Beginner : Bar for boring head

[hobgobbln]

I ordered a 2" head and R8 shank from Travers. They were having a sale on their house brand and it came with some brazed bars. We'll see how lucky I get.

Thanks for all the info everybody.

[hobgobbln]

The boring head kit I ordered came in today. I took a picture of a boring bar because all 9 in the set are just like this. If I remember the terminology correctly, in a lathe setup this would be considered pretty severe negative rake.

Are the bars meant to be rotated like I have it in use or is it just made that out of whack? Earlgo ground a chip breaker in which gives it a more positive angle. Is that expected to be done when you get these from factory?

I know these are cheap bars but will all nine of them being almost identical I'm questioning if I'm just thinking of it wrong.

[spro]

I am disappointed by what I see. It is almost like the last grinding operation didn't happen. I wasn't aware new tooling was sold like this.

[BadDog]

Based on the way it looks in that pic, the way that bar is constructed, I don't think you can use it in a boring head, though you could use it in a lathe by orienting the top of the carbide chip level and then lowering it to put the point on center. After a suitable sharpening operation that is. Then you just have to remain aware of retaining sufficient relief. You might also be able to rig an eccentric adapter bushing to get things lined up, if the bores in your boring head are sufficiently large.

Also, it looks like you may have a slight downward angle in the photo. You only care about the horizontal line bisecting the main shaft (that goes in the boring head bores). The cutting point needs to be on that line for things to work correctly.

[spro]

"Eccentric Bushing" would be required. Really though, did he not order the size to fit the head? It came as a package and he, or anybody is supposed to true up each cutting edge before either would work. So each one is another work and before I get too deep into this, camera angles can magnify the disappointment. Still it is wrong in my opinion. Stuff happens. I have respect for Travers and if one set goes out like this, they need to know before everyone goes bonkers.

[warmstrong1955]

Wow......I thought the ones I got looked fugly......that pic hurts my eyes....

Like I said....I didn't use mine for boring, but a few times.
I did grind some, and make them usable for odds & ends on the lathe however.
Not a go to tool by any means....

Bill

[hobgobbln]

The boring head takes 1/2" shanks and that's what came with it so an eccentric sleeve is out. I guess I'll either pick up or make a new bar and save these for the lathe. Or a trash can.

Here's a side view of that same bar showing how far off the height is. Explains why they threw them in for free

[warmstrong1955]

Throw 'em away???
Never throw anything away!
Only thing I throw away....is slag & chips.


Get yourself a good one to suit the task at hand, and more good ones after that as you need 'em.
The uglies....they will have purpose later.
(Some of mine did)

Bill

[spro]

+1 to what warmstrong said. If these were free, it is harder to complain and they can be used with different orientation, grinding. Seems like we've seen this before. All you wanted was actual boring bars and now it is a project and a carbide grinder. Reinvent boring bar geometry while you just want to bore with the new head. +2 to what Warmstrong said. This is still useful. It just hasn't been modified yet.
It is possible that this lot is an aberration and Travers would want to know about it before any mods.

[hobgobbln]

I was only joking about throwing them out. I'm sure I'll use them for something.

Thanks everybody

[ccfl]

I'm pretty sure all the generic brazed carbide bars are as unusable as that one. Mine are. The issue is, the chunk of carbide they use is too thick, and if the bar was made to put the edge at C/L and the top at neutral rake, the bar under the carbide would be too thin to survive. Obviously the factory that makes them has never tried to use one.

These are surprisingly affordable especially when compared to something comparable from Kennametal or etc.: http://www.mesatool.com/products/boring-bars/
Pretty sure you can substitute cheaper/easier to find TCMT 21.51/21.52 inserts in those 1/2" bars. Anybody with any insert tooling at all probably already has some of those.

[Harold_V]

I'm pretty sure all the generic brazed carbide bars are as unusable as that one.

Not true. When they are made properly, the cutting edge will be on center, whether the tool requires sharpening, or not. The example shown clearly displays a blank made with the mounting surface on center, so the only way the tip can be on center (in a boring head that holds that size shank) is if the bar is rotated, creating excessive negative rake. All in all, not a good tool.

The issue is, the chunk of carbide they use is too thick, and if the bar was made to put the edge at C/L and the top at neutral rake, the bar under the carbide would be too thin to survive. Obviously the factory that makes them has never tried to use one.

Agreed! However, there's more than one way carbide can be affixed. It need NOT be off center---that's just the fast and easy way to install the tip, without consideration to the fact it creates a less than useable tool (for boring with a boring head).

These are surprisingly affordable especially when compared to something comparable from Kennametal or etc.

That's not a fair comparison, as price is not a good reason to purchase a tool that is not capable of performing the required task. This is a classic example of a case whereby the buyer would be much better served to pay for a more expensive tool that is capable of proper performance.

It should be noted that for larger bores, offset cutting edges become more tolerable. The only other issue to consider, then, is that the feed mechanism will not be linear, albeit with very little error. Again, the larger the bore, the smaller the problem.

I'm at a loss to understand why most applications require carbide, anyway. Boring with a boring head generally demands slower spindle speeds, thus HSS is typically best suited, especially when one considers that boring bars are generally quite long, and encourage chatter. Yes, there are exceptions.

Harold