how to machine flats inside a box end wrench?

Broach

And generally broached in stacks of several in a jig to save money/time. That is, of course, unless it's a super cheapie. Those seem to be forged with the hole/flats in place. That's probably the reason they don't fit well on nuts: Can't forge to tight tolerance.

Koz

They don't machine them. They forge them around a mandrel. Because forging directs the grain of the metal advantageously, a forged tool is stronger. But that's not why they do it that way. They do it because it's also a lot cheaper.

However, if you wanted to machine them, you could do it with a form-broach. Or, if you're really patient, with a shaper.

Are those all covered in your book? If not, ask.

Ed Huntress

snipped-for-privacy@evcom.net (Dave Wilson) wrote in news: snipped-for-privacy@posting.google.com:

With a broach. Basically, it's a cutting tool the shape desired, but with many cutting teeth along it's length, each tooth cuts a little more out as the broach is press through the hole..

Several explanations are given for how manufacturers make the box ends. Another method could be used to create a hex opening in a home shop. If you look at Snap-On and some other sockets, you'll notice that the "corners" aren't sharp angles, but instead, small circles located slightly outside the corners. They claim this is an advantage over sockets with sharp corners.

This could be accomplished with a mill and a rotary table, with an oversize hole circle of 6 points, then mill the flats to the size of the hex. I suppose 12 points could also be done, which is just 2 hexes, but it leaves less metal for contact.

WB .................

Gosh Ed,

I'm surprised you didn't mention EDM. That's how I made a couple custom ones.

Karl

form-broach.

I dunno, Ed............years ago I made some hex punches for Stanley / Proto--as I understand it, after forging and while the wrench was heated to a dull red, the punch was run through to give a final sizing to them, in a single pass.

But I cant recall for sure though whether these punches were for sockets, or wrenches, or perhaps both...........

I do recall however they were of annealed M2 HSS, turning this material in that state was almost like working aluminum, unbelievably soft and gummy.

Onesies, twosies, you can make them with a file, if you have the patience.

Ed Huntress

They've been made in different ways over the years. As a matter of fact, wrench *sockets* were push-broached by most makers for many years, and then Sears had them made by somebody who forged them over a mandrel in one shot. It made a better socket, and Sears made some advertising hay with it. The broached ones had burrs at the bottom of the socket, which didn't look very good. However, Sears was hardly the only one who made them that way.

I don't know how they're making box-end wrenches these days, but I remember that at least some of the better manufacturers were forging the insides the last time I looked.

Ed Huntress

Production broaches are usually pulled.

Thanks for the replies. The book I'm reading, Machining Fundamentals, by John R. Walker, does devote a couple pages to broaching, and I can see how it works. I guess the cutter increases in size until the finishing teeth, which are a constant size so the finished flats are parallel?

Another poster mentioned broaching sockets. How does the broach get all the way to the bottom of the socket? Is it a series of blunt end broaches, that increase in diameter?

I'd like to find a night school class on basic machining, like the welding class I took last year, but there doesn't seem to be any place in Palm Beach county that offers that.

Dave Wilson

That's a production-type multi-tooth broach, used in pull-broaching or push-broaching for volume work. There also are single-tooth broaches, used more often in jobbing work. They're usually pushed, except for some keyway broaches, which are pulled, in a machine that looks like a vertical shaper -- or that often *is* a shaper, horizontal or (antique) vertical.

It's a single-edge broach with, as you say, a blunt end. It's done in one shot. There is only one size broach for each size wrench.

It's probably done on fully-annealed stock.

Steve Austin wrote in news:3ffa66c4$0$86270$ snipped-for-privacy@news.westelcom.com:

Agreed.

Generally, in the past, a punched socket would either have an internal groove within its recess for the "chips" to fall freely or not.

Cheap sockets, often imported for discount houses will often have within them a quite visable "burr" ( or rather six of them in the case of a six point socket )

Higher quality sockets will usually have the groove, and no inside burr will be visable..........

I have some fairly new Craftsman sockets, I will get one and speculate on how these were produced, hang tight a sec.............

Ahh, a very fine looking tool indeed, this is a 16 mm socket, having a 3/8 sq drive, I purchased it as part of a set less only a few months ago..............

Missing are the internal burrs, and there are no signs of an internal groove having ever been turned.

It appears the hex socket was finished using the punch method, else by some sort of internal swage forming technique.

I would tend to speculate towards the latter, as the finish is almost mirror like--certainly to polish the inside of a socket to this high a lustre would be cost prohibitive, thus, I would guess this basically reflects the pre-plate finish, more or less.

This certainly lends support to Ed's claim as to the most modern methods..............

At first glance, I would have speculated the 3/8 drive to be broached, but again, there is a very nice finish on these surfaces also.

As the hex recess seems most likely formed using a sort of rotary swaging technique, and the technique should lend itself just as well to a square drive as to a hex, I would futher speculate both are generated with the same tooling in a single operation these days.

Pure speculation on my part, but as to the original question " how are these machined"-- the short answer is they are most likely not "machined" at all, rather they are "formed".....entirely from blanks through deformation, and no material removal is involved whatsoever.

The socket can be made oversize with an internal bore, an arbor or mandrel can be inserted, and an external rotary swaging operation can be performed to bring the metal down to form the internal shape and the OD in one pass. The socket can then be mechanically stripped from the arbor/mandrel and lathe trimmed/faced for finish length. We do similar swaging almost daily in our production, and lucky me gets to make and maintain the swaging dies. Precise length is difficult to maintain due to the flow of the metal in it's plastic state. Our rotary swager makes about 3,000 hits per minute. Another method is cold forming, where a mandrel is simply rammed into the round stock to form the piece. The film I saw was showing about a second of cycle time for the part, and it was smoking.

RJ