Thread Chaser or Tap?

[R_W_B]

Dave, Most Felpro gasket sets IE Head gasket kits come with new head bolts now, these are torque to yield bolts and should not be re used, If this is a chevy 4.3 motor do not take any chances

No it's a 350ci (5.7L) TBI, small block w/ cast iron heads. Those heads nearly killed my old back lifting them out of the engine bay. They only weigh about 50lbs but bending over pulling them off sticky gaskets is like a lead weight.

I did not order a gasket set since my machine shop will be suppling the valve seals. I don't think mine are "torque to yield bolts" since none of my manuals stated such. I did buy the Fel-Pro Permatorque head gaskets which only require one torque at install, but do recommend new head bolts used. I also bought the Fel-Pro set of Head Bolts so I'm covered if they are "torque to yield bolts" since Fel-Pro advertises that they match OEM specs including "torque to yield.

Of course old timers like you and me remember Fel-Pro under the old name of Federal Mogul. I like their stuff, always had good luck with um.

 

[ckphir0]

It is simple, tap/die sets have a different pitch diameter than chaser sets. It is really important to use chasers for cleaning threads or you will end up with loose threads. One person posted that you could use a tap if you didn't take it in too far, and they may be correct but it is my experience that I tend to mess up when I go on a maybe. As another poster stated that you need to be very carefull even with a chaser to follow all correct proceedures or you will get very bad results.
Best of luck to you and have a Merry Christmas.

 

[R_W_B]

It is simple, tap/die sets have a different pitch diameter than chaser sets. It is really important to use chasers for cleaning threads or you will end up with loose threads. One person posted that you could use a tap if you didn't take it in too far, and they may be correct but it is my experience that I tend to mess up when I go on a maybe. As another poster stated that you need to be very carefull even with a chaser to follow all correct proceedures or you will get very bad results.
Best of luck to you and have a Merry Christmas.

One thing for sure this subject has a never ending supply of different opinions. I showed the Machinist forum guys a pic of a "Thread Chaser" and they said those are what's called "Form Taps" and/or "Form Dies". I asked them what that was and they said they are used for cutting threads in soft or gummy materials like very soft metals or hard polymer materials. I do know for sure the bolts I did today with just an ordinary cheap set of dies (not chasers) produced no ill results or metal loss. I will try the tap holes tomorrow.

Here is another interesting Machinist post.
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Take the money you'd spend on a chaser set and get you a case of beer and put the rest back in your pocket. Use the taps!!

FYI- I have spent the last 20 years as a machinist with equal parts being new and refurb work. From aerospace to mining support to tool & die to fab work. Parts ranging from a few ounces to 80 tons.
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[R_W_B]

You know many years ago when I worked as a framing carpenter in construction. As the job came to a close we all had to leave and hunt elsewhere for a new project. After I had worked on several different crews ran by different formen is when I realized I had collected different technics from all of them that I could pick the best most functional ones to combine for a most efficient job. This helped me a great deal when I ran my own framing crew years later.

The whole truth is a great accept, but not always prevalent without some searching and exposure. So I want share this recent post from a machinist on another forum that is very complete in the whole subject giving some deep concepts into the matter.

[--
"Most" everyday applications can be cleaned up using a standard tap and die set, which many times can be bought in carbon steel grade cheaper than they sell Chaser kits (Form taps).

However you don't need to buy anything to have a perfectly safe thread cleaner. If you have the bolt or know it's size and TPI, just buy one bolt for each size you need. Then cut slots perpendicular to the threads (lengthways) with a thin ginder or cutter. The slots will allow the rust and buildup a place to collect out of the thread and give it a place to go as you turn. They also form a dull cutting edge. The die version can be made of a nut however the slots can be a challenge if you don't have a milling machine or a good holding drill press setup. If you are frugal make the size you need yourself. You still need to practive proper technics in 2 turns forward and 1 turn back, plenty of oil, and an air blow to rid of excess buildup of removal material.

However to be complete I would be very careful if your chasing a thread with a standard tape or die in something critical because you don't know what size tap was used by the factory. What I mean isn't the actual thread size but the taps tolerance 2B 3B etc. Or if they used a form tap and the tolerance for that. It's "possible" that you may remove some material and the thread will be a small tolerance factor looser. Always examine what the process is doing before you go to far.

But with the bolt method you are covered in all areas (purchase price and tolerance safety). The only drawback to using the bolt tool (or a chaser) is that sometimes it will not clean "all" the residue buildup which in some critical applications can affect torque parameters. But usually these issues are only important in high tolerance applications, but just pay attention and look as you go. For most stuff, no worries.
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