March 15, 201115 yr What does 4 X dia mean? I understand that a 1/2" bolt will have deeper threads than a 1/4" bolt. Is that what it's related to? If the bolt is 1/2 inch diameter, then you need 2 inches of threads engaged into good iron to get a "full strength" joint. "Full strength" being the pressure the bolt is capable of making when properly torqued. (but I don't know the proper torque) Phil
March 16, 201115 yr Author If the bolt is 1/2 inch diameter, then you need 2 inches of threads engaged into good iron to get a "full strength" joint. "Full strength" being the pressure the bolt is capable of making when properly torqued. (but I don't know the proper torque) Phil Thanks Phil. So that's why Grant recommended a 2 3/4" depth with presumably a 2 1/2" bolt. Cool. I found this article which explains the torque required.Zerofast torque I guess a grade 5 1/2"x20 socket head cap screw should work well.
March 16, 201115 yr Thanks Phil. So that's why Grant recommended a 2 3/4" depth with presumably a 2 1/2" bolt. Cool. I found this article which explains the torque required.Zerofast torque I guess a grade 5 1/2"x20 socket head cap screw should work well. I think a grade 5, 1/2" 13thread would be better.IMO 20thrd is a fine thread bolt.
March 16, 201115 yr I would expect that it doesn't matter much which way you go, and would determine the choice on the easier sourced bolt. The shank of the bolt is going to be similar in size so the pressure generated by the torque will be the same. Course threads require lower torque to generate the same pressure as fine threads. In both cases (fine or course) you are looking at a number below or about 100 ft-lb which is a pretty reasonable value with common tools (my torque wrench goes to 150 ft-lbs). That is a helpful article and chart. Phil
March 16, 201115 yr I agree with the bolts being the same strength, I was thinking in the tapping of the hole being easier and less apt to "pull" the threads while tapping for the fine thread, especially in cast iron...but then I'm no machinist either! :P
March 16, 201115 yr I agree with the bolts being the same strength, I was thinking in the tapping of the hole being easier and less apt to "pull" the threads while tapping for the fine thread, especially in cast iron... If the body is cast iron, coarse threads are recommended
March 16, 201115 yr If the body is cast iron, coarse threads are recommended I agree, coarse threads for cast iron.
March 16, 201115 yr I did a successful repair on a similar type of crack using pins. The holes were drilled and the pins were turned to the exact same size + - .001. Its best to leave the pins a few inches long and cut them off later. A few drops of loctite and drive em in (No stopping) I didn't do it but freezing the pins would be a good idea. I had the advantage of being able to use a mag drill on a flat surface once the sow block had been removed. The holes in the LG will need hand drilling I expect. Kinda tricky. Anyway the crack never spread after that.............mb
March 16, 201115 yr I would expect that it doesn't matter much which way you go, and would determine the choice on the easier sourced bolt. The shank of the bolt is going to be similar in size so the pressure generated by the torque will be the same. Course threads require lower torque to generate the same pressure as fine threads. In both cases (fine or course) you are looking at a number below or about 100 ft-lb which is a pretty reasonable value with common tools (my torque wrench goes to 150 ft-lbs). That is a helpful article and chart. Phil Sorry Phil, I think you got backward, in fact I'm sure. But at any rate, you should use course threads in cast iron. I like bolts in this case to pull the the crack together.
March 16, 201115 yr Sorry Phil, I think you got backward, in fact I'm sure. But at any rate, you should use course threads in cast iron. I like bolts in this case to pull the the crack together. I based my torque statement on the linked article. I defer thread and bolt selection to people who know more than I do. Phil
March 16, 201115 yr You're reading it wrong. A thread is an "inclined plane" wrapped around a cylinder. A wedge is also an "inclined plane". A fine thread is like a slim wedge. In both cases they can exert more force in relation to the applied force than a coarse thread or a steeper wedge. A fine thread can also exert more force because the root diameter of the thread is larger.
March 17, 201115 yr Author You're reading it wrong. A thread is an "inclined plane" wrapped around a cylinder. A wedge is also an "inclined plane". A fine thread is like a slim wedge. In both cases they can exert more force in relation to the applied force than a coarse thread or a steeper wedge. A fine thread can also exert more force because the root diameter of the thread is larger. Ok, sounds like the consensus is 1/2"x21/2"x13 socket head cap screw. Actually, when I get the ramguide and possibly the ram out of the way, I'm going to try move a drill press over the site to improve the precision.
March 17, 201115 yr You're reading it wrong. A thread is an "inclined plane" wrapped around a cylinder. A wedge is also an "inclined plane". A fine thread is like a slim wedge. In both cases they can exert more force in relation to the applied force than a coarse thread or a steeper wedge. A fine thread can also exert more force because the root diameter of the thread is larger. Dangit. Now I gotta go find my textbook that has the formula on this stuff. Did you look at the chart in the article at least? Phil
March 17, 201115 yr Dangit. Now I gotta go find my textbook that has the formula on this stuff. Did you look at the chart in the article at least? Phil Yeah, I did before I commented and I don't see what you're referencing.
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