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  1. #21
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    Quote Originally Posted by Hydroracer View Post
    I was not planning to use a form tap, I was just asking questions about the process in general for my own education.
    Form taps are great in ductile materials, but they do require a bit more precision than a cut tap.

    The big difference as Dew alluded to is hole size. I don't tthink you need to be within .0005", unless you are gaging with a plug gage for a 2b or 3b. For a "regular" bolt if the hole is within .002" (on larger sizes) it would probably be ok.

    Here is a chart, as you can see the hole size are different for form vs cut taps.

    Forming Tap Drill Sizes | Jarvis Cutting Tools

  2. #22
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    Quote Originally Posted by Mike1974 View Post
    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.
    Yeah MolyDee odor does hang around a bit eh? lol
    I just yanked the following from TapMatic's site Surface Treatments For Taps - Tapmatic Corporation

    Oxided
    Produced on surface of a finished tap by means of a steam furnace or cyanide salt bath. Well know heat treatment by which an oxide layer (Fe3O4) is formed on the surface of the tap. This will improve the adherence of threading agent which leads to improved output of taps.
    Categories of Oxide

    Steam Oxide: To counteract galling or loading lubricate tap surfaces. Best for low carbon, leaded steel, stainless and gummy material.

    Nitride and Oxide: For stress relief and light coating. Copper alloys of medium machinability.

    Nitride Plus Steam Oxide: To add wear life and reduce loading. High speed production tapping, poor lubrication. Steam Oxide Plus Nitride: To add wear life and provide self lubrication. Use in cast iron.

    Heavy Nitride Plus Steam Oxide: To add wear life in hard and dense metals. For tapping hard steel alloys, titanium, exotic metals and hard copper alloys.

    Black Oxide: Helps retain cutting fluid in the working portion of the tap. Improves Performance in stainless steel, steel forgings, tool and die steel, and hot and cold rolled steels.

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  4. #23
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    Get you a bottle of "TapFree" far much better than MolyDee or Tap Magic IMO.

    What's the deal with "BRite Finish" That just about all I've used in my past 50 plus years of machining. Spiral point, yes. Don't get me wrong, I've used coated taps too, but for most of my tapping it is bright finish spiral point taps for most threads.

    Ken

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    Quote Originally Posted by 4GSR View Post
    Get you a bottle of "TapFree" far much better than MolyDee or Tap Magic IMO.

    What's the deal with "BRite Finish" That just about all I've used in my past 50 plus years of machining. Spiral point, yes. Don't get me wrong, I've used coated taps too, but for most of my tapping it is bright finish spiral point taps for most threads.

    Ken
    Maybe, we use Moly-Dee predominantly on 316 SS and the taps last forever, also use it for running dies on SS. It is messy though, has the look and consistency of old motor oil. The OP sounds like he is on the right track now, thread quality and the time/money spent will vary with the customer's prerequisites, good luck and let us know how you get on.

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  7. #25
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    Quote Originally Posted by 4GSR View Post
    Get you a bottle of "TapFree" far much better than MolyDee or Tap Magic IMO.

    What's the deal with "BRite Finish" That just about all I've used in my past 50 plus years of machining. Spiral point, yes. Don't get me wrong, I've used coated taps too, but for most of my tapping it is bright finish spiral point taps for most threads.

    Ken
    Basically same principal as coated carbide inserts, they just last longer. With the exception of tapping/cutting aluminum, then it doesn't matter much as long as its not black oxide or any of "A" (ALTiN etc) coatings...

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  9. #26
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    There are elevendy-seven commercial brands and types of metal-cutting lubricants/coolants, and every one of them is better than all of the others.

    Over the last fifty-some years, I have used several dozens of them . . . and now prefer ones that don't stink, don't stain hands or clothing, don't make my eyes sting and water, don't attract vermin or putrify, and don't release noxious fumes if overheated.


    For hand tapping in steel, plumber's pipe threading oil that is available in small containers from just about any hardware store is good . . . as is Crisco-type shortening from the grocery store. I've known observant Jewish and Muslim machinists to use sheep and beef tallow, and many others -- including me -- too use bacon fat or lard. (the animal facts will putrify, but do work very well).

    My bottom-line recommendation is to bypads the hazmat fee and buy yourself an another good tap.

  10. #27
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    I'm going with a 4 ounce can of tap-magic. I can't find moly-dee in anything but 16 ounce sizes for $38+ and even if I start combobulating up other little machines (I have quite a few little induction motors squirreled away), I'd still never use even a 4 ounce container the rest of my life most likely.

    Then again, when you accumulate a new hammer, suddenly every construction issue becomes a nail, so who knows. I'll worry about more tapping fluid down the road should I need it.

    So, a couple of those $10 black steam oxide taps, one of those "machine wrench" tap handles to fit the drill press, a can of tap-magic, and I think I'll invest in a couple of the short cobalt drill bits too so the holes are nicer, and off I go.

    As for holding .001" runout, nah, I don't have a machinist quality press or mill, it's just a Delta floor press I use for my woodworking. By wood standards it has very little runout, but it certainly won't cut it for precision machine work, but I think it'll be fine for tapping a few holes in mild steel...certainly more accurate than eyeballing it. Don't get me wrong, I've drooled over metal lathes and mills for a while, but decent ones are out of my budget.

    Now, just gotta find a good local source for the steel. You'd think being in PA, it'd be everywhere, but looks like I'll have to make a trip down around Pittsburgh (2 hour drive).

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    Quote Originally Posted by Hydroracer View Post
    Now, just gotta find a good local source for the steel. You'd think being in PA, it'd be everywhere, but looks like I'll have to make a trip down around Pittsburgh (2 hour drive).
    If you just need a leetle bit McMaster is my go-to. Kinda 'spensive but it's here the next day.

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    A "leetle bit" is relative, I guess. I want to buy a little extra in case I fudge up some parts, and it's always nice to have some laying around for other stuff, but a short list:

    16 feet of 3/8 x 1-1/2 flat bar
    16 feet of 3/8 x 2 flat bar
    4 feet of 1-1/2 x 1-1/2 solid square
    2 feet of 1-1/2 x 1-1/2 x 1/4 square tube
    3 feet of 1/2" rod
    1 foot of DOM tube (3/8 ID, 1/4 wall, if I can find it). needed to make a hinge, so something similar with a proper sized bolt or rod would suffice.
    either a couple of 12" x 12" 3/8 plates, or a 12" x 24" piece (looking around, these are pricey)
    another piece of 3/8 plate, around 8" x10", or an even bigger single plate and cut it out

    That's for the basic grinder, platen and table. I still need to add to the list to build a few other attachments to go with it, like a small wheel attachment, a large wheel attachment, and a couple others, but for now, I just want the basic machine, platen and table. The other attachments will come later.

    I can find it all at an online metal place and the steel itself is mostly reasonable, it's the shipping that hurts because of weight and size (I can live with three 6ft pieces instead two 8 foot pieces for shipping purposes), but it's still a lot to ship. I think for $100+ in shipping, I'll drive a little to get it in person...

  14. #30
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    Quote Originally Posted by Hydroracer View Post
    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?
    .
    oversize tap normally only used on heat treated parts where hole gets smaller and or out of round after heat treatment and H number varies based on size of tap
    .
    many paint tap shank green that way when looking for tap in a drawer its easier to see its not a normal tap. there are thread plug gages to check if thread pitch diameter is GO or NOGO tolerance. it has happened before somebody used oversize tap when wasnt suppose to and part got rejected. also you can order a tap but should check you got correct ones. for example 10-32 and M5 taps look similar and easy to confuse the two. warehouse clerk putting stuff in a bag or box can easily make a mistake

  15. #31
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    Quote Originally Posted by Mike1974 View Post
    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.
    I was wondering too until someone posted a quick blurb that said it converts surface layer to Fe3O4...that's when the lightbulb came on for me. Fe3O4 is magnetite. Steam oxiding is just one method to apply what's known as a "conversion coating" onto the metal. Black oxiding achieves the same result, just through a slightly different method. The point of them is to simply convert a tiny layer of the base metal to magnetite. Steam oxiding uses steam, black oxiding generally covers three temperature based methods, "Hot blackening", "Mid temperature blackening", and "cold blackening." You might be more familiar with these processes if they were called by another well known name: gun blueing.

    I initially confused it with parkerizing, which is another conversion coating, but is phosphate based and in my experience with it on firearms, doesn't last long. Interestingly, it's claimed that parkerizing is tougher than blueing. I find them to be about the same in terms of wear resistance...which really isn't all that great either way.

  16. #32
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    Sounds like you already bought your tapping fluid, but when tapping mild steel like A36/1018 for a home project I generally use Oatey/Rigid dark thread cutting oil from Home Depot. Really cheap and handy and has always worked well for me. It's in the plumbing section.

    https://www.homedepot.com/p/Oatey-16...E&gclsrc=aw.ds

    Also if you like numbers and want to mess around check out this site.

    UN imperial screw thread calculator

    It's even more useful once you get a lathe.

  17. #33
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    Quote Originally Posted by Hydroracer View Post
    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:
    I spent most of my professional life doing fabrication, installation and repair like that. I found you can do almost anything with plain old spiral point plug taps with an H3 limit, in fractional sizes. Most all of my taps both personal and for work, are GTD/Widia spiral point plug taps with H3 limits, they'll work with all commonly available fasteners. I've been very satisfied with that setup. I use dark cutting oil, same stuff plumbers use. (sulfurized)


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