Expectations of Chinese Lathes 12 x 36 or smaller vs. Taiwan units

[Aaron_W]

Just got me to thinking: I wonder where the Grizzly G4003 fits compared to the PM 1236 and 1236T?

I was just looking at that, Grizzly has 4 12x36(35)" lathes that pretty well straddles the price range between the 1236 and 1236T, from $4700 for the G4003 to $7400 for the Shop Fox M1112.

 

[Aaron_W]

My admittedly shallow research on the G4003 indicates mostly favorable reviews. YMMV.

Never really gave any thought to the whole documentation issue, and now I understand why Grizzly emphasizes, "The XXXXX manual was written by our U.S.-based Documentation Department and is packed with useful information. The complete and easy-to-read manual makes it easier to assemble and maintain your lathe" in all its lathe descriptions. I am a documentation hound, so this could be a big deal to me.

One more thing, can someone help clear up a bit of confusion on my part - change gears and back gears. Change gearing allows for greater variation in threading capabilities, right? So a lathe with a QCGB will not require a separate set of change gears - correct? And back gearing (or changes thereof) allows for variation in spindle speed, but having a variable-speed motor on the lathe would eliminate the need for back gears? Is that about right?

Thanks again.

Think of back gears as low range in a 4x4. They are essentially a transfer case that when engaged drops the entire gear range by the ratio, so a lathe with 8 speeds, will have 16 speeds (8 high, 8 low) if it has back gears.

Because of the way back gears work, they provide high torque at low speeds, like a 4x4. A common complaint with variable speed is they can result in low power at low speeds. You look at the PM1236, it has 18 speeds from 65-1800rpm, a Craftsman 12" (which has backgears) was a budget lathe in its day but it has 16 speeds from 28-2072rpm. Variable speed lathes will sometime show very low speeds (some even zero) but in practice most have an effective low speed more like 80-100rpm, and some more like 200rpm. Slow speeds are nice for threading as it gives good control when you are working up close to the chuck.

Change gears are literally changing the gears on the lathe. You get a set of gears and you have to put a specific combination on the lathe.
Quick Change Gear Box allows you to change settings internally (don't have to swap gears around), using a levers or knobs.

Gears are used to control power feed speeds and for single point threading.

There is a grey area between change gear lathes and quick change gear boxes. A lot of the current 9-11" lathes do have a quick change gear box, but can only do a handful of threads on a set of gears, so in effect they are change gear lathes, since the odds are high to do a specific thread you will need to change the gears. These gear boxes are intended to allow easy adjustment of the power feed speeds, not really for threading, although on a specific set of gears you can probably do a handful of threads without changing the gears around.

A proper quick change gear box will allow a large range of threads to be done, just by changing the position of the knobs / levers. Many QCGBs do require the use of change gears to switch between metric and inch threads, but some better quality gear boxes will even allow this without having to muck about with change gears. Many people do not have a huge issue with needing to switch between metric and inch, since it seems most tend to work in one system or the other.

 

[Ischgl99]

On the 1236T and probably most others in this price range, the lower speed range is done by changing the v-belt position on the motor and input pulley. Something that has a back gear that can be actuated by a lever would be much nicer to use. I bought a three phase machine so that I can get the lower speeds by just changing the motor speed with a VFD. My v-belt is kept on the high speed range, slowing the motor to half speed gives me the low speed range shown on the front chart, but at the expense of half the horsepower and half the torque of switching from the high speed position to the low speed position on the pulley.

 

[Larry$]

My lathe has a wide selection of spindle speeds by levers on the head stock, plenty for my use.
The QCGB has a wide selection of SAE feed rates for about anything I've wanted.
BUT to do metric threads I have to change the 100/127 gear position manually. In addition I have to change one or two of the driven gears to get the metric thread I want in conjunction with the QCGB. Changing gears doesn't take all that long but is a greasy mess. As long as I stick to SAE thread pitches I don't need to touch the gears.
I use my lathe for repair work, so encountering metric threads is fairly common. Life would be much better if Congress had stuck to going metric back in the '70s. I prefer working in metric because it is a more logical system. Why are we still stuck with having to use two systems 50 years later?

 

[verbotenwhisky]

My lathe has a wide selection of spindle speeds by levers on the head stock, plenty for my use.
The QCGB has a wide selection of SAE feed rates for about anything I've wanted.
BUT to do metric threads I have to change the 100/127 gear position manually. In addition I have to change one or two of the driven gears to get the metric thread I want in conjunction with the QCGB. Changing gears doesn't take all that long but is a greasy mess. As long as I stick to SAE thread pitches I don't need to touch the gears.
I use my lathe for repair work, so encountering metric threads is fairly common. Life would be much better if Congress had stuck to going metric back in the '70s. I prefer working in metric because it is a more logical system. Why are we still stuck with having to use two systems 50 years later?

Exactly, its a threading gear box not back gears, a term I have issues with because I see it used several ways regardless of actual meaning.

It would be nice if the threading gear box did both but I would settle for your arrangement over swapping all the gears around all the time which is my only concern with the lathe I have which isn't a problem as it is operating as designed and not the only machine designed that way.

I do not care so much about metric vs imperial as I have reached the point where I can go back and forth in my head.

 

[coolidge]

My admittedly shallow research on the G4003 indicates mostly favorable reviews. YMMV.

Never really gave any thought to the whole documentation issue, and now I understand why Grizzly emphasizes, "The XXXXX manual was written by our U.S.-based Documentation Department and is packed with useful information. The complete and easy-to-read manual makes it easier to assemble and maintain your lathe" in all its lathe descriptions. I am a documentation hound, so this could be a big deal to me.

One more thing, can someone help clear up a bit of confusion on my part - change gears and back gears. Change gearing allows for greater variation in threading capabilities, right? So a lathe with a QCGB will not require a separate set of change gears - correct? And back gearing (or changes thereof) allows for variation in spindle speed, but having a variable-speed motor on the lathe would eliminate the need for back gears? Is that about right?

Thanks again.

Not correct, a QCGB can reduce the number of change gears and how often you need to swap those gears around to cover all the threads and feeds a lathe supports. But it's rare that a QCGB can cover 100% of the threads and feeds without changing any gears. I think I came across a single lathe that can do that but your talking a $25k lathe. Note also feeds, the QCGB and gear configuration is also about covering the full range of feed rates a lathe supports not just the range of threads.

A great example of two quick change gear boxes are the Grizzly G0709 and the G0824....

G0709 - has only 5 change gears. Only 3 of those ever need to be changed to cover the entire thread/feed range. And there are only 3 configurations total hence the factory configuration covers a lot of the most common threads and feeds without having to swap change gears at all. Also, all the change gears are installed on the machine. You don't have a stack of extra change gears to store on shelf.

G0824 - has a whopping 9 change gears and complaints by people who bought the thing not knowing what a pain it was going to be having to swap change gears all the time. I'll let you read up on the G0824 if you want more details.

Grizzly has very detailed manuals, specifications sheets, and parts lists. Everything on the lathe has a part # down to screws and bolts which you can search for on their website to see if it's in stock. I purchased a number of spare parts for my lathe straight away. Two of the lead screw brass shear pins for example because shearing one of those and not having a replacement on hand in the middle of a job blows. Headstock cover gasket because freaking leaks. Extra brass thread dial gear etc. ALSO if there's one thing that would put me in a bad mood is having to wait months for a spare/replacement part to arrive from China. Grizzly's USA part supply was also a factor in my decision. I can't speak for PM's spare parts supply but a lot of these other machine sellers just sell the machines, they don't maintain spare parts inventories.

Variable speed vs fixed speeds vs back gears - Starting with back gears PM lathes with high and low belt pulleys does double the number of fixed speeds. For example my G0709 has 8 spindle speeds. If it had the high and low motor pulleys (back gears) I'd have 16 spindle speeds and if I remember correctly some of the PM lathes have exactly that so advantage PM. That said a lathe is not a mill. Mills have spindle speeds from 50 to 30,000 RPM's. Lathes are a completely different animal. I discussed variable speeds with my brother before purchasing. He owned a $250,000 Mori CNC lathe and never exceeded 2,000 rpms. Different feed rates sure, but you don't need infinitely variable spindle speeds really. It can help in certain situations, tweaking to eliminate/reduce chatter (squealing) for example. Typically variable speed lathes use 3 phase motors which run smoother vs single phase motors which can produce finish issues. But there are other methods for dealing with chatter. Isolating the single phase motor from the lathe completely. Larger shank tools. Smaller radius tool tips etc. If money were no object I might have opted for variable speed but honestly the 8 speeds the lathe has pretty much covers anything I would do so I spent the variable speed money on tooling and chucks instead.

 

[verbotenwhisky]

Not correct, a QCGB can reduce the number of change gears and how often you need to swap those gears around to cover all the threads and feeds a lathe supports. But it's rare that a QCGB can cover 100% of the threads and feeds without changing any gears. I think I came across a single lathe that can do that but your talking a $25k lathe. Note also feeds, the QCGB and gear configuration is also about covering the full range of feed rates a lathe supports not just the range of threads.

A great example of two quick change gear boxes are the Grizzly G0709 and the G0824....

G0709 - has only 5 change gears. Only 3 of those ever need to be changed to cover the entire thread/feed range. And there are only 3 configurations total hence the factory configuration covers a lot of the most common threads and feeds without having to swap change gears at all. Also, all the change gears are installed on the machine. You don't have a stack of extra change gears to store on shelf.

G0824 - has a whopping 9 change gears and complaints by people who bought the thing not knowing what a pain it was going to be having to swap change gears all the time. I'll let you read up on the G0824 if you want more details.

Grizzly has very detailed manuals, specifications sheets, and parts lists. Everything on the lathe has a part # down to screws and bolts which you can search for on their website to see if it's in stock. I purchased a number of spare parts for my lathe straight away. Two of the lead screw brass shear pins for example because shearing one of those and not having a replacement on hand in the middle of a job blows. Headstock cover gasket because freaking leaks. Extra brass thread dial gear etc. ALSO if there's one thing that would put me in a bad mood is having to wait months for a spare/replacement part to arrive from China. Grizzly's USA part supply was also a factor in my decision. I can't speak for PM's spare parts supply but a lot of these other machine sellers just sell the machines, they don't maintain spare parts inventories.

Variable speed vs fixed speeds vs back gears - Starting with back gears PM lathes with high and low belt pulleys does double the number of fixed speeds. For example my G0709 has 8 spindle speeds. If it had the high and low motor pulleys (back gears) I'd have 16 spindle speeds and if I remember correctly some of the PM lathes have exactly that so advantage PM. That said a lathe is not a mill. Mills have spindle speeds from 50 to 30,000 RPM's. Lathes are a completely different animal. I discussed variable speeds with my brother before purchasing. He owned a $250,000 Mori CNC lathe and never exceeded 2,000 rpms. Different feed rates sure, but you don't need infinitely variable spindle speeds really. It can help in certain situations, tweaking to eliminate/reduce chatter (squealing) for example. Typically variable speed lathes use 3 phase motors which run smoother vs single phase motors which can produce finish issues. But there are other methods for dealing with chatter. Isolating the single phase motor from the lathe completely. Larger shank tools. Smaller radius tool tips etc. If money were no object I might have opted for variable speed but honestly the 8 speeds the lathe has pretty much covers anything I would do so I spent the variable speed money on tooling and chucks instead.

For the most part I agree with your assessment. There are three reasons I would choose PM over Grizzly (Keep in mind I own some Grizzly machines, Just not the metal Lathe and mill) I find that PM's customer service is better and their tech support is much better should you need to ask questions and although many of the machines are the same there are little differences such as the imperial lead screws PM orders their machines with.

My wife has the Grizzly G0969 Scroll Saw and we have the shop fox W1852 wood lathe which was the Taiwanese version of the G0766. We have called Grizzly to ask question and it is difficult to find an individual versed in any specific piece of equipment. I find the PM Manuals to be decent and complete with very good illustrations and parts list, which you can download from their site prior to purchase.

As it concerns the PM-1236, it has 2 belt drive positions, high and low which drive the gear box, it is a gear head lathe, not a variable speed.

 

[Aaron_W]

Exactly, its a threading gear box not back gears, a term I have issues with because I see it used several ways regardless of actual meaning.

It would be nice if the threading gear box did both but I would settle for your arrangement over swapping all the gears around all the time which is my only concern with the lathe I have which isn't a problem as it is operating as designed and not the only machine designed that way.

I do not care so much about metric vs imperial as I have reached the point where I can go back and forth in my head.

It is not just a threading gear box, it also controls the speed of the power feed. In fact that is the primary purpose for the gear box on many small lathes. Back gears are an entirely independent system, many lathes like my little 6x18 Craftsman have no gear box but they do have back gears.


As far as Metric I was in 2nd grade in 1976, so I learned both systems, and can easily use both. I view them as a language, no different than speaking English and Spanish (or German, French etc). I like old stuff, so I will never not have a need for US Customary units. I will always need a set of both SAE and Metric sockets.

 

[verbotenwhisky]

It is not just a threading gear box, it also controls the speed of the power feed. In fact that is the primary purpose for the gear box on many small lathes. Back gears are an entirely independent system, many lathes like my little 6x18 Craftsman have no gear box but they do have back gears.


As far as Metric I was in 2nd grade in 1976, so I learned both systems, and can easily use both. I view them as a language, no different than speaking English and Spanish (or German, French etc). I like old stuff, so I will never not have a need for US Customary units. I will always need a set of both SAE and Metric sockets.

Second grade in 1976? yer a young feller.... Sorry I had to say it... LOL there are so many guys here older than me with much wisdom...

 

[verbotenwhisky]

It is not just a threading gear box, it also controls the speed of the power feed. In fact that is the primary purpose for the gear box on many small lathes. Back gears are an entirely independent system, many lathes like my little 6x18 Craftsman have no gear box but they do have back gears.


As far as Metric I was in 2nd grade in 1976, so I learned both systems, and can easily use both. I view them as a language, no different than speaking English and Spanish (or German, French etc). I like old stuff, so I will never not have a need for US Customary units. I will always need a set of both SAE and Metric sockets.

If you look at the picture of mine the 4 knobs on the bottom are in a separate small gear box. 2 on the left shift gears (feed speed), top right selects the drive shaft or lead screw and the bottom right is a high/low gearing. In addition to this box which does 90% of the work, there are a set of change gears with the 120 to 127 idlers in the cabinet to the left behind the labels; you have to line-up the correct gears when threading, other wise for feed there are 2 standard gears I default to which do everything I need to do; other than threading....