# Indexable tooling



## Chop (Mar 2, 2004)

I know that die hards choose to grind their own tool bits, but I'm the lazy type and I prefer to use indexable tooling. One of the things that threw me off about indexable tooling is the cost of those itty bitty inserts.

Any way, I've been wanting to get a decent boring bar to replace the cheap set that I bought when I first got my lathe and The LMS had what looked like a decent Phase II boring bar that took inserts, but they've been out of stock for ever on the inserts.

Well, I found this place, www.carbidedepot.com and what I just ordered to check out are some inserts from their dollar store. $2 each. I thought that was pretty good. I guess I'll see how they do. They had pretty good prices on the non economy inserts too.

Just wanted to share.


----------



## MicroE (Mar 2, 2004)

I have used carbide inserts, but I actually prefer HSS inserts now. Maybe I have been buying a bad grade of TiC and a good grade of HSS, but that has been my personal experience.


----------



## unnerv (Mar 2, 2004)

My Father is a machinist, and he also recommended that HSS is better for aluminum, because it can be cut to a sharper edge than carbide. Carbide is better for the harder metals like stainless steel.


----------



## cy (Mar 2, 2004)

Chop,

Thanks for the link. There are several styles of indexable insert holders. Several styles of indexable boring bars are offered as well.

Which type is best?

Thanks,
CY


----------



## jtice (Mar 2, 2004)

Chop,

I have been grinding all my own tooling bits so far. Even internal threading bits ! /ubbthreads/images/graemlins/grin.gif

(not an easy task)

I have a 6 piece boring bar set, but I also am in need of a longer boring bar.
Right now, I cant bore a 2x123 from one end. I have to flip the piece over and do the rest from the other end.

Let me know what you think. I might get one also.
I also didnt like that I had to buy those expensive tips, but I guess thats better than the entire bar.


----------



## KC2IXE (Mar 2, 2004)

There are special inserts for AL - MOST holders and inserts used in industry are Negative Rake. For AL, you can get positive rake, or even negative rake holders that use inserts that give you a positive rake. Some of the inserts designed for AL have a VERY shap edge - usually referred to as "Upsharp" inserts

One thing - you REALLY want to spin your work up to speed with them

Well - yes and no - but that's a topic for a LONG message, about critical speeds, and the fact that carbide can be used below critical speed, or above it, but all the speed charts only show the "above it" speeds


----------



## chalo (Mar 5, 2004)

Those carbide inserts which have been finish-ground after sintering will deliver better results on materials that require a sharp cutting edge, like aluminum and most plastics. However, because of the grain size (carbide tooling is a blend of ultrafine tungsten carbide powder cemented in a cobalt matrix), there is an upper limit on how sharp any carbide tool can be ground. 

High speed steel can be ground to a much finer edge, and is often a better choice where feedrate, cutting speed, machine stiffness, and/or available horsepower are limited for other reasons. 

Chalo Colina


----------



## KC2IXE (Mar 5, 2004)

[ QUOTE ]
*chalo said:*
...snip... However, because of the grain size (carbide tooling is a blend of ultrafine tungsten carbide powder cemented in a cobalt matrix...snip...

[/ QUOTE ]

Which is why people like Kennametal are affiliated with some of the best nanomaterial labs in the USA - Got to meet some of the folks from the University of ??? who are affiliated with them - the average grain size in carbide goes down every year - makes the carbides sharper AND wear MUCH longer, as when a grain of the carbide tears out (which is the normal mode of wear) a lot less tears out


----------



## tvodrd (Mar 5, 2004)

Chalo is correct on being able to get a _better_ edge on a HSS bit. The big perspective is being able to get your cutter geometry, (rake, clearance, etc) right and its height and overhang and closeness to the chuck (ridgidity) optimized. This is even more critical with the small bench-top lathes most of the cpf'rs are using! (I know, I have one.) (Being able to put 5HP into the cut makes things a little less _sensitive_ to such issues is why I don't use it much. /ubbthreads/images/graemlins/grin.gif )

Larry


----------



## gadget_lover (Jul 14, 2005)

I'm probably not the only one to be confused by the indexible tooling, so I thought I'd share information that took an afternoon to gather.

My objective was to buy some inserts to match the insert holders I had from Harbor Freight. I have the 3/8 inch shank set of holders, part number 39932. That set came with a set of inserts of unknown sopecifications. The holders are identical to the second set I bought from ENCO last week for $19.99. That was part number 250-1400, a "3/8" SHANK INDEXABLE HOLDER 5 PC SET". The ENCO set did not include inserts.

I eventually found that I wanted TCMT21.51 inserts. I got them for $2 to $3 each from carbidedepot.com. Below is the explanation of how I determined what I needed. n You can follow along at http://www.carbidedepot.com/formulas-insert-d.htm.

My first challenge was to find out what size my 3/8 inch tools used. I finally learned that they are not measured by the length of the side nor from tip to tip. It's measured by the size of the largest circle that fits totally within the outline of the insert. This is known as the Incribed Circle or IC. See http://www.mathwords.com/i/inscribed_circle.htm for a picture and discussion.

I suspect that the IC is used instead of length because the other dimensions change with the shape and the treatment of the cutting tips.

Once I learned that I use 1/4 inch IC, I next needed to find out the rest of that silly code. It's all described well in Machinery's Handbook. Page 757 of edition 27, under "Cutting Tools". Some parts of the code are pretty clear and some take some thinking.

It was easy to determine that I was using *T*riangular inserts, so the first letter was a T. The holder is ground to use only triangles.

I measured the angle on the tip of one of my existing inserts and found it to be about 7 degrees. The holder is straight across, no rake. That made the rake 7 degrees, which makes the second letter a "*C*". The web site said that 7 degrees was good for aluminum as well as light cuts in steel.

I wanted a nice, sharp, ground finish, "tolerance" class G but I could not find any that were cheap. I settled for "M" tolerance, knowing that I would have to check the alignment if I swapped inserts.

The last leter was the geometry of the insert. I had screws with a bevel on them, so I need a hole and the hole needed to be countersunk. My old inserts had chip breakers, since it made deeper cuts cleaner. I had specified a rake, so only one side could be used. Add all those up and you get a 'T'

So now we have TCMT. What about the 21.51? That's three fields. 2, 1.5 and 1.
2 = IC = number of 8ths in the IC. In this case 2*1/8 = 1/4 inch IC
1.5 = Thickness = number of 16ths. In this case 1.5*1/16 = 3/32
1 = the radius of the cutting point in 64ths. In this case 1/64th

That't it. TCMT21.51. You can play with the thickness to change the cutting height if your tool post does not have a height adjustment

I had to decide if I wanted 0, 1, or 2 64ths radius. I found that I can see the difference. A 0 is great for threading and for cutting hard materials. It will dull and chip easier. A 1 is a good general purpose edge. A 2 gives a very smooth finish. It should last longer.

Using the right insert makes a big difference. A C2 TCMT221 had a hard time with a piece of steel I was trying to turn. A C6 TiN coated TCMT21.51 cut it like it was butter.

Let me know if pictures are desired.

Daniel


----------



## dat2zip (Jul 14, 2005)

Wow!!!

Thanks daniel for taking the time to detail that so nicely. I think I've got the same set from HF. I need to go out and measure it. But, if it is, I can possibly follow your part numbers and pick up some additional tips. I would like to stock the thread cutting and a general purpose round bit. Those two I think would help me avoid having to sharpen the tool steel ones I use all the time.

Wayne


----------



## Illuminated (Jul 14, 2005)

Thanks for the detailed info, Daniel!

I have the same 5pc set and was wondering about buying new inserts.

One question - where the heck can I get some of those tiny torx screws?? My set came with a few extras - but they've somehow eluded me. I had to drill one out to rotate an insert because the head stripped. That must have been when I lost the remainder of my extra screws... /ubbthreads/images/graemlins/frown.gif

John


----------



## gadget_lover (Jul 14, 2005)

Enco sells the screws for their holder on the same page that they sell the tool holders. I tried the HF screws in my new enco holder and it almost fit. The thread is the same but the diameter of the HF is just a skooch bigger. Probably metric.

Harbor freight sells a set of TCMT21.51 inserts for the 3/8ths shank, part number 39945, $6.99 for 3. I found that, of course, after doing all that research. /ubbthreads/images/graemlins/smile.gif The write-up does not say if they are made from C2, C6 or if they are coated. I'd go with the carbidedepot.com.

One thing I left out of my write-up; Carbide inserts tend to be sold in packs of 10, though you can also order them in single units. Check your order before you click on the button to charge your credit card.

Inserts are made from various types of material, from HSS to carbide to cermet. The carbidedepot site has a little guide under "resources" that tell you which material works with which type of metal. My experience so far has been that the TiN coated C6 works pretty well with the steel and aluminum that I've been using. Having a small machine with limited power makes it more forgiving???

Thanks for the kind words, guys.

Daniel


----------



## Illuminated (Jul 14, 2005)

Thanks Daniel. I wondered whether or not there were any HSS inserts to fit those generic import 3/8" carbide holders made for the TCM21.51 inserts. I'll have to do some more looking...

FWIW - I bought a set of 6mm (I think) pre-ground HSS cutters from LMS for $39.95. Catalog lists them as 8mm, but I use them with a QC tool holder with height adjustment, so it's no problem. Came in a nice little wooden box. I bought them for the inside and outside threading bit profiles, but have found the other profiles useful as well. I like them so far. Though not the indexable insert type, I can root out the LMS part number if anyone else might be interested...

John


----------



## gadget_lover (Jul 14, 2005)

Hey John. I see that LMS has the HSS inserts that are close to the TCMT21.51 as item 1724 and TCMT21.52 is item 1725.

These are actually TCGW-21.51 and 2. The W means a hole with countersink, but no chip breaker.

I sent you a PM, John.

Daniel


----------



## Anglepoise (Jul 14, 2005)

I use an unusual indexable carbide system. Each individual insert has 8 , 12° positive cutting edges. This system works very well with lathes of 1 HP or less that need positive rake.
Made by Hertel in Germany and sold by Kenametal in USA.


----------



## Illuminated (Jul 15, 2005)

Thanks for the info Daniel - I'll check them out. I've been very happy with my experiences with LMS so far.

John


----------



## gadget_lover (Jul 15, 2005)

That's an intresting looking tool holder, David. What are the advantages to that 8 edged insert? Is it cheaper than two 4 edge inserts, or is it just more convenient?


Daniel


----------



## Anglepoise (Jul 15, 2005)

The advantage is 1 only. A very high positive rake angle and lots of clearance. So for people that want to use carbide inserts on a small machine, they work well.
However they are expensive and I use only when cutting stainless etc. My every day insert is a TPMR, positive triangular.


----------

