Thread: What steel for brazed carbide tooling?

Re Flux,
I've always used borax and a drop of water as flux when brazing. It does help to use a very small clamp to hold the carbide tip in place though.

that old flux will work ok Ben...well it does for me at least...i'm still on the jar i bought 10yrs ago

Originally Posted by nearnexus

You also need a green grindstone to rejig the carbide profile afterwards.

Rob, have you tried a diamond wheel? I got a small one from CTC and it does a lovely job of shaping carbide scrapers - much nicer than a green wheel in my (limited) experience.

Very rough, crude and dangerous but I just clamped my small angle grinder down with a fine diamond tile wheel in it for rough shaping that last carbide insert. I went to diamond plates to finish it off.
If I had a green SC wheel on the bench grinder I would have used that. That's next on the list.

Any recommendations on a grade of wheel for heavy grinding of carbide bits? I'm guessing 60 or 80grit. I'm happy to finish them on diamond stones so I don't need to buy two wheels! It's for a standard speed 8" bench grinder.

I have seen a lot of home made jigs on YouTube for sharpening carbide tipped circular saw blade using diamond tile cutting disks, so the idea was not mine to begin with! I don't know that I would recommend it but it got me out of a bind.

I reckon a angle grinder could throw a shattered piece of carbide pretty hard! The tile cutter worked a treat but it was pretty aggressive and grabby!

Originally Posted by eskimo

3% and 5% is rubbish..one should use a minimum of 15% for cu to cu, and they (and 15%) are no good for steel

Really?? That has not been my experience. I've used a lot of 15% for steel and I think I've probably used some 2 or 3% as well (have definitely used 2 or 3 for cu).

I had an old plumber explain it to me a long time ago. I can't say I have had the chance to fully test it but it's holding up so far.

Low silver rods make for the strongest bonds in similar metals and require the most heat to get the rod to run.

High silver rods make for a softer bond and are used in the most different of metals and require the least amount of heat.

Low silver rods (2 and 3%) require the most skill

Higher silver rods flow and wet better and their is less of a chance of pin hole leaks.

Now.....I can't say I can prove any of this as it's passed on information but I can't remember ever having a problem following this advice.

I think when it comes to lathe tooling, everyone's set up and materials are going to be a little different. I think it's going to be a matter of working out which filler rod suits!

I for one am a new Dad and have suddenly learnt the fine old Scottish art of 'tight fistedness'... I'm starting out with 5%

I'm palming this information back to the brains trust! You all know more about it than me!

Ps....I mean no offence to the Scots! I'm half a McKeon!

Try whatever rods you've got and see if they work.

They either do, or they don't.

A GP hard rod is what I use, but you can try anything and see what happens

I've used a cylindrical diamond burr in my pencil die grinder to give the carbide some top relief, and that worked OK.

They are 120 grit, I think.

Diamond should handle carbide OK, but go for a fine grit.

You can actually grind very sharp edges into carbide, and it's really a requirement for very small boring bars to prevent chatter from the overhang.

Unless you are making really large cutters, I can't see how you can use a clamp to locate the carbide.

I generally just grind a flat, allowing for the depth of the carbide, and bronze the carbide fragment in place using gravity to locate it. Use a piece of light gauge steel wire to position it as required.

I don't care how good or bad they look, just so long as they work.

I did actually put up a video touching on this quite a while back:

How to make your own lathe tooling (and weld small metal components) - YouTube

Cheers

Rob

Originally Posted by Vernonv

Really?? That has not been my experience. I've used a lot of 15% for steel and I think I've probably used some 2 or 3% as well (have definitely used 2 or 3 for cu).

SBA102, 105, 115, are not suitable for brazing ferrous metals..reference BOC err I mean CIG and others...!!

if you reckon its okay you can keep using them...but for your own safety may i suggest you check with the the experts ie BOC and all the others

I work on airconditioning systems and for cu to cu anything less than than 15% silver is a definite no no as it does not flow (ie sweat into joint) easily with possible result of poor joint (and is the main reason why I say 2% and 5% are rubbish as I have seen too many PLUMBING leaks with that stuff).... and when working with refrigerants with potential for 700psi I know what I will use...even for brass to copper it is recommended to use SBA245. Apart from the personal safety aspects the cost of refrigerant alone dictates the need for the correct solder.

as for SBA245 it has exceptionally high capillary flow making it very suitable for steel

how ever looking at the book they recommend SBA3402 for carbide tipping of tools.....but SBA245 may be okay as well I'd say

Originally Posted by eskimo

I work on airconditioning systems and for cu to cu anything less than than 15% silver is a definite no no as it does not flow (ie sweat into joint) easily with possible result of poor joint...

Ok, so it is not that it's unsuitable, it just requires more care/skill to get a decent joint.

I'll check the CIG site for the info on use with ferrous metals ... but as I said, it seemed to work well for me. It should also be remembered that we are talking about brazing carbide tips here and not pipe/tube carrying high pressure liquid/gas.

Originally Posted by Vernonv

Ok, so it is not that it's unsuitable, it just requires more care/skill to get a decent joint.

I'll check the CIG site for the info on use with ferrous metals ... but as I said, it seemed to work well for me. It should also be remembered that we are talking about brazing carbide tips here and not pipe/tube carrying high pressure liquid/gas.

yeah but what forces would the carbide be under when machining?...thats way way too hard for me to work out...but I'd reckon it still requires a good joint ???
great to know what sort of forces are involved eh?

Originally Posted by Vernonv

Ok, so it is not that it's unsuitable, it just requires more care/skill to get a decent joint.

Also

I can do that with soft solder...but it'd be poor by comparison to the correct solder...as would the 2, 5 and 15%?

but with 15% you need a better joint.
The forces are more about the design of the bar. after all most tips are held on by a tiny little scew.
I've used soft solder to make a carbide hand scraper.
Why any silver at all? its not like the carbide is going to care if things get a little hot.(assuming you have that much heat of course. the reason I used soft solder on the hand scaper was I didnt have enough heat to use anything else)

Stuart

Originally Posted by eskimo

Also

I can do that with soft solder...but it'd be poor by comparison to the correct solder...as would the 2, 5 and 15%?

Not exactly sure what your point is ... a "decent joint" is one that does the required job. Anything more is just overkill, or is a crutch for lack of care and/or poor skills (and no, that is not directed at anyone).

If you are chasing the ultimate cu/cu joint, maybe look at TIG.

For my money I would be using 15% for brazing carbides, it's cheap and easily obtainable.

Originally Posted by Vernonv

Not exactly sure what your point is ... a "decent joint" is one that does the required job. Anything more is just overkill, or is a crutch for lack of care and/or poor skills (and no, that is not directed at anyone).

If you are chasing the ultimate cu/cu joint, maybe look at TIG.

For my money I would be using 15% for brazing carbides, it's cheap and easily obtainable.

you are correct ...a decent joint is one that does the required job...it must be suitable for the duty??? yes!!?...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?