Fastener tech
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==Fastener grades== | ==Fastener grades== | ||
Fasteners are graded according to their properties. The following article will help the grading system to be better understood. | Fasteners are graded according to their properties. The following article will help the grading system to be better understood. | ||
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[[File:Snap7.jpg|none|Left]] | [[File:Snap7.jpg|none|Left]] | ||
| − | + | ==Metric nut grading== | |
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The grade system for a metric nut is a number that represents 10% of the specified metric proof load stress in kgf/mm². The proof load stress corresponds to the minimum tensile strength of the highest grade bolt that can be used with that nut. | The grade system for a metric nut is a number that represents 10% of the specified metric proof load stress in kgf/mm². The proof load stress corresponds to the minimum tensile strength of the highest grade bolt that can be used with that nut. | ||
| − | ==Caution on grading== | + | ===Caution on grading=== |
While it is common practice for a grade 5 bolt to have three slash marks and for a grade 8 bolt to have six slash marks for identification purposes, it should be noted that not all grade 5 or grade 8 bolts will have ID marks. | While it is common practice for a grade 5 bolt to have three slash marks and for a grade 8 bolt to have six slash marks for identification purposes, it should be noted that not all grade 5 or grade 8 bolts will have ID marks. | ||
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OEM bolts may not have any ID markings at all, or may have a unique symbol. If doing a restoration, it’s best to use OEM bolts in places where ID markings are important. | OEM bolts may not have any ID markings at all, or may have a unique symbol. If doing a restoration, it’s best to use OEM bolts in places where ID markings are important. | ||
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| − | [[File:Bolt head grade marking.jpg]] | + | |[[File:Bolt head grade marking.jpg]] |
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| − | [[File:Gr 8.2 and encap head bolts.jpg | + | |[[File:Gr 8.2 and encap head bolts.jpg|thumb|380px|Grade #8.2 bolts w/JS-500™ rust resistant coating and rust-proof polypropylene-encapsulated head.]] |
| − | Grade #8.2 bolts w/JS-500™ rust resistant coating and rust-proof polypropylene-encapsulated head. | + | |} |
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==Cleaning threads== | ==Cleaning threads== | ||
To get the correct torque on a fastener, the threads need to be clean. This can be done using a wire brush after the grease and grime is completely removed. Using a vise to hold the bolt will make this easier. A wire wheel is a much faster method, and gives superior results. | To get the correct torque on a fastener, the threads need to be clean. This can be done using a wire brush after the grease and grime is completely removed. Using a vise to hold the bolt will make this easier. A wire wheel is a much faster method, and gives superior results. | ||
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But whatever method is used, the bolt has to be free of dirt, grease, and rust. The metal should be spotless, but without removing any material. | But whatever method is used, the bolt has to be free of dirt, grease, and rust. The metal should be spotless, but without removing any material. | ||
| − | Below are tools that clean external threads | + | Below are tools that clean internal and external threads when no other means are available: |
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|[[File:Otc-7402 wOD chaser.jpg|thumb|350px|External thread chaser. Costly tool but worth it if there's no access to a wire wheel.]] | |[[File:Otc-7402 wOD chaser.jpg|thumb|350px|External thread chaser. Costly tool but worth it if there's no access to a wire wheel.]] | ||
|[[File:KRC-8221od cheap.jpg|thumb|235px|right|Less costly set of external thread cleaners]] | |[[File:KRC-8221od cheap.jpg|thumb|235px|right|Less costly set of external thread cleaners]] | ||
| + | |[[File:Arp-911-0006chaser.jpg|thumb|250px|ARP thread chaser set. Look like taps, but these do not remove any metal like a tap would.]] | ||
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| − | For cleaning internal threads like threaded holes or nuts, a thread chaser is used. This is not the same as a tap; chasers remove no metal. | + | For cleaning internal threads like threaded holes or nuts, a thread chaser is used. This is not the same as a tap; chasers remove no metal. The chasers shown above look like taps- but they're not. |
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Chasers can be bought as a set or individually. Sears calls their tools a Master Rethreader Tap and Die Set, just be sure it's not a regular tap and die set.In a pinch, a bolt having the correct thread can be made into a thread chaser. A section is ground away lengthwise, this gives the debris a place to go. A nut can be used in the same way to clean up bolts or studs. | Chasers can be bought as a set or individually. Sears calls their tools a Master Rethreader Tap and Die Set, just be sure it's not a regular tap and die set.In a pinch, a bolt having the correct thread can be made into a thread chaser. A section is ground away lengthwise, this gives the debris a place to go. A nut can be used in the same way to clean up bolts or studs. | ||
| − | ==Cutting threads== | + | ==Cutting new threads== |
*When threading a blind hole, the best way to clean out the chips is to use a ball inflater needle in a blow gun. You can make an adapter using a 1/8-NPT fitting (which is a close thread to a blow gun nozzle) to adapt the inflater to it. | *When threading a blind hole, the best way to clean out the chips is to use a ball inflater needle in a blow gun. You can make an adapter using a 1/8-NPT fitting (which is a close thread to a blow gun nozzle) to adapt the inflater to it. | ||
*To keep chips from falling into an engine when rethreading a spark plug hole, put axle/bearing grease on the tap. This will collect most if not all the metal chips from falling into the engine. | *To keep chips from falling into an engine when rethreading a spark plug hole, put axle/bearing grease on the tap. This will collect most if not all the metal chips from falling into the engine. | ||
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*Make sure all threads are clean and is the right fastener for the part. Right thread pitch, length and diameter. | *Make sure all threads are clean and is the right fastener for the part. Right thread pitch, length and diameter. | ||
*Lubricate the threads with a suitable lubricant, if necessary. | *Lubricate the threads with a suitable lubricant, if necessary. | ||
| − | *Consult the manufacturer's fastener tightening chart whenever possible (all threaded fasteners have different torque values based on fastener grade, size, thread pitch, material and if lubed, and with what type lubricant, or if installed/tightened | + | *Consult the manufacturer's fastener tightening chart whenever possible (all threaded fasteners have different torque values based on fastener grade, size, thread pitch, material and if lubed, and with what type lubricant, or if installed/tightened dry). |
| − | *Bolts of different sizes are torqued | + | *Bolts of different sizes are torqued differently. Smaller diameter bolts are generally torqued in one step. Larger bolts are generally torqued in at least three stages. 1/3 of the torque spec, 2/3 of the torque, then full torque. For example, if cylinder head bolts are supposed to be torqued to 90 foot-lbs, then they would be torqued first to 30, then to 60, and finally to 90 ft/lb. |
| − | * | + | *Should you want or need to re-torque a fastener, you must first loosen it, then completely torque it. |
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| − | Should you re-torque a fastener, you must first loosen it, then completely torque it. | + | |
==Lubricants and sealants== | ==Lubricants and sealants== | ||
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