re- using carbide tips

Hi all .

I have a few old replacable carbide tips floating around the workshop and wondered if anyone has tried to braze them onto a tool shank ?

Seems to be a waste of a carbide tip if they get pegged into the bin because the tip is chipped and could be re- ground after brazing it onto a shank .

The ones i have are made with the chip breaker on one side only and have 3 points (triangle shape ) with the TiNi coating .

IAN

Ian,

I do a lot of work on reclaimed welded shafts which is hard on tooling. I use reground tips all the while to get under the weld.

I'm more or less standardised on the triangular TPUN series and just lick the corners and top on a diamond wheel on a small cutter grinder but do it free hand. Much of the time the tip is still good enough after getting under the weld to finish to a bearing size which has to be nob on.

Never got to the trouble of brazing them as I think that defeats the object and turns a 3 point insert into a one point and so easily scrapped.

Sometimes I can get 9 lives or so from one insert.

John S.

Hi All

It is easy to silver solder a used carbide tip onto on a mild steel shank; a great way to make a small boring bar, or a custom turning tool. The only tricky bit is holding the tip in position while soldering. A piece of stout wire to hold it may help. or mill a pocket in the steel shank.

I use a propane torch and low temp silver solder and have had no problems with overheating. Just let it cool naturally do not quench.

If you have a diamond wheel it is easy to grind the tip in position. (Make sure you grind away all the steel shank first, diamond is crystallised carbon and has an affinity for the carbon in steel and will be quickly worn away) So grind the shank with a normal wheel then the exposed projecting tip with the diamond wheel.

Cheers

John

Hi Ian,

I make tooling brazing carbide tips to pieces of steel. The thing you must do is grind off the TiN coating first ( the flux and braze will not wet this).

Good luck.

Peter.

John,

I continue to read this and fully accept the theory but in real life it doesn't happen.

I fitted one of the cheap ARC grinding wheels when he first started stocking them about 7 years ago.

This one in fact,

I actually bought two because at the price I though they wouldn't last, however it's been on 7 years now in a full time jobbing shop and has sharpend steel, HSS, cobalt and tungsten, all on the same blade, same speed etc.

Now the purists say it won't work, will glaze up, suck all the carbon out of the steel but PLEASE tell me when this is going to happen so I can use the new blade I have paid for.

This damn thing WILL NOT wear out.

Edited By John Stevenson on 18/06/2012 20:44:44

Hi John

I was discussing this with an engineer mate a few days ago. He told a story of an apprentice wrecking 2 large diamond wheels grinding mild steel at the factory he ran. Not low cost import wheels. 9" industrial cup wheels (In a tool grinder with an angle table) serious money to replace. So I know it can happen. I would not be surprised to find that a lot of the cheaper wheals are not in fact natural Diamond. Maybe they are CBN or some other man made concoction; CBN is OK on Steel.

I have a couple of bench grinders set up with silicon carbide wheels of various grades plus the Epoxy Warden I made fitted with a Diamond wheel most of the time.

I guess it is a matter of trial and error. for fine work and a light touch maybe its OK? In any event for hogging into a chunk of steel and moving metal I still prefer to use conventional wheels. I will keep the Diamond for fine HSS and Carbide work. I do transgress and use it to finish my scrapers, but it is only removing a few thou.

Cheers

John

Edited By John McNamara on 19/06/2012 13:42:51

John.. I suspect its more a matter of using (abusing) diamond wheel for soft stuff , not the physical chemistry of diamond and steel. ( plenty of diamond whet stones in use and diamond dressers brazed/soldered into steel holders.).

Will ask a metalagist friend...but I do know soft stuff cloggs wheels of all types...not fun on 36" by 10" wheels I can tell you.

John Mc,

Probably you are correct in that they are not 100% diamond, in the past when decent wheels were over £100 a pop and wages at £40 a week I wouldn't have dared try it but given current pricing it's a no brainer and I have found out it works.

Proves how things move on, recently I have had a big clear out, sold a big slotting machine and scrapped a 10" x 84" TOS lathe which has left the place looking like a WWII bomb site.

Culling this very severly, over 3 tonnes of gear has gone for scrap but I have found stuff I have forgotten about or in cases didn't even know I had.

Amongst this lot were two bench grinders that used a dished green grit wheel for sharpening brazed carbide tooling from ages ago. These were freely give away to two local model engineers who though they were brilliant.

I didn't have the heart to tell them they were abandoned because in light of present technology the green grit wheel is alongside the millstone. Green grit wear away like crazy, it has to when presented with a harder material. Add to this if you examine the edge after grinding thru a glass it looks like the edge of a paving slab and still need honing or finishing on a diamond wheel which is where we came in.

Instead of a green grit for roughing get one of those diamond blades that ARC sells to fit an angle grinder. These will back tunsten off from a brazed tip tool fast than anything out there, you get two sides and mine after 3 years is still on the first side and I often have to take a whole 1/32" off the face of a 20mm square cutter.

Depending on grade you can sometimes get an edge that doesn't need finishing, even if it does it takes less work than a green grit wheel.

All my green grit wheels have now been given away or thrown at next doors cat.

John S.

Edited By John Stevenson on 19/06/2012 20:11:00

Hi all

Thanks for the replies i will hang on to these tips and re use .

Ian

I had a Drill Doctor for a while; they are fitted as standard with a diamond wheel, and are most certainly intended for use on steel.

Regards,

Tony

.".but I do know soft stuff cloggs wheels of all types"

soft like al, bronze ,copper,.pencils ....sadly the "tools only " wheels some times get used for deburring/knotching bar......now ali realy clogs the wheel.EVEN GREEN WHEELS .---sighs---

But imagine dressing 100 thou in 2 thou steps off a 10" thick centerless grinder wheel ! 'cos its loaded up with bronze...at least that was in the line of duty...the" kids" dont mess with the big wheels...