Can a carbide boring bar be broken and appear to look okay?

[kb0thn]

Hi Guys,

I run an Ultradex 3/8" E06M SCLPR2 carbide boring bar in a Mazak CNC lathe boring some small features in 304 SS.

E06M SCLPR2 | Ø3/8" CARBIDE BORING BAR - ARCH Cutting Tools

Carbide .375" x 6" Boring Bar .460" Min Bore to hold a Positive CPMT 21.51 at -5° Lead (Right Hand) Coolant Thru

www.archcuttingtools.com

Very nice stable tools and I've been running them for years with perfect results.

In the middle of a production run I got a part w chatter on the bored surface. Insert was a bit chipped, so I replaced it. Next part had massive chatter and blew the corner off the insert. I took the tool all the way out, replaced insert screw, reloaded the bar in its holder, reset the tool on x and z (no real change in offsets. Maybe a few 0.0001") ... and it did the same. Blew up insert and of course horrible finished. Tried this a few more times before giving up.

Bought identical brand new tool and bores are back to being wonderful. This bar is years newer and x only changed by 0.0015". z was about 0.04" different.

My question is do these bars break and not appear to be broken. A friend has suggested that the braze between the steel(?) head and the carbide bar may have cracked?

I guess I am getting to be a better CNC machinist because my bars are dying of old age and not getting murdered smashing into things...?!? :-)

Thanks,

-Jim

 

[William Lynn]

Since a new bar fixed the issue, either the braze joint failed or the bar is cracked. If the bar looks good, I'd say the braze joint failed.

 

[kb0thn]

Since a new bar fixed the issue, either the braze joint failed or the bar is cracked. If the bar looks good, I'd say the braze joint failed.

Same friend who suggested the braze being the problem also pondered if he could throw it in his heat treating oven and reflow it. Any thoughts on that? As far as I know it is a normal atmosphere oven.

Thanks

 

[memphisjed]

Same friend who suggested the braze being the problem also pondered if he could throw it in his heat treating oven and reflow it. Any thoughts on that? As far as I know it is a normal atmosphere oven.

Thanks

It is a piece of scrap now. Either reflow works and you get a few more years out of tool, or you have the same scrap you have now. If ever a perfect risk reward ratio this is it.

 

[CarbideBob]

If the carbide cracked you would know. The end falls off on the next cut.
Braze failure is common. This braze joint is hard to get 100% right. IMO Ultradex is as good as any on the planet.
Here you get chatter and terrible size control but the bar still kind of cuts as what braze left in the cone sort of acts like a spring.
Sometimes this can be fixed with a torch, some pressure and silver solder.
The right fix is heat up. Knock off the head. Sandblast all clean. Rebraze that cone filled correctly.
Have no idea what U-dex would charge to do such. Would hope they may do it for free as a product failure.
Bob
(U-dex and I am oil and water enemies going a long time back since thier formation so no love)

 

[gregormarwick]

I've had a good few carbide tools fail at the braze, never had one fail and stay attached...

I'd wager if the bar is very old that the insert seat is worn and the insert has movement under load. High frequency squealing/chatter is a pretty good indicator of this.

 

[michiganbuck]

$200+ boring bar might be worth repairing.
At the Big shop, we would send broken boring bars and the like to Stegman Tooling Troy Michigan, I don't know if they still do such work. but Stegman could restore just about anything to like new..might cost half the new price or what. *Easy contact on the first page of the Stegman website it will take 5 minutes to ask if they want the job of repairing. (good to send it with your favorite Insert, a used one is OK) You might say Buck recommended Stegman.

Stegman Tool

This shop offers the same. I know nothing about their quality but they advertise BB repair, and they are only 50 miles away).

Indexable Tool Repair - NTM

Instead of buying brand new tools, discover how NTM can restore your damaged or worn tools to perfect condition.

ntminc.com

 

[GregSY]

Your problem went away...so stop chasing it.

There probably is - there must be - a technical explanation but it's more expedient to decree the holder as very, very wicked and throw it out. If it bothers you to make such a decree, you could hire Tim to do so at your bequest.

 

[Zeuserdoo]

I'd wager if the bar is very old that the insert seat is worn and the insert has movement under load. High frequency squealing/chatter is a pretty good indicator of this.

I've seen this exact thing happen before, especially on bars that are holding size 2 inserts and smaller. The walls around the insert seat deform over time after tens of thousands of loading and unloading cycles. If you've worn out the pocket on a boring bar, I'd say you got your money's worth out of that bar, and then some.

 

[gmach10]

Would you be able to "Ring" test it? I'm thinking a solid carbide bar versus one with a crack would sound way different.

 

[kb0thn]

I ended up sending it back to Ultradex / ARCH for repair. I was told the carbide would be reused and they would put a new head on it. They just sent a new bar. Which was slightly annoying because the carbide portion had been cut shorter to fit in the CNC lathe without massive stickout.

 

[4GSR]

......................was slightly annoying because the carbide portion had been cut shorter to fit in the CNC lathe without massive stickout.

WHAT??? A 3/8" x 6" lg bar, you can't chock up on it and leave 2" sticking out the holder? Any less than this is a waste of a carbide bar IMO. Maybe I'm used to letting them stick out 4" and run.

 

[kb0thn]

WHAT??? A 3/8" x 6" lg bar, you can't chock up on it and leave 2" sticking out the holder? Any less than this is a waste of a carbide bar IMO. Maybe I'm used to letting them stick out 4" and run.

On a sub spindle lathe? With bars facing both directions? Good thing is not your money I'm wasting.

 

[4GSR]

On a sub spindle lathe? With bars facing both directions? Good thing is not your money I'm wasting.

Yeah, good point there. Watched a guy break off a carbide bar just to use on a opposed spindle lathe. Made a mess out of that bar. Wound up waiting for the correct length bar to come in.

 

[???]

Its a damn sight cheaper to replace a bar than have the head come off down inside a hole and cause some major damage when the head and bar get caught up inside the hole.