Friday, March 20, 2015

Pushing the limits of a cheap chinese end mill

My friend Jonathan Chalfant has this steady gig with a friend who makes composting toilets. They are a plastic roto-molded affair used in boats and campers. As fabricator Jon is called upon to manufacture the stainless steel hardware and on occasion modify the molds used in the roto-molding process. Modifications were once again deemed necessary so a bit of precision machining was required on one of the tank molds.
Milling the cast aluminum was not a problem but due to its dimensions fitting the mold on my cheap Chinese made end mill really was pushing the limits of its capacity. Sorting through my collection of scrap steel provided us with some 5/16 threaded rod and some C channel that got the mold suitably affixed to the bed of the mill.
The bump that made the indentation for the viewing port on the tank had been relocated and needed to be milled flat.
The Spinning carbide cuts cast aluminum like a hot knife through butter
One precision machined toilet mold

Addendum. Per popular demand here is the Airhead composting toilet ( http://airheadtoilet.com ) made by the mold Jon had to modify. The mold we were working on was the front liquids tank. The little round viewing port needed to be lowered a half inch for better clearance of the top radius.

14 comments:

  1. I like what you did there, I've never done any metal milling, I leave that to my dad. What do the finished toilets looks like? I quite fancy having a composting toilet here at some point.

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    1. Hey Kev I had been eying those little Chinese mills but never got up the courage to spend the 500$ one one. Then a couple years ago I spotted a used one for sale locally at a repair shop for a couple hundred dollars and could not pas it up. It comes in handy for the occasional project.
      Here is the company web page for the composting toilet. http://airheadtoilet.com/
      The part Jon had to relocate is the little round viewing port on the front liquids tank.

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  2. Hi Mike, composting toilets are used alot here in Alaska, mostly off grid

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    1. Hey John, here the big market for them is on sail boats as you are not allowed to flush overboard in the harbors or within ten miles of shore.

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  3. I need one of those for my bus. I'm thinking about buying a chinese stick welder. :) Harbor Freight is all too tempting.

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    1. Yea Mark, the composting toilet would be great for the bus, though I am sure they are not cheap. As for the little stick welders I have one of the Craftsman inverter type I got at Mardens for 80 buck a few years back and even though it is a short duty cycle it gets the job done.

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    1. Hey Mark, I have a plain stick welder (arc). Here it is. I think it cost me just under 80 $ at Mardens 12 yrs ago.
      http://3.bp.blogspot.com/-tNLBaSCcfSU/UHMHr6GLw8I/AAAAAAAAAM4/h8W63g_lWrc/s1600/IMGP7747.JPG
      Good for mending trailers and mowers and the like.
      A MIG would be better and easier to use. Preferably the gas shield type rather than the flux core. But those run more expensive 350 to 2000$ range. Harbor Freight out by the Maine Mall has both stick and MIG for under 100 $ right now. The MIG they offer at that price is flux core wire. Comparable to my stick welder. Splatters a lot more than a gas shield MIG. If I had the choice today I would choose the MIG over the stick. For 100$ it is cheap learning and you will have a bunch of fun with it. Ultimately I am looking to buy a TIG welder. I have used Jon's big Miller, and TIG has it over all others in terms of control and ease. The learning curve is easier with the new inverter type TIG welders as they have all kinds of do-dads that make initial strike much easier and all your welds look like a neat row of dimes. This is the one I am looking at. http://www.ebay.com/itm/231499183822?

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  5. Nice. I've been wanting a welder ever since leaving the transfer station. I taught myself how to stick weld there and really enjoyed it. I've been talking to my wife about teaching the boys (and girl, if she wants) to weld and I think I might do a cheap one from Harbor Freight. I've never used a mig, but I've heard it's easier/better. Not sure what the best is to start the kids on. I certainly do miss Mardens. My uncle goes to the one in Presque Isle and finds some crazy deals. And I guess if I get a welder, I have to get a cutting torch set, too. ;)

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    1. Mark, with the MIG you can set the feed rate on the wire and it allows you to keep a neat pace, and for me it gives not as many fits and starts as with a stick. I have only used the gas shield type which gives a bit nicer results than the flux core type. The flux core MIG (no gas shield) is more akin to a stick welder. I have a small portable oxy-acetilene rig and been trying to teach myself gas welding and have had various degrees of success and failure mostly due to its small capacity. A proper cutting torch would be a blast but you need some big tanks for that, though for detail work a proper plasma cutter would be better and they are not so expensive.

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  6. I never had a composting toilet. I know people use them in situations where plumbing isn't available. Seems like they would smell kind of funky.

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    1. Harry, Yes, that's is kind of where I was on the whole idea as well. But as I understand it the principle on this one is separation of liquids and solids and evaporation. To that end it has a fan that keeps positive pressure going the right way and vents it outside the dwelling via a hose. And so everything dries out to a powder. More details on the web page for the product.

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  7. Nice, looks a might prickly, but it's got the right man on it!

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    1. Yes, as usual the set up took longer then the actual milling.

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