Stuart Twin Victoria (Princess Royal) Mill Engine

[JasonBModerator @jasonb]

Posted by Dr_GMJN on 29/08/2022 20:37:52:

Unfortuntely a lot of the steel I got specifically for this model is 080A15 for some reason.

Your square and rectangular sections are likely to be this spec as that is what is usually available but EN1A is more readily available in round section so worth buying. Drawfiling with emery over the file will clean up flat faces, the fish bellies on the rods will need hand finishing so not really much in the way of turned surfaces on the sq/rec sections to worry about.

Blowing some of those images of tools up on Thumbsnap the cutting edges look a bit soft. The cutting edge is really a corner where two flat faces meet and should be as crisp as possible, this is where rubbing on a stone or diamond plate helps. Also try to grind the tool without lots of facets, the belt sander may be easier to do this after initial shaping on the grinder

[Ramon WilsonParticipant @ramonwilson3]

I didn't realise you were using a belt sander to finish your tool. That's not an ideal way to get a good cutting edge as the belt is soft and flexes in comparison to a grinding wheel. If you look at your image you can see that the faces aren't uniform as such – that front cutting edge is poor for instance. One thing you haven't mentioned is the off hand grinder you have and the wheel condition – trying to grind a decent tool edge on a very coarse wheel is not ideal for instance.

Hopper, if Sparey says 30 degrees then so be it but the 15degrees already suggested will make a big difference too. As already said it is only the very tip of the tool that does the cutting – just the depth of cut in other words – so the tool's basic shape once ground only needs refining at the point plus a bit – that is the area where you need to pay attention to the shape Doc, not the whole tool.

It's easy to become fixated on producing the ideal tool shapes and angles to the descriptions in books – certainly did myself when first starting out and that was fraught with difficulty not least as the grinder I had was a Black and Decked geared one – no real power and phenomenally noisy. I replaced it quickly with a small 5" diameter wheel one that though on the small size did me well for many years – grinding a tool from solid was a slow affair but it is still in my workshop and used to do the fine 'tweaking' after grinding the basic shape out on an 8"

[JasonBModerator @jasonb]

Doc said he has both grinder and sander and a belt sander often has a bigger table so should be easier to hold the tool in one position for each face.

I quite often use mine and get a reasonable face.

[Ramon WilsonParticipant @ramonwilson3]

On a general basis I would say my belt sander, just ahead of the bandsaw are the most used tools in my workshop but I don't ever recall even thinking about using the belt sander on a cutting tool.

Never saw it done at work and have never felt need to do it myself

My small 5" Slibette bench grinder is perfect for finishing tools

Maybe I'll give it a try though

Each to his own eh

 

 

Edited By Ramon Wilson on 30/08/2022 09:20:24

[JasonBModerator @jasonb]

Many a woodworker or blade smith will use a belt and they can get very obsessed with sharpness. The Sorby is quite a popular one though I just have a Clarke.

[HopperParticipant @hopper]

Posted by Ramon Wilson on 30/08/2022 08:17:53:

Hopper, if Sparey says 30 degrees then so be it but the 15degrees already suggested will make a big difference too. As already said it is only the very tip of the tool that does the cutting – just the depth of cut in other words – so the tool's basic shape once ground only needs refining at the point plus a bit – that is the area where you need to pay attention to the shape Doc, not the whole tool.

Yes it raised my eyebrows too, being more used to 10 degrees or so as used in industry back before inserts became ubiquitous. But in more recent years, Sparey's knife tool worked phenomenally well for me on my old 1937 Drummond, with a much smaller diameter spindle than an ML7 etc and thus much more prone to chatter. (G H Thomas made some comment he used to call his Drummond "Old Chatterbox".) With the acute 55-deg included angle, that old machine will take 100 thou deep cuts without chatter, and on fine cuts will produce a beautiful finish with accuracy down around half a thou or even less if required. On the ML7 it works equally well, if not better.

But the honing of the edge on the oilstone is critical. It should FEEL sharp to the finger. You want to cut that metal, not bludgeon it.

That said, I have found pretty good results on the ML7 with GT insert tooling. Not as shiny smooth as HSS but acceptable and easily dressed up with emery.

Doc, what feed rate are you using? Should be down around 2 or 2.5 thou per revolution if you use the three largest and three smallest gears from the standard Myford set. From memory something like 75, 70, 65 and 12, 20, 25. There is the special "fine feed" gear for the output on the reverse mechanism that has the 12T gear made in one piece with the larger gear. Still available from Myford I belive. The standard 20 is a bit coarse on that first reduction.

[Ramon WilsonParticipant @ramonwilson3]

Posted by JasonB on 30/08/2022 09:45:33:

Many a woodworker or blade smith will use a belt and they can get very obsessed with sharpness. The Sorby is quite a popular one though I just have a Clarke.

Not quite in the same arena I would say Jason but as said each to his own. I certainly use the sander for chisels and the odd kitchen knife but wouldn't have given it a thought to use it for lathe tooling.

That said and following your suggestion I have just tried to improve a tool using the belt sander. I used a tapered nose tool as suggested to Doc previously. Setting the table to an approximate angle it does work quite well I agree but, there is a distinct rounding of the cutting edge as the belt relaxes from the cutting pressure – small, minute even but definitely distinct. Not exactly convinced it's a viable method to recommend (certainly for me) at this stage but I haven't tried it out as yet – obviously the proof will be in the eating

Edited By Ramon Wilson on 30/08/2022 12:56:37

[Dr_GMJNParticipant @dr_gmjn]

Thanks very much all for the comments and info.

So this morning I spent half an hour on the EN1A, and it immediately gave a much better result. Started wth the (un-modified) HSS tool:

Which gave a far better finish on this material. However, the second pass was nowhere near as good, with some ridges apparent.

So, gave up with that (again), and went to the GT insert, which gave fairly similar results, and more consistent in subsequent passes too:

After wrapping some abrasive paper and Autosol around it for a minute or so, I ended up with this:

Not perfect, but far closer to what I wanted. So GT insert, lubricated with oil aerosol and finished with fine abrasive and polish is what I'll do.

Also – Ramon & Jason's comments on getting lengths consistent: I've got a second-hand set of unashamedly uncalibrated slip gauges. I assume the procedure is something like this?

1) Put the tool against the end face of the workpiece.

2) Make a stack of gauges to the machined shaft length required:

3) Put the slip gauge stack between the saddle and the stop, and lock off (I made an adjustable stop when building the 10V):

4) Cut using feed up to about 1/2mm from the stop, then manually cut to the stop.

It seemed to work OK, although I'll need to lengthen the stop rod for this.

Quick question on procedure:

It was mentioned before to swap the rod after machining one end, so always machine at the tailstock. I suppose to get the diameters of each step precisely the same, I could rotate the shaft after every roughing cut, and final cut, such that the diameter setting would be identical for both ends? The only issue would be the length stop would rely on the centre drillings to be of identical depth, otherwise the lengths would be slightly off.

So is it best to complete one end, then swap and start again on the other, or do them 'simultaneously'?

To answer a few questions:

I'm using a grinding wheel that's a bit too coarse and a bit worn, plus a belt sander. During the conversations on grinding the boring tools ealrier in the thread, someone said that the stuff I was using was better than theirs and shouldn't be an issue, so based on that I've just cracked on with it. The boring tools I ground worked fine eventually.

Re. flood cooling to get rid of the chips – I did think that might be an issue, so experimented with an oil spray can with the tube next to the cut, to flush the chips away – made no difference to tearing on the 080A15 material, although for the final passes on the EN1A I will do it anyway.

The material 080A15 material I'm sure my supplier said it would be OK to machine, but then again he doesn't know the specifics of my equipment (or experience), so fair enough.

Ramon – I'm using brass bearing material, not CI or bronze. I don't think anyone mentioned that was an issue when I mentioned it previously?

Ramon – what is that part you posted – it looks impressive, like the clutch from the space shuttle or something?

Hopper – Re. feed rate: I can't remember the figure, but it's the lowest with standards gears, plus I fitted the one-piece fine feed tumbler gear you mention from Myford a long time ago. So it's fine-fine. Works very well on most other materials.

Thanks all.

[Dr_GMJNParticipant @dr_gmjn]

BTW I do have this Dormer long series centre drill 4mm x 1mm at the tip. I got it for drilling an oil hole in the 10V eccentric strap, adjacent to the stem:

Unfortunately it sticks out of the lathe chuck way too far, but I guess I could grind one end off it – I'd still have a dencent length centre drill if I ever needed one, plus a short one for centering this shaft? I'm assuming 1mm pilot would look OK.

[Ramon WilsonParticipant @ramonwilson3]

Looks like you are on the way in the right direction Doc.

First off you have the perfect set up for determining the length of turned surfaces. Slip gauges are the perfect means for that – their non calibration is of no importance – what they are is far better than any other means as previously described. As your image shows is exactly how I would have suggested – just wasn't aware you had any slips to use.

Personally speaking if you are going to size the holes by reaming through your flywheel, eccentrics and webs etc then it would be a good idea to make them first so you can fine turn/polish the relevant diameters to suit rather than the other way and getting the holes to suit the shaft.

As said, I would do it all from the tailstock end turning the shaft as necessary. Rough the shaft out first to within .5mm on diameters and leaving .5mm or so to come off on the varying lengths. Then fine turn each section to close limits making a note of each setting on final cuts.

I should have included brass – I think I did say so before that 'brass' is fine.

Well lubricated En1a, in combination with cast iron or with any of the soft bronzes eg gunmetal, half hard brass, manganese bronze etc makes for a good if not ideal running surface situation. Incidentally, the pinkish coloured, drawn bronze should ideally be used with hardened surfaces as it can pick up and gall with soft steel.

I don't have flood coolant but do use a brush to apply some if required, much less messy and perfectly adequate at the cutting levels done at home. If you have it of course by all means use it. I made one of those solenoid pumps that was advertised in ME years ago. I can't remember the last time that was turned on – the treacle tin and brush at hand at all times.

The part, 'far from space age', was the front bearing and gear housing from the Bentley engine I was building. All of the steel case parts were made from En1a and turned using HSS. The nine cylinder heads were also En1a the machining of which using mainly home made cutters was described on here several years ago.

 

Here's the rear housing, all of it now residing in New Zealand

I think I may have said on here before but when it comes to grinding lathe tools I have to be one of the laziest around. Only occasionally and really 'when needs must' do I rough out a new tool. Consequently the shapes of tooling are about as far removed from text book idealism as you could imagine. That said however they all work for the most part because the only area I pay attention to is that which actually does the cutting.

I took a very old and well abused tool out today tweaked the end on the grinder and cut some En1a to a fine finish without any issues I did take pics but all were hopelessly blurred

 

Best – R

 

Edit – Personally I would keep the centre drill as is – that could be very useful in years to come. Just get a new 1/8 diameter one from Arc and save the long version for when a standard won't do – very useful when you need it

Edited By Ramon Wilson on 30/08/2022 16:12:07

[Dr_GMJNParticipant @dr_gmjn]

Thanks Ramon.

The Bentley casing looks awesome – I'd have assumed something like that was CNC'd unless you'd told me.

We've been round the houses too many times already with shaft first vs. hole first, I'm going with the last thing that was said, which was do the shaft first, and bore (not ream) the other stuff to suit. I'll probably end up messing something up at some point which will mean one side or the other will be the other way around anyway! I'll get there in the end.

I'll get a couple of the smaller drills; unfortunately I just ordered a couple of slot drills from Arc, so…more postage! Never mind.

[Ramon WilsonParticipant @ramonwilson3]

Well that's your choice of course but it's much, much easier to measure a shaft to the tolerances required than it is the bores to fit the shaft – just my thought.

I oversaw, programmed and ran a 20 tool Haas machining centre for about my last three years of work but those Bentley parts pre date that considerably. I found this photograph (ha remember those?) of an op on the rear bearing housing only the other day

This goes way back further than I first thought – not only is the old original table in use but there's no DRO either. It was this op that lead me to fitting dead stops to the rotary table and some to the Y axis when I replaced the table. (Note the jury rigged dead stops on the R/T) Crumbs, now that is history!

I also took a couple of pics again – as you can see this HSS tool is very close to it's 'sell by' date

It does have a fair back rake on

 

I literally just tweaked that small radius on the front corner on the bench grinder and cut this scrap piece of 1/2 dia En1a with no coolant at about 600 rpm The dots are the fresh turned areas the shiny part about a 1- 2 thou cut. As machined, no emery or wet or dry paper.

Good luck with the shaft – R

Edited By Ramon Wilson on 30/08/2022 22:48:30

[HopperParticipant @hopper]

Posted by Ramon Wilson on 30/08/2022 22:46:07:

Well that's your choice of course but it's much, much easier to measure a shaft to the tolerances required than it is the bores to fit the shaft – just my thought.

^^^^ +1. Trying to bore a tiny hole to the tolerance required to make a good fit on an existing shaft is doing things the hard way.

[Dr_GMJNParticipant @dr_gmjn]

Thanks Ramon. Re. The shaft vs. hole first debate:

You mention relative ease of measuring, shaft vs. bore, which I get, but I’m not machining to a size and tolerance, I’m doing it pretty much by incrementing cuts until one thing fits to another such that it feels about right. So to me it seems irrelevant which I do first.

If I make the shaft first:

and screw up the crank webs, I’m making a new shaft to suit (no spare web castings).

and screw up a bearing, I’m making a new shaft to suit (quicker/easier than making new bearings).

and screw up an eccentric bore, I’m making a new shaft (quicker than making a new eccentric).

and screw up the flywheel…ditto.

If I do all the bores for the above first, and screw the shaft up…I’m making a new shaft.

So whichever bit I make first, and whichever bit I screw up (and believe me, I will)…I’ll probably be making a new shaft.

[Dr_GMJNParticipant @dr_gmjn]

Posted by Hopper on 30/08/2022 23:09:59:

Posted by Ramon Wilson on 30/08/2022 22:46:07:

Well that's your choice of course but it's much, much easier to measure a shaft to the tolerances required than it is the bores to fit the shaft – just my thought.

^^^^ +1. Trying to bore a tiny hole to the tolerance required to make a good fit on an existing shaft is doing things the hard way.

Thanks Hopper, but from what I understand that’s the exact opposite of Jason’s advice!

[JasonBModerator @jasonb]

That is kind of the way I look at it DOC what can I afford to muck up and what part has the most work in it. Different if they were small holes that I was going to ream as I can't get a boring bar easily down 5 or 6mm hole so would do those holes first then make the male part to fit. It's not a universal thing and each job needs looking at to decide what is going to work best.

Also with your new stepped design how will you form the various hols to a measured size with the equipment that you have which is going to be a digital calliper. Using the shaft as a plug gauge will allow you to feel the fit rather than measure a shaft that is a few microns down on a hole you can't accurately measure anyway.

Many an engine is also made with built up crankshafts where you start with material of a set size* so have no choice than to make the various parts to fit the shaft, again if you only have a digital calliper there is not much chance of hitting an H7 tollerence or whatever is needed and hoping it will fit. Better to use a stub of shaft material as a plug gauge and bore to suit that making the bearings a different fit to the flywheel and eccentric and the cranks an even tighter fit.

* This includes all the 2×1 Stuart models where you are supplied material for the crankshafts so the flywheel, bearings and eccentric need to be made to fit.

Edited By JasonB on 31/08/2022 07:27:19

[Dr_GMJNParticipant @dr_gmjn]

Jason, yes, on the 10V the shaft material was supplied finished and I reamed the bearings in-situ. Easy.

I’ve got bore gauges, digital calliper and micrometer to measure the bores, but once measured (plus or minus the inherent error in that) I’ve no way to bore to the necessary tolerance. I can angle the top slide to get fractions of a thou, but what about ‘spring’?

So it’s always going to be trial and error.

Ive re-read your ‘how to’ on the bearings, noting you say to make the soldered stock long enough for both bearings, and – I think – to bore one at a time, which makes sense. Do I bore one, part it off then move the stock out and start again with the next bore, or leave enough stock protruding from the chuck to do both without disturbing the stock? I’d think having the minimum protrusion would be best, but wondering if it’s necessary to re-centre if I loosen 2 jaws and pull the stock forward?

Thanks.

[Ramon WilsonParticipant @ramonwilson3]

I can see your logic Doc about making another shaft if things go awry, but if you'll forgive me for saying so that is an amateurish way of approach.

That is not to be offensive but to say that as a machinist who has the opportunity to control the method that really is the wrong way to go about it – in my mind.

I'm not trying to change your's however, if you are happy to do so then by all means continue but it's not the way most would go about it.

If you machine the adjoining parts first and ream or bore the holes then you have a 'standard' to make the shaft too. As Hopper says too it's much easier to measure accurately the shaft diameter than a small hole.

I have to say that considering 'what part I'm going to muck up – and the easiest way to replace it is not something I consider in my approach to a job, rather how each job/operation can make the next easier and more accurate but as always its down to choice.

Whatever way you approach it I hope it goes well for you – the main thing is to enjoy the process which I'm sure you will

[JasonBModerator @jasonb]

Posted by Ramon Wilson on 31/08/2022 07:46:48:

As Hopper says too it's much easier to measure accurately the shaft diameter than a small hole.

But first you need an accurate measurement of the hole to know what measurement to use for the shaft, So would have to accurately measure the hole anyway.

Doc I would mark out the ctr on both ends of your bearing block, have enough out to do one and then turn the work around to do the other, clocking it true again.

Regarding taper that can result from using a boring bar, this is another good reason to have your shaft or shaft material readily at hand to use as a plug gauge. You will be able to bore until the shaft enters the hole, if it tightens up you know the hole is tapered and can take a spring pass or two until the shaft fits. If you measure the opening of your hole to the nominal size and then stop cutting and take it out of the lathe it will be a lot harder to correct if you subsequently find the hole is tapered.

Edited By JasonB on 31/08/2022 08:24:03

[HopperParticipant @hopper]

Posted by Dr_GMJN on 30/08/2022 13:08:31:

Just another thought: If you made that screw on the stop a 40TPI thread and made a disc to go on the screw head with 25 divisions around it, you would have a micrometer stop with one thou resolution. Bit of work to make but quicker to set in use than Jo blocks. (Or the equivalent metric thread and graduations if that is what you work in.)

I use a graduated handwheel on the leadscrew for the same function. But it is a PITA on the ML7 to disengage the change gears to use it. Leadscrew dog clutch is on the Round Tuit list.

Re hole first vs shaft first, seems there are arguments for and against so all you can do is pick one and give it a go. If you go inadvertently oversize on the hole you can always bore it out and sleeve it and start again.

[Dr_GMJNParticipant @dr_gmjn]

Ramon, I appreciate the comments, but I can’t control the process to the necessary accuracy – that’s the point. I’m not planning on messing up, but I might, so to me it’s logical to plan for that eventuality. Even Sparrey mentioned early on in his book that with the equipment in question, production to measured tolerance is impossible, but machining to fit is normal. In the case of the ML7, I have the exact same equipment…

Jason, yep, that’s logical, thanks.

Hopper, the idea of the bolt was to make it adjustable to pitch similar to how you say, but the reality is I never used it like that.

ETA when I made the stop, I put a clamp and ratchet lever on it, so it’s very quick to adjust or retract as and when:

 

Edited By Dr_GMJN on 31/08/2022 09:32:27

[Ramon WilsonParticipant @ramonwilson3]

Well if a reamed hole isn't accurate enough for this purpose Jason I don't know what is ???

Using a such a long item, the shaft, as a plug gauge with it's potential, of wringing a much smaller part held in a chuck runs a good risk of moving the part in the chuck but I offer my thoughts based on my own experience. As I commented right from the outset – make the hole in the bearing first and machine the outside to suit then use the bearing to size the shaft to a running fit.

No ones mentioned it as yet but once the bearing is split and the solder faces cleaned the diameter is reduced slightly anyway.

One way the bearing is finished and the shaft is reduced until it slips on with a good running fit usually by 'polishing' with a fine file, emery or wet and dry paper. Much easier I would suggest than doing the reverse in a hole with its potential of tapering/bell mouthing over such a short length.

In an ideal world both would have probably been made by two different people to tolerances that would ensure the perfect fit. I can't speak for anyone else but It makes perfect sense to me to be able to measure the shaft diameter easily and potentially more accurately than it does a hole, especially around 12mm or less

 

We will have to agree to differ I'm afraid

Edited By Ramon Wilson on 31/08/2022 10:42:36

[JasonBModerator @jasonb]

Unless Doc is going to buy a bunch of incremental reamers in 0.01mm sizes then he will have to make do with what kit he has. His drawings do not show common nominal sizes except for the 3/8" end so would need separate reamer for each to the sizes on his drawing. You keep mentioning the kit he has so I'll mention it too. Yes a commercial shop may well ream but a non standard size would put costs up, ammature in the home workshop has to make do.

Even then a 12mm H7 reamer could be anything from 12.000mm to 12.018mm and then there are other variables that can affect cut such as material, pilot size, condition and quality of reamer, dry or lubricated, machine or taper. etc

Even if it did cut to size you would not want the same tolerence for all parts, cranks would be light press/tight push fit, flywheel push fit and bearings a running fit.

You are also now saying you will polish the shaft down to a fit, earlier you and hopper ware saying measure the shaft,

Is what I say really any different to a plug gauge mentioned in another recent thread except it's a bit longer and by using the actual part there is no risk of inaccuracy between the part and a separate plug gauge.

Like you I would say it is easier to measure a shaft so why not machine that first to your design size and then fit the hole to suit which only needs measuring until you are close to size then sneak up by trial fit so no accurate measurement of the hole is even needed.

[HopperParticipant @hopper]

It is easier to "sneak up" on an exact diameter on a shaft than inside a hole. Boring bars are inherently springy and bored holes notoriously tapered in smaller sizes where thin boring bars spring a lot. Sizing a hole precisely with a boring bar is difficult. Sizing a shaft OD with a turning tool and emery cloth is machining 101.

The usual way I do such jobs is drill, bore and ream the hole so it is round, straight and parallel, and located. Then turn the shaft to fit it, making final size with emery cloth and oil and "try and fit" it to the hole to get final size. Looser fits in bearings and tighter fits in crank webs can be achieved by how much final polishing is done on the shaft in what location. These are one-off jobs so such minor adjustments are no big deal to achieve the desired fit.

But, that is just the way I do it for general machining, and my experience on model engines is limited to a small handful over the years.

[Ramon WilsonParticipant @ramonwilson3]

I am beginning to think you are being a bit pedantic Jason, surely not?

No way does Doc have to buy a series of reamers in 0.1mm increments – whatever for.

I would assume though he might have the odd couple near what is required but if not then make the holes to a pre-machined plug gauge to any size you desire and then make the shaft to suit.

When I refer to 'polishing' down to size it's taking that last couple of tenths not thou's off to get that fit – of the respective part – just right. Obviously it would be measured down to size, but that last final bit is probably, more likely than not, too much to ask for an old lathe to cope with – it's called 'fitting' don't you know

There was a fair amount of it on this shaft – finished between centres until the bearings, the centre bearing already split, were just able to fit just right. Obviously it would be some machinist indeed to make the centre bearing fit the shaft using the shaft as a gauge.

 

I should point out that even then, once fitting the bearings to the bedplate and clamping up the keeps, the bearings/shaft required further 'polishing' until a good running fit was reached (This is being spun between fingers and thumb BTW no external drive)

No doubt, now its been painted and awaiting assembly that will require doing again – which is why I have advised before – build it up, including painting as you go along, to eliminate any tight spots before moving on to the next stage and ensuring all remains in good running order throughout the build.

It's advise, not dictat. Doc makes the decisions

R

 

Edited By Ramon Wilson on 31/08/2022 12:30:54

Edited By Ramon Wilson on 31/08/2022 12:31:44

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