Instead of using hex nuts and wrenches, allen keys and cap screws, I use lock handles as much as possible and have made quite a few of them for my tool posts and other ancillary attachments for my Taig lathe.
At first I simply used a short cylinder as a head, tapped at the bottom with a hole appropriate for the purpose for which the handle is made, drilled a cross hole through the top part of its body, and inserted a short length of thinner steel rod (say 5mm) into the cross hole as a lever. This works well but it looks rather crude and is not quite ergonomic. So I replaced the cross rod with a tapered handle tipped with a ball to give it a better look and feel, and angled up by a few degrees to be more nicely held.
I made the first few without any plans or set dimensions and just improvised on the go. I find it particularly difficult to attach the handle to its head, especially when it is also angled up and not stand at right angles to the wall of the cylinder. The resulting handles vary in quality and size. Several did not even pass my very lax visual inspection and had to be discarded.
This Instructable explains how I standardized the process with the help of a drilling guide.
I have no machine work training and I am unfamiliar with industrial jargon. You have to excuse me if I cannot make myself clear or have used the wrong terms to describe things. Better still, give me your comments and corrections in the comments.
Step 1: Design
The Lock Handle is made up of two parts, namely a cylindrical head and a tapered lever with a ball tip. There is a variety of designs which I have seen on the internet. The choice boils down to personal preference.
For me, a cylindrical head measuring 15mm tall and 12mm in diameter is good enough for most purposes. It is tapped to #10-32 (standard for the Taig lathe) for about 5mm in depth at the bottom. Dimensions are not critical and may be varied to suit. I also have some measuring 10mm x 10mm with an M4 thread.
A hole threaded to #10-32 is drilled across into the cylinder wall 7mm from the blind end. This hole is not perpendicular to the cylinder and is angled 15° towards the blind end. The angle is empirically chosen; larger or smaller is also fine.
The tapered lever is about 40 mm long (not measuring the attachment threads) turned from an 8mm mild steel rod. The ball tip is 8mm in diameter and the rod is tapered from 3.5mm in diameter at the ball tip to 8mm just next to the threads at the attachment end. Beyond the taper, the lever is turned down to 4.5mm and threaded to #10-32 for about 5mm. I find that if the lever is too long it takes up too much room, and if it is too short there is not enough leverage for tightening.
The threads on the lever mates with the inclined hole in the head, allowing it to be screwed in securely.
The threads on the bottom of the head turns it into a nut for locking whatever needs to be secured on a jig or some other part or attachment of the lathe.
Step 2: Handle Head
A short length of 12mm steel rod is used as the blank for the head. Only about 15mm at the end is finally used. I cut an initial length of about 50mm to allow for chucking. This is later trimmed to size.
In order to drill the mounting hole for the lever properly at the correct angle I made a drilling guide. This is basically a block of aluminium with a 12mm hole drilled through it, inclined at 15° angle from horizontal. Another vertical 12mm hole is drilled from the top at right angles to horizontal, to reach into the cross hole drilled earlier, at a location about 10mm from one side. A 12mm steel rod with a 5/32" guide hole drilled through is inserted and secured with a grub screw through the aluminium block. This serves to guide a drilling into the side of the handle head at the proper angle. This guide rod is contoured to meet the head neatly for clean drilling. The drilling guide is either clamped onto the press drill vise or onto the milling attachment for use.
The 12mm steel blank is inserted into the cross hole, with one end just flush inside the entrance hole at the higher end. The drilling guide is put under the drill press with a 5/32" bit in the chuck. This bit runs straight in the vertical guide and drills a hole in the wall of the handle head, to a depth of 7 to 8 millimeters.
Removing the steel blank from the guide, the hole is then tapped to #10-32.
I put the blank into the chuck, faced the end closest to the drilled hole leaving the hole about 7mm from the end. I turned and cleaned up the rod reducing its diameter slightly. I then cut off 15mm of the rod with the parting tool.
The stub parted from the rod is turned around and secured in the chuck. A 5/32" hole is drilled to a depth of about 10mm and then tapped to #10-32 for about 8mm.
(See photos; you can get the idea generally and make your own without following the same dimensions except the angles and the size of holes.)
Step 3: Tapered Lever With Ball Tip
The tapered lever with ball tip is made from a piece of 8mm rod, 45mm long. First, 5mm from one end is turned down to about 4.3mm diameter. This section is then threaded #10-32.
I took a short scrap piece of 12mm rod, say about 25mm in length. I faced both ends square and drilled and tapped a #10-32 hole, 8mm deep in one end. Using this as an extension, I screwed in tightly the 8mm rod earlier prepared with a #10-32 thread at one end.
Placing the 12mm rod end of this joint piece in the chuck, I then marked off 8mm from the other end and from there turned down a short section, say 4-5mm long, to 4mm in diameter.
I then installed my ball turning jig (see Instructable) and turned the 8mm section at this end into a ball, with a neck of 3.5mm connecting to the rest of the rod.
With the top slide, I then turned a taper on the rest of the rod, from the ball to the end of the 8mm rod, tapering from 3.5mm to 8mm for a length of 32mm. The taper and the ball can then be filed and sanded smooth. I did not bother to polish the piece to mirror finish as I am less concerned with aesthetic appeal than functionality.
Step 4: Completion
The tapered lever with ball tip can now be attached to the head. I can simply screw in the rod onto the cylinder and tighten and leave it at that. Hower, the assembly may come loose in time, and the joint tends to look a little messy. So I decided to put some solder in the joint. The solder filled in any gaps and hides the junction. I cleaned the junction with alcohol and put some soldering flux onto the parts. A short piece of thin solder wire is cut and curled around the threaded stub of the lever before it is screwed tight into the cylindrical head. The solder is then molten in place with the help of a small butane torch.
Excess solder is scraped away, and the surface is smoothed out with a wire brush on the Dremel.
Making such a handle takes less than half an hour, and costs next to nothing.