New 1340GT Coming and Need Assistance with VFD

The VFD will actually do a minor amount of braking as coming to a stop by setting the program to do such without a braking resistor. I set mine to decel brake and kept creeping up on the time until it over ramped the current and tripped, then backed it off a bit and it works great. I could install a braking resistor and had thought about it at first but in all honesty it does fine without the braking resistor. Once I turn the rotary switch off, back to the neutral position, the spindle only turns a few revolutions before coming to a stop. It's not like it coasts for four or five seconds.

If you want it to stop faster then by all means you will need to install a braking resistor but there is some controlled deceleration in the VFD alone.

Maybe I look at things differently but the harsher the stops/starts the more wear there will be on the gears overall. I watch these videos and see people stomping on their brakes just to stop the machine during a normal process and have to wonder how much long term wear they are creating. Chances are maybe not enough to measure but then what if there is. I can see using the lathe brake in an emergency situation, doubtful you would be able to react fast enough, but let's say you do, I can see that. I just don't know why for normal machining operations it is needed, same with a braking resistor, probably overkill.

Again, just my opinion, not wanting to start a heated debate over if you need a braking resistor or not. Just my two cents.
 
I know you mentioned foot brake Bill, so I just thought I would again throw my two cents worth in, if it's worth that much.

Foot brakes are good for the reason they give people a sense of safety although it could be a false sense of safety as it is highly unlikely an operator could get to the foot brake before getting caught up in a lathe spindle spinning at several hundred RPM. Once you get caught and sucked in it all happens before you even realize you had an accident.

That said even if pulled in, your body will be thrown off balance and the operator may not be able to stand on one leg to stomp on the brake with the other. Again, these are merely opinions, not based on personal experience nor witnessing of said accidents.

I have been around moving machinery my entire life, between being raised on a farm, working on and around farm equipment and then for the past 26+ years in the industrial maintenance career. We have foot brakes on some of our equipment in the plant and thank God we don't have many industrial accidents but I have never in that 26+ years seen someone get to the foot switch/brake when they themselves have been involved in an accident. The majority of the time(s) it has been a second person hitting an E-Stop that kills the machinery.

All that said, take the foot brake for emergency stopping out of the equation and let's say the operator want to use it for threading or boring up to a shoulder. This is where I see the foot brakes used many times in videos and such. This is definitely a viable option but I think back to my post above about the gears of the machine, again, I may be overthinking the wear aspect, but personally I feel there are other methods of threading or boring up to a shoulder that rely more on planning and execution of a smooth and consistant disengagement of the carriage vs. stomping on the brake.

Again, this is merely my own opinion and I am not trying to offend anyone who feels differently or uses the foot brake for one of the processes that I mentioned above. Just my experience.
 
Also, I don't mean to beat a dead horse but lathe brakes are also not all created equal. While many are mechanically linked to the spindle to stop rotation, there are some that merely drop out the contactor (electrical brake) and therefore do nothing more than the E-stop or switching the rotary switch to neutral.
 
I learned pistolsmithing in my friend's shop where I worked on a rather large Japanese 16x40 lathe (nice lathe too!). And for the most part, the only time I used the footbrake on that lathe was when I was blind ID threading at 40 tpi on compensators. What a way to learn threading eh? :whiteflag:

But with that big set-tru 3 jaw he had on there it would take quite a while for the spindle to stop rotating once power was removed, and even longer when you're working at high (>1600 rpm), so we both tended to lightly press the foot brake just to get things stopped a little quicker so we could take the next measurement. Especially when working to a tight deadline on a customers custom pistol. :)

My usage of the term footbrake was just relating it to the controlled braking of the VFD. If the spindle will stop in 4-5 revolutions I'm good with that.
 
I learned pistolsmithing in my friend's shop where I worked on a rather large Japanese 16x40 lathe (nice lathe too!). And for the most part, the only time I used the footbrake on that lathe was when I was blind ID threading at 40 tpi on compensators. What a way to learn threading eh? :whiteflag:

But with that big set-tru 3 jaw he had on there it would take quite a while for the spindle to stop rotating once power was removed, and even longer when you're working at high (>1600 rpm), so we both tended to lightly press the foot brake just to get things stopped a little quicker so we could take the next measurement. Especially when working to a tight deadline on a customers custom pistol. :)

My usage of the term footbrake was just relating it to the controlled braking of the VFD. If the spindle will stop in 4-5 revolutions I'm good with that.

Matt made the comment to me when I was talking to him about the 1340GT that he had many people decide NOT to purchase that particular lathe merely based on the fact that it did not have a foot brake. I found that sad because it is such a nice machine and the foot brake was not even on the radar for me. I am by no means a "machinist" but I cut my teeth on an older Taiwanese lathe with no footbrake and never really had a need for one. Personally, I am goint to eventually build a toolbox under the center section of mine and remove that filler panel in there as soon as I find time. So a foot brake would impede my ability to do that.

When threading in a blind hole, threading to a shoulder or boring to a shoulder I use my soft stop and merely release the feed when I get to a predermined reading. It is quick, simple and with the nice smooth controls on this lathe it is very easy to hit the target dead on.

I actually did a youtube video a while back demonstrating just how easy and repeatable it is to bore up to a shoulder on the 1340GT. If you get a chance you should check it out. It will also show how smooth and quiet the lathe is.
 
There is probably much more torque/load placed on the gear train from starting a non-VFD motor, then braking. You can always switch in or out the electronic brake or change the VFD parameters as needed, and you can adjust the braking rate to be more linear or S curve. Without the resistor, I had no problems with stopping the lathe in 1-2 seconds, but as the speed increases beyond 800-1000 RPM, there is just to much momentum in the system. I was getting over voltage errors. This will also be affected by the chuck weight and what your milling. Agree with Mike, that in an emergency, by the time you get to the foot brake it is probably too late. That being said, the electronic braking is smooth and quick with a VFD/resistor, and the resistor is a small cost. It also may move some of the heat from regenerative braking away from the VFD to the resistor. Either way, you will have a great set-up. Let us know on what you find with the QMT VFD install, and what they recommend.
 
Never had the time to learn how to use a soft or hard stop, or at least that's my story and I'm sticking to it. :)

I DID get really good at disengaging at the same value on a 2" travel DI though... :lmao:

I don't want a lathe with a foot brake as that means it's larger physically than I want to deal with. The fact that the VFD will assist on ramping down the spindle is just icing on the cake for me. Heck, these smaller 'hobby' lathes aren't spinning that much mass anyway. ;)

Thanks again guys, this is all really good stuff.



Matt made the comment to me when I was talking to him about the 1340GT that he had many people decide NOT to purchase that particular lathe merely based on the fact that it did not have a foot brake. I found that sad because it is such a nice machine and the foot brake was not even on the radar for me. I am by no means a "machinist" but I cut my teeth on an older Taiwanese lathe with no footbrake and never really had a need for one. Personally, I am goint to eventually build a toolbox under the center section of mine and remove that filler panel in there as soon as I find time. So a foot brake would impede my ability to do that.

When threading in a blind hole, threading to a shoulder or boring to a shoulder I use my soft stop and merely release the feed when I get to a predermined reading. It is quick, simple and with the nice smooth controls on this lathe it is very easy to hit the target dead on.

I actually did a youtube video a while back demonstrating just how easy and repeatable it is to bore up to a shoulder on the 1340GT. If you get a chance you should check it out. It will also show how smooth and quiet the lathe is.
 
Never had the time to learn how to use a soft or hard stop, or at least that's my story and I'm sticking to it. :)

I DID get really good at disengaging at the same value on a 2" travel DI though... :lmao:

I don't want a lathe with a foot brake as that means it's larger physically than I want to deal with. The fact that the VFD will assist on ramping down the spindle is just icing on the cake for me. Heck, these smaller 'hobby' lathes aren't spinning that much mass anyway. ;)

Thanks again guys, this is all really good stuff.


Just FYI, what I refer to a soft stop IS a dial indicator that you run the carriage up to a set reading. My lathe came with a hard stop/carriage stop but I don't use it much. I prefer to use a soft stop and use it I do, a lot. I don't know what other people call it but that's what I call it anyways.

I have a writeup on my lathe thread where I show how I fabricated mine and use it. I also have a youtube video as I have had a lot of people inquire about it.

On a side note, I wouldn't necessarily call the 13"x40" lathe a smaller hobby lathe. They are more of an intermediate size. Heck, our 12"x36" in our maintenance shop at work has done pretty much everything we need to do on it. There have been a few things we have had to farm out over the years but the majority of work we do is on that lathe. We used to have an old 16"x60" but it rarely got used because most of the mechanics liked the Norton gearbox on the 12"x36", so when the old 16x60 took a crap we never replaced it. Haven't really missed it.
 
Didn't mean to offend, that was strictly tongue-in-cheek on my part.

Someone here on the board once said 'any lathe with a 14" or smaller swing is basically a hobby lathe'. While I bristled, I kept my mouth shut about it as it was one of the elders here.

I just intended it to cause a chuckle or two... I'll restrain myself from here on. :)
 
Didn't mean to offend, that was strictly tongue-in-cheek on my part.

Someone here on the board once said 'any lathe with a 14" or smaller swing is basically a hobby lathe'. While I bristled, I kept my mouth shut about it as it was one of the elders here.

I just intended it to cause a chuckle or two... I'll restrain myself from here on. :)

Nope, didn't offend. I've got broad shoulders. I just wanted to convey that a 13"x40" isn't exactly a "hobby" machine based on it's size. Many toolroom professional lathes are smaller than that.
 
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