Drilling perspex hatch

[BAtoo]

I am considering installing a chartplotter on the boat. I want it outside & its quite large - Raymarine RC80 - so its a bit big for the bulkhead. The best place seems so far to be on the sliding hatch which is perspex & I would obviously need to drill this & possibly tap it - not wanting nuts protruding below.

Last time I drilled a thin sheet of perspex it shattered o obviously dont want this to happen.

Any tips? Can I tap the holes so no nuts??

 

[paulm299]

Use a sharp bit ( New would be better ) . Drill at slow speed and very little pressure letting the bit do the work . I do not think you could / should tap the perspex unless its more than 1/4 in. thick . Hatch could be made from softer perspex than I'm used to , So I'll bow to more experienced with tapping hatches .
Paul

 

[misterg]

Information on drilling & tapping about half way down this page including details on how to re-grind drill bits to suit.

Andy

 

[Spuddy]

Try sticking a bit of tape down and drilling thro that - stops skidding. Main problem is that the rake angles on standard twist drills are unsuitable; look at the tip and you see the flutes twist down like a spiral staircase to meet the end at, say 45 degrees ( sorry haven't got tables handy) - it should be more like 80 degrees. The answer is to use a fine file to stroke up and adjust that cutting edge .....just the last half mm will do it. There's other stuff you could do but needs a bench grinder. This gives more of a scraping angle and stops digging in. Probably worth clamping down onto firm backing and drilling in to that as well. I have tapped perspex of a decent thickness.

 

[pissativlypossed]

Special drills are available for ceramic tiles, they have a very sharp tip, almost like a pilot drill, they work very well on grp and perspex. All the big DIY stores have them.

 

[srp]

[ QUOTE ]
Drill at slow speed and very little pressure letting the bit do the work . I do not think you could / should tap the acrylic unless its more than 1/4 in. thick . Hatch could be made from softer perspex than I'm used to , So I'll bow to more experienced with tapping hatches .
Paul

[/ QUOTE ]
You should use high tool speeds and low feed rates. Tapping perspex is ok, provided you have drilled the correct size tapping hole. The thread won't be all that strong unless the material is fairly thick - anything less than 3-4mm is not going to be strong enough to prevent it stripping out.
Cast acrylic is easier to machine than the extruded sort (the latter is often sold in diy supermarkets).

 

[LadyInBed]

Maybe an insert would be better instead of tapping (the one bottom right)

 

[BAtoo]

Excellent guys; all the info I need; now just need to pluck up courage!! /forums/images/graemlins/grin.gif /forums/images/graemlins/grin.gif