Turning Tool And Facing Tool Questions

[Doubleeboy]

Carlo, you can control chip stringiness to some degree without a chip breaker by varying your feed or speed. So If you are turning 1020 or 1018 and you are getting stings on your roughing cut try taking a deeper cut, or faster feed or change your speed. Using cobalt HSS I like a lightly tan chip, with plane old chinese budget hss I like a little less than tan. I keep a bent coat hanger to rip strings with if necessary. Sometimes you find the feed and speed and depth of cut you want for a fine finish and still get strings, I just rip em out of way before they ball up on the chuck or toolpost.

cheers
michael

 

[mikey]

Glad you gave it a try, Carlo. You're right; if the tip slants down, that is a negative rake. This works but you need a lot more power and rigidity to use it well.

I'm glad you gave back rake a try. Now you can play with your tool angles until you find what works for you. I would guess that boosting the side relief and side rake angles a little will further reduce cutting forces and allow your lathe to cut with less effort, too.

I agree with Mike - our cutting conditions (speed, feed, DOC) have a lot to do with chip formation, as does the material we are cutting and our tool geometry. Stainless and Aluminum in particular like to form stringy chips that are sharp and dangerous. I tend to take very heavy roughing DOC with these to reduce this tendency. Hand feeding also helps to break the chips off. Then I take a light finishing pass with power feed to get the finish I want. My stainless tool has a lot more side relief and my aluminum tool has more back rake than normal and these changes help in those materials.

 

[Strtspdlx]

I think before I
Mess with angles too much I either need to fix my belt sander or get a stone dresser for my bench grinder. It is t completely flat which makes it challenging to get an even finish on my tooling. I've thought about using chip breakers also but I've heard they take more tool pressure to properly use. Is this true? Also on tooling this small. 3/8" I believe. What is the best way to grind a chip breaker? I doubt I could grind it using the corner of the wheel.


Regards-Carlo

 

[Joe Pitz]

Hey Carlo,

Adam Booth has several videos on chip control and cutting a chip breaker.

One thing to note though, he is using a heavy lathe, so he is not applying the steeper back rake and side rake/relief angles that mikey has suggested to adjust.

But otherwise, some nice videos on the performance you can get using HSS tools.

He is using 1/2" tool blanks, but you can apply most of his technique using 3/8" tool blanks.

You might be able to cut the chip breaker with a diamond tile saw or a Dremel tool.

Thanks

Joe

 

[mikey]

Those videos are impressive! Big lathe taking very big cuts - Wow!!!

Chipbreakers work, no doubt about it. I've messed with them in the past, mostly to try to deal with the chips from Aluminum and Stainless, but decided that the hassle to grind them wasn't worth the effort. It was an honest effort over about a 6 month period that varied width, depth, angles and closeness of the channel to the cutting edge. When I tried them they curled the chips into more compact curls that eventually broke off so there were no 4 foot long Aluminum chips going past me. My real problem with them is keeping my tools sharp. Dunn0, maybe I'm doing it wrong.

I have ground them in both 1/4" and 3/8" bits with the corner of my grinding wheel and also used a Dremel and an air die grinder using fiber reinforced abrasive cutting wheels and found that it is very fiddly to get the edge of the chipbreaker channel to line up precisely with the side cutting edge. In the video, Adam is not trying to do this but that may be because he has a lathe big enough to allow that. I just know that this does not work well on a little lathe like my Sherline; I have not tried it on tools for my larger lathe. On the other hand, it might work for you, Carlo, so give it a try and let us know how it goes.

Oh, if you do get your belt sander up and running, Carlo, do yourself a favor. Build a good tool rest that can be set at precise angles and use a ceramic glass platen under the belt. The glass is sold by knifemaking suppliers and is called Pyroceram. It will stay flat for many years and is worth the low cost.

 

[Doubleeboy]

I quit fooling around with hand ground chip breakers a while back. Yes , I could get one to work, but it made later sharpening problematic and did not seem worth the trouble. Like Mike said, you can interrupt the cut periodically. While not something I would do for a fine finishing cut, it works great while roughing. Considering how small the chips are when taking a finish cut, even if it goes continuous I just pull it away with a hook tool. If you have the room a vertical shear tool will make a great finishing tool and swarf is basically miniature steel wool. Anyone can grind a shear tool, there are several you tube videos I believe, and its been written about on most of the machinist boards.

cheers
michael

 

[Strtspdlx]

Well the belt sander idea was a flop. I remembered it being a lot nicer looking. It doesn't have a belt and the motor wiring was cut all the way into the case. That and the person that was supposed to give it to me decided to not do so now.
Anyhow I was taking a .040 cut on my lathe and I realized if I didn't make the cutting edge so long I may be able to use the unground part of the tool as a breaker of sorts. I'm going to attempt to grind a new tool and see if it may work. These long stringy chips keep throwing little chips and whatnot everywhere. And they aren't very fun to clean up.


Regards-Carlo

 

[Joe Pitz]

Hi All, Here is another cool video from Tom Lipton on tool grinding and chip control.
He grinds a tool very close to how Mikey would grind it, but with less side/edge relief. But he does grind a fair amount of back rake.

Using a 1/2" tool he very easily turns steel at .875 DOC, at .005 and .010 feed rates.

Pretty amazing video using just HSS tool blank.

Thanks

Joe