Holey Screws?

randyjaco

randyjaco

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Last week I found a large box filled socket head cap screws at a yard sale . The price was right, so I snatched them up. When I got home, I took a closer look. Some of the screws had holes drilled through them. The holes are. 04" and . 08" drilled longitudinally through the screws. Anybody know what these might be used for? They are Imperial dimensions and come in multiple configurations.

Thanks
Randy

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Are the holes drilled all the way through? If yes, those are known as vented screws. I have no idea what applications they are actually used in, just remember that Mcmaster sells them.


Quote from Mcmaster:
These screws are drilled through the shaft to vent fluids and gases trapped beneath the screw. Good for vacuum systems.
 
Or if you need bigger jets in your carburetor .
You could pass everything but a gas station.
 
darkzero said:
Are the holes drilled all the way through? If yes, those are known as vented screws. I have no idea what applications they are actually used in, just remember that Mcmaster sells them.
Click to expand...

+1 on use in vacuum systems. Screws used in high and ultra high vacuum systems need to be vented to "outgas" any air or other gasses or vapors in critical vacuum processes. Otherwise they act as virtual leaks and severely extend pump-down time.
 
uncle harry said:
+1 on use in vacuum systems. Screws used in high and ultra high vacuum systems need to be vented to "outgas" any air or other gasses or vapors in critical vacuum processes. Otherwise they act as virtual leaks and severely extend pump-down time.
Click to expand...
That's interested. Would have never thought of that.

BTW- I fixed your post for you.

Ken
 
They also can prevent hydrostatic lock if some foreign fluid happens to be in the receiving hole. That effects the tightening torque as well adding the risk of knocking the bottom out of the hole if the material is thin. I know that happened to my brother with building a FE engine with the rocker studs. A little oil in the bottom and the casting shed a little chunk right into the cylinder, which was found in a few seconds of run time. Ruined a perfectly good piston and had to sleeve that bore. But those were solid studs. So the lesson there is not to have much oil (or anything) in the mounting holes.
 
Randy--before I read responses ---I had your answer in my tool box and in my head----I have made many of these bolts for a different reason---When you have a broken bolt in a hole---I have made these to guide a drill to get a starting hole in the center of the broken bolt even if the broken bolt is broken at an angle-----I have always used the socket head hardened cap screws because the center indent is easy to start drill in center---I have made many in different sized holes and different lengths---once you get the small hole drilled in center you can go to a larger size so your ( easy-out ) will work----I have also made these to run wiring or tubing through----Dave
 
Yeah, they do go all the way through. It was some kind of technician's kit. I wonder what what they were used for?

Dave :it appears that I have a lifetime supply of drill guides

Randy
 
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