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Bolt torque: steel vs brass washer

Bill D

Diamond
Joined
Apr 1, 2004
Location
Modesto, CA USA
I have a lock bolt that has to be made up tight to hold my Drillpress head in place and not swing. It simply clamps the split casting tight to the column. It is just a steel bolt with a steel washer. My question is what happens if I replace the steel washer with a thick brass washer. Thick enough that it will not bend or flex.
Will it act as a bearing and allow the same torque to tighten the bolt tighter. Being softer will it dig into imperfections and cause more torque to be lost in friction. Or will there be no difference at all? I suppose I could oil the threads but then they may vibrate out.
I know good practice is to install a washer under every nut. Not sure if they need to be under the bolt heads as well.
Bil lD
 
Honestly, in that application I can't imagine that it makes a difference either way. I'd just tighten whatever fastener is there sufficiently to hold and call it good. I personally wouldn't spend two minutes thinking about it!

Now, if you're looking for 'theory', etc, I suppose the brass washer would allow tighter clamping at a given torque. Anything critical I've ever done measures proper tightening by bolt stretch, but certain wheel studs/nuts spec a friction condition for proper torque.
 
I am inclined to think one of each with neversieze between would allow the best you can get without a thrust bearing.
But like mentioned above it likely dosn't matter
 
I have a lock bolt that has to be made up tight to hold my Drillpress head in place and not swing. It simply clamps the split casting tight to the column. It is just a steel bolt with a steel washer. My question is what happens if I replace the steel washer with a thick brass washer. Thick enough that it will not bend or flex.
Will it act as a bearing and allow the same torque to tighten the bolt tighter. Being softer will it dig into imperfections and cause more torque to be lost in friction. Or will there be no difference at all? I suppose I could oil the threads but then they may vibrate out.
I know good practice is to install a washer under every nut. Not sure if they need to be under the bolt heads as well.
Bil lD

There's a patented "diamond shaped gib" trick to get that sort of clamping to round goods to work superbly.

More important short of that is that your casting bore have a more nearly perfect size-match to the column. Otherwise, you are just flexing Cast Iron, it is only in partial contact, even at the most "tight", and it isn't infinitely forgiving of such excursions.

Unless you are trying to mill with it, neither of head nor table should really NEED all that much "anti-rotation" grip, either.

I set the head height on my 1940's Walker-Turner with a separate collar UNDER the head casting that has two stout hollow-cone tipped grub screws in it.

The Alzmetall's head has a four-bolt mating flange to the top of the column. It ain't going NOWHERE.

The table, OTOH, can go half a ton with goods on it and CAN rotate around the column.

I don't fight that at the column. I just rig "field expedient" diagonal brace rails or rods to the base. Result is much like outboard over-arm support braces for a horizontal mill.

In this case, kinda "redneck" and only when needed, since the table height isn't predictable enough to shop-fab anything "pretty" nor permanent.

"Pretty is as pretty does", so it may be ugly to the eye, but it gets the job done to the metal.
 
The brass washer will result in dramatically less clamping force. For the most use a hardened steel washer and lube the threads. BUT it is a cast iron part and you don't want to break it. If it is not clamping, check for lubrication between the pillar and clamp. Check that the clamp is not ridiculously oversize. If so then replace or repair.
 








 
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