Stuart Twin Victoria: Advice & General Questions

[Dr_GMJNParticipant @dr_gmjn]

I’m re-reading the articles in more detail, and I’ve a question about connecting rods:

In Part VI – “Connecting Rods”, It says I need two pieces of 3/8 in. x 5/16 in. mild steel, each about 6 1/4 in. long”

It then goes on to detail how to turn this to form the round connecting rod, with rectangular ends.

It mentions fitting a carrier. I think this is for turning between centres? Why would you do this if one end could be secured in the 4-jaw chuck (as outlined beforehand in order to centre drill both ends of the rectangular section)?

I can’t think it’s for accuracy or repeatability, because firstly you’ve just used the 4-jaw to centre-drill the ends, so the centre drillings themselves are only as accurate as the 4-jaw setup, and once machined there’s no need to ever put it back in the lathe; in fact you’re going to file one of the centre marks away to form the rounded end at one side.

It does highlight that the centre marks should be within a thou of each other. This seems extreme considering that the part isn’t rotating or fitting anywhere with a critical axial clearance once assembled. Isn’t the machining of the circular section middle bit just cosmetic?

I’ll do it as per the instructions, but I’m just wondering what the thinking is behind the process.

Thanks.

[Ramon WilsonParticipant @ramonwilson3]

Did you not see my last post Doc – last post on page 3?

A good bench grinder is essential – minimum of 6" wheels for shaping. I have an 8" for that and a small Slibette 5" for tweaking the cutting point. As said I have used HSS for many years but only worry about the very point that cuts the metal – the rest of the shape is unimportant as long as there is clearance.

Heres an example of a very effecient boring bar made from a redundant slot drill in a mild steel holder – 4BA screw. Doesn't look pretty but works perfectly.

And another using the shank of an FC3 throw away cutter (very high quality HSS for this purpose) ground into a parting tool for doing deep fins on an IC engine. Similar tool holder – other end)

Ideal for radii, screw cuttting, parting etc etc the limit of this tooling is your imagination – I have tin full of these little shanks ground into all sorts of shapes that get 'retuned' as required. You don't need a vast collection of expensive (relatively) HSS square blanks.

Depends on what you want out of it – nice tooling to sit on the bench and look good when you're not using it or something that doesn't but does do the job exactly as you want.

Grinding tools is not a black art but it does take practice – the more you do the easier it gets and the better you get at it. Unless you try though you won't know.

Grinding square blanks with precise clearance angles is just not important. As long as the tool has enough clearance on the three faces then all that is required to get right it just that part that does the cutting. If you don't get it quite right for the material – eg a poor finish, chatter etc then it's just a matter of a slight tweak at the point to find what does. Obviously a knowledge of the basics of cutting angles for varying materials is required but they don't have to be precise all over.

It's easy to get bogged down on thinking that expensive inserted tooling is required to achieve a good result -especially expensive if you need something for just one job – but in my opinion nothing beats a freshly ground HSS tool and especially so if you are machining brass/bronze/gunmetal.

Ramon

Edited By Ramon Wilson on 24/10/2020 23:05:25

[Dr_GMJNParticipant @dr_gmjn]

Posted by Ramon Wilson on 24/10/2020 23:00:27:

Did you not see my last post Doc – last post on page 3?

A good bench grinder is essential – minimum of 6" wheels for shaping. I have an 8" for that and a small Slibette 5" for tweaking the cutting point. As said I have used HSS for many years but only worry about the very point that cuts the metal – the rest of the shape is unimportant as long as there is clearance.

Heres an example of a very effecient boring bar made from a redundant slot drill in a mild steel holder – 4BA screw. Doesn't look pretty but works perfectly.

And another using the shank of an FC3 throw away cutter (very high quality HSS for this purpose) ground into a parting tool for doing deep fins on an IC engine. Similar tool holder – other end)

Ideal for radii, screw cuttting, parting etc etc the limit of this tooling is your imagination – I have tin full of these little shanks ground into all sorts of shapes that get 'retuned' as required. You don't need a vast collection of expensive (relatively) HSS square blanks.

Depends on what you want out of it – nice tooling to sit on the bench and look good when you're not using it or something that doesn't but does do the job exactly as you want.

Grinding tools is not a black art but it does take practice – the more you do the easier it gets and the better you get at it. Unless you try though you won't know.

Grinding square blanks with precise clearance angles is just not important. As long as the tool has enough clearance on the three faces then all that is required to get right it just that part that does the cutting. If you don't get it quite right for the material – eg a poor finish, chatter etc then it's just a matter of a slight tweak at the point to find what does. Obviously a knowledge of the basics of cutting angles for varying materials is required but they don't have to be precise all over.

It's easy to get bogged down on thinking that expensive inserted tooling is required to achieve a good result -especially expensive if you need something for just one job – but in my opinion nothing beats a freshly ground HSS tool and especially so if you are machining brass/bronze/gunmetal.

Ramon

Edited By Ramon Wilson on 24/10/2020 23:05:25

Thanks Ramon, yes I read all your posts. I have a bench grinder, but I think I might need a much finer grade of wheel is what I was thinking in my subsequent post. I’ve got some old HSS tools that Ive never really used. I might try grinding a radius on one and having a go at Jason’s draw geometry on some scrap using the fly cutter for starters. Nothing to lose I guess.

[JasonBModerator @jasonb]

I really don't have anything special in the way of grinders, Just the 6"bench grinder by Dad bought when I was in my teens, did fit a green grit wheel to one side for brazed tip tools and have been "thinking" about putting a slightly better rest on it for the last 40yrs! The cheap Clarke belt sander gets used as much if not more than the grinder these days to shape and sharpen HSS.

As you have some HSS you have nothing to loose giving it a go, may be worth looking at the draft angle on your 10V to see what Stuart's typically used.

Having a ctr hole in each end allows you to easily swap the part around and end for end and it will always go back in on exactly the same axis, with the best will in the world that is not easy to do with a 4-jaw. On this particular part there does not seem any need for repositioning. However I make sit easy to do things like add a "fish belly" to a rod with the top slide or taper attachment left at one setting by tapering one end then flipping the part end for end and doing the other to the same handwheel settings

[Ramon WilsonParticipant @ramonwilson3]

Posted by Dr_GMJN on 24/10/2020 22:44:10:

I’m re-reading the articles in more detail, and I’ve a question about connecting rods:

In Part VI – “Connecting Rods”, It says I need two pieces of 3/8 in. x 5/16 in. mild steel, each about 6 1/4 in. long”

It then goes on to detail how to turn this to form the round connecting rod, with rectangular ends.

It mentions fitting a carrier. I think this is for turning between centres? Why would you do this if one end could be secured in the 4-jaw chuck (as outlined beforehand in order to centre drill both ends of the rectangular section)?

I can’t think it’s for accuracy or repeatability, because firstly you’ve just used the 4-jaw to centre-drill the ends, so the centre drillings themselves are only as accurate as the 4-jaw setup, and once machined there’s no need to ever put it back in the lathe; in fact you’re going to file one of the centre marks away to form the rounded end at one side.

It does highlight that the centre marks should be within a thou of each other. This seems extreme considering that the part isn’t rotating or fitting anywhere with a critical axial clearance once assembled. Isn’t the machining of the circular section middle bit just cosmetic?

I’ll do it as per the instructions, but I’m just wondering what the thinking is behind the process.

Thanks.

If memory is correct is not 3/8 x 5/16 the finished size of the big end section? If so then it really is not a good idea to use stock material as finished sizes.

This really is a component that is so much better made from round bar – a bit longer than required – centred each end for mounting between centres just in case as Jason suggests then, milled to a square section (it doesn't have to be a fully square section just four faces for reference for cross drilling) the entire rod is machined on both lathe and mill and finally parted off from the centred ends. Little, if any, distortion – nice to machine in EN1a and to exact size and squareness where needed.

Just another option on the advice you seek – I know what I would prefer over working with flat bar but it's your choice.

One of the things I have always borne in mind is to try to ensure where posible that whatever op I'm doing leads to accurate holding for the next.

Ramon

[Nigel McBurney 1Participant @nigelmcburney1]

I agree with Ramon,avoid square/rectangular material ,machine from round stock,and use HSS for all this turning.Carbides ok for making large batches of parts as there is less tool wear,or for roughing out as the carbide chip breakers produce compact short chip swarf. The 1mm cutting disc in an angle grinder used to rough out tools from hss bits,does save a lot of time compared to grinding lots of material to dust on a conventional grinding wheel.

[Dr_GMJNParticipant @dr_gmjn]

Ramon, Nigel,

Yes, stock size is finished size (only at one end). I did ask why not simply use round stock and mill the ends, but deleted the question before posting. I concluded that the size of stock round bar required to get the largest rectangular end, would be pretty big and cause more wastage of material. I think this is the sole reason rectangular stock was specified.

Id be happier using round, purely from the distortion pint of view.

Thanks both. Another amendment to the stock order list!

[JasonBModerator @jasonb]

The other easy way to save a lot of time grinding is to start with small section HSS in the first place if you only want a small tool. Had a try to see what my sketched profile would look like just using a 3/16" sq tool I had been using for turning hence a bit too much sticking out the back.

I'm not averse to using flat stock particularly if the rod doe snot have a forked end which can tend to close up, This pile of bright and black bar………

…………….Stayed true enough on my Easton & Anderson

[Ramon WilsonParticipant @ramonwilson3]

Proof is in the pudding Jason and they certainly have come out well

It's all a matter of choice – I've certainly stuggled at times with stresses in material – mainly at work and it can be frustrating if it goes wrong but it's not impossible as you show – I just look for the point of least resistance.

Another alternative to flycutting is to simply shape the corners of an end mill or slot drill to the approximate radius required and use as normal. This is something I do a lot to put fillets in corners when milling (and chamfering) I do flycut on occasion but it's usually as a last resort or blocking out aluminium for I/C engines but much prefer to overlap mill to achieve a flat surface. Incidentally learning to tweak the corners of a cutter can extend the use of a cutter considerably and it's particulrly beneficial on machining 'brasses'

Edited By Ramon Wilson on 25/10/2020 11:04:13

[Anonymous]

Posted by Ramon Wilson on 24/10/2020 23:00:27:

Grinding square blanks with precise clearance angles is just not important. As long as the tool has enough clearance on the three faces then all that is required to get right it just that part that does the cutting. If you don't get it quite right for the material – eg a poor finish, chatter etc then it's just a matter of a slight tweak at the point to find what does.

I agree with Ramon, there's nothing difficult about grinding HSS tools. It's simply a case of understanding the angles. None of which need to be precise, just done by eye. I use a 5" Slibette (bought by my father 50 odd years ago in Cooks of Bedford) for grinding. It's got a coarse (46 grit) aluminium oxide wheel on one end and green grit wheel on the other end for grinding TIG welding electrodes. I also have a 8" Wolf grinder with an 8" wheel, but that's very fine and doesn't get used much. If I need to remove a lot of material I'll mill the toolbit first.

I use a lot of rectangular steel section, but mostly hot rolled rather than cold drawn. My conrods were hogged out of hot rolled bar on the horizontal mill before turning the taper and transition curves on the lathe:

I've never built any of the Stuart models so it's time for me to drop out of this thread as I can't add anything pertinent.

Andrew

[Dr_GMJNParticipant @dr_gmjn]

Re. tool grinding, this is the wheel I've got, I think it needs to be much finer (and un-worn!):

Any recommendations – it's 6" diameter, 1/2" spindle and about 5/8" wide. Thanks.

[Dr_GMJNParticipant @dr_gmjn]

Posted by JasonB on 25/10/2020 06:45:16:

I really don't have anything special in the way of grinders, Just the 6"bench grinder by Dad bought when I was in my teens, did fit a green grit wheel to one side for brazed tip tools and have been "thinking" about putting a slightly better rest on it for the last 40yrs! The cheap Clarke belt sander gets used as much if not more than the grinder these days to shape and sharpen HSS.

As you have some HSS you have nothing to loose giving it a go, may be worth looking at the draft angle on your 10V to see what Stuart's typically used.

Having a ctr hole in each end allows you to easily swap the part around and end for end and it will always go back in on exactly the same axis, with the best will in the world that is not easy to do with a 4-jaw. On this particular part there does not seem any need for repositioning. However I make sit easy to do things like add a "fish belly" to a rod with the top slide or taper attachment left at one setting by tapering one end then flipping the part end for end and doing the other to the same handwheel settings

I'd missed this post.

I'd forgotten: I've got a Rexon belt sander – I used to use it for profiling model glider wing ribs. I've got some new #240 abrasives for it. Also a linisher. They're just B&Q specials, but have performed very well over the years of general garage use:

I also found these spare wheels:

Unfortunately most of the markings are no longer legible. Do you think any of these would be suitable for HSS tool grinding?

[JasonBModerator @jasonb]

Looks in better nick than mine

[Dr_GMJNParticipant @dr_gmjn]

Posted by Ramon Wilson on 25/10/2020 11:03:31:

Proof is in the pudding Jason and they certainly have come out well

It's all a matter of choice – I've certainly stuggled at times with stresses in material – mainly at work and it can be frustrating if it goes wrong but it's not impossible as you show – I just look for the point of least resistance.

Another alternative to flycutting is to simply shape the corners of an end mill or slot drill to the approximate radius required and use as normal. This is something I do a lot to put fillets in corners when milling (and chamfering) I do flycut on occasion but it's usually as a last resort or blocking out aluminium for I/C engines but much prefer to overlap mill to achieve a flat surface. Incidentally learning to tweak the corners of a cutter can extend the use of a cutter considerably and it's particulrly beneficial on machining 'brasses'

Edited By Ramon Wilson on 25/10/2020 11:04:13

Looks like 1/2" dia. mild steel bar would accomodate the rectangular ends with minimal waste. Also, it would only be under 4 mm to remove on radius, to turn down to the minimum diameter of the circular section part. For what it's worth in material costs (only a few £'s), I'll get both, make a start and see what happens. Likewise with tool grinding. I need to sort it so might as well make some mistakes and start learning.

I've never really had any issues at all with fly-cutting on the mill – always got good surface finish, no chatter. Milling on the other hand has been problematic for me from day 1 on the SX2P, especially side milling. Chatter and 'ringing' never seem far away on anything from steel to aluminium, slot drills, end mills, cheap/premium tooling. Anyway, that was a different thread altogether. I suppose building the 10V, and it actually working, means that it wasn't that much of an issue for parts of that size.

Thanks all.

[Ramon WilsonParticipant @ramonwilson3]

At 6" you have a suitable grinder but is that a wire wheel on the other end of your linisher? That could be your second finer grit wheel if so. The wheel on your other grinder certainly needs dressing – and would be ideal for roughing. Star wheel dressers do work but do so ferociously – have every thing covered up with something disposable and a vacuum held close by by a helper will be a big bonus to keep dust to a minimum – Better to do this outside if you can. Fine truing can be done by diamond if you have one. 46 grit for roughing and 60 for finishing is about ball park for HSS. Finer grit is okay for finishing but will glaze over quicker. Horses for etc

If you are happy with flycutting then go for it. Sound though like you may possibly have some bearing issues with your mill spindle if you experience excessive chatter/ poor finish when cutting on the side. What size cutters are you basically using. I would say that 85% of my machining even often on large parts are done with 6mm or 8mm throw away cutters – small cuts at higher speed and fast feed rates certainly takes the strain off the machine and removes metal just as quickly overall as a larger slower cutter will. Does mean a lot of handle swinging though. I do have a good range of cutters to choose from but definitely the most used (worn) cutters lying redundant in a box are mostly 6mm and 1/4 FC3.

Regards – Ramon

Edited By Ramon Wilson on 25/10/2020 13:37:53

[Dr_GMJNParticipant @dr_gmjn]

Posted by Ramon Wilson on 25/10/2020 13:37:29:

At 6" you have a suitable grinder but is that a wire wheel on the other end of your linisher? That could be your second finer grit wheel if so. The wheel on your other grinder certainly needs dressing – and would be ideal for roughing. Star wheel dressers do work but do so ferociously – have every thing covered up with something disposable and a vacuum held close by by a helper will be a big bonus to keep dust to a minimum – Better to do this outside if you can. Fine truing can be done by diamond if you have one. 46 grit for roughing and 60 for finishing is about ball park for HSS. Finer grit is okay for finishing but will glaze over quicker. Horses for etc

If you are happy with flycutting then go for it. Sound though like you may possibly have some bearing issues with your mill spindle if you experience excessive chatter/ poor finish when cutting on the side. What size cutters are you basically using. I would say that 85% of my machining even often on large parts are done with 6mm or 8mm throw away cutters – small cuts at higher speed and fast feed rates certainly takes the strain off the machine and removes metal just as quickly overall as a larger slower cutter will. Does mean a lot of handle swinging though. I do have a good range of cutters to choose from but definitely the most used (worn) cutters lying redundant in a box are mostly 6mm and 1/4 FC3.

Regards – Ramon

Edited By Ramon Wilson on 25/10/2020 13:37:53

Cheers Ramon,

The spindle bearings are fine. The mill is new – or at least first got used this May after buying it last year. I can only think that the tramming process – using shim steel under the column bolts, doesn't give enough bearing area and is causing some kind of resonance. I'm using 6/8/10mm end mills or slot drills. It's mainly side milling that gives the issues. The end of the sample aluminium base section I posted yesterday for example is about a 20mm deep x 10mm wide section, and when facing the ends to neaten it up, the cutter squealed like a pig no matter the speed, depth of cut, climb, not climd or whatever. I was trying to face it using the full depth of a 10mm end mill. Maybe it's just me I dunno. Fed up with it TBH, I just try to avoid it now.

When you say "throw away cutters", what do you mean by that? If you mean cheap, then I had some of those, and folks on here told me to buy premium stuff because the cheap ones were probably contributing to the issue.

I added an x-asis power drive (just a dc motor and speed control through a dog clutch) that reduces handle spinning on longer parts (and often gives me improved surface finish on wide surfaces).

Anyway, I'm currently finalising the materials list, and converting the drawings to metric, then I need to convert the ML7 to wide bed format to get rid of some wear, and add some slide bearings. Then I'm good to get on with machining again.

I'll just crash on with grinding some of the HSS tooling I've got, but never use, and see what happens on some test material.

[JasonBModerator @jasonb]

It may simply need the bearing preload adjusting, when my X3 arrived the adjusting nuts were actually loose.

Throwaway cutters is the term used for the small usually under 6mm cutters though they can be had upto 10mm dia with a Weldon (sidelock) shank. They are not worth industry sharpening so have become known as throw away I also use them a lot as they are quite economical and the 3-flute design is a good all rounder. I usually get Hertel brand from MSC when they have them on offer, though not listed this month.

They work well on aluminium but the aluminium specific cutters are better still.

[Dr_GMJNParticipant @dr_gmjn]

Posted by JasonB on 25/10/2020 17:13:11:

It may simply need the bearing preload adjusting, when my X3 arrived the adjusting nuts were actually loose.

Throwaway cutters is the term used for the small usually under 6mm cutters though they can be had upto 10mm dia with a Weldon (sidelock) shank. They are not worth industry sharpening so have become known as throw away I also use them a lot as they are quite economical and the 3-flute design is a good all rounder. I usually get Hertel brand from MSC when they have them on offer, though not listed this month.

They work well on aluminium but the aluminium specific cutters are better still.

I'll have a look at getting some of those cutters next time – and I'll check the bearings, although they don't feel loose at all.

[Ramon WilsonParticipant @ramonwilson3]

Posted by Dr_GMJN on 25/10/2020 16:47:54:

Cheers Ramon,

The spindle bearings are fine. The mill is new – or at least first got used this May after buying it last year. I can only think that the tramming process – using shim steel under the column bolts, doesn't give enough bearing area and is causing some kind of resonance. I'm using 6/8/10mm end mills or slot drills. It's mainly side milling that gives the issues. The end of the sample aluminium base section I posted yesterday for example is about a 20mm deep x 10mm wide section, and when facing the ends to neaten it up, the cutter squealed like a pig no matter the speed, depth of cut, climb, not climd or whatever. I was trying to face it using the full depth of a 10mm end mill. Maybe it's just me I dunno. Fed up with it TBH, I just try to avoid it now.

When you say "throw away cutters", what do you mean by that? If you mean cheap, then I had some of those, and folks on here told me to buy premium stuff because the cheap ones were probably contributing to the issue.

I added an x-asis power drive (just a dc motor and speed control through a dog clutch) that reduces handle spinning on longer parts (and often gives me improved surface finish on wide surfaces).

Anyway, I'm currently finalising the materials list, and converting the drawings to metric, then I need to convert the ML7 to wide bed format to get rid of some wear, and add some slide bearings. Then I'm good to get on with machining again.

I'll just crash on with grinding some of the HSS tooling I've got, but never use, and see what happens on some test material.

 

I replied to this earlier but for some reason it has not posted. I'm having a lot of problems today with the computer dropping in and out of internet connection.

No, I definitely didn't mean 'cheap' cutters (never a good idea) but Jason has explained what I mean perfectly. Any good brand of FC3 cutters will be ideal. There are cheaper versions on Ebay but despite their attractiveness the quality of life rarely holds up.

Any mill that is exhibiting the kind of issue that you describe is definitely suffering from a lack of rigidity – somewhere – it's finding it that can be a problem. As Jason suggests I would certainly begin at the spindle and check for any slackness in the bearings first, both vertically and radially,  then work out from there. Assuming the table axis's are firm and well supported squealing, chatter, juddering when cutting is usually a lack of firmness somewhere in the spindle set up or in it's guide in the head. Certainly worth spending some time on to improve it if possible – the machine should be able to be relied upon at the age it is.

A power drive is a very nice accessory to have – my Amadeal mill is still waiting for one, nearly six years after being told it would be a few months! The finer pitch leadscrew on that compared to my old Linley certainly makes for tired arms on lenghty parts!

Edited By Ramon Wilson on 25/10/2020 20:24:29

[Dr_GMJNParticipant @dr_gmjn]

I've started a WIP thread for this here in case anyone's interested:

https://www.model-engineer.co.uk/forums/postings.asp?th=168849

Thanks for all the advice here folks; any further P.R. questions, I'll ask on the new thread.

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