Another Experiment

Enough of the humour. Today was the day for cutting the headboard sheet to size.  My experience of cutting plywood isn’t good.  Usually this results in a jagged cut edge caused by ‘tear-out’ from the circular saw blade.  I know why the ‘tear-out’ occurs!  The blade is spinning anti-clockwise and as a result the initial cut is to the underside of the plywood.  the blade cuts in an upward motion resulting in the blade teeth exiting through the top of the sheet.  This can splinter the wood fibres which creates the jagged edge.  There are various methods to avoid this including turning the sheet over or running tape over where the cut will appear.  The joiner at the boatyard would run a razor knife blade down the line of the cut to severe the wood fibres before running the sheet through the big table saw.  I’m trying something different today.

At the local specialist woodworking store I bought a Festool jig.

 

The jig clips onto my Makita Tracksaw guide rails.

This creates a right angle join which secures the rail guide at 90° to the edge of the sheet.  The rail is then clamped to the sheet from underneath.

First time I’ve attempted this so I used my old yellow square to check the angle.

This next part is my experimental cutting method.  Usually you would push the saw forward along the guide rail which means the blade is cutting upwards from the bottom of the sheet.  Today I’m doing it in reverse by pulling the saw backwards.  This way the blade is going down through the top of the sheet.

I’ve only set the blade depth at 2mm so it will just cut the wood fibres on the surface of the plywood sheet.  Such a shallow cut also means the saw shouldn’t bounce around. Then I lowered the badge to cut the rest of the way through the sheet and pushed the saw forwards in the normal direction.  As you can see in this next photo I have a perfect edge on the side I want to keep with ‘tear-out’ on the waste side

However there was a problem with the edge. As you will see in the next photo the rearward cut has an offset to the forwards cut.

To solve this I made all the cuts by drawing the saw backwards multiple times lowering the blade depth 7mm each time.  This solved the problem.

The above photo shows the ‘tear-out’ on the underside of the offcut.  Notice also the difference in colour between the original sheet and my Jarrah stained surface.

My plywood bedhead is now the planned size.  I’m not happy with the status of the stained surface.  It has had three coats but I’m obviously going to need to apply more stain.

Jan has suggested the drawing might be more prominent if I fill the grooves with white paint rather than black.  More research required!