1930 dash knob removal

[West Peterson]

I have a perfect-condition 1930 dash knob (marbelized amber color) that is stuck to a cut-off and rusted shaft. I've tried soaking the whole thing in a jar of PB Blaster for more than two weeks, but still have not been able to remove the plastic knob. Apart from cutting the shaft at the end of the plastic, and drilling the rest out, is there anything else I can try?
I've thought about soaking the whole thing in Coca-Cola (remembering my sixth-grade experiment of dropping a paper clip into a glass of the solution). Or, possibly a well salted solution... or even some type of acid. However, i do not want to ruin the knob, as it is so nice. Reproductions are no where near as nice.

[Restorer32]

You might try heating up the remaining stub gradually until hot enough to pull out, then rethread or Helicoil the knob.

[Rusty_OToole]

Are you sure it is supposed to come off? Some knobs were molded onto the shaft.

[West Peterson]

No set screw. I'm pretty sure it's supposed to scew off, but I base this on knowing that the dash-light knob screws off. The knob I'm having trouble with is for either the choke or spark, so perhaps Tom or Rick can varify its attachment.

[mrpushbutton]

perhaps someone on the forum has a broken or runied knob they can dissect and tell you how it is on there?

[West Peterson]

I guess that weather it's screwed on or molded on, I'd like to know if there is any way of eating away the metal without harming the plastic (is it plastic?).

[imported_Speedster]

The '29 choke and spark knobs are metal, not plastic, but they are threaded and screw on (normal right-hand thread). So, it does seem logical that '30s knobs were threaded also.

[imported_Speedster]

In '30 there were also plastic knobs on the 2 gloveboxes. Could it be from one of those? The glovebox knobs may Not have been threaded on to shaft, since they would have a nut on inside?

[Rusty_OToole]

I was thinking about the headlight switch knobs used on many cars from the 40s 50s and 60s. Where the knob was molded onto the shaft, and the shaft pushed into the switch where it was held by a snap ring or otherwise locked in.

Someone who did not know this might cut the shaft when he couldn't get the knob off.

Have seen this type knob, screw on knob, and set screw knob all on the same dash board.

[34PackardRoadsta]

The choke and spark knobs on my 30 are plastic, and they look screwed on. I have not tried to take them off.

You could try using galvanic corrosion to remove the metal. Place some salty water in a copper tub (3.5% table salt will work). If you don't have a copper tub than a plastic tub with a flat chunk of copper immersed in the water will do. Attach your metal post to the cathode of a 12V battery using a copper or stainless connector, and immerse in the tub. The tub (or chunk of copper) is then grounded to the anode of the battery. Current enters the electrolyte through your piece of metal, travels through the electrolyte, and goes to ground through the copper. 12V DC at very low amps will result in dissolution of 1/2 lb of metal in less than a day, so it shouldn't take long with your post.

Just don't use tin or aluminum for the cathode (e.g. bucket). You will just end up with salty water all over the floor!

Tom

[mrpushbutton]

Here are a couple of images to help this discussion along.......

[imported_Speedster]

What is the knob for, on right side of dash above cigar-lighter? Is that the Heater-switch, dash-light switch or what? The '29 doesn't have a switch there.
What ever it is, it has a plastic knob also.

[Packin31]

On my car that is the Map light.

[West Peterson]

Yes. Map light.

[imported_Speedster]

Map-light! Man, How Modern can you Get! [img]<>/shocked.gif[/img] [img]<>/grin.gif[/img]

No Heater standard, but it HAS a Map-light! [img]<>/smirk.gif[/img] [img]<>/grin.gif[/img]

[Packin31]

It is a neat thing. You pull is out in it lights up [img]<>/smile.gif[/img]

[34PackardRoadsta]

Or in my case, sparks a bit! Or it did before I disconnected the wire!

[R W Burgess]

Quote:

Or in my case, sparks a bit!

....Comes in handy for the Fourth of July Events! [img]<>/whistle.gif[/img]

Wayne