[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]

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.

[msomerville]

You don't have a cog belt? My oldest machine is a vm24 from '96 I believe. It has a Cent5 control and my newer machines with Cent 6 have the cog belts.
What do you mean by it is always hunting for RPMs? Cuz on the screen my RPMs are always hopping around for some reason, but that never affected my tapped hole.
I would just be curious if I could do it. For instance we use to make some antenna assemblies and the holes for the aluminum base plates were for a 3-48 bolt. The holes were .15 deep and they needed all the thread they could get. That was the first time I tried a thread roll form tap. These taps form the threads instead of cutting, so no chips. I programmed the machine to tap .145 deep with a bottom style tap, and that was it. I don't know if you could do that with a floating tap holder.

[msomerville]

Someone posted on here that he uses a piece of wood to try it out on (rigid tapping). If it is correct your threads will be there. If not it will just strip out your wooden threads. Oh well no broken tools.

[merl]

jpawelk, you are correct, my machines are of the two speed type. I have one set up for high range and one set up for low range, I was not aware that a parameter had to be changed as well, I will check this out. These machines were set up this way when I took them over and I always asumed that they were just getting a little querky.
msomerville, yes though I'm emberassed to admit it, I do not have a cog belt drive on either machine. The modest increace in productivity does not merrit the cost of the conversion and the time lost to do the job. Bothe machines work well enough as they are to make shop rate on the jobs I do on them. They are good machines but are too old to make any major up grades to.
You may have read in one of my previous posts that we are planing to purchase some new machines so I'm not too up tight about the current machines perfomance. As to the "RPM hunting", what you are seeing on your screen is just what I'm seeing but somtimes when it goes into extream fluctuation I can actualy hear the spindle motor running up and down. Someone once told me that the reason it hunted like that was because the spindle encoder was either dirty/oily or the reader amplifier was getting weak. That sounds logical but, I'm sure going to check that parameter first. As to the ridgid tapping, every thing can be set up just right to do this accuratly but if the spindle snubbs in mid cycle (belt slipping) the tap will shatter. I use a compresion/ extention tap driver with a quick change collet. If I have to get right down to the bottom of a hole like that I usualy just stay a couple of turns off the bottom and have the "grunt labor" finish them to depth.