New project, I'm in over my head.....

I got the parts welded together and now I have a problem, I was hoping I left the housing thick enough so the welding wouldn't deform it enough to mess up the threads but it did. the threads will start and screw in a ways but they get tight after a turn or so.

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I'm thinking I need to make a tap to clean out the threads where they got deformed, I tried using a 1/2" x 20 tap as a scraper in the weld area to clean up the threads but it didn't work.

I have wires to measure the existing male threads so the question is how much bigger than the thread that I want to fit does the tap need to be? Also do I start with a larger major diameter also? I think I would have to.

I found this thread size on a chart but I didn't find any LH taps or RH either so I guess making one is the only way I'll get this project past this failure point.

2 other concerns that come up now that I can see it all together, my hinge pins on the rudder bracket are going to be under a bit of stress at full power so we'll see if they hold up and I think I am going to need a skeg to protect the prop from debris which means another bit of welding.

So any and all advise for making a large tap would be very welcome. Would mild steel cut the aluminum for a couple uses?
 
bpimm said:
I guess making one is the only way I'll get this project past this failure point.
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....but.....
.............it's so beautiful....
...................the dream cannot die yet......

if the aluminum cylinder did deform from welding it is likely not cylindrical anymore....likely both oval and bell-mouth from the weld shrinkage when cooling. (beautiful welds, by the way....)

bpimm said:
Would mild steel cut the aluminum for a couple uses?
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I bet it would! I agree that making a tap is an interesting solution and worth trying.
If I had to do it, I would make a male thread to the same spec. as the female thread, and then mill some longitudinal slots to produce a flat cutting face.
Ideally, there would also be some relief behind the cutting edge. Four slots minimum, but since you're working with such a large diameter (2-3/8") you could fit any even number to be sure you had good counter forces, perhaps any multiple of 4.

Did you make the thread gauges you talked about in your first post?
If made of steel, maybe those could be re-used as dies.

Wow I would hate to see all your effort not lead to a working result.
-brino
 
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I hope the profanities weren't too bad, if me they would have been.
Before you remove any material could you make some type of die that would reform the cylinder. As brino said chances are its gone out of shape, removing material will make it loose if thats the case.
I agree, beautiful welds.

Greg
 
Wish I could claim the welds, local welding shop. I think he'll be sending me his machine work now so that's cool.

I'll do some measuring and see if I can figure out what happened but even if it's a little loose the orings should still seal.

Brino I was thinking the same thing with milling the cutting edges into the tap, the test threads I made were Aluminum so they wont work. I feel I need to make the tap a few thousandths bigger than the male thread for clearance I just don't have a good feel for how much bigger and I don't want to make them in .001 increments to find out, not that I could hit .001 anyway.

It's not going to die, I'll get there somehow.

Greg, I'll try to measure it out and see if it's out of round or just the weld spot deformed, trying to imagine what a re rounding die would look like.
 
And when they ask, "Where'd you get that really great motor?" what are you going to say? ....
 
This morning I couldn't stay away from the shop and this happened.
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and then this happened.
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the nose cone goes in all the way but the tail section is about a half turn short. I think the edge where the weld is pulled in and is to tight on the oring now, I think I can file the chamfer in that area to get the clearance back but I need a better file for that, all my half round files are way to coarse. But even as it is it should work so full steam ahead again. I'm headed out to Dad's to start the cast of the Kayak today. Still hoping to test it this weekend at the wooden boat festival.

Thanks for all the help and support guys.
 
bpimm said:
Turned the center section down to match the ends and sanded it down to 400 grit, how fine do I have to sand aluminum to get a good polish?

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I used to make spherical aluminum mirrors. I would polish on the lathe using 600 grit wet or dry with WD40 for a lubricant. The WD40 retained the aluminum particles, some of which would oxidize to aluminum oxide. With some pressure, I would get a mirror finish. A self cleaning car wax sich as the old Turtle Wax contains a fine abrasive which would speed the process.
 
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