FS 19 to 23# Featherweight 36" Camelback Straight Edge. Rough casting or machined.

FS 19 to 23# Featherweight 36" Camelback Straight Edge. Rough casting or machined.

Note to moderator: Please move this to the "For Sale" forum as I posted here in error. Sorry and thank you.


At long last, after previously having my Straight Edges commercially cast, I have gotten all the kinks worked out of my own foundry and am casting my own straight edges start to finish. The complexities of making a working small-scale foundry greatly exceeded my estimates. But the satisfaction of getting a working foundry set up and making better castings than I could have cast commercially has been a very interesting and satisfying labor of love.

I am using the same pattern as before, but now am sourcing and pouring Class 40 Grey Iron Straight Edges and doing every step in that process myself. My feed stock comes from a commercial foundry and is spectoscopically checked to confirm that it meets specifications. Every straight edge is stress relieved in a commercial heat treat oven following initial in-sand cool down. Taking both steps minimizes retained internal stresses.

I have previously sold half a dozen of these of these to straight edges to PMers (some pros and some neophytes) with universally glowing reviews from those owners. I now have four back from heat treat and will be casting more as needed. As cast it weighs 28#. But to get it flat and cleaned up, it machines to 23#. From there it is a matter of personal preference. I machined mine to 19 pounds which is probably the lower end of what most folks would want though it would certainly be practical to go thinner without loss of rigidity.

The sole measures 2 7/8" wide and 1/2" thick as cast. It requires roughly an eighth of an inch of milling on the sole base to clean it up.

Though it is very light in weight compared to comparable 36" SE's, it is very rigid. I tested it to have less than .0001" deflection when supported at its ends and loaded with 30 pounds at its midpoint. Its broad base distinguishes it from any other 36" SE new or old. (Check it out----other 36" straight edges whether new or vintage look more like a narrow railroad track in profile) That broad base allows the user to reach well under dovetails and other potentially interfering features. It is not intended to be used as a prism on doves, though. More on that later.

I can supply it as a rough casting or with the sole machined to .002 flatness and the sides machined as well. (Flatness of .002 means that when mapped, the highest high point of the sole to the lowest low point is less than or equal to .002. I can usually do better than .002 as I have developed a proprietary method to fixture the SE's that minimizes distortion)

Local pickup would be ideal, though I can box and ship for about 80 dollars (depends on location) to most places in the US. Shipping to Canada is possible at greater expense.

If interested, please PM or preferably email me, at all one word denis g foster at gmail dot COM. Please note that my first name has one “n.”

I will be able cast more as needed to keep up with demand.

The pictures in the next post show a plywood, plastic pad, and brass grommet storage shoe I made for mine---not supplied but for illustration.

Price is 450 USD as cast and 625 USD machined. Shipping, obviously would have to be worked out depending on buyer needs.

Denis

I added a photo of the profile of the end of the SE and then posted again some photos of the casting. Your back will thank you for choosing a lightweight straight edge.

PS Tomorrow I will be casting a proof-of-concept Featherweight prism that I plan to offer for sale in the near future. It is designed so that it can be cast in 36" lengths but conveniently cut to 12 or 24 inch lengths as needed with no compromise in utility or quality.

Later this summer I hope to be casting 48" Featherweight straight edges of similar design to the 36.

Couple more pics

Here are a couple of pics of my personal 36 and the hang-up sole cover I made for it.

What is your iron melter, cupola, electric furnace,..? What is a typical melt, 1000#? Transfer bull ladle, 2 man hand shank? Petrobond sand?

Do you do custom castings?

Very interesting.

Tom

Tom,

I use diesel fuel atomized and blown with combustion air into a refractory-concrete furnace. Induction is elegant and very economical to operate but initially hugely expensive even for 60 pound melts. These straight edges are cast one at a time.

I use use green sand as petrobond is not very well suited for the temperatures involved (compared to aliminum, brass, bronze) as so much of the petrobond binder is burned by the high heat. Green sand can last through many cast iron cycles with a little care.

I designed a unique (never saw evidence of similar) lifting hoist to get the crucible out of the furnace quickly, safely, and single-handed as I work alone. Once out of the furnace the crucible is transferred to a wheeled trolley and moved to the molds and poured. Kinda tricky handling as the iron is the consistency of water and has a lot of stored energy at 2500 to 2600 F.

I have not done any custom pouring yet as I have been so focused first on solving the myriad (casting is conceptually simple but making by it actually happen involves intertwined challenges) technical issues and now on pouring SE's. Pouring iron is much more difficult than non-ferrous. I know of no one in a hundred mile radius other than commercial operations-a few- in the Seattle area. There are many non-ferrous casters around especially those doing aluminum as it is much lower temperature, doesn't require special crucibles etc. I might do some custom work someday if the job were interesting. But I have zero interest in casting mundane stuff.

Denis

How much time does it take to melt 60 lb this way from cold. The 28 lb noted is that after degating? Do you have multiple molds that cast at one time, returning the unused melt back to the furnace with a recharge or is it one casting a day? Do you blend your own sand or get a load from a local foundry. Green sand or dry sand.

If you want an interesting cast, then do a cup, a spoon and a saucer all in one piece. This was a standard test for apprentice molders for a journeyman's card years ago.

Tom

One 36" SE requires 41 pounds due to sprue, runner and gates. Of course there are losses due to dross formation, possible spills, fin formation (pretty well have that one licked) and so on. So, it is common practice to melt extra metal which can be poured into another mold and/or recycled.

I started out using sand from a local non-ferrous foundry thinking I'd be using a proven sand and thus eliminating a potential start-up misstep. Well, I learned that sand had been in service for 40 years! It worked fine for bronze, but caused poor surface finish for iron and had poor green strength. A trip to a Canadian foundry supply to buy new olivine sand, bentonite clay and sea coal allowed me to mix new sand from scratch with dramatically better results. That is a good example of the many many process tweaks needed to get a working system in place.

Another challenge involves simple handling of the mold/flask combination which weighs 250 pounds and requires precise lifting, turning, and placement to make a good mold. Chain hoists, barn door trolleys, and a garden cart with a custom hoist were pressed into service.

Then there is a muller to be built to condition the green sand. And the list goes on... This is not an endeavor for the casually interested!

Denis

Where did you learn the foundry arts. What sand testing do you do, moisture by machine or handfull?

tom

TDegenhart said:

Where did you learn the foundry arts. What sand testing do you do, moisture by machine or handfull?

tom

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Indeed, much of the foundry work is "art" since many crucial factors are difficult to measure and on a small scale are often impractical to measure. Various patents have been granted for sand moisture content, clay content, and other additive content measurement that can be done "on the fly" as one is actually mulling sand. That is practical for automobile manufacturing-scale operations for example. But small scale guys end up having to learn by trial and a fair bit of error what the correct moisture content feels like in the hand---the classic squeeze and break test of green sand. I have also found that packing sand into the corner of my molding bench backboard and then cutting out a chunk for breaking testing is a better way way for me to determine the remarkably narrow useful moisture range. For instance, a variation from 3.7% to 4.5% can significantly impact performance. Not easy to feel that small difference! But I can bake out moisture and use a scale to see where I was after the fact. That is not practical on the fly though. It, nevertheless, is helpful to me to go to that effort to start to make sense out of what is going on. Garden moisture meters simply do not work for this due to several factors I tried one. Useless.

Another factor that is not commonly measured is air/fuel mixture of the heating source. I am working on cracking that one using a O2 sensor form a car. In most cases that is also done on the fly by eye alone. That is hardly ideal.

Temperature measurement of molten ferrous metal is also not economically done in small scale foundries as the devices themselves cost 4K or more. Most guys have learned to do that by eye. This is also not ideal and can lead to failures. I have made some significant strides on that which I will be "publishing" some time in the not too distant future. Trust me that those hand held optical sensing devices are completely useless due to dross formation, and other problems.

I apologize for whining, but it may be of some interest to those not familiar to get an idea of the hurdles to be jumped to get good, predictable, and consistent results. Certainly as I started down this path I had no concept of them. (Took a little longer than expected to get to the point of feeling like I had the process reasonably in hand.) But, because of YouTube and a couple of websites where information is pooled, it is possible to get past most of the hurdles. It also helps to be very stubborn and not give up when confronted with repeat failures that could have any number of potential causes.

If anyone is in the neighborhood, they are more than welcome to stop in for a demo. But be prepared to spend some time ramming up a mold, melting iron, and waiting 8 hours to shake out the casting. Ramming up molds of this size takes a little more than an hour. Cutting runners and popping vent holes a bit more time. Melting 60 pounds takes about 3 hours. The next heat is faster though since the furnace is hot and ready to go.

Denis

Added later: I was remiss in not saying that a couple of regional commercial foundry owners were also very sympathetic and helpful. Their operations differed some as they were using a different binder system for their sand were using induction furnaces. They shared valuable insights and took the liability risk on several occasions to let me visit their facilities, wander around visiting with employees, and answered questions to the best of their ability. That is a true privilege. It also doesn’t hurt to have a few loyal friends offering suggestions and cheering you on. A wife willing to ignore long absences while in the shop and tries to understand why one would do such a thing as cast iron is essential.

In the old days, small foundries used either a sand cutter or a Simpson muller. When I started, it was both hand shoveling through a sand cutter for natural sand and a Beardsley-Piper speed mullor. What are you looking to do? Other than the melt control, this is probably the most important part of casting control.

Tom

TDegenhart said:

In the old days, small foundries used either a sand cutter or a Simpson muller. When I started, it was both hand shoveling through a sand cutter for natural sand and a Beardsley-Piper speed mullor. What are you looking to do? Other than the melt control, this is probably the most important part of casting control.

Tom

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I made a pretty satisfactory muller from a vintage heavy duty cement mixer as commercial mullers are few and far between.

I have found that proper sand conditioning is positively essential if I hope to have success ramming up a mold. The complexity of the pattern I made demands a little more attention to detail than a simple wheel or gear so sand moisture and content of clay and coal is critical. That all adds to the fun.

I have a neighbor who is the founder CEO of an internationally known instrumentation company who has become interested in figuring out a cheap and effective on-the-fly moisture meter for the sand. I really hope he can come up with something. Having such a tool would help control that variable better.

Denis

Of course in your case, you don't need a high tech on the fly moisture tester. The way we did it, the sand pile would be watered, then run a couple to times through the sand cutter and covered with plastic. later a sample was taken for moisture testing. Caterpillar had the same problem when I worked there, how much water to add to the sand on the conveyor as it moved to the muller.

Have you had a mold erupt because of too much water yet? A few years before my time too much water was added, the resulting bronze blew out of the sprue and hit the ceiling of the foundry 20' up.

Thinking about the material handling, I would look into a monorail over the furnace continuing to the pouring line and last to the shake out. Use a motor operated trolley to lift the crucible out, transfer it to the pouring shank

Hot, dirty, smelly, dangerous..I loved it. Nothing like a cold beer after a pour.

Tom

TDegenhart said:

Of course in your case, you don't need a high tech on the fly moisture tester. The way we did it, the sand pile would be watered, then run a couple to times through the sand cutter and covered with plastic. later a sample was taken for moisture testing. Caterpillar had the same problem when I worked there, how much water to add to the sand on the conveyor as it moved to the muller.

Have you had a mold erupt because of too much water yet? A few years before my time too much water was added, the resulting bronze blew out of the sprue and hit the ceiling of the foundry 20' up.

Thinking about the material handling, I would look into a monorail over the furnace continuing to the pouring line and last to the shake out. Use a motor operated trolley to lift the crucible out, transfer it to the pouring shank

Hot, dirty, smelly, dangerous..I loved it. Nothing like a cold beer after a pour.

Tom

Click to expand...

You have some ideas I would love to incorporate in my setup. Unfortunately, site limitations prevent construction of an overhead trolley. A full overhead trolley would be great. Not happening though. A bottom-[pouring ladle would be super too. Also not happening. But, there are pretty good work-arounds and that is what I am having fun figuring out.

On-the-fly moisture eval would also be wonderful as it would allow batch-by-batch testing. As it is, I mull my sand in six or so batches. Bakeout takes a few hours. So testing, waiting a few hours, tweaking and retesting is simply not practical for me except as an occasional check to make sure I am not drifting from my desired water content.

I have not yet blown up a too moist mold. I am hoping to avoid that as I never want to be dodging molten metal.

And yes, hot metal is dirty, hot, and somewhat dangerous work. But there is just something about a pot of molten, gleaming, white hot metal that is seductive. And the rush of pouring is pretty intense.

Given your background, I think you would have a great time seeing my foundry.

Denis

MOre than that, working in it.

Tom

Awesome thread! One day I would like to do a melt of my own steel, so I am soaking this all up with fascination!

I own #2 or 3 of the Foster Featherweight cast iron straight edges and I can attest it's the real deal; light stiff and stable.

I've been on the receiving end of many text messages from Denis over the last too years as step by step he worked his way past successive problems from making the original patterns, to vetting commercial foundries, and in the end to building a complete and functioning home foundry of considerable sophistication. It's no mean feat to go from retired physician to building and operating a small home cast iron foundry. My hat's off to him.

Anyway, if my vote counts, anyone needing a 36" cast iron straight edge ready to scrape would be well advised to consider the casting Denis Foster offers. BTW, I don't think $80 is excessive for PCH: the strongly made birch plywood box he shipped mine in required only latches to convert it into a storage/shipping case.

Lucky 7 brought one to the Bourn & Koch Class we had 2 years ago and it's a nice design. Does it second side or a 45 degree on it to use on a dovetail? Or do you have another model that will? It scraped nice, was light and the older guys like me need light, feather light.....lol. I do recall it drooped or sagged a few tenths when Lucky tested it, most do I suppose. We talked about this back then I think in a thread. Good luck selling them. Rich

Richard King said:

.... . I do recall it drooped or sagged a few tenths when Lucky tested it, most do I suppose. Rich

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What do you call "droop or sagged?" Everything is made of rubber one way or another, precision scraped straight edges included. Damn! We are professionals here. We don't toss un-quantified words like "droop or sagged" when discussing high precision scraping references. That's called condemnation by inference. Droop or sagged by how much? How was it measured? Be precise. It's our trade. Words are our tools as much as scrapers and precision references.

The question is how much is the deflection from the force of gravity and how much is acceptable? I read Rich's post and had to wonder what he meant by "droops or sagged". I took straight edge out to my 17" lathe whose bed is the stiffest item in my shop, stiffer by far than my granite flat since the bed casting is a X-braced box 11" deep.

I mixed and matched 1-2-3 blocks to make 4" risers on the flat and bridged the saddle with my straight edge with the riser support on the very ends. Then I set up my Federal EAS 1226 gage amp and EHE 2048 lever gage head to register vertical deflection in the center of the straight edge. I set the gage amp on the +0.0001 to - 0.0001 range where each graduation registers 5 millionths. I cleaned and fiddled until the gage needle returned to zero no matter how I agitated the set-up. I made up a saddle bag of 30 lb (Denis' test weight) of misc small hardware in the sleeve of an old shirt.

With the gage amp zeroed on a bearing point, I lowered the saddlebag over the center of the straight edge arch. The gage amp registered 0.000075" deflection. When I removed the load the gage amp returned to near zero (less than 1/2 minimum graduation. On re-application of the load the gage amp read 0.000070". The reading bobbled but didn't change when I dithered the set-up. When I removed the load the gage amp registered very close to zero. I attribute the small errors to inexact placement of the contact tip on the bearing point. There was some inevitable movement when applying the saddle bag load.

Is that what you mean by "droop," Rich? About 70 millionths for a 30 lb load by actual measurement? That's an actual quantified test result expressed in repeatable numbers based on repeat zero tests and described is detail so there can be no dispute as to method or conclusions.

I don't know if there is a standard for deflection of an arched precision scraped straight edge. I would think without supporting authority deflection as measured by inversion would be no more than 1/4 the total span planarity tolerance. I'm unsure of where along the reference length of the straight edge the tool is to be supported for straightness test. I duplicated Denis' test conditions to avoid confusion.

I've always thought of the wear limits requiring re-calibration as being 0.0003" in any foot and no more than 0.0005" overall times the cube root of of its length in feet. A freshly scraped and calibrated straight edge shall not exceed 0.0001" per foot, and 0.0002 times the cube root of 3 over-all non accumulative. That's my notion not based on a real standard so take it with a grain of salt.

Is there is an actual commercial standard, that is, one recognized by NIST or some other standards organization? I haven't found it. Individual manufacturers of the past have published their own internal standards which are kinda the basis for mine.

not meaning to stir up anything, asking this just out of curiosity

Isn't idea behind the "droop test under load" for such a straight edge more to assess the design and maybe material, and has no real bearing in day to day operation of the tool?

The only test relevant to real world application I can think of would be to test the droop with no load while the SE is bearing on the far ends (set up on riser blocks), if the deflection in the middle is at least 10x less than the precision requirement for the job, then the tool can be considered good for the job. This would be the worst case scenario for a SE, most of time it wouldn't see this.

And more rigid under load in this case would mean higher back of the SE, or thicker in places, which will lead to more weight, and in turn make it more difficult to operate.

For moisture content testing I remember using a small steel flask into which you put a sand sample. Then added a small pill and clamped a cap on with a pressure gauge attached. Shake the flask and the pressure reading gave you the moisture content. I am guessing that the 'pill' might have been something like calcium carbide but there are other possibilities. This kit was a standard tool for UK foundry labs - simple and very fast to use. I haven't worked in a foundry for many years so I have no idea what is current usage, but I am sure that something similar must have been available in the US and probabaly still is.

As an apprentice I can remember beeing asked to get a sample of sand direct from the muller. This was considered the best place to get a representative sample for a whole range of tests. The foundry was in a high volume engine plant and the mullers were large. In order to get the sample, you climbed a ladder up the side of the muller and then with great care, balance and timing caught a bucket full as the rollers came around. I don't recall any accidents but there certainly would not have been much left if you got caught. Health and Safety regulations would have forced a safer way of doing that job years ago.

The moulding sand used for engine blocks had a variety of additives. Bentonite, coal dust, Sierra Leone Concentrate are a few I remember. Then there were the cores - another process for those.

Hat is off to you for your effort in learning how to cast iron. I was fortunate to be able to experience a small iron foundry in operation back in the 1950’s when I received my mechanical engineering degree. Not long after my graduation, all the manufacturing shops of the university were closed. I did have the opportunity a couple of times to experience bronze casting using ceramic shell techniques. I never managed to scratch off from my bucket list having a personal foundry. I have great admiration for your work.