Newbie- What is the difference on 321 inserts??

[wrechin2]

I am new to the machining world and Have bought a boring head with a attachment that uses TPGB 321 inserts. I see they are all kinds of 321's like a TNMG 321 and 321's without holes. Where can I find what all this means. I need to know what bits would do good in cast iron, chrome, and aluminum. Thanks to all that reply!!!!

James

[wms]

Where can I find what all this means.

http://www.anconline.com/nomenclatur...ureinserts.htm

[wrechin2]

THANK YOU!!!! Should help big time!!!!!!

[wrechin2]

How do you know what materials they cut? Is there a thickness or what that makes them different? Thanks!

[mc-motorsports]

Originally Posted by wrechin2 I see they are all kinds of 321's like a TNMG 321 and 321's without holes.

With a hole is intended to be mounted with a counersunk torx head bolt, or when they are that small, usually called screws. Without the hole is made for tool holders that use clamps to secure the insert, some require "chip breakers", some don't.

See the picture I attached, you'll probably need to save it zoom in to read it, but I checked and it's pleanty clear enough to read.

Your TPGB-321's are going to have an 11* relief which will fly through aluminum, but the sharper edge will break down faster on harder materials. Your TNMG inserts are going to have a 0* which would be better for cast iron.

Then you have your diffrent grades, usually C1 thru C8. And each manufacture has thier own "code" for the grade of carbide, I use the ISO ANSI C1 thru C8.

You REALLY need to get your hands on a general tooling catalog. I have 2 catalogs for the two local suppliers I deal with. So many variables as far as relief angles, tolerances, with a hole or without, with a chip groove or without, so on and so forth... The list goes on.

My one catalog has 223 pages of just milling and turning inserts. The total catalog is over 1700 pages, but 223 pages of inserts should explain that it's kinda complicated. Once you've been doing this for a while, more than likely you'll use a handful of inserts over and over, you'll be able to order off the top of your head and will only have to reference the catalog for something special like a specific grooving insert or what not.

www.shopsupply.net and www.jtsmachine.com are who I buy all of my tooling from, both are within 15 minutes drive. I would get a catalog for my local supplier if I was you.

Good luck,
MC

EDIT: would be nice if I remembered the attachment

[wrechin2]

The other site has that same chart, but you said the 11* angle is good for aluminum and the 0* is better for steel. So the difference between materials that are being cut are the angle of the bits?? That is what I was asking.

I have a MSC "big book catalog" like 5,000 pages. I noticed the other day it had what to end mills worked best on what materials.

Thank you for your response. Sorry for the very simple (To you guys!!!)questions.

I have another question.... When cutting a 75MM hole in 3/4 aluminum, how would you get the starting hole cut to finish it to 75MM. Are there bits that go into a boring head that will cut through or what kind of different tool?

[mc-motorsports]

Originally Posted by wrechin2 The other site has that same chart, but you said the 11* angle is good for aluminum and the 0* is better for steel. So the difference between materials that are being cut are the angle of the bits?? That is what I was asking.

Relief angle, rake angle and grade are your 3 biggest factors. Cutting edge radius can make a difference also

[mc-motorsports]

Originally Posted by wrechin2 I have another question.... When cutting a 75MM hole in 3/4 aluminum, how would you get the starting hole cut to finish it to 75MM. Are there bits that go into a boring head that will cut through or what kind of different tool?

That question is too general to answer. Did you mean you need a 75mm hole in a piece of aluminum? Thru hole? Blind hole? How deep is the hole or how thick is the material?

Boring heads are finishing tools, you're only going to take out the last .05 to .5mm of material using a boring head, you'll need an existing hole, use the boring head and boring bar to make a nice round hole within a tight tolerance with a good surface finish.

[wrechin2]

Thanks. I will be glad when I understand all of this!!!!!!

[CarbideBob]

Inserts and their holders are matched sets.

The letters call out a specific shape to the insert. This insert needs to be used in a holder designed for this shape. You would not use a TNMG in insert in a milling cutter made for a TPG, it just won't work.

Cutting geometries are divided into 2 main classes. Positive and Negative.

In a positive geometry the cutting tool drags across the surface. In a positive geometry it slices into the material. Negative inserts are stronger and have twice as many cutting edges (the top and bottom surfaces are the same size). Positive inserts are weaker but use less cutting pressure.
Aluminum cutting inserts are high positive rake (20 degrees) and are set at extreme angle in their holder.

Imagine a cold chunk of butter and you have a butter knife.
Hold the knife so that the top twisted towards you and you drag it across the surface. This is negative cutting.

...... /
....../ -->>> negative cutting
...../---------
__/

Now twist the knife so the bottom edge is towards you and pull it towards you. This is positive cutting.

. .\
. ...\ -->>> positive cutting
. .....\-----------
_____\

The top surface of the insert is positioned in a pos or neg direction by how the pocket is oriented (twisted) in the holder. Flat holders are called neutral but from a design standpoint this is negative cutting (hold your butter knife straight up and down).

Soft materials like aluminum do not like negative cutting actions.

On top of this carbide comes in different flavors. This is done by changing the recipe and adding things like titanium carbide to the mix which make a harder carbide for finishing and tantalum carbide which increase heat resistance. On top of this you place a variety of coatings, each of which has a specific use. This is the wide variety of grades you see in the marketplace. I make over a hundred different grades of carbide inserts.

Tooling designed for cast iron cutting does not work well on aluminum.
A tool designed for aluminum will chip very quickly when cutting steel.
A TPGB will be normally be set up for steel finishing. It will work on aluminum but not as well as a TEC tool (which would take a different holder)

Yes it's all very confusing at first. All the manufactures have info on the correct use of their tools and recommendations for which grades work best on different materials.

General grade usage: C-2 honed for cast iron, C-5 and C-6 for steels, C-3 grades with a up-sharp edge and polished top for aluminum.
All around do everything inserts: C-2 uncoated up-sharp inserts.

Note that this is a drastic generalization of the subject and you can get away with all sorts of non-optimal cutting conditions if you take it easy on the tool. However some combinations just don't work. For example you would not want to try cutting aluminum with a heavy honed and coated steel roughing insert.
Bob

[wrechin2]

MC-Motor sports...
I am needing to put a through hole in it that the finish bore is 75MM. My question is how do I make the starting hole? I understand the finishing part, just don't know how to start it. Thanks for your help.

CarbideBob,
So negative for steel and positive for aluminum. Now what about CHROME? I intend on boring Outboard engines and they have steel sleeves, chrome plated aluminum cylinders, and at times I will have to machine the aluminum to accept larger steel sleeves. These are the materials I will bore. So I will need different boring bars for each?? Thank you for your help.

James

[diecutter]

Positive relief indexable carbide inserts require less power to make a cut and produce a smoother finish which make them ideal for small lathes such as the 9X20. The negative inserts are more durable, can make deeper cuts, and you can flip them over and use the other 3 tips which is why they are used so widely in production machining.