Stuart Twin Victoria (Princess Royal) Mill Engine

[HopperParticipant @hopper]

Disappointing about not being able to easily mill steel or cast iron without problems, and should not really be the case. What is the black finish on those broken end mill cutters? Are they carbide? Maybe try different brand of cutters, or HSS etc. Sometimes 4 flute cutters are a bit more solid too. And did you try slowing the rpm right down for cast iron?

Edited By Hopper on 07/07/2022 08:23:34

[Dr_GMJNParticipant @dr_gmjn]

Posted by JasonB on 07/07/2022 07:06:11:

I'd actually face one side and saw a bit off, repeat 3 more times. Face the opposite sides of your 4 pieces.

Now with a 3 flute 6mm dia cutter bring the 4 pieces to overall size, using a stop and parallel packing so you can repeat the sizes. Use the side of the 6mm cutter and start with say a 4mm height x 0.5mm stepover cut. Reason for the 6mm is the spindle speed can be higher which means the motor is running where it will have more power, also more mechanical advantage for the machine with a smaller cutter and cutter will be shorter so more rigid.

Then recess the two covers, turn the chests then stitch drill out the waste and mill the cavity

Also suggest you position the parts over to one side of the block rather than in the middle then you can saw off most of the waste down one side prior to milling.

Sorry Jason, I don’t follow. I’m making the two top covers for the valve chests. I’ve already finished the chests themselves – they were Stuart castings I bought ages ago.

Reason I did it like this was I’ve had trouble getting stuff like this all square, so I thought by facing and profiling in one setup I’d be guaranteed as accurate as the mill table.

I also thought it’s easier/safer to grip the work like that for most operations – again in the past work has moved while trying to grip a c. 3mm plate in the vice.

[Dr_GMJNParticipant @dr_gmjn]

Posted by Hopper on 07/07/2022 08:22:20:

Disappointing about not being able to easily mill steel or cast iron without problems, and should not really be the case. What is the black finish on those broken end mill cutters? Are they carbide? Maybe try different brand of cutters, or HSS etc. Sometimes 4 flute cutters are a bit more solid too. And did you try slowing the rpm right down for cast iron?

Edited By Hopper on 07/07/2022 08:23:34

Thanks Ramon. I think they’re carbide cutters.

Over the years I’ve had the mill, it’s never cut ferrous metals very well. In that time I’ve tried a whole range of feeds, speeds, cutter collets, cutter diameters, and machine fettling to no avail.

[SillyOldDufferModerator @sillyoldduffer]

Posted by Hopper on 07/07/2022 08:22:20:

Disappointing about not being able to easily mill steel or cast iron without problems, and should not really be the case. What is the black finish on those broken end mill cutters? Are they carbide? Maybe try different brand of cutters, or HSS etc. Sometimes 4 flute cutters are a bit more solid too. And did you try slowing the rpm right down for cast iron?

Edited By Hopper on 07/07/2022 08:23:34

+1 I suspect the cutters too. That the shell cutter did a reasonable job suggests the machine is reasonably stiff and the motor is adequately powerful. It's not surprising that a smaller hobby mill isn't rigid enough to take aggressive cuts out of steel, or to get through the hard skin sometimes found on cast-iron, but they do work.

Maybe unlucky with the material too: not all metals machine well, which is why I always look for 'free-cutting' in the specification when buying, and am not surprised if a bit of unknown scrap proves difficult.

Could be a case of:

Awkward material + iffy cutters + light mill + inexperience = misery

Dave

Edited By SillyOldDuffer on 07/07/2022 09:19:48

[JasonBModerator @jasonb]

Though by the size of the lump you were cutting the chests too. In that case just face, saw, face and saw again to get two slices then face opposite side before doing the edges.

Look like ARC Premium cutters to me with the dark coating being TiAIN and I've not had any problems with them either HSS or Carbide..

Ron who chips in here sometimes also has an SX2P and manages these materials OK with the same cutters

It's not a bit of scrap DAVE but CI block from a supplier which won't have a skin either.

[HopperParticipant @hopper]

Posted by SillyOldDuffer on 07/07/2022 09:18:52:

+1 I suspect the cutters too. That the shell cutter did a reasonable job suggests the machine is reasonably stiff and the motor is adequately powerful.

That's a good point.

I can mill steel and CI on the vertical slide on the Myford and that is a pretty flimsy, flexible, "make-do" sort of a set up, so would have thought a proper mill would do the job, as it does with the shell cutter so must be capable as you say. Very weird.

[Dr_GMJNParticipant @dr_gmjn]

Posted by JasonB on 07/07/2022 10:05:07:

Though by the size of the lump you were cutting the chests too. In that case just face, saw, face and saw again to get two slices then face opposite side before doing the edges.

Look like ARC Premium cutters to me with the dark coating being TiAIN and I've not had any problems with them either HSS or Carbide..

Ron who chips in here sometimes also has an SX2P and manages these materials OK with the same cutters

It's not a bit of scrap DAVE but CI block from a supplier which won't have a skin either.

Thanks Jason – problem is – how do I do the edges to get them all square. I've had trouble in the past gripping thin work like this, and how do you cut and re-orientate to guarantee squareness? The block sides aren't perfectly square I don't think.

Yes, it's GD 250 iron, from my usual supplier who is very good.

[Dr_GMJNParticipant @dr_gmjn]

Posted by SillyOldDuffer on 07/07/2022 09:18:52:

Posted by Hopper on 07/07/2022 08:22:20:

Disappointing about not being able to easily mill steel or cast iron without problems, and should not really be the case. What is the black finish on those broken end mill cutters? Are they carbide? Maybe try different brand of cutters, or HSS etc. Sometimes 4 flute cutters are a bit more solid too. And did you try slowing the rpm right down for cast iron?

Edited By Hopper on 07/07/2022 08:23:34

+1 I suspect the cutters too. That the shell cutter did a reasonable job suggests the machine is reasonably stiff and the motor is adequately powerful. It's not surprising that a smaller hobby mill isn't rigid enough to take aggressive cuts out of steel, or to get through the hard skin sometimes found on cast-iron, but they do work.

Maybe unlucky with the material too: not all metals machine well, which is why I always look for 'free-cutting' in the specification when buying, and am not surprised if a bit of unknown scrap proves difficult.

Could be a case of:

Awkward material + iffy cutters + light mill + inexperience = misery

Dave

Edited By SillyOldDuffer on 07/07/2022 09:19:48

Thanks S.O.D. you're probably spot-on about the real causes of the issues. I have no baseline for expectations for a mill like this, because I only embarked on this hobby a couple of years ago.

Jason makes an interesting point about using small cutters, running fast. My assumption was that larger cutters would be stiffer, hence give less issues.

[Clive Brown 1Participant @clivebrown1]

Regarding the problems with the end mills. Are you taking off much metal both with the side teeth and the end teeth on the same cut? I've tried to minimise this type of operation on my fairly light-weight hobby mill ever since GHT advised against it in ME years ago. He was writing about milling with a vertical slide. It seems easier on the cutter and certainly improves the finish, especially with steel.

Edited By Clive Brown 1 on 07/07/2022 11:17:37

[JasonBModerator @jasonb]

The one thing that struck me looking at this mornings photos was the dust being produced, can't really call it chips or swarf.

This suggests to me that the cutters have become blunt and are no longer cutting as they should, possibly due to being used on Stuart Castings that some say have hard spots, This could also explain why the insert cutter works as that is less likely to have been blunted than what I assume are HSS cutters.

Now I don't have an SX2P to test on but the SX2.7 is the next one up and not as rigid as my X3, to compensate for the slightly larger machine I chose a bit of low quality cast iron (old gym weight) and took a few cuts. used a similar type of vice.

First with an ARC Premium 6mm HSS cutter, I only have 2-flute in this size but it will do to demonstrate, a 3-flute would be better. Worked out the spindle speed for a modest for me 20m/min cutting speed. Ap – vertical height of cut 5mm as suggested but I upped the Ae- sideways cut depth to 0.6mm which is 0.1D. Fed at what seemed right and looking at the time on the video it's approx 150mm/min would be around 225mm/min if a 3 flute at that spindle speed.

Next took a similar 5mm x 0.6mm cut with a 10mm dia 3-flute cutter from the same source and cutting at the same surface speed though spindle obviously less.

Finally upped the anti and went with Ap of 10mm and Ae of 1mm with the 10mm cutter which is the often quoted cut in makers suggested feeds and speeds.

So if the 2.7 is happy taking 10mm x 1mm cut the next size down SX2P should given sharp cutters be able to remove 1/4 of that eg 5mm x 0.5mm

 

The one thing to notice in all these three cuts is the form of the swarf being produced that shows the cutters are actually cutting not rubbing or forcing the metal off the block.

 

I think there is a tendency to keep using blunted cutters particularly for those without a means to sharpen them as they cost good money. This is another reason to consider using smaller cutters as if you run into a hard spot it will take the edge off a 12mm cuter just as quickly as it will a 6mm one. However the 6mm is a lot cheaper to replace

 

Also if as you say the mill is not capable of taking big cuts then why use big cutters where most of the side will never make contact.

 

Edited By JasonB on 07/07/2022 13:03:43

[Dr_GMJNParticipant @dr_gmjn]

Posted by Clive Brown 1 on 07/07/2022 11:16:40:

Regarding the problems with the end mills. Are you taking off much metal both with the side teeth and the end teeth on the same cut? I've tried to minimise this type of operation on my fairly light-weight hobby mill ever since GHT advised against it in ME years ago. He was writing about milling with a vertical slide. It seems easier on the cutter and certainly improves the finish, especially with steel.

Edited By Clive Brown 1 on 07/07/2022 11:17:37

Clive, no, just one or the other usually.

When I milled the cylinder cover bosses I made a final cut simultaneously on the side and base, but only something like 0.02mm.

[Dr_GMJNParticipant @dr_gmjn]

Posted by JasonB on 07/07/2022 12:21:32:

The one thing that struck me looking at this mornings photos was the dust being produced, can't really call it chips or swarf.

This suggests to me that the cutters have become blunt and are no longer cutting as they should, possibly due to being used on Stuart Castings that some say have hard spots, This could also explain why the insert cutter works as that is less likely to have been blunted than what I assume are HSS cutters.

Now I don't have an SX2P to test on but the SX2.7 is the next one up and not as rigid as my X3, to compensate for the slightly larger machine I chose a bit of low quality cast iron (old gym weight) and took a few cuts. used a similar type of vice.

First with an ARC Premium 6mm HSS cutter, I only have 2-flute in this size but it will do to demonstrate, a 3-flute would be better. Worked out the spindle speed for a modest for me 20m/min cutting speed. Ap – vertical height of cut 5mm as suggested but I upped the Ae- sideways cut depth to 0.6mm which is 0.1D. Fed at what seemed right and looking at the time on the video it's approx 150mm/min would be around 225mm/min if a 3 flute at that spindle speed.

Next took a similar 5mm x 0.6mm cut with a 10mm dia 3-flute cutter from the same source and cutting at the same surface speed though spindle obviously less.

Finally upped the anti and went with Ap of 10mm and Ae of 1mm with the 10mm cutter which is the often quoted cut in makers suggested feeds and speeds.

So if the 2.7 is happy taking 10mm x 1mm cut the next size down SX2P should given sharp cutters be able to remove 1/4 of that eg 5mm x 0.5mm

The one thing to notice in all these three cuts is the form of the swarf being produced that shows the cutters are actually cutting not rubbing or forcing the metal off the block.

I think there is a tendency to keep using blunted cutters particularly for those without a means to sharpen them as they cost good money. This is another reason to consider using smaller cutters as if you run into a hard spot it will take the edge off a 12mm cuter just as quickly as it will a 6mm one. However the 6mm is a lot cheaper to replace

Also if as you say the mill is not capable of taking big cuts then why use big cutters where most of the side will never make contact.

Edited By JasonB on 07/07/2022 13:03:43

Thanks Jason – very useful. I have a 6mm cutter (with the 1mm corner radius) that's hardly been used. I will try to replicate your cuts later on.

The reasoning behind using larger diameter cutters wasn't to take large cuts, but rather because I assumed they'd be stiffer, and the more rigid the system was, the less chance of chatter.

[JasonBModerator @jasonb]

They have more flute length protruding from the collet so the length to dia ratio is not much different.

Also greater distance from bearings and/or head to tip of tool which will magnify any movement you may have.

Edited By JasonB on 07/07/2022 16:09:28

[Ron LadenParticipant @ronladen17547]

Doc, I,m quite surprised that you think your SX2P is horrible when cutting cast iron or steel, thats not been my experience with my SX2P. As Jason mentioned I also use the ARC premium range both HSS and carbide and have had no issues. It shouldnt be the machine if mine is anything to go by, for a small table top mill I,ve always thought it punches above its weight with decent rigidity and more than enough power for its size.

I,ve cut quite a lot of cast and steel and with something like the correct depth of cut, rpm and feed rate to suit the cutter size i dont have any issues. In fact the side cut Jason shows 10mm x 1mm using a 10mm cutter wouldnt be a problem I wouldnt have any worries taking that cut in cast iron, and quite recently I side cut a 15mm x 0.8mm cut along a 4 inch length of cast using a 10mm cutter and it was fine.

If your cutters are sharp ? and your set up is ok I cant quite see why you are having problems. The one thing I would say is that I dont tend to go by what the book says re rpm and feed rates etc I do tend to run my SX2 a bit faster then book values especially with rpm I dont know if that makes any difference or not but its just what I,ve found on my machine and where its happiest.

[SillyOldDufferModerator @sillyoldduffer]

As a clumsy self-taught machinist with absolutely no natural talent I've had more than my fair share of trouble! Starting out I found tools, like hacksaw blades, blunted amazing quickly, which I assumed was normal, or that the tools were cheap and nasty.

I actually had three problems:

• by chance, my collection of scrap metal was all horrible!
• My approach to cutting was either delicately tentative or fast and furious: both are bad!
• I was unable to isolate causes quickly due to imperfect understanding

These problems interacted! I blunted tools quickly and then didn't realise other problems were being caused by the tools I'd ruined. Plus, a strong aversion to spending money kept me loyal to blunt cutters for far too long.

First improvement was replacing scrap with bought free-cutting metal. I'm all for recycling, but be aware scrap metal might be nasty stuff that blunts tools in a blink. Cheap metal, ruined cutter, then nothing but trouble on other jobs until the cutter is fixed!

Second improvement was avoiding too delicate and too forceful cuts. "Let the tool do the work", in other words enough force and speed that edges cut rather than rub, but not so much brutality that the edge is overloaded. Most tools have a sweet-spot were metal is removed reasonably quickly without rapid blunting. There's more to efficient cutting than this simple observation, but it was my main error. Removing swarf, appropriate lubrication, sharing the load between teeth, and rigid work-holding are important too.

Third improvement was me tuning in to the needful. Getting feeds and speeds about right. Better technique and above all quickly homing on what's wrong rather than constantly feeling my way through a fog of uncertainties. Fault finding is often a case of joining the dots, and it gets much easier with experience: I've come to recognise patterns of misbehaviour.

When I started 'poor tools' got almost 100% of the blame for bad results. Now the first suspect is me: I've twigged that the material is important, and has to be held firmly in the machine; that cutters need to be in good condition and work best in a sweet spot; and that thoughtfully eliminating causes is more productive than random guessing. This way, I learned the importance of operating within the limitations of my tools. When stuff goes wrong, I usually find I missed something in the set-up, method or operating parameters.

It's a long process and I still make mistakes. The first time I tackle anything new I'm sure to find gaps in my understanding! Practice and a critical review of how the job went is useful. The forum has been excellent, often casting light into dark places. Pleased to report now my biggest fault is slow progress rather than repeated failures. Most things I attempt work out OK, and failures are usually because I missed something – like a damaged cutter, or forgetting to fully tighten collets.

Dave

Edited By SillyOldDuffer on 08/07/2022 11:08:50

[Dr_GMJNParticipant @dr_gmjn]

All, many thanks for the replies and advice. I’ll post a more complete update tomorrow, but yesterday I had some success using a 6mm and 8mm cutter with – approximately – Jason’s settings.

I think part of the problem has been a) using too large cutters and b) too fast spindle speeds (I have no speed read-out on my machine).

I managed to reduce the CI block to size, although it slipped in the vice at one point and stalled the cutter while conducting the 8mm test run.

I’m now set up ready to mill the recesses in each plate, then surface to thickness. I’ll try that tomorrow.

Cheers.

[JasonBModerator @jasonb]

I'll talk about those vices and their vices tomorrow.

[Dr_GMJNParticipant @dr_gmjn]

Posted by JasonB on 08/07/2022 21:01:19:

I'll talk about those vices and their vices tomorrow.

Hmmm it’s by no means the first time work has slipped in the vice.

I thought I read somewhere that paper shims can help with grip, but as you can see, that didn’t work out too well:

It was this movement of the workpiece that snapped the two previous end mills. Luckily I caught this one in time.

[JasonBModerator @jasonb]

Well I was going to say there are two issues but you have a third user related one there which I will deal with first.

From the look of the sides of your block it appears sawn so the chances of two opposite faces being parallel to each other are slim. Yes a bit of paper, card or thin aluminium will all help with grip but as there is little angular movement in the jaw you will be putting the tightening force onto the block at it's thickest point which from your latest photo was on the right hand side.

The way to grip sawn blocks or castings for their initial cuts is to choose the flattest preferably non convex side and put that against the fixed jaw of the vice, paper can be added. Now on the other side you want close to a central point load which is best applied with a small piece of aluminium between moving jaw and the work. This not only holds the work firmly (3 points of contact) but also helps keep the flatter side against the fixed jaw.

This is the first photo from a section in my book that shows how to deal with a rough block you can see I have aluminium packing at the back and a small piece to give point contact at the front.

[Ron LadenParticipant @ronladen17547]

Doc should you want a cheap spindle speed readout thats easy to fit and 100% reliable then have a look at the one I fitted to my SX2 in the photo below. Available from a well known auction site, I paid 6.50 for mine 3 years ago but I see they are now a tenner but still well worth it.

[JasonBModerator @jasonb]

The other two things that users of this style of vice need to be aware of are:

1. If the pin block is engaged in the rack in such a position that the screw has to go in a long way before the jaw tightens onto the work it will be in a much more vertical position than if the pin block were one notch closer to the work. This results in more tightening force going vertically downwards than horizontally into the moving jaw which reduces the clamping force. So make sure you are not screwing the screw in too far.

2. Slightly related to the above and it has been found on a couple of these type of vices is that if the screw is turned a long way into the pin block making it closer to vertical the end of the screw can touch the mill table. So when you start to feel resistance and think the jaw is tightening it is actually the screw pushing against the mill table

Edited By JasonB on 09/07/2022 07:37:32

[HopperParticipant @hopper]

And it is more common to use a piece of thin typing/computer printer paper in the vice rather than thicker cardboard-like stuff.

You can also make a sort of false jaw that approximates the little extra jaw on the Myford mini vice, by taking a piece of flat bar about the size of your vice jaw and welding or attaching a piece of round bar to it in the position Jason shows. That way, clamping grip is along the full length of the job but the single line of contact with the vice jaw proper allows it to swivel to accommodate out-of-square blocks etc. Less fiddly to set up too, as the little bit of round bar is captive and does not fall down into the gap in the vice etc.

No need for the half-round scallop in the jaw proper. It will still work without it.

Edited By Hopper on 09/07/2022 08:34:16

Edited By Hopper on 09/07/2022 08:35:11

[Dr_GMJNParticipant @dr_gmjn]

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.

[Ian HewsonParticipant @ianhewson99641]

Hi

This is the speed indicator on my mill, magnet held by its own magnetism.

[Ramon WilsonParticipant @ramonwilson3]

Doc – not wishing to pre-empt Jason but like you I began my engineering life as an amateur (1972 ish) And like you I struggled with feeds and speeds but around 1980 I gave up my offshore career and retrained as a milling machinist.

The first thing I was taught was how to square a block in a vise – just as Jason shows. Cut surfaces cannot be regarded as ideal to be gripped in a vice and as someone else has said copy paper is all that's required behind one face – next to the fixed jaw. Card, even thin card will compress and is not advisable.

The second thing that really was a game changer was to be taught about the varying cutting speeds of various materials.

At the time I wrote this down in a little note book – it's still on my shelf and occasionally still gets referred to. It might not be 'au fait' with modern thinking and advise but it works and works well – not only for industrial use (at that time) but now – in the home workshop on the small kit most of us have at our disposal

 

The formula can be reduced to CS x 4 over dia of cutter (or work if on a lathe) which will give the near enough optimum speed

Now I realise much has moved on over the last forty plus years but this has stood me for all of that time – yes I do possess several of the 'posey' manufacturers booklets that show optimum speeds and feeds all of which are the optimum for industrial machines in an industrial environment. I have spent many years in front of a lathe, mill or grinder at work but never felt the need to bring that 'pace' into my home workshop.

Most newbies to the hobby make two fundamental mistakes because of lack of knowledge – either they run largish cutters – say 6mm upwards – too fast and small cutters far too slow. The info on the page above sorts that out immediately.

Finally good cast iron will machine with ease if the speed of the cutter is right – much better to start slow and move up than the other way round. If the machined surface has a shiny glaze to it it's too fast, a nice uniform matt is when you have it right.

Hope that helps a little more.

 

Edited By Ramon Wilson on 09/07/2022 11:42:18

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