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JoeLee
12-05-2013, 10:33 AM
I have to make a small rod with a 1/8" hex hole at one end, the hex hole needs to be about 1/2" deep, it's not a through hole. Does anyone think this is possible.

JL..............

adatesman
12-05-2013, 10:34 AM
Yup. Rotary broach.

TGTool
12-05-2013, 10:52 AM
Heating and forging might also be possible. Depending on how good a hex you need, it might also be possible to drill a hole that wouldn't form a complete hex, but would allow you to drive a suitably sharpened hex wrench down the hole and produce adequate corners.

Arthur.Marks
12-05-2013, 11:14 AM
I'm sure it is possible... but that sounds waay too big a ratio of diameter:depth for a rotary broach. Isn't the recommended ratio 1:2.5 ?

Tony
12-05-2013, 11:33 AM
If I were trying something like this in my basement hack shop :) (no EDM, no rotary broaches)
I think heat would certainly be involved.

Drill slightly undersized, heat, force a 1/8" hex in there.
Or, drill for a slight slip fit over your 1/8" hex, heat, and try to move material in.. swaging operation?

Maybe run an old scissor style knurling tool over it while its hot to bring material in?

Maybe you could get away with sharpening the end of 1/8" hex key and just forcing it in?
You'd have to make your hole just a bit deeper so that once all your chips have packed down
in there you end up with 1/2" depth. Probably need to support the outsides.. depending on
how thin wall it ends up.

Paul Alciatore
12-05-2013, 11:42 AM
You don't say a lot about the materials needed or the stresses involved.

You can buy inserts with a hex hole:

http://sdp-si.com/D810/PDFS/Section-4/81004032.pdf

They need to be soldered or glued in or perhaps a press fit.

If that is too much for your budget, you could consider drilling an oversize hole to the full depth and cut the top of a Allen head cap screw to insert at the end. Again, it needs to be soldered or glued in. Or again, a press fit may work. This leaves a wider hole under the insert but you have the hex hole at the end. This could work in some cases.

A.K. Boomer
12-05-2013, 11:48 AM
If you have a real small endmill and a rotary table you can create a nice hex with radius reliefs in the corners, actually stronger than the standard hex and puts less load on both hex and allen tool...

kinda ends up looking like snap-on's "flank drive" system...

JoeLee
12-05-2013, 01:54 PM
I'm not familiar with a rotary broach. The material is just mild steel shafting. My thoughts are to drill the hole slightly bigger than the hex key and take a piece of the hex key, grind the bottom flat so the edges are sharp and press it into the hole. It should shear the sides of the round hole giving me the proper size fit. This is just a guess and may require some trial and error attempts. If it works getting the piece of hex key out of the hole is another story. I think that is how are they done in set screws????

JL..................

macona
12-05-2013, 02:43 PM
You can get rod with hex holes already in it. Drill into your other rod and silver solder in an insert.

The Artful Bodger
12-05-2013, 02:52 PM
One possible solution, start with a steel tube and a hex key of the required size. Heat the tube and force the hex in after grinding and tapering the hex to make the job easier. The tube will take the shape of the hex and shrink on tight as it cools. Mount the hex in a lathe and turn the tube to minimum thickness, drill the end of your rod then slip the tube in and solder it in place. Now pull the hex key out.

mars-red
12-05-2013, 03:04 PM
I'm not familiar with a rotary broach. The material is just mild steel shafting. My thoughts are to drill the hole slightly bigger than the hex key and take a piece of the hex key, grind the bottom flat so the edges are sharp and press it into the hole. It should shear the sides of the round hole giving me the proper size fit. This is just a guess and may require some trial and error attempts. If it works getting the piece of hex key out of the hole is another story. I think that is how are they done in set screws????

JL..................


There's a great example of a small shop-built (and pretty easy to make) rotary broaching tool here: http://mikesworkshop.weebly.com/rotary-broaching.html I've actually started making one myself, but smaller (to fit a quick change toolpost on my watchmakers lathe). If you don't want to make a setup for rotary broaching, then the method you describe for pressing should work if you have some relief behind the sharpened cutting edges. You'll want it to be hardened too (especially for the kind of depth you're talking about) - if the hex key is made of some good carbon steel then hardening won't be a problem. If it's mild steel then I guess you could case harden it... or find some high carbon hex stock the right size. It might be easier to start with some good O1 or W1 rod and mill or file the hex shape (with the correct relief, at the same time) yourself. If you plan on driving a broach through like this it will probably be hard work, but should work if you're patient enough. One of my favorite blogs has a nice little demonstration of broaching a small square hole, using this same technique - it's shown part way down on this page: http://watchmaking.weebly.com/keyworks.html

JoeLee
12-05-2013, 03:38 PM
Here is a picture of the rod. It's pretty simple except for the hex part. I suppose I could just slot it for a screw driver or mill an external hex and use an open end wrench but that would be a small wrench and would get in the way of adjusting the nut that goes on the end, that's probably why they went with the internal hex in the first place. Other option would be to get a 5/16" - 24 set screw 1 1/2" long and fit it to the new shaft by silver soldering it, but there is a lot of pull on that end of the shaft and if it works loose the vari drive sheave comes flying off.

thanks for the info on the rotary broach.

JL.........................

http://i911.photobucket.com/albums/ac317/JoeLee09/Clausing%20Lathe%20Sheave/Image002_zps9c6e3768.jpg (http://s911.photobucket.com/user/JoeLee09/media/Clausing%20Lathe%20Sheave/Image002_zps9c6e3768.jpg.html)
http://i911.photobucket.com/albums/ac317/JoeLee09/Clausing%20Lathe%20Sheave/Image003_zps161cd7d3.jpg (http://s911.photobucket.com/user/JoeLee09/media/Clausing%20Lathe%20Sheave/Image003_zps161cd7d3.jpg.html)

awemawson
12-05-2013, 03:38 PM
I popped a hex socket in the end of a rod myself this afternoon by co-incidence. OK it was somewhat bigger than yours, and in HT steel but I'd do yours the same way. I milled a male hex on a piece of copper bar, then sunk it into the HT bar using my Die Sinker EDM machine. 8 MM hex 10 mm deep in about 5 minutes.

I'd upload some pictures if I could work out how! - let's see if this works .....

http://s155.photobucket.com/user/awemawson/media/Milling_Hex_zpsdd4ad2b5.jpg.html?filters[user]=39772696&filters[recent]=1&sort=1&o=2
http://s155.photobucket.com/user/awemawson/media/Hex_Electrode_zps49a87725.jpg.html?filters[user]=39772696&filters[recent]=1&sort=1&o=3
http://s155.photobucket.com/user/awemawson/media/Hex_Sinking_zps47b0bacc.jpg.html?filters[user]=39772696&filters[recent]=1&sort=1&o=1
http://s155.photobucket.com/user/awemawson/media/Hex_Result_zps2a9c833c.jpg.html?filters[user]=39772696&filters[recent]=1&sort=1&o=0

Andrew


ok that didn't work - they're here:

http://s155.photobucket.com/user/awemawson/library/?view=recent&page=1

duckman
12-05-2013, 03:53 PM
How big is the stock, and does the hex have to go to the bottom, if not turn a SHCS down, cut the socket off and press it in, if it needs more length turn 3 or 4 and put them on an allen wrench and push a bunch of them in at the same time.

Jaakko Fagerlund
12-05-2013, 04:04 PM
One possible solution, start with a steel tube and a hex key of the required size. Heat the tube and force the hex in after grinding and tapering the hex to make the job easier. The tube will take the shape of the hex and shrink on tight as it cools. Mount the hex in a lathe and turn the tube to minimum thickness, drill the end of your rod then slip the tube in and solder it in place. Now pull the hex key out.
I'm pretty sure the hex key will snap off when pulled before it loosens from that contaption. Shrink fits usually grab with so much force that you have to destroy something to get it undone.

DR
12-05-2013, 04:16 PM
Drill a 1/8" hole in the end, or possibly very slightly smaller. Cut off a piece of good quality hex wrench and grind the end flat. The hex wrench is now a broach. Press the broach into the material to form the hex socket.

Figure out some way to remove the broach from the hole. Do that before pressing it in, it'll be in there tight taking a fair bit of force to extract. Extracting the broach from the hole is the hardest part of this job.

In my shop we make some special wrenches in this way. Except we either grind or buy the broaches that are made of HSS for long life.

The rotary broach can't go that deep and it's an unnecessary expense for such an easy job.

Jono
12-05-2013, 04:45 PM
I think duckman's on the right track except I'd use a long 1/4" socket setscrew instead cos they tend to have deeper sockets and there's more to grip for turning the threads off. Silver braze it in with a clearance behind.

coalsmok
12-05-2013, 04:59 PM
If it is just to hold the shaft to allow adjustment of a nut does it really need to be that deep?
Seems that for a 1/8" Allen key ~1/4" would be plenty to twist the wrench anyway.

JoeLee
12-05-2013, 10:19 PM
.[
QUOTE=DR;889697]Drill a 1/8" hole in the end, or possibly very slightly smaller. Cut off a piece of good quality hex wrench and grind the end flat. The hex wrench is now a broach. Press the broach into the material to form the hex socket.

Figure out some way to remove the broach from the hole. Do that before pressing it in, it'll be in there tight taking a fair bit of force to extract. Extracting the broach from the hole is the hardest part of this job.

In my shop we make some special wrenches in this way. Except we either grind or buy the broaches that are made of HSS for long life.

The rotary broach can't go that deep and it's an unnecessary expense for such an easy job.[/QUOTE]

This is what I first thought of doing as I believe I mentioned it in my initial post.
No, the hole doesn't have to be 3/8" deep, 1/4" would do.

JL....................

JoeLee
12-05-2013, 10:22 PM
The rotary broach was pretty cool, it would make a good winter project, but I need my lathe up an running before I can make one. This is the first time in about 30 years that I've had the need to do something like this.

JL................

Jaakko Fagerlund
12-06-2013, 02:46 AM
Drill thread and run in a set screw with a hex hole in it with Locktite. Done in 5 minutes and gives the function needed.

Wheels17
12-06-2013, 08:02 AM
This is the Home Shop Machinist site. November/December 2013 has an article about forming hex recesses for nut drivers. I would have expected a mention before page 3. It might work as the first step in fabrication.

JoeLee
12-06-2013, 08:31 AM
I would take this approach but the threaded part of the shaft is only 5/16" drilling and threading a hole would only compromise the strength of the shafts threads and the hex of the set screw would be small and likely to strip out. I wish it was that easy.

JL...................
Drill thread and run in a set screw with a hex hole in it with Locktite. Done in 5 minutes and gives the function needed.

JoeLee
12-06-2013, 08:33 AM
I think I remember reading that, but just can't remember all the posts I've read over the years.

JL.................
This is the Home Shop Machinist site. November/December 2013 has an article about forming hex recesses for nut drivers. I would have expected a mention before page 3. It might work as the first step in fabrication.