How to evenly taper liner material, like on a split spring whittler

[Jason Fry]

You may be familiar with the split spring whittlers that have the liner in the middle that's tapered down to a point. Any tips on how to do that? I'm making a frame handled knife where the frame is made of three layers of 410 stainless liner material. I plan on fileworking the two outside layers, but was thinking it might be cool if I tapered the middle one to give the knife a tapered tang look. Any tips for tapering a liner so that it's flat, but wedge shaped?

 

[Geoff Flato]

A surface grinder with a sine plate would be the easiest and most accurate way I could think of

 

[stezann]

Scribe your end lines on the edges of your stock, then go slowly on the grinder (or flat disk grinder) holding the stuff with a nice magnet

 

[javand]

A surface grinder with a sine plate would be the easiest and most accurate way I could think of

We wish. Usuaully this is way to thin for any reasonable holding on a surface grinder, and you're working from like 0.020" to zero, at least, in the case of a tapered spacer for a whittler.

How thick is the material you're using for this? Most standard pole, or import fine line permanent magnet chucks wont hold 410 below 1/16 enough to do any work with. Although a good electro magnet with a strong controller can.



I'd recommend roughing one side of the material (80 grit on the disc grinder maybe, you don't want deep gouges, but you need a sticky surface) and then super gluing to a larger plate. Then you can surface grind, or fly cut the other side. Just take extremely light cuts and don't let the metal get hot. Super glue is the most versatile tool in our arsenal, I have no idea how I'd live without it. Once you're done, just heat the back side of the bar you glued to, with a torch and the part will fall off. May have to straighten a bit from stress or heat warp, but nbd.

Bear in mind that in this case, you don't have to cut both sides, just calculate the angle you want and make the cut on one side. This isn't like a blade that you have to flip and keep holes oriented. If this is your center spacer piece, you can cut the holes slightly oversized, pin or glue it together, then you can clean up the profile making the edges square to the angle. Honestly if you can cut the pin holes later, unless you're talking about a much more extreme angle than I'm envisioning, you can probably just clamp all 3 pieces together, set it up reasonably level, and drill the pin holes. If they're going to be peened/domed, you'll never have to worry about the angle being 1 degree off of square. Hell, most of us can't drill that square to begin with, either the drills, tables, or technique induce more error than that.


Let me know if that makes sense?

 

[Geoff Flato]

I'm not saying it'd be easy, but it'd beat trying to do it on the belt grinder.
I do exactly as you described when something doesn't want to cooperate on the grinder. A good chuck makes a huge difference though.

 

[Jason Fry]

Thanks, that's kind of what I was thinking. I was planning on doing it on the belt grinder, but hadn't thought of gluing the liner to a piece of regular steel. I figure it'll be a matter of just grinding it down and flattening. The tiny angle we're talking about, I agree, shouldn't mess with the hole alignment. I don't have a surface grinder. I do have a fly cutter or end mill that may be an option if I can't just get it to work on the grinder.

 

[olymon]

You are probably not going to fly cut anything that thin. Lots of load on the leading edge and it'll pop off. Glue and grind.

 

[Jason Fry]

I tend to think so as well, that the fly cutter would be less likely to work.

 

[javand]

Face mill, large diameter, sharp end mill, whatever you've got. You could even do it, although tediously, with a 1/2" end-mill.


One thing you can do is make a fixture plate with holes along the side for clamping bars (still use glue regardless), and clamp one end, cut till you get close to the clamp, then clamp the already cut side, cut further. Etc.


That's how I do integral liner/bolsters with very thin liners (down to 0.035" sometimes, below that it's very difficult) without flood coolant on one of my mills. Usually runnning 1.5-2" diameter end mills if I'm not doing double bolsters. With flood I can go faster, and take them thinner if I wanted, but without it, usually once I get below about 0.0450 if I'm not being careful they'll heat up enough to let the super glue release, and the ends of the liners will warp into the cutter making a mess.