Shaft adapter ( are rigid ) and couplings ( these are flexible ) may well be one of the more useful parts you can make if you like to use a lot of salvaged parts, as its really useful when you need to match up old electric motors with old pumps and gearboxes etc. If you are like me you often need a 12v dc motor for devices that can also use battery power and you get really nice surplus items that have 125v ac motors on them that are really difficult or expensive to run  on battery power. Sometimes one shaft is metric and the other is not to add to the problem . While I do make some solid shaft adapters , shaft couplings could make more sense on the power input side of a gearbox as electric motors  run fast on this side and the torque is at its minimum. Couplings allow you to get away with less precision  and that is also a real advantage when trying to mount the motor.

  One thing I did learn with making these, is if you plan to do this sort of thing often or are just concerned with a few different diameters, it may actually be a big help just to have a solid piece of shafting machined to different diameters, so that your adapters could be woven directly onto it and then the metal shaft can be removed and reused later. Perhaps having it go from 1/8- 1/4- 3/8 - 1/2 inch and etc. This could become a bit demanding however if you might also need all of the different metric to non metric combinations as well.

   One of the most likely  types you can consider  making is just a simple  small piece of rubber  tubing that will fit onto the ends of your shafting and if necessary you could build up the diameter  of the smaller shaft with a smaller  piece of tubing to increase the diameter of the smaller shaft to fit the inside of the tubing  on the larger shaft . This can have a few disadvantages in that many types of rubber are not always all  that durable over long periods of time,  and or depending on what it is exposed  to, and you may have some trouble without set screws to secure it . You could try some approaches such as hose clamps on the larger  shafts, but for very small  ones , you might decide to experiment with making  miniature versions of hose clamps or by a similar  way  that I describe in this booklet later on  about how to make set screws for shafting .This can however possibly cause a counter balance problem, unless you account for this, and it really might not be much of a problem on small motors, however it often doesn't help to have exposed pieces that can catch or strike other objects .Or  you can just wrap it tightly with  wire or  fibers , seams reasonable to consider using crazy glue here rather than  the cheaper resin, after all the small amount of fiber used wouldn't require much of the expensive glue and this way you can save time .   Do however remember to keep in mind the different immunity to moisture with crazy glue has , as you may chose not to use it for this type of reason .

 The  shaft coupling shown here are based on ones I
 have made using old stainless springs I got from aluminum door hinges but don't forget to look into making your own springs sense it really is easy to do, for example just carefully wrap stiff wire of the type used in springs around a smooth shaft . Yes you can also make your own springs in composites with carbon fiber and fiberglass, vinyl easter is about the best with  fiberglass . Fiberglass have been used in commercial springs and you could experiment using the greased threads of different types of screws to create these types of springs.
 Drawing below is based on after I put mine into small roller molds I made previously to give a better look , and as with other parts I used a small piece of modeling clay to cover the top of the tiny set screws as they needed to be short to fit the roller molds, so they could be easily accessed after the resin hardened. Good to use a magnetic material here to make finding them again easier.


Drawing a is just the bare part showing just the piece  with the  fiberglass strands that hold both the  set screw  ( better  details later) and also wrapping over the ends of the spring , I bent the part of the spring that is to be inside the fiberglass so that it is securely hocked into it well  . I always start with a screw that is  long enough to go above the fiberglass strands so that when it is removed you can use a lower screw without the need for drilling  and always remember lots of grease . The drawing also show's the greased shaft  that is to be removed later  . This is to be put into one of the jigs shown elsewhere, so that the opposite shaft " quite often of a different diameter" can be mounted with the extra accuracy that jigs make possible .

 

    You would need to later slide the whole thing over so that the other end of the spring will fit over  to where the other shaft end will be, unless its to be used on 2 pieces of shaft that are the same size , in that case you would only need  to continue and finish the other end . I do sometimes prefer to use grease just to hold a layer of   aluminum foil  onto the whole shaft before I start construction, as this makes for a very good mold release and  because I sometimes prefer the extra tolerance  it gives me so parts that are not so tight fitting , after the aluminum foil is  removed, as with lye or acid , its then easier to remove and reuse the part . If appearance is important I have placed the wrapped ends into roller molds I have made previously as shown above . While not as good , its also possible to use pieces of old rubber tubing that has been cut lengthwise and greased so it can be placed like a jacket over the piece with an epoxy putty under it,  over the piece to give a reasonably smother and finished result .You can also cover the spring with a  thick jacket of rubber  tubing, made the same way to help finish the inside edges and just file or cut off the outer  ends .
   Should you plan to use this in high speeds it may become important to consider counter weighting  your set screws, this could be helped by having an extra one of the same set screw on the opposite side done in the same way . Also do remember that if you make a solid shaft adapter  you will need for  your fibers to be placed so that they go somewhat lengthwise and possibly angled both ways . You could consider doing this all  in the one way if  you knew that your adapter  is to only be twisted in only the one way ,  you  could then consider winding  your  fibers to take the most advantage of this  . However  on couplers your  fibers only need to be wrapped on  , much like string on a spool , with its main strength mostly only  to hold the set screw and ends of the spring together but with solid shaft adapters your  strength requirements are different .
 
 


                                   2 types of shaft adapter jigs that I have not shown are
   1  I have made by using telescoping tubing but this doesn't give much choices when making adapters for going from metric to non metric shafting and you may have to except that tubing can have some looseness that means it may not be exactly centered . Tape could be used however to build up one side or oil less bearings when ever you can find the right sizes .
 2 It could be most ideal for shaft adapters if you plan to make a single  shaft to have continually lesser diameters
but this might require a machinist to cut down a metal shaft but could be very convenient for as a simple mold or jig to make lots of different adapters from . I have never tried this but remember a drill that used to be designed along the same idea of multiple diameters , it would drill a small hole at first and then  would allow you to continually drill larger holes as needed .
   3 You can consider using different variations of  for example , 2 shaft adapters on the ends of 2 pieces of the same type of shafting and then mount these end to end  , in one of the jigs shown here . I haven't tried this one and of course you may need to get or make the adapters first especially if they are odd

Before I start wrapping fibers on I usually first need to place the nut and screw to serve as a set screw . I have found that very fine wire from old transformers works well but I will sometimes use crazy glue and kevlar strands as the glue works really well and fast on fine fibers and with it you can create a rather strong perform . Do remember the importance of using lots of grease on the threads of  your nut and screw, and perhaps make a point of saving really tiny nuts and screws for this as sometimes you might need the really tiny ones his  view is just to give an approximate idea of how the wire is wrapped on to hold the nut onto the shaft before the fiberglass strands are to be built on

 Sideways view showing how the round objects
 set in an epoxy putty on an angle rod  This method  assures that everything remains in the same angle each time it is removed and then placed back into the angle rod . Its usefulness is for the jigs below as well as to sometimes mount motors.


 

                                            SHAFT ALIGNMENT
 One of the things needed for making shaft adapters and couplings is a way to align up the shafting and I have tried 2 ways to do this .One way is to use 2 drill chucks scavenged from  old drills but for some reason some of the chucks I tried gave less precision than others . To use these find a good piece of short angle rod  that you find is reasonably precision  and attach both  drill  chucks to a piece of precision shafting . while both are attached make a putty of epoxy and mount on the angle rod while both are attached so that when the epoxy hardens and with the angled part of the angle rod they will re align to each other when the precision shaft is removed . On  mine after this molding process I just use plain old electric tape to hold them in place but hose clamps should work good to .Do remember to avoid any tiny bits of dirt or bumps on the angle rod as they will degrade precision


To make this type of jig you again need a short piece of precision angle rod but because welding and other methods might cause a loss of precision , I made mine by taking a piece of U shaped metal and by using the epoxy imbedding with an epoxy paste similar to what I did with the drill chucks , with rather good results . I  also preferred to use screws to attach the angle rod on to the support as I did not trust the epoxy bond to be reliable enough , and put in the screws after the epoxy has hardened to prevent stresses that otherwise might cause distortion without the solid epoxy underneath .Of course the screw heads should be sunk under the surface of the metal .
   This drawing is the finished jig with its middle removed to give you room to work , and with the smaller shafting wrapped with tape to increase its diameter to match the larger shafting . I usually prefer to use modeling clay to hold them in place but you should be able to use wire or tape . For extra grip try using pieces of wood or other material to extend the surface of the shafting so that tape or maybe hose clamps can more easily grip the shafting in places that wont tend to bend the shafting


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