I am going to be reinforcing my keel with 1/2 Inch X 10 inch stainless steel lag screws that I purchased from Catalina and was hoping to get some advice on the procedure. Anybody have any? Oh, and any idea what drill bit size you would use for a 1/2 inch lag screw? On other projects I never seem to pick the right one and it always causes me problems and since I'll only get one chance to drill it right on this project I'd kind of like to pick the proper size this time. I'd apprciate any help as getting an answer from Catalina didn't work out. I guess they're busy.
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John
Drill Size
According to my Machinery Handbook the minor diameter of a 1/2 lag bolt is .371". You could go with a 3/8" (.375") drill bit, but better yet use a "U" (.368") size drill. The smaller bit gives you a little more bite in the lead. Is there a shoulder on the bolt (no threads). If there is make sure to use a 1/2" drill for a countersink after the smaller bit for the clearance of the shoulder of the lag bolt. Have fun!
According to my Machinery Handbook the minor diameter of a 1/2 lag bolt is .371". You could go with a 3/8" (.375") drill bit, but better yet use a "U" (.368") size drill. The smaller bit gives you a little more bite in the lead. Is there a shoulder on the bolt (no threads). If there is make sure to use a 1/2" drill for a countersink after the smaller bit for the clearance of the shoulder of the lag bolt. Have fun!
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Gerry, Newbury MA.
keel re-inforcement ?
I don't quite understand what you mean by re-inforcing the keel. If you could elaborate a little it would help me to get a clearer picture. Thanks
I don't quite understand what you mean by re-inforcing the keel. If you could elaborate a little it would help me to get a clearer picture. Thanks
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Peter
drill bit size
I've heard from 2 owners that have done this. They recommend 7/16 or even better 15/32, but it's harder to find. Do not use a 1/2 in.Either way, you'll have to back out the bolt every couple of threads because it'll fill up with lead - you're essentially threading the lead with the bolt. You'll likely also want to use a little epoxy or some sealant to seal the threads esp. for the block of wood ontop of the keel. Recommed you be careful with placement of the holes you drill - don't put the holes too close to the outside or you won't get the extension for the socket wrench on the bolt head because of the sole. Hope this helps. Peter
I've heard from 2 owners that have done this. They recommend 7/16 or even better 15/32, but it's harder to find. Do not use a 1/2 in.Either way, you'll have to back out the bolt every couple of threads because it'll fill up with lead - you're essentially threading the lead with the bolt. You'll likely also want to use a little epoxy or some sealant to seal the threads esp. for the block of wood ontop of the keel. Recommed you be careful with placement of the holes you drill - don't put the holes too close to the outside or you won't get the extension for the socket wrench on the bolt head because of the sole. Hope this helps. Peter
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lcm1947
Appreciate the help all!
Hey thanks guys for the information. I really appreciate it. I also want to mention that Catalina did come through for me after all. I just got their answer earlier today and it covered everything I need to know but I sure appreciate your help also. Now I'm ready to tackle it. Thanks again all.
Hey thanks guys for the information. I really appreciate it. I also want to mention that Catalina did come through for me after all. I just got their answer earlier today and it covered everything I need to know but I sure appreciate your help also. Now I'm ready to tackle it. Thanks again all.
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Jack Bollinger
A broken tap will ruin your day
Hello lcm1947, If you are talking about tapping,(threading),the holes for the keel bolts Then with all due respect to John's post, I can say that it is not a good idea to use a "U" drill as a tap drill for 1/2-13NC. I have been a machinist for the last 30 years, of which the last 17 I have been teaching it at the local college, I can say that I nor any other machinist would use a "U" drill as a tap drill for a 1/2-13 NC thread, a "U" drill is not the standard tap drill size and could add to the possibility of a broken tap, which is no fun trying to remove, if you can remove it. If you do be very careful that you don't break off the tap. The standard tap drill size for 1/2-13 NC is a 27/64" drill, which is .412" in diameter. If the thread is a 1/2-20 NF then the recommended tap drill is 29/64, or.4531". You can check out the link I provided, and if you are not sure call Catalina and ask their advice. A quick formula for finding the tap drill size for 60 Degree V thread is : Major Diameter - 1/Number of threads, or Major Diameter - the pitch of the thread (Pitch = 1/Number of threads) If you do a search on google for "tap drill sizes" you will come up with a lot of links. Best of luck, Jack Bollinger
Hello lcm1947, If you are talking about tapping,(threading),the holes for the keel bolts Then with all due respect to John's post, I can say that it is not a good idea to use a "U" drill as a tap drill for 1/2-13NC. I have been a machinist for the last 30 years, of which the last 17 I have been teaching it at the local college, I can say that I nor any other machinist would use a "U" drill as a tap drill for a 1/2-13 NC thread, a "U" drill is not the standard tap drill size and could add to the possibility of a broken tap, which is no fun trying to remove, if you can remove it. If you do be very careful that you don't break off the tap. The standard tap drill size for 1/2-13 NC is a 27/64" drill, which is .412" in diameter. If the thread is a 1/2-20 NF then the recommended tap drill is 29/64, or.4531". You can check out the link I provided, and if you are not sure call Catalina and ask their advice. A quick formula for finding the tap drill size for 60 Degree V thread is : Major Diameter - 1/Number of threads, or Major Diameter - the pitch of the thread (Pitch = 1/Number of threads) If you do a search on google for "tap drill sizes" you will come up with a lot of links. Best of luck, Jack Bollinger
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John
Jack you are correct......except!!!
It is a LAG BOLT and not not a UNF or UNC thread form and you do not TAP the lead keel. Now given all your experience go back and check the drill size you would use for a LAG BOLT. Hint: Machinery's Handbook, 25th Ed, page 1423. Root Diamaeter for a 1/2" ANS Lag Screw is 0.371". I stand by my original post.
It is a LAG BOLT and not not a UNF or UNC thread form and you do not TAP the lead keel. Now given all your experience go back and check the drill size you would use for a LAG BOLT. Hint: Machinery's Handbook, 25th Ed, page 1423. Root Diamaeter for a 1/2" ANS Lag Screw is 0.371". I stand by my original post.
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Ron F.
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Paul Dixon
You may want to haul your boat to do this.
You may want to haul your boat for a couple of reasons. The most important one is to make sure you don't sink your boat. If the hole you drill goes through the side of the keel you will have a bad day if the boat is in the water. Secondly by hauling the boat and blocking the keel you will be able to insure a tight fit between the keel and the keel stub. While the boat is out you can fix the smile which is probably letting water into the space which forms with the crack. When you do put the bolts in angle the holes slightly toward the centerline of the keel this is to account for the shape of the keel. Good luck. Use a good sharp drill bit and it will slice through the lead with no problem.
You may want to haul your boat for a couple of reasons. The most important one is to make sure you don't sink your boat. If the hole you drill goes through the side of the keel you will have a bad day if the boat is in the water. Secondly by hauling the boat and blocking the keel you will be able to insure a tight fit between the keel and the keel stub. While the boat is out you can fix the smile which is probably letting water into the space which forms with the crack. When you do put the bolts in angle the holes slightly toward the centerline of the keel this is to account for the shape of the keel. Good luck. Use a good sharp drill bit and it will slice through the lead with no problem.
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robert taylor
bit size
being a machinist for 10 years prior to mechanical engineer (now 12 years), and sailing for nearly 30 years, i would say we need more information. what is the length of the actual thread engagement. The shorter the thread engagement, the tighter the pilot drill can be. if you have 3 inches of threads, you will never drive it in a 3/8 diameter hole. the last thing you want to do is break the head off during installation. i would agree with the previous post about 7/16. the safe thing to do would be to get some tire weights or lead fishing weights and melt them into a mold. then do the r&d on it and decide for yourself. when putting self tapping screws into any surface, a bar of soap run across the threads is a great lubricant. good luck
being a machinist for 10 years prior to mechanical engineer (now 12 years), and sailing for nearly 30 years, i would say we need more information. what is the length of the actual thread engagement. The shorter the thread engagement, the tighter the pilot drill can be. if you have 3 inches of threads, you will never drive it in a 3/8 diameter hole. the last thing you want to do is break the head off during installation. i would agree with the previous post about 7/16. the safe thing to do would be to get some tire weights or lead fishing weights and melt them into a mold. then do the r&d on it and decide for yourself. when putting self tapping screws into any surface, a bar of soap run across the threads is a great lubricant. good luck
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