How to make tommy bar nuts?

[Ian ParkinParticipant @ianparkin39383]

i want to make a quantity of tommy bar nuts and bolts like these

I’ll be using 1/2 bar with a 6mm tommy bar how to hold the bar in?

on the sample i have theres no sign of being pushed into an undersized hole,no sign of soldering..

how would you do it?

[FulmenParticipant @fulmen]

A set screw from behind? You already have the threaded hole…

[Ian ParkinParticipant @ianparkin39383]

Great idea some will have males though so i could make them all nuts and glue in a length of studding to make the bolt type…

[Nick WheelerParticipant @nickwheeler]

Move into the twentieth century and use Loctite….

[DC31kParticipant @dc31k]

The interior grubscrew above is a very good idea. It would not need to be the same diameter as the main thread. Little dab of loctite for security and use a pointed one to dig into the cross bar.

If you ever need to remove or reposition the cross bar, use a dog point grubscrew and a small flat on the cross bar.

In commercial quantities, either the cross bar or the main body could well be upset so they swell and grip the other part.

Another option is knurling and drive into the hole. That is how the wheel studs in your car are prevented from turning.

Loctite or epoxy resin is another possibility.

[Ian Parkin]

On Ian Parkin Said:

make them all nuts and glue in a length of studding

That’s how I usually do it. Not only is it much simpler to tap a hole than to turn and thread a thin screw, a piece of high strength bolt will also be a lot stronger.

[BazyleParticipant @bazyle]

Most common method I have seen is hit the middle of the bar with a pair of dies equivalent to drilling an undersized hole in the tool then cutting in half. This pushes out two ears like a minimal knurl in a way.

[old martParticipant @oldmart]

A very common practice with smaller ones is for having the centre of the bar straight knurled and the rest a sliding fit. The knurl will not be visible unless the bar is removed.

[Tony Pratt 1Participant @tonypratt1]

Loctite or knurling.

Tony

[Clive FosterParticipant @clivefoster55965]

Loosening is a potential issue with any form of grub screw retention. Whether external or internal.

The tommy bar on  the chuck key of my 200 mm Bison chuck is a bit loose but the grub screw hex is a poor fit on the key and can neither be tightened or removed. Presumably a low quality screw with soft end that has mushroomed preventing removal. Eventually it will annoy me enough to get drilled out and sorted. Properly!

If using grub screws it’s imperative to provide proper flat or hole on the shaft so these crew can get a grip. Over the years I’ve taken many things apart having such grub screws for retention. Non of the one with proper flats or holes ever worked loose or were problematic when removing. All the ones without flat or hole or inadequate ones tend to work loose and all fought back on extraction. Probably a moral there somewhere.

I generally favour a knurled band narrow enough to be hidden in the main body.

Clive

[FulmenParticipant @fulmen]

Another option is a straight pin through the back of the body. Peening the end and turning it down should hide any trace of it.

[Nigel Graham 2Participant @nigelgraham2]

Consider if you need the option of being able to move the body from the centre to close to one end of the tommy-bar, as sometimes used in small socket-sets. It also allows the bar to be slid back and forth as necessary to clear some obstruction in use.

For this, turn a shallow semicircular-section groove in the tommy-bar at both setting locations, for a grub-screw to run into.

The obvious draw-back is that in plain form, it is easy to lose the tommy-bar!

 

If the bar is to stay in the centre, you could use a small roll-pin to retain it. It will be visible end-on but no more noticeably than a grub-screw, and acceptable or not by taste.

The pin or grub-screw is of course, drilled axially in the body, not radially.

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