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Hi, I am trying to bring this pa

Hi, I am trying to bring this pa

Hi, I am trying to bring this pa


I am trying to bring this part in-house to save money, improve the quality and appearance of this part. This is a "door latch-spring" application that latches two vertically bi-parting dumbwaiter elevator doors. The "v-notch" latches onto a 3/4" round stock to secure the two halves of the vertically bi-parting elevator doors. The design goes back at least 6 decades, maybe more. The latch-spring is made from T301 3/4-hard stainless that has a dimension of 0.052" thick X 0.390" wide X approximately 7.0" long in the formed condition.

Material: T301 3/4-hard Stainless.

1. I looked up and noticed that several vendors have the T301 3/4-hard Stainless in 0.044" and 0.050" sheet and strip forms.
2. I want to see if I can arrange the part in the flat, and laser cut it by nesting and "kiss-cutting" from say a standard 48"X96" sheet. I would arrange the parts so that a tiny "bridge" is left at each end, and is connected to a 1"-2" wide carrier strip. Then I would either shear this 1"-2" wide carrier strip on a shear, or manually cut the bridges off with a small cut-off abrasive wheel.

My questions are:

1. Will the heat from the laser have any ill effect on the part? From the light brass-color heat dis-coloration, I have assumed that the part was formed and later tempered? Am I correct to assume that the the vendor used 301 3/4-hard S/S and then tempered the part after forming? If so, what is the temper specs that I need to give to a heat treating company?

2. I did a search and only Earle M. Jorgensen offered 301 3/4-hard stainless steel at 0.050" thickness in 48"X96" sheet. However, they only offer the material in 1/4-hard and 1/2-hard condition.

3. Since tempering will increase the tensile and yield strength, can I use 1/2-hard condition 301 S/S and bring it to 3/4-hard tensile and yield strength after tempering it?

4. The hole is 0.157". What kind of tool steel and coating should I use to get the best life from my punches? This is assuming I would punch the part or add the holes after forming to hold edge-to-hole tolerance since I have not build a blanking tool or forming tool yet. Actually, I need help here also. :)

5. The reason I want to use a laser to cut the part is because I don't want to damage my shears when shearing this part.

6. Quantity is approximately 150 parts per year unfortunately.

Any help is greatly appreciated!


Trung Do

RE: Hi, I am trying to bring this pa

You need a copy of ASTM A666. The various tempers for different alloys have different strengths.
The heat from laser cutting is very shallow, it is not an issue. the edges do have some re-cast material on them and it might be good to give them a vibratory abrasive treatment to remove some of the rough edges.
The discoloration is heat tint from a post forming stress relief, spring formers do the same thing.
It is usually 600F for 30 min. The part will flatten out a little when you stress relieve so you may need to over-form slightly. This takes trial and error.
The heat tint does reduce corrosion resistance, but if it has never been a problem then don't worry about it.
The material will never get stronger than it starts out, there is no heat treatment that will make it stronger.
You should be able to use tool steel punches and forms. After all you aren't making very many. Carbide would last longer, but probably not worth it. I would punch holes, and then register off of them to form.

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P.E. Metallurgy, Plymouth Tube

RE: Hi, I am trying to bring this pa

I looked in A666. There is no spec for 3/4 hard 304. The only alloys listed at 3/4 and full hard are 201, 205, 301, 302.
Nearly all of the alloys are listed at 1/2 hard.

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P.E. Metallurgy, Plymouth Tube

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