Mouth size on wooden jointer

[Caruso]

What size of the mouth opening should you have on a wooden jointer.

I inherited a 19 century wooden jointer that is about 63 cm long, 25". It is made of Birch which is common here. Now the mouth opening is about 6-7 mm. Do I need to close it with an inlay? I rarely work with difficult Wood, usually pine, oak or birch.

 

[D_W]

Double iron?

A tenth of an inch is nice, but not necessary. If the mouth gets big enough that you catch the plane on the ends of noards, you should fit a fillet block in the sole. Other than that is pure preference supposing you use the double iron as it should be used.

 

[Caruso]

Yes it is double iron and the iron is about 5.5 mm thick in the business end. I fitted a fillet block so now the mouth is about 2 mm.

So now these eight are ready for use:

 

[ED65]

I think quite honestly the mouth opening can be very wide, gigantic by modern standards, and the plane can work exactly as you want it to. With a double iron it makes little to no difference to performance if the mouth is 3mm or double that unless you're not using the cap iron the way it's supposed to be used.

 

[Argus]

I think that planes that had their soles jointed and rejointed time after time developed wider mouths as the sole regressed.

Tradtionally I think that the answer was to re-mouth the plane by insetting a fillet (usually Beeech) in front of the mouth so that the edge could be adjusted to the desired gap in front of the blade tip. You sometimes see it on old wooden planes. Obviously the desired gap is what works well for you.

I did it some years ago - it is a bit of precision cutting, but not too difficult.