Stuart Twin Victoria (Princess Royal) Mill Engine

[JasonB]

On JasonB Said:

Going back to the handwheel suggestion. Put your alignment pin in the flywheel that is in the chuck, slip on the previously turned one and touch the tool on the rim and zero the handwheel. Now you know the setting to turn the second handwheel to.

It’s times like these that my 300mm digi calliper comes out of the draw.

Yes, another option. I’d already forgotten about the spigot.

[Dr_GMJNParticipant @dr_gmjn]

OK, so I’ve used three measuring methods – just out of interest to see the relative accuracies:

1) A strip of card wrapped around the smaller wheel, and its length (circumference) measured with a tape measure, then wrapped around the larger wheel and the difference measured with verniers:

2) Measuring the chord length and its offest from the circumference using verniers:

3) Height gauge:

 

Assuming the height gauge is the datum (as the most accurate method) Anyone fancy a bank holiday guess at the maximum and minimum deviation from this – on radius, in terms of thou – between the chord and tape methods?

I’m going to use Jason’s spigot method as a double-check on the height gauge readings, and hopefully get it done this afternoon.

Thanks all.

 

[JasonBModerator @jasonb]

I thought you wanted to do the measuring with the second one still in the lathe, if so height gauge method may be tricky.

 

If off the lathe then stand the two side by side and measure the height difference with depth gauge or the back of your callipers.

But as you have a height gauge then just clamp a flat plate to the bottom and you effectively have a vernier calliper.

[Dr_GMJNParticipant @dr_gmjn]

I did want to keep it on the lathe, but as mentioned I then thought that I really want to bore the hub and face the mating parts of the rim/hub in one setup, to reduce the chance of them being out of true. I’d machined the outer face first (as per the article method I think), which I suppose was a mistake.

So with both wheels off the lathe, I’ve now just measured them directly with the height gauge, and will take off the measured difference once the second wheel has been re-set.

I tried the other two methods out of interest to see how accurate (or inaccurate) they would have been.

 

[Dr_GMJNParticipant @dr_gmjn]

Mounted the second wheel and machined it to the o/d of the first:

Counterbored the hub – I hope this doesn’t interfere with the broching process too much:

Here are the two wheels:

One middle boss is wider than the other, but I suppose this will not be visible once joined and filled. There is still metal-on in terms of overall outer circumference face width, and overall hub length, which I will re-size on the faceplate after joining.

And fitted to the spigot:

I managed to get both small bores to zero difference according to my gauge and verniers, but unfortunately, despite the spigot being a decent fit in both, I can still wobble the wheels against each other very slightly. I could re-make another shaft to be a tight fit, but am slightly concerned it might lock iteslf in place after clamping the wheels together. I suppose I could make it in brass and that might be easier to drift out?

Next job is to drill the peripheral holes for the clamping screws, and then do a bit more clean-up of the cast areas before finally bringing them together. Didn’t quite get them joined this holiday, but still some progress.

 

By the way, the difference in radius between the card tape, vernier-measured chord, and height gauge (datum) was +/- 0.001″. Maybe it was luck, but I found that pretty incredible especially with the card tape.

[Dr_GMJNParticipant @dr_gmjn]

Thinking out loud again:

For the final facing operations (after joining), and machining the recess for the barring ring, if I did make a tap-fit brass spigot, turned between centres, could I machine the whole assembly between centres, using a drive dog through the spokes?

Seems like it would save a lot of setup time, and be more accurate than setting and re-setting on a faceplate for each operation?

Thanks.

[JasonBModerator @jasonb]

I’ve never got a good finish doing flywheels mounted like that as the lack of support at the rim causes fine chatter marks Probably won’t be rigid enough for rope grooves either.

I prefer to machine the rim OD, one side and do the bore all in one setting which keeps things true then the other side of the rim is a simple facing job.

[Dr_GMJNParticipant @dr_gmjn]

Yes, I forgot about the most important thing – the bore, which needs opening from about 11mm to 14mm.

Re. Bonding the halves, I think JB weld for the hub, and Araldite for the rim – I’m concerned that JB weld on the rim might leave a black line, which, I think in theory would end up on top of the middle peak of the rope grooves. So it would presumably be quite visible. I guess I could JB Weld where the inner spoke blocks are, but from memory it’s quite grainy and might hold the rim apart slightly. Could relieve them a bit, but is it worth the effort?

[JasonBModerator @jasonb]

Unless you ar eonly using one of the two tubes your JBW should be grey and quite close to the colour of cast iron. Applied very thinly it should not show anymore than the amber of Araldite.

I’d much rather machine across the JBW than Araldite which is always a bit soft even after setting and I’m sure that if Tubal Cain had it available 40yrs ago then he would have used it.

[Dr_GMJNParticipant @dr_gmjn]

OK, JB Weld it is.

Bit more progress last night – I measured from the shaft o/d to the inside of the machined rim, and subtracted half the head diameter of an M4 caphead (M3 didn’t look robust enough to me):

Then turned over and marked each square pad to make sure I could drill and tap it. It was very close, but it’s just about do-able.

Then centre marked them:

Drilled to 4mm, and countersunk the mating face holes:

Then turned over, and counterbored with a 6mm end mill. I turned down the M4 caphead head diameters from 7mm to just under 6mm, because even at 6mm, somehow the end mill grazed the machined rim (doesn’t matter too much I guess because that part will be machined away for the barring ring insert):

Plenty of thread protruding – next job is to align the wheels on the spigot, then drill and tap the other side. I’ll make blind holes to save filling – that side will be untouched apart from clean-up and a slight recess machined under the rim.

So after drilling and tapping I’ll do a final clean-up of the cast surfaces – the pads will need matching becasue some have a prominent step.

I may also grind a small chamfer along all mating edges (apart from the outer edges to be machined) as a sort of JB Weld-prep. May help with disguising the joint line.

[Dr_GMJNParticipant @dr_gmjn]

Made a jig to align the spokes, and then, with the spigot fitted and a slip gauge under the rim, marked through the counterbored holes onto the second flywheel with a drill:

Then centre-punched & drilled:

Countersunk slightly:

and tapped M4:

All fitted together nicely (dry):

I then put the assembly in the lathe between centres, and checked runout.

Radial runout on both wheels was a couple of thou, but axial runout was 0.018″, and gave a visible wobble.

From this I assume the two wheels are not co-axial – this seemed to be confirmed when I could feel a slight step at the join line on one side, but smooth on the opposite side.

This may not be surprising since despite re-machining the spigot to give a better fit, I can still very slightly rock the two wheels against each other. I don’t think I can get the spigot a tight fit on both wheels due to the bores being very slightly different. I tried a dodgy method of centre-punching around th espigot to get a tigher fit, but obviously that didn’t work too well.

I suppose I can try to correct this by feel on the step of the rim to get them more co-axial, but it’s a bit hit-and-miss- especially when I finally assemble with JB Weld.

Anyway, it is what it is (which isn’t a disaster by any means), I will just have to get it as good as I can I guess.

[Dr_GMJNParticipant @dr_gmjn]

I think I might have found the issue – three of the bolt heads were tight in their counterbores. When I removed them and got the rims concentric by feel, the spigot dropped in (which suggested they were better aligned. Re-checking on the lathe gave about 0.0025″ max. runout for both rims:

and aout 0.0045″ axial:

So I think that will be fine – they look much better when spun. I’ll have to re-check after JB Welding that they are true before final tightening and leaving to set.

Now for final fettling of the cast bits.

[Dr_GMJNParticipant @dr_gmjn]

So after leaving the castings a week or so after rough machining (I think as per the instructions), I did a bit more fettling of the mating parts, and cleaned off the primer so I’ll have a cleaner base to start finishing from once joined and filled. Then applied the JB Weld:

 

and put back in the lathe to check that they were true:

After a bit of tapping with the hammer, they reverted to being a few thou out, but nothing serious.

So now they are left to set:

I remember some conversation about the rope grooves previously on this thread – I wonder if I could use a standard dimond shaped tool for these? Getting a precise profile doesn’t seem that important at this scale?

Also, how is the tool held so far out from the toolpost (on the ML7)? I think there is an image in the magazine article showing how it’s done, but it hasn’t reproduced well enough for me to see how it’s done. I expect there may be a lot of overhang unless perhaps a specific toolholder is made from bar stock.

Thanks.

[JasonBModerator @jasonb]

Might be able to do it with a VCGT insert held in a custom holder otherwise it’s grind up a bit of HSS and make a simple holder like this mounted in the near side of the toolpost

[Dr_GMJNParticipant @dr_gmjn]

Thanks Jason. If grinding a tool, how do you get it symmetrical? Some kind of jig?

I suppose any slight asymmetry would mess up the groove spacing.

[JasonBModerator @jasonb]

Anything from a couple of Sharpie lines on your grinding resy to a jig, you could 3D print something.

It won’t mess yp the spacing and the tops of the groove will all be the same distance apart.

I seem to remember seeing someone use a parting shaped cutter first to take out most of the material and then change to an angled one. I don’t think you can swing the Myford topslide round enough to allow cutting to the angle so will get a lot more tool contact and the risk of chatter.

[Dr_GMJNParticipant @dr_gmjn]

Jason, yes I think the article also suggests using a parting/grooving tool initially on the grooves, and also moving the shaped cutter side-to-side so that it’s only cutting one side at a time.

[Dr_GMJNParticipant @dr_gmjn]

I might have a go at making a tool holder later on. Any advice on tool geometry? I still have some of the cylindrical bits that Ramon sent me – that I made the cylinder boring tools from.

Also, what’s the best way of shimming the wheel assembly out from the faceplate? The two o/ds are almost exactly the same, with no overhang of the flywheel. I assume some bits of aluminium plate might do, but I am a bit concerned about slippage.

Thanks.

 

 

[JasonBModerator @jasonb]

Nothing special, base it on one of your DCGT inserts, the 7deg side clearance will do.

Hot glue should stop packers slipping, if you use thin bits of ali 1.5mm or so thick and 6mm wide just bend into an L shape then they won’t get past the rim

[Dr_GMJNParticipant @dr_gmjn]

I made a test piece for the grooves – much smaller diameter obviously, but the correct width. I wanted to get used to the spacing method, and to try the tools I made.

It wasn’t much of a success – I find grinding tools is hopeless, and the results were – as expected – poor. I think that if it’s not symmetrical, the end grooves to the edge of the wheels would be wrong even if the central groove spacing was correct.

At least I sorted the spacing method using the leadscrew handwheel though.

I reverted to an insert type tool, and things improved a bit, although nowhere near perfect, mainly becasue the workpiece kept moving.

So, what’s the best way of making a VCGT 90 degree holder? Is it a simple case of milling a piece of square bar to get the right height, then drilling for the Torx screw, and perhaps retaining the back end of the tip in a JBWeld “V”? I could coat the tip in grease so that the insert didn’t stick, then I could replace it.

I think that the torx screws in inserts are slightly pre-loaded towards the holder, but I wouldn’t be able to do that  I guess.

Not sure If I’d need the 1mm wide parting type tool to start the grooves if I was using inserts? If I did need it, I’ve no idea how I’d make anything other than a mess again – I don’t really have any of the correct equipment for grinding – the wheel I’ve got is worn, and the adjustable jig I made for the boring tools never really worked properly. I’m keen to get on with it, and don’t want to spend hours of trial and error again on trying to make tools that don’t really work.

 

 

[JasonBModerator @jasonb]

One of your main problems is the amount a tool contact, as that goes up the chances of chatter increase. This is why the parting tool first is suggested as you are only cutting with a 1mm wide contact on the cutting edge.

Once you change to the Vee tool then if the cross slide is set parallel to the lathe axis you can move it back and forth slightly so you take alternate cuts with the left and right side of the cutter which again reduces contact. I don’t think the topslide will swing round enough to do it like the angled thread cutting method that some people use where only one side would be cutting.

The bigger the bar you use the more rigid the setup so if you can go up in size with that. May mean ditching the QCTP and reverting to the original Myford method of clamping the tool to the top of the cross slide.

As for making a tool to take inserts then you really need to machine a pocket. Not too hard, set the mill vice to half the 55deg and mill a slot. Leave the work in the vice and reposition it at the opposite angle so tool height stays the same and mill a slot that just crosses the first then mill out what is left where you want th etool to sit. The cross ensures there is clearance for the tip which won’t fit against a radius left by a cutter.

To drill the hole place an insert in the pocket and hold a drill that is a good fit in it’s hole upside down in the mill chuck and find the hole position when insert tight in the pocket and zero dials or DRO. move a few thou closer to the edge of the pocket and drill your hole which will draw the insert into the pocket.

Post a photo of what you have in the way of a grinder and also a belt or disc sander if you have one of those then might be able to suggest a way to grind the tools

 

[bernard towersParticipant @bernardtowers37738]

I think you may find it easier if you drill the hole for the tip first this gives a pocket for the milling cutter to go to. As Jason says you then fit the insert to the pocket find the hole centre move a few thou into the pocket drill and tap. then profile the underside to suit.

[JasonB]

On JasonB Said:

 

Post a photo of what you have in the way of a grinder and also a belt or disc sander if you have one of those then might be able to suggest a way to grind the tools

 

The last one isn’t fitted to the bench. Ironically it’s got the best wheel. Never used it, and I don’t have the rest for it.

[bernard towers]

On bernard towers Said:

I think you may find it easier if you drill the hole for the tip first this gives a pocket for the milling cutter to go to. As Jason says you then fit the insert to the pocket find the hole centre move a few thou into the pocket drill and tap. then profile the underside to suit.

Sorry Bernard, I don’t understand what you mean.

[bernard towersParticipant @bernardtowers37738]

The hole that i mentioned is for the end of the tip that is not in use, the end facing away from the work.

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