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Getting the cut angles for an opening cap.

Turned newel post cap.

When fitting a traditionally turned opening cap, it is essential to get the mitre angle correct, when this is not cut correctly the profiles will not intersect at the correct points.

Here we will show the only way I know of getting this correct.

This is the same process for any handrail profile.

Opening cap joint angle.
Opening cap joint angle.

Opening cap size.


The first stage is to determine the size of cap that suits the handrail profile.

This will normally be in about 1 3/4 to 2 times the width of the handrail.


In this instance I will use a cap twice the size of the handrail.


Once you have the cap size, draw a circle the size you wish to use and draw the handrail profile centrally over the circle.

Opening cap size.
Opening cap size.

Draw the cap and handrail profile.

From the over all handrail width, draw lines down until the intersect with the opening cap over all diameter.

Profile over all width.
Profile over all width.

Cap inner radius.

To get the the inner radius of the cap, measure the distance from the widest part of the handrail to the narrowist point of the handrail.
We will call this distance “A”.


Reduce the over all radius by distance “A”.


Draw the inner circle at that radius.


N.B. when working with oval handrail use the edge of the flat on the underside as the narrowist point.

Cap inner radius.
Cap inner radius.

Transfer the handrail width to the cap.

Carry the measurement of the narrowist part of the handrail down to the cap inner circle.

Handrail narrow point.
Handrail narrow point.

Mark the cut angle.

Drawing the cut angle.
Once you have all these lines.

Draw a line from the widest part of the handrail, where it intersects the over all of the opening cap circle, through the intersection of the narrowist point of the handrail, where it intersects the inner cap circle and carry this on to the centre line.


Repeat this on the other side of the cap.


This is the angle at which the cap and the handrail that joins into the cap should be cut.

Cut angle.
Cut angle.

Mark the angle onto the cap.

Mark these angles onto the opening cap and handrail.

The angles may be drawn onto a template, this would normally be done for setting a jig for cutting the cap.

See how to cut the opening cap.


N.B.
Make sure that the opening cap grain is perpendicular the handrail grain. when the grains align the cap is prone to splitting when bolting up.

Mark the cap.
Mark the cap.

The opening cap cut.

Here you can see the opening cap and the handrail cut ready to join to each other.

Opening cap handrail joint.
Opening cap handrail joint.

The opening cap and handrail joined.

With the opening cap and the handrail cut, they can be joined together.

Opening cap handrail jointed.
Opening cap handrail jointed.

Square newel post cap.

Cut angle.

The process for getting the cut angle on a square cap is the same as for the turned cap.

Here I have shown a close up of the joint angle.

Square cap cut angle.
Square cap cut angle.

Cut angle comparison.

Here you can see the difference between the 2 styles of cap.

Cap cut angle comparison.
Cap cut angle comparison.

The finished joints.

The two different cap styles with the joints cut in.

Opening cap square or turned.
Opening cap square or turned.

The next stage.

The next stage is to cut the “V” into the cap, find out how to mark the template and make the jig for cutting the caps.

To see how that is done.

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