A putter that stays square
when you don’t.
The Square-Locked Pendulum is built around one measurement: how much the face rotates through impact. Perimeter mass, a bonded carbon collar and a head milled from solid take that number down to where a miss still holds its line.
You cannot feel
two degrees.
A face open by two degrees at impact misses a ten-footer by the width of the hole. That is well below what a hand can detect, which is why practice alone never fixes it. The fix has to be in the head: enough resistance to rotation that an off-centre strike does not open the face in the first place.
Milled from solid.
Measured after.
Each head starts as a billet of carbon steel and comes off the machine at 363.7 g. Nothing is cast, so there is no porosity to vary between one head and the next, and every finished head is weighed and logged before it ships. The carbon shaft bonds into a collar cut into the body rather than a hosel welded on top of it.
“We stopped guessing what felt better and started measuring what actually stayed square. Almost everything we believed turned out to be wrong.”
HAPT Golf — design bench, Tokyo
What we make.
Two putters and the kit that fits them. Runs are small and made to order.
Fit it yourself,
on your own floor.
The specification that suits you is the one that holes putts, not the one that sounds right on paper. Six counterweights, two shaft lengths and a torque driver preset to the collar's spec mean you can change the club and putt again in about a minute — without sending anything back to us.
The dimples are
not decoration.
The mark is a golf ball’s surface wrapped onto three solids — the same pattern, at the same scale, that decides how far a ball actually goes. It is the shortest way to say what HAPT Golf is: a company that treats the surface of an object as an engineering problem rather than a finish.
Built in the open.
Every prototype, every measurement, every thing that did not work. Published as it happens on YouTube, Instagram and here.
16:22
YouTubeWe built a rig to measure MOI, and our first number was wrong
A bifilar pendulum, a phone camera at 240fps, and three days of getting a repeatable figure out of it. The error turned out to be in how we were clamping the head.
- Journal
Where the Square-Locked Pendulum came from
The first drawing was a wrapped-forward mass around a hollow centre, sketched to answer one question: how much rotation can we take out before the head becomes unwieldy?
12:04
YouTubeMilling the first head from a solid billet
Four hours of cutting compressed into twelve minutes, including the pass where we took 0.3 mm too much off the sole and started again.