Newbie- machining with a boring bar

[Rich 72]

I have to ask because I'm just a maintenance tech and have done very little programming.
We are running an EMag vertical lathe and machining the ID of a part with a boring bar but are having issues with chips getting stuck in the part sometimes breaking the boring bar during the program. My question is do you have to machine the part by running the bar into the part or can it be done while pulling the bar out of the part thus pulling the chips out at the same time?
Thanks
Rich

[Geof]

Back boring is possible but most boring bars do not have the tip oriented correctly to place clearance at the back of the tool. Also the tips normally do to protrude far enough from the bar to take a good cut.

[Rich 72]

Geof
Do you have any examples of these bars? The bar being used is a Tungaloy # E12Q-STUPR1103-D140. Like I said I'm not a programmer, just trying to get a better understanding of what is going on and the programmer won't tell me anything

[Geof]

Originally Posted by Rich 72 Geof Do you have any examples of these bars?..

Sorry, no. I made one many years ago for back boring on a manual lathe by the crude method of welding a brazed carbide tool onto the end of a piece of round bar.

[gene rhodes]

machining a part with a back-cut tool is possible and can be done using a positive feed ( away from the chuck). We use a 2" boring bar with a removable head that uses a DNMG type insert. This has worked for years and seems to work quite well. We have been looking into trying this operation on some smaller material and have found that there are actually a few different size tools, mostly using a VNMG type 55deg. insert, that are readily available.
And yes, the ideal toolpath to follow is extend into part first making sure not to rapid or "plunge" into material at any more than a 30deg.This "blending" effect should help to improve your issues. Keep in mind that if your cutting to a specific point, where material is actually being left on the ID, such as a wall, that depth of cut also pertains to the vertical remnant as well.... if one or more passes is futher (away from the chuck)than the previous by an excessive amount, then this too can cause your problem

[g-codeguy]

We are running 3 Emags. Can you give a little more information? For a start, what kind of material? What I.D. size? Starting with a solid slug or tubing? Drill size if using one? Surface feet? Feedrate? DOC? How close to the jaws are you boring? Square corner? Insert grade, style and chip breaker?

EDIT: BTW, roughing is always advisable to turn into the chuck if possible.

EDIT 2: Do you have coolant thru the spindle? High coolant pressure? Besides M8, what other M-codes are you using in the first few blocks. (Don't care about the M3.)

Sorry about not getting all the questions asked at one time. Been a while since I programmed the EMAGs, but it is coming back.

[gene rhodes]

BTW, roughing is always advisable to turn into the chuck if possible.

This is a true statement, but in this particular situation, unless I seem to misunderstand his problem, he is in need of a tool that requires a positive feed...away from the chuck.

[g-codeguy]

Originally Posted by gene rhodes BTW, roughing is always advisable to turn into the chuck if possible. This is a true statement, but in this particular situation, unless I seem to misunderstand his problem, he is in need of a tool that requires a positive feed...away from the chuck.

I was hoping to be able to help Rich eliminate the chips packing up and still cut in the normal way without having to maybe buy new tools. Like I said in my original post, we are running 3 EMAGs, and don't have to resort to cutting from the spindle to the front.

[gene rhodes]

I understand and your advice is not incorrect. After rereading his post, I'm wondering... just how much are you trying to remove on a single pass?? We have never been able to "remove" chip build-up but I do know that poor chip evacuation due to the closed in area being machined in combination with improper cutting depth, feeds, speeds, etc. will definitely lead to problems of his nature....regardless of feed direction. You might even have to instill an "optional stop" allowing an opportunity to clean the chips before the build-up becomes too much.

[g-codeguy]

One thing I forgot to ask was the size of the bar being used. Sometimes a bar that just clears the hole is used. Although it will work, it doesn't give the chips any where to go. Chips couldn't fall out if they wanted to.

You are right Mr. Rhodes. There are a lot of variables to be considered. That is why I asked so many questions. He could be feeding too slow. The DOC might be too shallow for the chip breaker being used. Is he using the correct grade for the material being cut? If he is cutting to a shoulder with the wrong grade, he can easily wind up chipping the insert. Etc. Etc.

[Rich 72]

Sorry haven't been on here for a while but I'll get all the info I can and post it here on Monday.
Thanks
Rich

[Rich 72]

Sorry guys,
Product development manager found out what I was doing and has told me to stop all attempts to improve the process. I guess they like to break $400 boring bars 2-3 times a day