[jbtsax]

This has always been a level of frustration for me to form a nice dovetail consistently on every spring. Any advice on tools or techniques would be appreciated.

I currently use a jewler's anvil and a medium flat face "tack hammer" and have trouble hitting the "target" each time. I have tried both heating the end of the spring and cooling in oil before striking and striking the spring untreated.

Thanks.

 

[Henry D]

I use the anvil but, after placing the spring on the anvil, position a piece of square cross section steel stock across the end of the spring so that I have the steel stock just where I want it. I then strike the steel stock with the hammer to flat the spring. I find, for me at least, that it makes it much easier to position the impact on the spring just where I want it. When I try to strike the spring directly with the hammer I frequently miss by a bit (sometimes a lot!).

By filing a slight round edge on the square stock it's also a lot easier to avoid a sharp indentation where the flatted portion of the spring merges with the cylindrical portion. This, in theory, reduces the stress at the point where many springs fail.

 

[abadcliche]

I heat the end to be flattened- must be a nice hot flame to get it low red on just the very tip- if the flame isn't hot enough, the heat has time to travel and remove temper where you don't want it removed. You should be able to hold the spring at the halfway point in your fingers and not feel any change- if you do, you are heating too slowly or too much. Should take less than a second. Hold the spring flat on the anvil with your finger. Use the sharp end of the hammer to get the shape, use the flat end to smooth it out. Less hits overall is better. Strong, steady, sure, carpenter-of-Nazareth-like strokes. Make sure the jewelers anvil is on a solid surface like your vise anvil face. Bench anvil on the carpet of your bench does no good. If the spring end cracks or flakes, cut it off and start over. When done, give the end a tiny buzz on the belt sander to remove the sharp/thin edge so your spring installation pliers have something to hold on to that can take the force. It should look like an old Selmer spring when done.

 

[tictactux]

Place the spring on the anvil, rest a peen hammer's tip (or a small chisel with a blunt tip) on the to-be-dovetailed end and hold it. Use a slightly heavier hammer and hit the chisel instead of the spring. (you also may want to secure the spring with a bit of adhesive tape so that you don't spend the whole day searching for it in the back of the room)

 

[simso]

Heat - Ball peened hammer - Anvil

 

[paulwl]

Amazing amount of technique, special tools, and educated guesswork required for such a small and seemingly simple part.

And yet Norton springs never revolutionized all that. Goes to show how traditional the craft really is.

 

[Gordon (NZ)]

I have made a significant radius on one edge of my anvil (prior to heat treating it.)

For me, that makes a big difference to achieving a decent dovetail.

 

[abadcliche]

Pictures?

 

[simso]

Pictures?

Hammer - Ball peen :mrgreen:

 

[jbtsax]

I think Matt was referring to Gordon's post about the "significant radius on one edge of my anvil".

 

[simso]

Clearly, the humour for some, is lost :faceinpalm:

 

[Gordon (NZ)]

Edge with radius

 

[griff136]

I have made a significant radius on one edge of my anvil (prior to heat treating it.)

For me, that makes a big difference to achieving a decent dovetail.

how so Gordon?

 

[jbtsax]

Thanks Gordon for your helpful post and picture. That makes perfect sense. Can you describe the "heat treating" for those of us who have very little back ground in metallurgy?

 

[abadcliche]

thanks SO much simso- its amazing how much great information is given out for free here. [rolleyes] hehehe

Gordon, thanks for posting a picture.

 

[simso]

Can you describe the "heat treating" for those of us who have very little back ground in metallurgy?

Boots on, pen at the ready

 

[Gordon (NZ)]

how so Gordon?

I place the spring not flat on the anvil, but most of it off the anvil, and the part to be dovetailed resting across that curved area. By using this convex surface I have great control over the shaping of the dovetail.

 

[Gordon (NZ)]

Thanks Gordon for your helpful post and picture. That makes perfect sense. Can you describe the "heat treating" for those of us who have very little back ground in metallurgy?

I just used a rough and ready approach, with rather little control over anything, with a risk of the surface cracking to uselessness...
First, I knew that this particular piece of metal was heat treatable steel, i.e. sufficient carbon (or equivalent) content in the alloy... I bought it as a cheap off-cut from a specialist steel supplier. Probably cheap because of its odd shape.

I used oxy-acetylene to heat the curved surface to cherry red. Most of the rest was not hardened because it never got to cherry red.
I then waved stirred it around in a large bucket of water, to quickly cool it. The fast cooling from cherry red is what makes the affected metal very hard (and also brittle).
The size and shape, (and unhardened interior) meant that brittleness probably won't affect it during use.
However during the rapid cooling the surface shrinks more, and faster than the not-so-hot, and not-so-quickly-cooled interior, so I risked severe splits in it. I struck it lucky, with only slight fracture, and not in an area that mattered. I have used this for a few decades, with barely a mark on that curved area that I use.

As I said, this was a very rough approach that happened to work well this time. If I wanted it done better I would most certainly take it to a specialist heat treatment plant, 3 km away from here. I happen to know enough to know that heat treatment is actually a very complicated area. Such a plant would possibly use case hardening, such as that done with the gears in a gear box. There are a variety of ways to do this, not at my disposal in my workshop.

 

[Gordon (NZ)]

Boots on, pen at the ready