Chip Control

[littlerob]

Hey guys I want to know what you think. When boring (or turning I guess) does an increased feed rate create a smaller chip or a harder chip? Maybe less time to generate heat? I'm boring 1.75 start hole with 1.5 bar and trying to evacuate the chips F.R .015ipr but there just isn't enough room for the chips to get around the bar, at least for the first couple passes. I know there are unconventional and alternative ways to go about it. But if I can create a smaller chip I can get it out of there. Thanks

[spock]

you might try smaller depth of cut at a faster feedrate, (to help them break) till you get the bore bigger than the bar.

[mrainey]

You don't say how deep you're boring, but consider this approach:

Say you're roughing out to 3" diameter x 4" deep. Start by boring to 3" diameter x 1" deep, then 3" diameter x 2" deep, etc, Work back in steps like that and you'll have fewer problems with chips trashing your tool.

In extreme cases, you might want a program stop after each step to pull remaining chips out of the bore.

[sluggo]

To answer your first question, a heavier or faster feed rate is a heavier thicker chip

[littlerob]

thanks sluggo that is what I wanted to know. Though I kicked the feed up to .02 and used a different chip break and it is working fine now. Experiments are key if you can afford them right?

[Geof]

As you found out generally if you push it harder you get a tighter broken chip.

Another approach is to use G83 for the first few passes so the tool retracts and lets the chips out.

Or use G74 (or G75 I can't remember) and peck your way in without retracting.

[littlerob]

Thanks Geoff, im running an Okuma are those codes drill cycle codes? (g83, g73) I understand the logic of tricking the machine into thinking it is drilling but the language is a little different on an Okuma, drilling would be G74. Im just trying to understand if that is what you are saying.

[Geof]

Yes, G83 is peck drill with R plane retraction on my machines (Haas). G74 and G75 are peck grooving cycles, I cannot recall which is face and which is OD. These cycles do not do full retraction they just pull back a small distance that you define.

On Haas I can set these cycles up and give them a Z and a string of X coordinates and they will peck to the Z, retract, step over to the next X and then peck to Z again.