Beginner : Bar for boring head

[hobgobbln]

First, I've been away from the board and my own shop for about a year and its really great to come back and see a lot of the familiar names. Hope everyone has been well.

I've been looking into picking up my first boring head for a project and I've got a newbie question about boring bars.
If a tool is listed as a boring bar with a round shank (be it brazed carbide or indexable), is it safe to assume that the cutting edge will fall on the center line of the shank?

I've never bought/used a real boring bar. I've ground my own for the lathe so far. With the lathe I can adjust my tool holder for proper center height, but from looking at pictures and videos of boring heads I see no such adjustments.

[spro]

Yes the cutting edge is at the center.

[spro]

I hesitated to say that. I "eyeballed" a few things and no way now. The edge must ascribe to the largest circumference of the intended bore. That means the relief angles are correct, or how they are seen by inserts.

[GlennW]

I'd go with spro's first answer as long as they are round shank and not something someone has ground themselves.

But spro's second answer is also correct, as the bar has to be properly aligned when it is installed in the boring head to cut properly.

[EOsteam]

There was a thread on this board that referenced some problems with some imported brazed carbide boring bar sets. I could not bore to a shoulder with my set and didn't know why until that information came out. My set had the issues of noncentered and inappropriate angles on the brazed carbide portion of the bars. Since I don't possess the tooling to alter carbide, a Crterion insert boring bar was purchased and there has been joy in Mudville ever since. Please note that this option is not inexpensive. The bar and inserts that were purchased totaled around $160 and you can spend more than that depending upon what your requirements are.

I have been gravitating away from the imported cutting tools due to issues of quality like this. Although some name brand previously "Made in America" HSS cutting tools that were purchased recently came labeled "Made in India"and have been OK.

HJ

[earlgo]

Hobgobblin:
I had the same issues when I ordered a boring head from Shar's. The kit had several bars with it. The bars were brazed carbide and as a result the edge was not on center. See PDF attached

boring bar unmodifiedrs.pdf

unmodified boring bar

(108.23 KiB) Downloaded 360 times

Having the capability to modify brazed carbide, this is the better bar

boring bar modifiedrs.pdf

modified boring bar

(114.09 KiB) Downloaded 343 times

Incidentally, the edge of the unmodified bars are not sharp due to handling at the factory, so you may need to come up with a way to sharpen them.
Of course the larger the bore the better the unmodified tool will work. That is something you can figure out.
Hope this helps to visualize the problem.

The suggestion that you start with a better bar will save you many headaches later.
--earlgo

[GlennW]

If you are going to use import brazed carbide tooling, it's best to assume that it is like a HSS tool bit in that you will need to grind it in some manner before using it.

[hobgobbln]

I'm glad I asked then because it doesn't sound as cut and dry as it could be. Unfortunately I do not have the proper equipment to modify carbide so it I'll have to take my chances.

Any experience with indexable bars? With the correct size insert for it, are those safe to assume proper alignment?

[John Evans]

I have something like 25 indexable bars ranging from 1/4 shank up to 1" [ya I know WAY too many] my go to favs are the T series triangle style. Cheap inserts and I have some with chipbreakers that have a sharp edge.But,for boring bar use those inserts need to have cutting edge relieve ,actually that applies to any inserts used in boring bars.Also have some that use the C style inserts that work well. Also look for "Bokcam" sp? bars on ebay very easy to re-sharpen due to their design ,made in both HSS and carbide.

[warmstrong1955]

I had the same experience with the Enco brazed carbide bars. Made in China or India....not sure. Dull....maybe on center....maybe not...and some had relief....and some....notso much.
I have managed to use some, after some sharpening. Mostly on the lathe however.
My own hand carved HSS bars did much better.

I have a bunch of indexable carbide bars, like John Evans , from 1/4" to 1". I use those the most.
As far as tool or tooling, which is actually doing the cutting, I do not buy the cheapies. I have not done well with any, from drill bits, HSS, and including carbide & carbide inserts.

Bill

[BadDog]

Regarding insert bars, I've also gone that way for a lot of mine, also from about 1/4" up to 1". But over the last several years I've had an almost complete turnover in my bars (except for the 1") converting to solid carbide bars. Talk about more expensive, and I'm probably one of the cheapest guys on this board. But once I got my first solid carbide bar (for a specific job where I really needed it), I got spoiled and had to have more. There is just no comparison to using those solid carbide bars, but oh how it hurts when those brittle expensive bars break...

All that said, I also frequently use my old school HSS bars, particularly the ones with holes near the end to hold a HSS bit at 90* or 45*. Love those for threading, form bits, and aluminum boring when I don't have the right insert on hand. Those small bars take some weird proprietary expensive inserts at times.

[BadDog]

Oh, and for what it's worth, I've found the cheaper (not necessarily cheapest) boring bar sets are not half bad as long as you have access to a diamond wheel. At first I took mine to my friends shop where he let me use his Baldor Carbide grinder to "fix" the poorly sharpened and profiled carbide chips. Later, I stumbled onto a good deal and bought my own, though it is fairly rarely used now that I have a decent selection of insert tooling and a lathe that can capitalize on the insert tooling. But in between I touched up my brazed insert tooling using a very cheap small diamond wheel setup. Even a Dremel can be used with a little diamond wheel. Or find a friend with a grinder to use.