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View Full Version : New carbide inserts/toolholders--mistake?



krems
01-10-2007, 02:54 AM
UPS dropped off the box to me this morning. I carefully unwrapped the way overpriced sandvik toolholders and carbide inserts. Chucked a piece of 6061 aluminum and tried out the CCGX h10 (3-2.5-1-AL) grade inserts. Perfect cut & finish . I put in the CCMT (3-2.5-1-pf) 4015 insert and tried it on a piece of plated steel rod (6 inch length, 5/8" between centers) that I had lying around. Horible finish... tried various speeds (400-900), feeds / DOC etc. I can't believe it....i'm pis..ed off. I put a DCMT insert in the other toolholder w/ same grade of insert and got the same results. Now I just spent a lot of money on these based on Sandviks recomendations and got the worst finish I have ever had...I got better results w/ some unknown worn inserts that I had laying around. Where did I go wrong???, Did I buy the wrong grade, nose radius, etc. I never did try a DOC over .008" , or feed rates over .006". I thought that the finishing inserts required more speed and smaller DOC, I'm confused and broke.....any suggestions!

PS....would any machine shake/vibration be a factor. I may try those machine levelers as well.

torker
01-10-2007, 10:33 AM
In my limited experience with most inserts...you need a heavy doc to get a good finish. I have a new toolholder also and got fooled on the first few pieces I made. I found that for my finish cuts I needed .010 instead of my usual .001 or .002 that I use with HSS.
My machine isn't quite as rigid as I'd like either.
Not sure what size diameter you meant for that part (5/8" center to center??) but you could be turning it too slow. Most of my inserts require 400 sfm with mild steel. If this piece is 5/8" dia you should be up around 2500 rpm....no?
Russ

DR
01-10-2007, 11:15 AM
Jack the rpm as high as your lathe will go. Increase the DOC. Keep increasing all the cutting parameters until you start getting chip breaking with blue chips.

Try a piece of known material, like 1018. Preferably a little larger diameter to get more sfm.

Shaking/vibration? Yeah, that should be corrected.

krems
01-10-2007, 11:31 AM
My lathe may not be able to handle these carbide bits correctly. If I'm reading my lathe correctly my max RPM is 1200. Older Clausing #6320 13" swing. I may need a differet type of insert that cuts better at lower rpm. Any suggestion on insert grades, make etc that may work on a CCxx, or DCxx toolholder.

High tech on an older machine hasn't worked for me yet on steel. It may be HSS time again.

Krems

J. R. Williams
01-10-2007, 12:14 PM
Krems
Look up a "Speed -Feed" chart for the insert being used. You will find it has a "window" of feeds and speeds for the particular tool. Your comment about a 0.008 inch feed may be low for a typical carbide insert. Operate in the "window" and things will change.

JRW

pcarpenter
01-10-2007, 01:28 PM
Ummmm..."plated steel rod"??

Is this the cheap cadmium plated junk you can buy at the hardware store that machines like bubblegum?

I would offer that as a HSM who has several carbide insert type cutters, often the best finish does come from HSS. The advantages of carbide are the ability to remove material more quickly with less wear. Insert design is based on a particular chipload and taking less than that can change an insert from being positive rake to negative rake. If you feed in far enough for a positive rake cutter to cause the chip to hit the chipbreaker, it may be a positive rake as designed. A shallower cut causes the chip to hit the top of the insert in front of the chipbreaker making for a more neutral-to-negative type rake and this may not make for a great finish. Negative rake cutting commonly produces greater forces on the lathe too, which may be a problem with a smaller lathe.

Of course, having other vibration problems will always be an issue and the source should be examined and fixed.

In short, carbide is not inherently better. For us HSM types, we may take shallower cuts on purpose in many cases which can wear out the edge on an isert before it has done its intended amount of work. Taking a larger cut may produce better results which may seem counter intuitive. The lathe must be solid enough to support this, however, and sometimes carbide makes less sense on a smaller lathe.

I would use the carbide for applications that merit it and certainly don't give up on HSS. I'd also get some material that is known to machine to a better surface finish and take that variable out of the equation. Also, try a shorter piece, chucked up close for the purposes of your tests. Whipping is always a problem with a longer piece between centers.

Paul

Steve Stas
01-10-2007, 05:23 PM
My experience has been exactly the same as Paul Carpenter's. Carbide cutters need a deeper cut to make the chip breaker work, and they aren't inherently sharper than HSS, just tougher, designed for heavy feeds for longer tool life. I also change to HSS for a fine finish when I can't use the heavier cut as a last cut. And definately, machine shake should be eliminated.

steve Stas

DR
01-10-2007, 06:50 PM
Provided the Sandvik inserts are "standard", there should be HSS inserts that'll work in the holders.

Someone here may have a link to one of the companies producting HSS inserts.

HB Rouse company might be someone else to consult. They have high positive inserts similar to the aluminum cutting variety, but coated for steel.

pcarpenter
01-10-2007, 07:05 PM
One other thing I forgot to mention is that the general assumption is that the minimum DOC should typically be at least equivalent to the nose radius...ie for say a 221 it would 1/64" or about .015 for a 222 (or 322 etc...the last digit is the nose radius in 64th's of an inch) it would be around .030" etc.

While they may list one grade of carbide or another as being for finishing etc. the nose radius is no less as meaningful in terms of an insert's value for finishing vs. heavy cutting.

Paul

mbensema
01-10-2007, 08:03 PM
The company that produces the HSS inserts is AR Warner http://www.arwarnerco.com/index.html

I saw their stuff at IMTS last year, looks good, but haven't taken the plunge yet and bought anything. They alos sell toolholders.

Carld
01-10-2007, 09:42 PM
Ok, what the heck does DOC mean???

mochinist
01-10-2007, 09:45 PM
Depth of cut

mochinist
01-10-2007, 09:51 PM
Crap I can't remember what snadvik inserts I use at work, but I do know that I rarely ever run the lathes over 800rpm, they probably do most of their work at 500rpm, anyways I get fine finishes and I don't take no .010" or ".020 doc finish passes, that would suck if I was trying to hold plus or minus half a thou. You probably got some crap material or the inserts arent set at the correct height, or maybe you just bought the wrong ones.

krems
01-10-2007, 11:39 PM
Called Sandvik today and talked to one of the tech reps. He almost laughed when he calculated out the sfm. (1000 rpm max w/ 1/2") steel... I think he came up w/ 125 SFM+/-.......Someone needs to tell me how to calculate the SFM. The carbide insert was basically made for 3 to 4 times or greater what he calculated.....He recommended a larger nose radius w/ a 1025 grade carbide insert at the speed my lathe can operate. I wish the other Sandvik rep would have thought about it before he talked me into buying these high speed 4015 inserts

I'm going to pick up some known steel tomorrow and try again. Yea I was using that junk plated crap that you buy at the hardware store. Thanks for the link to HSS inserts.

MOchinist: Sounds like you operate as i do. Chasing that last thousandths w/ small DOC and slower speeds. If you think about it I'd like to know what insert you were using.

Thanks for all the info!.....................Krems

flatlander
01-11-2007, 12:29 AM
I bought a set of Warner's toolholders & T15 (HSS +15% cobalt) inserts a couple of years ago - even though the T15 inserts are fairly expensive, I think they represent a good value if you shy away from the idea of grinding your own HSS tools. I got a great finish on some mystery stainless with TPMW 222 T15 inserts while building a benchrest style front rifle rest a year ago - it was much easier than trying to find the right combination of doc, speed, & feed with any of the 31.52 TCMT carbide inserts I had on hand. The stock I used had an OD so close to the desired finish OD that there wasn't much room for error while experimenting with speeds & feeds.

I've bought Sandvik TCMT 31.52 inserts in 1015 & 4025 grades off ebay, and it seems the 1015 grade gives a better finish on stainless than 4025, in the limited turning I've done so far with 4025. I don't use much mild carbon steel; aside from chambering & fitting barrels of 416R, most of the stock I've bought to play with is mystery SS from a surplus yard.

BadDog
01-11-2007, 04:19 AM
The basic formula is this:

RPM = (CS x 4) / D

Where CS is Cutting Speed (based on material cut) and D is Diameter. 4 is a VERY rough approximation for PI, but generally considered sufficient for these calcs.

You can look up CS, based on the material you are cutting, from the “Handbook” or preferably from your cutter manufacturer since they may have factors that influence the choice. Typically, low carbon steel has a CS in the neighborhood of 100 SFPM with HSS and around 300 SFPM for Carbide, but that varies based on lots off stuff (see handbook and/or manufacturer). For aluminum, it would be around 300/1000 respectively. Those numbers are supposed to get you into a good starting position where a good balance of material removal, finish, and cutter life CAN be FOUND. You can adjust the parameters from there, and “feed” is also important as is the mentioned affect of cutter geometry and coolant use.

So you can see that for, say, a 1” diameter piece of LC steel using Carbide you would ideally like to turn around 1200 rpms as a starting point. For 1/2 in the same material you would be in the range of 2400 rpms.

The handbook and various other (often simpler to follow) resources provide a full briefing on these calculations.

Hope that helps. (just for you Don, er D ;))


Edit:

As for cutters, I picked up a full set of 1” Kennametal TPG holders (well; left, right, and facing holders anyway) for $5 each that I intend to mill down to 1/2” height (on the mount side) and use for roughing or on VERY hard stuff (or abrasive) that HSS steel just can’t hack it on. I find I rather prefer HSS for most everything so far, but this will get me away from (for the most part) those brazed Carbide cutters I’ve grown to so despise. I also got a bag of 50 C6 Carbide TPG chips (1/64 radius IIRC?) to fit them, so I should be set with the addition of a few alternatives...

mochinist
01-11-2007, 07:57 PM
MOchinist: Sounds like you operate as i do. Chasing that last thousandths w/ small DOC and slower speeds. If you think about it I'd like to know what insert you were using.

Thanks for all the info!.....................Kremstpmr 321 16 03 04 , I use em on everything from aluminum to stainless steels. The finish can be a little tough to get good on 1018, but I don't like running the lathe at 2000rpm, I have seen stuff fly out and it isn't fun.

krems
01-13-2007, 12:22 PM
Thanks for the info guys!...........My local distributor was kind enough to get me a couple samples of the Sandvik 5015 grade inserts (cermet 3 2.5 2 UM 5015) w/ two different sized nose radiuses. Mush improved finish at the speeds my lathe will run. Not perfect but getting closer to what I'm looking for. I think the larger nose radius (2) cuts better. I'd still like to try the 1025 grade but am not willing to spend the bucks before trying first. I ground a HSS bit today and the finish was mush better than the 4015 grade i tried earlier. Will report any progress on how the old clausing (slow as a turtle) lathe performs w/ different inserts.

Krems

toolsrul
01-13-2007, 03:01 PM
The grade you've selected is quite hard & likes higher SFM (.262 x dia. x RPM = SFM) which may be hard to reach depending on your situation. When you select carbide grades for manual machines go with the tougher grades since your SFM keeps changing & you usually run at a lower SFM or RPM. The depth of cut (DOC) rule of thumb has changed, yrs. ago it used to be at least the tool nose radius (TNR) now with technology the chip breaker or chip groove can take a small DOC. Look at the cutting edge of your insert, if you see any shinny area you either took the coating off by the slow SFM or possibly chipped the cutting edge. If Sandvik recommended this grade have them change or use someone who will support you. Remember - all big guys used to be small. Good luck.

krems
01-13-2007, 03:57 PM
Tools:, Were you refering to the 4015 grade insert, 5015,(cermet) or the 1025 grade. I'm following what you're saying but am not sure what insert you were refering to. Thanks!

krems

toolsrul
01-13-2007, 08:10 PM
4015. Another problem that you may run into is the coating. When using a CVD coated insert on aluminum you'll see a rough surface plus build up (BUE) on the insert edge. Reason is that the coating & the aluminum are reacting & is sticking to the coating actually creating an above center line condition. Switch to a PVD coated insert grade. Won't go into the explanation of each - too lengthy. On manual lathes we should be using grades like Kennametal KC730 or KC850 & others. Use old technology from these carbide companies & carbide does works on manual machines. People who are having problems aren't getting any guidance on the situation. Good Luck.

motomoron
01-13-2007, 08:29 PM
2 Big thumbs up for the AR Warner HSS inserts and holders. I finally took the plunge and got the set at Cabin Fever last year, and I've used them almost exclusively the past year.

I spent a bunch of time today turning a 3" long chunk of 4" dia 1020 into a toolpost support for my Smithy 1324. I have a trash can full of blue curls and the insert is unchanged in cutting ability. Surface finish is OK, not fabulous, but a fast thin final cut with a spritz of cutting fluid gives an acceptable result. I played with carbide inserts a while back and found that I had neither the speed nor rigidity to take advantage of their inherant properties.

nheng
01-13-2007, 08:50 PM
For steel, a good speed and feed will produce chips that leave the cut and then turn toward blue. That's not to say you can't cut at any slower speed you want. Try using a cutting oil and take a DOC that is about half the nose radius.

It's possible that your plated rod is something like 1018. The finish on that is always kinda crappy next to aluminum or better tool steels.

Check your cutting edge with a magnifier and see if you have any edge build up. This can be very common running at the lower rpms on your machine. When I turn aluminum with carbide, I flick the build up off periodically with the sharp, faced end of a mild steel rod. Cutting fluid will help to reduce the built up edge. Only high enough rpms will prevent it to begin with. For aluminum at 5/8", its way up there ... 500 to 1000 SFM would require 3000 to 6000 rpm.

Don't let that bum you out. You will still get nice finishes :)

Den