Just buy good quality tools as needed. Then, when you have too much money, you can buy the rest of the tools to make complete sets!
Ive been building and machining just about anything my whole life and always got a kick out of threds like this, HOWEVER, I never like sticking my own toe jam encrusted feetuses in my own mouth without being pretty sure of what its gonna taste like. Take some time to read this instead of guessing like you know what youre talking about OK? 4+ pages worth... https://www.practicalmachinist.com/vb/general/thread-chaser-tap-237679/ Any motor build Ive done will usually include take a 1/4" drill bit to loosen any crud in a bottom tapped hole, blow it out with air, chase it with a BOTTOM tap on the cordless drill (they are very low torque BTW) and when done doing EVERY hole in the block, blow them all clean again. After each hole I will take a wire brush and clean the crud off the tap or blow it clean with air. If youre dealing with a fastener of criticallity, like a rod cap or main cap bolts, you are going to replace the bolts and nuts anyway AND use a round wire brush in the receiver right? Then wash and blow dry. If good ol' Hank couldve save 2 cents per block by using one less threaded hole, you know he wouldve done it time 16 million blocks. This after a few dozen overhauls in the last 100 or so years... ws
You don't want to use a different GH number tap to clean threads out than the hole was originally tapped with. Here's a size chart for different GH sizes/ oversizes. G stands for ground, H is the amount of oversize. Use Huggers method and you'll be fine..... H1 = Basic to Plus 0.0005" H2 = Basic Plus 0.0005" to Plus 0.0010" H3 = Basic Plus 0.0010" to Plus 0.0015" H4 = Basic Plus 0.0015" to Plus 0.0020" H5 = Basic Plus 0.0020" to Plus 0.0025" H6 = Basic Plus 0.0025" to Plus 0.0030" H7 = Basic Plus 0.0030" to Plus 0.0035"
So Mart... Im guessing (!) that a standard set of Crapsman or even the stuff that came out of drawers at work were to be an H1? I dont see any reason that to clean out holes in a block would need to be oversize. If a bolt comes out clean and I can thread a STD. tap in 90% by hand (fingers) is that a STD size? I would also guess that the taps should be marked for QC issues. Now Im headed out to the shop and will get some pics of what I have... ws
I could see a tap thats .0030" - 0035" oversized being a little loose on the diameter... that really not all that much for automotive fastening, except on stuff like suspension parts . JMO... ws
I'd guess that most of the stuff that Craftsman sells or that you have laying around would be an H3. I would be surprised if Craftsman sold anything other than an H3. You can't gauge a thread by how far in a standard tap will go. There are thread gauges made for that. They are available in all sizes and classes of fit. https://www.threadcheck.com/thread-plug-gages-taperlock-design-chrome/ I just double checked my taps. Most are H3. The few that I have that are larger than 5/8" are H4. Metrics use a different numbering system. That's a good question. My set isn't marked with an H number. I'd have to get my thread wires and machinist handbook out for a proper answer.
Not sure about any re-threaders, maybe chasers? Roll taps / thread rolls, have no flutes and displace material for a smooth/ strong thread. (Difference between cut and rolled threads). The different GH size's of taps/ threads have to do with the part and assembled products, depending on how much percentage of thread is requested, I imagine for various pull/torque/ stretch values. If it's a non-important (general) application, I wouldn't worry about it too much. That's why Hugger suggested the fluted Allen bolts for thread clean-out purposes.
Mart is right on with the tap sizes. There is also the matter of fastener size. The thread fit tolerance say 1, 2 , or 3 . junk grade 2 hardware probably fits loose because it is smaller with looser tolerance. Something like a rolled thread or cap screw may be a class 2 or 3 fit and fit the hole much tighter. Basically the tap h series are a way to control the class of tapped hole in various materials. I have used h5 or h7 taps to arrive at acceptable size in stainless alloys.
