The Home Machinist!

As they say a photo (even a not very good one) speaks a thousand words!

Here, principally for you, Harold, is the wing nut job. Extreme right is the wing nut itself that needs the concave cut-out at the left hand end. It screws onto the end of the rod. Positioned on the rod is the cylindrical cross piece that when everything is fitted up will seat between the jaws of the brake lever and which the concave of the wing nut will fit around. At the extreme left is the fork, screwed onto the rod. This holds the whole assembly to the brake pedal with a clevis pin.

Rex suggested holding the wing nut vertically in a milling vice using the wings. This was a very good and logical suggestion. The wisdom here was (totally unsound) that the wings have to be at right angles to the axis of the concave.
It obviously doesn’t matter a damn, but I accepted the ‘accepted wisdom’ which negated Rex’s sound advice. Thus I devalued the set-up considerably by trying to hold the wings horizontally.

Someone else (Glen?) suggested inserting a rod in the thread of the wing nut and using that as a ‘holder’. That was another very helpful idea. I actually used the rod that is part of the assembly. Packed out the fork end to add rigidity and held that by its cheeks in a second vice.

I intended to use a ball-nosed end mill to cut the concave. Rex said an ordinary end mill was all that was needed. Absolutely right (again). That’s what I used – two in fact, one to make the initial shape and a larger diameter to widen the radius. I guess the perfect cutter would have been a slot drill. Not sure (any thoughts?)

Happy ending? Not quite. Towards the end the wing-nut moved in the vice. I abandoned milling and finished the job with files.

I am, as of today, not a good miller. I’ve learnt a huge amount from this brilliant site and its equally brilliant people. One, when milling, make it all run true by using test gauge indicators on the vice etc etc.

But, am I under-estimating the need to HOLD firmly. I’m using drill press vices and a-not-very-high quality tilting vice that came, as a freebie, with my machine.

I’m saving up for a Vertex milling vice. That’s a Taiwanese make that I think is pretty good. I have their chuck for milling collets and it seems A1. I can’t afford a Kurt and I don’t think they are available in France. Record are astronomically expensive and I don’t think they make machine vices (only bench jobs).

Will a good milling vice help me?

Martyn

It certainly wouldn't hurt, but I believe the part to be held requires a little thought. Holding by the wings is risky, regardless of the quality of one's vise.

In order for the results to be in keeping with the requirements of the application (the concave to be generated should be at a right angle to, and on center with, the thread in the wing nut), I would suggest that both should be generated in the same setup. If that is not an option, personally, I see no easy solution.

Were that project mine, I'd likely make a set of jaws (they can be simple insert pieces, made of aluminum, set in the existing vise) that gripped the piece by the body. That would lend support where it is most needed, near the cut, to prevent movement. Proper relief on the inserts could allow for vertical orientation of the wings, and the radius plunged with an end mill, or even generated with a boring head. The inserts would be placed in the center of the vise, to eliminate canting of the jaws when the vise was tightened.

The cut isn't the problem---holding and orientation is. Problem is, there's no easy way to assure alignment, although a snug fitting threaded piece could be installed and used to determine orientation. A lot of extra work, but it would assure the proper outcome. Seeing the picture, there's no way in hell I'd try to hold the part by the wings. The mechanical advantage of the cutter over the vise is far too great.

If the thread is already established, and it's not at a perfect right angle with the body of the part, one could add a few thou clearance to the cross piece, so it could center on the radius that is established in the nut. Not the best solution, which would be to drill and tap the the thread, then cut the radius in the same setup, using a ball end mill.

Harold

_________________
Wise people talk because they have something to say. Fools talk because they have to say something.

Hi There,

How about holding the wing-nut is some Cerrosafe or
similar low melting point metal.

A box could be constructed out of aluminum,

The wing-nut threaded onto a piece of threaded rod
(held in a collet in the spindle of the mill to insure
perpendicularity to the spindle),

The box placed in the mill vice and positioned so the wings
are in the box part and the molten Cerrosafe poured around it.

Once the metal solidifies, it should hold the wing-nut firmly
enough to do the machining.

Just an idea that may work.

Good Luck!
-Blue Chips-
Webb

I would think even lead might make a suitable molded fixture. From the picture it looks to me like a pair of shallow grooves in the vise jaws holding the cylindrical body or something similar would do the job adequately. A threaded rod inside would prevent collapse if that is a concern. If orientation is wrong, mount the vise on a 90 degree angle, if clearances allow.

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Don Young

And a good one, assuming a guy has the Cerro bend. Much faster and easier than making the jaw inserts, with 100% support of the part. With the wing nut already tapped, it would be dead easy to orient the nut in a vertical position, using a threaded rod.
I heartily endorse the idea!
The idea of using lead isn't too good--it's likely to solder to the wing nut, but would serve quite well otherwise. I expect a little paint on the nut might eliminate that problem, though.

Harold

_________________
Wise people talk because they have something to say. Fools talk because they have to say something.

Thank you everyone for the advice.

As I said in my note I did get a result that works in service but I was very, very unhappy with the holding.

I now see much better ways of tackling this and think the temporary jaws for the vice are very clever and wouldn't be difficult to make.

One day I will need to make another part the same (for another car) and feel I now have much better methodology.

Thanks again.

Martyn

I wonder if you could make up a workholding fixture with a threaded stub to fit the wingnut. Screw the wingnut onto the fixture with loctite ahesive, so it won't unscrew. Use care to not overheat the part when machining. To remove, just heat the wingnut to about 400F with a torch (or place in the oven) to soften the loctite.

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Dan Watson
Building IC mikado in 1.5" scale

My concern would be much the same as gripping by the wings. The relatively small diameter of the thread versus the length at which it would be held would yield a serious rigidity problem. In brass, that could prove interesting using conventional cutting tools due to its (the brass) propensity to hog. This is a good place to observe the no greater than three times a diameter for projected length.

Harold

_________________
Wise people talk because they have something to say. Fools talk because they have to say something.