So the plumbing shop next door threw out eight manhole covers and surround rings about 30 Kg each today and they landed in the tray of my ute. It should be decent grey cast iron I can break up for the furnace and was even thinking they could be the base of a sand muller or a pattern maker's disc sander at 25 inches diameter 0r 64 cm. Ideas for uses are welcome!.
They seem to be an awfully handy size, shape, and weight. I’d tuck a couple behind the bench. One day you’ll need some ballast, a form to bend some steel, or a ….. manhole cover, and you’ll be glad you have them! Pete
I am thinking a larger disc sander would be good, have to be lower RPM's under a thousand or so. Maybe too heavy for a muller/sand mixer. It's not enough to prompt me to build a network of tunnels under the property and use it for a hidden door (unlike Jason ). Could make a neat BBQ hotplate once the tar is burnt off....imagine searing the word "Sewer" into your steaks.
I have often wondered if manhole covers were grey or ductile. From an engineering and safety point of view, ductile would be the better choice. The question will be easy enough to answer. A few sharp blows with a 10 pound maul on the central ring should cause a good-sized break in the ring. If not, you may be working with ductile. Breaking them up will involve deep (probably at least half way through) scoring cuts with an abrasive saw and some mighty good hits with the sledge. Ductile is a whole lot more work to break but makes fine feed stock for grey iron casting. I use ductile returns exclusively for my castings. Even though I do not add magnesium to the melt they still show some trace of ductility in that they will often yield a bit before breaking. Denis
Im thinking those would be ductile due to size and weight it would need to support. We make some covers and bases for Vestal out of grey iron but they are small and not meant to withstand much weight.
https://www.usfoundry.com/usfoundry/engineering/specifications/ https://www.iron-foundry.com/astm-a48-class-35.html V/r HT1
The good news is that it doesn't really matter if it is ductile or grey iron...you can still melt it and use it as grey iron. The mag will fade out during remelt if it is ductile. In order to remain a true ductile iron the melt would need an alloy addition to boost the mag back up. So either way you are good! If it is cast it will be easier to break and make it fit it in a crucible..if it is ductile you may just need a bigger crucible.LOL
HT1 has the right idea: It's marked "complies toAS3996-2019" and "Class B sealed" which according to the standards is a nominal wheel loading of 2670Kg or 5816 lbs. Mainly for private residential use https://www.mascoteng.com.au/technical-support/load-ratings-as3996/ and I hadn't considered if it was ductile or grey iron. It can't be much worse than the ventilated brake rotors I use now that need a few groove cuts with the angle grinder (as Denis mentions) to break up.
Thinking more about it, some covers are actually marked as Ductile—-Neenah Wisconsin foundry makes ductile covers as an example. Covers poured in India are often poured using a huge cupola and are clearly grey. I am betting on ductile for the ones pictured in post 1. That is based on thier minimal ribbing. I think Mark will be sporting more muscle after cracking these babies! Denis
There's one of those "Extreme" gyms across the road from my friend's foundry where they hit tractor tyres with sledgehammers for an hour or so. I should see if they'll do it for training purposes of course.
So, Mark. Have you taken a whack at the covers? Do they break or just ring luoudly and smile mockingly at you? Denis
I'll have to give it a whack today and report on the results. According to the specification they are for residential use and light vehicles only, so may be grey iron. Edit: Gave the underside three good belts with a sledgehammer and all the blows bounced off with just a few bruises on the surface left behind and no obvious denting of the material or any hint of cracks. I'll definitely use one as the base for a new furnace build as the diameter is ideal.
