Stuart Twin Victoria (Princess Royal) Mill Engine

[HopperParticipant @hopper]

Yes we were taught the old 4CS/Diam formula too, and it still works for me today too. Sometimes basics are basics and don't change. The only thing that has changed is the cutting speed (CS) is higher with today's carbide tools, but the formula holds true nonetheless. I like your chart with the diameters and surface speeds and rpm already worked out as a ready reference. Very handy.

It is easy to forget that cast iron cuts at about half the speed of mild steel. Still seems counterintuitive to me but it definitely is true, as I have found out more than once!

[Ramon WilsonParticipant @ramonwilson3]

Yes Hopper, the ready availability of carbide tooling has certainly brought a new dimension to the home workshop though perhaps not always for the best.

Though I have various carbide cutters to use they only get used on rare occasions when the task really demands it. HSS tooling is a much more versatile material to use in the home work shop as once past their useful life they can be reclaimed even by hand far more easily than carbide can – not to mention being easily converted into further useful tooling if broken.

I'm at the end of my machining days now and whilst I do appreciate that things have moved on (considerably) as you say 'basics are basics'. I've always offered my thoughts on being the best (as in easiest) way to achieve something bearing firmly in mind the limited kit that's at the disposal of most home users. Yes they are those with some lovely kit – even industrial quality – to call on but I'm not one of them so have always 'cut my cloth' etc to what I have in my workshop and even my limited resource can be a lot more than most for some.

I'm not saying that available information should be ignored, just that it isn't always necessary to get the job done to a satisfactory outcome.

Best R

[HopperParticipant @hopper]

Agreed. Sometimes 19th century methodology is still useful in the home workshop, because in those days they had to make do with what they had,which was a lathe and not much more. Time was not so much of the essence in those days — and it is not in my home workshop today either.

[JasonBModerator @jasonb]

Ramon's chart stills hold true, that 20m/min cutting speed I used in the video just falls into his 50-70ft/min and 30m/min would be a good general rule for steel which is not far off his 100ft/min. The other speeds hold true to for HSS. You could probably up it a bit for coated cutters but you are not really able to run at the speeds coating works best at.

You may want to make up a similar spreadsheet with metric diameters and speeds if that is the dia of tool you are most often using as the formula does not work unless you convert diameter to inches.

carbide has been one of the items that has changed the way we can work though it is often at it's optimum as speeds above what most manual hobby machines can run at, some do have a high range that will get you to 5000rpm which suits the smaller cutters on ferrous material though is still a bit below optimum for non ferrous. However high spindle speeds are only useful if you can feed at a rate to keep up with them, you would need some fast wrist action to feed at say 1000mm/min which would equate to turning your SX2P handwheel 500 times in 60secons. Best kept for power feeds (not slow old mechanical drive ones) or CNC machines.

What has changed a lot are the cutters and how they can be used. Back when Ramon was compiling his note book there was not much to choose from just 2-flute slot drills and 4-flute end mills. Now we have 2, 3, 4 , etc flutes. Different coatings and geometries to better suit the specific material being cut not to mention other ways of holding the tooling that does not need the end to be threaded.

Along with this the approach to how you cut has changed Lighter depths of cut and higher feeds have been shown to be more efficient than using a heavy old machine with a lot of grunt behind it slowly chewing its way through a heavy cut. On that is often seen now tends to use a lot of the side of the cutter where the Ap (vertical depth) can be anything from 1 -2 times the diameter and qute often more but Ae (sideways) depth of cut is typically around 0.1D or 10% of the diameter. Although you may not be able to do this on a small machine you can adapt the principal by letting the motor run towards its top speed, and feeding fast so you keep the chip load (thickness per cut) reasonably light for the machines power but not so light that you are just rubbing the surface.

Tis is the type of cut I showed in the video and adjusted to be something the SX2P can handle, rather than the cuts you often see which use a lot of cutter width and little depth which puts all the wear at the ends rather than spreading it along the sides so you get better value out of the cutter. Obviously if you are facing a piece of work that method can't be used.

I still use HSS 95% of the time on the manual mill but the CNC only really gets to use HSS for drill bits. Also looking in the draw under the CNC all but two cutters are 6mm dia or less. Ther eis one 8mm that was bought as I needed the flute length and a 10mm R1 corner cutter that's not been used unlike the 6mm and 4mm ones. The CNC does have a 5000rpm spindle so I can get the best out of them.

 

Edited By JasonB on 09/07/2022 13:31:58

Edited By JasonB on 09/07/2022 13:44:18

[Ramon WilsonParticipant @ramonwilson3]

Good post Jason and yes that was a long time ago. The terminology has changed some too but to this old 'dino-sore' a centre cutting 'endmill' is still a 'slot drill' – three flutes or more

Regarding actual cutter size and method I would hazard a good guess that 90% of my machining is done as you say – with a slightly higher RPM, lighter cuts and a high-ish hand fed feed rate but not, I stress, on cast iron. To boot most of it is done with HSS 6mm FC3 throwaway cutters too. This puts much less strain on the Linley mill though it's sturdy enough to take more of course.

Coatings are another matter but again I don't think the benefits – on home based basic kit – outweigh the extra cost. That said one of the best wearing cutters I used both at work and home was a Presto 6mm TiN coated FC3. At work we would only use Clarkson, Dormer or (agh! name escapes me – sign of the times I'm afraid **) throw away cutters but I was convinced by a sales rep to try this Presto brand. Well the small diameters lived up to 'expectation' and had but a short life but the 6mm' s just went on and on, far in excess of anything we got out of Clarkson and others. The only coated cutter, I would say, that I used personally to have shown any benefit over non coated. This is long before CNC appeared in our workshop so Bridgeports only!

I guess the problem is now, one of manufacture. I bought some TiN coated cutters some time back from ARC but they do not perform as well as I'd hoped for I'm afraid to say – they very quickly wear and soon begin to rub.

One thing that soon became apparent – there are always easier ways to do most things but it's best to assume there are few shortcuts! They virtually always end in disaster .

Best – R

 

** Osborne?

Edited By Ramon Wilson on 09/07/2022 14:09:42

[Dr_GMJNParticipant @dr_gmjn]

Thanks everyone – I will digest all that later on. I just wanted to post some progress as opposed to problems. So here is a summary of the work on the covers. This is the second attempt:

Smaller cutters, smaller cuts, lower speed:

Surfacer the top, so all square:

Co-ordinate drilled the holes, deep enough to get two slices:

Hacksawed the first slice of, re-faced, then sawed the second one off:

Then cleaned up the sawn faces:

[Dr_GMJNParticipant @dr_gmjn]

Then setup in the rotary table, centering on the oiler hole. This is what the blanks looked like:

I set up an air line to blow the chips away, I didn’t want them getting stuck in the recess:

Milling the outline:

Then rotated the table around the central hole to give a radiussed pad:

Then tapped the 5BA threads for the oilers (which I need to make):

Then faced to the correct thickness:

Result:

Primed:

Test fitted to the other bits:

Might not look much at the moment, but there is a lot of work just in those assemblies…

[Ramon WilsonParticipant @ramonwilson3]

Well you got there in the end Doc and that's what matters but I will say you would have been a difficult apprentice to teach

Holding directly on sawn surfaces in a vice for milling even with paper is an accident or a ruined part waiting to happen. It's not just the part either, self safety and the damage to the machine and cutter needs bearing in mind too. 'Catching a crab' as we refer to it around here when you least expect it is one thing (and yes I've had a few over the years) but working in a manner likely to create the situation is not really good practice.

Your enthusiasm to get on reflects my own in early days but the best advice I had from a sage old machinist at the time was "You need to slow down to speed up" Took me a while to realise the significance of that but it eventually dawned and he was absolutely right

I guess that's you near back on the Vulcan now then. The Phantom is going well but a trip to Hannants is called for before the next phase can get going

Stay well

Best – R

[Ramon WilsonParticipant @ramonwilson3]

Hah! looks like our posts crossed!

Very nice result Doc, I can well appreciate the work and effort you have put in to get there, they certainly look the business

Regards – R

[Dr_GMJNParticipant @dr_gmjn]

Posted by Ramon Wilson on 09/07/2022 18:05:47:

Well you got there in the end Doc and that's what matters but I will say you would have been a difficult apprentice to teach

Holding directly on sawn surfaces in a vice for milling even with paper is an accident or a ruined part waiting to happen. It's not just the part either, self safety and the damage to the machine and cutter needs bearing in mind too. 'Catching a crab' as we refer to it around here when you least expect it is one thing (and yes I've had a few over the years) but working in a manner likely to create the situation is not really good practice.

Your enthusiasm to get on reflects my own in early days but the best advice I had from a sage old machinist at the time was "You need to slow down to speed up" Took me a while to realise the significance of that but it eventually dawned and he was absolutely right

I guess that's you near back on the Vulcan now then. The Phantom is going well but a trip to Hannants is called for before the next phase can get going

Stay well

Best – R

Thanks Ramon. Just to clarify – The pictures I posted just now of the sawn block being machined were not from today, but – I think – from previous to when people pointed out the issues of holding it in the vice like that. Next time I’ll do it differently. The covers I worked on today had machined square sides, so presumably should have been ok to clamp as I did in the vice? I had no problems with slipping anyway.

I used reduced spindle speeds today, and had a much better experience!

Ill carry on with this I think, and fit the Vulcan in when I can. Problem is I airbrush in the same vicinity as machining, so I have to vacuum/degrease everything before risking a spraying session.

[Ramon WilsonParticipant @ramonwilson3]

As an aside Doc – how are you going to bring the 'steam' (air) in if you are mounting oilers on the steam chest. Do you have an inlet in the side of the valve chest that's out of sight in those images

Most large stationary engines had steam directly into the top face of the cylinder where a larger surface are allowed for a bigger inlet valve Whilst there would no doubt be oilers mounted on the steam chest the steam inlet would usually be there too.

This is how I did mine if it's of use

The throttles for the governor are within the blocks. I didn't make butterfly types but rotary ones similar to a model aircraft engine carb. Obviously if it's a twin set up unlike a compound the governor should control both cylinders

Hope that's of use

[Dr_GMJNParticipant @dr_gmjn]

Ramon, the oilers will have sealed caps, so remove the cap, add oil, replace the cap. They won’t be open ‘drip’ oilers. Alternatively, a short bolt could be used (but wouldn’t look as nice).

The throttles will be as per the plans – butterfly valves. I suppose the advantage of these is that they are to a degree balanced.

[Ramon WilsonParticipant @ramonwilson3]

Thanks Ramon. Just to clarify – The pictures I posted just now of the sawn block being machined were not from today, but – I think – from previous to when people pointed out the issues of holding it in the vice like that. Next time I’ll do it differently. The covers I worked on today had machined square sides, so presumably should have been ok to clamp as I did in the vice? I had no problems with slipping anyway.

I used reduced spindle speeds today, and had a much better experience!

Ill carry on with this I think, and fit the Vulcan in when I can. Problem is I airbrush in the same vicinity as machining, so I have to vacuum/degrease everything before risking a spraying session.

Yes, I was referring to your previous images and not those on the covers.

The main time I use paper is for when a part has minimal clamping pressure either due to its set up up or when I don't want to use to much pressure on a weak part. The increase in grip per se can be eased as it makes a considerable difference – relative to the clamping pressure – in such a situation

I'm fortunate in having two spaces to keep the two separate but often that in itself raises 'conflict' – which one to be in!

Which ever way you go – enjoy it

[Ramon WilsonParticipant @ramonwilson3]

Posted by Dr_GMJN on 09/07/2022 18:31:38:

Ramon, the oilers will have sealed caps, so remove the cap, add oil, replace the cap. They won’t be open ‘drip’ oilers. Alternatively, a short bolt could be used (but wouldn’t look as nice).

The throttles will be as per the plans – butterfly valves. I suppose the advantage of these is that they are to a degree balanced.

The oiler on mine is that point on the top of the central manifold. I had originally intended to fit a working oiler plumbed to that point but that never happened. The engine was displayed a lot, originally on steam then on air. Oiling was carried out by removing the plug, squeezing a slug of steam oil in from a syringe and replacing the plug. On steam that would last quite a while but virtually all day on air.

When I have run my other engines as such I just squeeze the oil in to where the airline enters. I always use steam oil even on air – works well without emulsifying.

[Dr_GMJNParticipant @dr_gmjn]

Thanks Ramon.

By the way, rewinding a bit, this was the basic principle I was using to square the block (although obviously my technique to grip the sawn faces was wrong):

**LINK**

And to be fair in the end it worked ok.

[Ron LadenParticipant @ronladen17547]

Posted by Dr_GMJN on 09/07/2022 10:42:32:

Thanks all – I did a similar plane/point clamp with the 10V cylinder (IIRC), but I assumed this sawn block would be close enough to parallel. Anyway – lesson learned.

Ron – The only issue with that rpm sensor is that you can’t then fit the upper bearing cap. I was told by Arc that it’s important to always replace it to keep debris out of the bearings.

Could the speed control dial be calibrated instead?

Jason – is there a simple calculator for speeds and feeds for common model engineering materials/cutter types?

About to mill the recesses – wish me luck!

Cheers.

I have a slot in the cap which allows the cap to fit down over the sensor, having said that I more often than not forget to replace the cap but in 3 years I have not had any debris up there and swarf never gets up there.

Have you read the Howard Winwood review on the SX2P, you probably have but if not you can find it on the SX2P page on the ARC website by clicking the "More" tab which is next to the specification tab. He has some good mods on there one of which is adding a forward/reverse switch its cheap and so simple to do. I added it to mine as it allows tapping on the machine which is good if you have a number of holes to thread. I can tap up to M6 in alu and up to M5 in cast and M4 in steel.

Re spindle rpm, yes you can calibrate the speed control I did mine before I fitted the hall sensor. I have a handheld digital tacho from my R/C aircraft days and used that to find a number of speeds between zero and 2500 rpm. Though for the low cost of the Hall sensor and digital readout I think it more user friendly having the display.

[Ramon WilsonParticipant @ramonwilson3]

Posted by Dr_GMJN on 09/07/2022 23:28:39:

Thanks Ramon.

By the way, rewinding a bit, this was the basic principle I was using to square the block (although obviously my technique to grip the sawn faces was wrong):

**LINK**

And to be fair in the end it worked ok.

I agree but your crab could have been much worse and caused more damage than it did.

I was made aware of this method to quickly and initially square a block only recently and yes it's an excellent way to do it, when the work design warrants it, but as you've found, the block needs to be faced first in order to be held securely to do it.

'Blocking out' – to my mind is something that should always be considered as a first op before machining to dimension begins – once again you 'know' it's square if you do. I would think that virtually everything that I've made from scratch has always begun life as such.

Here's an example – this could have begun from a sawn off block straight in the lathe but blocking first gave firm reference faces – the turned face and bores the first datum finished to dimension from which all else is referenced to – much more difficult to create if if the block was still sawn

Here's the result

I'm now off to put some more into the F4 – enjoy your day

Best – R

[JasonBModerator @jasonb]

As Ramon says if you look back at any of my build threads the description of many parts starts with "square up a suitably sized block" or similar before any machining of the part starts. Sometimes the initial block is left oversize, sometimes to final size depending on what is being done to it. At the very least you want to do two opposite faces if holding in the vice.

Likewise on the lathe of you have a round casting you can often grip it by a fettled cast face to just skim the opposite end so you have good jaw contact when you flip it end for end to do the more critical cuts to finished size. See current build thread

[Dr_GMJNParticipant @dr_gmjn]

Ron, yes I read the article you mention some time ago. In some ways I thing calibrating the dial would be better for me – one less modification to make!

Ramon, Jason,

Yes, that’s what I was trying to do – “square the stock”, but in order to do that I first had to grip the rough block. I think (apart from the cutting parameters), all I’ve done fundamentally wrong here is not using a plane/line contact to hold the sawn block?

I could have gone down the route in the video I posted, but since I was only slicing the already squared and dimensioned parts off the top of the block (the bits being gripped were irrelevant to the parts being made) it didn’t seem worth adding another load of operations to upend the block in the vice to grip it with the machined faces.

[JasonBModerator @jasonb]

You were lucky, a broken cutter or stripped plastic gear may have had a different worth let alone something more serious.

I've a few holes in the fire door and block wall behind where I feed into my tablesaw which act as a reminder to take care and the Riving knife and crown guard were in place when they happened.

[Dr_GMJNParticipant @dr_gmjn]

Posted by JasonB on 10/07/2022 13:02:22:

You were lucky, a broken cutter or stripped plastic gear may have had a different worth let alone something more serious.

I've a few holes in the fire door and block wall behind where I feed into my tablesaw which act as a reminder to take care and the Riving knife and crown guard were in place when they happened.

I’ve still not found the end of the mill that broke off. Didn’t even make a noise against whatever it hit…

[Ramon WilsonParticipant @ramonwilson3]

Hate to put my safety hat on Doc but that's exactly what I meant too – you'd have found it had it hit you in the face

The idea that the video shows is indeed a quick way to ensure 5 sides of a square or rectangular block are true to each other and is one tried and endorsed but both Jason and I are trying to get you to see that no matter how good the surfaces look when sawn the chances of them being parallel are pretty slim.

Had you have taken a skim over all side faces of the block beforehand the next time you pick it up it will pop straight in the vise – to my mind it's a bad habit to get into and one which will eventually lead to a decision 'not to do that again' but then of course by then something will be truly spoilt – workpiece, machine or flesh – potentially all three together.

Each time you grip something like that in the vise – packing or not – you will be straining the vise beyond it's design parameters at the very least.

Just saying!

 

Best – R

 

Edited By Ramon Wilson on 10/07/2022 14:20:41

[Dr_GMJNParticipant @dr_gmjn]

Guys – yes, I understand the safety issues – I’ve not re-done the same mistake. As I said, the images I posted were of what I did before the issue/solution was pointed out.

As an aside, when the mill broke, I hade a polycarbonate screen in front of the cutter – to stop the chips flying all over me and the garage as much as anything.

[Dr_GMJNParticipant @dr_gmjn]

I think I'll have a change from the cylinder end, and machine the main bearings:

Obviously they need a good initial clean-up, but I was wondering the best way to proceed? The instructions are for a single cast version that you cut in half, re-attach with solder and studs/nuts, before machining the bore. The ones I've got are in two cast halves. I was thinking:

1) Mill the base flat, but leave it a bit thicker than final dimension.

2) Mark-out the bearing split line (based on height measurements of the cylinder centreline as mounted to the base). Hopefully this figure should pretty much match the figure specified.

3) Stand on milled base, clamp sides, and mill the bearing split line (making sure once assembled it will end up in about the right place to keep the boss concentric with the cast upper cap).

4) Mill the cap bearing face (again making sure when the boss is cleaned up it will be concentric with the cast outer profile of the upper surface), then mill the oil cup face.

5) D&T the cap bolt holes and secure the halves together (don't bother soldering).

6) Put in 4-jaw and bore or ream the hole. This is what the instructions say, but I was thinking the location of the part just on the narrow base face and oil cup face was a bit sketchy for getting the bore dead square to the crankshaft axis?

7) Turn & face the bosses (these are already undersized in terms of width, so I guess the eccentric will need some compensation to get the right offset).

8) Using the boss faces as datums/clamping surfaces, re-mill the base to be the correct thickness – this should also ensure it's square to the axis (see my assumption in 5).

9) Mill to of base ears and base mounting slots.

What do you think?

Thanks.

[JasonBModerator @jasonb]

Put them in a cupboard and start from scratch, those look to be 7/8" ctr height ones not 5/8" that you want. It will be easier than trying to cut down and reassemble what you have.

[Author]

Posts