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Drilling across a threaded shaft's diameter and/or threaded adapter's diameter

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Scott(GA)

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#1
In the JET Lathes, Mills, Saws, Etc. Forum I posted my efforts at adding a Z-Axis Powerfeed to my JET Milling Machine.

Pretty much the last step of the installation is to drill a 5mm hole through the Powerfeed shaft & Manual Crank Handle adapter and insert a Spring Pin.

I had thought I'd take the adapter off the shaft and drill the hole through it using the Milling Machine but I was concerned that doing so - without something inside the adapter to protect the threads - might cause problems.

The issue is explained in detail in the Powerfeed thread: Here's a link to the actual POST that details things with pictures and such.

As I was having issues finding a bolt that matched the internal threads of the Adapter, I was wondering if drilling through the Adapter without something in the hole would be a mistake.

Scott
 

Dave Paine

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#2
I think the issue is burrs on the inside when the drill exits the top side of the hole. May also get burrs on the bottom side. If I were doing this I would prefer to have a tap to clean up the burrs. If you make a 7/8in x 12 tpi plug and screw this in, you may still get burrs and may have a challenge getting the plug out.

7/8in x 12 tpi is a special thread. Taps exist, just are not cheap.

7/8in x 12 tpi tap at Victor Machinery.
 

markba633csi

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#3
Making a "pseudo-tap" would be a good way to avoid the burr problem- make a threaded shaft and mill a couple slots lengthwise on it, like a tap. Then use it to chase the threads in the adapter after you drill. You may not even need it if you use a nice sharp drill, a dull drill will leave a nasty burr for sure
Mark
 

P. Waller

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#4
There are methods of creating such holes without burrs but few hobby shops would have the equipment for it.
 

derf

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#5
Reach inside with a Dremel and deburr it...
 
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