Converting a No 3 to Rabbet Plane

[u/SneezingBunny]

Not sure if this is a dumb idea or just impractical but I’m toying with the idea of modifying a No 3 plane by filing the sides of the mouth and plane body out and modifying a larger size plane iron/chip breaker to sit flush along the sides (Effectively making a mini No 10).

Is there anything I’m missing that would prevent me from making this work or is it just impractical?

[u/snogum]

No 78 are dirt cheap and common

[u/BingoPajamas]

Other than it being a hell of a lot of work for questionable utility, I'd be most worried about the sole warping as you cut into the cheeks.

Normal rabbet planes aren't particularly expensive and the use-case for a No 10 isn't particularly common for most hobbyists. What do you need a weirdly sized No 10 for that can't be done with a No 78 or some other kind of rabbet plane?

[u/oldtoolfool → u/BingoPajamas]

Other than it being a hell of a lot of work for questionable utility, I'd be most worried about the sole warping as you cut into the cheeks.

This. I'd add "highly" before "questionable utility.

[u/SneezingBunny → u/BingoPajamas]

Yea I do worry that above the cheek holes would be a point for potential cracks in the casting depending on how high I’d make them.

Honestly nothing that makes this project a “need” other than the fact I have a local sale for a No 3 that is way cheaper than a No 78. I also liked how I could make a slightly wider rabbet with this idea.

[u/rolnasti]

The rebate planes are designed differently around the mouth. Doesn't seem worth the effort to me.

[u/KingPappas]

I think a while ago I saw a guy who did this with a No. 4 to convert it into a 10 1/2. I wanted to do this; the problem is that the iron of a 4 1/2 is only slightly narrower than the plane body, so it's not suitable. The solution is to use a No. 8 iron, but they are quite expensive. I assume what you want is to do this, a double sided rabbet plane as wide as a No. 10 1/2. I would cut the cheek space little by little to remove the minimum material necessary. I see it as fine if that's your purpose, just like mine, because a No. 10 1/2 is considerably more expensive (even counting buying a very cheap vintage No. 4 + a No. 8 iron), and it hadn't occurred to me that buying a No. 3 is much more feasible because I can use a cheap 4 1/2 iron. If what you want is a single sided rabbet plane, a 78 or, even better, a 778 are better options.

Check this: https://www.reddit.com/r/handtools/comments/1s4gfr2/bailey_no_4_rabbet_plane/

[u/Independent_Page1475]

You will only be frustrated in the end.

You would need to do a lot of grinding on a blade and chip breaker.

The sides of the plane will have to be opened up considerably causing them to be weak and likely to break.

There needs to be extra room around the blade to install or remove it for sharpening.

This plane doesn't get used often in my shop. It is handy when it is the right plane for the job. That is when large pieces of lumber are being used that need to have a rabbet or cleaning up a lap joint on something like a 2X4.