Arching a flat bottom plane

[deaf42]

Hey everyone. I'm not new to luthierie but I am new to making archtop instruments. I understand I need thumb planes to do my arching and preferably some arched sole planes. I don't have any but I do have some extra small flat bottom planes. I was wondering if anyone had tried rounding the sole of their plane and if so, what their technique was. My instinct would be to take it to sand paper on tempered glass similar to the way I flatten a sole of a plane. But obviously put a slight curve in it.

Any advice on the matter would be greatly appreciated!

[Oliver A.]

I've thought about doing what you are proposing. Unfortunately, the small, flat bottomed planes that I have don't have thick enough soles to be able to accommodate the amount of curvature required. Your gonna' want a radius of about 4". If it were me, I'd just take a file to the sole if I thought that the plane could handle the amount of inevitable thinning.

Another option that I thought about but haven't tried, is to glue some ebony to the bottom of the plane and then shape the sole into that.

Of course you can also make your own planes from a suitable hardwood. They won't last as long as either cast iron or brass but they will get you started.

[HoGo]

Don't use ebony, I made my own thumbplanes (from any pieces of hardwood I had laying around and blades made of broken kitchen knive, it's pretty easy to make) with ebony soles thinking they will be good but found out they wear quite quickly (curved planes are typically used for rough work on rough surfaces) and even leave dark streaks on the surface of wood.
My solution was plate of cow bone (2x1" 1/8"+ thick) instead of wood. You can glue some brass stock to bottom of plane with epoxy and rivet (or bolt) it in place and then file it to shape. The curvature doesn't need to be perfect and spherical for the plane to work correctly, I started by filing smooth curve along thre planes and then rounded across without measuring. All you need is to grind the blade to match this curvature.

[billhay4]

There are plenty of woods besides ebony that will work well. Any pretty hard wood will work. Hard beech, hard maple, some of the hard exotics. All will avoid the problem of leaving black marks.
And the metals will work well, too, of course.
Bill

[HoGo]

I used beech as well, but that wears even quicker than ebony, even oak wears quickly. Traditionally hornbeam has been used on wooden plane soles, but flat planes wear much less than convex with small point of contact with wood.

[kjbllc]

traditionally dogwood was used for sleigh runners and bobbins, not sure how it would \work for finger plane

[deaf42]

Thanks for all the advice guys I think I'll probably just make a wooden bottom out of some kind of lighter color hardwood beech or maple probably.