What's new
What's new

Jack bolt Material??

machin33

Plastic
Joined
Jun 16, 2020
Hello all

new user here.

I need to make some leveling bolts, the size is 1 1/4" 12TPI, this is for a heavy pillar holding up a beam with a robot mounted on it.

I already have 4 bolts, but need 4 more. I have checked the material of the existing bolts and the elements are about:

Iron 86%
Tungsten 8%
Manganese 2%
Chromium 1.5%

So I'm wondering what material/ alloy I should make these bolts out of.

thanks guys.
 
That seems like a more "exotic" composition for a jack bolt than I would expect. Is there anything special about the geometry of the bolts, or could commercial grade 8 hex bolts do the job? What length are the current bolts, and any special features?
 
Yeah, 8% tungsten seems more like a high speed steel. Tungsten's purpose is to stabilize carbides to provide a harder alloy at high temp.

If the screw itself is not lifting a furnace in operation and your temperature is not high, then you're after strength, go with 4140. For corrosion resistance, a 300 series stainless.

You can buy pre-made jack screws from, for example, Nook.
 
You need to consider what profile of thread to use also. I found the best jack screws has a fine thread, like BSF for instance.

Regards Tyrone.

1-1/4 - 12 is certainly a fine thread. In fact, it's an excellent thread, only surpassed by the extremely rare 1-9/32 - 14.7 thread, which was only in common use on Tuesdays.

In December.
 
1-1/4 - 12 is certainly a fine thread. In fact, it's an excellent thread, only surpassed by the extremely rare 1-9/32 - 14.7 thread, which was only in common use on Tuesdays.

In December.

Only during leap years! ...how many more times do I have to remind you? :rolleyes5:
 
Only during leap years! ...how many more times do I have to remind you? :rolleyes5:

I can't help it! I've got a very tiny brain rattling around in a trapezoidal skull, and it gets stuck in the corners all the time. Makes it very hard on the old synapses.

Besides, I bet YOU can't remember that it's the Julian calendar, not Gregorian that determines the Leap Year date!

So there...
 
I can't help it! I've got a very tiny brain rattling around in a trapezoidal skull, and it gets stuck in the corners all the time. Makes it very hard on the old synapses.

Besides, I bet YOU can't remember that it's the Julian calendar, not Gregorian that determines the Leap Year date!

So there...

Don't you go getting all smartass with ME sunshine!
 
1-1/4 - 12 is certainly a fine thread. In fact, it's an excellent thread, only surpassed by the extremely rare 1-9/32 - 14.7 thread, which was only in common use on Tuesdays.

In December.

I thought 1-9/32 - 14.7 was only used in western Slovenia.
 
You guys forgot the most important part: The 1-9/32 - 14.7 thread uses Löwenherz thread form!

Geez, a guy's gotta work full time to make sure that there's no errors on the interweb.

I suspect that the thread form is determined by what was used on the other 4 existing jacks. Be interested in knowing what that thread form was. V-form is pretty poor for transmitting thrust. Acme or trapezoidal?
 
Sort of back on topic - I'd imagine ASTM A193 B7 would make good jack bolts


I thought I'd replied, but don't see the response here (I'm slippin', guys). Acknowledging John Oder's superior knowledge, but doesn't ASTM A193 B7 use unified thread below 1 inch, and eight pitch above? The OP wanted 12 tpi or that was my impression. So, at least, it's not off the shelf.

Would 8 pitch, or even coarser jackscrew pitch still be manageable? A 1-1/4 jackscrew is going to be rated about 3.5 tons. Normal jack thread for this size is between is 4 and 8/3 tpi. Assume 3 ton max load, 4 pitch, meaning the theoretical tangential force at the thread pitch line will be 480 lbs (6000lb/4*pi). Add 50% for friction (a 60° screw will be higher than an ACME or, heaven help us, square). Torque is 720lbs*1 inch or so pitch diameter. About 60 ftlbs. The point of the calcs was to find out if a coarser thread pitch would be workable if the jacks are manually operated. 60 ftlbs sounds manageable. Seems like the OP could probably go to an 8 pitch just fine as far as force is concerned. 12 pitch might give a little better adjustability.

This got me to thinking about what is used for scaffolding. Interestingly, the scaffold leveling screws are 1-1/4 hollow threaded rod, with a bizarre thread form. Given that you can pick up 4 for about 77 dollars, if the 2 ton rating is acceptable this might be a good solution. But what form is that? The short (12") posts shown below, but there is a 24" post that's 1.375 inches OD and uses 4 pitch ACME. The threads below don't look like ACME, or are they?
https://www.amazon.com/dp/B00Q62P6MI?tag=duckduckgo-d-20&linkCode=osi&th=1&psc=1

71YUNY9uhRL._AC_SL1500_.jpg
 
Thanks for the replies.

this pillar is not getting hot or anything :)

it doesn't need to be corrosion resistant(stainless)

I have already tapped the holes with a 1 1/4 12TPI (to match the other pillar) it is a standard UNF thread.

I would like to make my own jack bolts for these holes now, I have some threading experience on a lathe.

I'm just not sure what material I should use for something like this.

the existing jack bolts thread length is about 6.5" with another 1" cut square on top for a wrench.
 
I'll add (now that we're back to boring mode) that the rolled thread of threaded rod (either Gr8 or B7 are available from McM, but they don't ship to CAN without an intermediary (I think)) gives a smoother, harder surface than cut threads. I'd go with the threaded rod, even if I'm just dying to use my lathe.
 








 
Back
Top