Intro: Quick Knobs
I earlier posted an Instructable about making quick adjusting nuts called Lock Blocks. They were made of hard maple and pretty easy to make once you got the hang of it.. The feedback I would get back is that people strip them frequently. I commented that they are tightening them too hard (Tight is too tight). So I decided to make some from aluminum.
To minimize the metalwork I decided to buy blank four prong 2" knobs. I found the following source on the internet for knobs
Twelve of them, including postage, cost me about $52. I just received them in the mail and they are beautiful. They anodized, well finished and esthetically pleasing. I got them from an excellent company with exceptional customer service. Tell them Dave sent you. My only association with this company is as a customer. Mention this Instructable to let them know what a economic power Instructable.com can be.
Step 1: Quick Knob Theory 101
A Quick Knob is made from a standard blank 2" knob with a ⅜-16 threaded hole in the middle. The another ⅜"hole is bored at a tilt of 13.5° (13.463°). This removes most of the threads except for one side at the very top and the opposite side at the bottom. This allows the block to slip down the threaded rod and only lock into place when it hits a hard surface. Please view the included 8 second video.
Step 2: Scribe 5/8" Circle
These knobs have centers marked on their bottoms. Use the center mark to start drilling a hole with a ⅝" brad point drill. Stop when a ⅝" diameter circle is lightly scribed on the knob.
Step 3: Drill and Tap the Center Hole
Using the same center mark, drill a 5/16" diameter hole through the nut. Then thread with a 3/8-16 tap. I find it easier to mount the tap in my drill vise and turn the knob to thread it. Make sure you get a tap with at least 1¼" of thread cutting length.
Step 4: Make Angle Blocks
Now you can use a miter saw to cut a 13.5° angle block but it is hard to get an accurate angle. Historically woodworkers did not have protractors so they would express an angle as the ratio of the two values of a right triangle. As an example, a triangle that is 1 unit high and 4 units long is fourteen degrees. Woodworkers would call it "1:4". (A useful fact, 1:4 = 14 degrees)
A close ratio for 13.5° is 6:25 (13.496°). To make angle blocks I take the cutting cradle for my table saw and mark a reference point and another that is 25 units to the right and 6 units. up. I them take a straight stick and tack it so it touches both points. With normal layout techniques, I can keep the error well under a 1/10th of a degree.
The knobs are a little wider than 1½". I made the block from 1½" thick MDF. Since I didn't have MDF that thick I glued three ½" thick pieces together. After letting the glue dry a trimmed the block to a 4" width. A nice piece of 2x4 would work if you don't have any MDF.
Laying the block on the angled reference allows you to make the angled cut. Move to the reference face of the cradle to make the square cut. By switching back and forth, you can make as angle blocks as the your length of MDF allows. You will drill into these blocks and the will get used up. This is know is an investment fixture because you have to pay for new one occasionally. (If you make ice in a cube tray. that is a fixture. If you make ice in balloons, that is an investment fixture.)
Step 5: Bore Angled Hole
Put the angle block into your drill vise and place the knob, upside down, on top of block and close the vise to clamp it into place.
Place the 3/8" milling bit into the drill press and align the vise so the side of the mill just touches the prescribed ⅝" circle. Firmly clamp the vice to the drill table.
Slowly bore the angled hole. Cleanup rough edges with a small file when done.
You have now completed a Quick Knob.
Step 6: Quick Knob Building Kit
I decided to combine all the tools together into one box so I can make these knobs anytime I want. When you friends see them they will want you to make them some. If you are lucky, you can just lend them the kit and let them build them themselves. Rental price? A beer! Cost to make them? They buy the knobs and a beer for each one I make.