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Cutting inner slots and runoff holes

September 28, 2019 — BarryK

Continuing with construction of solar water distiller prototype #3. Here is the previous post:

Today have cut the inner slots and holes for the runoff tube. The runoff tube is 16mm outside-diameter aluminium, and I posted previously how a 10mm wide slot was cut in it. One end of the tube has to be blocked off, so I purchased a rubber stopper from Clark Rubber:

I chose the 24x16x13mm stopper, and cut off the narrow end and pushed it into the end of the tube:


...I managed to push it in a bit more than shown in the photo, until it was just about flush with the end of the tube.

Cutting the inside slots taught me more about router bits! I used the 4mm straight single-flute bit, and as I was moving the router along, suddenly realised that it was cutting much deeper. The single flute causes more vibration, and although I thought that I had tightened the chuck very well, the bit was gradually working its way out.

What a lesson that was. Fortunately, I spotted what was happening and readjusted the depth of the bit in the chuck, and tightened it up as much as I could.

But then I observed something else: the 4mm bit was cutting a fractionally-over-4mm wide groove. Before, when cutting the outside grooves, I used a Diablo 3.2mm (1/8 inch) straight dual-flute bit, then later ran through the grooves with the 4mm single-flute bit to widen the grooves. That resulted in a pretty well spot-on 4mm width, that the glass fitted into very snuggly.

We are talking about sub-millimetre difference here, but it is still significant. I put the wider cut of the single-flute bit being due to the vibration as it cuts one side then the other.

I did receive advice that dual-flute bits are better, now I know from experience. Though they are expensive. Here is the Diablo 1/8 inch bit:

...unfortunately, there isn't a 4mm (5/32 inch) dual-flute bit. Not at Bunnings anyway.

The steps that I followed today, was to firstly drill the round holes to hold the runoff pipe. I did that before cutting the slots.

I will post a diagram showing exact measurements when the final DIY page is uploaded. Basically, there is a 16mm hole cut 10mm deep on the left side, and cut right through on the right side. To do this, I purchased a set of spade drill bits, at only AU$7.98:

...require the 16mm bit, and later on the 12mm bit, so it was cheaper just to buy the set.

After drilling the holes, the router was then setup and the slots cut, 630mm long, well slightly over, as the glass is 630mm long.

Finally, a check to see that it goes together. Here is the inner sheet of glass and runoff tube inserted:


...just eyeballing it, I think that if I ever make another runoff tube, I will make the slot slightly narrower, down from 10mm to 8mm. But 10mm is OK. The important thing is that the runoff should not be able to splash out -- the design is such that there won't be any splashing anyway. 

Tags: nomad