Drilling into Polyester

[Ron Overs]

Gene,

Drilling into polyester is quite straightforward using twist drills. 
The trick is to have the drill bit very sharp with a lower clearance 
angle than normal, so that it won't bite into the material too 
quickly. I generally sharpen all my twist drills with a lower 
clearance angle than standard. This helps to prevent the drill from 
pulling itself into the work too quickly, with often disastrous 
results. As far as speed and feed rate is concerned, I like to have 
the drill going fairly quickly with a light application pressure. If 
the drill is razer sharp it will fall through the poly like its 
cutting butter. I usually cover the area over the hole to be drilled 
with masking tape before drilling. This helps to prevent any risk of 
perimeter chip-out. When I'm drilling lids for fitting rubber 
buffers, I run a couple of strips of wide masking tape on the panel 
adjacent to where I'm planning to drill, to prevent scratching and 
scuffing of the surface with the Portaline, which is the drilling 
attachment I use for holding the drill square to the panel.

While its easy to drill into polyester with low clearance angle 
drills, I recommend that you drill or grind away a clearance-diameter 
of polyester, down to the substrate, so that the mounting screws 
can't come into contact with the polyester. Preventing the risk of a 
crack developing. Once you've drilled your minor diameter hole for 
the mounting screws, you can cut away the polyester to the substrate 
with a larger drill to ensure that there is good polyester clearance 
from the outside diameter of the screw. This will prevent any risk of 
a nasty stress crack running out from the screw hole at some future 
time. Some caution is required when drilling away the poly to provide 
clearance, since the larger drill, with no material at the drill 
centre for control, can allow the drill to tear into the panel unless 
the feed pressure applied is very light. Another approach might be to 
drill your hole clearance first, being careful not to drill it too 
deep, then following it with the minor diameter drill. I generally 
don't drill the clearance away first, because it increases the risk 
of drilling the minor diameter hole off line. If you've got some 
tungsten carbide grinding balls and a die grinder handy, using these 
can be lot safer way of providing clearance for the screw after 
drilling the minor diameter hole, without risk of tearing up a piece 
of polyester.

Ron O.

>Have a client that wants the 9"x1" hinge installed on the music rack 
>- it originally never had one "
>The piano has a high gloss polyester finish along with some very 
>fancy veneer on the music shelf.
>Drilling into poly makes me a bit nervous - never did it before, 
>expecially in such a visible area of the piano -
>Is there a technique that someone uses to dimple the spot to drill 
>so that the poly will not split, or to prevent the dirll bit from 
>wandering? Accuracy is a must.
>Regards,
>Gene Nelson


-- 
OVERS PIANOS - SYDNEY
    Grand Piano Manufacturers
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Web http://overspianos.com.au
mailto:ron at overspianos.com.au
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