Thursday, July 1, 2010

100mm Hole in 20mm Al. Baseplate.

Last week I bit the bullet and decided to go ahead and cut the hole for the diff' pump in my base plate. I got the piece of Aluminium plate from a local scrap dealer.(€10). He had mixed cement on it and it took a bit of cleaning with patio cleaner. Its dilute hydrochloric acid I believe. Any way, it attacked the cement well and loosened it after a few goes.
So I decided to use my router and an 8mm straight wood cutting bit. As you can see from the picture I did a test cut in MDF first to see if it would work.
First I drilled a 6mm hole in the MDF and pushed in a pivot made of 6MM brass tube. You can see that sticking out of the wood.
I then carefully measured two points on the base plate of the router one at 102mm dia and the other at 98mm dia. I centre punched them and drilled them out at 6mm. (Don't forget to measure from the correct side of the cutter!). So then I had my pivot point on the router. Easy!
Here is the first pass in the aluminium plate. I oiled the hell out of it. On the cutter and in the channel. I did 8 or 9 pases on one side then flipped it over and needed 4 untill I felt the cutter clear into the groove in the oppisite side. I forgot to mention that the 6mm brass pivot went all the away through the 20mm plate, so it could be used on both sides.
This was a critical point...
As you can see I left 3 tabs holding the plug in place. Aluminium is very sticky to work and I was a bit concerened that at the last minute it would catch the router bit and fuck it all up. The tabs were thin enough to be broken off by hand and sanded back. The process was quite painless, the cutter bit was still sharp at the end. I suppose it took a couple of hours in total.
Note: I firstly cut the 102mm circle to about 3mm depth and then 98mm the rest of the way through. This was to imitate the ISO100 flange design. Just in case I get a gate valve one day...

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