Round column mill lock-down torque

[slow-poke]

I have an old round column mill with the three vertical bolts to lock the head to the column.

I don't really have a sense for how much horizontal force is applied during a heavy cut.

Every time I lock the head in place, I wonder if I'm over doing it or if it's just about right. I have never had an issue with the head moving, it's just a bit of a PITA cranking down the three bolts and always wondering. I just Put a torque wrench on to get a sense of how much torque I typically use and looks to be about 25 ft-lbs.

If I could get away with less, it would be less of a hassle, so how tight are guys/gals going when you tighten up the head in ft-lbs?

 

[DavidR8]

I only torque two of them; the lower one is easy because the previous owner welded a handle to the nut and the middle because it has a handle on it from the factory.
I've only had it move once when I had not done one of them up.

 

[Bi11Hudson]

A "redneck" shadetree rule of thumb is two snaps and a grunt. There are some caveats to that, if the metal is cast iron, I would go only one snap. For aluminium, maybe only the grunt.

.

 

[RJSakowski]

I don't torque my RF30 clone to a specific value. I just checked it and it looks like I torque to 45 - 50 lb-ft. I have been doing that forty years with no problems. I always tighten the middle nut first, then the bottom and finally the top. I do so because when the head is loose there is a slight gap and it is possible to cant the head slightly which will affect tram. I also take all three nuts to snug, then tighten all three to a mid torque and finally I tighten all three to final torque.

 

[T Bredehoft]

I'm glad I've got a square column mill. Hand tight on two little levers.

 

[C-Bag]

Don’t mean to complicate things but saying round column mill does not convey bolt size. My 80’s vintage RF30 only has two locking bolts and they look to be around 5/8” size so the limiting factor is the socket wrench that came with it. The bolts can easily take 50-90 ftlbs but that wrench is lucky to let me do 40-50lbs if I get after it. There is much variance in the number of bolts and size of those bolts. It’s pretty easy to match the size bolt with recommended torque. But I’ll bet nobody here torques them, just goes to “that’s about right” and gets on with it.

A member here posted many mods to his round column and amongst them was making his locking bolts into cam locks. If I ever get around to it that’s what I’d like to copy and toss that silly wrench.

 

[Manual Mac]

I can honestly say I have never used a torque wrench on these clamping nuts until just now out of curiosity.
They’re just shy of 25 Ft. Lbs., and I alternate tightening sequence ‘til I get ‘em where I like ‘em. I use never-seize on them, so reading may be a bit higher.
I’ve always done ‘em up like this & have been doing it for many years with no problems.
my Griz Taiwan made RF 31 clone is a 6-04 build with 2 bolts, not 3.
This is my mix-n-match wrench, a 23mm craftsman socket, short Williams extension & old Kraeuter 1/2” ratchet.
This works 4 me, of course YMMV.
Cheers, Manny