The AM Forum

I picked up a var. cap. for a project but it has a 3/8" shaft. Any idea where or how to adapt the larger shaft to a 1/4" shaft?

Thanks,

Bob
wb6kwt

http://www.surplussales.com/ShaftHardware/ShaftH-8.html (http://www.surplussales.com/ShaftHardware/ShaftH-8.html)

Third down on left. Not cheap ... but they look like quality pieces. Any friends with a lathe and drill press? Not difficult to make.

I have seen them many times on older homebrew equipment.  I don't think it is a particularly scarce item.

Yeah, what Don said. You will usually find them in vendor aisles that have all the parts in neat little bins. Or go scrounging in the boxes under the tables of the tailgaters. I'll guarantee you'll find one.

You can always find one when you don't need one!

My junkbox solution is, grab a bit of scrap aluminium of large enough size, drill a 1/4" hole though it, then using the 1/4" hole as a pilot drill a 3/8" hole half way thru. Drill and tap for some set screws (or use self tappers - if you want to be really ugly), hacksaw the shaft off a burnt out pot and stick that in the 1/4" end. 

Odds are, the next day after doing this a real adapter will appear from nowhere.

                                                               Ian VK3KRI

 

I needed a shaft coupling insulator anyway when I built my 813 rig, so I took a 1/4 by 1/4 ceramic insulated coupler (universal joint type) and drilled out one end to 3/8".  Really slick.  Only problem encountered was holding the bushing steady while drilling. Finally held it in a vise from the underside looking up through the jaws.

Thanks for the suggestions. I like Rick's idea of the insulated shaft coupler, I have a couple of those. I'll give that a try, I was going to use one anyway.

Bob

Cheaper, fasterest, dumbist:

A short length of clear PVC tubing with 1/4" ID, heat end with heat gun or hairdryer, place long nose pliers in that end, widen, slide quickly onto the 3/8" shaft (is it 3/8" or 5/16"??), place spring type hose clamp as needed, put 1/4" shaft into the other end, use hose clamp as needed.

                  _-_-WBear2GCR

PS. I have done this to put the same 1/4" hose over the outside of 3/8" OD copper tubing, no problem.

do the hard way: drill a piece of brass with the 3/8" drill halfway through, then finish it with the 1/4" drill, then drill and tap the holes for setscrews. It won't be perfect with just a drill press and a tap and die set but it works.

Try finding a 0.315 (8mm) to 3/8" adapter! darn metric stuff.

Well, while looking for my insulated shaft connector, I found the proper coupler in my junk box, forgot I even had one. Now where are those spline wrenches?

Bob

Remove spline set screws and replace with allen??

          _-_-bear

I use the lathe and make whatever is required and would be glad to do it as a last resort for those not having lathe access.
However...adapters are generally stocked at better hardware stores. You will find that 3/8" couplings  (for motor shafts etc.) are pretty common. Then go over the the hobby section and you will find an assortment of brass, aluminum, and SS tubing that is stocked in sizes where the OD of one size will fit neatly into the bore of the next size larger. All that is required is to cut short lengths of the desired size to reduce the bore of your coupler. I have used this tubing for everything from re-bushing carburetor throttle shaft bores to sleeving wallowed out HRO & KWS1 tuning knobs.
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