Error in manuals

[B2]

Hi @Scott-ak

It is not uncommon that the feed rates and the x-feed rates are incorrect on a lathe face plate and in some manuals. Which lathe are you dealing with?

I spend considerable time generating a spread sheet work book which calculates the TPI, Pitch, feed rates, and x-feed rates (imperial and metric) for almost any lathe. I set this up for my PM1440GT, but then added other lathes to the workbook as individual lathe work sheets. It is designed in such a manner that you copy one of the currently available worksheets that have been developed for a lathe, perhaps similar to yours or even yours, and then you can modify it to your lathe gear box, transpose gears available, lead screw, saddle gears, lead screw, etc. Then you can use pull down menus to calculate any combination of gear settings. There are also macros supplied which will automatically generate a table of all possible values achievable from your lathe. There are other macros available for sorting and searching this table. Without access to the lathe it is almost impossible for me to figure out the gearing for the x-feed, but the feed rates are directly relatable to the TPI or pitch values. You will find that there are far more possible TPI and feed rates available than are mentioned in the manuals or on the lathe plates.

You can find this software at:

Nov. 6 2023 Excel workbook file name: TPI_ManyLathesRev1 NB06_0054.xlsm

I hope to update the macro software one of these days to do a better job of removing duplicates. Let me know what you think.

Dave L.

 

[MikeWi]

It would be good to know which machine this is, but when in doubt, follow our manual. The printed one from the factory is removed whenever we can do it, because those are always bad.

 

[rwm]

120, 127..close enough. Just make it a loose fitting thread.

 

[B2]

Upper part of picture is the manual, the lower from their website. Spent way too much time trying to figure out why pitch was off.

Maybe I am missing something from your first post. I cannot see the discrepancy between the two tables. They look the same??

 

[coolidge]

Maybe I am missing something from your first post. I cannot see the discrepancy between the two tables. They look the same??

They are exactly the same I don't see any problem.

 

[rwm]

It's the pic. Gear arrangement.

 

[Scott-ak]

it's from the 1440 manual.

Seems many here have never changed the gears on their machines and understand that there is more than just the numbers in the tables.

For what it's worth a 49/120/60, R-W, A-C almost cuts a 1.5mm pitch

 

[B2]

I have the PM1440GT. There are other lathes out there with the number 1440 in the model number, which do not all have the same gear box. I assume you have a PM1440GT if not your gear box may be different. For example the PM1440HT does not have the same gear box.

According to the PM provided manual for the PM1440GT the gear arrangement (see attached):
It shows the Spindle (upper) 30/127/120/60(lower)gear box side, the gear box set at Q-X and A-C multiplier to yield a pitch of exactly 1.5mm/Thread. My spread sheet yields this number. However, there are a few other configurations that will also get you to exactly 1.5mm/thread. There are several that will get approximately there. The following are exact 1.5mm/Th:

30/127/120/60 Q-X , A-C
30/127/120/60 R-Y, A-C
42/127/120/60 Q-W, A-C
XX/127/120/XX Q-X, B-C Here XX means the upper and Low gears are the same. Unfortunately, PM does not supply any duplicate gears.
XX/127/120/XX R-Y, B-C Here XX means the upper and Low gears are the same.
28/127/120/35 Q-Y, B-C
35/127/120/28 R-X, B-C
36/127/120/60 P-Y, B-C
42/127/120/30 Q-W, B-C
49/127/120/28 R-W, B-C
49/127/120/35 Q-W, B-C

When I plug in your description from your last posting "For what it's worth a 49/120/60, R-W, A-C almost cuts a 1.5mm pitch" my spread sheet yields a pitch of 1.48166 mm/Thread. An approximation, but pretty close!

It is my understanding from PM that the factory manuals sometimes has errors in them and so PM discards the manual that comes with the machine but rewrites the manual and supplies this to the customer via download from the PM site.

Dave.

 

[B2]

Hi @Scott-ak

For the PM1440GT owners, I used my Excel Workbook and generated the "massive table" of all of the possible TPI/Feedrates/ (in both Imperial and Metric) using all of the standard gears that come with the machine. It is attached as TPI_PM1440GT OA28_0008.pdf file. I also sorted the rows so that the TPI values are increasing in value. One still needs to check to see if the gear arrangement is physically possible to fit in the space available. At the later parts of this table I put the TPI etc values you would expect to get if you were to use the feed bar to move the saddle rather than the lead screw.

If you are a bit confused about the notation you can look at the spread sheet that was posted and mentioned earlier in this posting thread. The Readme sheet should help. Note that the column titles show the spindle (upper) gear at the right-center and the gear at the gear box (lower gear) at the left-center. The gear box settings are to the left of this. Imperial values on the left and metric values are on the right.

Using the spread sheet macros you can also search this table when in the workbook for exact and/or approximate values as well as automatically generating a table of possible configurations for a standard set (of your choice) of thread values. Of course the pdf file attached is just a text document.

If you scan down column C (TPI) in the table until you reach of TPI value of 16.93333 and then look at the Pitch values at the right side you will see this is the same as 1.50000 mm/Th. You might also note that there are 11 gear configurations available for this exact pitch. I am attaching a screen shot of this area of the table. Note the notation of "S&T" means that the gears at column position S and position T can be a single value. That is, there is no transpose gear pair, just single gear at the transpose axle, Axle A. That is only one gear touches both the upper and lower gear. Also note that there are many other combinations of gears and gear box setting that are very close approximations to the exact 1.50000 value.

I used a more recent version of the workbook macro to generate this TPI_PM1440GT OA28_0008.pdf table. The WorkSheets work the same as what was posted earlier, but this new macro does a better job of removing duplicated entries. I am pretty sure it is working correctly, but it needs further testing. Also, I have considerable clean up work to do on this macro code then I hope to get it posted.

Good Night
Dave