I cant think of anything in cofig that could affect threading in the way you are describing but if you attach your latest xml I will have a check through it. Also attach the code you are using.
Hood

Hi Experts,
I also have been facing the same problem of pitch variations in threading with SS. Strangely I am not able to find any clear guidelines about interfacing encoder for threading with SS Manual. I am not clear how the encoder should be connected to SS card. Should all A B and Z be connected in port3 which has encoder input. Should only A or B be connected and configured as Index or timer input.
I have connected 'A' phase of 1000 PPR encoder to port 2 input of SS and configured it as index. I get a steady RPM indication at 348 RPM. But when tried to thread with wizard code for rod dia of 28 mm and thread length of 60 mm, depth of thread as 2 mm, I get a 20 pass code. When the program is run, threads are not matching and instead of a clean thread of 2 mm depth, I get a roughly turned part due to overlapped threads.
I am attaching my XML and Prog files. Please advise.

Mach expects one single pulse per revolution of the spindle, which is what the SmoothStepper also expects. You can try just using the Z from your encoder (which provides 1 pulse per revolution.)

Jeff,
Thanks for the reply.
I understand that SS gives much better performance in threading just because Mach with PP sees the index just once a revolution and hence slow to respond with spindle speed variations, while SS can take index as encoder inputs and hence quick to respond and gives accurate threads.
Also I get RPM indications very well accurate. I also get started well with the pitch but as the passed increase, threads get overlapped.
And I fail to understand the use of encoder at spindle if you are supposed to use just Z phase instead of total PPR. Please clarify. I am a lot confused.
Also there is given a parameter as Encoder index multiplier up to 4098 pulses in the SS configuration menu. I have set this as 1000 because my encoder is 1000 PPR and it gives me fairly accurate RPM on the DRO.
Please clarify. Someone using encoder practically may respond.
M Vyas

The Smoothstepper only uses an index pulse the same as Mach, the difference is the Smoothstepper controls threading external to Mach and thus the index and threading are all in the hardware so theoretically should be much more stable.
I would suggest you try the Index input on Port 3 if you are using the USB Smoothstepper. If your encoder has differential Index signals then use one of the differential Inputs on port 3 for it.
Also reduce filtering in the SS plugin for all functions to as low as you can, 0 is preferable but if you need some filtering then start with the 1.43 (smallest increment)

Hood

Hood,
Thanks for the reply. But I fail to understand that while using Encoder with SS, there are three phased available A /B /Z . While A and B give pulses 1000 Times a revolution for a 1000 PPR encoder like mine while Z  gives only one per revolution. Now, if I am supposed to use only Z, for one PPR, why go for encoder and not go for simple sensor fitted over spindle like Inductive Proximity Sensor?

Also it is strange that while it has a dedicated encoder port available all the A/B /Z inputs, it just takes Z as index. This will surely not give best result as compared to if done with 1000 PPR Phase A or B.

So,if  it is confirmed that I have use only one pulse per revolution, then what is meaning of the SS setup parameter Encoder Multiplier or something like that..
M Vyas

The benefit may be twofold. First is if you are using a servo for the spindle it will have an encoder on it so there is no need to fit an additional signal to feed the Index input. Second is the encoder is likely to have high quality electronics and thus will likely have a cleaner Index pulse and thirdly Encoders are often differential so you have less problems with noise that a single ended input could have.

I dont think I have that setting in the plugin, I still use an older plugin as newer ones had issues so I went back to the old one and have not bothered updating since.
Hood

Hi archcomp,
Mach needs a index  pulse that is at least 50% wider than the other pulses. Mach is watching that  pulse to start the threading.
I guess your encoder don't provide that wider  pulse.
just a thought.
Alex

Mach when using the parallel port does not use the Timing input now so it should not be set up.
With the SmoothStepper I dont think it ever did use the Timing input so again it should not be used.
The only input needed for threading is the Index and that is what you should use.
There was talk a long time ago that Greg was going to use an encoder to fully sync Z to spindle but 2 or more years passed and it was not done so I suspect that is still the case and that it will not be done. Whether that is for hardware/software reasons or commercial reasons I cant say.
Hood

Hood,
Thanks for the clarity. I will try the setup tomorrow and post it here after confimation.