Thursday, 28 August 2014

Garden Gate Project - Part 4 - Top rail profiling

Template making and bandsawing

We had decided that the top rail would be curved long ago during the projects inception. Originally we had planned for the top side and undersides to be curved but this may have proved to difficult to pull off especially since a lot of the oak had voids in it. We didn't want to chance cutting into voids so the underside of the rail remains straight.
However the top of the rail is going to be curved. A template was duly made. This was done by drawing a grid over the top of the rail at 25mm spacing (approx 1"). The half image was exported out of Sketchup as a PDF file to full size.
Gate top curve template
This produced around 3 pages that were pasted to a scrap of 1/4" plywood using some 3M spraymount. The grid was used simply to join the paper sheets together at the correct spacing

The paper template was then cutout at the bandsaw. Then, using a spokeshave, was smoothed to the line.
The template was positioned on the centre line of the rail and the profile marked out. The template was then flipped so producing a mirror image on the other side of the rail.

The next exercise was cutting the 3" thick chunks of scrap from the top rail. As we had already experienced reaction wood when cutting the tenons a number of relief cuts on 1" spacing were made.
Cutting relief kerfs
The pencil lines were then followed about 1/16" away and the profile was cut. This produced several blocks of oak that were just scrap. Quite honestly I could have cut the profile in one go but I didn't want to get into the reaction wood situation that I had when cutting the tenons.
If we had a long enough template following router bit the plywood template could have been used as a router template. However the longest one we have is around 2.1/2" so the oscillating spindle sander (OSS) was used.

Profile Sanding

Next the profile was sanded to the line with our oscillating spindle sander (also known as a bobbin sander in the UK). The good news was the timber did not have any voids or cracks in it so we got a good stick of wood for the top rail.
Sanding to the line with an OSS

Profile created on the top face
The upper surface of the rail needed a slight angle machining on either side to create water run-off for the inevitable rain we get in the UK. The OSS table was set at 2 degrees and used to create the tapered faces.

Marking out for the taper

Not much of a taper but this
profile will help with water runoff

Then a 1/2" radius was cut on the upper and underside of the top rail to produce a nice roundover on each of the edges.
The round-over cut on the router table

The final process on this piece is to use a smoother plane to clean it up.
Using a #4 to clean up

The finished toprail.
Note the tenons are long at the moment and
will be cut down after the glue up.
There is still some carving of house number
and street name to do on this component before glue up.

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