Lathes & M/C tools

[richard_t]

Thanks again for the replies, needless to say my research continues and I have some questions.

 

I have been looking a the various tools and cutters for a mini lathe in particular the parting tool.

There are many references to the use of the parting tool in particular the use of the tool cutting from the rear of the piece as well as on the front of the piece to be parted. What is the difference and what are the benefits with the two arrangements?

 

If you're looking at Mini-Lathe (C3 for example), you can mount the parting off tool at the front, and run the lathe backwards. This will be the equivlent to a rear mounted parting off tool. This is only possible as the chuck isn't just secured by a screw fitting (which would unscrew), but by 3 studs. More info in the Mini-Lathe book (Chapter 7), referenced in my previous post.

[alcazar]

Maybe. The collet chuck for the lathe looks like this: (was going to post a pic but the e-bay sale has ended. Anyway, it has no taper, but a flange with three bolt holes, it would seem to be turned out of a piece of solid bar.

[ozzyo]

If you're looking at Mini-Lathe (C3 for example), you can mount the parting off tool at the front, and run the lathe backwards. This will be the equivlent to a rear mounted parting off tool. This is only possible as the chuck isn't just secured by a screw fitting (which would unscrew), but by 3 studs. More info in the Mini-Lathe book (Chapter 7), referenced in my previous post.

 

 

Me thinks,

that you may have got some things a bit the wrong way round. If you have the parting off bit in the normal tool post run the lathe as normal.

 

If you have one to the rear you have two options,

 

1] mount the tool upside down, & run as you would for turning.

 

2] mount the tool upside and run the lathe in reverse.

 

OzzyO.

[bertiedog]

He is right about the upside down and reverse as the object is to throw the cutting force down on the saddle when the rearpost is used and the reversed front does the same in a more limited way. (It does not seem to logically, but the bed/slide acts as a fulcrum/lever).

 

I have used this on the small Ward turret lathes where the saddle was full of tools both front and rear all set on stops and motion regimes to do a sequence of pre-set cuts on complex items, and the parting worked better in reverse.

 

The Myford, despite its renown, has the design flaw of a "loose saddle", you cannot adjust it tight enough to part off, without locking all the gibs tight, but you can leave them unlocked if the rear post is used, or the front in reverse, to apply down force to the saddle, preventing lift and judder.

[bertiedog]

And by the way the Sieg is quite good at parting off, the troubles reported would apply to many smaller lathes, it's the method, not the lathe.

 

A saddle lock is vital for a decent parting off experience, and the Sieg does not have one at all, only the gib adjustment. A saddle lock can be added in an afternoon, there are kits or home brewed versions.

 

To part on any lathe the tips are:- ........ a firmly mounted tool, a locked saddle, and a slow speed, and the tool tip must be below the centre line by a few thou.

 

The appears to leave a pip, but one side of the tool tip face can be set to leave no pip, but the bulk of the face should be shy of the centre line. On, or above the centre line, causes or risks judder as the tip alternatively skates and then digs in.

 

For most cut off work the rake should be near zero, or slight for steel in small lathes. With normal rakes the tool digs and then relieves and again judder sets in.

 

For amateur home machinist the other golden rule is that the parting off is not the finishing cut, many pros take pride in production work to use it as the finishing cut, but do not aim for this at first, part off and then face the work with a round nose tool, much better finish, and no pip.

 

Also with smaller lathes, do not expect to part plain mild steel easily, it needs lubricant like Rocal, and some steel is really quite rough and tough. You would find silver steel or stainless actually easier.

 

With Aluminium, the parting should be easy at low speed, but aluminium swarth has a tendency to weld itself to the tip at higher speeds, so use paraffin to act as cutting oil.

 

Brass should part off dry, and cleanly, the speed can be a bit higher.

 

Stephen.

[ozzyo]

He is right about the upside down and reverse as the object is to throw the cutting force down on the saddle when the rearpost is used and the reversed front does the same in a more limited way. (It does not seem to logically, but the bed/slide acts as a fulcrum/lever).

 

I have used this on the small Ward turret lathes where the saddle was full of tools both front and rear all set on stops and motion regimes to do a sequence of pre-set cuts on complex items, and the parting worked better in reverse.

 

The Myford, despite its renown, has the design flaw of a "loose saddle", you cannot adjust it tight enough to part off, without locking all the gibs tight, but you can leave them unlocked if the rear post is used, or the front in reverse, to apply down force to the saddle, preventing lift and judder.

 

 

If you just say he is right, not much of an answer.

 

To use the parting off tool in the front tool-post run the lathe as normal. OK.

 

If the parting off tool is in the rear-tool post you have two options, up side down and run as normal, not the best option as the culling force is trying to lift the saddle off the bed.

 

If you mount the parting off tool the correct way up you have to remember to change the cutting direction. But this will normaly put the cutting force down on to the saddle and lathe bed.

 

The Myford should part off from the front tool post with no problems, if it is set up right. AFAIK.

 

It will all depend on the make of you lathe.

 

OzzyO.

[bertiedog]

 

I hope this is clearer, and explains why B and C are in fact the same, as it is just a mirror image and still results in a down force to act on the saddle, albeit with the pivot point moved...indeed A and D are mirror as well.

 

So front mounted in reverse will work the same as back the right way round.....to a degree, and less force than B.......phew!

 

Stephen.

[alcazar]

 

Stephen.

 

Unfortunately, that one looks A LOT like the one RDG tools withdrew from sale.

 

At least two others are still selling the same tool on e-bay, so I'm loathe to buy unless sure.......

[bertiedog]

Unfortunately, that one looks A LOT like the one RDG tools withdrew from sale.

 

At least two others are still selling the same tool on e-bay, so I'm loathe to buy unless sure.......

Well I have used this type and they work, but they may have had makers troubles, but there is the g/tee... or going for a more expensive Glanz insert type in 6 mm size..

There are also the 6mm full clamp, where the holding force is provided by the clamping screws, should work fine, there is nothing to go wrong !!!

 

Stephen

[bertiedog]

Just had a talk with one of the suppliers whilst ordering some bits, and there are two reasons the other brand had failures, one....

• The screw was done up far too tight, it needs to be secure but people were adding leverage to the bolt head, and two....

• They were over extending the whole tool, one of the keys to parting is the minimum amount possible and no more should be extended to do the work,.... grip at the back, with an extended front and great force is applied to an already over stressed clamp down bolt and it can shear the body blade groove where the blade sits or even strip the bolt.

These are FE made and usually OK. The full clamp type do no suffer in the same way, but again only use as much blade as strictly needed.

 

It was not so much the small size, but inexperienced use that brought problems to light.

 

Stephen.

[ozzyo]

 

I hope this is clearer, and explains why B and C are in fact the same, as it is just a mirror image and still results in a down force to act on the saddle, albeit with the pivot point moved...indeed A and D are mirror as well.

 

So front mounted in reverse will work the same as back the right way round.....to a degree, and less force than B.......phew!

 

Stephen.

 

 

All I was trying to say was that 'A' & 'D' transmit the cutting force down to the lathe bed. Whereas 'B' &'C' will try to lift the saddle off the lathe bed, now please tell me how that is not so.

 

OzzyO.

[PhilH]

The Myford, despite its renown, has the design flaw of a "loose saddle", you cannot adjust it tight enough to part off

 

I'll tell my mate that, who makes his living with Myford lathes - should make him smile. I'm sorry Stephen, that is just not a true statement.

[bertiedog]

B are C are the same in effect, the resultant opposition force is towards the saddle in both cases, the "correct" way to do it.

 

In normal front cutting by parting the force is the wrong way, but barely matters as the weight of the saddle resists it, dependant on lathe design, and the Myford/ Southbend/Colchester etc., saddle at the front is heavy.

 

In D the same applies, and the "wrong" upward force is applied to the back of the crosslide and is less desirable.

 

However all is academic, if the work demands multiple tools, as on a manual Brittain or Ward , where 4 to five tools may be mounted at the front, and another four at the back, just to get enough tools for a regime of cuts. You just have to place some to work in reverse.

 

It's a very much simpler world with an Emco or Sieg etc., or the tiny US Sherline, where front parting is the normal position.

 

As lathe size increases back parting is usual, especially for the Myford, which has the same style of saddle as the classic Southbend lathe, and suffers with front parting, due to judder, not all the time but it can happen with bigger diameter workpeices. I worked with Myford for 20 years, and my current Warco has the same saddle, but it is so heavy that it does not judder, (and locks as well.)

 

The Colchester Student, Boxford, and larger Colchester do not judder on parting, different type of lathe bed, and my small Toolroom Lorch simply does not judder, as the whole bed is flat and it grips with V beds facing front and rear, and has a clasp lock that clamps totally for parting off, virtually making the whole cross slide part of the bed.

 

Denham used this type of bed on many of their medium size lathes, as did Cardiff, and Brown and Sharp. You don't worry too much about judder on a Denham, the saddle weighs as much as a whole Myford!!

 

You may notice I have had about 48 years experience on lathes of all types, I had to learn on the job, you never told the foreman you had never seen a particular lathe before, you were expected to be able to use it.

 

Many a time I have been presented with an "unknown", and I know the manager is thinking....I bet this stumps him, but I have never been "had" except on a Holzpeffel fitted with a machine engine pattern generating head, which TD Walshaw, "Tubal Cain", of the Model Engineer magazine conservatively thought it took about 10 years to learn to use properly. I barely learnt how to do elliptical cutting let alone complex patterns to order!!!

 

This is all why I like the Sieg, especially in the form the Warco uses, with the new tailstock, it is essentially a small Southbend in miniature, and no worst for that.

 

Stephen.

[sagaguy]

I'll tell my mate that, who makes his living with Myford lathes - should make him smile. I'm sorry Stephen, that is just not a true statement.

 

 

 

Eh!!,I have no problem at all parting off steel with my Super 7,With a properly ground tool & set correctly,it works every time.

 

 

Ray.

[bertiedog]

Your jumping to the wrong conclusion if you are thinking I am complaining about Myford, the Myford 7 series is good, very good, but it does have a flaw that I and others have commented on,, shared by lots of other makes to the same design, the upward force on the back of the saddle is taken by a plain flat surface, not a self locking V surface.

 

If you get good parting on a Myford it is because you are working well within the limits of the machine and you are just very good at it. The Myford judder only occurs when the saddle is not locked, or the gib adjustments are poor, but well adjusted, and locked, a Myford will part 4 inch steel bar with ease.

 

Old hands like Terry Walshaw of "The Model Engineer" advised using the rear post to drive down the saddle to sit tight on both the front and the back of the bed slides equally, a movement so small you need a good dial gauge to read it. This is because he did parting without full locking, as he was using multiple tools and did not want to lock and unlock the saddle repeatedly.

 

I have never had a Myford I was using judder in any way, but in helping out setting up lathes for other model engineers, often came across the saddle too loose or not locked, and people would comment that they did not get on with parting off, but a few adjustments, and using the saddle lock, and all of them worked 100%.

 

I have re-built several Myfords, from the ground up, including hand scraping the bed flat and total strip, and know every detail on them, and would have one of the machines if Myford had been able to deliver one in under 15 months in 1987, as I needed a big lathe for work the next week I opted for the larger Myford 13 inch centre equivalent from Warco.

 

Often the problems with any lathe is the user not being completely used to using a lathe, and passing on tips like the details of parting off is not attacking a particular lathe, but providing the knowledge and tips to be able to understand why something is advised.

 

Now it could be an annoyance to any lathe owner that has a lathe with high quality roller bearings to hear that a well adjusted Myford beats it hollow on surface finish, because even the best taper races cause harmonic vibrations than result in patterns on the cut surface.

 

The reason I know about it was producing British Standard test peices, yes, the ones that test others!, and the surface had to be perfect, no marks, even at the reflection of laser light. It showed that you could tell from the reflection pattern whether a roller or ball races was used, and the beat frequency even told you the number of rollers fitted in the bearings.

 

But a Myford and a Schuablin, with plain bearings, produced little or no patterns, and the Schaublin none at all when really tightly adjusted. The Myford was the next best, so do not say I do not know what work a Myford will or won't do.

Stephen.

[bertiedog]

One other point I had in mind to mention on parting off and it involves insert tips as well, it that upside down tools clear the chips of swarf better than the right way up, .......it's gravity you know!!,... and also for parting off the geometry of the carbide insert tips breaks up the swarf finer than the conventional HSS blade grind, again combined with up side down there is liiitle chance of the swarf causing drag and inducing judder or jams.

George Thomas, who designed his famous rear tool post holder for the Myford,* said a top rake of 7 seven degrees was best for general work with steel, both front mounted or rear mounted. This ties in with Sanvik inserts.

 

The other vital point I did not mention is that the blade must be at right angles to the work, plus or minus nothing!!! Check both sides with a good miniature try square against the turned work, or a test bar in the chuck, a fraction of a degree either way, and friction builds up and the tool tip is deflected.

 

The carbide insert parting tools are kinder in this respect, they are are only a small side length, then a thinner holder, so out of right angles does not how too much, but it still counts on finish and safety, so still check with the square.

 

Stephen.

 

* George Thomas's books and ME articles cover the design of the Myford saddle and its limits etc., in great detail. He was a deeply respected author and expert tool designer. I use one of his toolposts in the Warco lathe, expanded to the bigger size from the Myford series 7 type.

[ozzyo]

B are C are the same in effect, the resultant opposition force is towards the saddle in both cases, the "correct" way to do it.

 

In normal front cutting by parting the force is the wrong way, but barely matters as the weight of the saddle resists it, dependant on lathe design, and the Myford/ Southbend/Colchester etc., saddle at the front is heavy.

 

In D the same applies, and the "wrong" upward force is applied to the back of the crosslide and is less desirable.

 

So Stephen,

 

are we now to assume that cutting with the lathe as in Dig. A is wrong, and that we should all start cutting with our tools mounted as in Dia.C.

 

Tool position as in Dia. A, will transmit the cutting forces down to the lathe bed.

 

Tool position as in Dia. B, will try to lift the rear of the saddle off the rear slide.

 

Tool position as in Dia. C, will try to lift the front of the saddle off the lathe bed.

 

Tool position as in Dia. D, will try to transmit the cutting force down to the lathe bed.

 

All this is assuming that the size of the work piece is less than the distance across the width of the lathe bed.

 

On your remarks about machining test pieces on the lathe, yes it may tell you how good that that lathe is running, but not necessarily how good the next lathe is running. With regards to taper roller bearings it is not good policy to only have one at the head end of the lathe but to have two, one towards the cutting force and one to take up the end slack (or it could be with roller bearings that will take end thrust). On the rear end of the headstock it will normaly be a roller bearing.

 

Just out of interest where did you work? As I used to work in the nuclear industry.

 

OzzyO.

[bertiedog]

NO, the correct/normal/every day/usual/ accepted way is the front and right way up, the others are alternatives and only shown to show what they do...it is horses for courses. If it is a Colchester 20 inch lathe it ain't going to notice anybody messing up parting off, but if you do it wrong on a Sherline it is going to protest in no uncertain terms!!!!!

 

The Myford is an exception in some ways, it is a very fine lathe, but parting off can be troublesome to people who only have half the story, it needs to be well adjusted to part off well.

 

This is very well documented, it has been addressed by Myfords with redesigns within the design of the lathes bed,...... the final word is parting off is OK on a good condition machine with a good operator, too often I see a badly adjusted Myford with a newcomer to lathes, and Yes, I have seen half a broken parting off tool buried in the ceiling!!! it juddered, dug in, and before he could operate the clutch the tool shattered, but it was that operator, and it might have happened on any small lathe.

 

I was trained in engineering with Post Office Telephones(BT), STC, and Cable and Wireless, and worked later in model engineering and model manufacture, and then in optical instrument making and making lenses and scientific instrument making....and I started on lathes with my father at the age of six, on a Drummond round bed I still have, and that's fifty four years ago.

 

Stephen.

 

Stephen.

[PhilH]

I think that anyone left reading this thread will be asleep now - it's a shame that it has become a snoozefest of pedantic, theoretical proclamation. Why don't we just get back to practical tips and advice remembering that a lot of us have had, in one way or another years of experience in owning and using a lathe and allow these people to have an opinion too.

 

the final word is parting off is OK on a good condition machine with a good operator

 

.. which applies to every lathe under the sun.

[sagaguy]

I think that anyone left reading this thread will be asleep now - it's a shame that it has become a snoozefest of pedantic, theoretical proclamation. Why don't we just get back to practical tips and advice remembering that a lot of us have had, in one way or another years of experience in owning and using a lathe and allow these people to have an opinion too.

 

 

 

.. which applies to every lathe under the sun.

[/quote

 

 

Hi Phil,I did try!!!

 

Ray.

[flubrush]

Maybe, too, we've been banging on about exercising extreme care in what should be bought. Sometimes it is worth just getting something and seeing how you get on with it. My first lathe was a rather elderly Myford ML2 which I got for £10 (when my take home salary was £65 per month). It wasn't perfect and I learned not to try to part off in it but use a saw and face off afterwards. But I learned a lot about what the lathe could do, and what I wanted it to do for me.

 

The next lathe was a Super Adept which was rigged up for treadle operation on an old Singer sewing machine base. On that lathe I learned how to use a four jaw independent since that was the only chuck available for the lathe. I think the Adept also cost about £10.

 

Then Myford brought out the ML10 and I went to town and bought one new - almost bankrupting myself in the process - but the ML10 did all that I wanted from a lathe and with a vertical slide, gave me a lot of milling facilities as well. The decision to get it was based on my experience with the earlier lathes and what they could or couldn't do for me. I've still got the ML10 nearly 40 years on and it still does everything I want to do.

 

Also I had always wanted a milling machine and I finally got one about 10 years ago - a Centec 2A which is almost as old as myself. This machine then allowed me to do a lot of milling that is not easy on a lathe. The X and Y movements on a lathe are relatively small which limit the size of work you can do, and the average model makers lathe is not as strongly constructed as a milling machine, which limits the type of work you can achieve.

 

But another big help was knowing other engineers or model engineers. You could talk to them and see them doing jobs on their machinery and see what they had in their workshop. If you are new to lathes, it's worth looking out for a local model engineering club and joining it before you make any purchases so that you can benefit from other people's experience and you might also find out about suitable second hand lathes in the area which might be available.

 

Jim.

[alcazar]

Thanks for that Bertie-dog, I'll look into buying one.

[bertiedog]

Working with any small lathe and wheels in smaller scales up to about gauge one.

 

The methods are well known, but act as introduction to newcomers as well to lathe uses.

 

One of the main jobs that a small lathe is used for is producing wheels or modifying the existing wheel, taking a commercial product that can be made to conform to a tighter standard etc., or replacement of tyres on mazak cast wheels with a more suitable tyre.

 

You can also mass produce wagon and coach wheels from scratch, maybe for P4 or less used standards like S scale.

 

Any of the small lathes from the Sherline upwards can handle these jobs, it needs a bit of planning on holding the wheels for machining, mostly out of the chuck on a mandrel or spur point.

 

The most common request is reduction of the flange, taking a Lima wheel as an example, the flange is about twice as high as it could be reduced to. Most of the older Lima wheels were brass, chrome plated, but it will work with the mazak chromed as well.

 

The wheel, removed from its axle is not able to be simply gripped and the flange removed, so the first job is to chuck a bar of steel, say 3/8th inch(8/9mm metric in the three jaw, and turn a matching end on it to fit the Lima axle size,(or other). As the mandrel will be used many times it is worth reverse chucking first and putting a flange that will consistently rest against the chuck every time the mandrill is used.

 

The stub for the axle should stick through about half way, and have the end drilled with a centre drill to allow space for the point of the ball raced centre to fit without touching the stub when the wheel is fitted.

 

The mandrel should be marked to match jaw number one to allow return to and accurate position for each use, and the concentricity should be checked before use. Most three jaws are accurate enough, but if you want on larger wheels the mandrill could be set in a four jaw chuck for complete accuracy.

 

The mandrel is readied and the wheel slipped on to it, now comes the hard part, getting it to be turned by the lathe, and the easiest way is a live centre fitted in the tailstock, and to simply press the wheel onto the mandrel back, with sufficient pressure to hold. The centre revolves with the work, and the wheel is very accurately held. All small lathes come with, have available, or it's an accessory from any independent supplier, a ball raced live centre, (or you can make your own in the lathe should you wish.)

 

 

The flange can then be reduced and the shape of the tip filed or turned and finished with abrasive papers.

When abrasives are used , cover the slideways with paper, or cloth, and remove any dust made. Only use a file if you are experienced in such work, it is classed as somewhat dangerous, but is an accepted Jewellers and clockmaker's method.

 

 

The whole wheel can have the tyre removed till it is flangeless, or reduced further to take a new tyre, on for example a mazak chrome finished wheel, which lots of modern ones are.

 

A non insulated wheel is easy it presses against the mandrill, but an insulted one should have a washer added at the back to allow the pressure to bear on the metal parts.

 

Some Bachmann wheels have only a cast back, and some have raised surfaces and pips, so prior to re turning they would go in the three jaw, or a collet to have the back trued up first.

 

All of this covers metal centred wheels, including Romfords, which can be turned on one of their own axles if needs be.

 

With plastic wheels and scale wheels being returned, like Gibson, then a large mandrel face is made to match the diameter of the wheel so that the force is taken by the steel tyre, and the live centre bears on a washer made with a rim to press on the tyre, this removes all risk to the plastic, which on a spoked wheel cannot take the forces of turning.

 

 

All so far is accurate flange reduction or removal, the new tyre would have to be turned and a profiled tyre shape turned to continue the process. None of the above should be beyond any small lathe, or a newcomer to turning.

 

You can use such mandrels to hold blank wheels of your own for mass production, but usually a form tool and parting off a finished wheel is done from stock bar material, to be described later.

 

Next part, making a profile tool or using a commercial profile for re-turning or tyre replacement.

[gordon s]

Stephen, I'm really interested in how to true up wheels such as Romfords/Markits on the axles and suspect some of the pics in your last posting might help me understand how it's done. Only problem is that I can't see any pics. Have you left them out or have the picture files not loaded?

[sagaguy]

Hi Stephen,

 

Ermm,I think a mandrill is an Ape with a very colourful backside,I think it`s a mandrel

 

Ray.