PDA

View Full Version : using mismatched insert tooling question



mikem
01-11-2009, 05:43 PM
John S. mentioned on another thread that he has a lot of inserts that he got at an auction. Me too, but I am not as smart on how and where to use them. I bought holders that some fit but many will require homemade holders.

Some are yellow coated, some are metal gray. They drawer that holds them is full and weighs about 30 lb. They are really heavy. Most are so sharp on the point that I wonder how they are intended to be used. Surely you don't dig that point into the work at 90*? If you use them at an angle won't that leave a spiral cut on the work?

Anyone have a suggestion that would help me learn more about them and their use? Not so much interested in the scholarly approach but more of a down and dirty approach that the average HSM can understand.

Carld
01-11-2009, 05:48 PM
You would use them just like you do a HHS or brazed carbide cutter. I don't know what you mean by feeding them in at 90 deg. That would be a plunge cut to me and you can't go very deep untill you start chatter.

mikem
01-11-2009, 06:07 PM
By feeding in the point, I mean with the point at 90* to the work.

When I grind HSS bits, I usually put a radius on the end and cut with that. If I cut with the tips of these inserts, they would dull quickly and if the feed wasn't really fine, they would leave a spiral on the work. The cut that the insert tip would make would be narrower than the feed per revolution.

Thinking more about it, I imagine that the longer edges have to be used, maybe at 15 to 30 degrees to the work and fed so that the tip is trailing the cut so it doesn't dig in?

SVS
01-11-2009, 06:28 PM
Two points:

You'll get better advice if you take the time to look up what inserts you have.

You've got a lot of them-Go ruin a handful and try'em out.

lwalker
01-11-2009, 06:45 PM
I second that!

I received a few boxes of TPG322 inserts in trade with someone on here and just this afternoon used one to make a flycutter. Cutter was designed so I could change the rake angle (although with only 7 deg relief on the insert, I can't change it by much :-). It was a fun Sunday afternoon project. I would probably never have attempted it if I didn't have so many inserts that I wasn't afraid to trash a few while I got it right.

Never used a flycutter before, and I was absolutely amazed at the finish it leaves on aluminum.


Two points:

You'll get better advice if you take the time to look up what inserts you have.

You've got a lot of them-Go ruin a handful and try'em out.

bobw53
01-11-2009, 06:53 PM
You didn't say exactly what inserts you have, but generally they don't come with much less than an .008" rad. Anything that is smaller than that is usually only used to meet a requirement of a small radius at the base of a shoulder. They will also put less tool pressure on small diameter/long overhang stuff, but mostly they are useless, though they can be hard to find.

And you are right, they aren't very useful otherwise, not so much dulling, but they are fragile. Not very good for roughing, and a really slow feed on the finishing.


Anyone have a suggestion that would help me learn more about them and their use? Not so much interested in the scholarly approach but more of a down and dirty approach that the average HSM can understand.

I take a little bit of offense to this, there really is no difference. You're going to end up at the same point, its weather you get there through a lot of trial and error(which can get expensive), or you know where to look to get your starting points. It doesn't matter if you are running a 25hp 12,000lb CNC lathe or a chinese 9X20, all the same principles apply.

I do this for a living, and I have a 12,000lb cnc lathe and a 9X20 chinese lathe, they both make money, obviously one more than the other. I apply the exact same principles to both. Speeds, Feeds, DOC, cutter geometry and limiting HP. Its really simple stuff, keep the down and dirty and creative stuff to the way you attack the part, set up the part and fixture the part. Why reinvent the wheel.

Back to your inserts, how do you use them, well, they are no different than HSS, they can just run faster and survive(that statement is oversimplified). Same principles apply, though the geometry may get a bit more complicated. Rake, relief, nose radius, edge hone, etc.... So. Look at the geometry of the insert, figure how you would run it if it was HSS, and then run it at a higher surface speed, tweak to suit.

wierdscience
01-11-2009, 07:16 PM
Here is a page that can help you identify what you've got.

http://www.carbidedepot.com/DynamicLanding.aspx?CategoryID=1

Once you know what insert it is,look up a holder for it,they usually have a cad drawing of what the holder is supposed to look like in terms of angles,clamping method ect.

It also helps to know what a replacement insert will cost if you should ever need any.Many inserts are under $10 ea,but just as many are over and quite a few are upwards of $20ea.

Also keep all your busted carbide or unusable inserts,the're worth money-

http://www.kennametal.com/carbiderecycling/index.jhtml

Last I sold fetched $7.85/lb

mikem
01-11-2009, 08:16 PM
Sorry about the request for "down and dirty" info, it is just that some of the posters here take their answers way beyond what I would need or understand. For example, which way electrons flow, sub-atomic particles effect on magnetic fields, etc. My day job is hectic and sometimes I don't want to think that hard. :) It wasn't meant that geometry isn't important or that your advice is not appreciated.

Wierd--I like those sites you linked. Will look some of the numbers that I have up when I get home.

Thanks for all the help to all!

lazlo
01-11-2009, 08:34 PM
Mike, here are two more charts from Carbide Depot that should make it a lot easier to identify the inserts you have:

Chosing Insert Shape (http://www.carbidedepot.com/formulas-insert-shape.htm)

Insert Designation Chart (http://www.carbidedepot.com/formulas-insert-d.htm)

The two key things to identify are the insert are the shape (T = Triangle, S = Square, C = 80 diamond, ...), and whether they're positive or negative rake inserts.

Negative rake inserts (TNxxx, CNxxx) have flat (90) sides, and need a negative rake pocket on the toolholder to tip the insert down.

Positive rake inserts have a 3 - 30 rake on the sides (7 - 15 is the most common), and sit in a flat pocket. These are really easy to make scrap-box insert holders.

SVS
01-11-2009, 08:38 PM
I'm going to extend my comments a bit.

I fell into a big pile of the CNMG and WNMG inserts and holders to match.(Fat and skinny 1/2" ic diamonds.) I like the big diamonds for any general turning or facing. Skinny ones for profiling and boring. I've got CNMG holders for each insert orientation so can theoretically get 8 points per insert. You do need a horse to make them run right.(Enough speed, feed, and DOC to get finish and chip breaking.) These are sorta antique but cheap and pretty good.

The little triangles are cheap, versatile, and not bad at all-But the cheap little holder sets are often pure junk.

A buddy of mine swears by the Trigon inserts-Pretty close to a do anything insert.

I have a 1" APKT/APET insert endmill and really like it, plus a 4" facemill for the positive rake squares-Good on a solid machine, but again old tech.

mikem
01-11-2009, 08:52 PM
I printed the charts out and will put them with my inserts so I can figure out what I have and do a little experimenting. Thanks to all who posted.

Maybe I will try one of the inserts when I build one of the ball turners that some of the guys have posted lately.

Teenage_Machinist
01-11-2009, 08:52 PM
Grey inserts are uncoated.


Gold inserts are TiN coated which makes them last longer and reduces gauling and welding.

If you are not using CNC/ do not require exact indexability, you can make them young again a few strokes of a diamond hone.

Check what the radius is. It may appear small and yet be large if it is only on a small area.

lazlo
01-11-2009, 09:07 PM
Grey inserts are uncoated.

TiAlN or TiCN coating can be grey.

Teenage_Machinist
01-11-2009, 10:13 PM
Hmm that changes things....


Also there is one version for cast iron and nonferrous and another for steel that is shatter resistant I think.

bobw53
01-11-2009, 11:15 PM
Sorry about the request for "down and dirty" info, it is just that some of the posters here take their answers way beyond what I would need or understand. For example, which way electrons flow, sub-atomic particles effect on magnetic fields, etc.

I was being a little sarcastic when I mentioned actual offense. But honestly, and I do this for a living, thinking about cutter to metal interfaces is very relaxing, I actually find it quite fascinating. Theorizing about it can never hurt and it may be on the 3rd to 7th burner back, but its something that is always clicking. Pull it to the front burner when waiting for a plane or trying to get to sleep, driving down a boring road isn't a bad time either. Nothing is better than a good machining dream, especially one that makes you money.

Teenage machinist, grey does not necessarily mean uncoated, Lazlo is right, and actually most of the uncoated inserts I've come across are shiny silver.

TiAlN can come out as somewhere between grey, purple, pink, as can a TiCN coating. There are also some other wierd ones out there. Inserts tend to have more specialized coatings(layers of different coatings, and underlying substrates) than endmills/drills and can come out looking funky, so, going by color can really lead you astray.

It really is best to know what you have from the get go, especially if you are going to run it balls to the wall.

Carld
01-12-2009, 12:12 AM
mikem, to address your statement that the insert leaves a threaded appearance on the work tells me your using to high a feed rate. Try slowing the feed down to about .005" to .010" and see what kind of surface finish you get.

Also, what rpm and depth of cut (DOC) are you using? Do you have a book telling how to use lathe cutting tools? A right turning tool will have a cutting edge that is perpendicular to a shaft in the chuck and remove metal while moving toward the chuck. A triangle shaped tool can be used straight in to the work with the triangle cutter set as if cutting a thread. That would leave an angled shoulder on the shaft.

lazlo
01-12-2009, 09:31 AM
mikem, to address your statement that the insert leaves a threaded appearance on the work tells me your using to high a feed rate. Try slowing the feed down to about .005" to .010" and see what kind of surface finish you get.

To add to Carl's advise, picture the radius of the tool tip as creating circular grooves on the workpiece. For good surface finish, you need to have a feed rate (inches per revolution) that's lower than the tip radius, or you're creating fine circular threads:

http://www.custompartnet.com/images/calculator/turning-surface.png

You can actually calculate the surface finish according to the tool radius and the feed rate. If you play with this calculator a bit, you'll see that you can get down to 16 microinch finish (usually surface grinder territory) with a large tool radius and very slow feed. This is the old timer's finishing tool that's a large half-moon, on the slowest feed your machine has. Of course, that presumes a very rigid machine with perfect bearings :)

http://www.custompartnet.com/calculator/turning-surface-roughness

mikem
01-12-2009, 11:23 AM
Carld and lazlo--that answers my question. Nice picture that shows the problem. My triangle inserts have really sharp points. I have lots of the diamond shaped ones and they usually have a much bigger radius. ( I think that I paid about $35 for a box with over a hundred of them at a surplus auction.)

What would the typical uses of the triangle inserts versus the diamond ones?

Thanks for all the replies!

lazlo
01-12-2009, 12:02 PM
What would the typical uses of the triangle inserts versus the diamond ones?

That has the least complicated answer: the triangle inserts have 3 tips, and the diamond inserts have 2 :D
Double both numbers if it's a negative rake (flat-sided) insert because you can flip those over and use both sides.

The reason for the diamond inserts is because you can turn and face without moving the toolholder.

The Trigon triangle inserts (Wxxx) are the best of both worlds: they have 80 angles on each of the three tips, so you get three edges per insert and can turn and face...
http://www.iscar.com/Ecat/illust_M/490.gifhttp://www.iscar.com/Ecat/datafile/PICTURE/490.gif