Nice Finish but Can’t Break a Chip

[Shawn_Laughlin]

I just purchased a brand new Grizzly G0791 lathe/mill combo which is the first of either I’ve ever owned,operated or even been around and I’m quite surprised with the hate these machines get. I’ve been using a 2” and 2-1/2” face mill with all but 1 insert removed and getting excellent results but that’s a whole other topic. My issue is on the lathe side of things. I’ve got about 3 solid weeks of using it and just last I was able to finally get an almost mirror finish on some, what I’m pretty sure is a36 with a roughly 2” od, but can’t break a chip. I get these long stringers which are a pain in the but.

Will too low or too high a feed rate cause this? I’m using a 5/8 holder with a wnmg insert. 1000rpm ,525 give or take a couple sfm, dry, feed rate not exactly sure bc I was changing gears so much I just quit looking the chart and would just move the pin to the next hole till I got a good finish. Thanks

 

[benmychree]

Feed rate is important with cutting tools with built in chip breakers, also depth of cut is important, if you want to break up the chips; personally, I like to see tightly curled chips that break off frequently. I use mostly TPG inserts with an adjustable chipbreaker on a toolholder that Aloris sells.

 

[mmcmdl]

Your chips should look like corn chips with the proper feed and speed . Some machines can't provide them . John's information is correct that it may be your tooling .

 

[benmychree]

I would like to avoid the corn chips as much as possible, they come flying at you in all directions, and burn you quite nicely; I like spirals that break off because they don't fly in all directions and don't typically get tangled up in the carriage handwheel.

 

[Illinoyance]

In general, if the chips do not beak the feed rate is too slow. Others have told me that the depth of cut needs to be equal to or greater than the tool nose radius for the chipbreaker to work. For hobby sized lathes I suggest buying inserts with a light finishing chipbreaker design.

 

[markba633csi]

Regardless of the chips, your surface finish certainly looks nice
Also, you won't find any machine haters here; we don't do dat
We dogs would rather learn new tricks with the stuff we have

 

[Bamban]

The last barrel I turned cut differently from the batch of 12 I was working on. The same set up as before, on the first roughing cut, chips came out small Cs flying out everywhere and some of those smoking Cs found their way on the front of my shirt and burned holes in it. Had to change speed, feed and DoC to get what I want.

You can see some of those Cs in the foreground.

 

[SamI]

I would like to avoid the corn chips as much as possible, they come flying at you in all directions, and burn you quite nicely; I like spirals that break off because they don't fly in all directions and don't typically get tangled up in the carriage handwheel.

A chip shield like this works wonders for protecting your hands. Doesn’t stop them getting down your shirt though...



My only gripe with it is that, being a magnetic base it is, quite literally, a magnet for chips!

 

[ThinWoodsman]

I put magnetic bases in a ziploc bag with a small hole cut in it for the indicator stem, chip shield posts, etc. Small rubber band to keep the chips from burrowing into that small hole. It looks ugly but nobody else really has to see it

 

[Shawn_Laughlin]

Holy crap I didn’t know there were so many replies. Thank y’all. I have tried as many combinations of speeds feeds and depths and can not find a spot that produces chips. Also I’m the dang radial striations I guess is a food word that are bothering me. I’m new to this so I don’t know what to do. The lathe bolted to the croncrete and leveled dead on. The machine vibrates and wobbles even though it’s secured and that’s before I touch off with my tooling. I can hear harmonics that are coming from the end gears. The end gears were installed where the mesh was sloppy so moved the idler gear closer in and helped a bit but I think the sound is resonating into my work piece,it had to be. I don’t want to spend money and time trying to figure out how to do all the wiring for a 3phase motor and vfd if there is a major problem elsewhere that can’t be fixed. Ugh