Which type of chisel should I use to clear up bulk removal?

[Tetsuaiga]

I am trying to hollow out some musical instrument bodies. The work is either cherry, douglas fir sometimes sycamore or maple.

The sides are between 12 and 15mm wide and I have been removing the bulk with forstner bits. I've been using 3/4" firmer chisel to remove the waste between 1 & 2" forstner bit waste holes but only by pushing (also used 1 +1/2 bevel edge too). I'm a bit worried the sides might not take the force of striking with a mallet, but pushing the chisel taking thin slices each time is quite hard work.

I am wondering what the best type of chisel would be to use. I know I could use a router but am not a fan of them for various reasons. Would a mortise chisel be any good? I mostly chisel with the edge of the chisel parallel to the grain, moving straight down, so exactly not how a mortise chisel would work.

Thanks

 

[rxh]

Gouges rather than chisels are normally used for musical instrument hollowing work. What sort of instruments are you working on?

 

[Tetsuaiga]

I'm making a few zithers. In most designs the bottom side meeting is 90 degrees. You can make by either gluing up multiple parts or just shaping one and adding a top. Both are the same in form when finished though.

 

[thick_mike]

I'd use a pig sticker mortise chisel and a mallet. Blade vertical and across the grain. Have something underneath the wood like a towel so that the wood doesn't get bruised by all the whacking!

Way before I got into woodworking I made a Rickenbacker copy which involved hollowing out an ash body in a similar way to how you describe. I didn't know about Forstner bits at the time so I just used a normal Brad point bit in a drill press...it took ages.

I am with you on routers by the way...horrible dangerous things that have a habit of ruining all your hard work!

 

[ED65]

I have been removing the bulk with forstner bits. I've been using 3/4" firmer chisel to remove the waste between 1 & 2" forstner bit waste holes...

What is this "waste between" of which you speak? One of the few bits that are tolerant of the hole overlapping a previous one is Forstner bits, might as well take advantage of it

I am wondering what the best type of chisel would be to use.

The widest one you have. Might sound overly simplistic but you should always use the largest chisel possible for any given job and hogging out material is no time to skimp on width.

But once you overlap your drilled holes you'll reduce the waste needing to be removed to practically nothing, just the paring at the sides and knocking off a few projecting bits in the middle, so you could probably continue to use the chisels you're already using without a bother.

BTW if you need the bottom to be dead flat or nearly so I can highly recommend a chisel router for now. It's worth making a proper hand router or two down the line if you're doing a lot of this kind of work but for now a chisel router will do the job for nearly zero expended effort.

 

[Tetsuaiga]

Thanks for your input everyone.

There is relatively little waste, I haven't overlapped the forstner holes they are just touching each other. So you have some waste that is a bit like a concave mountain inbetween. The instrument body is quite deep though, nearly 2 inches but the bottom is around 4-5mm.

I think i'll see if I can overlap my holes a bit more and also give wider mortise chisel a try.I have been a bit worried having tried mortising before and having the part of my work piece between the mortise and end grain blow out because of the stress, i'm guessing the fact that i will be chiselling into an empty space means there wont be anything like the same stress?

I did also find going along the grain instead of down into it seemed to cut better but seemed a little trickier to maintain the good straight line.

 

[ED65]

On the little mesas of wood left by the Forstners are you paring those away vertically? Not sure if you have the clearance that would allow this but you should try flicking them away with the chisel going horizontal, riding its bevel on the bottom of the recess.

If you don't have enough clearance that's a good use for a dogleg carving chisel or gouge. Ones with a double bend are particularly good for tight quarters.

 

[Tetsuaiga]

Mostly vertically yes. I have concave /\ shapes left over, i will try overlapping the forstner holes so hopefully can reduce them more.

I think I was finding chiselling parallel to the grain was more challenging in terms of controlling an even cut of waste, going in vertically was more accurate but more force required. Perhaps I will have to try using a bit more force via mallet on a test piece and see what happens, like i said i've been a bit worried about breaking the restively thin sides, i'll have to experiment.

 

[whiskywill]

What about a scorp? http://www.pfeiltools.com/en/products/scorp.html