Gray vs. Ductile iron for scraping tools

Hello all,

From what I see and read, gray iron seems to be the preference, but would ductile iron work as well?

I ask as I'll be doing a job for a friend in the construction trade and he has a lot of manhole and city utility covers that he's willing to cut up for me. It seems that they're primarily gray iron, but it made me wonder.

I'd like to make some surface gages, bench blocks, tool maker flats,other random tools,etc. Maybe even a small straight edge for working on my small hobby machines at home, or even a new compound for my bench lathe.

I suppose ductile iron would be a little harder to scrape opposed to the gray?

Am I crazy for wanting to make tools out of a sewer plate?

Corey

I think you may find that the manholes are made of junk iron, idk, maybe not because the manholes are subject to vehicles driving over them.
I myself have been looking for cast iron I can repurpose for scraping. You could always get one to test, see how it cuts, you may be able to tell the quality just by watching the consistency of the saw cuts, watching for hard or soft spots.

I have tried Ductile when making Straight-edges and it reminds me of scraping steel. Small slivers and burr's. I now make them out of close grained gray Iron 30 or 40 grade. Those man hole covers I would think have been stress relieved quite well... how old are they??

Not too sure, but I know everything he's offering were used for a while and replaced with new ones. One would assume a sewer plate has a pretty long service life? They're from "the greatest city in the world" so they were well used and subjected to the 4 seasons, so I'd say your probably right about them being pretty settled Rich.

Judging from what I read off of manufactures websites, the standard for manhole covers seems to be gray iron, with ductile being a premium. Being from such a city, could they be premium? Perhaps, but going off the number of them needed for such a city, id say there gray iron.

Rich, how well did your ductile straight edges hold up over time? Maybe being tougher than gray iron, they'd wear better? How about dimensional/thermally stable?

I sold them and have no idea. I just hated scraping them.

I thought that they would wear better too, but the extra hassle and slivers in your fingers is not worth it. Once you scrape ductile you will understand. Scrape some steel and you will see what I mean. Rich

Richard King said:

I sold them and have no idea. I just hated scraping them.

I thought that they would wear better too, but the extra hassle and slivers in your fingers is not worth it. Once you scrape ductile you will understand. Scrape some steel and you will see what I mean. Rich

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Interesting. Many of the older high end planes like Norris', and Baileys used ductile or malleable iron, They seem to cut fairly smoothly, although with chips, not dust.

dee
;-D

Bailey planes are actually Stanley. All the ones I have are steel not any form of cast iron.

Interesting. Many of the older high end planes like Norris', and Baileys used ductile or malleable iron, They seem to cut fairly smoothly, although with chips, not dust

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Bailey planes are actually Stanley. All the ones I have are steel not any form of cast iron

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Hmmmmm......

Norris made some cast planes late in their production, but I am pretty sure they were CI and not ductile. A typical or perhaps one should say "archetypal" Norris infill plane was dovetailed steel plate. I have scraped a dovetailed Spiers (who Norris copied) and the sole seemed to be wrought. It sure scraped nicely! not at all like the A36 steel plates I started out scraping on a few decades ago.

Stanley bench planes and indeed most of their metal planes were all "cast iron". That is why they break so easily. Not any kind of ductile or maleable iron, just plain old "cast iron". It says so in their ads and on many of the boxes.

The compass planes obviously had steel soles; metal plough/rebate/dado planes had steel skates; the "infill style" rabbet planes were beechwood cases in steel (rather rare to see today); and there were a few steel bodied or steel and iron block planes. But everything the average person pictures with the word "plane" was made out of CI.

Today, Lie Nielsen & I believe Lee Valley (among others) use nodular iron (ductile) and they are stronger than old Stanleys.

I've scraped a number of old planes. Stanleys scrape fairly nicely, but are probably harder (which is good for the application) than the really nice to scrape but not very wear resistant Class 30 iron many machine bases were made of.

smt

Here's my haul folks, everything is estimated pre-1970's NYC, minimum thickness is 1.5". Just playing around, seems easy to scrape and file. The main plate was cut half way with a demo saw and the rest split with a wedge. Kinda interesting to see the corrosion lines through the casting, kinda like layers in rock. What do you guys think?

Made my first piece, indicator stand out of the gas main cap. Call it "rough" scraped until August

Before I knew what scraping was I made a lot of fixtures out of a 150lb Seattle storm drain cover and 50lb weight plates, allegedly both grey iron. They cut fine enough on my shaper.

capocoreyollo said:

Hello all,

From what I see and read, gray iron seems to be the preference, but would ductile iron work as well?

I ask as I'll be doing a job for a friend in the construction trade and he has a lot of manhole and city utility covers that he's willing to cut up for me. It seems that they're primarily gray iron, but it made me wonder.

I'd like to make some surface gages, bench blocks, tool maker flats,other random tools,etc. Maybe even a small straight edge for working on my small hobby machines at home, or even a new compound for my bench lathe.

I suppose ductile iron would be a little harder to scrape opposed to the gray?

Am I crazy for wanting to make tools out of a sewer plate?

Corey

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I have a foundry owner friend here in Bellingham who has mentored me as I have set up my own small foundry for casting SE's, prisms, and eventually other related equipment. He is the 3rd generation to own this family business. His company has cast thousands of manhole covers over the years. He reports that they put everything including the kitchen sink in the furnace when making low-grade stuff like manhole covers and were not too particular about what "grade" of cast iron they made.. So the mix could vary from one batch to the next. It could be that one cover will machine well and be great to use. The next one might be hard as can be and have included slag, carbide, etc. The other thing that might make a big difference from one cover to another is how the casting was handled after pouring. If it was immediately shaken out of the sand it might again be terrible to machine. If it was part of a big batch at the end of the day and they just left the casting in the sand to the next morning it will have been pretty well stress relieved and certainly not hardened.

One thing is for sure, you can not beat the price and by cutting into the casting with the saw you immediately get valuable information about the iron. If it cuts easily with the saw (I am assuming form the pics this was not an abrasive blade cut, or was it?) and breaks with a fine grey grain, you should be in pretty good shape. I think if I were dealing with unknown hunks of iron like that, I might try to stress relieve them after cutting them up and rough machining. If you have a friend with a ceramic kiln and programmable (most are) thermostat, just put the pieces in the kiln and ramp up the temp to 1050 or 1100 F hold them for a couple hours and then let them cool slowly over 8 to 12 hours. Pretty easy to do and gives a little piece of mind. The cast parts were almost certainly never stress relieved after they were cast. Thermal stress relief is the most certain and well accepted way to relieve stress.

Denis

If you believe vibrational stress relief works, you could hypothesize that the manhole covers have been whacked by rubber tires for years on end. You'd have to ask the sewer rats if they were ringing.

TG, I will be teaching a class in Nowata OK again in October. Nick bought a new building with AC. He wants me to teach a few of his new rookies. Plus I am selling a few outsiders... If you can get away your invited N/C as you have attended enough now and you can help teach.

You have such a great demeaner and your longtime experience is helpful in the classes. Oh and Cory (capocory) is head of a toolroom and is one of the best scrapers I have taught. He turned a Rungfo into a jig bore in my Boston class. :-)

chevydyl said:

I myself have been looking for cast iron I can repurpose for scraping.

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When I have needed a onesy piece of cast iron, I found that barbell weights were cheap and usually decent quality. Don't know about scraping but they usually machine pretty well.