Thread chasing or cleaning for head bolts/studs.

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stumblinhorse

stumblinhorse

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I am going to be installing my newly machined heads (675) in the upcoming long weekend. I am looking for what people are using to thread chase or clean the engine block holes. I really can't find anything other than a regular tap. Also I assume it is 1/2" 14 NPT? Summit has a Thread chasing kit that has a 1/2" 13?

Summit Racing® Thread Cleaning Tap Sets SUM-900200

Thanks!
 
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stumblinhorse said:
I am going to be installing my newly machined heads (675) in the upcoming long weekend. I am looking for what people are using to thread chase or clean the engine block holes. I really can't find anything other than a regular tap. Also I assume it is 1/2" 14 NPT? Summit has a Thread chasing kit that has a 1/2" 13?

Summit Racing® Thread Cleaning Tap Sets SUM-900200

Thanks!
Click to expand...
NPT is tapered pipe thread. Not what you want. Get the summit kit. You don't want to use regular cutting taps either.
 
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correct you want "bottoming"
 
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everyone should have these in their tool box//just measure your head bolts "pitch gauge"
 
A bottoming tap is still a cutter. Problem running a cutting tap through a threaded hole you end up cutting the hole bigger. Standard fasteners work off somewhere around %75 thread engagement. You start reducing that percentage and you might end up pulling the threads or a fastener that doesn't stay torqued. Same with fasteners, higher end and heavy duty fasteners have rolled threads, run a cutting die up it and you've pretty much ruined it. 9 times out of 10 you might be ok on cast iron or steel.
 
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For just cleaning the threads, Take the proper sized bolt and a flat file, use the corner of the file to cut 3 V shaped grooves in the bolt spaced around the circumference. I know it sounds kind of simplistic. Works fine to clean the dirt and smegma out of the threads and it's cheap.
 
I would not use taps. As stated they will take more meet out, and that's not what you want. Thread chasers are what you want. The Summit kit is a basic chaser kit, you might be a size or two shy. Most tool suppliers have much larger sets.

Dave
 
Unconventional said:
For just cleaning the threads, Take the proper sized bolt and a flat file, use the corner of the file to cut 3 V shaped grooves in the bolt spaced around the circumference. I know it sounds kind of simplistic. Works fine to clean the dirt and smegma out of the threads and it's cheap.
Click to expand...
Agree 100%. I also use a squirt bottle with lacquer thinner and compressed air to blow everything out.
 
Run it in a ways, pull it back out. If it has guck in the grooves, wire brush it. Go at it until you get to the bottom. 1/2" nc is 13/inch nf is 20/inch. Oil the bolts before you install for even torque figures. BTW Caterpilar has some oddball 1/2" bolts, a proprietary thing like 16/inch. It's a Cat thing, we could never get a good explanation from them for it :rolleyes:
 
I have heard all the above before. I have also heard many machinists say a thread chaser is just a dull tap and they never use them. Ask the question on a machinist site and see the answers you get. I don’t have the expertise to answer the question, but it is surprising how many machinist I know laugh
At using a thread chaser.
 
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