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NQCairns
16-07-2005, 06:25 PM
I have my new perspex windscreen panels and it would seem I will need to drill and rivet through them as the perspex is but one portion of what holds the frame together ???
Each corner of the frame is riveted where the aluminium channel overlaps in this design although along the straight runs of the channel it is also drilled and riveted into the perspex. It doesnt seem right to me.

Anyway do I run much of a risk of cracking this stuff if I copy what was done before, I dont have any experience in what this plastic can take, probably drilling and poping 12 different spots at 1/8 or possibly a bit larger this time.
Any tips? thanks nq

blaze
16-07-2005, 06:57 PM
Hi Nq
do a trial assembly with masking tape on each side where you will need to drill, assemble the frame and drill the holes very carefully, dismantle and remove the tape and reassemble
cheers
blaze

Tracker
16-07-2005, 07:11 PM
be careful what type of pop rivits you use.s/s with hard mandrels tend to crack perspex.seems ok on lexan.try a offcut first.

bay_firey
17-07-2005, 04:54 AM
NQ
You probably thought of this already, but,
Don't use pop rivets with plain steel mandrels. they rust.
If you are riveting directly onto the perspex you may want to try a small washer to stop the rivet actually pulling up on the perspex

CHRIS_aka_GWH
17-07-2005, 05:10 AM
i recently put a side splash screen on my nomad console but I screw it rather than rivet.

The guys at BIAS (??) the chandlery place at underwood advised me to use these little nylon grommets with a nylon seat underneath - that way the screw is never in contact with the perspex. You could possibly work it with rivets.

Fisher_Boats
17-07-2005, 05:55 AM
NQ,
Blunten your drill bit slightly so the sharp cutting edges don't grab and crack the acrylic. We run them into the concrete to blunten them. Use AA rivets ie alloy rivets with an alloy stem and with a bit of holding your mouth right you should be OK. Just be careful that it's a neat fit where you are going to rivet and it's not going to want to pull the acrylic. Good luck.

Cheers Col

familyman
17-07-2005, 06:36 AM
Nq you could try getting a corner piece from an ally supplier or window place and mitre your frame corners.In regards to assembly and holding the panels possibly could you glue them with sikaflex or similar ie remove the seals if any then fill both sides with sealant therefore not requiring any rivets in perspex to keep it all together,and also no weak points from which cracks WILL start. ::)
cheers jon

NQCairns
17-07-2005, 10:20 AM
Gee! heaps of great advice, if It does crack I will have too keep it a secret 8)

Blaze the panels still have their sticky protective cover so I will keep that on should suffice for as tape for the first assemble. thanks

Thanks Tracker I will stay away from them!

Bay firey, thats a good idea I will see if a washer will work although I may be stuck for the amount of throw I can get so the pop will probably start pulling up inside the plastic :-/.

Chris Thanks, If I dont get away with my first attempt I will adapt your diagram to suit my frame by popping from the frame side into the grommet it should soften the pop rivet pressure outwards on the perspex and channel with the nylon washer[smiley=2thumbsup.gif].

Col thanks for the tips, I hadn't thought of blunting the bit will do that for sure now, will chase up those AA pops I was wondering which would be the most appropriate to use. Great thanks!

Familyman lying in bed last night I had the same thought about using sealant instead of pops and it is certainly an option and I guess stronger, hate masking up and not sure how clean it will stay in the years to come, this screen rebuild is an interim measure before I build another one so It might work till then Thanks.

Thanks all great advice now to digest it all. cheers nq

Tracker
17-07-2005, 02:07 PM
Col,
I will send the propdinger to help you with the drills.He seems to drill into concrete and any thing else when using MY good drills.
cheers Brian
ps (no charge for this service,he's free)

Sportfish_5
17-07-2005, 02:14 PM
Col,
I will send the propdinger to help you with the drills.He seems to drill into concrete and any thing else when using MY good drills.
cheers Brian
ps (no charge for this service,he's free)


LMAO ;D ;D ;D ;D ;D ;D ;D

Burley_Boy
17-07-2005, 04:17 PM
Love the pictorial resource Chris.

I've never thought of blunting the bits so thats a new one for me, I've just used light pressure and as high a speed as you can muster. I have only cracked the stuff when I was rushed and sloppy on stuff that wasn't too important either, but I'm no plastics pro.

Good luck mate.

CHRIS_aka_GWH
17-07-2005, 04:37 PM
somewhere in my engineering education between beers I thought I heard some eminent fob tell me when drilling aluminium & plastics low speed is the go ...

as high speed = high friction = high heat & the material melts onto the bit.
Low speed, nil pressure let the bit find its way.

chris aka Michealangelo

OandaFX
17-07-2005, 05:17 PM
Guys you are on the right track with the blunting thing, but a bit crude. What you are doing is reducing the "rake" of the drill. It is best done on a grinder and you carefully grind away the front edge to 1-2 mm wide. Put on you glasses so you can see what you are doing! SOOOO rather than the cutting edge being an acute angle(less than 90 degrees) it is now a bit wider

http://www.sdplastics.com/polycast.html
have a look at this site. All the good stuff is here on sawing and drills etc.
I know this stuff as I was a Manual arts teacher for 20yrs

good luck

phewy
17-07-2005, 05:32 PM
Good info there phil. ;)

NQCairns
17-07-2005, 06:40 PM
I will try that Phil, I am fair at sharpening bits by hand with a stone on a drill been doing it forever.
So I should flatten the leading edge this will in turn decrease the point to a more exagerated line point and will flatten the drill point angle overall, am I on the right track? - let me know if I am not. Then I drill some concrete to be certain#;D cheers nq

blaze
17-07-2005, 07:05 PM
Had to do some running repairs on a fishing trip once and heated up a knife in the gas barbi and drilled/melted a few holes like that and it worked well
cheers
blaze
ps dont like the price of those trim motors

DR
18-07-2005, 06:40 AM
use a masonary drill bit, has same affect of all described above & you dont have to destroy a good drill bit. make the holes slightly oversize so as rivet expands it does not stretch the hole.
cheers

mickey7
18-07-2005, 04:39 PM
Allway's allow for expansion and drill the hole slightly bigger than the stem of the rivet,use a back up washer as suggested and if you crack the perspex drill a hole at the end of the crack this will stop the crack from migrating further.
mickeyl

Cyclone
20-07-2005, 06:05 AM
Nq spent lots of years working with this stuff only safe way to drill is to get hold of one of those stepped drill bits with the single cutting edge they will never crack it you will get hold of one at Norfast well worth the dollars. Also a bit lost on the rivet thing you but if the rivet is pulling up tight in the plastic it's wrong and will crack if not straight away as soon as it gets some sun on it as this stuff grows heaps when heated. A neat fitting whasher must go over the back of the rivet as someone else said. Good luck. Andrew.

NQCairns
20-07-2005, 06:35 AM
Thanks Fella's I am officially paranoid about copying what they did, I might take it easy and see what happens, after checking it out I have no chance of getting a washer that far up inside the channel and over the rivet end.
Marine sealant as a glue is looking better all the time for the straight sections as much as I hate the sticky crap!.
If use sealant I will have a heap of bare ex-rivet holes around the frame ::) so they will need riveting anyway with clearance holes in plasic.

Thanks again for all the great ideas/tips and info, I now have a reasonable plan of how to attack this job which I clearly wouldn't have had with out this post, brilliant! [smiley=2thumbsup.gif] [smiley=2thumbsup.gif]cheers nq

Burley_Boy
20-07-2005, 09:06 PM
Tis true CHris your memory does not fail you, but with a normal sharp bit at slow speed Its a pretty high chance you'll grab so I'd rather drill with a bit of melting.
The proper way is probably to change the drills sharpening angle as indicated. You have to remember that I do butcher the stuff I work with...

bazz
23-08-2005, 03:16 PM
You can buy drill's for drilling perpex thay have a diferent angle on them same price as h/s drill bit's but better than a blunt one and do not crack the perspex. hope this help's bazz.

Eagle
23-08-2005, 10:42 PM
The worst thing you can do to a drill when trying to "sharpen" it to drill perspex or any plastic is to run it into concrete to dull the point. This should NEVER be done. The corect way is to reshape the cutting edges with a diamond hone or with a grinding wheel as on a bench grinder. If you dont have a grinder, use a diamond hone. Put the drill in a vice positioned horizontal. rotate the drill so one of the cutting lips is vertical. Place the hone against the lip and slide it lengthwise along the axis of the drill. The idea is to grind the sharp lip back to a small flat about 0.5mm wide. Do the same to the other side of the drill. Try and make the two flats the same size. These flats STOP the drill from biting into the plastic and it will now make a perfect hole with NO cracking or chipping and no grabing of the plastic. It's very easy to do, even easier with a bench grinder. Once reshaped in this manner, the drill will NEVER cut steel or aluminium like it originaly did when new. It will have to be reground to the original shape to drill these metals easily and without fear of breaking the drill. If you need more info on this e-mail me.
Eagle