View Full Version : Locking a bolt?

Stuart Br
01-28-2011, 04:12 PM
Simple question, but I can't get my head around the best way to achieve a solution. My local clay shooting club has a couple of ancient auto traps. The height adjustment on these is a PITA and has been botched in the past. Currently it consists of a 10mm socket head bolt passing through the body casting and clamping handle which clamps a slotted strip. As you will see from the photo the existing red clamping handle is totally useless as the bolt head spins resulting in the handle fouling the base casting web.


Due to the size and instability of the carousel above the height adjuster, it is really difficult to get access to both sides, so needs at least two people plus tools to adjust.
My plan is to modify the clamping so that access is only required from one side. This means the elevation can then be changed single handed. To do this I want to replace the socket head bold with a standard hex head bolt and somehow stop the head from spinning on the reverse side.
I will then replace the existing handle with a ratchet clamp.
Best way to do this?
a) Mill a recess in one of the flats of the bolt head, to take the head of a socket head machine screw. In a similar manner to that gunsmiths use to lock screws.
b) Make a small plate that buts against the bolt head across a couple of faces and screw the plate to the base casting. i.e. a mini spanner that is bolted to the casting.
c) Any better ideas???

Thanks in advance for any advice

Just for completeness, here is the whole trap and no neither the welding, nor the duct tape are my efforts. You can see the existing clamping lever just being the vertical strut.



01-28-2011, 04:52 PM
My immediate thought is that you can use the long slot in the adjusting strut to hold the bolt. Either:

1) Substitute a carriage bolt for the existing bolt. The square underneath head will lock into the slot.
2) weld a small tab to the existing bolt so that it engages the slot. (Can you tell that I just learned to weld!)

I suspect the red handle is supposed to hit the casting, thus stopping the spin.


01-28-2011, 04:58 PM
Hi Stuart:

I don't know anything about trap shooting.

Do you transport the device lowered, then raise it all the way up when you get to the shooting spot?

- or -

Do you need fine adjustment for range?

I'd be inclined to use a threaded rod with knurled locknuts and forget about the sliding slot thing for fine adjust.

01-28-2011, 05:15 PM
Replace the slotted strip and clamping handle with a turnbuckle assembly.


01-28-2011, 05:20 PM
Remove the red handle, and reinstall the bolt. Secure the adjusting arm with a coupling nut. Orient the handle in a convenient direction, and secure it with another bolt into the coupling nut. Tack-weld the handle to the coupling nut.

The idea is to put the handle far enough out so it will not interfere with the casting as it is turned. If one coupling nut is not enough to clear the casting, add another coupling nut to the stack with a short piece of threaded rod, and tack-weld it together.

01-28-2011, 08:20 PM
I'd try something like this.


Make a double ended Tee nut that would ride inside the arms slot. Run one half thru the frame and put a nut on it but not so tight as to keep it from moving... that would allow the the handle to be used while the arms slot acts like a wrench to keep it from spinning. I did something similar to the banjo adjustment nut on my atlas lathe so I only need one tool to work it.

Stuart Br
01-29-2011, 04:01 AM
Thanks for the input guys.

The height adjustment is for changing the flight of the clay. It is not required to be a precise adjustment as we don't shoot any of the "fixed" disciplines.
Those (Skeet, Trap, etc) require the clays to fire at specific angles and distances. We shoot "English Sporting", where basically anything goes, the clay can be thrown in any direction, height and distance.

I kinda like the Tee nut idea using the slot to stop it spinning. I will have a look tomorrow when I go to the ground and see if it looks feasible.

BTW I am missing welding from my skills and kit at the moment, although I could get it done elsewhere.

01-29-2011, 08:52 AM
How about replace the mechanism with a $20 car sissor jack?

01-29-2011, 09:08 AM
Tap the frame M12

Turn a M12 Set screw down to 10mm except enough to screw into frame.
Leave enough 10 Dia for sliding bit and thread rest 10mm
Modify handle to suit.

Steve Larner

Marc M
01-31-2011, 05:46 AM
The quick and easy route for a few bucks:


They have a variety of styles / threads. Just pull the handle out and turn to whatever position you need.