Jack and his big mouth

[AndyT]

Over in the thread about transitional planes, I mentioned that I prefer a wooden jack plane with a large mouth, and David Weaver asked about it (viewtopic.php?f=11&t=120484&view=unread#p1324946) and whether it had been altered.

Rather than take that interesting thread further off topic I thought I'd reply in a fresh thread and see if anyone wanted to compare notes.

This is the plane I was talking about:

Made by Preston, with this mark

which according to Mark Rees was between 1889 and 1920 or so.

The plane has been modified a bit - the right hand edge has been replaced with a detachable strip of mahogany, so it can be used to cut wide shallow rebates.

but if you peer down inside the mouth, the surface of the wear has the same appearance as the rest, though it's hard to photograph. (The lighter wood is where I have trimmed the wedge back a bit.)

It hasn't been patched at the mouth. Really heavily worn planes often end up wedge shaped; this one is a little bit lower at the toe than the heel, but only by less than a sixteenth:

Heel:

Toe:

But it's a properly useful plane. You may remember how much work it did while I was building my chest of drawers:

where it was taking the sort of thick shavings I was talking about:

So please consider these old tools carefully and try them out in practice before assuming that they are worn out or useless.

 

[rxh]

I have these two 17" wooden jack planes. The one at the back is by W. Greenslade, Bristol and has the wider mouth. The other one has no visible maker's mark. The are certainly effective for removing a lot of wood quickly.

 

[D_W]

Absolutely effective. I guess I'm wondering what your best guess would be on the mouth size at making.

In my opinion, nothing compares to a wooden jack, whether you push or pull planes - if one works from rough, it'll be doing 90% of the volume and it only needs to be fitted reasonably and sharp. It doesn't need to be perfect.

I think they're generally made with a mouth about an eighth or so when new, though. The wear is often 80 degrees or so, leading to a fast opening of the mouth with even so much as a quarter inch of sole lost (probably another 3/16ths of opening with a loss of 1/4th inch of the sole, perhaps slightly less, but more than another eighth.

I used an ohio tool jack plane for quite a while before I got into making planes and forked out the cash on the few that I found with little wear on them (but still older). The only issue the large mouth ever causes is the plane can catch ends or edges and do substantial damage when you start to get fatigued. Obviously, it can lift bigger chips for tearout, but you can mitigate that, too, with the cap iron or wood selection.

It's much easier for me to find jointers and try planes with little wear, though, than it is jack planes - they were too useful to too many people for too long!

 

[AndyT]

Yes to all the above.
I agree that in general, about an eighth of an inch when new is about right. I have a more modern jack - a 20th century razee style by Emir - which is tighter than that, and it's not really enough for quick work.

 

[thetyreman]

I've been meaning to make an adjustable insert on the mouth of my old jack plane for a while now, mostly just for an experiment, at least you would have the option then of a tight or open mouth and everything in between.

 

[D_W]

If you create an adjustable insert, are you going to do it from the top? If you put something sliding on the sole, you'll have a gap in front that catches the ends/edges of boards.

 

[D_W]

Yes to all the above.
I agree that in general, about an eighth of an inch when new is about right. I have a more modern jack - a 20th century razee style by Emir - which is tighter than that, and it's not really enough for quick work.

When the mouth is too tight for jack work, it feels like a parking brake, as you're probably implying.

I haven't encountered that on a proper older plane, but I made a couple of jack planes starting at zero mouth and then opening up just little bit. Not surprisingly, even though they won't clog with proper making, the amount of work that it takes to bend a chip around a tight angle like that (past the mouth up into the wear) is pretty significant.