View Full Version : Cutting Tool nose radius

02-11-2004, 12:35 PM
When making a finishing cut at a small DOC and slow feed rate, should you be using a small or a large nose radius when using carbide inserts?


02-11-2004, 01:59 PM
You should use a small radius...

Rule of thumb with radii...whatever your nose radius is, then thats the minumum DOC needed..example: .015 radius means you should have a DOC of atleast .015....Now with the feed you should go about half of your radius..example: .015 nose radius means you should feed at .007/.008 per revolution..There are always exceptions to the rules..

These are the "rule of thumbs" that I follow to achieve fast production and nice finishes and tool longevity...But once again I need to point out that there are always exceptions to the rule...

I also want to mention, that each insert manufacturer and each grade of insert will have their own reccomendations..Its impossible to use the same "values" with every kind of insert shape and grade..what I stated in the previous paragraphs are good starting points..but you may have to "tweek" your DOC, speeds & feeds according to the manufacturers reccomendations...

[This message has been edited by bspooh (edited 02-11-2004).]

02-11-2004, 02:25 PM
Thanks for that valuable info!

02-11-2004, 04:00 PM
Thank you Brent for the education.


02-11-2004, 04:39 PM
Thanks for the thanks.... http://bbs.homeshopmachinist.net//smile.gif


02-12-2004, 05:04 AM
Yeah, what Brent said.

You know you guys can learn this stuff yourselves by asking the reps questions and reading the catalogs - the manufacturers print truckloads of information in their catalogs you just have to learn how to read and understand them a little. Not a big task for a bunch of smart guys.

02-12-2004, 11:55 AM

The reason I asked this question was, most of the textbooks I have say that a larger nose radius gives a better finish. While experimenting, it seemed that a small nose radius at small DOC and slow feeds gave a better finish. Being this seemed contradictory, I wanted to ask those with far more experience than I have, because in my book experience is the best teacher.


02-12-2004, 12:28 PM
Thank you for that elusive bit of information. Do the same rules apply to HSS?

I've been using the "cutting and trying" methodologies with the general rule that one uses a larger radius for roughing, and a smaller one for finishing cuts....there is always that contradictory statement though...to use a larger radius to get a nice finish on the last cut. I often cut long slender clock arbors with integral pinions so my problem is usually with the work piece flexing away from the tool: light cuts/feeds with a small radius seem to cause the least deflection.


[This message has been edited by mmambro (edited 02-12-2004).]

02-12-2004, 04:57 PM
Materials of the workpiece and materials of the cutting play big parts in all of this.

41 series steel for example, you want the full nose radius in the cut or it rubs and scratches. Also higher feed rates are in order for this material

Brass seems not to care, will take high amts of nose radius at small depths. Slow feed rates work well.

Most steels in general, full nose radius or at least 2/3rds according to my experiencs, and the books I have on this topic. Feed rates vary between the 10, 11, 12, 41, and 43 series...

Aluminum will "rub" terrible with a large radius and small depth, but will "burnish" rather than show the scratchy "rub". Of course 6160 I talk of, 7075 will scratch.

HSS likes bigger nose radiuses due to heat dispersion at the furthest most "tip", or the tip wears faster and burns. However, I like my HSS kind of small radiused thus my dilema. Carbide is more apt to work small nose radiuses, but be very careful on the 1/64th radiuses not to intermittient cut or touch the part while stationary (without revolution) or you break the tip.

I often bore with .007 NR tools - carbide, and do fine turn this way, better control on very small cuts. Of course my removal is also small, and I tend not to want to rough the cut with this tool, nor start a bore from a drilled hole with this insert.

Just observations and information fom experience.

02-13-2004, 04:22 AM
forget the damn text books I said the manufacturers technical materials - they have up to date information in their catalogs for any bozo to read if you bother to take the time to do it.

It is not that same as what your text books tells you - that stuff is fifty years out of date and unless your teacher is on his toes they will not be any better - it is the same situation with most shops. Very few companies will even take the time to get a representative in to help them select proper tooling for their production needs and in the end they are just wasting money because of it.

Insert companys spend billions on research and you can't be bothered to draw on their expertise? Duh!

02-13-2004, 10:19 AM

Wow, I'm sorry if I offended you, and asked a dumb question. I was just trying to draw on the expertise of the people on this forum. I will check with the insert manufacturers about obtaining their technical info.

A Bozo that can't read

02-13-2004, 12:32 PM
Ahhh, Thrud's just in a grouchy mood. He's got a heart of gold. Don't let him tell you otherwise. (Start a discussion on stainless steel, he likes that. Nice'n shiney)

02-13-2004, 05:21 PM
Thrud is right. Most of my info and experience come from the inserts, tools, and books given to me by the regional engineering rep from kennematal. I get some great inserts and tools to use and test from him, and invaluable information. His comments to me though - "Look in this book, I can't remember it all...." Friendly and honet, not smart alec, and I like this honesty. Otherwise he would have to remember probably 1000 types of tools and inserts, and probably that many test products and new designs.

The tech manuals are a great resource, and gets to the "workpiece and cutting tool material" aspect of what I stated.

ACF, yours was a very good question, and one worthy of quite a bit of observation and input, for no matter what the book says, there are the variables in a home shop environ that you can pick up from others (call them little unpublished "hints").

Keep up the good work all of you.

02-14-2004, 05:36 AM
I was not calling you a bozo I was trying to make a point.

Very few people, including professional shop owners that should be consulting with the insert companies to maximize their profits, machine time, and tool use never do this. It is called the Ostrich effect - stick your head up yer arse and hope the problem goes away by itself. The problem is it does not.

My whole point was there is this enormous resource out there for all of you to use to your advantage and to learn from - both newbies and pros, and yet so few take the time to take advantage of the enormous funds sunk into materials research to cut metal faster, better, cleaner, cheaper.

..and I might have been a little short that day - if so, sorry. Don't take it personal, I have no hair.

02-14-2004, 10:33 AM
Yeah Thrud, but most of us lazy bastidges would rather come HERE for the wealth of knowledge HERE because we like it HERE! We'll even risk getting chewed on by you because we know your teeth are pretty dull. So lighten up, you crusty old fart, gnaw on yur meatloaf, and be happy we're HERE. Luv ya, Dave! Hugs and stuff. Giz

02-14-2004, 04:33 PM

I won't take it personal, I enjoy you posts here and your witty comments (we all have a bad hair day once in a while). I found some info on the proper use of inserts in the MSC catalog, but would like to have more. Do the insert companies have more info that they will provide to us people that only use a handful of inserts, or do you have to be a "big" user?


02-14-2004, 05:01 PM

I am a small end user of inserts, my yearly insert budget probably the costs of inserts for a short run job in some shops. However, I am not afaid to look and ask.

Contach insert web sites such as kennemetal, and you will find information. You can also request information from the companies. I have Kennametal as a shop "sponsor", also Lovejoy (who produce milling cutters and inserts), but also have contact with SECO, Valenite, Iscar, Sumitomo,and Sandvik.

This is one way, request info.

Another way is to know someone in a shop. They get insert information by the truck load, and would probably give slightly outdated stuff to you, or duplicate info. Outdated info is probably one year of less.

This is how I started to find out about inserts and such when I started to "rebuild" the machining program here at my school from a general metals "ashtray and hammer" program into a full bore voc and adult program. This is also how students find info - through web or shop connections.

Also industrial shows, almost every state has one at some time during the year...These are so fun you can't believe it, and i get so many freebies (two to three shopping bags full each trip). I go to Eastech, but there is also a Vermont, and NH show, and even a Mass. show.

Just some starting ideas. If in a pinch, maybe I can (no garontees) get some Kennemetal stuff sent your way.

Check the site first though, better to get it first hand and often.

02-15-2004, 01:48 AM

If you are a purchaser of Kennametal inserts ofr instance you are welcome to call and speak to their application engineeers - they will assist you in selecting the proper inserts for your application.

For instance if you want a good general purpose insert call them tell them the shape and size of inserts you use (ie triangle 1/4"i.c. (inscribed circle) and the types of materials you are cutting - cast iron, Aluminum, brass, 12L14, 12T14 (tin based non-toxic free machining replacment for 12L14), and occasionally stainless and Titainium. They may ask if you have a ridgid machine or high horsepower - the answer here no to horsepower, maybe to ridgidity depending on the machine. this is to determine if you can use negative rake tools or not, generally stick to positive geometry tools - ask for them as they require far less horsepower. They will then give you the best choices for your application.

They may or may not be coated - don't sweat it - I have V shaped inserts that have Aluminum Oxide coating and they kick ass and take names. They don't have to be "sparkly" to work great.

02-15-2004, 10:01 AM

Thanks to everyone for the input, I'll contact the insert people and see what kind of info I can get.


02-16-2004, 10:33 PM
I like the KC 935 inserts....Solid Black coating, hard as hell, and cut anything they come in contact with quite well at lower feeds and speeds......

meatloaf included.....