Rigid tapping metric threads

[msomerville]

I can't seem to get this tap programmed right. I have cut plenty of standard threads but I can't seem to get this metric tap to work. I do have a compression tap holder but I was just trying to get this right rigid tapping.

[mholden]

If you are using conversational programming it is asking for threads per unit.
English 1/4 - 20 you would put in 20 for the treads per unit.

If in metric 6mm x 1.5 = .6666 threads per unit.
metric taps give you the lead not the treads per mm.
just take 1/lead

[msomerville]

Man I was looking too hard into it I think. That was too easy.

If only every problem were that easy.

Thanks for your help.

[Kiwi]

Am I missing something?
I would have thought if your machine is set in inches and you require to tap a metric pitch of 1.5 then you would enter 16.933 (25.4/1.5) as this is the number turns per inch.

[mholden]

Yes, if it was in english, I think he was asking about if it was programmed in metric

[msomerville]

I am programming in metric for this job.

[Kiwi]

I understand now. Didn't realize that you were doing the whole job using the metric system.

[Mitsui Seiki]

You know all this but I thought I'd write it down anyway.


Pitch, metric

Metric | Norm. pitch | Fine pitch
M 2,3 | 0,4 | 0,35
M2,6 | 0,45 | 0,35
M3,5 | 0,6 | 0,35
M4 | 0,7 | 0,5
M5 | 0,8 | 0,5
M6 | 1,0 | 0,75
M7 | 1,0 | 0,75
M8 | 1,25 | 1
M10 | 1,5 | 1,25
M12 | 1,75 | 1,25
M14 | 2,0 | 1,5
M16 | 2,0 | 1,5
M18 | 2,5 | 1,5
M20 | 2,5 | 1,5
M22 | 2,5 | 1,5

[merl]

mholden,
When I "fill in the blanks" on my CentV & VI controles (ridgid tapping not an option for me) I simply convert what ever TPI I have to a lead as you say, and then multiply that by the RPM to get the required feed rate.
Ex. 1/4-20 tap at 200 rpm converts to .05" lead x 200rpm =10.0 inches per minet feed. If I have a Metric tap I simply multiply its given pitch by.03937 first and then by what ever RPM I have selected.
Pretty much the same thing you are doing but, I can not ridgid tap on my machines because the spindle speed encoder is always about a hundred rpm off from what I have programed (not in the spn spd overide switch either) and I just plain don't trust 'em. What would be the advantage in ridgid taping anything if I have to worry about breaking a tap?

[jpawelk]

Originally Posted by merl mholden, When I "fill in the blanks" on my CentV & VI controles (ridgid tapping not an option for me) I simply convert what ever TPI I have to a lead as you say, and then multiply that by the RPM to get the required feed rate. Ex. 1/4-20 tap at 200 rpm converts to .05" lead x 200rpm =10.0 inches per minet feed. If I have a Metric tap I simply multiply its given pitch by.03937 first and then by what ever RPM I have selected. Pretty much the same thing you are doing but, I can not ridgid tap on my machines because the spindle speed encoder is always about a hundred rpm off from what I have programed (not in the spn spd overide switch either) and I just plain don't trust 'em. What would be the advantage in ridgid taping anything if I have to worry about breaking a tap?

How do you know that your spindle speed is off about 100 rpm? Are you looking at the display's read out or are you using a tach to meaure the rpm? If the actual spindle speed is off, you may have to adjust a parameter in the spindle drive so that the rpm matches the programmed spindle speed. The advantage of rigid tapping is that it is much easier to program and more accurate that soft tapping.

[merl]

jpawelk,
I'm sure your right that it's probably a parameter that needs adjusting but, what I also failed to mention was that the spindle also sometimes hunts for the programed RPM and, has even gone into alarm when it sometimes goes outside of the parameter limits (+- 150 RPM I think )
The spindle motor is set up for low speed operation (100-2000 RPM) on the one machine and high speed on the other (about 500-5000 efectivly) but, also relize that they are bothe V-belt drive not cog tooth belt as they should be so the RPM thing is a moot point. Those little old naggs won't push a 1/2-13 tap through anything more than aluminum.
I could probably get some more time out of them if I were to convert them over to a cog belt drive but, the boss already cringes when I take a roughing cut as it is.
I would like to get the RPM thing fixed though. The other machine is rock steady at any speed or load ( untill I snubb out that is)

[jpawelk]

Merl,

Your machine may be a two speed machine and if that is the case, you need to change pulleys and also change the spindle range parameter found under (F7 Parms), (F9 Ctrl). Make sure that the parameter matches the physical pulley selection that you make.