tilting it perhaps.

Try holding something round, smooth and straight in the four jaw that you can test with the dti to see how much run out you get – near and away from the jaws

[Dr_GMJNParticipant @dr_gmjn]

Ramon – yes, I saw the split mounting plate in your post. Having now gone down the route I have, and now thinking about what I actually did, I realise that yes, by using the chuck I’ve made a new set of issues for myself, especially in terms of clearance height. I was thinking I needed access to the o/d to get the centre, but of course I’ve ended up not doing it that way anyway. The clearance using a plate would have made things much easier. In fact that, coupled with watching Jason’s video again has made me wonder if I’m really not thinking straight (I did mention covid!).

So what I’ll do is continue with the mount block for the profile milling, then, as a double/check once complete, I’ll remove the vice from the r/t and see if I can set up using a method more akin to yours and Jason’s, and see how much runout I get.

It’s easy to go down a particular route and get fixated on something that ultimately doesn’t matter!

Anyhow, it’s really a cosmetic exercise, because it’s the cylinder cap spigots and rod hole that ultimately need to be concentric with the cylinder bore I guess.con

[Dr_GMJNParticipant @dr_gmjn]

We’re getting out of sequence with replies! Yes, I checked runout on the 4-jaw and it was indeed about 10 thou, but this shouldn’t have been a factor because the entire 4-jaw was aligned on the r/t by the spigot mounted in the spindle. The 4-jaw was then effectively a static vice, so runout was irrelevant. No amount of adjustment could seem to get it better.

[Ramon WilsonParticipant @ramonwilson3]

If that's the case then the relationship between the four jaw (I assume it's a self centering one?) and the RT is awry somewhere –

If the R/T is true to the spindle

and the R/T hole is running true

and the four jaw chuck is reasonably accurate (much better that 9.5 thou) I think mine is around 2-3 at worst

then the only thing left to influence it is the aligning spigot, the plane of the RT or the bolting tension.

You could check this by removing the spigot and let the chuck float on the RT. Repeat your exercise with a bar in the collet clamping the chuck to it with everything 'on centre'. Clamp the chuck just sufficiently tight enough and test for run out – then tighten up and recheck. Check there's no detritus under the chuck too

[JasonBModerator @jasonb]

I have the same DTI holder and you should be able to just give it a tap with a finger to bring the needle to where you want it, I usually have it out to the side so it's easy to see. Then just turn the bezel to bring the zero to the needle position, another light tap if needed.

You should certainly be able to set the part in the chuck true by doing as you have with the chuck loose then tightening when the dti clocks true. You are rotating the DTI & spindle and not the table? Any runout after that will be the hole in the rotary table not on its rotational axis.

Edited By JasonB on 18/06/2022 20:03:11

[Dr_GMJNParticipant @dr_gmjn]

Thanks both.

Jason – yes, always rotating the spindle. I did rotate the table initially to check runout, but it was true. The dti holder was very difficult to position because of the height restriction – one part or another was crashing, so the adjustment may have been out, or even some play somewhere. As I mentioned – I’ll re-check when I’ve got more room.

[Ramon WilsonParticipant @ramonwilson3]

As an after thought Doc, my comment referring to a 'spigot' was such that you should have between the RT and the chuck – to align the chuck to the table – not the aluminium spigot used in the part.

Forgive me stating the obvious but it goes without saying really – once you have the R/T truly aligned with the spindle and the DRO/dials zeroed anything else bolted to the RT has to have the same reference.

I have a stub of steel that locates into the 1.00inch hole in the RT which then registers into the back of the chuck. Also have a 6" diameter sub-plate that does the same.

Once the R/T is set then the part is set to the same reference – it should then all be in alignment. If of course the chuck has a considerable run out then the only way round that is to have the chuck float and align the part – which is why a simple plate is sooo much easier

Hope I'm not offending your sense of understanding of this situation

[Dr_GMJNParticipant @dr_gmjn]

Ramon – no problem repeating setup procedures, but yes, I realise that getting everything co-axial is important and that there’s a set way to do it. Remember though that in this case, runout of the chuck was irrelevant to the setup, because it wasn’t rotating, and nor was the part being removed and re-fitted; it was purely used as a vice.

Anyway…drilled and tapped the cover fixture, and fitted the first cover:

I’ve put JB Weld around the boss as a bit of insurance against running off the casting where it’s a bit marginal (this was the point of trying to get the mounting holes as perfectly aligned as possible, since the excess cast material available for error is tiny. A degree or so either way, and the cutter would be in fresh air on one side or the other, and the wall thickness next to the bore would be very thin).

Then double-checked the alignment of the R/T, mounted the vice and centred on the job while everything was still loose:

Then put a smaller drill in the collet chuck to offset the job left and right and set the end stops:

This will allow me to move the cover to automatically re-centre on the end holes to mill the end radii, while maintaining the same cut depth.

All ready:

Then remembered I’ve not yet made the brass blanks for the gland collars…doh!

Edited By Dr_GMJN on 19/06/2022 16:00:16

[Ramon WilsonParticipant @ramonwilson3]

"Then remembered I’ve not yet made the brass blanks for the gland collars…doh!"

Ha! you won't be the first to get ahead of yourself Doc – know the feeling.

I like your idea of using the JBW before machining – a much better way of taking care of low spots rather than afterwards.

Apart from the glands what's the next in line?

Best – R

[Dr_GMJNParticipant @dr_gmjn]

Posted by Ramon Wilson on 20/06/2022 09:32:37:

"Then remembered I’ve not yet made the brass blanks for the gland collars…doh!"

Ha! you won't be the first to get ahead of yourself Doc – know the feeling.

I like your idea of using the JBW before machining – a much better way of taking care of low spots rather than afterwards.

Apart from the glands what's the next in line?

Best – R

Thanks Ramon! You were asking about the other thread you started – it looks like a good way of making the brass parts, but what I was after was profiling the corresponding cast part at the same time. Since I'd bought the R/T last year, it was a case of "why not use it?" even though it might take a bit longer to set up. TBH I've been chasing thou (which is why it's taken a while to set up), but for this job it doesn't really matter I guess. Im trying to set things up as accurately as possible whether it's a critical job or not – just for practice.

Next job is to profile the exhaust pipe flanges from brass – while the R/T is set up. Much easier for those becasue they're not aligned to much of a cast profile (or at least a very shallow one that's not easy to mill). After that I think I'll make the butterfly valve housings, and the valve chest lids. At that point I think I'll continue and do the pistons and valve rods etc., so I've got a pair of pretty much complete cylinder and valve assemblies, and then review progress.

Cheers.

[Ramon WilsonParticipant @ramonwilson3]

Yes, of course Doc, if you want the two parts to match that's a different matter. Full size of course it's very unlikely so I've never attempted to make them the same but I agree it does look neater

Incidentally the plate clamp method of work holding is perfect for doing the eccentrics – makes the job very simple indeed and everyone identical. Perhaps something to bear in mind when you get to that stage.

My rotary table was one of the first tools, the first I think, I made when starting out. It was from the old MES castings and has done me proud over the years. I added a degree ring at some stage but the best mod was, without a doubt, to fit dead stops to it – takes away that ever present potential of over movement!

All sounds good so looking forwards to seeing your engine grow

Regards – R

[Dr_GMJNParticipant @dr_gmjn]

Made a start on the brass clamps for the piston rod seals:

So the long awaited screw-up…

After drilling the centres I realised I’d made them 4.9mm diameter rather than 4.8mm. Same with the cast cylinder cover holes. Oh dear. I misread the number on the drill – twice it seems. To be fair the etching on the drill shank isn’t clear, but I should have measured it.

So…what to do?

The piston rod is specified as 3/16” stainless steel, which I’ve already got.

So with a 4.8mm drill, this gives about 0.0015” clearance in diameter.

With the 4.9mm drill, it’s 0.0055”.

Can I turn some stainless down to compensate, and maybe polish it afterwards?

Bush the castings somehow, and re-make the brass clamps?

I don’t really want to start again from buying new cap castings, but I will if necessary.

Cheers.

[Ramon WilsonParticipant @ramonwilson3]

Ha, Commiserations! I remember doing that just after starting a new job – very embarrassing and it quickly lead to the practice of mic-ing the drill as soon as it's selected, something I still do even to right up to today!

 

You should get away with leaving as is and allowing the packing to take up the discrepancy – the annular gap after all will only be just under .003" The slope on the mating faces will squeeze the packing inwards equally. Personally I would use a fine thread loaded with graphite than the traditional graphite packing which can be quite coarse and usually requires stripping into the individual stands for ease of packing. I have a good supply of Graphite if you need some BTW

You could use 5mm ground stainless rod too – just ream the two parts at the same time after assembly to suit.

Either will easily overcome this slight setback.

 

Edited By Ramon Wilson on 21/06/2022 22:28:17

[Dr_GMJNParticipant @dr_gmjn]

Thanks Ramon – I thought you'd come up with a solution!

I like the 5mm diameter option better – but what size to ream? Would a 5mm reamer give too tight a fit?

I'm planning on using the braided PTFE tape as I did with the 10V – it worked very well.

Cheers.

[Ramon WilsonParticipant @ramonwilson3]

Though a small annular gap is desirable I would just ream it a standard 5mm – you could buy a special 5.01/02 but it's hardly worth it – if it does need opening up slightly it could easily be lapped to give a looser fit

As said before I always use PTFE impregnated braided yarn as a piston seal but always use the string like graphited packing on the piston and valve rods. Though I have no experience in using the PTFE tape as you describe I feel there could be a possibility that 'strands' of it could find their way between rod and hole which is very unlikely with the coarser graphite packing. I unwind the basic graphite 'string' to give (still quite coarse) individual strands that makes for easier packing, especially on small glands, but have used fine cotton line with graphite which works just as well.

As always it's a matter of choice though

Regards – R

Edited By Ramon Wilson on 22/06/2022 11:16:01

[JasonBModerator @jasonb]

5mm H7 reamer which is quite a common tolerance will be fine with 5mm stainless rod which can be a little under nominal anyway. That's what I used on the Real I'm describing at the moment, one of ARC's Machine type.

[Dr_GMJNParticipant @dr_gmjn]

OK thanks both. I'll get some 5mm rod and a reamer.

Ramon: I think Jason mentioned PTFE tape for the packing for the 10V. It was a bit stringy and tricky to deal with at first, so I twisted it, then plaited three lengths of it to give some bulk. It was then easy to use and works very well.

Cheers.

[JasonBModerator @jasonb]

Yes you need to do that if using tape, the actual PTFE packing is more solid like like a thin rope or cord and there are also square section ones available.

[Ramon WilsonParticipant @ramonwilson3]

Whatever you are happy with Doc. I haven't tried it so can't really comment but if Jason has used it successfully then carry on – one things for certain it'll be a lot cleaner than using graphited yarn!

I like the braiding BTW but I did you have to use a fair bit of tape to get that bulk?

Best

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