Gear material (Changewheels)

[MrFluffy]

Just spotted this on thingiverse, passing it along!
https://www.thingiverse.com/thing:1808219

[Norman Bain]

How about a sprocket for the blank.

Here is one on eBay.com

https://www.ebay.com/itm/391913342650

[The Artful Bodger]

I know it is infringing the cultural mores of this site to say anything positive about anything from China but in my experience the only downside of using barbell weights is the black mess when turning the skin off.

On the other hand they are very cheap in charity shops, garage sales etc etc.

[Illinoyance]

I like the idea of auto flywheels. They are made from excellent quality cast iron. Most cars and light truck have automatic transmissions now. I suspect flywheels will be hard to find in a few years.

Weights for barbells have no metallurgical requirements for the metal. Most are cast in China. I would suspect they are poor quality iron with lots of graphite. If the molds were opened too soon there will be a very hard skin. Would one really want to invest time in trying to make a gear from this questionable material?

Surely there are steel fabricators in Scotland. One could burn a gear blank out of plate, complete with lightening holes (for chucking also). Most can accept DXF files of the part. If you have a torch you could burn out the circle yourself. Most fabricators have a pile of drop ready to be sent to a scrap yard. That would be cheaper than buying new plate.

[MrFluffy]

If you have access to a scrapyard or a friendly garage, another handy source of big flat round pieces of cast iron is car engine flywheels. You would have to turn up a centre boss depending on pilot shaft hole size unless you were lucky though. I have made up bespoke for a job faceplates to swing in my lathe's gap area from sacraficial car flywheels and there's always a couple tucked away behind the lathe ready as I have a friend who when he pulls a old engine to replace it with a replacement engine that arrives with one fitted will let me take the clutch side flywheel, and who also saves halfshafts and other handy stock bits too. But then I'm one of life's natural scavengers :-)

[grim_d]

There's a home foundry supplier in Liverpool, I think they do additives and such.
I think I've still got addresses of the boron nitride supplier in the uk, or one of them
LSM metals, I think they do a lab sample size bag, couple of hundred grams of boron
You don't need a lot to grain refine cast aluminium, parts per million works.
https://www.artisanfoundry.co.uk/about_us.php
Mark

I will try and contact LMS for boron nitride. I see it's also popular as a powder in cosmetics, might be easier to get a hold of.

Apparently about 0.002% (20ppm) by weight is sufficient! A few milligrams per kilo.

I have seen artisan foundry a lot, i would like to order some degassing tablets from them despite their prices being high but the only available shipping option available to me is £20!!

I've received your message, I'll come back to you later on as right now it's time for bed!

[boslab]

There's a home foundry supplier in Liverpool, I think they do additives and such.
I think I've still got addresses of the boron nitride supplier in the uk, or one of them
LSM metals, I think they do a lab sample size bag, couple of hundred grams of boron
You don't need a lot to grain refine cast aluminium, parts per million works.
https://www.artisanfoundry.co.uk/about_us.php
Mark

[danlb]

I still want to add boron to the other stuff but the only source of it I can find is in health supplements, not sure if suitable, not much to lose by trying though

You can find borax ( sodium borate ) as a laundry cleaner. I'm unaware of what brand names it would go by in Scotland. Here it's Borax, Boraxo, 20 mule team Borax and other brands. Often used as a flux in metalworking.

Dan

[grim_d]

Grim,

In the USA most towns and cities have cast iron covers in streets and near sidewalks for access to water shut off valves and other utility services. If you pay a visit to the water or sewer department with a case of beer you might come away with an old discontinued or damaged cover. I have a water shutoff valve cover about 8" in diameter that will become a small lapping plate one of these days. I found it in the ditch in front of my house. It must have fallen out of a city truck because we are all on privates wells and septic systems where I live.

No chance. Around here you can't even take things from the dump. Because health and safety. Councils are terrified.

I've just had a thought though, I do have a bunch of cast aluminium, gearbox housings and the likes that will likely cast better, I'll give that a try!

I still want to add boron to the other stuff but the only source of it I can find is in health supplements, not sure if suitable, not much to lose by trying though

[nc5a]

Grim,

In the USA most towns and cities have cast iron covers in streets and near sidewalks for access to water shut off valves and other utility services. If you pay a visit to the water or sewer department with a case of beer you might come away with an old discontinued or damaged cover. I have a water shutoff valve cover about 8" in diameter that will become a small lapping plate one of these days. I found it in the ditch in front of my house. It must have fallen out of a city truck because we are all on privates wells and septic systems where I live.

[Paul Alciatore]

Your lack of local suppliers sounds like a real challenge. Perhaps you could look for a water jet or laser cutting facility that can cut your blanks from sheet/plate. Let them worry about finding the stock to cut them from. As for alloy, I would look for a leaded one, at least for my first attempts. And they may even have some drops laying around that they can cut them from.

[danlb]

Please note the addition to my post. 7075 is NOT weldable due to micro fractures. Castable alloys tend to have high levels of Si as well as other traces.

[grim_d]

May I recommend that you get an alloy specifically for casting? 7075 is known to be "not weldable" due to micro fractures. I suspect that's what is happening when you are melting and casting it.

Info on castable alloys.

https://www.dynacast.com/aluminum-die-casting

https://en.wikipedia.org/wiki/Alumin...oy#Cast_alloys

Dan

Possibly, I do know 7075 isnt ideal for casting so i have tried using other types such as 6000 series with the same problem, grain refinement seems to be what I need to investigate.

I suspect that by the time I obtain enough proprietary aluminium for casting I would be just as well buying a peice of plate!

I have read that adding boron to cast aluminium can help tighten the grain structure...foundry's use bars of titanium-boron aluminium for this, but obtaining a small peice for hobby use is seemingly impossible.

[danlb]

May I recommend that you get an alloy specifically for casting? 7075 is known to be "not weldable" due to micro fractures. I suspect that's what is happening when you are melting and casting it.

Info on castable alloys.

https://www.dynacast.com/aluminum-die-casting

https://en.wikipedia.org/wiki/Alumin...oy#Cast_alloys

Dan

[grim_d]

Grim, I realize you are in Scotland, but there must still be some Screw Machine operations or vendors around.
They have beautiful blank steel or cast iron rounds up to 10 inches in size that can be quickly cut into gears without any prepping or refacing. The material is superb
see this example
https://www.sommatool.com/catalog/ac...cam.blanks.asp

Rich

I certainly don't know of any. Nobody wants to sell to the public!

Don't you have mail order suppliers somewhere in the UK or Europe?

Sure, if I want to pay more in shipping and tax than the material costs, which I won't do.