Capping pin design

TheBitterEnd

TheBitterEnd

Well-known member
I am finding my current capping pin design somewhat unsatisfactory and plan to make some hardened silver steel ones. I was wondering what other people do at the business end of their pins by way of a suitable shape for engaging the rim of the cap?

Also has anyone seen an original Hilti firing mechanism in the flesh, what does the cap striking part of that look like?
 
Brains

Brains

Well-known member
A friend made some by using a fine cutting disc to cut a cross in the end of a silver steel rod, leaving 4 teeth on the rim to act as firing pins.
Other options gave included grining the tip off a phillips screwdriver then drilling a countersink in the end to leave 4 pins again, or cutting a slot in the end of a flat head screwdriver to leave 2 prongs.
With a persistent misfire drill out the hole with an old masonry bit on hammer action, the bad cap will drill out and or go
 
TheBitterEnd

TheBitterEnd

Well-known member
Thanks all, very helpful. Looking at the videos I think I have been making the cuts in the end too deep. I'll have a mess about to see how shallow I can make them.
 
PeteHall

PeteHall

Moderator
I used to use one of (the other) Pete Hall's hardened steel sets, but after that gave up, I've opted for a much more lightweight alternative, which to date has been very effective and is dead easy to replace if it gets bent.

I simply use a length of M8 threaded bar and grind up the end to give a double pin which seems to work very well (I attach this to my bolt driver with a studding connector). The cut is about 2mm deep.

I have tried to atach an image of what it looks like, but not sure if this will work as it's not there in the preview...

 

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Rob

Rob

Well-known member
I too use (the other) Pete Hall's product, and it's very good.

I should point out though that there seem to be two different designs of cap. Rim or Centre fire mechanism. This selection will change the ideal pin design.
 
TheBitterEnd

TheBitterEnd

Well-known member
Pete Hall - I have been using 8mm threaded rod and I just use a small round file on the end to create two "prongs". This works well but the problem I find is that the prongs don't last very long before becoming deformed and then they stop firing the cap, hence the plan to make a harder pin.
 
PeteHall

PeteHall

Moderator
TheBitterEnd said:
I have been using 8mm threaded rod and I just use a small round file on the end to create two "prongs". This works well but the problem I find is that the prongs don't last very long before becoming deformed and then they stop firing the cap, hence the plan to make a harder pin.
Click to expand...

Fair enough.

My experience has been the other way around, I started out using a hardened steel one (assuming threaded bar would be crap), then it got very slightly bent and started jamming in the hole, so I just made one out of some threaded bar and haven't had any trouble since. They don't last very long, but are easy enough to re-sharpen or replace.

I do make some effort to harden the tip by heating and rapidly cooling, but no idea how successful this is...


 
bograt

bograt

Active member
I wonder if case hardening the 'business end' is worth trying?, heat it to cherry red and quench in engine oil (old sump oil is O.K.)
 
SamT

SamT

Moderator
I use threaded bar, and just make up a few pins at a time, as they do bend eventually.

Handle is made up of a nut glued into a 13mm socket. attached to a 1/2" extension bar. You can of course then extend it to various lengths need be with more extension bars to suit.

640856-3-piece-1-2-drive-wobble-extension-set.jpg
 
Simon Wilson

Simon Wilson

New member
I know around half a dozen people who have ended up in hospital using capping rods. A great deal has been learned about the design of capping rods and Pete Hall's rods are based on a lot of combined experience. Silver steel with a hardened and tempered tip ground to a slightly hollow chisel point has proved to be the best. Also, lightweight rods are dangerous. The rod needs to be at least a metre long and needs to have some mass, I guess around a couple of kilos.
 
SamT

SamT

Moderator
Simon Wilson said:
I know around half a dozen people who have ended up in hospital using capping rods.
Click to expand...

indeed.

Lightweight rods are dangerous.
Click to expand...

agreed - i've been through the early days, I was just using M8 bolts years ago - nearly shot myself in the head once.  {shudder}
However, flyrock, shards, shrapnel from the brass casing are much more of a danger, and thus a decent capping mat, large enough and preferably of conveyor belt material is a must.

The rod needs to be at least a metre long and needs to have some mass, I guess around a couple of kilos.
Click to expand...

Disagree - in many situations, a meter long bar would not even fit the space.  Extendable handles to suit are order of the day.
  A bit of mass is vital, but a couple of kilos is a bit over kill IMHO
 
Dave Tyson

Dave Tyson

Member
bograt said:
I wonder if case hardening the 'business end' is worth trying?, heat it to cherry red and quench in engine oil (old sump oil is O.K.)
Click to expand...
I don't think this will achieve much in the way of case hardening. You need to keep the steel hot and in contact with a carbon rich source for at least 5 min to get a thin case hardened surface. Traditionally you used 'Kasenite' and dipped the part in it while red-hot and then continued to heat it for about 5 min before quenching.

Dave
 
Simon Wilson

Simon Wilson

New member
SamT said:
Simon Wilson said:
The rod needs to be at least a metre long and needs to have some mass, I guess around a couple of kilos.
Click to expand...

Disagree - in many situations, a meter long bar would not even fit the space.  Extendable handles to suit are order of the day.
  A bit of mass is vital, but a couple of kilos is a bit over kill IMHO
Click to expand...

Yes, I just measured mine and it is 860mm. I carefully plan my capping and drill the holes in such a way that I can get the rod in and swing the hammer from as safe a place as possible. I can't be bothered weighing it but certainly the mass has to be sufficient to stop the rod being a missile.
 
PeteHall

PeteHall

Moderator
Simon Wilson said:
I know around half a dozen people who have ended up in hospital using capping rods. A great deal has been learned about the design of capping rods and Pete Hall's rods are based on a lot of combined experience. Silver steel with a hardened and tempered tip ground to a slightly hollow chisel point has proved to be the best. Also, lightweight rods are dangerous. The rod needs to be at least a metre long and needs to have some mass, I guess around a couple of kilos.
Click to expand...

Capping is dangerous.

There are things you can do to limit the danger.

I have taken the view that the greatest danger is from shattered rock and bits of brass casings, hence the need for a decent sized piece of conveyor belt rubber over the area.

Presumably a heavy capping rod is to add some inertia to prevent the rod firing back out. I mitigate this by attaching the pin to a rubber handled bolt driver, which I hold firmly with my hand through the strap. I always try to make sure I am not in line with the hole, though sometimes this is unavoidable. I am happy that this limits the chance of injury from the pin to an "acceptable" level.
I've not seen anybody else using this technique and perhaps there is a good reason? So far, it seems very effective and I have not had any concerns or near misses, but I don't do that much capping.

I would also think the length of the bar will need to depend on the cave situation. What is the reasoning for 1m long? Is this just to add weight, or to get further away from the action?
 
AR

AR

Well-known member
Dave Tyson said:
bograt said:
I wonder if case hardening the 'business end' is worth trying?, heat it to cherry red and quench in engine oil (old sump oil is O.K.)
Click to expand...
I don't think this will achieve much in the way of case hardening. You need to keep the steel hot and in contact with a carbon rich source for at least 5 min to get a thin case hardened surface. Traditionally you used 'Kasenite' and dipped the part in it while red-hot and then continued to heat it for about 5 min before quenching.

Dave
Click to expand...

If you do want to try hardening the tip of a steel rod by quenching/tempering then really, you need to know what grade of steel you're using so that you can find out what's the best form of heat treatment. Some steels may be fine with heating the end to a cherry red heat then quenching in oil for shock restant hardening, but another steel may perform best with a water quench followed by re-heating to a specific colour. Heat treat a steel in a manner inappropriate for that alloy and it may shatter in use....
 
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