Problems with tapping head.

[Chuck Reamer]

I finally set up the 4th axis and tapping head today. I tried to tap a 1/2NC thread in to some plastic.

I have tried to a few different things, and all it seems to do is pull out the tap out of the collet. I doesn't even show any signs of reversing spindle when retracting.

Here is the code I am using, just one hole. Its a little butchered up because I have changed it a few times.


g54
g00g17g40g49g80 g90
m00t5m6(27/64 t drill)
s1000m3
g43h05
g00z0.2
x0.0y0.0
g83x0.0y0.0z-1.2r.2q.2f10.0
g80
m5m9
g91g28z0.0
m00
g00g17g40g49g80 g90


m6t10(tapping head)
m3s500
g43h10
g00z1.0x0.0y0.0
g1z-.8f38.46
z-.64f65.0
z.5f38.46
g1z.25
g94g00z4.0


m30


Am I missing something very obvious, I have tried several different methods for retraction. The large head has a reverse ratio of 1:1.75, with .160" until clutch engagement.

I have only rigid tapped or used tension compression holders on a CNC in the past. On a drill press self reversing tapping heads work great, I am a little bit baffled with the situation.

Could some one post a tapping cycle of there own to look at.

[prototypeCNC]

Looks fine to me, I don't have that particular tapping head, but there should be a clutch adjustment. Set it on it's lightest setting.

I write my code slightly different, but your should work

m3s500
g43h10
g00z1.0x0.0y0.0
g1z-.8f38.46
z-.64f65.0 ****** I change this to g01 z-.025 f1000(shouldn't make a difference at all)
z.5f38.46
g1z.25
g94g00z4.0

I am guessing your clutch isn't kicking properly.

[Chuck Reamer]

Thanks for the reply, I had the clutch set on the lightest setting and changed it to about the middle. I will try it again on the light setting and see what happens.

I am also going to try the change in code you made to see if it helps.

[mayhugh1]

Did you find your problem? I've just started messing with tapping myself. It looks to me like the main problem is that your'e not feeding up fast enough to account for the head's 1.75 reverse ratio and 500 rpm is a tad too fast for a 1/2-13. with this combination. I think this code at 400rpm would do it:

G0 Z.1 (staging point)
M49 (turn off feedrate over-ride)
G1 Z-1.1 F30.15
G1 Z-.54 F65
G1 Z.66 F52.8
G1 Z .1 F65
M48 (restore feedrate over-ride)

and the above feedrate rates include a bit of underfeed as recommended by Tormach. The above code is what is created by their M871 tapping macro set for 13 tpi for the large tapping head. - Terry

[Chuck Reamer]

Thanks mayhugh1 I will give that code a try, I contacted Tormach and they said to try it will the clutch set to 4. I have yet to have time to try it out but hopefully this week I can give it another attempt.

I will post back and let you know how it worked.