Hand Tapping 316 SS - need help - Page 2
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  1. #21
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    Sorry, I missed AD Design's post. The stuff isn't magnetic and I don't get any sparks off the belt grinder so I'm pretty sure it's the austentitic 300 series and not 400 series. Now that I'm getting the lower hardness I think it was probably just cold rolled and work hardened. I haven't had a chance yet to see if the annealing helps my tapping though.

    Thanks
    Dave

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    Thanks Jim

    Unfortunately Fort McMurray keeps getting wacked. We just had a 1 in 100 year flood that flooded our only hardware stores so I'm not sure when they'll be open again. The water was three feet up the front door so probably lots of mess to clean up. I'm back down to Edmonton at the end of the month so I'll pick up some better cutting oil then. As for the two flute gun tap, I'm trying to source some good quality ones. MSC has what I want but when I checked, shipping was US$ 40 for a $15 tap. They use UPS as well and UPS usually springs a surprise border duty charge on me and then play hide and seek with my orders. I'll keep looking around though. Maybe there's some more reasonable sources.

    Just a question about the gun tap. With pushing the chip ahead, I'm assuming you'd only want to use that if you were tapping a through hole? What would you suggest would be the way to tap a blind hole?

    Regards
    Dave

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    I have never had much luck with those spiral taps and if they break they are a real pain to remove. I like Jims info on the 2 flute tap as they are strong. I have had good luck using bee's wax too when I'm in a fix, and that should be easy to get up there. I was thinking if you want I can mail you something. Or Lucky 7 is up in Winnipeg and I bet he could mail you something with no customs fee's. I'll message him, he''s a friend of mine.

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    A quick run down on tap types/nomenclature:

    Spiral flute: Looks like an endmill. Often a bottoming tap, but not necessarily. Has helical flutes (as the name implies) that pull chips up and out of the hole, used for blind holes. Generally weaker than a spiral point tap, due to the thin web caused by fluting. Available as 2, 3, and 4 flutes, generally.

    Spiral point: Looks like a bolt with a radiused tip and straight flutes cut along its length. Pushes chips down and through a hole. Generally only used for through holes. Also called gun taps. Generally the strongest type of tap.

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    Quote Originally Posted by Dave Hodson View Post
    Thanks Jim

    Unfortunately Fort McMurray keeps getting wacked. We just had a 1 in 100 year flood that flooded our only hardware stores so I'm not sure when they'll be open again. The water was three feet up the front door so probably lots of mess to clean up. I'm back down to Edmonton at the end of the month so I'll pick up some better cutting oil then. As for the two flute gun tap, I'm trying to source some good quality ones. MSC has what I want but when I checked, shipping was US$ 40 for a $15 tap. They use UPS as well and UPS usually springs a surprise border duty charge on me and then play hide and seek with my orders. I'll keep looking around though. Maybe there's some more reasonable sources.

    Just a question about the gun tap. With pushing the chip ahead, I'm assuming you'd only want to use that if you were tapping a through hole? What would you suggest would be the way to tap a blind hole?

    Regards
    Dave
    There has to be more than a few tooling suppliers in Edmonton.
    SOWA 123-308 Yellow Ring HSSE-V3 Spiral Point Tap - 1/4 inch at Edmonton Fasteners and Tools Ltd.
    Thomas Skinner Company Profile

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  9. #26
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    Quote Originally Posted by TeachMePlease View Post
    A good quality tap is your best friend. A cheap, home depot bought tap is your worst enemy.

    Good tap brands include: Guhring, Emuge, OSG, Balax, Nachi, and probably others I can't think of right now.

    Bad tap brands: Anything you can buy at home depot or lowe's or ace hardware.
    I agree that quality taps will make the difference. I buy my taps from local machine shop supply. They typically come with three flutes and are much stringer and better than the hardware store types

    I have yet to break one, but I will also drill a bit oversized since typically I'm doing hobby work.

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    As a fellow Canadian I hear what you’re saying about difficulties getting what should be easy to source tooling. I’m just a little guy and don’t order huge quantities of anything. I regularly order from McMaster Carr and ship to an address just across the line. This obviously doesn’t work at the moment with the border shut. I also use KBC and Traverse tools. Not the cheapest, and not always best quality but no border issues.

    There are smaller mom and pop tooling stores local to me, but that doesn’t help you in Fort Mac.

    Good luck.

    L7

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    Like MattiJ said, Edmonton is likely my best source for direct pickup and I'm checking sources there - there's a few. Also checking some online options.

    Still need to figure out what I'm looking for for a blind hole though. Looks like a good two flute spiral flute bottoming tap in a slightly larger drill hole using my drill press to add a bit more downward pressure and some better tapping fluid. There's a suggestion I could start with a two flute spiral point and I'll give that a try but that introduces a stop/start that some have said creates a problem. Anyway, lots to try. Thanks for all the help.

    Dave

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    If you try the spiral-point in a blind hole you need the hole to be at least 25% longer than the depth you intend to tap. 50% is better. Also, most spiral-point (gun) taps come with a rather steep point on the end. Grind it off to avoid hitting the bottom of the hole, and/or packing the chips in any tighter than necessary. You can grind it right up to the point just before the first 'tooth' starts. Doing this will make a tapping guide almost essential for hand tapping. The chip can usually be picked out with a 'crochet hook', but if its a one-time assembly some people leave the chip in the hole.

    Really, much of the benefit of a gun tap is lost when you're turning it by hand. Stopping for any reason in many stainless types will cause problems. You will be absolutely amazed at the difference a good HSS tap makes over what you get at the hardware store. Some of those are carbon steel and will cause problems almost immediately.

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    Thanks Gordon - I'd been wondering about hole depth. I was thinking I needed two different taps to finish it off but I never considered grinding one down

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    My 1/4-20 taps have a class of fit equal to GH3. It is stamped as GH3. It is .0015 above normal diameter.
    Bought the taps when the class of fit over the counter buy usually gets you a GH3 if you don't ask for a GH1 or GH2.
    If I had to buy again I would get a GH2 or GH1.

    Class of Threads, H Limits - Tapmatic Corporation

    I need to replace a 2-56 tap that broke in some SS. Had to sacrifice a carbide center drill to remove the broken tap from the hole.

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    That's good to know. I'd briefly read about class of fit but hadn't really considered it.

    Thanks
    Dave

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    Hi Dave:
    I'm with Mattij; this is way too hard for 316.
    How confident are you that it's actually between 45 and 55 RC.
    55RC is pretty hard, you cannot get a file to bite at that hardness without heavy pressure, so I'm convinced you either have something other than 316 or it ain't 55 RC
    Is it magnetic?

    Cheers

    Marcus
    Implant Mechanix • Design & Innovation > HOME
    Vancouver Wire EDM -- Wire EDM Machining

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    Hi Marcus

    For annealed 316 yes, but I'm not sure it's way too hard for work hardened 316 - maybe someone with more knowledge than me can comment on this.

    I've got a Wilson Hardness tester that I use regularly with my knifemaking and heat treating and a calibration test block to confirm it so I'm pretty comfortable with the higher readings.

    I guess I'm a little surprised that so many have difficulty with a high Rc when everybody agrees that one of the main challenges is work hardening in drilling and tapping. I'm just starting to learn about this stuff but dwelling a little with my drill work hardened it to a point that I struggled to get it started again. It seems reasonable to me that any cold rolling or other manufacturing process could cause similar surface hardening.

    An hour in the kiln at annealing temperatures lowered the Rc to mid 20's which is what one would expect for annealed 316 so that suggests to me that this barstock was surface hardened at some point. Out of curiosity it would be interesting to cut a section off the bar and see if the centre is similarly hard or is it just the surface. If I get some time, I'll do that.

    All the best
    Dave

    Edit: May 17

    Sorry, forgot to mention that it's not magnetic. Also, it doesn't produce any sparks on the belt grinder so I'm pretty sure it's at least an austenitic steel of some kind. By the way, just had a chance to have a look at your web site and shop - pretty amazing - congratulations.
    Last edited by Dave Hodson; 05-17-2020 at 08:17 AM.

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    Just a quick question for TeachMePlease (or anyone actually).

    I was just reading about Hand Taps and Power Taps and the suggestion there was to try a Power Tap that would normally be used on a CNC for hand tapping as opposed to a hand tap. The impression I got was that there are crappy hand taps (like the ones I have), good hand taps from quality manufacturers (like the ones I should be using) and then there are power taps for CNC's which apparently are another level up.

    Am I understanding that correctly? Are there such taps and would people like myself benefit with a power tap made for a CNC over a good quality hand tap? Bear in mind, the majority of holes I'm tapping by hand are in the 1/4" and under range.

    Thanks for your help
    Dave

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    I call them high performance taps at the counter. That's all they need to know. Never got junk yet. Nothing made in China as well.

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    The 'cnc' taps are just those with the spiral-point or spiral flute which tend to take care of the chips by ejecting them either top or bottom. Hand taps often have a gentler taper to aid starting, and are available in progressive sets. Its a definite yes that you can get better results by using machine taps, the issue here is the material you're trying to tap and problems caused by stopping and starting during the process.

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    In our shop we tap things in the following order:

    1. If it's on the CNC lathe or mill we use spiral flute taps and rigid tapping cycles.

    2. If it's on the manual lathe we use a hand tapper I made that guides the spiral flute tap out of the tailstock.

    3. If it's drilled on the knee mill or the drill press we almost always tap it using a hand tapping machine we bought from Enco. We almost always use spiral flute taps. Here is the current version at MSC: https://www.mscdirect.com/product/details/09491002

    4. If we have to tap something in place or in a vise we try to figure out the best way to guide the tap straight and we use spiral point taps.

    Note that the ONLY time we use anything other than spiral flute taps is when we need the extra strength and guidance provided by a spiral point tap. A guided spiral flute tap takes less power to tap, causes less work hardening in some materials, and doesn't leave chips in the bottom of a hole. (Customers tend to object to having chips left in a hole, esp our military customers...)

    We break almost 0 taps if we use steps 1-3. We break a lot using step 4 and avoid that method as much as possible. Bought a big set of carbon steel taps and dies from Harbor Freight a while back, the only use we have for them is to clean up existing threads, they're about useless for cutting new threads. We almost always use carbide taps vs HSS unless it is a special thread for a limited run and the dollars don't add up.

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  25. #39
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    You're right Gordon. The material is the issue although I'd have to add that I'm coming at this as a complete nube with a Canadian Tire set of taps. If I'm going to solve this, I'm going to have to up my game a bit.

    I am getting some conflicting information in that there are some over on the knife forums using 316 that recommend short forward/reverse steps as their preferred tapping method. I'm not sure why that works for some and not for others (especially when the full bore ahead, no stopping method is the only way to drill it) but I'm guessing there are some reasons I'm not clear on yet.

    Regards
    Dave

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    Post 38 #4. If we have to tap something in place or in a vise we try to figure out the best way to guide the tap straight and we use spiral point taps.

    If you are tapping by hand with a free-hand wrench then the tap can rock about the center axis. I will always support the tap/wrench from the back with
    a center point in a drill chuck or similar. I couple of times I was going to use a cheap tap in the lower wrench. But the tap had no counter sunk hole
    at the end of the shaft like the tap in the picture.

    dsc_0744.jpg


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