Trimming light covers...part 2

Simon · 05-23-05, 04:22 PM

Thanks for all the advice on the previous post guys. I have yet to drill the holes in the covers but hopefully I will know to do it carefully.
Just thought you'd like to see my solution to trimming the light covers to fit.
It's a cheap belt sander clamped to the workbench.
The belt sander was only £29.00 (I've got a number of other jobs around the house to do with it as well) and clamped down tight, it makes the perfect toolo for sanding down the covers.
I put masking tape on the covers and trimmed it with a razor blade so it was flush with the edge. I then positioned the light cover and drew freehand where it needed trimming.
Cutting very carefully, it's possible to get a really nice smooth edge and as long as you don't hold the cover in one place for too long, won't butcher the cover.
Simon

Simon · 05-23-05, 04:23 PM

Another pic

Tim Kay · 05-23-05, 04:27 PM

"Necessity, the mother of invention" [img]/ubbthreads/images/graemlins/wink.gif[/img]

Simon, I like it [img]/ubbthreads/images/graemlins/grin.gif[/img]

Julian West · 05-24-05, 06:35 AM

Simon,

Neat idea! Glad you got the results you wanted. I'm just about to start trimming my light covers & windows so I'll be using a similar technique.

Let us know how you get on with the drilling.!

Fwiw, I'm considering using Stainless steel M4 'button heads' & rubber 'top hat' fixings. I figured the rubber nuts would allow for a small amount of movement in the covers.

Anyone else considered these?

Simon · 05-24-05, 07:06 AM

Julian,

What do you mean by top hat fixings? any pics? where to buy?

Simon

Julian West · 05-24-05, 07:36 AM

Hi Simon,

They look like top hats, & are made of rubber with a threaded brass insert in the top. They are much like a rivnut.

As the screw is tightened in the hat, it compresses the length & expands the diameter.

I'll try & take a picture & post.

cheers!

Ian Anderson · 05-24-05, 07:44 AM

Question

Why do you trim first then drill the holes - surely a crack is more likely to happen if the hole is nearer the edge of the material?

That said has anyone tried the "mirror" drill bits for drilling the perspex / plexiglass?

Ian

Bill Bayard · 05-24-05, 08:01 AM

Since the subject of drilling plexiglas has been raised, what type of drill bit will you be using?

I need to replace a light cover and my side windows, but I am torn between trying a "stepped" bit, or a bit with "small teeth" at the outside edge(recommended to me by a custom car guy)
Sorry for the vague description, but I can't remember the specific names of each type of bit.
Any thoughts would be appreciated.

Bill

Simon · 05-24-05, 08:46 AM

Without trimming the covers to fit the recesses, it would be very difficult to see exactly where to drill the holes. It could mean that you end up sanding back too close to a hole that's already been drilled.

Neal · 05-24-05, 10:57 AM

Simon,
Great minds think alike! I did exactly the same this you are doing. I laid the cover in position and used painters masking tape to outline the impression in the body. I then sanded away, slowly bringing this size inline with the recess.

I then placed the cover in the recess and taped it down. Then, using full taper Plexiglas bit, I drilled location holes for all the screws. I then removed the cover and drilled the holes in the clip to an appropriate size for nutserts. I finished off by putting sticky back foam tape around the perimeter.

Plex bits can be found here...
http://www.aircraftspruce.com/catalo...plexidrill.php

dave harris · 05-25-05, 12:13 AM

Bill B. - re: drilling.

If you have a "TAP Plastics" store near you, they sell the correct drill bits for all types of plastics. I don't know if they have a web site or not (have'nt looked as ones just around the corner from me!).

Anyway - if you want one, let me know and I'll be happy to pick one up and send it to you - (it may take a couple of weeks as I'm leaving for Europe for 2 weeks of business this Friday).

Cheers

John W · 05-31-05, 12:01 PM

The rubber Top hat fixings are called well-nuts, and are commonly used for holding plastics, such as motorcycle screens in place.

Don't buy them from a bike shop though as they will charge dealer prices. Margnor Fasteners in Guildford, Surrey supplied mine (I use them along with stainless bolts and penny washers to hold the wings on the caterham).