Looking for a shop in the USA that can headless set screws and shear test them
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  1. #1
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    Default Looking for a shop in the USA that can headless set screws and shear test them

    I have a client that is having troubles finding a screw machine shop that can make brass slotted or socket headless set screws. There are many shops out there that can make them but have no way to shear test them to verify what they shear at. Specifics can be provided, for general, the sizes he is looking at are from 1/4-20 up to 1/2-13 and in different lengths of 5/16 to over 3/4" long. Material grade and selection is open, suggested grade is 360 half hard brass. Quantities are 3000 plus in a given size. We can provide specifications for a shear fixture the sample screws go in. Nothing fancy, real simple, about 3" in diameter and about 2" long. Amount of force to shear three shear screws, required for the fixture will hold, not to exceed 12,000 lbs. We are not trying to shear to a specific value, just need a verification of what the screws shear at from each heat of material used. Does not have to be certified by a testing lab even though that might be an good idea. The industry this is used in is the oilfield down hole tool market.

    Anyone set up to something like this, let me know. You can post here or send me a PM.

    Ken

    Monrator, I may not have this placed in the right forum, please move if you see fit.

  2. #2
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    I think the requirement for a special shear fixture is what the problem is. There are already 2 standard fastener shear types out there. I'd suggest double shear per NASM1312-13. There are many test houses that could do this test for you after you have them made.

    https://www.instron.us/en-us/testing...r/nasm-1312-13

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  4. #3
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    Quote Originally Posted by Triaged View Post
    I think the requirement for a special shear fixture is what the problem is. There are already 2 standard fastener shear types out there. I'd suggest double shear per NASM1312-13. There are many test houses that could do this test for you after you have them made.

    https://www.instron.us/en-us/testing...r/nasm-1312-13
    I agree, this is not standard. We don't do double shear in this material. In actual use, the shear mechanism may have up to eight screws installed for proper operation of the tool. And for the shear fixture to load properly, it needs at least three screws. Oh, the fixture has a .015" clearance built into it to simulate the shear as it would see in the oil tool.

    We don't follow any standard on shearing, even though the testing may be done on a Instron testing machine.

    Ken

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    You don't think you could correlate the double shear in a standard fixture to the single shear in your application? It might not exactly be double shear x 3 / 2 but there is likely a coefficient very close to it. Custom shear fixtures can be very expensive and frequently get broken in testing so it will scare off most suppliers unless there is tons of money to justify it. You might be better off subbing the screws, test fixture, and testing too different places. Each shouldn't be too hard to find individually. You will take on the liability of the test fixture.

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    Quote Originally Posted by Triaged View Post
    You don't think you could correlate the double shear in a standard fixture to the single shear in your application? It might not exactly be double shear x 3 / 2 but there is likely a coefficient very close to it. Custom shear fixtures can be very expensive and frequently get broken in testing so it will scare off most suppliers unless there is tons of money to justify it. You might be better off subbing the screws, test fixture, and testing too different places. Each shouldn't be too hard to find individually. You will take on the liability of the test fixture.
    Nope! Shear fixtures are very cheap to build and heat treat. At least for us they are. Ken

    BTW- the double shear fixture Instron uses and sells is for bolts. Our shear screws are only about 3/8" long. Plus for what Instron gets for that one fixture, I can build 10 of ours for the same price!

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    I mean, why not send them the fixture?

    If supplied a fixture, method of ops, and a spec, it would be pretty straightforward to test as you go, and pretty easy to quote the time involved.

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    I used to take auto engine parts to Detroit Testing Lab here in Michigan.
    likely a similar shop in Texas.
    You get a print-out of the facts you need.
    Small parts you can UPS to Michigan.
    It is good to have the paper not just your home made test device IMHO>
    Detroit Testing Laboratory Inc
    in Warren, MI 48092

    - MLive.com

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    I have been making oilfield shear screws for 35+ years. The customer has many times noted a shear strength on the drawing, but just given us usually plus or minus .005 on the dog dimensions. A few years ago a customer asked us to dial in the shear strength using his testing fixture. I ran some samples and took them to his location to break them. On that one we changed the tool radius to change the minor diameter to increase the shear value. There is another that has to be adjusted on a disk that shears off, the same customer provides the gauge that I put in my old South Bend and I break them and adjust them in. If you can check these with those easy to make fixtures I can run them.

    In a long ago post you mentioned that you made the drawing for a long named integrator screw, I think this is the same one running here: Present customer calls it a GB screw: YouTube

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    Quote Originally Posted by FredC View Post
    I have been making oilfield shear screws for 35+ years. .................................
    In a long ago post you mentioned that you made the drawing for a long named integrator screw, I think this is the same one running here: Present customer calls it a GB screw: YouTube
    Yep, that's them. Integrator, I know that name and where it came from. Some of these screws are for that same tool made by others. Can you PM me your contact information and I pass this on to my customer?

    Thanks, Ken

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    PM sent. I had to clear out messages. Have not found out how to selectively delete them. Made copies I think, then deleted all.

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    FredC, click the square at the right hand side of your message in the inbox or outbox view. Selected message bar will turn yellow & checkbox will turn blue.

    Then go down to the 'Selected Messages' box at the bottom of the message list, and click the little arrow. Box will expand and give you a choice of various fates to befall your selected messages. Choose Delete if that is your desire...

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    Quote Originally Posted by Chip Chester View Post
    FredC, click the square at the right hand side of your message in the inbox or outbox view. Selected message bar will turn yellow & checkbox will turn blue.

    Then go down to the 'Selected Messages' box at the bottom of the message list, and click the little arrow. Box will expand and give you a choice of various fates to befall your selected messages. Choose Delete if that is your desire...
    Chip Chester, that was easy. First selection was move to folder, if you create folders to organize and store important messages do the folders contribute to the capacity limit?


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