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    Default Tap question(s):

    So, getting ready to build a little machine (a 2x72 grinder) in 3/8" steel. Of course, I'll need to tap a few holes here and there. Like usual, I don't just go buy a generic whatever tool and and go at it, I want to "understand" more about the process, etc, etc. So...I did a lot of reading on taps and dies and the entire process which leads me to some questions, perhaps more for my own education than any real need for consideration in this project.

    So, first question, when buying a tap (I am looking on industrial supply houses in order to buy a good quality HSS American made tap, I don't want no chinesium junk), I am looking at the H and L designators. Am I correct to understand that, say an H5 tap will provide a "looser" fit for any given bolt, whereas an H3 will be a little tighter? L speced taps are just going to make the threads undersized and even tighter to the point of not fitting. Also, 2B vs 3B, I'm guessing the majority of the grade 8 bolts available are probably not going to be toleranced to 3B specs.

    Anyway, I guess my real question is, if you were buying a tap to make threads for generic grade 8 3/8" and 1/2" bolts, would you choose an H3 or an H5 tap?

    Any particular brand of tap to recommend? I was planning on a taper tap since all holes on this machine are through holes, but I see they have spiral and spiral tip. Are these worth the extra cost for hand tapping operations? I plan to use my drill press to do the tapping (manually, not under power) just to keep things lined up. What about forming taps? Is a 3/8" form tap too difficult to do by hand power in A36 mild steel?

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    Quote Originally Posted by Hydroracer View Post

    Any particular brand of tap to recommend? I was planning on a taper tap since all holes on this machine are through holes, but I see they have spiral and spiral tip. Are these worth the extra cost for hand tapping operations? I plan to use my drill press to do the tapping (manually, not under power) just to keep things lined up. What about forming taps? Is a 3/8" form tap too difficult to do by hand power in A36 mild steel?
    You're not ready for form taps yet.
    Brand? Hertel, Accupro, Morse will suffice.
    Get a SPIRAL POINT H3 tap.Not Spiral flute.
    Do not get Uncoated/Bright... at the very least get steam oxide coating.

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    Hydroracer --

    I'm in a bit of a time pinch, can only give you a quick answer at the moment:

    1. H and L numbers on a tap identify the deliberate oversizing or undersizing of the tap diameter (H for oversize, L for undersize), in units of 0.0005 inch. So, an H3 tap would have a 0.0015 inch larger diameter than the theoretical external thread of the same size, an H5 tap would have a 0.0025 inch larger diameter. Either one would probably work fine for you, but I'd lean to the smaller size generally.

    2. My suggestions for the drilling and tapping itself are simple:

    Drill your holes using a drill press or, if necessary to use a hand-held drill motor, use a "drill block" guide.

    Use a spiral-point tap, using either the drill press as a guide, or use a "tap block" guide.

    Use a T-handle tap wrench to drive the tap, not a Crescent-type adjustable or mechanic's open-end wrench, to drive the tap.

    Spiral-point taps are designed to cut continuous chips in tight curls that flow down into the hole being tapped; they do not need the half-turn-forward-and-quarter-turn-back shuffle that old fashion taper / hand taps need. Wind a spiral-point tap straight into its hole, and wind it back out again.

    3. I have a warm spot in my heart for Reif & Nestor taps, but Norseman, Triumph, and Viking are also good . . . as are many others.

    John

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    Out of curiosity, what's wrong with the "brite finish" taps?

    What is it about form taps that I'm not ready for? I understand the premise of operation, was just curious if the forces needed are significant enough to render them solely to power tapping? I wasn't looking to go that route, just looking for more understanding is all.

    Looking around, I found this one as described below for $22.87. Made by "Cleveland", is that decent brand? It is H3 and TiCN coated (and from my reading, this coating has a lower coefficient of friction and is harder than TiN). I'm finding the majority of spiral point taps are either bottoming or plug only, no tapers, which I guess is fine since I'm using my drill press as a manual tapping machine.

    3/8-16 2B 3 Flute TiCN Finish High Speed Steel Spiral Point Tap
    Plug Chamfer, Right Hand Thread, 3/4" Thread Length, H3, Series 1011TICN

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    Quote Originally Posted by Hydroracer View Post
    Out of curiosity, what's wrong with the "brite finish" taps?

    What is it about form taps that I'm not ready for? I understand the premise of operation, was just curious if the forces needed are significant enough to render them solely to power tapping?

    Looking around, I found this (description). Made by "Kennametal", is that decent brand? Seems any of the spiral point ones I find are all 3B (no 2B), but it is H3 and TiCN coated (and from my reading, this is supposed to be one of the better coatings, or at least a step up from the Ti Nitride coating. Seems all the spiral points I'm finding are also plug taps and not tapers, which I guess is fine since I'm using my drill press as a manual tapping machine.

    3/8-16 UNC 3B 3 Flute TiCN Finish High Speed Steel Spiral Point Tap
    Plug Chamfer, Right Hand Thread, 2.94" OAL, 1-1/4" Thread Length, 0.381" Shank Diam, H3, Series 5301S
    Brite finish taps are generally not for steels, they are better for aluminum, plastics, etc..
    I say you're not ready for form taps because it appears you're new to tapping. Form taps require a little experience and a different hole size that MUST be maintained for them to give you a good thread and not bust.
    Kennametal, Sandvik, Iscar, OSG are all good big name brands they are more expensive though.With OSG generally being the most inexpensive of them all.
    TiN, TiALN, TiCN are all good coatings for steel, TiN is the oldest technology but still viable.

    2B and 3B are classes of fit, meaning they have a specific tolerance of minor diameter and pitch diameter.
    You want a plug tap, Taper taps have a massive lead on them and I wouldn't use them unless you're tapping un-guided by hand.

    This one here is $10 on MSC, and it's OSG.
    https://www.mscdirect.com/product/details/04620134

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    Quote Originally Posted by Mtndew View Post
    This one here is $10 on MSC, and it's OSG.
    https://www.mscdirect.com/product/details/04620134
    Buy this one ^^^^^^.

    That's what we use for hand tapping through holes and they work great.



    [tangent] BTW, can someone explain why we have both B limits and H/L limits? Why have two standards? [/tangent]

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    I understand the science behind form taps, meaning I get why the hole has to be slightly larger than you would drill for cut threads (because the metal "moves" when the form tap goes in and comes back out due to the metal's "memory"). Also, alignment of the tap to the hole is critical, otherwise you will bust the tap.

    Still, I have the question, can 3/8" form taps be done manually, or do they require powered machinery?

    As for why we have thread classes and limits, my understanding is that for class 2 threads there is an allowance and a tolerance, whereas class 3 threads have tolerance but no allowance (Class 1 is not used much, but my reading indicates there is a use for it). In other words, class 3 threads have to be created more precisely (which is why they are also more expensive). Limits are available to allow you to adjust the fit, so to speak to account for variances in manufacturing, or other metalurgical based differences or changes to the measurements. If you look at internal threads and external threads, there is a "basic" major diameter, basic pitch diameter, and basic minor diameter. This is the baseline "target" that an absolutely perfect thread should be for any given size. Unfortunately, as good as machining is today, it is still impossible to make every thread exact, so allowances and tolerances exist.

    Anyway, that's my current take on it from reading, pros please correct me if I'm wrong...I'm still learning.

    I like the saying "if you can't make it perfect, at least make it adjustable" and having various limits available gives us that adjustability.

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    Quote Originally Posted by ChipSplitter View Post
    Buy this one ^^^^^^.

    That's what we use for hand tapping through holes and they work great.
    I don't have any experience with oxide coatings on tools, but I do with firearms and it's been my experience they don't last long. I'm not against this for the tap at all, but just wondering how it compares to my experience.

    So your saying the AlTiN coated one isn't worth twice the price? $10 is pretty cheap, heck I even thought $20 was pretty good considering what I've seen on prices for some of them. At $10, I'll buy 2 or 3 just in case I bust one.

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    Quote Originally Posted by Hydroracer View Post
    So your saying the AlTiN coated one isn't worth twice the price?
    Not for a hand tap, IME.

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    Default Hand tap info

    Here's a link to the full OSG catalog. Check out the technical info section for taps. It should give you a good overview. Also is a link to Greenfield Taps.


    https://www.osgtool.com/books/800201...002018CA__.pdf

    GFI | Technical


    Suggest the spiral point tap as others have suggested. Just pay attention to drill size for associated tap. Depending on size, standard H-limits will be little bit different for a standard tap. You need to go to bigger H-limits if part is going to be plated.

    If hand tapping, use a decent oil or tapping fluid (Tap Magic). There are different lubricants depending on material to be cut.

    I wouldn't go with a form tap if hand tapping. Our firm used to form a 1/4-28 tapped thread on multi-spindle screw machine in 316 stainless using OSG form taps with TiCN coating. Made 1,000 pcs. per day for 22 years. Taps worked great with long tool life. We used a high sulfur oil when cutting 316 stainless.

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    Parts are A36 steel 3/8" thick. There are only a few tapped holes in the entire machine mainly for locking handles. Most will be either welded or through bolted with lock nuts. Using grade 8 bolts, not sure if those will be plated or not, depends on what I can find locally. If they are, then most likely zinc.

    If you're curious, this is what I'm building:

    YouTube

    There are a few changes I'll make, mainly because my OCD is kicking hard on some of the design aspects, and although they'll likely make zero difference because the thing is so over built to begin with, if I don't do them, then my OCD will forever torment me :-)

    Mainly, the hinge points, he uses two prongs on each piece, so one is double shear and the other is only single shear. I'm adding a third prong so both of the prongs on the other piece are double shear hung. I'm also replacing the two bolts for the hinge points with shoulder bolts just because I think look and work nicer for hinging purposes.

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    I noticed that only one reply mentioned a good tapping fluid. So I will second that. Do, DO, DO use a good tapping fluid. I also like Tapmagic, but there are others.

    As for your question about using a 3/8" form tap by hand, I say it can work. I would want a larger than normal tap wrench. If you are tapping by hand, it is important to use a proper tap wrench. It is important to keep the torque balanced on both of the two arms of a tap wrench. If you try to use just one arm, you are ask, no begging for a broken tap. Always keep the two arms the same length and use both of them equally while turning the tap. You say you are going to use the drill press for guidance. That is a good idea and I do it all the time. I have two tap wrenches that are made for this. They have an extended pin on the top of the wrench which fits into a socket that is held in the drill press's chuck. Here is one like one of mine. McMaster calls them machine mount wrenches.

    McMaster-Carr

    My other one is shop made with a longer pin and a couple of sockets with different lengths so I can use it without repositioning the drill press table after taking the tap drill out of the chuck. I altered a commercial tap wrench by adding the guide pin. I like it a lot better than the store bought one.

    PS: I also like the spiral point taps for through holes. But others are better for blind holes because you don't want to push the chips into the hole unless you have enough depth past the threads to hold them. The taper, plug, bottoming sets are good for them, but it is back and forth and in and out to control the chips. Also the spiral flute taps, which push the chips backwards up the hole are good for blind holes but they can break more easily. I would not use them for a difficult material like harder steels and suggest that you stay away from them for a while until you have more experience.



    Quote Originally Posted by flubber View Post
    Here's a link to the full OSG catalog. Check out the technical info section for taps. It should give you a good overview. Also is a link to Greenfield Taps.


    https://www.osgtool.com/books/800201...002018CA__.pdf

    GFI | Technical


    Suggest the spiral point tap as others have suggested. Just pay attention to drill size for associated tap. Depending on size, standard H-limits will be little bit different for a standard tap. You need to go to bigger H-limits if part is going to be plated.

    If hand tapping, use a decent oil or tapping fluid (Tap Magic). There are different lubricants depending on material to be cut.

    I wouldn't go with a form tap if hand tapping. Our firm used to form a 1/4-28 tapped thread on multi-spindle screw machine in 316 stainless using OSG form taps with TiCN coating. Made 1,000 pcs. per day for 22 years. Taps worked great with long tool life. We used a high sulfur oil when cutting 316 stainless.

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    Here is an excellent video Haas did on different styles of taps.
    YouTube

    I use a spring loaded tap guide for guided hand tapping, these allow you to guide the tap several turns before readjusting.
    https://www.mscdirect.com/product/details/95267472

    As others have said, even pressure with a real tap wrench. Starting hole quality is also a big deal, reaming is always recommended, but a drill on size may suffice. Always chamfer the hole before tapping, single flute countersinks are easy to use. Moly-Dee is great on most metals hand tapping, WD-40 on aluminum, dry or a safe coolant on plastic that won't eat it.

    Finally here is another good resource on understanding tapping.
    "Everything you wanted to know about taps but were afraid to ask"
    Everything you wanted to know about taps but were afraid to ask, styles of taps, class of thread , gh numbers , basic point in thread measurement , constants for finding pitch diameter and minor diameter of screw threads , thread constants for various percentages , relation of tap pitch diameter to basic pitch diameter , tap limits product limits and class of thread , how to order special taps

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    I was wondering about reaming. I read somewhere (can't remember where) that reaming isn't necessary in mild steel, especially if it isn't particularly thick work pieces. I also had the idea of welding a nut over the holes that are used for the locking levers just to add more thread depth so the threads don't get wallowed out out over time since the levers get used frequently.

    Yes, I planned on getting some tap fluid. Was going to get tap-magic, but if moly-dee works well for hand tapping, maybe I'll go with that. I'll see what pricing is like and go from there.

    Thanks for the tip on the "machine wrench", I was going make a handle that uses the chuck holes on the press's chuck to turn it, lol.

    I already have several piloted single flute counter sinks and have used them for deburring and chamfering holes drilled in steel, they work well.

    All the holes on this are through holes, so I don't need a bottoming tap.

    Ok, I think I'm good to go at this point. Learned a lot from you guys and I appreciate all the information.

    I'm just excited to get started. Wife got me a plasma cutter for Father's day and I'm itching to use it :-) No way I was going to use a bazillion cut off disks and grinding wheels to cut 3/8" steel for this thing!

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    Quote Originally Posted by Hydroracer View Post
    I was wondering about reaming. I read somewhere (can't remember where) that reaming isn't necessary in mild steel, especially if it isn't particularly thick work pieces. I also had the idea of welding a nut over the holes that are used for the locking levers just to add more thread depth so the threads don't get wallowed out out over time since the levers get used frequently.

    Yes, I planned on getting some tap fluid. Was going to get tap-magic, but if moly-dee works well for hand tapping, maybe I'll go with that. I'll see what pricing is like and go from there.

    Thanks for the tip on the "machine wrench", I was going make a handle that uses the chuck holes on the press's chuck to turn it, lol.

    I already have several piloted single flute counter sinks and have used them for deburring and chamfering holes drilled in steel, they work well.

    All the holes on this are through holes, so I don't need a bottoming tap.

    Ok, I think I'm good to go at this point. Learned a lot from you guys and I appreciate all the information.

    I'm just excited to get started. Wife got me a plasma cutter for Father's day and I'm itching to use it :-) No way I was going to use a bazillion cut off disks and grinding wheels to cut 3/8" steel for this thing!
    Reaming is not necessary with "H" taps in mild steel, it's a waste of time. Tap Magic is far and above the best cutting fluid, IMHO. Always, always, chamfer the tap drill hole before tapping. It's just a good habit to get into.

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    Quote Originally Posted by Hydroracer View Post
    I understand the science behind form taps, meaning I get why the hole has to be slightly larger than you would drill for cut threads (because the metal "moves" when the form tap goes in and comes back out due to the metal's "memory"). Also, alignment of the tap to the hole is critical, otherwise you will bust the tap.

    Still, I have the question, can 3/8" form taps be done manually, or do they require powered machinery?
    You said you're drilling and tapping in a drill press, is your tool runout less than .001",can you ensure that your hole will be on size within .0005"? If so then get a form tap.But my advice is to get a cut tap like the OSG one that I linked above for 10$.
    Also it's Steam Oxide, not black oxide,big difference.

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    Quote Originally Posted by Rewt View Post
    Tap Magic is far and above the best cutting fluid, IMHO.
    The thick stuff is better, it doesn't smell like cat vomit.
    Also Moly Dee is really good too.

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    Quote Originally Posted by Mtndew View Post
    You said you're drilling and tapping in a drill press, is your tool runout less than .001",can you ensure that your hole will be on size within .0005"? If so then get a form tap.But my advice is to get a cut tap like the OSG one that I linked above for 10$.
    Also it's Steam Oxide, not black oxide,big difference.
    I've never heard of steam oxide? Similar coating to...?

    Also, to OP, Moly Dee is nasty stuff (unless they have changed the formula). If you get it on your clothes might as well throw them away IMO.

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    Quote Originally Posted by Mtndew View Post
    The thick stuff is better, it doesn't smell like cat vomit.
    Also Moly Dee is really good too.
    If you ask these guys, anyway....Molly-Dee, How I love you. Let me count the ways.


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    Quote Originally Posted by Mtndew View Post
    You said you're drilling and tapping in a drill press, is your tool runout less than .001",can you ensure that your hole will be on size within .0005"? If so then get a form tap.But my advice is to get a cut tap like the OSG one that I linked above for 10$.
    Also it's Steam Oxide, not black oxide,big difference.
    I was not planning to use a form tap, I was just asking questions about the process in general for my own education.

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