The other day I had a member call me asking about loctite and such and although everyone has their own way of doing it, I thought it would really be neat to get a guide going as to when to use loctite, what type to use, fine vs. course. thread benefits, wire wheeling the bolts before reinstalling, what you should do to the hole before putting the bolt back in or just on a new install (new part install). Also the importance of proper bolt torque and what tolerances there are (how close to the spec does it need to be..) For instance, the red and blue loctite seem to mix together in applications if you ask me. I was thinking we could get some solid guidelines to which one to use for what application.. Then there is what to do with a bolt that you take out and put back in.. I know some people take it out and put loctite over the old loctite and stick it right back in. Then some people don't use loctite at all. Then there are people who clean the threads up with a wire brush and stick it back in with or without loctite. Then there might even be some people who never reuse old bolts. Then there are custom installations that may need to be tapped, so do you use course or fine thread? I realize the physical differences and strength differences. Fine thread is stronger but then why do we have course thread.. Then we have the bolt, we can use a new one, polish the old one, don't polish it,..but what about the hole? Is it necessary to run a tap down it to clean out any other residue? Then we have bolt torque...I know a lot of people say to overtighten things so they don't loosen or slip in the case of my timing gear which is timed and held there by just the pressure of the nut, no keyway. So is there some % tolerance for the torque values? I will be definitely turning this into an article.. My personal input is to wire wheel the old bolts, put loctite on them, and reruse them. I don't touch the hole unless the screw has issues going in which then I run a tap through it. I don't see any reason for course threads other than how quickly you can unscrew them. The proper bolt torque tolerance is unknown to me. Those are my rough thoughts. I'd really like to get in depth on this with you guys. If there are alternatives to what I just said, alternatives to loctite, by all means share your thoughts.

I could be wrong, but Ive always thought that the main factor in the strength of a bolt (other than size) was the depth and pitch of the threads. If thats the case, I think a courser thread would be stronger. Take a look at a drill and tap chart, for example. You can look at any given size bolt and the recomended drill size will always be smaller for a courser thread than a finer thread. My reasoning is the smaller the hole drilled, the more "meat" the bolt will have to grab once threaded in. Just my thoughts...As far as loctite I very rarely use loctite except on critical parts such as flywheel bolts or where vibration or rotation may cause loosening. I live in the heart of the rustbelt so for me I wirewheel the bolt and am very liberal with anti sieze.Ok this kind of peaked my interest so Ive been looking at some sites online you are right ISX the fine threasdoes have a higher strength than the course. I find this rather interesting because you just dont see fine threaded bolts in nearly as many aplications as course thread. I was only going by my experiences where I work we deal with large bolts like 1 and 1/4 dia and up and torque values well up over 1000 lbs in certain applications. The majority of what we use are studs not bolts. And all are course thread, grade 8, something like 13 tpi. We work in an enviremont that is very corrosive and in some applications the studs/bolts see constant temps over 500 degrees. One example is the outlet piping coming out of the top of our reactors the exit temp of the offgas exceeds 1800 degrees. Now all this pipe is refractory lined so the steel temp may only be around 400 to 500 degrees. If they are properly antisiezed, they will usually come right out. If theyve been put together dry, youd swear they were welded together after youve rattled your teeth out with a 1" impact hooked to 150 psi of nitrogen! Ok, Im starting to wander off track, just wanted to correct myself.

The other day I had a member call me asking about loctite and such and although everyone has their own way of doing it, I thought it would really be neat to get a guide going as to when to use loctite, what type to use, fine vs. course. thread benefits, wire wheeling the bolts before reinstalling, what you should do to the hole before putting the bolt back in or just on a new install (new part install). Also the importance of proper bolt torque and what tolerances there are (how close to the spec does it need to be..) For instance, the red and blue loctite seem to mix together in applications if you ask me. I was thinking we could get some solid guidelines to which one to use for what application.. Then there is what to do with a bolt that you take out and put back in.. I know some people take it out and put loctite over the old loctite and stick it right back in. Then some people don't use loctite at all. Then there are people who clean the threads up with a wire brush and stick it back in with or without loctite. Then there might even be some people who never reuse old bolts. Then there are custom installations that may need to be tapped, so do you use course or fine thread? I realize the physical differences and strength differences. Fine thread is stronger but then why do we have course thread.. Then we have the bolt, we can use a new one, polish the old one, don't polish it,..but what about the hole? Is it necessary to run a tap down it to clean out any other residue? Then we have bolt torque...I know a lot of people say to overtighten things so they don't loosen or slip in the case of my timing gear which is timed and held there by just the pressure of the nut, no keyway. So is there some % tolerance for the torque values? I will be definitely turning this into an article.. My personal input is to wire wheel the old bolts, put loctite on them, and reruse them. I don't touch the hole unless the screw has issues going in which then I run a tap through it. I don't see any reason for course threads other than how quickly you can unscrew them. The proper bolt torque tolerance is unknown to me. Those are my rough thoughts. I'd really like to get in depth on this with you guys. If there are alternatives to what I just said, alternatives to loctite, by all means share your thoughts.

The only time I ever consider using loctite is if its a critical component. Something such as the timing cover where if the bolts came loose, I could loose my crank oil and it could cause the engine to seize. If something puts pressure against a bolt as I tighten it, such as the valve cover, I would not loctite it. If an area sees alot of potential corrosion, I would anti seize the bolt instead of loctite it. As for any of the other questions, IMO, a bolt and its respective hole should always be clean. Whatever it takes to make it clean. Wire wheel and a tap works good to do the job. If you have an air compressor, use an air nozzle to blow the hole out. The only time I would never re-use an old bolt is if the threads were no good and could not be fixed with a die, or if it was used in an application where it was torqued so much that the bolt was stretched. Use of the proper grade bolt is also important. Majority of bolts used on a vehicle is grade 8. If you use a bolt that meets or exceeds this, then there should never be problem, so long as its never been overtorqued. As for torque, torquing of a bolt or nut is not assigned because of the application per se. Its the amount of torque that the said nut or bolt can take before it will stip or break. My advice is to ALWAYS torque a nut or bolt to its EXACT value. Never any looser or tighter. Any looser, you risk it backing off and not fulfilling its purpose. Any tighter and you risk it breaking or stripping. There is a whole world out there dedicated to the science of proper bolt/nut application. Google would work good in finding out...

Well you guys showed me something in a different light So now I am left with some more specific questions. Red vs. Blue, when and where to use it... You guys explained when and where to use loctite, but not the type. Is there a "real" difference between the 2? Then you mentioned antiseize which I thank you for. You say to use it where stuff might rust but what other factors call for it? Oh and the part about not using loctite on bolts with a load on it like the valve covers..I was under the assumption all bolts had loads on them so could you clarify this a bit? You guys are doing a great job so far, details beyond what I was expecting haha.

Something to add while I was digging around Loctite site. Any of the loctite colors (Red, blue, green) are all thread protectant from the elements like rusting and corrosion too.

Loctite® Threadlocker Blue 242® is designed for the locking and sealing of threaded fasteners which require normal disassembly with standard hand tools. The product cures when confined in the absence of air between close fitting metal surfaces. It protects threads from rust and corrosion and prevents loosening from shock and vibration. Loctite® Threadlocker Blue 242® is particularly suited for applications on less active substrates such as stainless steel and plated surfaces, where disassembly is required for servicing.

So thinking of the Anti-Seize vs. Loctite they both are going to protect the threads from corrosion and rust. But one is going to lock the fastener together to prevent vibration from loosen then fastener when anti-seize might not work well in a vibration application.

I saw that too, was thinking antiseize must be a lot better at hindering the rust. Hex0rz, explain haha

Something to add while I was digging around Loctite site. Any of the loctite colors (Red, blue, green) are all thread protectant from the elements like rusting and corrosion too. So thinking of the Anti-Seize vs. Loctite they both are going to protect the threads from corrosion and rust. But one is going to lock the fastener together to prevent vibration from loosen then fastener when anti-seize might not work well in a vibration application.

Us rustbelters can pretty well blow the whole loctite/anti corrosion claim out of the water that may be true in an everyday environment but where they use calcium chloride (aka super salt) nothing short of a quality nickel or copper grade anti sieze will do the trick. Antisieze is also excellent for bolts in high heat applications. At work when we have to thread stainless pipe, we will also use it as a lubricant for the threads. Stainless will gall very easily. A few wraps of teflon tape, followed by some antisieze and you can bury the threads to proper depth with little effort.. works much better than pipe dope as far as lubrication goes. Another benefit...comes apart much easier inthe event the line needs to be pulled apart again... lots and lots of uses for antisieze...

I'm no exception to the rule I'm in the frozen northern states too with lots of salt, mag-cloride, and other road chemicals too. Yes I'll tend to agree I tend to grab the ol' Anti-seize bottle more than the tbe of Loctite.

this has been a most interesting read.

ISX, just wait til you get to Machine Design. It should be after or concurrent with Engineering Dynamics. You will love it, especially if the prof is good.