shop made knobs

[darryl]

Here's a simple project I did today to make some knobs. These are threaded so they will tighten up on a bolt to secure things. They can be bought pretty cheaply, but not if you don't want to leave the shop. The material I used is pvc, reclaimed from scrap pieces of 2 ft diameter water pipe. Cut into pieces, heated in the oven, flattened, etc, to become a useable material. Bla bla bla. I table sawed enough cubes to make 15 or so knobs, even though I only need about five right now. I drilled and tapped a carefully centered hole in each one.
Anyway, from the top left and going down: first image shows some completed knobs, some blanks, a jig, and a deburring tool.


The jig is just a piece of scrap to hold the pin, which is 3/16 diameter to fit the pilot hole size for the 1/4-20 threads in the blocks. Bottom left pic shows the jig positioned as it is used. Top right pic shows a block on the pin, positioned up agianst the square and with the pin brought up against one side of the t-slot. Note that the jig itself doesn't touch the square. Obviously, some hardware is clamping things in place. The hungry endmill hovers just above-
In the next pic, two sides of the block have been hollowed. I haven't shown it, but I put two pieces of tape on the downfeed handle area to give me a reference point to stop at, so I could get the depth of each cut the same. I snugged up the quill lightly and used the drill press handle to feed the endmill. This pic also shows more of the square I came up with to give me reference edges to work with on the mill. It can be bolted down in each t-slot, so it becomes very rigid- the center slot is being used here to handle the clamping hardware.

The final image shows the stub on which I mounted the blocks for final turning after the millwork. The nut is there to prevent the knob from touching the chuck jaws. This prevents the knob from skewing as it tightens on the stub, thus allowing the knob to run true to its threaded hole, which is good for facing the ends of the knob.

The deburring tool is just a piece of bandsaw blade with a few different curvatures ground into it. Every now and then I put a regrind on them to keep them sharp. It's easy to drag across a sharp edge to leave a very slight roundover. I use this on aluminum and steel as well, it does a good job.

[Deja Vu]

Nice! ..that jig looks like a blue version of the relatively stable composite decking material i use here. ...but probably not related.

What materials are those?

John Bloy

oops I guess I posted before you were complete with the text...

[darryl]

Here's a close up of a knob ready to turn to diameter.


I used a 3/4 inch endmill, which leaves a reasonable space for my fngers on the knob. I didn't pay a whole lot of attention to detail- they're just knobs anyway, so if the center hole is off a bit, it don't matter
What else- the pin is made from music wire, the holes are tapped right through and deburred- I may turn a shallow recess on one end of some to hold a washer in place for those knobs where I don't want so much friction where it tightens onto-
Now I can get back to my camera mount project. Pics of that when it's done

John, ever since I discovered that I could heat pvc in the oven and mold it, I've been bringing home pieces of scrap water pipe from construction sites. The material I'm using here started life as 2 ft diameter water mains. This stuff is over an inch thick, and grows a bit in thickness as it's heated. I had to skilsaw pieces out of the pipe so it was small enough to fit in the oven. Once it's rubbery enough, I set a piece on a flat surface, cover it with another flat surface, and add lots of weight on top. Once cooled, the resulting slabs stay amazingly flat. I've never had a problem with stresses warping something that I turn in the lathe, etc.

I should add a suitable warning about pvc- it's possible and probable that harmful components are produced through the heating and machining of it. The same probably goes for a lot of plastics, and some metals, I'm sure. Want to experience a bad one? Burn a fiberglass epoxy circuit board in the shop (ah, no, don't do that) . Common sense is is a pretty good tool to keep around the shop.

[chiphead42]

FYI Various bottle caps filled with JB Weld, drilled & tapped, make
good knobs also. Many sizes & shapes. Cheap & easy. chiphead42

[Alistair Hosie]

That looks amazing I am very surprised you don't get some air bubbles trapped in the mass as you fold it it looks very professionally done.Alistair

[Mcgyver]

I am very surprised you don't get some air bubbles trapped in the mass as you fold it it looks very professionally done.Alistair

you're loosing me on that one, what folding?

darryl, nice job, i haven't machined pvc - how does it cut? about the warning, is this a generic comment or is pvc known to be particularly nasty? i remember reading somewhere about the dangers of fumes from plastics at high temps being a reason diy injection molding held some challenges, but i don't know very much more about it...i'd guess your softening is at a lot lower temps.

[Alistair Hosie]

The material I used is pvc, reclaimed from scrap pieces of 2 ft diameter water pipe. Cut into pieces, heated in the oven, flattened, etc, to become a useable material. Bla bla bla.


that folding action or building up action of several layers.Alistair

[Mcgyver]

i see what you mean, i don't think there's any layers or folding though, the stuff was 1" thick, he said flattened it so i took it that it was a heavy enough section he flattened with heat and cut into cubes

[Alistair Hosie]

whatever it turned out beautiful.Alistair

[Dick Plasencia]

I've got a question on the pvc. Can it be cast? There may be some application where I could use a larger blank than can be had from a piece of scrap pipe. So I was thinking this would be good material if it can be melted and cast into a block of whatever size is needed.