Indexable Lathe tooling

Hi all,

Just a couple of questions. Having only turned my, new to me lathe, on for all of 5 mins and having finally worked out what the knobs and levers do I started to look at lathe tooling feeling very happy!. That was until I got completely lost with tooling holder types and Insert variants. I have a Dickson QCTP fitted to the lathe nd can accommodate 20mm tooling.

So I just wondered if a few of you helpful chaps might be able to point me in the correct direction. I have decided to plump for indexable rabid Tooling and holders and have come across the Cutwell site on the internet which hols a host of variants and information.

I have researched and now am starting to understand the ISO labelling and part numbers ref holders and Inserts.

What I need help with is which variants should I purchase, ie 95 degree, 75 degree R hand Left Hand..or do I just purchase a starter set fro Chronos or the like. I think I understand parting tools to get me going.

In particular could anybody assist me with which angle should I leave the Compound table/slide when using the holders and inserts. I presume at 90 Degrees to the saddle is OK??? Do really need to move to 30 degrees for thread cutting with thread specific inserts?

Finally, do I understand that the cutter inserts are specific to the threads that are being cut, and I will need a different insert for each pitch...seems a lot of inserts will be needed?

I have been googling and have ordered a few books for more Lathe tooling/ operating reading when they arrive, but had just hoped that someone might be able to assist me to get me going with ordering some tooling.

Many thanks in anticipation

Gary

No, you can also get what Mercans call "agnostic" inserts - we call them "partial profile". Fine for what we need and doesn't require such a large number of insert sizes.

Good guide here if you have time.....

Murray

Hi Murray,

Many thanks for the Link, looks to be some great info here. I will study with great interest. Again. Thank you.

Gary

The thread cutting question has a specific answer, so here goes: There are two ways in which this operation is usually carried out. In both the tool is held symmetrically to the work, with the same angle both sides (ie 30 degrees for Unified and Metric, 27.5 for Whitworth and its relatives, etc). The thread is cut in two or three passes.

The difference is that in one method the tool feed (ie the inwards adjustment for the next cut) is at right angles to the workpiece, using the lower of the two handwheels on the saddle assembly. This means that both sides of the tool cut (almost exactly) the same thickness of metal with each successive cut. In the other method, the adjustment is done with the top slide, set at the angle of half the thread angle (30, 27.5 etc) and the adjustment moves the tool along one face of the new thread, with all the material removed from the other face.

The second method is described as the better way by many experts.

And no you do not need a different insert for each pitch, as long as you are not too fussy about the tip radius (or tip flat). There are those who say that for ordinary low stress stuff, you don't even need separate 30, and 27.5, tools. After all, I bet your local nuts and bolts supplier will sell you UNC studding when you ask for Whitworth, as the pitch is the same and there is enough clearance to permit them to be interchanged. (Not such a clever idea for bolts and nuts, though, as the head sizes and spanner fitment is going to be wrong).

Regarding the broader Q: What to buy, I suggest that you start with a cheap and cheerful set, and a box of free-cutting mild steel offcuts, and play. This will give you the feel of the work. Then when you actually need to cut real parts at exact angles and positions, you might need to look more closely at the better end of the market. It is cheaper that way.

Regards, Tim

As another 'absolute beginner', (albeit for the last 20 + years or so!!), I think that I have 3 or 4 insert tool holders and inserts and I have NEVER had cause to use them. All of my (limited) turning has been done with either pre-ground or hand ground HSS tools. A recent purchase of the Eccentric 'Diamond' tool has been the (worthwhile) exception. Are insert tools necessarily a worthwhile investment for beginners? Personally, I rate them much the same as QCTPs but that may well be why I am still a beginner!!

rgds

Bill

Tim,

Many thanks for taking the time to post a detailed succinct reply. Much appreciated.

Gary

Hi Gary,

ISO tooling covers a massive range of variants which are used (mainly) by industry to maximise productivity. It's worth their while to put a lot of effort into selecting the optimum tool, speed and lubricant etc, hence the tremendous choice. You'll be pleased to hear that you can get by with relatively few of the alternatives.

I found a starter set is a good place for a beginner to get going. The main disadvantage of a set is accidently spending money on a tool you don't need, shock horror: some dislike wasting a few quid intensely! Another problem is that a particular set might not include a tool you do need. For example, the Chronos set has two tools you may not use much, and no threading tool. Nonetheless I recommend buying something like that and trying the tools out rather than agonising over a catalogue. What seems strange and mysterious on paper makes more sense after you've tried it, and later purchases will be much better informed. Worth wasting a few quid on learning I feel.

Recently I expanded my range of inserts with a a very sharp rhombic tool and a circular. I use the sharp one quite often, and a circular insert is dead handy once in a blue moon. Which inserts you prefer and use most depends on the type of work you do.

I usually leave my tool post at 90 degrees. The main exception is thread-cutting, but even then I don't bother when using proper threading inserts. Again, try it and see. Sometimes angling the tool helps.

Dave

Welcome Gary, as for the tool size best check that the shank top surface can be adjusted to lathe centre height with the available adjuster in the toolholder, I say top surface because that is normally the top height of any insert fitted to toolholders. You may find you have to fit smaller tooling.

What you end up buying will depend on the type and size of work you intend to do but if the toolholder will take 20mm tooling it suggests a fair size lathe, more info may help such as make and model.

Check on the advertisers sites for more info on toolholders shape and insert sizes/types but you will certainly need a Right Hand cutting tool possibly a LH and also a parting tool.
You mention threading so you will find upteen holders and inserts for various imperial threads although many can be cut with a single 55 deg tool,, most metric can be cut with a single 60 deg tool but inserts are available to provide correct radius to the crests but these are size dedicated inserts and named as Part or Full form inserts.

Buying a full set of different tools may not be the best way to go.

Emgee

I’ll take you on, for a bet, on 1/2” size!

If you look in the "thread designations" pages starting at pp5 in the linked document, you can see how tolerancing works for the various thread systems. Few MEs come across thread tolerancing, hence the experiences with rattle fits and stripping threads that arise from crappy rolled studding etc. However, for critical stuff like automotive and aerospace it matters, so fasteners are specified with tolerancing like a G (nut) and g (stud).

Murray

Try this lot http://www.jbcuttingtools.com/epages/es461493.sf/en_GB/?ObjectPath=/Shops/es461493/Categories/%22Milling%20inserts%22

They go to most of the ME shows

I can never be bothered with the faff of angling the topslide, plus it means you have to do mental juggling to keep track of the cut depth.

Moving the top slide across 1 unit for every 2 units of infeed will move the tool at 26.6 degrees, which is close enough to give a just shaving cut at the back with metric or imperial threads. (Not my idea, I got it from a Tubal Cain article).

Neil