How to Make Blind Six-Sided Hole for Allen Wrench?

[GlennW]

The screw has a dial on one end, with graduations around it, and threads at the other, to go into the body of the head. In the center of the dial, there is a socket that takes an Allen wrench. I can't tell, but it looks like the socket was cut into the body of the screw. It may be that a piece of metal with a socket in it was pressed in there, but I doubt it.

Start with a Shoulder Bolt of appropriate size.

shoulder.jpg (3.01 KiB) Viewed 2819 times

True up the head OD.

True and thread the shank to the required dimensions.

Machine a disc to press onto the head and machine it to size for the dial. (perhaps the shoulder bolt has a large enough head already!)

Add graduation marks.

[ctwo]

Not sure if this was said, but how about threading the hex hole to accept the appropriate size set screw and loctite in place?

[rodw]

Just an idea, the drawbar on my Seig mill has a high tensile socket set screw (Allen key head bolt) in the end that is pinned. I assume there is a thread as well as the pin holding it in there.

[itselliott]

Have you considered not making the hex socket, rather just using a new cap screw?(stainless)? and then press fit the dial onto the head of the cap screw?

OH, I see that was already suggested a few posts up. So I guess that I would agree .

[GadgetBuilder]

A rotary broach is the usual way to make a 6 sided hole - but they're too expensive for the typical home shop.

Mike Cox came up with an inexpensive, modest effort way to make a rotary broach in the home shop,
see: http://mikesworkshop.weebly.com/rotary-broaching.html

I made one as an experiment and it worked very well. Except I made a hex the exact size I needed, expecting it to cut slightly over size. It didn't so if you make one allow a couple thou or the wrench won't fit.

[SteveHGraham]

This is all great info.

I have some half-inch S1 steel rod. My current plan is to cut a short piece that will fit in my arbor press. I'll turn down the end, and then I'll stick it in the chuck of a rotary table. I'll mount the rotary table on the mill and tilt the mill head 15°, and then I'll cut the turned part of the steel into a hex which has a 15° relief angle. Then I'll figure out how to harden the end of the hex.

I'll turn the rough form for the screw, including drilling out the hole for the hex wrench. I'll drill the first millimeter or so of the hole to the biggest diameter of the cutter, so it will act as a guide, with the rest of the hole drilled to the biggest diameter. Then I'll mount it on the arbor press, shoot some oil into the workpiece, and mash the cutter into it over and over. When I'm done I can put the screw in the lathe, machine a beveled face on it (removing the guide), cut the flanges that hold the screw in the boring head, and put threads on it.

I'm thinking I may use a piece of 304 stainless scrap. It looks pretty, and the screw doesn't have to be super tough.

The intelligent thing would be to have a raised area in the center of the screw, with a slot for a big screwdriver. It's actually a very stupid place for a hex wrench, because you don't need much torque to move a boring head, and it's easy to lose the miserable wrench. But this is becoming a quest, so I want to make the cutter.

I wish I had some tiny stamps so I could put numbers on the screw dial. I can inscribe graduations on it using the rotary table, if I can make some kind of pointy tool. I'll have to tilt the mill head again, so the point of the tool will maintain a constant depth in the beveled screw dial.

Will this work, or should I expect the usual explosion, shrapnel shower, and chemical fire?

[SteveHGraham]

Here's what I got so far.

This stuff turns for crap, but it mills okay. I used a big carbide insert to turn it, and it looked pretty awful.

I read up, and it looks like I don't have the equipment to temper it optimally after I harden it. Apparently the 550° maximum temperature of my oven is barely hot enough to achieve anything. I'll toss it in there and see what happens.

[ctwo]

Steve, I thought the end was supposed to be concave to allow the chip to pull in and curl away.

[catman81056]

Here ya go, problem solved!!!
http://www.ebay.com/itm/Rotary-Broachin ... 1c29d0f80b

[SteveHGraham]

Steve, I thought the end was supposed to be concave to allow the chip to pull in and curl away.

News to me. I don't make these every day.

I heated the silly thing until it was orange and then quenched it in oil. Then I stuck it in the oven at 300 for half an hour. It's not hard. Guess I'll have to figure out what I'm doing wrong.

[dly31]

A hex (Allen) wrench makes a decent broach if you heat the work piece red hot. You can also use the wrench for a mandrel in a drilled hole and forge the work around it with a hammer.

[oscer]

Hi Steve, I'm no expert on heat treating but I've been playing around with it a little. When you heated it the first time did you check it with a magnet before the oil quench? When the magnet has no affect it is ready to quench. I've never used s 1 though so I have no comment on the draw step.