Boring Bar Push Off?

[Noah Katz]

Quote Originally Posted by litlerob1 View Post
When I use a Spaghetti noodle to Bore holes in Adamantium running 10k SFM, and .5 chipload---I have problems also.....

Funny. It was 900 rpm and I took 0.010 to 0.030 DOP

Depth of Pasta?

 

[litlerob1]

Depth of Pasta?

I was wondering about that too, not as creatively as you. It's good though.

I'm assuming he means Depth Of Pass.

 

[Mot3s]

I was wondering about that too, not as creatively as you. It's good though.

I'm assuming he means Depth Of Pass.

HAHA. Meant to put DOC. Although I do like depth of pasta.

 

[jondee]

This thread has been hard work. I tuned in to it from the email posts I get from the site.

Someone said early on "keep the tip of the tool a little above the centre line". That's 110% good advice. When boring you can have it higher than you might think and the tool will be happy. You can use an eyeglass to check, though you should possess a gauge for checking height of the tool tip.
Tip of tool HAS to be really sharp.
I think MoT3S's depths of cut are considerably too great considering the size of the hole he is boring. On a hole like this start with a cut of .005 or .010 inch and explore.
Convince youself that the tool makes nice swarf and that the hole remains cylindrical. There is no reason it should taper at all. Only when you have shown you are in control of the cutting process should you start increasing the depth of cut.
Use a little parafin or WD40 to lubricate the cutting. A dab with a brush will do.
I don't have a DRO but I put a tenths dial gauge against the back face of the cross slide. This shows me whenever the slide moves. Also you can do really accurate work that way, below 1/2 a thou easily.
I hope that help and don't get disheartened.

 

[awake]

MOT, one thing that has been said, that I'm not sure has been heard: it is absolutely crucial that there is enough clearance so that the tool is not rubbing on the bore below the cutting edge. The smaller the bore, the more acute the clearance angle must be to clear it.

This can often trip up a beginner using a purchased tool - surely it must be right, right? Nope - it likely needs to be ground to suit the hole that you are boring.

Don't assume that inserted tooling will automatically work, either. It will be made to work down to a certain bore size, but below that, it will rub.

Setting the tool above center line is one way to help compensate for the problem. Another is angling (twisting) the boring bar, but this will lead to a negative rake cut - which may or may not work with the tooling and material.

Here's your homework: Draw up the business end of the boring bar you were using initially in CAD, then set that drawing in a .625" bore, and see if the tool is rubbing.

 

[donie]

I really believe that throwing insert tooling at problems without understanding what the problem is, might be a poor way to go. My best advice is to practice on scrap pieces of various metals until you can gain just a little more experience.

 

[litlerob1]

Good Lord. He's not using an Indexable Bar.

R

 

[Mot3s]

This thread has been hard work. I tuned in to it from the email posts I get from the site.

Someone said early on "keep the tip of the tool a little above the centre line". That's 110% good advice. When boring you can have it higher than you might think and the tool will be happy. You can use an eyeglass to check, though you should possess a gauge for checking height of the tool tip.
Tip of tool HAS to be really sharp.
I think MoT3S's depths of cut are considerably too great considering the size of the hole he is boring. On a hole like this start with a cut of .005 or .010 inch and explore.
Convince youself that the tool makes nice swarf and that the hole remains cylindrical. There is no reason it should taper at all. Only when you have shown you are in control of the cutting process should you start increasing the depth of cut.
Use a little parafin or WD40 to lubricate the cutting. A dab with a brush will do.
I don't have a DRO but I put a tenths dial gauge against the back face of the cross slide. This shows me whenever the slide moves. Also you can do really accurate work that way, below 1/2 a thou easily.
I hope that help and don't get disheartened.

Thanks for all the tips. I just ignorantly assumed the ID boring would have gone as consistently smooth as the turning operations had (I guess it should) and I never considered periodically verifying the ID throughout.

I actually did have it slightly high off center given the advice I've seen online(I've noticed people say high, low, and center so... WHAT???). With it high, it kept squeaking. It wasn't rubbing the tool either. Guy running the shop said to center it and that it always needs to be centered(I have a feeling everyone has their own opinions). Anyways, did that and nothing changed. I tried changing rake angles and also rotating.

If I were to make one guess, it's that the tool wasn't sharp enough, and with less give of the material itself further towards the chuck and possible looseness in the cross-slide, it just simply walked. But who knows?

The new boring bar I purchased with an insert had no issues with 0.020-0.030 and a 0.008 finish. No squeaking. The hole was true throughout its depth, verified with a 3 jaw inside micrometer.

I am using A9 cutting fluid. Know anything about it? It was recommended on other forums. I don't know anything about it but it seems to work, just smells funny.

 

[eKretz]

It does not need to always be centered. I have run bars above center more times than I can count. On heavier cuts, setting a longer bar on center actually will result in the tool tip running below center once it enters the cut due to the bar flexing down from tool pressure. For light cuts on center is fine if it is working well. You can change the effective geometry of the cutting edge by running a bit above or below center. (Make the tool act more positive or more negative). There are never any set rules on tool positioning. Consider any "rules" as starting points and do what works. Eventually you will learn all the tweaks and what the results of using them are.