Verhoeven rail bolt torque specs.
- Thread starter redcordes
- Start date
Because no table manufacturers have ever recommended a rail bolt torque. The torque is specifically determined by the rail bolt anchor system, not the torque specification of the bolt used! Using T-nuts for anchors like Olhausen installs in their rails won't hold up to a higher torque specification compared to a GC3 or newer, or a Diamond for example. All billiards tables that use the threaded inserts, or the floating nut plate need to be set at 15ftlbs torque.
Ya, years ago I was setting up torque control power tools at a tractor assembly plant and one of the parts was a rubber clamp sandwiched between 2 metal plates, the bolts were something like an M8. The torque spec was for a M8 Grade 10.9 from some bolt chart. Not only could I not reach their torque spec. with my tools, when I got there using a digital torque wrench, the rubber was completely flattened/extruded. Ugly looking assembly.
Suggested to the ME to revisit the spec and get back to me.
I have run across the same over the years. The engineers are not always right. Sometimes they are sitting at a desk and not really familiar with the application.
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That's what most mechanics don't understand when they're using impact drills to install the rail bolts. I only use a 12V Makita drill to install the rail bolts, then finish tightening with a torque wrench.
I believe all major cordless brands of Drill Motors come with a clutch. I'm happy with using a drill clutch, if the mechanic comes back with a torque wrench to finish the bolt, rather than relying on the crude clutch on a drill motor. The clutch on a $200 drill motor will not clutch out better than within +-50% or worse your desired torque.A drill with a clutch is your friend. I've run across some real fine work by people who refuse to use anything but an impact driver.
Mechanics that use Impacts and then come back with a torque wrench, need to keep in mind, when they go to the wrench, they must see the bolt move before the wrench clicks off. If there's no movement before the wrench clicks?, that bolt is in an under torqued condition!
There is NO argument against that statement!
That bolt needs to be slightly backed off, then moved forward with a nice and smooth pull, till the wrench clicks. Done.
Do not double click just to make sure. If your pull is smooth and steady (bolt doesn't stop moving) till the click, you are good. Move on.
Those that say they can tell using an impact by the sound/socket movement and what not, cause I have decades of experience, are kidding themselves. Those folks don't understand torque at any acceptable level.
OH BOY!
Hear It Comes.. Since I'm not a Table Mechanic
Just a torque nerd, thank you very much.
If the wrench clicks before the bolt moves that would be an over torqued situation, not "under torqued". If the bolt does not spin before the wrench clicks that means that the bolt is already tightened higher than the settings on the torque wrench. I'm not sure how accurate torque settings will be on pool table rails, especially if it is a flanged bolt with no flat washer under the head of the bolt because of the friction between the fastener and the wood. Flat washers would help but generally torque specs are for a lubricated fastener with lubrication not only on the threads but under the head of the bolt also. On the other hand the torque settings I have seen are generally low enough so that the fastener is not actually getting stretched so lube probably doesnt come into effect. Just rambling, carry on.
I'm glad you made your comment. I went back to what I said and of course there is an argument.
In the scenerio I described: Running down a bolt with a power tool then coming back with a click wrench to finish it off.
If the wrench clicks before the fastener moves using the above process, there's no way to know what condition that bolt is in. I could be over torqued or under torqued. All we know is the wrench clicked. A click wrench doesn't give you a torque reading. It only gives an audible and tactile signal that the spring, block, cam.. has reached its limit.
If you really wanted to find out the condition of that bolt, you would need a Direct Read type torque wrench. In the old days torque auditors would use dial and flex beam wrenches. That took a lot of skill since you would have to watch the needle climb, then drop, then climb again. They would have to capture the drop (when the fastener moved). These days, auditors use highly sophisticated electronic wrenches with multiple transducers to give them a torque reading and a gyroscope system to measure degrees of angle after movement. These wrenches automatically capture when the torque curve drops and report that number.
The fastener must be in motion at the time the wrench clicks. If it doesn't move then it should be backed off, then moved forward.
As far as lubrication is concerned, I recommend following the instructions. In more complex assemblies than pool tables, the engineer will state dry or lubricated and what type lube. If lubrication is used for a dry application, the torque target will be lowered.
Getting back to pool tables. If the OEM assembly has no washer but you want to add one, I would consider the washer, lubrication, since the bolt rotation isn't being hampered by grinding against wood.
Since there's no OEM published torque specs, we can do whatever the heck we want to do.
Nothing that I've written matters a whit when it comes to pool tables.
How would the bolt not be over torqued if the wrench clicks before the bolt turns? If my torque wrench is set at 100 ft lbs and the bolt turns before the wrench clicks it would be torqued to under 100 ft lbs. If I try the same bolt and it does not turn before the wrench clicks it must be over torqued otherwise the bolt would have turned. Of course it takes a few extra ft lbs of torque to over come the friction of a bolt that is very near its recommended torque value but that is splitting hairs. if we are going to be that anal about fastener torque the only accepted method is measuring bolt stretch. I am well familiar with digital torque wrenches with gyros, I have 3, 1/2", 3/8", and 1/4" drive, oddly enough it was the small 1/4" drive that was most expensive.
Yes, I'm that anal about torque.
Torque measurment is a dynamic measurement, not a static measurment. Meaning the fastener must be in motion when torque is achieved.
If that's a fact, then if you try to check/audit torque, the fastener must be moving. You mentioned Prevailing Torque (friction) in your comments all along this discussion.
When DC Nutrunners are set to install bolts at a certain torque, the tool shuts off when torque is met. That fastener was moving when the tool shut off. When these type tools are set up, there's an auditor that puts an in-line transducer between the tool and the fastener to verify that the installing tool is operating correctly. Most quality minded assembly plants I've worked with do this process. Automotive, Farm, Aerospace.
Yes it gets anal.... very a...
I'm just stating facts that I've been taught and have taught and those beliefes are verified with my library of books, seminars and pamphlets.
Like I said, since there's no published torque specs according to the Cobra, none of this matters. "Ya all" can do it by feel. Goot e-nuff.
Been studying this topic a long time.
Retired and done