Using Old Exercise Weights as Project Material?

[bcall2043]

I heard using old cast iron exercise weights for project material can be a crap shoot but wondered if anyone has any experience good or bad?

Been looking for a piece of material for a upcoming project that I think could be made from cast iron or steel. Looking at my usual source, the scrap yard, I was finging pieces of steel round too small or too large and no cast stuff even close. Today I found an old cast iron exercise weight that may work. It was a 30# hand weight that could be cut into two pieces and provide a second piece of material in case I mess up the first piece. I have attached a photo below of the weight after I cleaned off some of the rust and cut it in half.

　

The project is a backing plate for a lathe chuck and requires a finish diameter of 4.00 inches. The existing backing plate that came with the chuck has a spindle thread that is too small for the lathe I want to put it on and the hub is too small to bore out and thread larger. So I need to start with new material.

Anything I should know before I start?

Benny
The Orphanage Never Closes

 

[Frank Ford]

From my limited experience and from what I've heard/read, this kind of weight is second only to window sash weights in its unreliability for machining. Can be OK, but can also include some really nasty stuff, hard spots, bits of sand, and what-all. So, I'd proceed with caution and lowered expectations.

Not too long ago I cut up a couple of weights - one really old barbell plate that seemed pretty uniform, and another, recently imported dumbbell that was made of some kind of ridiculous concrete/iron mix.

 

[8ntsane]

I would use caution Benny
Those things can be a real POS material wise. As Frank says, it can be full of nasty stuff. Depends on what your intending to use it for really. I wouldnt trust it for a chuck mount, unless it was for a rotary table or something stationary, that isnt spinning under power with the spindle.

You will know once you start cutting it, if its full of junk. Or has air pockets, and hard spots. Its a coin toss, take your chances. Might be better off with a chunk of hot rolled?

 

[bcall2043]

..........this kind of weight is second only to window sash weights in its unreliability for machining............So, I'd proceed with caution and lowered expectations.

I would use caution.........................Those things can be a real POS...................it can be full of nasty stuff.....................I wouldnt trust it for a chuck mount................You will know once you start cutting it..................take your chances. Might be better off with a chunk of hot rolled?

Thanks for the quick replies. You both kind of say the same things I remember hearing or reading somewhere before. I will keep looking for the right material but may do a trial run on the material I have to see what happens. Be a good learning experience. First I need to get the needed dimensions of the lathe spindle and thread so I can make a dummy of it for a internal thread gage. Do you see any problem using aluminum for the thread gage? It's easy to cut and won't see much use.

Benny
The Orphanage Never Closes

 

[mitsue]

Do you see any problem using aluminum for the thread gage? It's easy to cut and won't see much use.

Benny
The Orphanage Never Closes

It could pick up a burr on the thread and lock up. Stainless Steel is bad for galling also. Harder material is better and it won't change size when you hold it in your hand like aluminum will.) I wouldn't want to make a close fit thread with an oversize gauge.
Darcy

 

[tripletap3]

Something else to consider on using old cast or scrap metal that I learned the hard way. Being a tight wad I tried machining a piece of scrap cast material and it ended up costing more in inserts than the clean metal would have cost me:nuts:. Not to mention the huge aggravation
and a part that was less than desireable so I ended up buying a good chunk of metal anyway!:angry: I found out that sometimes being cheap can be exspensive. Just a thought.

 

[bcall2043]

It could pick up a burr on the thread and lock up........... Harder material is better and it won't change size when you hold it in your hand like aluminum will.) I wouldn't want to make a close fit thread with an oversize gauge.
Darcy

Thanks Darcy those are good points that I had not thought of. I will look for metal harder than aluminum for the internal spindle/thread gage.

Benny

 

[bcall2043]

............... Being a tight wad I tried machining a piece of scrap cast material and it ended up costing more in inserts than the clean metal would have cost me........ so I ended up buying a good chunk of metal anyway! I found out that sometimes being cheap can be exspensive. Just a thought.

I agree with you tripletap3. I measured the lathe spindle yesterday and checked online and there are blanks available. For example Jeff at tools4cheap has a chuck back plate that could be made to fit for $47 which is almost as much as I paid for the chuck. That is not many inserts. http://www.tools4cheap.net/proddetail.php?prod=2146back

I know I'm cheap and besides going to the scrap yard is fun.

Benny
The Orphanage Never Closes

 

[AR1911]

Before I chucked that up in my lathe I'd take a slice off it with my bandsaw and see what it looks like in cross-section

 

[bcall2043]

Before I chucked that up in my lathe I'd take a slice off it with my bandsaw and see what it looks like in cross-section

Too late!
I decided to go ahead and see how the cast exercise weight would be like to machine. The interrupted cut caused by the hex shape turned out to be a task! I found out that my little lathe did not like this and that the back gear needs some work to prevent it from jumping out of mesh. That repair project will need to be done before much more can be turned. The first photo shows the weight as it is just about round. One small flat and the "size" cast on the outside is all that remains to clean up.

I was taking light cuts with hand feed and not caring much about finish. The next photo shows the casting as the OD reached 4.350 inch and is round except for a little of the "size" cast area.


There were some voids in the casting as some of you warned about but no hard areas were hit, yet!

If this piece of cast iron continues to machine okay maybe I can use it for the spindle/thread gage. It would not have the issues that the aluminum I thought about using would have. It sure would not have any loading issues if used for the thread gage. If it only continues to machine okay and I don't screw it up.

By the way, machining cast iron is messy. Would not want to do that for a living!

OT - Off to fix the backgear next. I have never been into my 10" SB lathe but did some reading about the subject online. The back gear appears to be held engaged by a spring and shoe on one of the eccentrics. I will pull it all apart and clean and lubricate at the same time.

Benny
The Orphanage Never Closes