Improvised milling machine

Back working on my bat house mold. Envision a large rectangular sink made of 5/16 thick cast aluminum... I'm 'milling' a shallow slot in the middle with out
a milling machine. A router with a carbide bit actually works (slowly!) as long as I take light cuts and keep it lubed up with stick wax. Running into a problem getting the slots all the way into the corners.
http://www.mysecondbathouse.com/smallmoldpics/mold-slots.jpg
Have already booked some run time at my local rotational molder next month and would like to connect the slots before then. Only real machine shop I can possibly afford (semi retired relative) is not open on my normal days off and my day job is oddly wide a** open. Running out of time and ideas so I'm asking here.
--
William


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William Bagwell wrote:

I suspect that in the olden days such a slot would be cut with a chisel (not a wood chisel), also suspect that would still work today...
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You suspect correctly. The end slots which were already existing in the original cast molds (my mold is a weldment of cast pieces) were modified using the same 'router as mill' technique and the *much* smaller remaining triangles were removed with a long, very sharp, cold chisel.
http://www.mysecondbathouse.com/smallmoldpics/removereversedraft.jpg
Or the whole page if anyone wants to see it, http://www.mysecondbathouse.com/firstmold.html
Searching for a faster way...
--
William

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http://video.pbs.org/video/2284159044/ Watch how quickly he chisels the lettering into the high-carbon sword steel. If you can't/won't buy modern machinery you could fall back to the pre-industrial hand tool skills like learning to shape, harden and temper chisels suited to the work. jsw
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Started watching while I was eating dinner... Did not realize it was so long so might not finish until the weekend. What I did see was quite interesting!
--
William

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On Monday, November 26, 2012 2:11:21 AM UTC-8, William Bagwell wrote:

Like, maybe, an air hammer with a cold chisel tip?
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Might be able to borrow one. Still have the too small compressor problem...
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William

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    Perhaps a metal shaper with a properly shaped bit in it?
    Good Luck,         DoN.
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Have not even *seen* a metal shaper since Vo Tech in 77. Just Googled and was surprised that they are actually sought after today. Well, smaller ones at least... Will keep my eyes out for a deal.
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    Finding a deal is easier with the big ones. Sometimes a shop will give it to you if you get it out of there. For the nice small ones, like 7" stroke (e.g. my Rockwell/Delta/AMMCO one), expect to pay in the vicinity of $1000.00. (At least back when I got mine.) The small ones are the ones which are sought after in general. Most home shops don't have room for the larger ones. but a small one can do some intersting things which are difficult to do on a milling machine or lathe.
    Enjoy,         DoN.
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wrote:

Ive passed on at least (3), 36" shapers, including a Cincinnati that was absolutely mint. All of them were "free".
I managed to find homes for 2 of them, and the third is still parked in the back of the companies parking lot..slowly headed for the center of the earth.
Gunner
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On Fri, 30 Nov 2012 18:53:39 -0500, William Bagwell

I LOVE My Logan shaper!!
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On 26/11/2012 9:05 AM, William Bagwell wrote:

Die grinder + burrs?
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Inadequate air compressor. Would probably be faster than a chisel if I sprung for a few new burrs.
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On 26/11/2012 6:17 PM, William Bagwell wrote:

Do funds allow for a cheapy electric die grinder?
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Even if you had a mill, you probably could not make that cut all the way into the corner.
Some one else suggested using a cold chisel which might be the best option in your situation, although it might not look so pretty.
Other options could be: 1. Cut the sides off, then mill the slots, then screw, weld or braze back together. 2. If you did not mind making the part smaller and had not already milled most of the slot, you could have welded or screwed in sheets of aluminum to raise the flat surface rather than mill the slot. 3. Make a jig to guide a hand-held dremel or die grinder. You could either use an end-cutting bit or an abrasive cutting wheel. It depends which corner you want the radius to be on. 4. Cut out the center section containing the slot. Weld in place a thinner piece to form the slot.
BTW, I assume you know that the vertical edges of the slot should be angled slightly to let the part pop out of the mold more easily.
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On Sun, 25 Nov 2012 21:37:22 -0800, "anorton"

True. Could probably get closer than my router by angling the head.

Too late for that. Originally was two parts and joined (with a backer bar) where I'm now putting the slot.
Out of time, will reply to the rest this evening.
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William

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On Mon, 26 Nov 2012 05:29:44 -0500

Do you have one of the many oscillating/multi-tools? Like this:
http://www.harborfreight.com/variable-speed-multifunction-power-tool-67537.html
These cutters would probably cut aluminum okay (get extras):
http://www.harborfreight.com/1-18-bi-metal-multi-tool-plunge-blade-68912.html
Should look a bit better than chisel work, maybe...
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Hmm, have seen those plugged in and ready to play with at Home Depot. Can not imagine them taking a heavy cut in aluminum, but it might be just the ticket to clean up the mess left by what ever method I end up using.
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On Mon, 26 Nov 2012 19:43:59 -0500, William Bagwell

You'd be surprised. BTW, the single-speed version is on sale for $15 right now, with coupon. You can't afford NOT to have one. I'm sure the blades will cut aluminum (I've cut iron/steel screws with them with no apparent dulling), but if you're not sure, get the bimetal, diamond, or carbide half-moon blade. Keep the swarf from building up in the cut and it cuts extremely fast.
Question: Doesn't the metal bat house get too warm for the critters? And what do you use for condo separations inside?
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