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Refurbishing DTH mining drill bits, need tooling suggestions to break carbide with

M

MAFrecycling

Plastic
Joined
May 28, 2020
Hey everyone, new to the forum here. Just a quick introduction of myself...I’ve worked in the drilling and blasting industry for the last 8-9 years now and have actually started my own business recycling scrap mining drill bits. As of late I have been toying with the idea of attempting a process that can refurbish DTH hammer bits. I have already figured out how to remove the carbide buttons that aren’t broken efficiently, but I can’t for the life of me figure out how to remove the broken buttons that are recessed in to the steel. This would essentially be like a tap that broke off a half inch or so inside a hole that you needed to get out, but instead of HSS it’s tungsten carbide.

My best thought is perhaps a PDC Air chisel? The carbide is extremely brittle and breaks apart quite easily when hit against more carbide, so I’m hopeful that a PDC air chisel being harder than the tungsten carbide would hold up and I would be able to chip away the broken pieces until I can clear the hole for a new insert (the holes are 19mm in diameter, so I’ve got some room to play with)

Just wondering if anyone Has any suggestions is all, finding any kind of information on how to work with tungsten carbide is quite scarce so it seems...thanks for any help!
 
Post some pictures of what you are doing. How are the carbide attached, brazed, pressed in, or some other method? The best thing that comes to mind is a tap burner, but I don't know if they work for carbide. What is this PDC air chisel you mention?

What is the value of the body after you get the carbide removed? No use developing a $1000 process for a $500 body.
 
Is the carbide scrap worth saving? Is broken carbide dust worth any money. Will heat and fast cooling break it up. Too hot may affect steel temper adversely but steel can be re-heat treated.
Bill D
 
gbent said:
Post some pictures of what you are doing. How are the carbide attached, brazed, pressed in, or some other method? The best thing that comes to mind is a tap burner, but I don't know if they work for carbide. What is this PDC air chisel you mention?

What is the value of the body after you get the carbide removed? No use developing a $1000 process for a $500 body.
Click to expand...


Imgur: The magic of the Internet
Imgur: The magic of the Internet

The face of the bit is pre drilled and heated up, and then the carbide is simply pressed in, once the steel cools down it constricts around the carbide

PDC is diamond infused carbide, I was basically wondering if using a pneumatic chisel That’s harder than carbide would be an easy way to chip out the broken carbide pieces that I was unsuccessful to remove

These bits new are $2200 and they scrap them when there is a minimum of 3 carbide pieces in a row missing, if I can successfully replace all of the broken pieces (and not just 3 out of 6 like the first picture) I stand to make 50% of new cost in a refurbishing fee

My original business model was simply buying scrap bits off of drilling companies, removing the carbide and selling it is scrap...but being able to refurbish bits for an additional 70-80% life span is much more profitable, and when the bit is scrap again I would be able to remove all of the carbide and sell it as scrap anyway
 
Carbide scrap is what my entire original business model was and is very much worth saving (I’ve sold it as high as $12.50/lb), but I have been approached by the drilling companies I buy scrap bits from and asked if I can refurbish their bits instead...in the one picture I posted I was successful in replacing 3/6 broken pieces, but the pieces of carbide that are too recessed in the steel just don’t want to come out, I’m trying to figure out a way of chipping/breaking/drilling the pieces out without damaging the steel
 
I was thinking hit the carbide with a torch and drip liquid nitrogen onto it. Maybe use a sandblaster ceramic nozzle to contain the heat. Not crazy hot where it glows but under tempering temperatures, say 400F.
What does a tap burner do to carbide?
My dentist uses a mini air jackhammer to clean teeth.
Bill D
 
When you hit carbide against carbide it will shatter quite easily...if the broken recessed piece was hot and I used a room temp carbide punch, would the hot piece shatter much easier? Trying to find information on tungsten properties online is near impossible
 
Tap Disintigrator.

I worked several years ago with a drilling contractor who
bought a disintegrator from a company called Camann industries
to burn those buttons out of some 28" or 30" rock drills.

I believe we used tubular moly electrodes to core out to a
thin shell which then broke out easily.
 
Whatever you do, wear a decent safety shield over your face and decent gloves / long sleeve shirt. I still have a scar from a flying piece of carbide I shattered with a well placed hammer blow.
 
Last edited:
its an EDM system, tap disintegrator system that works. a company out here tried it, left a few heads in holes and quit doing it. the head breaks off at the shoulder, usually the inserts are set in place with silver braze or something like that. the problem is unless your working on 16" plus size bits the value isn't there and you can never get them back to gauge in as tough of condition as factory. A 16" is 5000.00 or so a 6" 600.00 BUT and I can't say it loud enough those bits have a fatigue life span. and if one shanks off down a hole they are not going to be blaming themselves for trying to go cheap
 
https://m.youtube.com/watch?v=4fuTYrplqOI

After petersen mentioned tap Disintegrators I was able to find this video, it literally does the job 100% as I would need

The heads of this bits break off from time to time at what’s called the “shank” anyway, often time it’s the operators fault for having too much down pressure on hard ground.

In the area I’m in, they are drilling through some of the purest iron ore in the world, so pure that the benches in the open pit mine rust, and in some spots, you can even weld to the ground.

Because of how hard the ground is here, they scrap these bits when there are a minimum of 3 buttons in a row missing as this causes too many torque issues on the drill rods, thing is, a brand new from factory bit can get 1 hole sometimes and have 3 buttons missing in a row, and the carbide would be the only reason to scrap the bit as the steel hasn’t even begun to wear out or fatigue. This idea may not be viable for many drilling companies, but given the remoteness of where I am (shipping in new drill bits is extremely expensive) and also given the type of ground being drilled in to, it is most definitely something that the local mines here would give a fighting chance
 
Also not every scrap drill bit is a candidate, I’ve had meetings with a few of the drilling companies I work with already and the consensus seems to be that about 25% of scrap bits are only scrap because of a few missing carbide buttons, that still amount to maybe 40-50 bits a month worth refurbishing, and these drilling companies have all agreed that they would be willing to pay in the neighbourhood of 50% new cost so long as the bits achieve 75% of the meters it got the first time around

I would still be extracting the carbide out of the other 150-200 bits per month no different than I have for the last few years, that alone has been a very lucrative business for me, but refurbishing drill bits would be a double wammy for me, repair THEN extract, I get to diversify my income in to servicing so that I’m not at the mercy of the current scrap carbide price, and I intrigue more of the local drilling companies that I’m not already working with in to dealing with me, effectively sourcing more scrap for myself in the process
 
The area I am in is busier than ever, the government declared the mines in the area essential for the tax revenue they generate, and the iron ore being produced here is quickly being bought from countries with plans to use infrastructure projects to stimulate their economy...the drilling is most certainly not on standby, it’s on overdrive

As far as the economics go, the drill bits I would potentially be refurbishing are $2200-2500 new, and these companies have stated they would pay 50% new cost if they were capable of drilling at least 75% of what the bit did new from factory, if there are only 3 buttons missing, they could be reconditioned in 30 minutes (based off the video I posted showing 2 minutes to remove a broken piece) for a charge of $1100-1250...my business/liability insurance already covers my business model of extracting the carbide to sell off as scrap, this isn’t much of an addition
 
I have no ambition to dive in to a market, no matter how lucrative it is, that will dry up once this pandemic is over...what I’m researching and trying to develop now is a life long market with my local mines so long as I can be efficient, and the finished product can be reliable

I don’t want to discuss anything other than the questions in my original post for that reason...thanks
 
You keep editing your posts with new posts, and I don’t know how to edit mine so I’ll just keep replying

I’ll repeat it again, I’m not dealing with drilling companies that are drilling for oil, I’m dealing with companies in the mining industry that are drilling and blasting, and they are mining some of the highest grade iron ore in the world...iron ore that is surging in demand for countries that are implementing infrastructure projects to stimulate the economy

Where I am is in overdrive, there has been absolutely no slowdown
 
I’ve been in business for 3 years by simply buying the scrap bits from all of these companies as is, extracting the carbide, and then selling the carbide and steel separately

I have 3 years of doing my due diligence, and not once in those 3 years have I been worried about running out of scrap drill bits to work on (Including now)

Now I’m looking at expanding my business to involve repair on the same drill bits I am already getting...if I am successful, I will be able to make money repairing a bit, and then once that bit is scrap beyond repair, I will be able to make money off of it again by extracting the carbide as per my original business model...this fits in to my business model extremely well, and gets me away from relying on the current scrap tungsten market for my profits, as I will be adding service income that won’t fluctuate with world markets

Now, for the last time, I did not make this post to discuss the viability of my business, my first year in business had 100,000 in sales, And my second had 150,000 in sales as a sole proprietor with no employees, and that was just by selling scrap material. I know what I am doing, I know there are risks involved, and quite frankly, you don’t understand the dynamics of the industry in my location like I do...if I go tits up I’ll make a post where you can say you told me so, but until then please stop posting unless you have a productive response to my original question
 
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