Pm1340gt Lathe Basic Vfd Control Conversion Using The Stock Control Board And Switches

[B2]

Thanks David. Nice. That helps me understand a lot better. There is a lot more room for the wires to come thru in the 1340 than in the 1440. The oiling system is not a great factory design, but you seemed to have a nice fixed for it as well as that nice drip pan you made! It is not clear what holds the drip plate in place.... just the two front panel mounting screws? The 1440 has a reservoir and so does not consume oil or drip it out the bottom. Do I understand correctly that drip plate siting on flat surfaces is all that keeps the oil from getting into the electronics enclosure. No o-rings or gaskets!

I understand you why dimpled down the plate surface you made due to the front panel being at an angle and panel mounted devices possibly bottoming out. However, it appears that you mounted the devices up high enough to avoid needing it. In the 1440 the panel is vertical, but there is also a ~1" hollow area in the enclosure extending down from the bottom edge of the front panel the provides extra space. Although I did not need it, I used just a little of it for the bulky part of the E-Stop switch. Nevertheless, the wires lay on the bottom.

The depth is a little hard to judge, but from the photo of the cavity with the new oil drip pan plus the drawing of your new oil drip pan would indicate that the depth is about 3.4". The height is not as large as the panel due to the oil drip pan.

Great to see those lovely Norton Gears!

Dave L.

 

[B2]

Hi @davidpbest

When you were refinishing your PM1340GT did you by chance take the apron gear box apart. If so did the gear arrangement look any thing like the manual shows? It appears to be similar to my 1440GT but I cannot figure out how the gears work in it. The manual is very poor, but at least it give some of the gear dimensions. The 1340 does not seem to even do that.

So here is the reason for the question. On both machines and many others it says that the ratio between the Power Feed and the X-Feed rates are simply 2:1 (or 1/2) however, I have made a quick attempt to measure them and I get a number more like 3.14:1 not the factor of 2. I think the tables on the lathes are wrong and miss leading. Most folks could not care, but still.... I am going to measure mine much more accurately and see exactly what the Power Feed and the X-feed rates are. I think the lathe table for The power feed is somewhat close. But not the X-feed.

I wonder how many other lathes are like this?

Maybe I should take this to another string and ask the general question about x-feed rates.

 

[Firstram]

Easy enough to measure. Engage the x feed and turn the spindle over by hand a few turns to take up any backlash. Zero a dial indicator on the tool post, rotate the spindle 10x and read the travel. Divide by 10 to get .xxx/Rev. Repeat the process to get the travel numbers, compare with the stated travel for the feed you chose.

 

[B2]

Hi @Firstram

Thanks. Yes, I have measured them that way as well as with far more turns on the spindle to get more accurate results. The end summary is that the table values in the manual for the Power Feed are not too bad, but not exact. However the x-Feed Table values are way off. Typically rather than the ratio of 1/2 of the Power Feed values which the tables on the lathe as well as in the manual say. The measured results are more like 1/3.xxx. So I want to know what is going on inside the gear box that is different from what the manual says. The manual's description of the gears is incomplete at best. In the end of course I will go with what I measure, and if I do not figure out the gears then it will just have to wait until SOME day when I or someone else take the apron apart and describes it better than the manual. By the way, the manual's description of the main gear box is also poor and incomplete and after a lot of study I concluded it could not work with the geometry that was described in the manual. It is not nearly as straight forward to analyze as a Norton gear box.

I have a unique instrument for this measurement. I have an electronic counter to count the spindle turns to 0.1 of a turn. I also have a good magnetic DRO which I have checked the calibration in both directions. So I can run the spindle for a long time and just get the turns on the counter. I should be able to find both feed rates rather accurately. Here is the counter I built in...

I was adding a counter to my VFD converted PM1440GT

Dave L.

 

[Provincial]

Dave, on my Metal Max MM-1340LB (China-made Jet/Enco belt drive clone) the manual states that the carriage feed rates are 0.0036-0.1005 and the cross-feed rates are 0.0012-0.0345. That is pretty close to 1/3. I believe that all the gears in the apron have the number of teeth listed except the one on the end of the carriage feed handwheel, but that gear is not in the power train of the powered feed. They also don't call out the tooth count on the cross-slide feed screw. I can take photos of the manual pages and post them if you desire.

Very nice conversion! I am envious. I have all manual equipment, but am converting to DRO's and VFD's.

 

[Provincial]

Rather than clutter this thread, I posted the photos on B2's thread about the cross-travel speeds linked here:

https://www.hobby-machinist.com/threads/x-feed-rates-on-pm-lathes.98071/