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Old 03-23-2020, 02:10 PM
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Default Custom countersink

So, I have a little job in the shop, that, to make things work, we are adapting ‘elevator bolts’ to work. They are basically a flathead bolt, with a square under the head, like a carriage bolt. They are made for bolting scoops to rubber belting for grain elevators and similar soft materials.

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Old 03-23-2020, 02:14 PM
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If you look closely, the underside of the head isn’t flat, it has about a 10degree angle to it.

I’m going to be using these on aluminum, so, I need to have a way to countersink the aluminum for the 10 degree angle.

I could likely sharpen a drill to suit, however I don’t have a lot of large drills over 1”, and this is almost 1.5” diameter.


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Old 03-23-2020, 02:16 PM
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So, I found some 1 1/4” steel and cut a piece off, and chucked it in the old South Bend.

I then turned a 3/4” diameter section for a shank.

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Old 03-23-2020, 02:17 PM
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Turning it around, I faced the end at 10 degrees to match the angle I want.

A little cleanup of rust on the OD and we’re done at the lathe.

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Old 03-23-2020, 02:21 PM
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Over to the mill. I happened to have a 1/2” carbide endmill already in it, so I used it.

I milled a section at the end to half the thickness.

Changing setups around, I set it with the flat now vertical, and tipped up 20 degrees. Why 20?

I going to use a triangular insert. So, 10+20+60=90 degrees.

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Old 03-23-2020, 02:23 PM
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Next I fired up the torches, used some flux and silver solder, and ss’d the insert to the shank.

I’m now letting it air cool before I try it out.

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Old 03-23-2020, 02:31 PM
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After cleaning up the flux. The second picture from the end, shows the step I milled, to the same depth as the insert. This puts the cutting edge on the centre line.

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Old 03-23-2020, 03:38 PM
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Default Custom countersink

So, in use, I found that since I’m going into aluminum, 500 rpm or so worked really well, as it didn’t want to ride up and down on the uneven material.

After that a few strokes with a file to make a square hole for the square on the bolt, and they sit nice and flush.

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  #9  
Old 03-23-2020, 03:40 PM
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Would these be easier?
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  #10  
Old 03-23-2020, 04:32 PM
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Nice!
well done.
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