Any problems/advantages using 1018 CRS vs A36 for AXA/BXA toolholders?

Bob Korves said:
the modulus of elasticity of steel
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I think this is difficult for most to get their head around and it is for myself. All of the engineering data I have read lists steel in their shape, size, alloy from the mill in MoE testing but I haven't read anything noting the difference in the steel alloys after heat treatment. With that said, the common terms we use to describe the mechanical characteristics which are affected by heat treating; Ductile (toughness), malleable, tensile strength, yield strength, elongation, would affect the tool produced.

Heat treating and to the degree of hardness chosen still allows for machining to tolerances without moving into a grinding process. I agree that these process are not the norm for the home shop and most require carbide cutting tools.
 
Rustrp said:
I think this is difficult for most to get their head around and it is for myself. All of the engineering data I have read lists steel in their shape, size, alloy from the mill in MoE testing but I haven't read anything noting the difference in the steel alloys after heat treatment. With that said, the common terms we use to describe the mechanical characteristics which are affected by heat treating; Ductile (toughness), malleable, tensile strength, yield strength, elongation, would affect the tool produced.

Heat treating and to the degree of hardness chosen still allows for machining to tolerances without moving into a grinding process. I agree that these process are not the norm for the home shop and most require carbide cutting tools.
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http://www.engineersedge.com/manufacturing_spec/properties_of_metals_strength.htm
The elastic modulus for all steels is ~30 x 10^6 psi. Stainless steel is slightly lower at 28-29 x 10^6 psi.
 
I made six AXA size to start with, cut the dovetail all at once. I should have roughed them in and finished the dovetail after cutting them apart. Some are sloppy but useable. Again the first were 1018 Cr and the later I made some from A-36. The A-36 did machine better. No real dimensional difference as I casehardened them all.
I had three factory blocks and did this as a learning exercise plus to save $$$. I don't think I saved a thing but I learned a great deal. Now I have a CXA and I will buy what I need unless it isn't available.
 
The method of determining the internal stress of a material is to machine away thin layers and then measure the change in dimension at a known location. So the key to machining any material since everything has internal stresses in it is to machine close to the desired dimension. The part will warp due to the material removed. Then measure and adjust for the final cut. If you can stress relieve the material before the final machining that is a great help. The reason when making a fixture to harden and relieve the part before surface grinding is deal with the warping that will occur from machining the non-hardened part and the stress and thus strain that occurs in the hardening and partial relief to reduce brittleness. Do not think casting will be better. The cooling of the metal of a casting occurs from the outside inward so the part will have internal stresses. Plastic molded parts all have lots of thermal stresses built into them. The warpages is local so a large or long part will look like spaghetti when heat treated be it metal or plastic.
 
Bob Korves said:
http://www.engineersedge.com/manufacturing_spec/properties_of_metals_strength.htm
The elastic modulus for all steels is ~30 x 10^6 psi. Stainless steel is slightly lower at 28-29 x 10^6 psi.
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Okay, and I know it was late whe I was attempting to pose the question. How does elastic modulus play into a decision to heat treat a part? My position was elastic modulus is outside of the mechanical properties and tests we use to determine how a piece of material is used, or when an alloy is added to improve tensile strength, resist the affects of heat or cold, wear resistance, impact resistance, ductility, etc. Elastic modulus is proportional based on the force applied through compression or extension and from that degree nothing changed if the part is heat treated. This is a lot of physics which I try really hard to not concern myself with on a daily basis. :)

A 4" length of .250" Sq. HSS prior to heat treating and after heat treating may have the same elastic modulus but the mechanical properties change dramatically after heat treating. I know we are not going to get the hardness of HSS from a case hardened 1018/A-36 but service life is improved greatly. I think the one item or piece missed in the question regarding 1018 and A36 is why 1018 has a higher tensile, less elongation, higher yield strength etc. This is due to mechanical changes caused or induced by the forming of the bar, because the chemical compositions are almost identical. These changes are also afffected if the bar is rolled or drawn (drawn usually has less stress), along with the the different drawing methods. The topic did receive comments on distortion, warping etc. along with the results which may happen during machining. It helps to ask for mill certs from the supplier to get a better picture.
 
Rustrp said:
Okay, and I know it was late whe I was attempting to pose the question. How does elastic modulus play into a decision to heat treat a part? My position was elastic modulus is outside of the mechanical properties and tests we use to determine how a piece of material is used, or when an alloy is added to improve tensile strength, resist the affects of heat or cold, wear resistance, impact resistance, ductility, etc. Elastic modulus is proportional based on the force applied through compression or extension and from that degree nothing changed if the part is heat treated. This is a lot of physics which I try really hard to not concern myself with on a daily basis. :)

A 4" length of .250" Sq. HSS prior to heat treating and after heat treating may have the same elastic modulus but the mechanical properties change dramatically after heat treating. I know we are not going to get the hardness of HSS from a case hardened 1018/A-36 but service life is improved greatly. I think the one item or piece missed in the question regarding 1018 and A36 is why 1018 has a higher tensile, less elongation, higher yield strength etc. This is due to mechanical changes caused or induced by the forming of the bar, because the chemical compositions are almost identical. These changes are also afffected if the bar is rolled or drawn (drawn usually has less stress), along with the the different drawing methods. The topic did receive comments on distortion, warping etc. along with the results which may happen during machining. It helps to ask for mill certs from the supplier to get a better picture.
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I agree with all that, Russ. What I was talking about is people who say they are going to make a boring bar out of 4140 and harden it so it will be lots stiffer than a same sized mild steel bar. T'aint so. You have to go with a higher Young's Modulus material (like carbide) to have a stiffer result.
 
NEAT info and a good learning discussion. But (or butt), I have only been doing any machinery works for 5 or 6 years and am still a noob. I went to a local machine shop (in business 65 years) and asked them what they used as they make most of their own (found out thru a friend) as well as custom one time use ones. THEY USE ALUMINUM! Not an exotic mix either. 7075 prefered but even 6061, tho they like Fortal (very like 7075-T6)
They say even with heavy production they last several years (unless dropped LOL) without issues. I bought sme and have made several. I don't do heavy qty but I do cut heavy sometimes (told you I was still a noob) and have never had any issues other than dinging them up. Cheap, easy to make and will probably last longer than the hobby does, or me! So instead of hours to make/harden. etc., as well as $$$, a few minutes and for very little money I have new ones when needed. Even reuse the hardware from the old ones. I keep several without slot for "special" use if needed.
FWIW
 
p.s. to the comment "My position was elastic modulus is outside of the mechanical properties".
In a prior life I was a Safety Engineer on the Shuttle program (and others) and had to deal a LOT with elasticity modulus of different materials. In raw metals IT IS PARTIALLY DETERMINED BY MECHANICAL PROPERTIES!
A steel that has a great amount of one material in its makeup than another, that gives a softer bond between molucles, will be different than anoth "real close" to that mixture. 12L14 is a good example. The elasticity moudulus for it is FAR greater than something like 4140 or cheap 1018. Look 'er up, don't believe me or anyone on a forum for "facts". Besides that way you learn it not just hear it!
Paul
 
Rustrp said:
My position was elastic modulus is outside of the mechanical properties and tests we use to determine how a piece of material is used, or when an alloy is added to improve tensile strength, resist the affects of heat or cold, wear resistance, impact resistance, ductility, etc. Elastic modulus is proportional based on the force applied through compression or extension and from that degree nothing changed if the part is heat treated.
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This was my comment in it's entirety, and I will add, the aluminum alloys you mentioned were heat treated. I'm sure the molecular makeup of a material does affect and relate to it's mechanical properties. The decision to heat treat or not to heat treat (especially steel) based on cost and the resulting quality is evident in many products made offshore.
 
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