Tapping metric threads?

[c-hook]

Hey all you super smart guys-

 

I haven't tapped metric threads with our HAAS cnc's before. Can I use a standard G84 to do this. I'm not sure if it will work, being that the spindle and feed don't sync up exactly to whole numbers.

 

Any advice??

 

I'm tapping a M8 x 1.25

 

Thanks

[John13]

yes you can do it, just convert the metric to inch

 

 

The formula I was given years ago here is:

 

pitch x .03937=

(1.25) x .03937= .0492125

 

pitch x RPM = feed

.0492125 x RPM = feed

[?Mark]

or simply pick this tool from a metric library, type in feed(or rpm) and it'll calculate required rpm(or feed).

( it will not backplot correctly though without editing a tool )

hth

[Hardmill]

quote:

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Hey all you super smart guys-

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Keeb got it under control.

Proof positive you didnt need anyone smart

 

 

PEACE

[John13]

Or pick the tool from the metric library, after the values hit MM it will convert to inch and then save the tool

[c-hook]

Ok, thanks for the info. I just wasn't sure if using a feed of , lets say, 6.152 @ 125rpm, would actually feed that accurately or if it would round out the 3 place decimal and cause problems.

[c-hook]

quote:

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Keeb got it under control.

Proof positive you didnt need anyone smart

 

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lol....

That ain't right.

[Storkman]

quote:

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Proof positive you didnt need anyone smart

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Good thing or you would have been waiting a long time.

[Watcher]

Just complementing what John said in the second topic, and living in a "metric country", I think that the formula shown below it´s better (and easier to remember) for the conversion:

 

Metric pitch : 25.4

 

This formula sounds better for me because you don´t have rounding problems with the values.

 

For example: By using the .03937 constant for a 6.35mm (0.25") pitch, you get:

 

6.35 x 0.03937 = 0,2499995"

 

By dividing 6.35mm by 25.4 (1") you get exactly 0.25"

 

Depending on the case, you can get rounding problems. I know that usually the resolution of the CNC machines running in Inch mode it is 4 places after the decimal (0.0001" - 0.00254mm), but in metric mode, the resolution usually it is set as 0.001mm, so that for me machines running in Inch mode are more sensitive to rounding errors, since an error of 0.0001" corresponds to a 0.00254mm deviation.

 

Claus from Cimco states in his signature: "The real world is metric". Agreed.

 

Just kidding guys...

 

JM2C

[Thad]

Point taken, Daniel, but are you worried about a thread pitch being off by .0001"? I'm not. The machine probably isn't in sync within a tenth.

 

Thad

[c-hook]

Especially if it's a HAAS.

[Programinator]

c'mon guys Haas does ok with tapping

 

It just makes alot of noise and vibrates the whole machine.

[Watcher]

Hey Thad!

 

I agree with you and usually a error off by 0.0001" it´s not a big deal. But it depends on how deep is the thread and which kind of holder and tapping mode you are using (I mean, rigid or floating).

Let´s suppose that you are tapping a M16x1 with a depth of 100mm. If you get an pitch error off by 0.0001" per turn, the the total error at the final depth is 0.254mm, what is a considerable deviation if you are tapping using rigid option with a holder without any axial compensation. For floating tapping usually the floating holder will compensate the deviaton. But IMHO rigid tapping is by far better.

I used to get very good results in a VF2SS with rigid tapping option, almost 3 years ago, in my former job. I used to use ordinary collet chucks for that, and I never had any trouble with my threads, oftentimes very deep.

[Hardmill]

quote:

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Let´s suppose that you are tapping a M16x1 with a depth of 100mm.

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A hole tapped 4 inches deep ?? When has anyone ever seen anything like this ??

 

 

 

PEACE

[Guest]

I did an M30 x 90mm once.

 

Roll form on a Mat760 with a gear head

[Hardmill]

quote:

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I did an M30 x 90mm once.

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quote:

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M16x1 with a depth of 100mm.

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.629 vs 1.181dsia, thats a big difference.

 

 

PEACE

[Watcher]

Hey Hard,

 

I´ve seen this quite often for fine leveling of heavy assemblies. I saw that quite a lot in satellite assembly frames ang jigs as well.

[c-hook]

Ok, let's say that there is some accumulative error the deeper the tap goes. Now, when the spindle reverses and the Z axis starts traveling back up, is (should) everyhing going to sync up exactly the same way as it went in, or is there going to be the same error deviation, but only the opposite this time?

[Flycut]

If it goes in at one feed and spinle ratio and come out the same way there won't be no compound error.