Tek-Tips is the largest IT community on the Internet today!

Members share and learn making Tek-Tips Forums the best source of peer-reviewed technical information on the Internet!

Register Log in
  • Congratulations MintJulep on being selected by the Eng-Tips community for having the most helpful posts in the forums last week. Way to Go!

Search results for query: *

  1. Screwman

    Torx screw star geometry

    The ISO dimensions are an approximation issued for gaging purposes, since the actual Torx shape is trademarked. The manufacturing dimensions are only available to Torx licensees. Try this link to contact that proper person: http://www.acument.com/licensing/index.asp
  2. Screwman

    Fine thread bolts - do they back off

    The close-up pictures of the failed studs show what looks to be a very brittle fracture surface and the one shot shows what looks to be inclusions in the weld area. I wonder if the person welding has the weld parameters all out of whack and is creating a massive heat affected zone. It looks...
  3. Screwman

    Bolt Pre-stress

    Sorry to say, but Skidmore devices are only considered accurate if the spring rate of the assembly and gage as taeted is the same as in the actual joint as assembled, and it usually isn't even close. A load cell sandwiched into a milled out area of the actual assembly (replaced by a hard steel...
  4. Screwman

    galvanized A35 structural bolts

    Were the nuts overtapped for use on galvanized bolts? Do the pitch diameters on the bolts measure within the allowable tolerance. Either the nuts need to be overtapped after coating or the bolts undersized prior to coating. Check out the A325 spec for all the details.
  5. Screwman

    shear stength of #12 tek screw

    Please don't try to use a TEKS screw in any location where it will see structural load. These are generally case hardened and as such are succeptable to all sorts of nasty failure modes. They were intended to fastener sheet product (with a few noteable exceptions) and not for structural use.
  6. Screwman

    countersunk structural fasteners?

    Any type of a flush head fastener with a recessed drive in it will fail thru the head and recess at a tensile load lower than the ultimate strength of the threads. You have to reduce your allowables and use more/larger recessed head fasteners than you would the same hex head structural bolts...
  7. Screwman

    Strength of 1/4-14 Sheet Metal Screws in 12g SS

    Cory, Good response. Best idea is make em and break em. SMS threads are highly variable in results, so make sure you use a large enough sample size to ensure that you have statistcally valid results.
  8. Screwman

    Strength of 1/4-14 Sheet Metal Screws in 12g SS

    It's not the strength of the screws that is so questionable (although they are pretty questionalbe from a mechanical standpoint too), it's the unknown strength of the one "thread" that is formed into the sheet metal. Slight changes in hole size and even the clearance hole size can reduce the...
  9. Screwman

    Counter sunk taptites

    Ah, interesting question. On any multi-bolt c'sunk application, the true position of the holes becomes critical to get fastener bearing all the way around the bearing surface of the hole. There is also the fact that there is more of a tendency for the c'sunk parts to lose clamp load than a...
  10. Screwman

    Fastening solution required

    The drive rivet will have very low pullout strength and will resist only a nominal shear load. If it was my design, I would stick with the Taptite, it will give much higher performance.
  11. Screwman

    Axial loads produced by fine & course pitch threads with equal torques

    The thing to remember is that in the commercial (read automotive) world, most joints are designed with massive overkill to allow for a lot of assembly variation. You can pisk up a car with a single M6 PC10.9 bolt and yet we use 3 M10 bolts to holt down the battery tray. When choosing an...
  12. Screwman

    Tensile and Shear Strength for #10 1.25ö PHSMS fasteners into aluminum

    I agree with Cory. The fact that someone is looking for mechanical properties on a sheet metal screw is enough to cause the caution flags to good up to full staff. This type of fastener is not intended for structural loading the performance is entirely dependent on the condition and size of...
  13. Screwman

    Torque to apply w/ Prevailing Torque nut.

    You may want to consider changing to a torque/angle system where you tighten to a relatively low snug-fit torque and then the gun is programed to rotate the nut a set number of degrees further to achieve the final assembly. This method removes a significant amount of the variation resulting...
  14. Screwman

    explosion pressure release screws part 2

    Try this link: http://www.dablackcompany.com/fasteners.htm I think this is what you have in mind.
  15. Screwman

    What purpose does reduced major dia fastener serve?

    Most of the NAS procurement specs require threads to be rolled (after heat treatment). A high quality aerospace grade thread will look like it has been ground.
  16. Screwman

    What purpose does reduced major dia fastener serve?

    Moose, Exactly. For these parts there are no cut threads allowed (and no manufacturer that I know would do that). Most majors are required to be a minimum of .001 under the grip diameter and then there are those parts which require much more reduction in major diameter for clearance.
  17. Screwman

    Bolting

    Effheat, The issue with recessed heads is failure from the underhead radius into the recess, as a result of having either a large and/or deep recess in the head of the part. You end up on flush head parts with a catch 22 for high load applications where either you put in a nice big recess to...
  18. Screwman

    Brainstorming ideas aluminum auto chassis construction

    For a lightweight construction look at the old tube frame cars of the mid 60s, some of them are quite light, using steel tube. After that we get into riveted aluminum sheet construction. Check out a mid 70s Chaparal or Lotus to see what you can do with structural rivets and aluminum sheet...
  19. Screwman

    Bolting

    Contact Acument at Taptite in Belvidere, IL.
  20. Screwman

    T-47 Torx Fastener

    Yep, Corey is right. This is not anything that was created by Camcar or any of the Torx licencees. I think this is a foolish part that GM came up with. He's right that it isn't a true Torx but a 'made up' shape that is similar to a Torx. In most cases you should be able to use a T-45 to work...

Part and Inventory Search

Back
Top