1144 Stressproof
1144 Stressproof
(OP)
I have an application for mower spindles that currently is calling out 1144 Stressproof. The reason that this was chosen, from my understanding, was to help prevent the external threads at one end from stripping out. It has been mentioned to me by a number of people that 1144 Stressproof has a soft center, meaning the stressproofing on penetrates so deep. Is this the case? I have not been able to find any information to substantiate these claims. Can anyone help me? What other materials would you suggest for this application?





RE: 1144 Stressproof
This heavy draft increases the strength, and many times allows Stressproof 1144 to be used in applications without further heat treatment, such as Quenching/Tempering. However, cold drawing affects the surface more than the core, resulting in lower core hardness. Quenching & Tempering produces a more uniform surface, but introduces another processing step, potential for distotion, etc.
One suggestion is to not change the steel grade, but just require a minimum core hardness. Is the steel currently making acceptable threads? If not, then you may want to consider other free-machining grades from LaSalle like Fatigueproof or ETD 150. You can read more about these grades at the following website/.pdf file:
www.machineshopguide.com/pdf/Cutfaster.pdf
LaSalle does not have their own website-- they use space allotted to them at www.suppliersonline.com, whose server is misbehaving today, otherwise I would add the link to this reply. Try accessing the homepage, and then find LaSalle Steel on it.
If you feel that the strength of the part is an issue, using something like 1137/1144/4142/4150 but with subsequent heat treating (Q&T) will provide increased strength, but with increased cost, process time, and potential distortion.
Is it possible to eliminate the machining? You may be able to forge the part (cold/warm/hot?) using a carbon steel like 1038 or 4140, then roll the threads instead of machining them. I'm guessing it was deemed cheaper to machine the entire spindle, instead of this, but you may want to investigate. Best of luck, and if you have any additional questions, just ask.
RE: 1144 Stressproof
www.niagaralasalle.com
It may not be the official web site or anything but it may help you with more information about the ETD and the Stress Fatigue options that Lasalle has. Good Luck.
RE: 1144 Stressproof
If that is the bulk of it then don't bother with a free machining grade and roll the threads. They will be smoother and stronger.
The StressProof line has a good reputation.
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Corrosion never sleeps, but it can be managed.
http://www.trenttube.com/Trent/tech_form.htm
RE: 1144 Stressproof
There was a fairly hairy lawsuit that happened here in Houston a few years back where an eye bolt used on a window washing scaffold failed and the window washer fell from near the top of a sky scraper. The eye bolt was made from a free machining alloy and was manufactured in China if memory serves. Free machining materials have thier place, but you have to be careful how you apply them.
RE: 1144 Stressproof
If there is any impact or alternating loads on the spindle I would seriously consider FatigueProof.