The Nutsaver

[Yanis]

This is one of those simple ideas that is so obvious that it is a surprise no one has thought of it before. I have to make me one of these for my Lie Nielsen skew rabbeting block plane.

http://www.popularwoodworking.com/wo...-writes-itself

[Pac man]

Bern has shared the process of making the nut saver on instagram


https://instagram.com/p/2gyKxSFrBS/

[pmcgee]

I have a similar sort of tool on a larger scale from Supercheap for car oil filters.
Paul

[IanW]

I guess it's a good excuse to buy or make another tool, but in an emergency, a broad rubber band wrapped around the nut will usually work. A strip of that anti-slip mat stuff wrapped around the obstinate object works even better.

Cheers,

[Yanis]

I would never buy one but I will certainly put it on my to-do list. A nice afternoon's entertainment.

John

[derekcohen]

DO NOT MAKE ONE TO USE ON THE VERITAS PLANES!

It will create too high a force at the circumference of the brass bolt, and cause it to shear! There have been reports of this occurring.

Far better than this is cutting a screw slot, as I have advocated in the past. This keeps the forces centralised.



Lee Valley will shortly be bringing out an improvement in this area.

Regards from Perth

Derek

[Yanis]

DO NOT MAKE ONE TO USE ON THE VERITAS PLANES!

It will create too high a force at the circumference of the brass bolt, and cause it to shear! There have been reports of this occurring.

Far better than this is cutting a screw slot, as I have advocated in the past. This keeps the forces centralised.

Lee Valley will shortly be bringing out an improvement in this area.

Regards from Perth

Derek

Not entirely sure what you mean Derek. A twisting force is a twisting force whether it is applied close to the center or at the circumference. If you mean that it may have a radial component then I can see that but it sounds more like the torque is too high in which case the trick is to not apply too much torque.

[derekcohen]

Hi Yanis

I am not an mechanical engineer, and indeed the courses I did in this area 40 years ago are lost in the mists of time as I strayed far from it. However something was nagging at the back of what is left of my brain, and I have done a limited amount of research.

What was nagging me is how shear failure occurs, and whether a screw slot is better/worse than a pair of vise grips, which Chris Schwarz advocated before he promoted the tool in your link.

I suspect that my instinct is correct, but others with the correct qualifications to comment are encouraged to comment. This is all aside from what LV come up with as a retrofittable solution - I have no idea what their plan is.

Here's how I see it (correctly or incorrectly): forces at the outside of a bolt head will act differently to forces at the centre of the screw. Excess force either way is bad, but forces at the outside of the bolt head will be bad regardless.

Part of the reason for the latter is that the outside forces can force the bolt shaft to twist, and this is what leads to shearing. A screw slot, by contrast, centres the forces - one is more likely to strip the slot if the down force is applied off centre.

One article I found that echos this is here (page 643): http://scholarsmine.mst.edu/cgi/view...context=isccss

"The typical failure mode observed in all tests was a combination of screw pull- out (tension failure), tilting of the screw (shear failure), and bearing of the sheet (shear failure). However, the normal- and low-ductility specimens did perform differently with respect to deformation and strength."

If I have understood this correctly, this tends to support the use of a screw slot, and explains why any form of vise grip, or similar, can be dangerous.

Please, I am not taking responsibility for those cutting screw slots - as I mentioned, mine are shallow and I do not over-tighten.

Perhaps LV will come up with a bolt that uses an Allen head. That would centre down force automatically.

Regards from Perth

Derek

[hiroller]

I think it's more that with a screwdriver you are applying torque with your hand to apply a force using a screwdriver handle with about a 15mm radius. With a nutsaver you can apply the same force using a 100mm radius. That is a lot more torque. Apparently more that the brass knob can handle.

[Yanis]

Hi Yanis

Here's how I see it (correctly or incorrectly): forces at the outside of a bolt head will act differently to forces at the centre of the screw. Excess force either way is bad, but forces at the outside of the bolt head will be bad regardless.

Regards from Perth

Derek

Yes - that makes sense. Brass is rather problematic in this respect since over tensioning or applying a lateral as opposed to a rotational force can easily wear the thread excessively. I think the issue as I said above is that it not only twisting the screw but it is forcing the screw sideways (shear) since the force is applied several inches to one side of the screw. I suspect that if you are careful and do not over tighten you should be ok. The danger is to apply more force than is necessary which is probably where you get into trouble.