Pricing strategies are interesting. For 14x40 shipping from Grizzly/PM is ~ $400-500. For KENT - it's 1500. Even though they won't charge sales tax it's still a lot. Most likely PM/Grizzly subsidize those. Had to, since even LTL would be different price depending on distance.
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Basement shop equipment suggestions needed
- Thread starter katit
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That's interesting. It should condition the air and remove the humidity. I have one that was installed in an large apartment above a garage which cools and heats well.(18,000 BTU). Also a newer one in my finished basement,(800 sq ft). Works so well I no longer have to run the dehumidifier. Each year they have become more efficient.
Oh, almost forgot. Most of the newer ones have a "Dry" mode. I use that when not using the space for longer periods.
I have never spent much time thinking about what external and internal gears one might need to build a metric lathe. A 2mm/thread lead screw in TPI is 25.4/2 =12.7 TPI. So it would appear that the lead screw is just playing the role of the 127 tooth transpose gear. My PM1440GT normally comes with a 8TPI lead screw.
The Standard Metric thread values are: 6., 5.5, 5.0, 4.5, 4.0, 3.50, 3.00, 2.5, 2.00, 1.75, 1.50, 1.250, 1.00, 0.80, 0.75, 0.70, 0.60, 0.50, 0.450, 0.40, 0.35, 0.25, 0.2 .
Since the Imperial to Metric Transpose gears are normally 120/127 and the new lead screw TPI is just 127/10 this would imply that if the lead screw were changed to 12.7 TPI (2mm/thread) and the transpose gear was changed from 127 to 80. It would be the same as moving the 8TPI lead screw count to the transpose position. However, the 120 portion of the transpose gears is too large to cover the standard metric thread value. It should be change to 60 rather than 120. This introduces a factor of 2 in the string of gear ratios being multiplied out.
So in my Excel worksheet I changed the set up of the PM1440GT to have a lead screw pitch of 2mm/thread (12.7TPI). Then I changed the Transpose gears to 60/80 rather than 120/127. Then I ran the program using the standard set of PM1440GT external gears. I did not check to see if all of the external gears were required, but with this arrangement all of the standard metric threads are possible. The largest Pitch that resulted was 24.64286mm/thread (1.03072 TPI), which would probably never be used. The smallest pitch that resulted was 0.17391mm/thread(146.0526 TPI), which would probably never be used either. However, it is obvious then that rather than using 60/80 as the exchange gear one could use 30/80 or even 15/80 which result in lower pitch values by factors of 2 or 4 respectively. There is probably little value in this except that it would probably result in more possible gear combinations of achieveing the 0.2 pitch.
A list of the lathe settings to obtain the EXACT standard metric Pitchs is attached. Note the pitch values are highlighted. There are far many which are close approximations to the exact values. This was done twice. Once for the 60/80 transpose ratio and once for the 30/80 ratio. Note in the table when the notation is Letter&Letter, such as N&S this means the gear at the excel columns N&S can be any value that is the same for both columns. In the case of N&S the S value is 60 in one file and 30 in the other file.
My conclusion is that by changing the lead screw to 2mm/thread and replacing the exchange gear's ratio to 60/80 or 30/80 or 15/80 one can generate all of the standard metric pitches using the Standard PM1440GT gear box and supplied external gears. One gets multiple possible gear and lever arrangements to achieve each the standard metric threads.
Dave L.
PS. An eariler version of my Excel workbook is at:
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@WobblyHand I do not consider the thread dial in my workbook. So I guess I am assuming that the 1/2 nut is always engaged. I quit using the thread dial as I use my proximity stop and just leave the 1/2 nut engaged. Anyway, if you change the lead screw you have to change out the 1/2 nut and probably the thread dial as well. My thread dial engages directly to the lead screw so it does seem you would always have to change it. I am not positive, but I think the X-feed engages to my feed bar and not the lead screw, but for many lathes there is no feed bar so that would mean other gearing in the saddle might also have to change to mesh with the metric lead screw TPI.
I have the factory manual for my 1236T, I’m not sure how accurate this is since the change gears listed for the inch version are not the same as the thread chart on mine. The metric version is listed using a 4mm leadscrew. The gears in the gearbox are different between the inch and metric versions, but it still has the 120/127 gear so that it can cut inch threads. In both versions, both change gears are on the same bull gear, but the gears in the gearbox are different to give the proper threads.
The thread dial uses an 18 tooth gear for most thread pitches, for 1.25, 2.5, and 5 it needs a 20 tooth gear, for 0.7, 1.75, 3.5 and 7, it needs a 21 tooth gear.
The thread dial uses an 18 tooth gear for most thread pitches, for 1.25, 2.5, and 5 it needs a 20 tooth gear, for 0.7, 1.75, 3.5 and 7, it needs a 21 tooth gear.
Interesting. So the metric lathe uses the same Transpose 120/127 ratio to get back to imperial threads. Makes perfect sense. I suppose the gear is just flipped over so in the case of an Imperial lathe where the lead screw is imperial (8TPI or 16TPI) the 127 touches the lower gear while in the Metric lathe where the lead screw is 2 or 4mm/thread then to produce Imperial threads one moves the 127 gear to touch the touch the upper lathe gear!
In other words, for these lathes, when one wants metric one needs a 127 in the numerator of the gear ratio products. It can come about either by the Lead screw or by putting in the Transpose axle position. When one wants Imperial threads one cancels out the 127 value of the product of ratios. Fundamentally, in terms of gear ratios, there is no difference between an Imperial and a Metric lathe other than the lead screw. The gear box or other external gears simply change the magnitude of the over all TPI or Pitch a bit. Of course the components such as the thread dial etc have to be changed.
If you look at the lathe sheets of my work book you will see the gear box lever generated ratios. At lease for the 1440, these are simple ratios of two numbers. For example, when you set the first lever to T, the ratio produced at this point is 0.818181818181818 which = 27/33. Similarly for all of the other lever positions the generated ratio is just the ratio of two number. These then represent the two value of the gear teeth in the gear box for this lever position. These gears could be at external positions as well when a different set of gears are at the gear box.
The same is true if you look at the sheet for the PM1236T (which is the same as the PM1340GT). They have Norton gear boxes. If you look at the lever position TWO you see a ratio of 0.5625 = 4.5/8 = 9/16 = 18/32. So, when the external gears yield a ratio of one then the 4.5/8 * Leadscrew TPI (8) yields the standard TPI value of 4.5.
Dave L.
I think in the factory manual they just used the wrong image for the inch threading chart since the metric chart for the imperial leadscrew matches whats on my machine, and that would not be possible unless the image is wrong.
This is the metric machine chart
This is the metric machine chart
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