Making a straight edge out of an old cast iron level as a first scraping project ?

[max.levesque]

I stumbled upon an old cast iron level, got it for practically nothing, thinking I could use it as a first scraping project, to make a straight edge.

It's kind of an H-beam, with a thickness of around 4.6 millimetres, as the photos shows.

The point is not to make the best straight edge possible, but to learn scrapping, though I will be quite pleased if the straight edge turns out decent !

On the granite plate I can see it's not so flat, as I can stick a 0.002" feeler gage near the middle of the bar.

Is that a good project to learn scraping ?

 

[JST]

Yes, you can make a decent S.E., and it is a workable first project.

I have a short S.E. made from an old Stanley level long ago. It has been stable for years. Yours looks similar to mine.

Depending on how flat the surface really is (the one without the circular relief), you may want to flatten it on a mill first. The 0.002" does not seem bad, though, you should be able to get that flattened in maybe 10 scraping passes or so.

 

[Paolo_MD]

I second that it could be a good project. However, before investing any serious time in it, I would touch up both parallel surfaces with a file, to remove most peening surface stresses.
Given the relatively small size, dings in the surface opposite to the one you are scraping could be more relevant that you might think.

Paolo

 

[Bakafish]

The narrow width makes a mason's level a little claustrophobic as a first scraping project, it's all going to be dealing with edges. The castings can be lovely though. I buy rusty mass blocks and straight edges really cheap and practice scraping on them. This 500mm unit was ~$50 delivered and needed a lot of cleaning, but the rust wasn't too deep and no machining was required before scraping it back to life.



Mass blocks are maybe not common over there, but they are dirt cheap here and give a ton of surface area to practice and are great for learning how to make squared faces.

 

[dgfoster]

Others have adequately answered the “should I” question.

I think it is very likely the level was properly cast (grey iron and slow cooling in the sand) many decades ago. It may not have been thermally stress relieved. Doing so now would be easy and something I would do just to stabilize the casting.

Find someone with a common electric pottery kiln. Stick it in the kiln and set it via the key pad to ramp up maybe 300 degrees F per hour to a target temp of 1150. Hold that for an hour. Turn off the kiln and let it cool to a couple hundred degrees prior to removal. There will be some reddish discoloration but no deep scaling. That is all that is needed to stress relieve it.

Denis

 

[Bakafish]

Obviously you will need to remove all the vials before exposing your level to any sort of heat treatment. Mr. Foster has likely forgotten more than I will ever know about heat treatment, but my gut contracts in fear at the suggestion of putting that thing in a kiln of any sort. There is some chance that things will get weird, and it already seems like too much wasted effort.

I would again discourage you from practicing on such a narrow workpiece. Transitioning on and off of edges is an important scraping skill, but that's all you will be doing on such a narrow surface, and I'd venture to say that most scraping is of planer surfaces not edges. Arguments that the end result is worthwhile as it can be used as a 'straight edge' are not very compelling to me, as it isn't really a robust enough frame to hold such high accuracy (I have several different lengths of hardened and ground I beam style straight edges, and the thing they all share is they are a solid chunks of metal with no 'speed holes' in them.)

It's a nice masons level, clean it up, get the vials nice and bright, give it some fresh paint or Japaning and wax the exposed surfaces so they don't rust. Enjoy it for what it is rather than try to make it something it's not.



This little old FSK level was 500yen, filthy and covered in rust. But a bit of careful restoration brought it back to great condition.



No need to scrape it, it is great at what it is. Those old casting patterns are easy on the eyes too. Find an old surface plate, a real camelback, angle block, V-Block or machinists level that is really toasted or invest in something worth restoring. The plus side of scraping taking forever is that it takes a long time to really f something up, and you will have a lot of learning opportunity before things are unrecoverable.

 

[dcsipo]

I stumbled upon an old cast iron level, got it for practically nothing, thinking I could use it as a first scraping project, to make a straight edge.

It's kind of an H-beam, with a thickness of around 4.6 millimetres, as the photos shows.

The point is not to make the best straight edge possible, but to learn scrapping, though I will be quite pleased if the straight edge turns out decent !

Scrape it in and use it both as a level and a straight thingie . It will never be as stiff as a real straight edge, but it can be made straighter than it is now.

On the granite plate I can see it's not so flat, as I can stick a 0.002" feeler gage near the middle of the bar.

Is that a good project to learn scraping ?

Good to start with. It is within scraping range. Be careful with the hollow side, and it is harder to scrape the narrows on either side than you would expect.

 

[dgfoster]

Obviously you will need to remove all the vials before exposing your level to any sort of heat treatment. Mr. Foster has likely forgotten more than I will ever know about heat treatment, but my gut contracts in fear at the suggestion of putting that thing in a kiln of any sort. There is some chance that things will get weird, and it already seems like too much wasted effort.

Baka,

I am wondering what is the basis of your concern regarding heat treatment of this cast iron level. Have you had a bad experience with stress relief of cast iron or read about or heard about bad outcomes? I ask as I have not had any such experience in stress relieving a few hundred straight edges nor have I read about or heard about some sort of unfortunate outcome.

Denis

 

[dcsipo]

Baka,

I am wondering what is the basis of your concern regarding heat treatment of this cast iron level. Have you had a bad experience with stress relief of cast iron or read about or heard about bad outcomes? I ask as I have not had any such experience in stress relieving a few hundred straight edges nor have I read about or heard about some sort of unfortunate outcome.

Denis

I am not sure I would bother with heat-treating that thing. . It is a very thin casting. It probably already did all the warping it will ever do. I would think that having it heated and cockeyed in a pottery kiln does more harm than good. Just scrape it in, let it stand for a few days, re-spot it, and fix any changes. That thing is a wet noodle compared to a proper straight edge. It will flex a few tenths just by sneezing at it. But hey, I scraped very questionable things in the past, so glass houses and stones make a volatile mix.

 

[dgfoster]

If I were going to scrape it, I would heat treat it. In a casting that has a lot of residual stress from its original solidification, the casting can be thought of as a matrix of a billion tiny springs randomly oriented and each exerting some force. Scraping and machining remove some of those springs which have, until removal, been in balance with the remaining springs. Removal of some of the springs then causes imbalance and warping of the casting. Getting a stressed casitng truly straight can be a daunting job.

Thermal heat treatment virtually elliminates those springs.

Time does nothing to relieve stress. Iron is a crystaliune material. There have been many studies to show that the internal stresses in iron are not relieved by time, low temperature cycling (weather exposure), vibration, etc. The US Navy did an oft-cited study of such in 1948 that addressed these questions. ASM has also published similar results in their Handbooks.

US Navy Stress Relief in Cast Iron Study

I know of no adverse effects of heat treatment. If someone knows of harm caused by proper heat treatment of iron, I hope they will inform us.

Concerning just how flexible this particular casting is, the owner could easily set it up on blocks with a strategically placed tenths indicator and load it. I did this and have reported results here on my castings. Then the question becomes how stiff is stiff enough and that is, in itself, an interesting question. It turns out, that for purposes of marking ways for flat scraping, flatness is critical, but resistance to deflection due to loads is less important as the tool is supported at myriad points along its length. If the tool is used to span distances, resistance to flexion becomes more important.

Denis

 

[JST]

I never heat treated mine, and it has remained stable for years now. Those levels are fairly old, and time plus use can relieve stresses, as well as add more.

Also, given that it is a level, I would expect the casting was stress relieved in manufacturing. In the old days many companies actually tried to put out a good product, instead of only focusing on the bottom line.

Probably no harm would be done by trying to relieve the thing, but cooling is somewhat important as far as not adding any stress back in. Best not to mess with it unless you are prepared to control the process decently.

 

[Bakafish]

Baka,

I am wondering what is the basis of your concern regarding heat treatment of this cast iron level.

As I said, based on 'gut feeling' and the worry of turning a perfectly good tool into a banana due to some metallurgical consideration that none of us could predict. My guess is that your experience is with heat treating your fine and robust castings not castings that were skeletonized for weight and alloyed for rough handling. I also suspect that removing the vials without damage and getting them remounted accurately would be a challenge, but that's beside the point.

Have you had a bad experience with stress relief of cast iron or read about or heard about bad outcomes? I ask as I have not had any such experience in stress relieving a few hundred straight edges nor have I read about or heard about some sort of unfortunate outcome.

I don't think any of us has noted we have much information on post machined heat treating something of this description, certainly I have no idea. Your advice may be spot on correct, my concern is that we don't have any actual experience doing such treatment on one of these, and the chances that whatever oven or kiln he gains access to overheats or suffers from drastic gradients is pretty high. It's just not the sort of advice I'd give to a beginner even if I knew it was correct, which I don't think any of us know for sure. I don't mean to be critical of your advice, as I said you are probably 100% right and you've shown great skill in the field, I just am advising to leave the poor thing alone and find a more appropriate scraping candidate. Maybe you have some scrap casting you can offer him.

Denis

 

[dgfoster]

If the OP becomes interested in heat treating his level, he should contact me. Stress relieving cast iron in a simple progammable pottery kiln is about as straightforward and safe a process as I know of. I'll talk him through it.

Denis

 

[dcsipo]

If I were going to scrape it, I would heat treat it. In a casting that has a lot of residual stress from its original solidification, the casting can be thought of as a matrix of a billion tiny springs randomly oriented and each exerting some force. Scraping and machining remove some of those springs which have, until removal, been in balance with the remaining springs. Removal of some of the springs then causes imbalance and warping of the casting. Getting a stressed casitng truly straight can be a daunting job.

Thermal heat treatment virtually elliminates those springs.

Time does nothing to relieve stress. Iron is a crystaliune material. There have been many studies to show that the internal stresses in iron are not relieved by time, low temperature cycling (weather exposure), vibration, etc. The US Navy did an oft-cited study of such in 1948 that addressed these questions. ASM has also published similar results in their Handbooks.

US Navy Stress Relief in Cast Iron Study

I know of no adverse effects of heat treatment. If someone knows of harm caused by proper heat treatment of iron, I hope they will inform us.

Concerning just how flexible this particular casting is, the owner could easily set it up on blocks with a strategically placed tenths indicator and load it. I did this and have reported results here on my castings. Then the question becomes how stiff is stiff enough and that is, in itself, an interesting question. It turns out, that for purposes of marking ways for flat scraping, flatness is critical, but resistance to deflection due to loads is less important as the tool is supported at myriad points along its length. If the tool is used to span distances, resistance to flexion becomes more important.

Denis

Yup, all that is true, and something like yours or other engineered straight edges need heat treatment. You also have the skills and the tools to ensure successful heat treatment of any CI part. The OP probably lacks both. I have one of those levels I would be concerned about heating it to 1150 and assuming that it will keep its shape , especially if it is not fully supported while heated. Most pottery kilns are not large enough to lay a 2' level on the bottom, and I am unsure if they are tall enough to stand a 2' level. Having it heated unsupported, resting diagonally may introduce additional unintended warping or some other stresses. I did not want to make this into a discussion about the benefits of heat-treating cast iron, which is a noncontroversial subject. I am questioning the utility of doing it to that casting. There is only so much lipstick you can put on a pig, and it is still a pig., If one is determined to wrestle the pig, it will not be the lack of lipstick to stop them. . So, just scrape the darned thing if it warps or twists into a banana, scrape it some more till it stops.

 

[JST]

Mine was so easy to scrape, that I figured it had been stress-relieved already. I did not have to chase anything but my own goof-ups.

No reason not to try it, unless the thing is worth big money to some deranged tool "collector". If it is anything like mine, it will not be an issue.

You have it, go for it!

 

[Paolo_MD]

As I suggested earlier in this thread, I would first touch both parallel surfaces with a file, removing the "skin". This is mostly to release the stress accumulated during the years of bumping it and denting it. It would be hard to determine at that point if any movement is due mostly to removing peening stresses, or to stresses in the casting.

If having it stress relieved by heat treating it is something easily achievable by Max, I would strongly encourage it doing so, even if it looks an overkill for this project: it is already frustrating to see the surface twisting while scraping when you know what you are doing, and it would be utterly confusing for the beginner scraper that has hard time interpreting what is going on. Beginner mistakes, or dancing casting?

However, if the heat treatment is too much of a chore, by any means I would encourage Max to start scraping the level (actually, being narrow, it will force you to learn making rather short scraping marks, which is a skill that, the sooner is learnt, the better).
If the results are perplexing, leave it on the shelf and try another project that will help you better understand if you are doing something wrong, or it's the level that doesn't want to stay still.

Paolo

 

[max.levesque]

If the OP becomes interested in heat treating his level, he should contact me. Stress relieving cast iron in a simple progammable pottery kiln is about as straightforward and safe a process as I know of. I'll talk him through it.

Denis

I'm interested in stress relieving with modest/DiY means, if not for this project, but for ones.

If you have links to share, I'm interested !

 

[dgfoster]

Max said :
"I'm interested in stress relieving with modest/DiY means, if not for this project, but for ones.

If you have links to share, I'm interested !"

ASM Handbook 1 has some information on stress relief of Grey Iron. Here is a useful excerpt:

"Only a small percentage of castings are stress relieved before machining, chiefly those requiring exceptional accuracy of dimensions or those with a combination of high or nonuniform stress associated with either low section stiffness or an abrupt change in section size. Castings of class 40, 50, and 60 iron are more likely to contain high residual stresses. Figure 19 shows stress relief at seven temperatures between about 310 and 600 °C (600 and 1100 °F). The range from 480 to 600 °C (900 to 1100 °F) recommended. For best results, castings should be held at temperature 1 h or more and then cooled in the furnace to below 450 °C (850 °F). High-strength and alloy gray irons require temperatures approaching 600 °C (1100 °F)."

Pretty simple huh? I do not worry about "supporting" castings during heat treat. I aften treat 3 to 6 castings at once and stack them into the oven without worrying about stacking one on another or spanning distances. I have never seen any distortion as a result. I usually treat at 1150, not because I am using high alloy iron, but rather just so I don't have chirping about "I heard you had to treat iron at 1100F" from folks who are not fully informed but sometimes eager to argue.

ASM Handbook 4 also provides a lot of background information concerning iron castings, machining them, and stress relieving including a statement that vibratory stress relief has never been demonstrated by legitimate scientific study to be effective in cast iron. Nevertheless, vibratory relief still has its adherents.

The Navy study linked in Post 10 above addresses stress relief and ineffectiveness of time, weather, and other non-standard methods as well as laying out a method they found useful for thermal stress relieving cast iron.

This really is a simple process that any electric pottery kiln is capable of. Programmabilty is a handy and almost universal feature in modern kilns. No wrapping in steel foil is needed as there is only very superficial rust/discoloration as a result of stress relief. I have never heard of a cast iron casting warping significantly as a result of heat treatment and, so far, no one has presented even anecdotal reports of such. Neither ASM nor the US Navy cautioned regarding this either. (I did have a casting of mine broken by a heat treater once. But that is because the forklift that ran over it was bigger than the casting!)

Denis

 

[jim rozen]

As long as he's aware of the possible stress relief issues, I'd say go ahead and start learning by doing.

Other question: "japanning" - how can this be done at home? Anyone done this?

 

[dgfoster]

As long as he's aware of the possible stress relief issues, I'd say go ahead and start learning by doing.

Other question: "japanning" - how can this be done at home? Anyone done this?

I have never attempted Japanning. I have only used shaker cans to apply glossy or semi-glossy black enamel to various vintage Stanley planes, draw knives, and router planes after replacing or fabricating any missing parts and scraping their soles. (A scraped sole really makes a good Western metal plane work even better.)

But, I have wondered about doing it at some time in the future. Were I to give it a whirl, I think I would use this guy as a prime resource as he seemed to really look into the history and several different methods of trying to make a suitable tool finish. And he seems to have honestly and critically looked at his results.

Japanning Methods Video Link

Denis