I've been thinking for a while it's about time I put something into the forum - I've certainly taken enough out! But I'd didn't think the cutter would've been of much interest as most folks on here are keen on their power tools - and who can blame them - power tools make the job much easier and faster. But for me, this is a way to relax after work. The only power tools I have are a bandsaw and a 8" tablesaw and an ancient old double action, single arm reciprocating bar sander. Everything else is done with blood sweat and cursing.
I made two of these cutters, one to cut radii, the other to scape out the wood between the cuts. This wee beastie is the scraper and it got it's first use last week! It will cut a minimum diameter of 78mm out to a max of 190mm. If I remove the tool height adjuster it will go down to 52mm diameter.
The tool for both is 4.5mm, made from drill bit shanks. Only because I can get them easily
I've given measurements but the only important one is the distance from the base to the centre of cutter bar. It must be 1/2 your bearing diameter.
Assembled
The body shape was made that way because it was easiest and quickest with the tooling I had (it was made "between jobs" at work - so no mucking about!) It was then drilled and tapped M8 about 15mm deep and then bored 20mm by 5 mm deep to take the spigot on the handle. Then parted off allowing enough material to turn the pivot pin.
Remount the body in the lathe so you can turn the pivot pin (dia 8mm by 20mm long) and counterbore the base deep enough to give the bush a bit of clearance. I went in 3.5mm at 25mm dia.
To drill the holes for the radius bar, adjuster and clamp I used a dividing head mounted in a mill but there is no reason, with a bit of care, that they can't be machined in a drill press. the only important measurement is the distance from the base to the center of the radius bar. It must be 1/2 the diameter of the bearing that will be mounted on the end of the bar. The adjuster and clamp I drilled and tapped M6
The Radius bar
10mm diameter (stainless steel bar) by far to long for what is required. I'll cut it off at the second groove one day which will leave it 190mm long.
First I mounted it in a vice on the mill and machined the flat. Starting 25mm in from the bearing end and making it 95mm long and wide enough to take the 6mm diameter clamp screw.
After machining the flat (or filing it if you don't have a mill) turn it 90 degrees in the vice and clamp it back up with a piece of key steel against the flat. This will hold the bar in the correct position for the next operation.
The tool mounting and adjuster holes
Now back to the lathe - turn the end down to 9mm for the bearing (9 x 24 x 7wide) drill and tap M5 for the tool clamp.
Reposition the bar in the chuck jaws to machine the slot for the adjuster. 130mm in from the bearing. Use your parting tool to machine a groove 2.5 to 3mm deep.
That's the 2 major components.
all the wee clamps and adjusters I'll post tomorrow
