Announcement

Collapse
No announcement yet.

Shear strength of bolts, check me on this.....

Collapse
X
 
  • Filter
  • Time
  • Show
Clear All
new posts

  • DR
    replied
    Originally posted by DrMike View Post
    Yes, it's exactly like that in configuration, same flywheel and crank shaft orientation. But mine is a floor model with a single casting from top to bottom that probably weighs 5 times what that bench model weighs, Years ago I had a small Perkins like the one shown, 3 ton capacity.

    I read in old literature the crank journal diameter was used as a good indicator of press tonnage. Sounded like a good way, the problem was another of my punch presses with capacity marked in the casting violated that method. I've had 4 or 5 punch presses over the years and Perkins seems to be the only one that doesn't specify tonnage on the casting.

    Leave a comment:


  • chipmaker4130
    replied
    Yes, that description seems like good stuff. If a good company is willing to put their name on it, that's always a plus. The real trouble often accompanies un-branded/no-name products.

    Leave a comment:


  • Tundra Twin Track
    replied
    Originally posted by chipmaker4130 View Post

    That's something a lot of guys don't realize: The spec for SHCS is much higher than for hex-head bolts, even grade 8. BUT, when you buy chinese, you have no idea whether or not that spec is actually met. Also, since tensile strength is always published and easily found, too many people figure that shear strength will be similar. It is NOT. At best, shear strength comes in around 60-65% of rated tensile.
    Not sure but I think these FKE should be decent as I wouldn’t think Barnes would purchase junk. Click image for larger version

Name:	E0DA5F3B-4F80-438B-B559-BB9D3EFB0114.png
Views:	113
Size:	909.3 KB
ID:	1960655

    Leave a comment:


  • darryl
    replied
    If you're looking to find out what tonnage your press can actually produce, you could look up how to press a bearing ball into a known material and measure the width of the dimple produced. This is dangerous as the ball can shatter, but it's a poor mans way of gauging the force. As for the bolts, being loose they allowed a bending moment to occur, and of course the weak spot would be at the first narrowest part of the bolt- where the threads start. You'd be lucky to have 40% of the tensile strength under that condition.

    Leave a comment:


  • chipmaker4130
    replied
    Originally posted by Tundra Twin Track View Post
    DR I’ve got some FKE 200+ which are 50,000 tensile strength stronger than Grade 8. . .
    That's something a lot of guys don't realize: The spec for SHCS is much higher than for hex-head bolts, even grade 8. BUT, when you buy chinese, you have no idea whether or not that spec is actually met. Also, since tensile strength is always published and easily found, too many people figure that shear strength will be similar. It is NOT. At best, shear strength comes in around 60-65% of rated tensile.

    Leave a comment:


  • Willy
    replied
    Originally posted by MattiJ View Post

    Yet if you factor in the joint friction coefficient you'll find out that ultimately the bolts hold more in shear than just clamping.
    The coefficient of friction being largely the great unknown quantity in an assembly much like this, a well engineered or designed product will allow for the variables inherent in such an assembly and with a large safety factor.
    The bolted assembly's surface finish may be etched, painted, or as supplied by the manufacturer and will play a large part in it's success or failure, as does proper torque and thus clamp load.
    As demonstrated by the OP, fortunately without much drama, clamp load is a very vital key, since shear strength was simply not enough.

    Leave a comment:


  • DrMike
    replied
    Originally posted by DR View Post
    You're absolutely right, if I knew the model number, that is.

    Perkins appears to be long gone. All the searches I've done for pictures of Perkin's presses show a different style than mine. The ones I find have the typical arrangement with the flywheel on the right side, On mine the flywheel is on the back with the crankshaft pointing at the operator. I have found a small bench Perkin's with my style, that bears no tonnage relationship to mine.
    Does yours look like this?
    https://www.youtube.com/watch?v=OWFq...ssetsMachinery

    Leave a comment:


  • MattiJ
    replied
    Originally posted by Willy View Post

    This!!!

    Proper torque will assure the bolts will not be subjected to shear loads in this application.

    There is a tremendous amount of clamp load applied by the leverage the threads on fasteners provide using only a relatively small amount of torque input to a fastener.
    5/8" grade 8 bolts, whether coarse or fine thread will exert in excess of 20,000-23,000 lbs. of clamp load each depending on thread count!
    Makes a huge difference compared to the shear only value.

    I'll include a link to a clamp load chart for various grades and sizes of fasteners as a reference.

    https://sabreindustrial.com/content/...ad%20Chart.pdf
    Yet if you factor in the joint friction coefficient you'll find out that ultimately the bolts hold more in shear than just clamping.

    Leave a comment:


  • Tundra Twin Track
    replied
    DR I’ve got some FKE 200+ which are 50,000 tensile strength stronger than Grade 8 if my info is correct,there Socket Head Cap Screws that I could send you if my stock has your required length.Also have similar in metric there labeled 14.99.

    Leave a comment:


  • Willy
    replied
    Originally posted by The Metal Butcher View Post

    I don't have the time to check the number right now, but I can answer the second.

    Except in specially designed shear bolts, meant to fail, bolts should never be loaded in shear. Instead, the tremendous tensile force they can create holds items together via friction. In a bolted joint say on a beam, zero percent of the load should be handled by the bolt in shear. This is why it is important to torque bolts in such a load case to their specified value.
    This!!!

    Proper torque will assure the bolts will not be subjected to shear loads in this application.

    There is a tremendous amount of clamp load applied by the leverage the threads on fasteners provide using only a relatively small amount of torque input to a fastener.
    5/8" grade 8 bolts, whether coarse or fine thread will exert in excess of 20,000-23,000 lbs. of clamp load each depending on thread count!
    Makes a huge difference compared to the shear only value.

    I'll include a link to a clamp load chart for various grades and sizes of fasteners as a reference.

    https://sabreindustrial.com/content/...ad%20Chart.pdf

    Leave a comment:


  • reggie_obe
    replied
    Originally posted by DR View Post

    You're absolutely right, if I knew the model number, that is.

    Perkins appears to be long gone. All the searches I've done for pictures of Perkin's presses show a different style than mine. The ones I find have the typical arrangement with the flywheel on the right side, On mine the flywheel is on the back with the crankshaft pointing at the operator. I have found a small bench Perkin's with my style, that bears no tonnage relationship to mine.
    Fair enough.
    Perkins Machine, Warren, Mass.?
    Indulge me with a photo or two please? Maybe with something in the images for scale.
    Last edited by reggie_obe; 09-07-2021, 10:45 PM.

    Leave a comment:


  • DR
    replied
    Originally posted by reggie_obe View Post
    Be easier to look up the press specs. Model 200b, 22s, 2a, 20c, ??
    You're absolutely right, if I knew the model number, that is.

    Perkins appears to be long gone. All the searches I've done for pictures of Perkin's presses show a different style than mine. The ones I find have the typical arrangement with the flywheel on the right side, On mine the flywheel is on the back with the crankshaft pointing at the operator. I have found a small bench Perkin's with my style, that bears no tonnage relationship to mine.

    Leave a comment:


  • old mart
    replied
    Sorry, I misread the original post, I take it the USA and Japan use the same number system on their bolts.

    Leave a comment:


  • chipmaker4130
    replied
    Originally posted by old mart View Post
    They wouldn't have broken if they had been done up properly. 8.8 bolts are medium strength, the 10.9 and 12.9 are stronger.
    You're talking 'metric'. A US grade 8 is stronger than a metric 10.9, closer to the 12.9. In any case, as you and others mentioned, the clamping force is critical to proper support for the press.

    Leave a comment:


  • J Tiers
    replied
    What TMB said.........

    Also, if they were loose, the failure was probably some combo loading in between shear and tensile. Plus, odds are they failed in some zipper type failure, not all exactly at once. Nothing was really forcing them to fail at once, so they didn't.

    Leave a comment:

Working...
X