Making gear wheels

[Matty F]

A laminator has plastic wheels to drive the rollers that pull the lamination pouches through heated rollers. If somebody puts something in that's too thick, the wheels break. I have no idea if spares are available, but probably not on a Sunday.

I wasn't sure if epoxy would stick to the wheel but I repaired it anyway. But I'll bet the repaired tooth breaks soon - they always do.

Since everybody will tell me that I can't make gear wheels I thought I would see if I could. We have no indexing head or anything to make gears with, so I cobbled up a holder using the old gear wheel which has 21 teeth. If it had 16 teeth I could have made an indexing plate. But how do you space 21 holes around a circle?

Here's the broken gear wheel on the left top, and after I repaired it with epoxy resin, at bottom left.

the right is the piece of plastic that I turned up on the lathe, and after I cut the teeth in it using the mill. I considered using brass but I found this black rod that seems to be some exotic very strong plastic. I couldn't find any suitable cutters so the teeth are the wrong shape. It doesn't seem to make a difference to the horrible piece of engineering that it's going into, the one that broke in the first place. The gears still go around OK.

Here's the setup in the mill:

discovered that the holder in the mill has to be very accurate. The hole in the middle of the gears is 7mm and I don't have any bolts that size and I didn't want to stop and make one. So there was too much slop. Now I think I need to buy an indexing wheel for next time!

[Skipweasel]

I've had success sometimes making a single metal tooth and melting it into the original nylon gear.

[Chris Wilson]

Skipweasel wrote in news:MPG.27cb91c6ea5a3ebe989944@85.214.73.210:

The first thing I'd try in a case like this would be to bodge on a new tooth then use it as a pattern, make a mould and cast a new one - white metal or resin ... probably resin. And give that a go.

[Dave Liquorice]

Looks suspiciously like a lego technic gear apart from the round hole in the middle rather than a technic spline.

[Andy Dingley]

21 factorises as 3 x 7

Many gear heads are reduction gear driven through a worm. This is usually 60:1, as that has plenty of useful factors (2,3,4,5 etc and their multiples)

The dividing disk on the worm shaft needs to have the necessary primes on it (you aren't getting them any other way), so there will be a 7 ring on it (probably something that's a product of 7). If it is just

7, then you have to count 20 clicks (or 1 click less than 3 whole turns).

If you have a milling spindle for your lathe (or for plastics, make a Dremel mount), then you can use the changewheels to do division.

[Matty F]

innews:MPG.27cb91c6ea5a3ebe989944@85.214.73.210:

What would you use to make the mould?

40 years ago I used to make RTV moulds and cast epoxy in them. I've not got around to getting the moulding material. There is a shop that sells it near here.

[Thomas Prufer]

Not relevant to the gears, but a clothes iron will laminate around and over thicker items, given a little experimenting with time and temperature...

Thomas Prufer

[Nightjar]

I would look at these people's range for a metal replacement:

Bignell

[Jules Richardson]

Yes, or key them into the original gear and glue - the gear for adjusting the height on my freebie camera tripod had around 1/3 of the plastic teeth stripped out, so I re-made using aluminium.

[Jules Richardson]

Yes, or key them into the original gear and glue - the gear for adjusting the height on my freebie camera tripod had around 1/3 of the plastic teeth stripped out, so I re-made using aluminium.

[Chris Wilson]

Matty F wrote in news: [e-mail]:

For white metal I usually use ...

01 silicone rubber

And resin I usually use ...

Silicone Rubber

You can get the stuf elsewhere, no doubt cheaper but it's easy for me to pop into their shop, no connection except as a satisfied customer etc.