Finally got my finger out and made one of these.
Its a wobble broach for rotary broaching in a lathe. How they work is they have a very slight error introduced into a tool running on spindles between its axis and the axis of the lathe. Then the tool rotates with the workpiece, but each rotation it wobbles by 1degree and forces the cutter in ever so slightly, and pulls itself in at the same time generating a hole the shape of the cutter in the workpiece.
Took a offcut of steel, turned the od 40mm with a flange at one end, and bored it through, and bored it to take a bearing at each end I found in the bearing box orphaned.
Bored a old bike wheelspindle with a 10mm hole one end and cut it to size and faced it off, and centre drilled a dimple in the other end.
Mounted it in a toolholder for my lathe designed to take 40mm boring bar sleeves, and put the wheel spindle in situ just pressed home. All running true, so far so good.
Whittled this out of a piece of stainless bar offcut, you'll have to forgive the lump midway as it came out the chuck and required fettling with a brick hammer afterwards, so I cut a second 20mm surface on it true to the 10mm lefthand end.
20mm because I own ONE 5c collet that happens to be 20mm, and my cheap chinese spindexer takes 5c collets.
I set the spindexer up on my surface grinder (but you could use a mill etc), and slipped a steel shim under the tailstock to introduce 2degree or so of error to the ground surface. Then I just used the markings on the spindexer and counted in 36/6's or 4's depending on which cutter I was making
In situ on the lathe, I drilled a hole slightly smaller than the inhex min diameter, then positioned the cutting bit directly over the hole, then used the tailstock to apply a pushing motion into the back of the spindle.
Voila, one m8 allen head broached into a random bit of scrap..
I'm stunned I managed to get this made in a nights tinkering. I've been procrastinating about making one for far far longer
Its a wobble broach for rotary broaching in a lathe. How they work is they have a very slight error introduced into a tool running on spindles between its axis and the axis of the lathe. Then the tool rotates with the workpiece, but each rotation it wobbles by 1degree and forces the cutter in ever so slightly, and pulls itself in at the same time generating a hole the shape of the cutter in the workpiece.
Took a offcut of steel, turned the od 40mm with a flange at one end, and bored it through, and bored it to take a bearing at each end I found in the bearing box orphaned.
Bored a old bike wheelspindle with a 10mm hole one end and cut it to size and faced it off, and centre drilled a dimple in the other end.
Mounted it in a toolholder for my lathe designed to take 40mm boring bar sleeves, and put the wheel spindle in situ just pressed home. All running true, so far so good.
Whittled this out of a piece of stainless bar offcut, you'll have to forgive the lump midway as it came out the chuck and required fettling with a brick hammer afterwards, so I cut a second 20mm surface on it true to the 10mm lefthand end.
20mm because I own ONE 5c collet that happens to be 20mm, and my cheap chinese spindexer takes 5c collets.
I set the spindexer up on my surface grinder (but you could use a mill etc), and slipped a steel shim under the tailstock to introduce 2degree or so of error to the ground surface. Then I just used the markings on the spindexer and counted in 36/6's or 4's depending on which cutter I was making
In situ on the lathe, I drilled a hole slightly smaller than the inhex min diameter, then positioned the cutting bit directly over the hole, then used the tailstock to apply a pushing motion into the back of the spindle.
Voila, one m8 allen head broached into a random bit of scrap..
I'm stunned I managed to get this made in a nights tinkering. I've been procrastinating about making one for far far longer