Carbide Insert Holder Types?

[Th232]

Question that I'm almost completely in the dark about. I've just gotten a small lathe (here), I'm working down my list of tooling to get, and I'm down to holders for carbide inserts. I think I've wrapped my head around insert nomenclature, but now I'm wondering, what types of inserts would you guys recommend? Still trying to understand what inserts are good for what and under what circumstances.

Work is mostly going to be Al, but maybe some SS or Ti in there somewhere. Just going to go for the basics at the moment, turning, boring and threading tools. Threading will be metric, so I presume it's a T???-??? insert, but other than that I'm completely lost here.

Any help would be greatly appreciated!

 

[Anglepoise]

Get your hands on a 'Free' book called 'Metal cutting Technical Guide'
put out by Sandvik. I am sure Sandvik has representation in Sydney.

This book is mostly colored illustrations and there is no better for explaining the reasons for so many insert shapes, grades and coatings.

 

[precisionworks]

Positive inserts (xPxx) require the least hp, cut more freely, and do a nice job on a smaller machine.

Negative inserts (xNxx) give more cutting edges & the edges are stronger.

Look on eBay under "carbide insert" to find the most popular ones. If you go with a common insert expect to pay $3-$5 USD. If you go with a less common shape & size, it's easy to spend $10-$15 USD per insert.

 

[Tom Anderson]

It really depends on the geometry you're creating and the materials you wish to machine. There are many, many types of indexable tools for lathes.

I would pursue the type of holder/inserts you'll need for the toughest material you're going to use. (In your case, that would be titanium.)

Other rules of thumb include:

Keeping the support for the cutting edge as rigid as possible.

Avoiding interrupted cuts with carbide tools.

Experimenting with speeds/feeds so to realize the optimum settings for your particular lathe. We all like to be cautious with our expensive cutters, but if you go too slow on some materials they will work harden and make cutting more difficult.

Learning how to set rake angles and determining the optimum height off center is also very important.

There are many reference books on the subject, the most famous being "Machinery's Handbook" - but you can also find a lot of free resources on line. Every manufacturer of indexable tools also offers a variety of on line and printed reference materials.

Even so, you'll probably end up experimenting a bit on your own to find what works best in your specific applications.

 

[Th232]

Great info guys, thanks!:twothumbs

A few more questions. I've seen various inserts with 3 or 4 letters (e.g. TPG and CNMG), in the 3 letter inserts is it always the geometry that's missing, or does it vary? Truth be told, I thought it was tolerance until I saw a stack of TPG inserts without holes in the middle.

At the moment I'm leaning towards CNMG for general purpose (easy to find and relatively inexpensive) and TPG for metric threading at the moment, or should I minimise the number of insert types I'm getting and go exclusively for TPG?

The lathe toolpost can take 10 or 12 mm tools, so if I take TPG as an example, I take it a 12 mm or 1/2" holder would be preferable over a 10 mm for added rigidity, but would a TPG-322 holder be about right, or too big?

Also trying to figure what variety of inserts a holder can take, e.g. with the above TPG-332 holder, will it work for different tolerances and different corner radii? I think the answer is yes to both, but I'm not sure.

And if I'm spouting complete rubbish, please tell me!

 

[PhotonFanatic]

I'd strongly suggest that you visit some of the major manufacturers' websites and download their insert and toolholder spec sheets, such as this one from Sumitomo, just as an example. Read through them all, which will initially be more confusing than helpful, but after reading enough of them, you will have a better idea of what is available, and why.

One of the best sources for info on product is Sandvik, so try to get their distributor to send some to you, as has already been suggested.

This page from Carbide Depot is helpful, but check under Technical Resources for more, too.

To quickly answer your question, a toolholder for a specific insert will have an inscribed circle that pretty much determines the size of the insert, but the inserts will come in various radii, which is usually designated by the last number, i.e., 432, where the 2 means 1/32" or .8mm.