Timber does play up when cutting.

Timber does play up when cutting.

Started another jewellery box, the fourth. When cutting the mitres at the corners they have again not fitted very nicely. The mites have not square across the width of the timber nor are the mitre faces perfect. I used the SCMS saw again, even swapped to a 80 tooth blade and fastened every piece down when cutting to stop any chance of drift, but I still finished with imperfect corners.

Because there was daylight visible after gluing I decided to put in some splines and I used the Triton biscuit cutter accessory which has a 45% fence and this made some perfect slots at the box corners as per pictures. I have not heard of this operation being performed on a triton before, I can tell Triton users that the operation is a piece of cake!

http://img.photobucket.com/albums/v3...linecutter.jpg

http://img.photobucket.com/albums/v3...um/splines.jpg

I then proceed to cut some material for splines, teak as a contrast to the oak sides. This is where I can see that timber definitely moves because of inbuilt tension when cutting. I took a photograph of the spline being cut from a batten of teak and before cutting off this 4mm slice it can be seen in the picture that the timber has deformed and has raised around 2 or 3mm above its connected side.


http://img.photobucket.com/albums/v3...mitres0011.jpg
I can only assume from this that to obtain perfect mitred corners not only must your tools be in perfect condition but the timber must be in a very peaceful state or machining will most probably be to avail.

What comments against my observations above?

Hi John,

See Wood Borer's recent post on mitred dovetail joints at http://www.woodworkforums.ubeaut.com...itred+dovetail

Hand sawn too :)

Thanks Auld,

I am hoping to get a personal hands on tuition:)

John,
I often experience the same with timber movement. After ripping Euro beech, I also do some light jointing and thicknessing (clean up) and then I let the timber rest for at least 2 days before the final machining, and this avoids any surprises down the road.
Regards
Les
Ps. Great innovation with the Triton BJ.

I wonder if it is the heat generated by machinery when cutting that starts this effect.

Do craftsmen who are only cutting by hand notice timber movement?

Quote:

---

Originally Posted by jow104

Do craftsmen who are only cutting by hand notice timber movement?

---

I am not a craftman, but I do notice timber movement when ripping by hand.

John,
I am led to believe that it is caused by stresses in the timber that is caused during the drying process. Apparently more so for kiln dried timber. By the way the splitter on my tablesaw has saved the day many a time preventing kickback during ripping operations when the timber bends into the blade. It also bends the other way some times. When it bends inwards, one will detect some burning marks caused by the blade.
Regards
Les

Even in my very limited experience, I can state, absolutely, that timber can move substantially when milled.

A straight baulk can transform into two pieces, suitable only for Robin Hood.

My theory is that it mainly happens (gross deformation) to branches. Decades of holding up the weight when relieved and sliced up, they twang apart. This goes for trees that have leaned during their growth, too.

Inside curve gets compressed, outside gets stretched during growth. Cut apart and each goes it's own way.

Makes sense to me.

Hi John.

I don't know if this is relevent but I'll post it anyway.

You never mentioned whether or not your SCMS cut was a bevel cut or not. If so the quality of your machinery also plays a part.

Bevel cuts can be tricky as a lot depends on whether or not the blade drops towards the table the further away from the fence it gets. If it drops, you have a guaranteed gap

I had the same problem with a GMC saw ( ie mitres not square and imperfect faces ) and ended up buying a lock mitre bit for the router to get a decent mitre joint.

Many thanks for views above, I think I will invest in a router mitre bit for the next session.

In the meantime I have got to cut out the four corners of the box to accept a small beading.

The box as you can see is now glued, what do you reckon a rebate bit or a straight 1/2" bit to clean off the edges on the Triton router table.

Alternatively you could make up a shooting board and use a hand plane.
Or make a jig and true the mitres on a disc sander .

with my Ryobi CMS when cutting picture frames for my paintings - that is, until I checked the mitre angle on the thing, and found it was out by a few degrees. The problem was easily solved by lifting and relocating the plastic strip on the front that denotes the mitre angle, using a protractor to get the angle RIGHT this time! I then use a shooting board and plane(just in case!)

yup.. sometimes it's reaction wood from the tree growing on a lean, or supporting a heavy branch, sometimes it's poor or uneven drying.

And sometimes it's just built into the tree. You can be sawing a perfectly straight log with no obvious faults, and the boards will bow up off the mill as you release them :mad: Sure you can flatten them in the drying stack, dry them out and end up with reasonably straight boards, untill you start ripping it down and find that that tension is still in there :o

Sometimes it's just the nature of wood :rolleyes:

Ian

Yes, I did have to resort to both the donkeys ear with plane and sander.

The problem using above setup is getting all lengths to finish up equal and you know what that means if on length is slightly short, you have to do the other one again, and again and again. :)

However things are not working out to badly, I shall most probable fill the inside of one mitre with some glue and sawdust filler,

Photograph of progress so far.

http://img.photobucket.com/albums/v3...um/mitreb1.jpg
.

This jewellery box with secret compartment is nearing completion and I thought you might be interested in its progress with regard to the mechanics of construction.

This picture shows my mortise jig with the base compartment having had two sides of the compartment cut using my router. This method gives me nice clean sides and enables the lid when made to fit tightly and no movement so helps disguise its function. The remainder of the aperture was removed with a fret saw and end cuts made chopping out traditionally with a chisel.

http://img.photobucket.com/albums/v3...tcompart1f.jpg

http://img.photobucket.com/albums/v3.../cutcomp2f.jpg





(The base was been screwed down temporily to stop any drift.)

A brass plate is fitted to the base of the compartment and a tapped hole and M4 nut soldered under. Sorry forgot to take pics of this section.

http://img.photobucket.com/albums/v3.../cutcomp3f.jpg
http://img.photobucket.com/albums/v3.../cutcomp4f.jpg







The lid is then shaped and a knob kindly supplied by Como has a brass bolt fitted which holds down the lid and hopefully disguises its purpose. Pictures below perhaps explain better than words?
http://img.photobucket.com/albums/v3.../cutcomp5f.jpg
http://img.photobucket.com/albums/v3.../cutcomp6f.jpg




The box is awaiting feet and my usual problem of applying a finish.