Author: Chris P
Date: 2007-04-20 12:47
The biggest problems with plastics is thermal expansion/contraction which can cause the mechanism to bind between pillars if there's not enough lateral play left (which makes the keywork feel very sloppy), and securing pillars as the internal threads are easier to strip, and also tensile strength - fortunately the only opposing toneholes on oboes are the Eb tonehole and the F vent tonehole and they rarely fracture there.
But the weakest point with all plastic oboes is the middle tenon, and on plastic oboes it's particularly vulnerable to breaking should the oboe get knocked over or sat on.
Injection moulding is alright for mass production, but the rate in which the plastic cools inside the mould or how the plastic is injected can cause weaknesses in certain areas, which is why pro oboes made in plastic are turned like wooden ones.
But machining plastic is made more difficult as plastic doesn't clear like wood which turns to powder during machining - plastic comes off in a continuous strip, and should the waste wrap itself around the joint while turning it can foul the cutter and melt the joint.
The heat generated during turning will cause plastic to expand between the centres which can distort the joint. And as plastic is more flexible than wood, the force applied by the cutter can also bow the joint during turning.
And after the joint is finished, it has to be polished which is more difficult to achieve a uniform gloss as plastic can melt if buffed too hard, and any dings that happen along the way are more difficult to remove.
Then there's cutting the toneholes and bedplaces - a slower speed is needed for the cutters in order not to melt the plastic, and cutting toneholes or undercutting usually kicks up a burr which needs removing.
Former oboe finisher
Howarth of London
1998 - 2010
The opinions I express are my own.
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