18" straight edge casting

I've seen Gary Martin's castings mentioned several times on this forum, but since these straight edges are not yet on his web site, I thought the attached photos might be of interest to the members of this forum. His contact information is on his website at http://www.martinmodel.com/

Gary is an independent patternmaker and sells castings of engine kits, flywheels for model engines, pattern filer kits, etc., as a sideline to his patternmaking business. He is located in Scappoose, Oregon.

I photographed the straight edge for Gary, and also some angles that might be of interest to folks looking for scraping projects. The castings are fully annealed and ready for machining - they obviously will need additional heat treatment for stress relief before scraping.

The 18" straight edge casting sells for $95, and the 30/60/90 angle (nominally 7"x12"x14") for $50. Plus shipping, but I think he told me that shipping is usually less than $20. I think he has four or five straight edge castings and three or four of the angles.

Full disclosure - I'm not involved with Gary's business in any way, although I helped him out with some of his photography as a favor. I occasionally attend his Thursday night patternmaking workshop. I made the pattern for the 30/60/90 angle at the workshop.

Douglas

One of the students who took the Texas class had some of those and they look good. I can't understand how he can make the pattern and casting and sell to make a profit. But I know hobbyists are looking for deals. My Casting costs more, but mine are stress relieved and no future treating is needed. Gary Cude down in Texas also makes 18"ers. Rich

Would be nice to stop by his shop and then Wesco boots on the next trip to the PNW.

dsymes said:

View attachment 193699 View attachment 193700

I've seen Gary Martin's castings mentioned several times on this forum, but since these straight edges are not yet on his web site, I thought the attached photos might be of interest to the members of this forum. His contact information is on his website at http://www.martinmodel.com/

Gary is an independent patternmaker and sells castings of engine kits, flywheels for model engines, pattern filer kits, etc., as a sideline to his patternmaking business. He is located in Scappoose, Oregon.

I photographed the straight edge for Gary, and also some angles that might be of interest to folks looking for scraping projects. The castings are fully annealed and ready for machining - they obviously will need additional heat treatment for stress relief before scraping.

The 18" straight edge casting sells for $95, and the 30/60/90 angle (nominally 7"x12"x14") for $50. Plus shipping, but I think he told me that shipping is usually less than $20. I think he has four or five straight edge castings and three or four of the angles.

Full disclosure - I'm not involved with Gary's business in any way, although I helped him out with some of his photography as a favor. I occasionally attend his Thursday night patternmaking workshop. I made the pattern for the 30/60/90 angle at the workshop.

Douglas

Click to expand...

If they are already fully annealed I guess for the guys on the forum here who don't have a furnace-do you feel it is necessary to stress again after you do the initial rough machine?? I would say yes but would like some other opinions.

My guy cooks my SE's for 20 hours at 1100 deg's F. To me annealed means heating up and cooling off in a short time.

My understanding is that fully annealed gray iron is typically heated up to around 1600F and then reduced 50F-100F/hour down to around 600F, and then air cooled. This results in conversion of pearlite to ferrite, and the resulting iron is relatively soft and easily machined.

My sources are:

http://www.dura-bar.com/resources/upload/Dura-Bar-Heat-Treating-Guide.pdf

http://www.dura-bar.com/resources/upload/resourceGuide_05_heatTreating.pdf

My solution to the problem of stress relieving after machining has been to use the small heat treating furnaces at the local community college which are just barely big enough to fit the 18" straight edge, wrapped in stainless steel foil to minimize decarburization. I heated to 1100F, held for two hours, and the reduced 100F/hour to 600F, and the turned the oven off and came back the next morning (below 600F, the oven lost heat at less than 50F/hour).

I should add that I am not in any way an authority on this stuff, and have generally followed Richard's suggestions as well as looking up whatever resources were easily available on the web, e.g., Dura-bar's guides, etc.

Douglas

I used to have another company do it 2 times. After casting they heated it to 1100 and held it there for 2 hours and then lowered it 200 deg intervals for 2 hours and then shut off the furnace. Then we roughed machined it and did it again and finish machined it. Every now and then I had someone say it moved. This new guy is a degreed engineer and he says one time is all you need. I have heard that if you heat the CI higher then that little hard spots as hard as glass appear in the IRON. Make it a bitch scraping.
The bottom line is My method works and if his method works, so be it. But I will stay with my method. Rich

PS: I do the Dur-a-Bar I make SE's out of too, the same way

The right angle square I scraped at the Springfield Vt class came from Gary Martin 5 or six years ago. it is indeed a nice casting. Gary Martin is a great guy to deal with to boot.

cash said:

If they are already fully annealed I guess for the guys on the forum here who don't have a furnace-do you feel it is necessary to stress again after you do the initial rough machine?? I would say yes but would like some other opinions.

Click to expand...

Interesting question. But, I have to wonder, is scraping not machining just as much as planing or milling? I don't have the answer to that question. But scraping is just a slow milling or planing operation. All involve peeling away metal and causing intense but very localized and brief heating where the chip separates from the base metal.

Is there a major difference in the effect of scraping vs milling and planing with respect to stress induction. And if there is (likely), can the milling and planing stress be mitigated to nearly that of scraping by taking final passes that are very fine? That is an important question I think.

Taken to the extreme the (il)logical conclusion might be that the piece should be stress relieved after every scraping pass.

Or maybe not. It seems that most folks have concluded that stress relief ( but not annealing) is an important step after casting. That seems to work. Like anything it can be carried further than needed. But, I do wish I knew the answers to some of the questions I posed in this post.

Denis

"Stress Relieving consists of heating the steel to a temperature below the critical range to relieve the stresses resulting from cold working, shearing, or gas cutting. ... However stress relieving does not change the material properties as does annealing and normalizing."

I had Stan hang his straight-edge and wring (hit the top, bottom, braces, for say 5 minutes tapping med soft, it's like a ringing a tuning fork) with a soft blow hammer 2 or 3 times while he scraped it. I had him check it on the blue and hinge it, then wipe it off and wring it, then blue it and hinge and he said it changed a little. I have been using this procedure for years and my Dad used it for years. When I taught in Germany at the rebuilders shop they did it too. So it is a method passed down by craftsmen I would say for a long long time.

if you only need to heat treat cast iron to 1100F for a few hours, or a few days, it makes no difference, you can get to that temperature with just fiberglass insulation and a heating element from an oven.

To give you an example of this: about a year ago I heated a 350 pound weldment, 7 feet long made from 3 layers of 9 inch channel iron.

Its outside surface area (for instructional purposes only) was 9 inches on a side, 7 feet long. wrapped with 1 layer of r-12? 2x4 household fiberglass insulation Edit: 2 layers. heating element was 7 feet long, 3500 watts, heating element was inside the weldment. It took something like 6 hours to get it to 1000F, and it cooled off fairly quickly. it was outside in 50F temperatures.

anyhow: to heat treat a 200 pound, 6 foot long straight edge, you should be able to bailing wire wrap a 3500 watt oven heating element to the length of it, wrap it in fiberglass and my biggest concern is the temperature difference between the top and the bottom. you probably want two such heating elements, one on both sides. or find a piece of channel iron you can set the straight edge in to spread the heat . so the cross section would look like this I~]

I is the straight edge ~ is the heating element ] is channel iron. wrap this up in a spiral of 2x6 insulation and you will should find 3500 watts can heat it up plenty fast. it would be good to find a variac or industrial sized dimmer (scr, triac, phase control heater etc) to modulate the power. the 2400 watt electric range elements should uncoil to be be about 4 feet long and that's enough for a 4 foot straight edge.

1200 watt small range electric oven coils should be good for a 2-3 foot straight edge.

don't worry about hanging this whole assembly from the ceiling with bailing wire. it will hold up. 1100F is not that hot. 1600F is another story. yes the electric oven range elements will hold up at that temp. the fiberglass insulation will not

So, johansen, it sounds like you have some working knowledge of oven heating elements. I, and I suspect, a lot of us do not. How are they constructed? Nichrome wire wrapped in an insulator all of which is in the external tube we see? How much bending and rebending will it tolerate without breaking? Could it be cut to length?

With respect to stress relieving a straight edge using one, it would seem crucially important to maintain very uniform heat throughout the casting. I would worry about applying the element more or less directly to the casting. But creative minds might be able to dream up a workable solution if the working properties I asked about were known. So, I'd appreciate being filled in on them a bit...

Denis

I just had an email from Gary who is somewhat computerphobic (which is probably why his website is not up-to-date). He asked me to correct some of the information on the angles. There are now two angles on his pattern board, the 30-60-90 shown in the previous photo and also a matching 45-45-90. Since he has them cast together, he wants to sell them as a pair for $100 with free shipping in the continental USA. See the attached photo of the two castings. The nominal dimensions on the 45-45-90 are 9.5"x9.5"x13.5".

This post started out as a favor to Gary who is a friend and a very talented patternmaker and woodworker. However, he needs to get this stuff up on his web site. So this is the last post I will do about this stuff. If you have questions, please direct them to Gary (http://www.martinmodel.com/)- he's a great guy and will be glad to help you.

Douglas

Richard King said:

I had Stan hang his straight-edge and wring (hit the top, bottom, braces, for say 5 minutes tapping med soft, it's like a ringing a tuning fork) with a soft blow hammer 2 or 3 times while he scraped it. I had him check it on the blue and hinge it, then wipe it off and wring it, then blue it and hinge and he said it changed a little. I have been using this procedure for years and my Dad used it for years. When I taught in Germany at the rebuilders shop they did it too. So it is a method passed down by craftsmen I would say for a long long time.

Click to expand...

Stress relieving via high-frequency vibration is a real effect. Race car frames that are poorly triangulated depend on the tension stresses of welding for their stiffness, and lose it in a matter of weeks, with the result that the spring rates have to be changed from what they were when the car was new. This is commonly called "metal fatigue," which of course it is not, it's simple stress relief. There is a commercial process for vibratory stress relief. You can do the same thing with a stress-relief anneal in a furnace, which is a short cycle compared to a full anneal which involves shutting the furnace down for the weekend and leaving the item in it. Don't know how much it matters in gray iron, but the difference between stress relief or a "process anneal" in cast 4140 can be 30Rc versus single digits. Helluva difference in starting point for a work-hardenable material.

I use and get my advice from a professional heat treater. I have discussed my past issues with another hear treat company and how the other methods failed from time to time. I have over 50 years experience and my Father a known expert in straight-edges, machine rebuilding and scraping used the hang from a hook and wringing the Cast Iron Straight-edges and have personally seen how it works when scraping a Straight-edge and they move! We do this to prevent them from moving after you achieve 40 PPI.

I don't offer guesses or might work answers to questions on here. I offer proven solutions and techniques. I will gladly give out the name of my "EXPERT" who does Heat Treating as a professional, who does certified aero-space work. PM me. I doubt he wants dozens of phone calls with questions from hobby guys though. Rich

PS: If anyone wants anything planned after you stress relieve it. Steve Watkins the owner of the Beast down in Texas can help you out for a low price.

dgfoster said:

So, johansen, it sounds like you have some working knowledge of oven heating elements. I, and I suspect, a lot of us do not. How are they constructed? Nichrome wire wrapped in an insulator all of which is in the external tube we see? How much bending and rebending will it tolerate without breaking? Could it be cut to length?

With respect to stress relieving a straight edge using one, it would seem crucially important to maintain very uniform heat throughout the casting. I would worry about applying the element more or less directly to the casting. But creative minds might be able to dream up a workable solution if the working properties I asked about were known. So, I'd appreciate being filled in on them a bit...

Denis

Click to expand...

yes the uniform heat is critical, for a camel back style straight edge you also don't have a lot of thermal conductivity connecting the two sides together, relative to the surface area and thermal mass of the business side of it. But that depends on the casting. you may need to place the part inside a steel pipe of thick cross section, or two C channel beams on both sides to get a temperature difference of say, less than 25 degrees from the top to the bottom. temperature differences (high in the middle, cool on the ends) probably not nearly as big a deal.

regarding oven heating elements. the inside element is coiled up, its easily double or triple the length of the element. I think they fold the nichrome sheet metal around the element and laser weld it while its being filled with ceramic powder. The outer casing is cheap nichrome. (its not kanthal A-1 which is 40$ a pound) I don't know the alloy but it holds up to oven, range use, at red-orange hot temperatures for years without corroding.

most of the heating elements i've messed with were rather old, so the outer cover probably had a lot of grain growth and you can break it while straightening it. if you buy a new one it will probably be a lot easier to straighten.

I'd say there's less than 50-50 odds you can cold straighten the factory bends without failure if its a used element. its much easier just to heat it up with a torch.

Water heater elements are not suitable. they are copper tubes that are electroplated with various elements, nickel, copper, chrome, etc.


its not worth the trouble to cut the element to length, you could cut the element and spot weld the nichrome to the nichrome tube, using the outer tube as the electrical return circuit. a crimped joint will not hold up, it may be possible to braze the joint if you don't have a spot welder but copper corrodes very quickly at high temperatures.

johansen,

Thanks for the information. Knowing a little more about almost any aspect of our physical world can't hurt. It may not have direct application in my case to something like heat treating a CI straight edge which I get done by a commercial heat treater for very little money. His process is based on one approved by his in-house metallurgist and is consistent with a scientific study investigating thermal heat treating and "alternative" forms of stress relieving CI done about 70 years ago by the Navy. It is very simple. They load up their room-sized oven with literally many tons of castings, heat them to 1100F (1050 is probably a threshold temp for stress relief with not much happening below that temp)and hold them for a couple hours at that temp. They then simply turn off the oven which very slowly cools over the next 8 to 12 hours to well below the 1000 mark and then remove the castings. This is a process they have used successfully for a couple of decades making castings for a wide variety of mission-critical applications in refineries, smelters, and general industry. I can only vouch for the casting made for me which have proven to be very stable and very nice to scrape.

Here are the conclusions of that 20 page article which I copied and pasted and then proofed to remove, I hope accurately tons of typos related to copying PDF material : http://www.dtic.mil/dtic/tr/fulltext/u2/620556.pdf

CONCLUSIONSRelaxation Tests indicate that:
(1) If the initial stress and the composition of specimens are the same,
the relaxation rate and degree of stress reduction increases as the temperature
Is increased.
(2) Rate af stress reduction is very slow below 1000F.
(3) Rate of stress reduction is most rapid during the first hour at
temperature, and decreases as the time at temperature increase..
(4) For any given temperature, the higher the initial stress, the faster
the initial relaxation rate, but the longer the time required to reach a
specific residual stress level.
(5) Alloy irons require higher temperatures and/or longer holding times
to reach the same stress level as plain carbon iron Stress Wheel Tests indicate that:
(1) Two hours at temperatures below 800F are ineffective, whereas at
temperatures above 950F substantial stress reductions are effected in the
same time.
(2) The greatest reduction of internal stresses occurs during the first
hour at temperature.
(3) Heat treatment at 600 for 24 hours shows practically no.stress
reduction.
(4) Air cooling after stress-relief heat treatment may introduce considerable
additional stresses which do not develop with furnace cooling.
Other Tests Indicate that:
(1) Indoor aging is an ineffective method for stress relieving.
S(2) Alternate heating and cooling of stress wheels between OF and
220F products only a very slight stress reduction.
(a) Corrosion o! stress wheel, with a mineral acid results in a very
slight relief of internal stress.
(4, The resistance of the mold sand may hinder the contraction of A
casting in such a way as to materially increase the internal stress.
The relaxation machine gives a good indication of the stress-relief
characteristics of gray cast iron and provides this information more easily
than can be obtained from actual castings.

My edit: I love it when DATA and SCIENCE are available to help reduce conjecture.

So, you never know when the heating elements you describe might be useful. And I appreciate the info provided. It sounds as if they are not particularly easy to work with.
One final question is whether the surface of the household oven units are electrically charged or does the glowing red tube simply provide protection and insulation to the enclosed nichrome wire?

Denis

dgfoster said:

So, you never know when the heating elements you describe might be useful. And I appreciate the info provided. It sounds as if they are not particularly easy to work with.
One final question is whether the surface of the household oven units are electrically charged or does the glowing red tube simply provide protection and insulation to the enclosed nichrome wire?

Click to expand...

They aren't hard to work with, i just can't guarantee you that you can straighten them cold, i suspect you can straighten new ones cold, but they work harden as you bend them so its easy to over bend part of the curve you're trying to straighten and break it, where as if you supported it in a vise or something it would have been successful, treat them as you would work hardened copper hot water heater flex pipe. You don't have to get them that hot to bend them, a small propane torch is adequate.

the outer surface is isolated electrically, but it should be grounded.

Richard King said:

I had Stan hang his straight-edge and wring (hit the top, bottom, braces, for say 5 minutes tapping med soft, it's like a ringing a tuning fork) with a soft blow hammer 2 or 3 times while he scraped it. I had him check it on the blue and hinge it, then wipe it off and wring it, then blue it and hinge and he said it changed a little. I have been using this procedure for years and my Dad used it for years. When I taught in Germany at the rebuilders shop they did it too. So it is a method passed down by craftsmen I would say for a long long time.

Click to expand...

I did this with my 3' straight edge, as advised by Phil down here. Hung it exactly as you described. I started with a deadblow hammer, but the novelty of standing there playing wack-a-mole with a straight edge soon wore off. So I quickly turned up a nylon face for a flat rivet set and used a 2X rivet gun on it. Worked a treat! Without the nylon cover the rivet gun will peen the surface, exactly the opposite to what you need. I'm sure a regular air chisel or similar would work just as well, I just like the ability to throttle on the rivet guns.

dgfoster said:

Interesting question. But, I have to wonder, is scraping not machining just as much as planing or milling? I don't have the answer to that question. But scraping is just a slow milling or planing operation. All involve peeling away metal and causing intense but very localized and brief heating where the chip separates from the base metal.

Is there a major difference in the effect of scraping vs milling and planing with respect to stress induction. And if there is (likely), can the milling and planing stress be mitigated to nearly that of scraping by taking final passes that are very fine? That is an important question I think.

Taken to the extreme the (il)logical conclusion might be that the piece should be stress relieved after every scraping pass.

Or maybe not. It seems that most folks have concluded that stress relief ( but not annealing) is an important step after casting. That seems to work. Like anything it can be carried further than needed. But, I do wish I knew the answers to some of the questions I posed in this post.

Denis

"Stress Relieving consists of heating the steel to a temperature below the critical range to relieve the stresses resulting from cold working, shearing, or gas cutting. ... However stress relieving does not change the material properties as does annealing and normalizing."

Click to expand...

Yes-this is what I am getting at, when you would originally cast the part you would want to do a full anneal, 1600 deg, hold for 4 hours and then slow cool.

Then when you start machining and you get thru the "crust", I don't care if you machine, plane, scrap, have the old lady take her egg beater to it, my feeling is after this initial machining process it is a good idea to then do a stress relieve, 1200 deg or so, hold 4 hours and slow cool.

Note, on ANY stress or anneal operation, I have found the most important part if the process is the SLOW COOL.

As far as our straightedges go we are discussing here, I think once you would have machined as get another stress on it you should be good.

I guess another trick we could do-when you receive your casting and it has had the initial anneal on it, toss it outside for a year, this will help the cause as well with temp changes ect, well at least for us in the North.