# Machining Cast Iron Dumb Bells



## Allan (Dec 7, 2018)

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 (Dec 7, 2018)

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 (Dec 7, 2018)

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 (Dec 7, 2018)

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.


----------



## COMachinist (Dec 7, 2018)

chips&more said:


> 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


----------



## RJSakowski (Dec 7, 2018)

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 (Dec 7, 2018)

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 (Dec 7, 2018)

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:


----------



## jdedmon91 (Dec 7, 2018)

chips&more said:


> 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


Sent from my iPhone using Tapatalk


----------



## 1448CW (Dec 7, 2018)

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 (Dec 8, 2018)

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.


----------



## silence dogood (Dec 8, 2018)

Allan said:


> 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.
> 
> ...


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 (Dec 9, 2018)

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 (Dec 9, 2018)

Allan said:


> 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.
> 
> ...




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 scrap I like to find is the hinge pins on heavy excavators, they get thrown out regularly, not as hard but machine well.


----------



## NCjeeper (Dec 9, 2018)

1448CW said:


> 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 (Dec 9, 2018)

NCjeeper said:


> 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 


Sent from my iPad using Tapatalk


----------



## middle.road (Dec 9, 2018)

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.


----------



## Downunder Bob (Dec 10, 2018)

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 (Dec 10, 2018)

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 (Dec 10, 2018)

Bob Korves said:


> 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.



	

		
			
		

		
	
......


----------



## just old al (Dec 12, 2018)

+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.


----------



## gi_984 (Dec 12, 2018)

I'm curious if anyone has tried tractor weights?  The kind that are stacked at the front or back of a tractor or forklift?  Some are definitely cast iron.  Around here you can get them fairly cheap when they have the tabs broken off.  They apparently can get broken when the weights get taken on or off.  Once the tab that hooks the weight into the bracket or holder get snapped, the weight is trashed.  I've got one for free but haven't tried to machine it yet.  Almost 20 inches square and about 1 1/2 inches thick.


----------



## Bob Korves (Dec 12, 2018)

gi_984 said:


> I'm curious if anyone has tried tractor weights?  The kind that are stacked at the front or back of a tractor or forklift?  Some are definitely cast iron.  Around here you can get them fairly cheap when they have the tabs broken off.  They apparently can get broken when the weights get taken on or off.  Once the tab that hooks the weight into the bracket or holder get snapped, the weight is trashed.  I've got one for free but haven't tried to machine it yet.  Almost 20 inches square and about 1 1/2 inches thick.


Metals are spec'd by buyers for specific requirements, looking for the best price and other needed qualities.  If we spec metal to make a cast weight out of, we care that it casts easily, and has enough strength to keep from breaking when in use.  Machining qualities may or may not be something we care about for that piece, but will increase cost if it is specified.  The metal may or may not be machinable, no one cared if it was not part of the specs for the metal.  That is why we call it "mystery metal", because we do not know what the specs were when it was ordered.


----------



## jdedmon91 (Dec 12, 2018)

gi_984 said:


> I'm curious if anyone has tried tractor weights? The kind that are stacked at the front or back of a tractor or forklift? Some are definitely cast iron. Around here you can get them fairly cheap when they have the tabs broken off. They apparently can get broken when the weights get taken on or off. Once the tab that hooks the weight into the bracket or holder get snapped, the weight is trashed. I've got one for free but haven't tried to machine it yet. Almost 20 inches square and about 1 1/2 inches thick.



It be worth a try, if someone gave me one I’d cut a small piece off and try machining it. Since you got it for no or extremely low cost. It be worth trying. 


Sent from my iPhone using Tapatalk


----------



## jdedmon91 (Dec 12, 2018)

Bob Korves said:


> Metals are spec'd by buyers for specific requirements, looking for the best price and other needed qualities. If we spec metal to make a cast weight out of, we care that it casts easily, and has enough strength to keep from breaking when in use. Machining qualities may or may not be something we care about for that piece, but will increase cost if it is specified. The metal may or may not be machinable, no one cared if it was not part of the specs for the metal. That is why we call it "mystery metal", because we do not know what the specs were when it was ordered.



A good point. But like the OP said he basically got for free. I’d cut some off and experiment. We always need cast for projects like backplates 


Sent from my iPhone using Tapatalk


----------



## Bob Korves (Dec 12, 2018)

The point of my long winded post was that mystery metal is just that.  "A single test is worth a million expert opinions."


----------



## Downunder Bob (Dec 13, 2018)

Bob Korves said:


> 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.



Yes that should work, I found that donating a slab of beer to their Xmas fund worked a treat, I have been granted unlimited access to the scrap bin. On a coupe of occasions he asked if I was looking for something specific, when I told him what I wanted he took me out to his material racks at the back of the shop, i quickly s[potted a suitable piece, It was about 70mm id x 100mm od and about 500mm long I want it to clean up at 75mm id. he said take it, he wouldn't accept anything for it, I guess another slab of beer is in order soon, after all it is nearly Xmas.


----------



## Downunder Bob (Dec 13, 2018)

Bob Korves is spot on again A single test is worth a million expert opinions, at best they can only guess. If it's free just suck it and see, if it machines well use it if it doesn't it is still a weight, and you have lost nothing.


----------



## gi_984 (Dec 15, 2018)

The reason I mentioned tractor weights is because of the source.  John Deer, International Harvester, etc.  operated their own foundries.  Not sure if the other farming equipment manufacturers did the same.  Point being they used good quality cast iron in their equipment.  I suspect they used the same cast iron in their tractor weights.  In an agricultural area, broken ones should be easy to acquire for little to no cost.  
My neighbor (retired farmer) gave me the one I have.  I might cut a section out and try a few experiments.  
Has anyone done any machining on cast iron tractor parts?


----------



## jdedmon91 (Dec 16, 2018)

gi_984 said:


> The reason I mentioned tractor weights is because of the source. John Deer, International Harvester, etc. operated their own foundries. Not sure if the other farming equipment manufacturers did the same. Point being they used good quality cast iron in their equipment. I suspect they used the same cast iron in their tractor weights. In an agricultural area, broken ones should be easy to acquire for little to no cost.
> My neighbor (retired farmer) gave me the one I have. I might cut a section out and try a few experiments.
> Has anyone done any machining on cast iron tractor parts?



Yes cut a piece and try it. You said it JD and IH did do their own castings. Also if the weights were older say pre 2000 they more than likely cast by in the states by a major tractor manufacturer. So the odds are good the cast is of a good machining grade. 


Sent from my iPhone using Tapatalk


----------



## Cadillac (Dec 16, 2018)

I actually had a write up on machining tractor suitcase weights. The ones I harvested were ford weights. About 4” thick 10” square.60-70 vintage.  When cutting some spots cut okay then some spots were very hard. Felt like I dulled every blade in the shop to get it cut out. Using a carbide endmill it cut but felt a lot of resistance. Not what I’d expect from cast.   After asking for some advice on the forum I threw the chunk in my forge while doing some casting and got it to a red hot temp. Then I let it cool overnight in the forge. I have yet to machine the part again but my hopes are it will do better. I have a newer JD plate 1 1/4 thick and a 2’ square. Says made in USA on it so I’m hoping it’s good.


----------



## NortonDommi (Dec 16, 2018)

Just a note on axles, we have a lot of Japanese cars here and many front wheel drive.  The axles on these are induction surface hardened 4130 and will destroy tips. They only way to use them is to have a very robust tip and a heavy cut to 'skin' them.  The hard layer,(about 1 mm),is harder than Diamond from my experience.  I now usually cut them and use for punches and pins if the right size and grind to size.  Enclosed axles from rear wheel drive or a 4 x 4 with enclosed axles are not a problem.  Most of these seem to be 1140 or 1180.


----------



## jdedmon91 (Dec 20, 2018)

Cadillac said:


> I actually had a write up on machining tractor suitcase weights. The ones I harvested were ford weights. About 4” thick 10” square.60-70 vintage. When cutting some spots cut okay then some spots were very hard. Felt like I dulled every blade in the shop to get it cut out. Using a carbide endmill it cut but felt a lot of resistance. Not what I’d expect from cast. After asking for some advice on the forum I threw the chunk in my forge while doing some casting and got it to a red hot temp. Then I let it cool overnight in the forge. I have yet to machine the part again but my hopes are it will do better. I have a newer JD plate 1 1/4 thick and a 2’ square. Says made in USA on it so I’m hoping it’s good.
> View attachment 282593
> 
> View attachment 282592



Have you tried to machine it after this process 


Sent from my iPhone using Tapatalk


----------



## Cadillac (Dec 20, 2018)

Not yet I'm in the middle of a project on the Bridgeport. The piece of cast is to make a solid tool post mount for my 14x40. Not really needed but a nice project. After initial cutting I threw it on the mill and tried milling with a 3/4 rougher endmill and it felt resistive so I took recommendation from the forum to try annealing. I should be on it by next week if Christmas isn't to hectic.


----------



## ericc (Dec 21, 2018)

A drain cover shattered in my neighborhood and scattered pieces of cast iron all over the street.  I harvested a few and found out that stuff is beautiful.  Cuts like "butta" and leaves a fine dusty chip.  Very uniform, smooth and predictable.  Solders and brazes just fine.  I have one cast iron dumbbell which has similar good properties.  Good luck, I guess.


----------



## jdedmon91 (Dec 22, 2018)

ericc said:


> A drain cover shattered in my neighborhood and scattered pieces of cast iron all over the street. I harvested a few and found out that stuff is beautiful. Cuts like "butta" and leaves a fine dusty chip. Very uniform, smooth and predictable. Solders and brazes just fine. I have one cast iron dumbbell which has similar good properties. Good luck, I guess.



Question do you think the quality of the bar bells makes a difference? Like a higher end set that is used in Gyms or competition? I would think those uses would have to use more consistent material to make the weights consistent that those uses demand. 

A home set that is close isn’t a big deal. Neither a tractor weight, but when it’s important to know the weights are consistent for competition




Sent from my iPhone using Tapatalk


----------



## Bob Korves (Dec 22, 2018)

jdedmon91 said:


> Question do you think the quality of the bar bells makes a difference?


Let me say it again.  You are buying barbells, not metal spec'd for fine machining.  You might get lucky and get metal that is high grade machine quality iron, but what is the chance of that?  The only requirements of barbells is that they cast to size and do not explode when dropped.  Mystery metal is always a mystery.  If it was me, I would be looking for cast iron scrap that has been finely machined, then you know it will machine well.  Making the weights of barbells match is not a big deal


----------



## jdedmon91 (Dec 22, 2018)

Bob Korves said:


> Let me say it again. You are buying barbells, not metal spec'd for fine machining. You might get lucky and get metal that is high grade machine quality iron, but what is the chance of that? The only requirements of barbells is that they cast to size and do not explode when dropped. Mystery metal is always a mystery. If it was me, I would be looking for cast iron scrap that has been finely machined, then you know it will machine well. Making the weights of barbells match is not a big deal



I’m not familiar with cast iron. That was my question, thanks for the answer. Some materials the content makes small differences, most barbells one would buy are yard sale items, kinda like treadmills 


Sent from my iPhone using Tapatalk


----------



## ericc (Dec 26, 2018)

I agree.  I've wasted time and bombed out good cutters trying to make stuff out of mystery metal.  The lure is still there.  Now, I spark and file test everything.  I have a huge set of comparative coupons, so most standard steels can be identified.  This is also useful around estate steels, since  a clean mystery bar can be A-2 which might lead to an accident (I've seen them) if forged as mild steel.


----------

