First cuts with the lathe

[duncan webster 1Participant @duncanwebster1]

Diamond file is good for rounding the vertical edge

[duncan webster 1Participant @duncanwebster1]

Diamond file is good for rounding thd vertical edge. 1/4″ sq tools are a lot easier to grind and plenty stiff enough for small cuts whilst learning

[Howard Lewis]

On Howard Lewis Said:

Cutter? Surely lathes have tools and toolbits and milling machines have cutters? The difference being cutters rotate while tools and toolbits remain stationary? (Not sure where that leaves shapers though?)

While most of us are trying help a newbie, can the above please be moved to pedants corner.

Pedagogy not pedantry! Teaching a “newbie” incorrect terminology is not helpful in the long run.

[PeteParticipant @pete41194]

While there different lathe brands than yours is Chris, a couple of PDF links for good basic turning information including tool sharpening.

https://gadgetbuilder.com/How-to-run-a-lathe.pdf

http://www.opensourcemachinetools.org/archive-manuals/Hercus_TextBook_of_Turning.pdf

If you have lots of books and don’t yet have this one, put it on your mandatory to buy list. https://www.teepublishing.co.uk/books/in-your-workshop/model-engineers-workshop-manual/ Yes I’d term it as a medium level to sometimes lower advanced level book. But it’s one you’ll refer to often. And even at your current level, a great deal in it that can be used immediately. The authors thoughts about proper slide adjustments, HSS tools, and even the pros and cons of QCTP’s just for starters. I was going back through my own copy this morning in fact.

As someone has already said in this thread, problem solving is a big part of the hobby. Sometimes highly satisfying, and sometimes extremely frustrating until you finally get a reason and solution figured out. Learn to view any problem using pure logic and think everything through. And not what you think might or should be true. In the beginning it usually isn’t. 😀

[Dave SParticipant @daves59043]

Sherline has a good how to grind tools guide:

https://www.sherline.com/wp-content/uploads/2015/01/grinding.pdf

 

Dave

[Nigel Graham 2Participant @nigelgraham2]

Diamond file –

Not thought of that – Thanks for the hint, Duncan!

[jamesp1]

On jamesp1 Said:

Cutter? Surely lathes have tools and toolbits and milling machines have cutters? The difference being cutters rotate while tools and toolbits remain stationary? (Not sure where that leaves shapers though?)

My old-British books call lathe tools “knives”…

History left metal-working terminology in a mess, especially in pioneering Britain, where trades, regions and companies all had their own variations.  Whatever jargon individuals were taught in the past can’t be universally correct because there is no common standard.

I think beginners just need to be aware it’s necessary to read between the lines sometimes.  We shouldn’t make it difficult on the forum:  I suggest ‘cutter’ is easier to understand than ‘tool’ because ‘tool’ is ambiguous, whilst “knife” is positively misleading.

Dave

 

[noel shelleyParticipant @noelshelley55608]

DID THE PERSON UNDERSTAND WHAT WAS MEANT BY THE TERM ? Does a lathe tool not cut ? It should ! Noel.

[PeteParticipant @pete41194]

A lot of the books covering lathe tool sharpening are a bit lacking in details Chris. Too many of them seem to cover the powered grinder sharpening well enough, but neglect or may not even mention the needed honing after. Yes a ground tool right off the grinder will cut, but not nearly as well or with the same surface finish quality as one that’s been properly honed. Paraphrasing George Thomas, “a rough ground tool can not produce a fine finish” or words to that effect. And a well honed tool with a slight tip radius will also last much longer. Many times you don’t even need to regrind the tool, just re-hone it and it’s as good as new.

However the term honing is a bit subjective as far as how sharp the tools cutting edges should be. Pulling the tools honed edge with very light pressure down your thumbnail, it should be sharp enough to start to raise a chip is one way. A proper and very good quality stone with a recognizable brand name such as a Norton isn’t cheap. And cheap stones aren’t worth buying. And after enough use, they need to be re-flattened. Instead I chose to buy from a woodworking tool dealer a diamond coated plate. They stay flat, last almost forever, hone quicker and in some cases, are cheaper than a good stone. I also use that plate with a few drops of light weight oil. Something easy to get like 3 n 1 if it’s available in the UK, or sewing machine oil works fine.

[Martin KyteParticipant @martinkyte99762]

I use window cleaning fluid with my diamond hone plates. It’s convenient in the spray bottle and less messy than oil. Wipe clean afterwards with kitchen roll.

[PeteParticipant @pete41194]

Thanks Martin, I’ll have to give that a try.

[jamesp1]

On jamesp1 Said:

On Howard Lewis Said:

Cutter? Surely lathes have tools and toolbits and milling machines have cutters? The difference being cutters rotate while tools and toolbits remain stationary? (Not sure where that leaves shapers though?)

While most of us are trying help a newbie, can the above please be moved to pedants corner.

Pedagogy not pedantry! Teaching a “newbie” incorrect terminology is not helpful in the long run.

Perhaps you may have overlooked the start of that particular ‘conversation’ at 06:56 ?

[SillyOldDufferModerator @sillyoldduffer]

The difficulty of sharpening HSS can be avoided by using carbide inserts.  Grinding HSS is an acquired skill, not everyone is good at it, and for many purposes carbide is better, or at least more convenient.  Carbide inserts are precision made and shaped with edges and relief needed to cut optimally.   Inserts fit accurately into the holder so there is no need to reset tool-height when one breaks; just swap in a new insert, or rotate a fresh corner into position.

 

A beginner advantage is that inserts eliminate grinding mistakes!  Starting out, self-teaching oneself to cut metal for the first time with a new lathe, it may pay to avoid having to buy a grinder and learn how to use it.  Save grinding HSS for later.

Inserts aren’t entirely plane sailing because shapes optimised for industry may not perform well on slow, underpowered and not very rigid hobby machines.   Inserts also come in bewildering variety*.  Nonetheless, at least 80% of my hobby turning is done with inserts because they save a great deal of time compared with HSS.  HSS isn’t redundant: once in a blue moon, carbide struggles to produce a good finish, so I switch to HSS.  Another reason  for HSS is it can be ground into non-standard form shapes for special cutting.  Form cutting is rarely needed in my workshop, but might be common in yours.

*Hints: the range of inserts sold by ArcEuro are a good match to hobby requirements. Also, the sharp inserts normally used by industry on non-ferrous metals perform well in a hobby machine cutting steel.

Dave

 

 

 

[Howard LewisParticipant @howardlewis46836]

Chris 12

You have  taken the first steps to climb the learning curve (It goes on for ever!)

You are doing the right thing by practicing on relatively cheap material, rather than something expensive, like a part from a kit.

As you gain confidence and experience, you could continue to learn by making simple tools that will not only give experience, and confidence, but can be used in the future.

I would suggest, as a start, making a Centre Height Gauge. Once made, it will help setting up tools in the lathe. An off centre tool does not cut properly, and leaves a pip on the middle when facing the end of a bar, so it is useful for that reason.

When you find a need to cut threads, start by using Taps and Dies.  Zeus charts, and charts provided by folk such as Tracy Tools, will show the sizes for various threads (Use your books to learn the difference between different thread types, their forms and uses. If you have not got it, Tubal Cain’s “Model Engineer’s Handbook” is a good reference book to have)

Then you can start to make a Sliding Die Holder for the Tailstock You can buy the sets of Die holders, and Arbor to make your own body. Have a look at supplier websites, such as Arc Euro Trade, Warco or RDG

No one seems to sell anything for a Sliding Tap Holder.A pity, since the load need to drag the tailstock  along the lathe bed, can strip the newly cut thread. (ME 40 threads are particularly fine, and therefore shallow, so can easily strip).

A small drill chuck attached to a body which slides on the arbor, will accommodate a variety of Tap sizes.  There are other ways of holding Taps, but making the holders involve techniques that are not suitable for a newbie.

Don’t forget to reverse the Tap regularly, to break and clear the swarf.  They are less likely to break and scrap the job, that way!

For thread cutting, you will need a lubricant, such as Trefolex or Rocol RTD.

Until you are more experienced, do not worry about screwcutting, or you will become embroiled in working out gear trains, some of which can be complicated,, and the techniques for taking multiple cuts without losing your place, and ruining what you have already done.

When you have mastered the ability to provide a steady, consistent feed, by hand than you can think about power feeds.

Again, this will mean you learning how to set up a gear train to give the right ratio between chuck and Leadscrew.  All part of the learning to walk before trying to run.

P M me if you want more details about Centre Height Gauges, or Sliding Die or Tap holders.

HTH

Howard

[PeteParticipant @pete41194]

There’s a lot to assimilate when first starting this Chris. And this isn’t going to reduce that.

As far as tool grinding, it’s really not that hard. All it takes is a bit of studying and understanding about what your trying to produce, some practice, then the rest is mostly technique for what your learning that does or doesn’t work as well. Cutting out a few sheet metal or even wooden gauges for your most used angles to lay on the grinders rest and position the tool that your grinding against are a big help to do it as cheaply as possible. Better or more sophisticated grinding rests can be bought or built later. But those are the basics, and once learned you have them for life. If the grinding wheel type used is correct, the ground clearance and rake angles on the tool are close enough to being correct, it’s properly honed as the last step, that’s it. Why would that be so hard to do? I taught myself how with a few books as reference for those recommended angles and some practice. And zero additional help from the internet since it wasn’t even invented yet. Anyone competent enough to produce even semi functional parts on any lathe is certainly capable of learning how to grind lathe tools.

But I don’t recall anyone mentioning this so far. Most or possibly all of the cheaper bench grinders come with about the poorest grinding wheel hardness, grit size and structure possible for any tool grinding. There used as a sales tactic, and how little the grinder manufacturers can pay to include them. And not because there the most suitable for the task. Yes if there not already glazed from prior use they will grind, poorly and slowly, and due to that produce a lot more heat. So if you don’t already have decent grinding wheels. Visiting a woodworking tool store and asking for there recommendations for the proper wheels they have available for grinding high speed steels would probably be a good idea. At least if the sales staff do know what really does work the best. Today there’s probably better than the aluminum oxide wheels I started with and still use.

Few Model Engineers would ever be as fanatical about HSS tool grinding and sharpening as many woodworkers are, so what there using is no different than what we need. Added to that, I’d highly recommend a diamond dresser. Even good grinding wheels need dressing once in awhile just to keep them doing what you bought them for. A properly dressed wheel is much easier and faster to produce a properly ground tool. Braised carbide tools can be rough ground using a green colored silicon carbide grinding wheel. However there lots of evidence that breathing any carbide dust that’s created can be extremely unhealthy for it’s long term side effects.

For now, practice getting the better surface finish. Once you can produce that, then it starts getting a bit more interesting and complex. Cutting that same surface finish, but then to the correct size you need is a bit tougher. And this is the important part most beginners take too long to appreciate or understand on there own because I sure did. Yes you have dials on your lathe and sometimes there even called micrometer dials. But for very logical reasons, those dials or even the very best DRO in the world mounted onto your lathe will not allow anything close to a micrometer level of cutting accuracy for your turned dimensions. They will get you close, but there still not accurate enough due to the lathe itself.

It’s not exactly intuitive in the beginning, but between a micron level and what is easily seen by eye, all machine tools large or small are still affected by simple physics. Your lathes components under cutting loads are all deflecting and being forced back and away from that load to the limits of any clearance, machine rigidity and lathe part cross section. Those are usually small enough they can’t usually be detected by eye, but there still present. The deeper the cut and or quicker the feed rate, the higher the loads are, and the larger those deflections and movements will be. The lighter the cut / feed rate, the less they will be. With the ability of accurate enough measurements, even the lathe chuck itself is distorting a bit as the jaws are tightened. Your or any lathes components are far less rigid than we normally think they are. And what you dial in for a depth of cut is NOT what your lathe will cut.

So for producing an accurately sized part to a target dimension. We have to come up with a method to work around or compensate for since those effects can’t be eliminated. Lets say you have a short bar of steel 1″ diameter and rigidly held in the lathe chuck. And it needs a reduced size dimension on the end of it measuring 1/2″, but the length of that turned step is outside this explanation. All were concentrating on is hitting that 1/2″ dimension. I’d rough turn it over size, and then accurately measure it. For round numbers, lets say it now measures .530″. So a further .030″ needs to be removed. Preferably your feed rate is already producing a decent surface finish, so we’ll leave that as it is. But we now have a much smaller but known amount to remove. On a smaller and lighter lathe, I’d then make two cutting passes taking .010″ for each cut. I’d then accurately measure the diameter again. Since both of those two cuts were using the same feed rate and cutting depth, the cutting forces for each have been duplicated as closely as possible for each one. I’d still expect each of those cuts to likely have some small amount of lathe and cutting tool deflection. So lets say on your lathe that dimension now measures .512″ That means each of those cuts was really only taking .009″ instead of the .010″ the cross slide was moved in for each cut. Depending on just how critical the size is or exact that .500″ needed to be? You still have a couple of choices. You could dial in a guesstimate of probably .013″ and fully expect to be very close to dimension, and almost certainly within + – .001″. If much more exact was required? You might further split the .013″ that’s needed to be removed in half. Take one cut of say .007″ and then remeasure. Let’s say it now measures .5063″ I’d then probably just dial in that .006″ plus a fraction of a thou if I could do it, and make my last cut. If it then measured a few .0001″ oversize and that was actually important enough? A bit of polishing with very fine emery paper and a few seconds would get it extremely close. Those lathe dials and even the feed screws are only so accurate, for the majority of work there close enough. But measuring the actual cross or carriage movements can also be done using dial indicators if desired. A secondary measurement method not dependent on the lathe parts themselves removes any errors that might be caused by feed screw or feed nut back lash. Or if the slides are poorly adjusted and too tight? That causes what’s known as stick / slip. The feed screw is being turned in, but the slides dovetail friction is high enough that slide isn’t actually capable of moving until that feed screw pressure gets high enough to force the slide to overcome it, and it then jerks ahead a less than predictable amount.

In fact I always use an indicator for longitudinal carriage movements. And for logical reasons, I don’t and never use any of my lathes top slides for parallel turning. Others will have different opinions about that though. In case it’s not obvious yet, internal boring has the exact same issues. Except it’s even harder for most of us to measure any holes with a high degree of accuracy. Most of Model Engineering doesn’t require extreme accuracy, but understanding what is or may not be possible is still worthwhile.

Every lathe and the larger they get is different. The more experience you gain with yours, the faster and easier it will be to get predictable results. All this might sound quite complex, it isn’t and takes just a fraction of the time to do than explain. It will soon become an easy enough method. But take your practicing in steps, get the surface finishes better, then start practicing and cutting to an actual dimension as the next step. Once you can start to do that reliably, your then well on your way for any real parts.

How to get started and machine with a lathe is one thing. None of us have even mentioned some of this yet, but its not too early to do so. Looking after your investment over the long term is just as important. I’d suggest that keeping any way surfaces as clean and well oiled as possible isn’t optional. Turning the outer skin off a cast iron casting or even hot rolled steel with mill scale on it is commonly mentioned, and the warnings about covering any exposed ways until that’s removed are 100% true. It seems to be less well known, and with the amount of scrap steel most of us pick up and hoard. Turning any metal with rust on it can be just as bad for your lathe. I brush or wire wheel as much off as I can outside first, then wipe on any oil at all that’s available on the metals exterior. A rag or even paper towels on the bed ways helps protect them until the shafts OD machining has removed any rust that’s left, and the oil keeps any air borne dust to a minimum. A bit more costly, but I think aluminum foil used for cooking works even better on the ways.

And that same way protection is absolutely required anytime your using any abrasives around a lathe or any other machine tool. Since the carriage is usually moving towards the head stock, you do have to be a bit observant and not let anything snatch that way covering and dump everything right back onto the ways you were trying to protect. Fwiw, my own shop is pretty tiny, for that reason I don’t even do any dry tool grinding inside it.

Any taper tooling used in either the head or tail stock Morse Tapers need to be absolutely undamaged. And both the male and female tapers need to be maintained and kept spotlessly clean before that tool shank is inserted. Any tool shanks Morse Taper you wouldn’t consider as clean enough to stir a pot of soup with isn’t something to be used in your lathe until it is. Damaged female Morse Tapers or left to rust are extremely expensive and difficult to properly repair. Not allowing that to happen costs very little other than a bit of time and attention to detail. I think it was George Thomas who used the phrase that “it’s just as easy to develop good habits as bad”.

Use a clean wooden board or piece of plywood under your lathe chucks and covering maybe 6″-8″ of your lathe bed every single time when removing or replacing any chuck. It’s not if your going to drop that chuck and do permanent damage to your way surfaces, only how long until you do that’s the only unknown. I had to learn that the hard way, so save yourself the trauma.

It’s inevitable that you WILL crash your lathe at some point. What that means is running the carriage or other lathe part into the rotating chuck, and usually done under power feed. Your lathe almost for sure has a shear pin on the lead screw that hopefully prevents any real and major damage. But there will be at least some cosmetic damage at the minimum, or up to broken parts. A magnetic base and dial indicator zeroed while first positioning the lathe carriage within where the maximum length of machined surface you need can almost eliminate that. If nothing touches in that position while your hand rotating the chuck a couple of times, your safe as long as you don’t ever go past that indicators zero point. Milling a good lathe bed mounted adjustable position carriage stop once you have enough practice to do so is one of the first things I’d make.

Crashing your lathe at any time should be a major learning experience about whatever you were doing you shouldn’t ever try repeating the same again. I have a very cheap drill press vise I partially drilled into its bed maybe 25 years ago, I don’t even use it anymore. But it still reminds me to think more and make less mistakes. And so far I haven’t repeated at least that one since. Once is a mistake that anyone can make, twice is a learning experience, more than that and were not learning what we should have from the previous two.

 

[JasonBModerator @jasonb]

If you have a linisher or belt sander for your woodworking then that can also be used to shape your cutting tools. They usually have a decent size flat rest which is easily angled for clearances plus the cutting surface stays flat so your ground surface will also be flat not concave or convex which a worn wheel can cause.

[Howard LewisParticipant @howardlewis46836]

Remember that on most lathes, if you dial in 0.005″, and take a cut, the diameter should reduce by 0.010″  This is because, the tool having removed 0.005″ from the metal on your side, it will remove 0.005″ from the other side when it comes round to you!

(A few do have dials which show the effect on diameter, but you are unlikely to come across one)

Sometimes, having set a 0.005″ cut, when you measure, you will find that the diameter has only reduced by 0.009″. Don’t touch anything, just take another cut (Known as a “spring cut). The tool will be seen to be taking a very fine cut, and when you measure, the work may even be a tiny bit undersize!

With boring bars, being relatively flexible, sometimes you can take upto six spring cuts before the tool stops removing metal!

A formal turning apprenticeship used to take four years, so you won’t learn everything in a month!

We never stop learning

Don’t get fixated on tenths of a thou, (or microns). For the machines, and measuring equipment that we have, and the conditions under which we work, 0.0005” is about as close as we can normally get, on a good day.

To work to tighter dimensions will demand better, and much more expensive machines, and strictly controlled conditions.

For measuring, the temperature needs to be controlled (Some micrometers have plastic pads on the frame, so that the heat of your hand does not heat up the frame, causing it to expand, and measure less inaccurately)

A Standards Room will be closely temperature controlled, usually to 20C, and nothing will be measured  until it has been there for at least 24 hours, to soak to the set temperature.

A Calibration Room, where measuring equipment is checked for accuracy, will also be humidity controlled. (When checking Gauge Blocks, or Slip Gauges, they will be measuring to millionths of an inch. Slips are so accurate that they can be wrung together, and will not separate when picked up)

So keep a sense of proportion, and remember that we are working with hobby machines that have been produced, down to a price, rather than a high precision machine which has been made to a far higher level of quality.

Howard

[JasonBModerator @jasonb]

Quite a few of the far eastern machines have cros sslide handwheels that read in diameter, mine does so you may come across them.

[Howard LewisParticipant @howardlewis46836]

You would improve with some face to face tuition (And demonstration / practice)

Initially, over a year, I was taught the rudiments of machining, by very experienced instructors, and then was able to see machining taking place within the factory (And actually do a little more during a 3 month spell in the Tool Room) Sixty years on, having owned and operated lathes, as a hobby, for forty years, as well as seeing machining in various industries, there are STILL things to learn.

Many of the participants on this Forum are very highly skilled (Much more than me), so note what they say.

Where are you located?

It may be that there is someone near to you, who could visit you, or you could visit them, to learn more quickly, by having what is happening explained, as it happens.

Howard

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