Custom reservoir question.

OK, I am trying to build a custom reservoir that will connect to the inlet of my pump but I have some questions.

I am going to be connecting the pump inlet to the reservoir through a coupling and I will be drilling two more holes, 1 as an entry point for the water and another as a filling point.

I got some plexiglass at Home Depot and had it cut to the size I want. I now have 6 sides cut specifically to form a box. I will be using Plastic Fusion to attach the pieces together and then put some silicone over the places where the pieces connect to form the box (even though Plastic Fusion is waterproof, I want to make doubly sure that there will be no leaks).

The problem is I can't decide what to use to make perfect holes for my barbs and the coupling that goes over the pump inlet. I have a dremel and I got a cutoff wheel for plastics which should be good enough for making the hole for the coupling (it is hex shaped) but not for the holes for the barbs.

I have been looking all over town and the net for conical drill bits for a dremel which would allow me to start with a small hole and then enlarge it as I keep drilling but I can't find one for the life of me. I want to use my dremel for this because I don't have a speed controlled drill and I am sure the drill would completely melt the plexi at its default speed. Besides, even if I used a regular drill instead of a dremel, I still would need to either use a hole saw (I don't want to as there is too much risk of cracking the plexi) or a conical drill bit anyway.

Any suggestions? I am not really a handy man here. Making the reservoir is not a problem for me but drilling perfectly round holes (and holes the size I want) on plexi is.

I don't see the problem with using a hole saw.

For plastics I use an old fashioned hand drill and a (modern type) spade bit, and get a nice double helix shaving off the cutters. Nothing beats that. Spade bits range from 3/8" to 2".

A dremel will burn plexi.

Just a tip about cutting plexiglass, Black_Paladin: Next time, pick up a "laminate cutter" (looks like a utility knife, but the blade is a scratching hook). This tool will cut through plexi, with multiple passes. Guiding your initial cut with a straightedge will ensure accuracy - if you can cut cardboard with an exacto knife, you can do this and better than the uninspired worker at Home Depot.

a dremil will destroy plexy. at low speed it wouldnt have the power to do what you want, at high it will kill it...

borrow a hand drill and use it slow.

Also, putting a block of wood on each side of the hole and drilling throguh the wood, plexi, and other wood block often make it a cleaner hole. the only problem is its harder to get it exactly where you want it.

Just cut the two blocks to the same size as the plexi, and measure properly. You'll get the hole right where you want it.

Black_Paladin said:

I have been looking all over town and the net for conical drill bits for a dremel which would allow me to start with a small hole and then enlarge it as I keep drilling but I can't find one for the life of me.

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Dremel makes conical grinding bits available in its standard display rack. Also, several companies manufacture steel or carbide carving burs in various conical shapes and sizes, mainly for larger carving tools. At anything like Dremel speeds these'll just burn plastic though. For slow speed drilling of plastics, sheet metal, etc. there are step bits AKA step drills intended for the drill press; they're shaped like an old school pyramid but conical, with increments typically in 1/16ths of inches. The step heights are only 1/8" however so a hole through material thicker than than sheet metal will be stepped.

Honestly, I've had a Dremel with flex shaft suspended over one of my shop work benches for three years now, and used it very very rarely. An old crank-powered hand drill will serve you better for drilling plastic and sheet metal.

In case you missed it: Hole saws are normally used with a pilot bit.

Dremel is a much better choice than a hand drill, the hand drill has to be one of the worst choices, mainly because you cant be solid with it and it only takes a little bit to shatter plexiglass. If your going to use a drill, make sure its a drill press.


Jon

JFettig said:

Dremel is a much better choice than a hand drill, the hand drill has to be one of the worst choices, mainly because you cant be solid with it and it only takes a little bit to shatter plexiglass. If your going to use a drill, make sure its a drill press.


Jon

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My thoughts exactly. For one thing, my drill doesn't have a speed control but my dremel does so I can cut the plexi at slow speeds. I actually practiced cutting on a leftover piece of plexi and the dremel made a relatively good cut.

Second, I wouldn't be near solid with the drill I have drilling plexi and the drill would be all over the place, especially with a holesaw where I have to make sure that the drill stays in the same spot and doesn't wonder all over the place.

Third, I am sure my drill would totally melt the plexi if it didn't crack it like a windshield.

I don't think I want to purchase a drill press just for drilling a couple small holes for one time though. A drill press takes up a crapload of space and costs a ton, doesn't it?

Sean Lindstrom said:

Dremel makes conical grinding bits available in its standard display rack. Also, several companies manufacture steel or carbide carving burs in various conical shapes and sizes, mainly for larger carving tools. At anything like Dremel speeds these'll just burn plastic though. For slow speed drilling of plastics, sheet metal, etc. there are step bits AKA step drills intended for the drill press; they're shaped like an old school pyramid but conical, with increments typically in 1/16ths of inches. The step heights are only 1/8" however so a hole through material thicker than than sheet metal will be stepped.

Honestly, I've had a Dremel with flex shaft suspended over one of my shop work benches for three years now, and used it very very rarely. An old crank-powered hand drill will serve you better for drilling plastic and sheet metal.

In case you missed it: Hole saws are normally used with a pilot bit.

Click to expand...

Thanks for the info Sean. This was very helpful. Unfortunately, I would rather not buy a huge drill press for just drilling a couple holes in plexi.

I wonder if a machine shop or someplace would do this for me cheap if I took my plate of plexi to them??

I'm doing close to the same thing but with acryclic/lucite. I'm using a dremel mutli-purpose cutting bit. Kind of like the drywall one, it's one you can go sideways with. Need to be careful but it'll make a decent enough cut that some glue and silicone can fill.

If yur gonna be making smoot horizontal edges on acrylic or lexan u need either a jig saw or a table saw. Dremel will not make the edges striahgt enough so that water will not leak through yur reservoir. And always with any machine working with plastics, go low rpm cuz if u go fast it will melt the plastics.

By "hand drill" I meant the man-powered "eggbeater" variety, or, better, what's called a "brace". The reason these work so well on brittle stuff is they allow perfect control of speed, pressure, and with practice in the case of the brace - unwavering cuts only bettered by a drill press. Really. I have all the drilling tools in one room and the one I've come to rely on for incidental drilling of plastic is the brace.

A very straight edge can be formed on plexi by cutting it with a steel straightedge and $7 scratcher ("plastic and laminate knife" - Home Depot stocks them), then "lapping" the edge on a sheet of sandpaper.

Any particular grit of sand paper?

When I dont need a 'perfect' cut I dont mind using hole-saws at all. The main problem being the cutout many times will end up resembling the holesaw itself and many times those arent perfectly round to start. It can lead to a slightly rough staggered edge on the cut. It also helps if you begin on one side of the plexi/acrylic with the hole saw and cut roughly 1/2 of the way through then reverse sides using the pilot hole to begin cutting on the other side. This avoids the plexi/acrylic 'chipping out' around the edge of the hole.

I do the same thing with just about every hole I drill in plastics. Start with a small pilot hole and follow up with the larger and final bit. Many times I will use a 1/16" bit for my pilot to avoid the larger bit 'walking'.

Good advice Bugsmasher. I think some people missed that hole saws normally employ a pilot bit.

@sunrunner20. For general truing I use an 80 grit sheet meant for drum (floor) sanding machines. I flop it on a counter or surface plate. These sheets are big. Any place that rents floor sanders will sell them individually, in a range of grits.

Plexi that's been scored and snapped will have a slightly stepped or sloped (but regular) edge. Sawing the piece on 80 grit will true that up. Progressive grits will polish it. To get the edge really clear requires fine powders or polishing pastes, or, with great care, a touch of heat.

ok, 80 grit should be enough then(hopefully I don't have to go any finer than that for just plain solvent welding joints)
And, Don't you have to permanetly avoid alcohol of any sort after you heat the plexi, becuase otherwise it will crack?


whats the flat surface you use when grinding down a straight edge?