Friday, April 17, 2015

Bench troubleshooting

Now that the leg vise is ready to go back on, it is grand time to look into the growing gap issue on the top.

The leg vise normally sit into a let in surface on the front leg, and although I flatten the back of the leg vise, there is rocking on the bed surface. Near the top of the leg, the front maple apron has been re-attached flush with the pine leg. The top is now also flush with the framing members. Whatever gap remains between the vise rear jaw and the top is due to shrinkage movements, mostly.

And sure enough we have a gap left. The leg has twisted a bit, remember it was detaching from the front apron before? She is now tight again, so cannot move any closer. That may have pulled that end a bit lower. The bench framing itself could be out of square a bit, but cannot be by much, everything is tight and square.

There is also some dip at the other end of the leg, the unsupported bit sticking out. Bolting the solid hardwood of the vise to the pine leg will take up much of that gap, but we can do better.

So how much are we talking about?
The bench is currently lying on its side on the cement floor. It is by no means level, but close enough. The legs would be also be pointing lower. All I have to do is to zero my gauge on the front apron.
Why Zeroed? Because it is a lot easier than to try to remember numbers, making it Bob's fool proof

It was about 0.10 degrees off horizontal before I zeroed it. Damn! My cement floor is probably off :-)

The front of the mortise is 0.20 off . And it is not consistent, that is about the worst spot.

The rear of the leg is off even more, 1.30  

As it is visible

The end of the side rail sticking out is off also. 

And finally, the other side of the apron is obviously in line (level with) the long part of the apron.

That only tested the front of the vise/top interface. I did similar checks on the length of the leg.
Note absolute readings here, I'm referencing on too short a surface to get good readings. But nonetheless, they gives me the information I need to quantify, hence confirm, what my eyes are telling me. I now know what to do to address my problems:
- Reduce gap between rear jaw of leg vise and top.
- Make rear vise leg sit without rocking on the inset leg.
- Correct skew of vise's jaws. make parallel with front apron.
Solution, plane the bottom of the inset leg. Pretty well all the worst movements that could have taken places is now done and fairly stabilized, as long as kept in this room. Yes, I will expose fresh surfaces and cause a bit more Relative Humidity transfer but I don't expect much physical movement.
Who could have predicted that construction lumber cup and twist? :-)

Again, I do not have to make it perfectly flat, just flat enough to do the things mentioned above. It only has to accept the back of the similarly made flat enough, leg vise, leg.

Almost there

I'm happy with that, the leg need some breathing room around the top mortise, because that is one big hunk of solid Sugar maple, it moves!...Go figure :-)

In the end I touched up flattening the back of the vise leg and the mating surface on the bench frame, until everything fit right and flush where it count.

This morning I finished fastening the top more securely to the framing, it is now as tight to the frame as I can make it.

I drill deep holes with a Forstner bit then put in a No 8, 2 in screw with a washer in a big enough hole to give room for expansion. There are now 3 such screws on the rear rail. 


That really tighten the top to the frame and took care of the curl of the top in the corner.
Once back up on its feet I checked the hollow on my top and it is now much less. Oh surprise! That is why I wanted to go over the bench before attempting to re-flatten the top.

I used my Shinto rasp on both jaws surfaces to fine tuned the closure. It now hold a piece of paper very tight, I'll call that success. Much improved, and would even be better when I put in a piece of leather on the jaws.

In preparation for the top leveling job, I left the vise slightly below the top.
I will leave it do its stupid wood tricks for about a week, before I plane it flat again.

The tools I used to assessed the problem. To fixed it I used a 1 inch wood chisel with a mallet, as low angle block plane, a jack plane, long jointer etc.

This is one area where using a longer plane, really make fast work of this problem. Unfortunately, in this case we also had to deal with an end grain piece of wood sticking out. It took me more than one plane to tackle it. No problems, I just happen to have pretty well one of everything to throw at it :-)

I'll call this re-hab a success and move on to the next thing on my list, hint you may have spotted the pieces on the bench...

Bob, the bench detective looking for Jessica (from Rogers Rabbit :-) with music from Casablanca in the background.


  1. Bob did you use your big 30" wooden jointer on this?

  2. NO, I stopped at the 24 in Stanley No 8. I wanted the mass to powered thru the end grain :-)