Thread: What steel for brazed carbide tooling?

Originally Posted by eskimo

...of course if brown tip (yellow and the like included) is not suitable for ferrous metals then its not suitable and is it therefore not a decent joint?

It's funny how real life experience contradicts that (certainly with 15%) ... but why let reality get in the way.


“Those who say it can't be done are usually interrupted by others doing it.” - James Baldwin

Alright! I think I can summarise all this info into that their are a few different approaches with brazing rod choices!

It's a matter of both your skill with brazing and your application in which path you choose. Every machine and cut is different!

If it works for you and it's safe, then thats appropriate.

We might put that one to bed now!

On the other side and back on topic, the base metal choice... It looks like it's pretty varied as well. I think it's a matter of having a go and learning how to use that cutter on your work. Every cutter has it's limitations and sweet spots! If you have problems, we can adjust with different materials, speeds and feeds etc... Because their are a lot of varied opinions, to me their are more solutions to try out!

Bloody top thread though! I learnt a lot and when I get a chance to have a go, I will post up the results.

Thanks everyone for sharing your perspective on it!

Originally Posted by Ben Dono

... sweet spots!

I have seen that also, especially with some of my thinner boring bars ... vibrations/harmonics can sometimes cause a terrible finish, however a small change to one of the the variables (bar projection, cutting depth, cutting speed, etc), can make a big difference to the surface finish.

Originally Posted by Vernonv

I have seen that also, especially with some of my thinner boring bars ... vibrations/harmonics can sometimes cause a terrible finish, however a small change to one of the the variables (bar projection, cutting depth, cutting speed, etc), can make a big difference to the surface finish.

So far I've not had to bore small holes <12mm so I made the decision to use the stoutest boring bars I could. Currently my smallest bar is 10mm square with a small HSS tool bit 4mm diameter held by a grub screw. By changing the tool bit I can thread internally. My 12mm square bar has a piece of a broken carbide tip brazed on to the flat right at the end, ground to shape with a green wheel. Its yet to detach. Its advantage is that I can get right up to a flat bottom hole. I've used whatever bits of steel that came to hand. Somewhere kicking about I have a boring bar that was used on a "Ward 7B" turret. I remember it being used to bore cast iron pulleys 12 or 14 inches diameter with 2.5" or there about spindle holes. The dam thing used to sing something rotten. And I was in the building next door. I used to go in to find out what the noise was. Guys, me included used to complain about the noise. Stan who ran that shop gave me the bar when he made a new one. The new one for all intents was the same as the old one but it never sang.

Just thought I would update this thread - yesterday and today I have been making some boring bars out of old carbide inserts (used and no longer any good). As a test I thought I would make one each using hard braze (Comcoat Blue), 2% silver and 15% silver. I used normal MAP torch and a white silver soldering flux (I think it may be a borax based flux, but don't know as the label is no longer legible). All of the bars were made from 12mm mild steel.

Here are my findings:
Hard braze - was very hard to get the bar and insert up to correct temperature, but with some heat shielding I was able to get it to work. I wouldn't bother to use this method again as it's just not as user friendly as the others.

2% silver - easy to get to temperature, however doesn't wet and flow as well as 15%. Attached is a pic of the 2% silver boring bar and an old gear I bored out. Note that the rough cuts were done with a little over 1mm DOC and the bar, insert and solder performed as required without any issues.

15% silver - very easy to get to temperature and it wetted and flowed very well. This would be my first choice for any future boring bars.


All bars were tested and all performed as expected.