Questions about shafts

[andy_ck87028]

Hi All

I'm about to start drive assembly and am planning to use timing belts and pulleys.

As a result, I'll need to attach pulley wheels to shafts and attach shafts to the assembly. These are my questions:

1. is it adequate to attach a 5mm shaft by drilling a 5mm hole in a metal plate and ensure the shaft is well polished by rubbing it with emory cloth?
2. Is there a guide for thickness of metal plate required when supporting a shaft that is say 5mm in diameter?
3. If I have a mild steel shaft, is it ok to use aluminium plate?
4. how could I manufacture a collar for the shaft when I don't have a lathe but do have a benchpress drill?
5. If the 5 mm shaft is threaded along its entire length, how would I change my approach in attaching that shaft to a metal plate?

Any othere relevant points I might have missed off will also be read with much interest.

Thanks heaps in advance

Andy

[2muchstuff]

Making collars from scratch can be done by drilling a 5mm hole in a plate followed by using a hole saw to cut the outer diameter. Then drill from the outer edge in toward the center with the correct tap drill followed with a tap.

You can run steel shafts thru an aluminum plate as a bearing surface but the aluminum will wear due to the tension (pull) created by the timing belt, causing belt slippage, mis-alignment and excessive friction. Your best bet would be to use a ball bearing whenever a shaft passes thru a side plate. If not a ball bearing then at least an oillite bushing. If a bushing wears out, then all you would have to do is replace just the bushing and not the whole plate. Since your shafts are small (5mm), I would not go any narrower than the diameter of the shaft itself (5mm) when using an oillite bushing. Some oillite bushings can be gotten with a flange on one side to allow you to have a shaft collar or similar ride up against it to hold the shaft in place.

Most timing belt pulleys have a hub on them that will have a set screw or two that will allow you to attach the pulley to the shaft. Some will have been spot drilled to allow you to drill a hole thru the pulley hub and into the shaft so a pin can be inserted to hold things together.

[andy_ck87028]

Thanks 2MuchStuff

Have googled Oilite bushings and can see they are cheap as ...

Thanks for the collar tip. Had no awareness of using a hole saw for metal ... will research that.

Seems that life is now easier than I imagined.

Cheers

Andy

[2muchstuff]

If you need to make a fair amount of collars, you may want to look into a carbide tipped holesaw otherwise get a good bi-metal or high speed steel holesaw. Just remember to use a fair amount of oil to clear the chips and keep things cool, heat will be your worst enemy. If you only need a few collars then the cost of a holesaw, tap and material may be more than buying the collars out-rite.

Regarding question #5, could elaberate on it a little more? I see it as a threaded shaft, but do you want to physically attach it to something rigid or pass it thru a bearing pressed into a plate.

[andy_ck87028]

Hi 2Muchstuff

The latter. Ie assume a bearing in a plate with a threaded rod running through the bearing. Do I need to worry about that in any way with respect to wear or thread damage, etc?

Thanks for tip about the collar. I had absolutely no idea that hole saws for metal exists. Great tip....

Andy

[2muchstuff]

Andy,
If the threaded shaft slides back and forth thru the bearing then you will have a problem with the threads flattening out. The threaded shaft is soft compared to the inner race of the bearing which is much harder. Instead of a ball bearing you could use a Nylon or Delrin (plastic) bushing, saving the shaft.
On the other hand if the shaft uses the bearing for support, you can use a washer and a nut on either side of the bearing to lock the shaft in place. If there is a fair amount of play between the shaft and bearing, try slipping a piece of rubber or vinyl tubing over the shaft that is wider than the bearing and tighten it up between the nuts and washers. When done right, the nuts will compress the tubing and take up the space between the shaft and bearing. A little trial and error is used here.

[andy_ck87028]

Thanks for answering all my questions.

Regards

Andy