Making a skip bolt some call it a shoulder bolt

[Frank S]

There are times when the exact size skip bolt or shoulder bolts simply do no exist off the shelf or if they do they are special order.
For a project I am working on I don't need precision ground and hardened bolts but I do need a shoulder.
There are a few ways to accomplish this 1 would be to start from scratch with a piece of hex stock then machine out the bolt as required.
Another way would be to slide a length of tubing over the bolt which in my case would have worked just fine, but I opted for a third way
By drill and taping a piece of round stock turning to desired length then screwing it onto the bolt.


I purposefully drilled 1 size over size to make the taping easier

I also turned a step on the nut for locating it in the hole


The shoulder on the bolt protrudes beyond the wheel mounting plate to lock against the nut welded into the member

the trolley truck is free to rotate about the shoulder
while the shoulder being tightened against the nut and centered to the hole side ways stresses and movement is all but eliminated

[DIYer]

Thanks Frank S! We've added your Shoulder Bolt to our Fastening category,
as well as to your builder page: Frank S's Homemade Tools. Your receipt:

Shoulder Bolt by Frank S

tags: fasteners

[metric_taper]

I guess I'm confused by your shoulder bolt, it seems your more making a sturdy threaded extension of the trolley truck pivot so that the hole does not elongate or rotate from the perpendicular mounting you want. I guess in my narrow view a shoulder bolt is used as a pivot axis for some other part in a machine.

I've made shoulder bolts via a fourth way (sorta your first method starting with raw hex stock), start with the next bolt size larger, machine the threads off, and any shank of unthreaded down to the hex head of the shoulder diameter you want, then machine the length of the OD for thread pitch you need, leaving the desired shoulder length, single point it or use a thread die.

I typically will support the bolt with the tail stock and a center drilled into the end of the bolt.

It should be interesting to see what your making with all these jigs and fixture posts of late.

[Frank S]

I guess I'm confused by your shoulder bolt, it seems your more making a sturdy threaded extension of the trolley truck pivot so that the hole does not elongate or rotate from the perpendicular mounting you want. I guess in my narrow view a shoulder bolt is used as a pivot axis for some other part in a machine.

I've made shoulder bolts via a fourth way (sorta your first method starting with raw hex stock), start with the next bolt size larger, machine the threads off, and any shank of unthreaded down to the hex head of the shoulder diameter you want, then machine the length of the OD for thread pitch you need, leaving the desired shoulder length, single point it or use a thread die.

I typically will support the bolt with the tail stock and a center drilled into the end of the bolt.

It should be interesting to see what your making with all these jigs and fixture posts of late.

The trolley truck allowed to pivot on the shoulder of the bolt, since after the bolt is tightened into the locating hole the truck still has a few thou. clearance.
The reason for the step nut being welded in place it to provide a land or a stop if you will to provide a positive locking location for the bolt this pilots the shoulder as well placing the threads of the bolt in tension and not shear. There is no possible way for movement other than rocking pivoting motion on behalf of the trolley truck

[Frank S]

It should be interesting to see what your making with all these jigs and fixture posts of late.

You possibly could get an early viewing of it at SEMA in Vegas this year if I can burn enough late night oil to get it done in time

[Saltfever]

Frank, it looks interesting and quite useful but could you please sketch a cross-section of the assembly?

[Frank S]

Frank, it looks interesting and quite useful but could you please sketch a cross-section of the assembly?

here you are

[Saltfever]

Hi Frank: Thanks for your fast reply and my apologies for my slow response. Its been a rough past few days!

Sorry for the persistent questions. I'm still trying to find the nut with a shoulder and how it locks in place and still give freedom of rotation.

It appears to have more flexibility in design compared to a shoulder bolt. Is the sleeve free to turn or is it locked in place?

[Frank S]

Hi Frank: Thanks for your fast reply and my apologies for my slow response. Its been a rough past few days!

Sorry for the persistent questions. I'm still trying to find the nut with a shoulder and how it locks in place and still give freedom of rotation.

It appears to have more flexibility in design compared to a shoulder bolt. Is the sleeve free to turn or is it locked in place?

the nut has a short shoulder to pilot into the hole then it is welded to the structural member, the shoulder of the bolt pilots into the hole as well this insures any side loading is carried by the shoulder of the bolt.
I could have just slid a sleeve over a bolt just as well but I wanted the assembly to be dead ridged and centered to another truck assembly.
the truck assembly is free to rotate on the shoulder in the space between the head of the bolt and the structural member
Actually rotate is a misnomer it would be more like oscillate since there will be almost zero movement having the bolt as the pivot in the truck assembly just assures that the rollers will be equally loaded with no single point loading of any 1 bearing possible