loose screw issue

[Patio]

Just a crazy thought.

Hard to explain.
This is a hole with a pin that is captured and spring loaded. Detents on the underside of thumb screw. When screw is almost time the plunger will settle in one of the detents keeping the thumbscrew in place. Nothing to loss and should never wear out.
Just a thought.

[John Hasler]

A similar solution is a ball detent.

[warmstrong1955]

A similar solution, but infinitely adjustable, would be a friction lock, like on a Morse hydrostatic or throttle control.
Basically, a spring loaded mini-brake pad, which would rub against the inner face of the knob.

[pete]

An interesting problem. I'm no materials or design expert so just a few thoughts. I see two items that are helping to create your issue RSG, the fine pitch thread and the aluminum threads having a lower coefficient of friction than another material might have. Plus depending on just how tight that thumb screw is done up it may not be getting within it's elastic tension limits that help fasteners to remain tight. Those plastic inserts should work for awhile, but even the proper Nylocks as others have said have a limited number of times they can be reused and still work reliably. Maybe a two piece thumb screw with a higher coefficient of friction stud material, coarser pitch thread (custom pitch tap and die?) tighter H limit on the threads and some type of hard rubber material in that cross hole with it's higher compressibility might be a semi permanent fix? I think I'd try cutting up some O rings of the correct diameter for your cross hole and see how durable those might be and just how well that might keep that thumb screw tight over multiple uses as a start.

[RSG]

Just a crazy thought.
49823697931_891bd8107c_c.jpg
This is a hole with a pin that is captured and spring loaded. Detents on the underside of thumb screw. When screw is almost time the plunger will settle in one of the detents keeping the thumbscrew in place. Nothing to loss and should never wear out.
Just a thought.

Thanks for the time and thought Patio, while the concept is good the spot you have that pin in would stop the spool from spinning because it's located on the outer race. Everything must be on the inner race to work.

[RSG]

Basically, a spring loaded mini-brake pad, which would rub against the inner face of the knob.

I'd love to see what this looks like. I googled Morse Hydrostatic but cant find anything that resembles your idea.

[RSG]

Maybe a two piece thumb screw with a higher coefficient of friction stud material, coarser pitch thread (custom pitch tap and die?) tighter H limit on the threads and some type of hard rubber material in that cross hole with it's higher compressibility might be a semi permanent fix?

Thanks Pete. I've considered using a different material for the screw but can't find a suitable method to fuse them together. I'll have to give that some more thought.



I really appreciate everyone stepping up to the plate.

[warmstrong1955]

I'd love to see what this looks like. I googled Morse Hydrostatic but cant find anything that resembles your idea.

Might be a thing of the past. Newer designs are more into belville washers.
Quadrastat made them too, but they had an bolt adjustable spring, to increase the tension on what equates to a caliper, clamping on what looked like half a brake disc on the mount.
I may have an old catalog, or parts list from an old machine somewhere.

I was picturing a detent mechanism like Pat drew, but instead of a rounded plunger or a ball, which indexes in dimples or grooves in the knob, it has a brass, bronze, or even nylon 6/6 plunger that is flat on the end, and rubs on the face of the knob. A mini disc brake.

Bill

[warmstrong1955]

Here's the Quadrastat one I remember.
Similar idea, a brake, but a different execution.

https://www.cw-industrialgroup.com/geta ... 7_brochure

Bill

[BadDog]

That's a nice idea. As long as it's captured so as to not be lost in a stream, lasts effectively forever, and leaves the tension right wherever you want to leave it.

[pete]

A tapered cross pin and taper reamed hole would work well to pin the stud and thumb screw head together and allow easy disassembly in the future if required. Not sure if the pins are available in stainless though. They should be for any less than ideal environments. But I've not ever gone looking for stainless taper pins before.

Edit https://www.mscdirect.com/FlyerView?pag ... s/big-book 18-8 stainless at least with just a quick search of the MSC catalog.

[RSG]

I was picturing a detent mechanism like Pat drew, but instead of a rounded plunger or a ball, which indexes in dimples or grooves in the knob, it has a brass, bronze, or even nylon 6/6 plunger that is flat on the end, and rubs on the face of the knob. A mini disc brake.

Bill

Would be a cool idea but no place to put it. Remember the outer part of the thumb screw must remain open so the spool spins freely.