Client brought in an old Western Field 12ga pump shotgun for cleaning and inspection. It was his grandfather’s gun, and it hadn’t been shot for decades. It is a Savage 520 made for Montgomery Ward long ago.
The firing pin was broken at its shoulder. Found replacement place at Numrich. I took the old broken pin for a practice run, trying to solder it back together, with a spline made out spring still. It was sort of re-tipping with different spin.
I went ahead to drill holes in the pin body. I thought it was a walk in the park. To my surprise, my HSS drill bit could hardly make a dent in the plain looking old steel. I went through 3 drill bits lubricated with oil. They all went dull in less than a minute. I re-sharpen them at least twice. It didn’t go anywhere even I annealed the steel. I finally gave up on drilling and ended up cutting slots with hacksaw for the spline to go in. Apparently the steel was harder than HSS in the drill bits, but softer than high carbon steel in the saw blade, at least so after annealing.
What sort of steel can this be? Could it be so hard because of the decades long work hardening by the hammer? BTW, I have a drill doctor drill bit sharpener. It came quite handy for such occasion. -TL
It sounds like it’s case hardened. Sometimes you need to use a burr in a Foredom/Dremel tool to break through the case hardening in order to drill. Cobalt bits hold up better on these types of jobs, but even they’re not perfect.
By the way, how do you like the drill doctor? Jeff
Question Follow Up
I was trying to drill into where the pin broke off, which was inside the bulk of the steel, so I doubt case hardening was the problem. Funny was that annealing didn’t help. Now I’m wondering whether it was HSS that was used to make the pin. I have heard mixed reviews on Cobalt bits. I think some cheap diamond bits could be better way to get through casing.
I do like my drill doctor. I got it used from Ebay for $50. It did put keen edges back on my bits on more than a few occasions. Arguably $50 can buy quite a few of cheap new bits. But being able to get back to the “fight” without waiting for new bits is priceless. I consider it a good investment. -TL
Answer
Tip for the Drill Dr.
When I sharpen my bits I usually index them one ahead of the 118 (towards the +) so that the relief angle is correct. Without that, the drills wouldn’t cut even though they were quite sharp. The issue was that the drill was rubbing and needs just a bit of clearance to allow the point to start in. DC
Question Follow Up
Absolutely. That’s the relief angle of the bit. It’s a bit difficult to describe with words. But it is quite simple if you see the graphical explanation online. My drill doctor is an old model. I don’t have the notches to adjust the relief angle. The machine has a pair of claws to guide drill bit’s position in the chuck. They work well for larger (1/8″ or bigger) bits, but not so much for smaller bits. I just eyeball it for smaller bits.
More positive relief angle makes the bit cut more aggressively, but it will go dull faster if the material is hard. Negative relief angle simple doesn’t cut. Slightly positive is the ticket.
I had been looking at the new models. But I was too cheap to put down over $100 while I could get the old ones for $50. -TL
Answer
The firing pin could be an oil hardened steel that is hard. It could be that it work hardened where the old pin pounded against the broken tip piece….that isn’t uncommon. Ken
