[jjjearls]

I don't recall having problems tapping on this machine before (MX-45VAE OSP-U100M), but I am using a fine thread machine tap for the first time and the crests are too large, but the minor and major diameters seem okay and the screw threads in fine, although it is a looser fit than it should be. The hole before tapping is fine. The machine is set up for rigid tapping. There is no apparent problems with the drill or the tap. I am all out of ideas. I am using G84 with unit/rev set (G95). The machine settings and feedback for the feed and speed are all correct while tapping. Anyone have any out-there ideas for other things to check? The short story is: the threads work and everything seems to measure fine, but the threads are definitely crappy. I am tapping into 1/2" A36 (mild steel) flat bar at 290rpm using a 29/64" drilled hole. Did I miss any details?

[deadlykitten]

hi, when tapping creates problems, is good to compare actual setup with another, using same tool, so not to blame the tool

thus is good to considere / assure that the tool is correct

we have a manual taping thing where i can test things ( check attached ), so if they work there, then also the cnc should deliver it

a tap longitudinal movement is not linear, but with small deviations, depending on it's precision class and on the material characteristics a fine pitch thread is also affect by this, and the impact of the cnc sync is much greater : thus the desincronization leads to much more wear on a fine pitch tap, comparing to a normal pitch tap : so use floaters

each cnc syncs rigid with a tolerance, and that tolerance is <> tool crafting tolerance, even if both machine and tool have same tolerance class, and this difference leads to stress on tap teeth is there a floater in the house ?

the tail of a tap may oscilate inside a cone, not only when the tap starts, but also among the way : 2 dial comparators on the tap shank may show this / the biting of a tap is not simetrical, like when drilling, but more like when drilling with a drill with 2 inserts, thus there is a tendency to tilt : this requires a floater with small angular or radial play

if there is no holder in the house, you may build one, similar to holding threading dies on a lathe, inside the tailstock : thus do something so to allow the tap to self feed a quick change tap collet chuck with overhang ? the overhang is there to allow radial play, and the collet chuck should allow self feeding, because it is not a very precisional part, but with some play within it, so you may achieve self-feed without a self-feed holder ... kind of

try also to tap at hand : does it cut ?

if a tap cuts, and if it is self feeding, then most problems are eliminated so does your tap cut, and is it self feeding ?

the threads work and everything seems to measure fine, but the threads are definitely crappy

... maybe i know how is to deliver messy threads that pass the go and no-go gauge & maybe sometimes is enough for me to find the cause, not also to fix it / kindly

[jjjearls]

Thanks for the reply deadlykitten. Using the tap to hand-tap was one of the things I plan to try. It is a brand-new tap from a quality manufacturer. I don't have any floating holders of any kind to try that, nor do I have another machine I can test the tool on (except by hand, of course). If a very experienced machinist was here with me, I'm almost certain that person would know right away what was wrong. But I don't have any of that experience at hand.

[deadlykitten]

hello jjjears, i was going to send you some photos, to show you how to achieve radial and floating without a specific device.

even if the tap is new, from a very good brand, this does not mean that the tap is ok ... maybe it is not sharpen properly, and maybe you had the luck to hit a lower-quality tool

is good to be sure about the tool and the holder, so to eliminate such kind of problems; only after you are sure the tap cuts and the holder delivers, if something happens, you may blame the fixture, material or code; considering that fixture and code are ok, it may be the material : to test it, tap a piece of aluminium, or whatever else that is easy to tap

Using the tap to hand-tap was one of the things I plan to try

hand or classical mill that allows the tap to self feed ( check attached image )

if tap delivers, then use same cutting specs on the vmc, and compare results

if thread on the vmc looks nice, cut a few more, then, if all threads look nice and pretty similar, if you wish, increase rpm a bit ( + 2 .. 5 .. 10, etc %) / kindly

[rcs60]

can you post the program for the tap ?
what is the tap size and pitch ?
any problems with other tap sizes ?
are you running coolant if so flood/mist ect ?

There has been some discussion in the past about low rpm and tapping being that the higher rpm reads the rpm resolver spot more often giving you a better thread
this also depends on the type of machine you have and what it is capable of doing

[deadlykitten]

hello again pls check attached images; they are about the quick-change system from a self-centering tapping arm ( showed in post 2 )

this system does not have radial nor axial compensantion, but it has some play within it

taps are always self feeding & they are used until they get such a wear, that a screw no longer fits inside the tapped hole ( this means good tool life, and tap breaking occurs rarely )

my point is that such a system helps, you may buy one, or craft one; also on youtube there are some simple but good solution about in-home made floaters, and i believe that it is possible to craft one also for a cnc / kindly

[Superman]

G284 is normally for syncronised (rigid)
tapping
G84 is the basic cycle best used with a T&C(tension/compression) holder

[OkumaWiz]

G284 is normally for syncronised (rigid)
tapping
G84 is the basic cycle best used with a T&C(tension/compression) holder

Superman may be on to something here... unless your parameter is set so that G84 is for rigid tapping, it is NOT synchronized.

[jjjearls]

rcs50, I realized I told you my tap drill size, but not the tap size. It is 1/2"-20. The code is this:

G15 H2
G00 G17 G90 X-6.5 Y-5.5 S290 M03
G56 H70 Z4.
M08
Z2.2
G95
G71 Z2.2
G84 X-6.5 Y-5.5 Z1.25 R2.2 F.05 M54
X-3.5 Y-5.5
X3.5 Y-5.5
X6.5 Y-5.5
G80
Z4.

So far I haven't noticed any tapping problems, but we don't do a lot of tapping. And everything so far has been coarse threads. I always run flood coolant. I have been using G84, but my machine is set for synchronized tapping on G84. I can try G284 just to check. I haven't had a chance to check the tap by hand yet as I am currently cutting keyways on the machine.

One weird thing in my manual about G84 is where it says this: "The G84 code calls either the conventional float tapping mode or synchroized tapping mode depending on the setting at bit 7 of optional parameter (bit) No. 17. If the synchronized tapping specification is not selected, the float tapping mode is called regardless of the parameter setting." I have no idea what it means by "synchronized tapping specification is not selected".

edit: Just digging into this a little bit, there is an alarm (2262 code 33) with similar wording. I think this means that potentially this option did not come with the machine. So if I try G284 and I do not get an alarm, then this problem would be ruled out.

[deadlykitten]

One weird thing in my manual about G84 is where it says this ...

hi jjjearls, i also read that 4-5 days ago, and it sounds funky ... it means that g84 syncronizes SZ with normal accuracy ( for floating ), or with increased accuracy ( for rigid tapping ); you toogle the accuracy level by editing the parameter

there is an alarm (2262 code 33)

i just checked that : seems to be a missing spec alarm ?! ... yup, go try G284 / kindly

[jjjearls]

Well, G284 is a valid code on my machine, but doesn't make a difference in the thread. I did 3 holes on Friday: one tapped with G284, one hand-tapped with the machine tap, and one hand-tapped with a straight-fluted tap. They all appeared to be the same. At this point, I'm just going to continue on tapping whatever I need to until it becomes an issue or I have a chance to do a rigorous test with the tapping.

[Superman]

Reading your 1st post.
... what do you mean by "crests"
1- minor diameter of thread
or
2- radius of the vee at the major dia

if #1 .. measure core diam before & after threading.
if #2 .. check tap to be correct form and tolerance range...ie UNF UNEF UNS 2A/2B

[deadlykitten]

try cutting the thread in half, so to view its section ? maybe it helps ...