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Machining Cast Iron Dumb Bells

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Allan

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#1
I have collected a bunch of cast iron dumb bels on spec. I pick them up at the thrift store for a buck or less. I have used and tried to use some of them for various projects with mixed results. Some machine beautifully and others are as hard as granite. They must take them out of the mold hot and dump them in the sea. One I used recently made a beautiful face cut and not bad longitudinal cut but the angled cut was just about impossible with HSS.

One I was hoping to use was so hard that a file just slid over it. I put it in a raging fire in backyard. The fire burned 3 feet tall for several hours. I let it cool overnight in the ashes but it is still just as hard. So is there an inexpensive way with minimal cash outlay and no weird chemicals to anneal these things?
 

Bob Korves

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#2
Mystery metal is just that. The file test can help, but there are also sometimes inclusions that are harder than Hades, and/or porosity and voids. Buying known quality metal with known properties is a safer but more expensive way to buy machining stock. Most of us use mystery metal at times, test it with a file and hope for the best. Sometimes the money saved on the material ends up costing more than that in damaged machines and tooling, not to mention frustration and a finished product that is not as good as it could be. More and more, I stay away from mystery metal and try to get drops of metal stock from known sources at a reduced price or free.
 

markba633csi

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#3
The hard ones are probably a mixture of leftovers, with nickel and zinc and who knows what else in it.- probably the cheapest grade of cast iron made.
Good only for weights.
mark
 

chips&more

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Life is too short. And I want a happy ending. My main choices in life nowadays are 12L14, 1144, aluminum, brass & plastics. The days of exotic and mystery metals are gone! Unknown cast iron will be just that “unknown”. Sorry, I don’t want any part of it. Especially the hard spots that it could be hiding inside.
 
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COMachinist

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Life is too short. And I want a happy ending. My main choices in life nowadays are 12L14, 1144, aluminum, brass & plastics. The days of exotic and mystery metals are gone! Unknown cast iron will be just that “unknown”. Sorry, I don’t want any part of it. Especially the hard spots that it could be hiding inside.
Plus one here. Wasting time on mystery metal and money dulling cuters and broken tooling just is not in my time table any more. Buying more cutters and grinding down your HSS, will cost more in time and money you could use to buy needed known material.
Good luck and God’s Speed
CH
 
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RJSakowski

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#6
Cast iron come in multiple flavors. When you think about the desirable properties of of weight, it needs ti be heavy and to be able to cast into a specific form. Mechanical property needs are all but non existent. There is no reason to expect that weights from different manufacturers or even from different production lots from the same manufacturer will have the same mechanical properties.

White cast iron is inherently hard and brittle. It can be converted to gray cast by heating at around 1,000ºC for an extended period (several days) and cooling slowly over an extended period. While your strategy of heating in a bonfire is on the right track, I doubt that you can say that you held the cast at 1,000ºC for the entire time. Even if you had, the conversion process normally takes about 10x the time. The best way would be to use a muffle furnace that can maintain a controlled temperature for the required length of time.
 

silence dogood

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I have worked with cast iron weights mainly barbell, window sash, and medical scales. Found some medical scale weights that were 1" by 3" by 8" with 3 guide holes, These machine beautifully. Barbell weights, if they are bare(no heavy paint or plastic coat), pass the file test, may be okay. Even so I take the first cut on an old carbide bit to see what it will do. Window sash weights,forget it. However, they can still be machined, sort of. Just use a side grinder and figure to a tenth of an inch instead of a thousand. Still, it's not a total loss, these weights still can be used as, DaDa!, weights. Used four of the weights as a counter weight for a machine. ( they're great since the weight is usually cast right on them), Weights to hold down things as I work on them. Weights when gluing two wood panels together. Last of all weights that are put in a box or heavy bag so they won't roll around as a substitute for sand bags for winter driving.
 

Tozguy

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#8
Of the two different barbell weights that I tried one was a joy to turn. The other one not as easy but was ok. This is the one that turned real nice:
 

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jdedmon91

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#9
Life is too short. And I want a happy ending. My main choices in life nowadays are 12L14, 1144, aluminum, brass & plastics. The days of exotic and mystery metals are gone! Unknown cast iron will be just that “unknown”. Sorry, I don’t want any part of it. Especially the hard spots that it could be hiding inside.
I agree one thing that I do is get scrap drops from my local metal supermarket scrap bin. The CLT store lets us pick through them and sells us the material by weight at scrap price


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1448CW

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What do they charge per lb. scrap price? I pay $1/lb for quality steel remnants, but I 'm thinking its a bit high.
 

Allan

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Thanks for all the replies. I would love to use known quality material but my budget is almost non-existent. The other problem is I doubt I can find a local source for cast and if I could the price would be exorbitant, I'm sure. As some folks have mentioned some turn beautifully but some are granite. I didn't know the plastic coating was an indicator of a harder material. I'll have to check that out. As for inclusions, I haven't found any yet.

So, as much as I would like to use known great material, I will have to try a file and relegate them to weights if they are too hard. There is always a wood working project that needs to be weighted down.

I started to make a surface gauge and for the base I used the cut off stub end of a CV joint. It was one of the nicest machining metals I have ever used - except the hardened spline and race area. But a carbide tool took care of that. I don't know what that metal is by SAE grade but I'd sure like to find out. I would use it almost exclusively.

Surface Gauge Base I.JPG Surface Gauge Base II.JPG
 

silence dogood

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#12
Thanks for all the replies. I would love to use known quality material but my budget is almost non-existent. The other problem is I doubt I can find a local source for cast and if I could the price would be exorbitant, I'm sure. As some folks have mentioned some turn beautifully but some are granite. I didn't know the plastic coating was an indicator of a harder material. I'll have to check that out. As for inclusions, I haven't found any yet.

So, as much as I would like to use known great material, I will have to try a file and relegate them to weights if they are too hard. There is always a wood working project that needs to be weighted down.

I started to make a surface gauge and for the base I used the cut off stub end of a CV joint. It was one of the nicest machining metals I have ever used - except the hardened spline and race area. But a carbide tool took care of that. I don't know what that metal is by SAE grade but I'd sure like to find out. I would use it almost exclusively.

View attachment 281787 View attachment 281786
Allen, I should clarify about the plastic coated dumbbells. It's still a hobson's choice when it comes to the hardness of the iron, First, you have to get past the plastic to see what you got. When something gets covered like that it makes you wonder. One thing that you can try is go to a music store and see if they have an old piano with a cracked harp. The harp is the cast iron frame. Chances are the store will let you haul it away for nothing. You'll have your self some high quality iron and some really nice wood. They do come apart in some what insections, Just ease the tension on the strings slowly. There is a lot forces there. I'm like you, I do a lot recycling
 

tertiaryjim

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#13
I also picked up a number of cast iron weights of differing sizes for $1 each at a thrift store.
Have only made use of one so far but it machined nicely ( with carbide ) and had no inclusions or voids.
Am always looking for more.
Be green- Recycle
 

Downunder Bob

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Thanks for all the replies. I would love to use known quality material but my budget is almost non-existent. The other problem is I doubt I can find a local source for cast and if I could the price would be exorbitant, I'm sure. As some folks have mentioned some turn beautifully but some are granite. I didn't know the plastic coating was an indicator of a harder material. I'll have to check that out. As for inclusions, I haven't found any yet.

So, as much as I would like to use known great material, I will have to try a file and relegate them to weights if they are too hard. There is always a wood working project that needs to be weighted down.

I started to make a surface gauge and for the base I used the cut off stub end of a CV joint. It was one of the nicest machining metals I have ever used - except the hardened spline and race area. But a carbide tool took care of that. I don't know what that metal is by SAE grade but I'd sure like to find out. I would use it almost exclusively.

View attachment 281787 View attachment 281786

Good choice Allan, CV joints and also axle shafts are a great source of quality hard steel. they usually machine well with carbides, and can be got for free. A local mechanic friend lets me rummage through his scrap bin whenever I'm Looking for some good hard steel. I also use truck axle shafts for larger dia. another crap I like to find is the hinge pins on heavy excavators, they get thrown out regularly, not as hard but machine well.
 

NCjeeper

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#15
What do they charge per lb. scrap price? I pay $1/lb for quality steel remnants, but I 'm thinking its a bit high.
We went a couple of weeks ago and we paid if I remember right 35 cents a pound for ferrous and 80 cents a pound for non ferrous.
 

jdedmon91

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We went a couple of weeks ago and we paid if I remember right 35 cents a pound for ferrous and 80 cents a pound for non ferrous.
You are correct I looked at copy of my invoice


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middle.road

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#17
I guess maybe look for vintage weights?
There was a company here in the Knoxville area that manufactured weights back in the day.
and now I can not for the life of me remember the name. I keep an eye out for them at estate sales and the thrift stores.

EDIT: found an image. Southern Barbell Co, Knoxville Tenn. No inkling who was the parent company, there were a lot of mfgs around here.
Looks like they might have started out in Richmond VA, and then moved to TN in 1960.
1544397860078.png
 
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Downunder Bob

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#18
Good sources of quality cast iron. Flywheels off old manual cars, brake drums from old cars, Note discs are usually cast steel. Large gear wheels from old machines even old engine blocks, it all depend on what sizes and shapes you want. Crown wheels from old diffs Larger items can be found at truck wreckers.
 

Bob Korves

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#19
I am retired from the heavy trucking parts business. One of my former customers has a truck wrecking and salvage yard, fairly close to my shop, and he gives me free reign to dig through his scrap metal bin, which is about 8 x 8 x 40 feet long and can be empty or near full, depending on when the last pick up was. Usually there is way more good scrap metal in there that is usable in a hobby shop than I have room to store. Still, it is a good resource for when I need something. Carrying a bag of doughnuts when you arrive to ask for scrap metal will often open the gates wide open from then on.
 

middle.road

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I am retired from the heavy trucking parts business. One of my former customers has a truck wrecking and salvage yard, fairly close to my shop, and he gives me free reign to dig through his scrap metal bin, which is about 8 x 8 x 40 feet long and can be empty or near full, depending on when the last pick up was. Usually there is way more good scrap metal in there that is usable in a hobby shop than I have room to store. Still, it is a good resource for when I need something. Carrying a bag of doughnuts when you arrive to ask for scrap metal will often open the gates wide open from then on.
I have some friends with the same. I attempt to stay out of the roll-off but it seems to have an off-world force drawing you to it.
The Brass pins out of older diffs are a nice score.
Very easy to get carried away and overload on stuff.

1544459262745.png ...... 1544459273718.png
 

just old al

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#21
+1 on axle shafts - they can be annealed and used for high wear items.

One caveat - inspect the shaft and see if it shows signs of twisting or other abnormal wear. Old Land-Rovers tend to break shafts and they twist before they break (usually at the splines) I've cut and tried to reuse such shafts and found them to warp if strained. Annoying.
 
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