Step fracture problem

[RyanY]

It seems like the biggest setback right now is the creation of large step fractures. They're happening a lot more than I feel like they should and I'm not sure why. What are the main causes of step fractures? I feel like I understand some of them but I must be mistaken or not correctly putting my thoughts into action.

[aaron]

possible causes:
the flake tried to travel across a flat spot, or even a concave valley- flakes like to have a nice convex surface to follow
angle of the blow too steep, too straight in
not hitting hard enough
platform too low
usually it's the first. Before attempting a long flake through a difficult area, use shorter flakes to build convexity.

[RyanY]

Ah. It's probably a combination of not enough convexity and the depth of the platform. My angle of attack doesn't seem steep at all but I think the angle I hold it at in combination with my swing doesn't match up with what I've seen other knappers do so I'm misjudging the angle. A lot of times I either take a big flake or get a big step fracture. Definitely need to focus on building that convexity. Thanks for the insight!

[seminolewind]

One other thing that helped me was switching to a bigger bopper or hammerstone, sometimes it feels like overkill but you got to have that power to knock it completely through.

[papoints]

Ridges ridges ridges.  Without them there is nothing..... lol.

[seminolewind]

For me its the preform not having a convex overall shape. If you have dips or any kind of concavity in your preform you will step  fracture all day long. Only run your flakes along a convex ridge.

In no way am I an expert in fact I just recently figured this out myself !

[iowabow]

Sometimes everything is right but sequence is wrong. Try taking the flake on the thickest side first. This will reduce the mass on the other side thus allowing the flake to travel more smoothly.   A point is more likely to step as the mass reduces. The energy moves the stone rather than propagating a wave. Also as the point reduces the size of the bopper need to change so the point of impact becomes smaller in relationship to the mass or you need to isolate for better flake detachment.

[RyanY]

Thanks guys. I'm definitely going to focus on getting that convexity now. I've been so focused on removing mass and thinning that I've been trying really hard to keep my width to do so but it looks like I need to rethink my strategy. I'm also working with just a couple smaller boppers but I do feel that with practice my technique and versatility with them is steadily increasing.