Jet 1221 RPMs Slowing When Drilling

[TonyL]

I am going to call Jet tomorrow (assuming they are open) and ask about this. Possibly my belt is slipping but I don't really see any signs of this. It appears that the motor is having troubling overcoming the resistance of large drill bitts (Forstner sp? 7/8) and some half inch regular bits.

Anyone experience this? It happens mostly when drilling 2" square bottle stopper wooden blanks. Nothing that dense. I drilled just about everything with this and only started having a "problem" the last few times.

This is 2 years old but seldom used until recently. My 4 year old 1221 is still going strong as is my 1015.

Thanks for reading.

 

[jttheclockman]

I am going to call Jet tomorrow (assuming they are open) and ask about this. Possibly my belt is slipping but I don't really see any signs of this. It appears that the motor is having troubling overcoming the resistance of large drill bitts (Forstner sp? 7/8) and some half inch regular bits.

Anyone experience this? It happens mostly when drilling 2" square bottle stopper wooden blanks. Nothing that dense. I drilled just about everything with this and only started having a "problem" the last few times.

This is 2 years old but seldom used until recently. My 4 year old 1221 is still going strong as is my 1015.

Thanks for reading.

So are you saying you have two 1221 jet lathes and one is giving you problems??

I would check all the obvious points such as loose belt, loose pulley, blow out dust from the controller. Make sure the motor is locked down if belt was moved. Is the bit sharp?? Is it VS and does it happen on all speeds of the VS if it is?? If it does then it would be in the controller.

 

[robutacion]

I am going to call Jet tomorrow (assuming they are open) and ask about this. Possibly my belt is slipping but I don't really see any signs of this. It appears that the motor is having troubling overcoming the resistance of large drill bitts (Forstner sp? 7/8) and some half inch regular bits.

Anyone experience this? It happens mostly when drilling 2" square bottle stopper wooden blanks. Nothing that dense. I drilled just about everything with this and only started having a "problem" the last few times.

This is 2 years old but seldom used until recently. My 4 year old 1221 is still going strong as is my 1015.

Thanks for reading.

I had a case recently with the motor of my bandsaw losing power considerably and no torque, I've thought the motor was done (done a lot of work in 7 years) so I spoke with an electrician that specialises in these type of things and he asked me to send the motor to him as he wanted to check it out before ordering a new one.

Well, it happens that we are used to believing that the capacitors do either work or they don't, but they can become weak/faulty and prevent the motor from reaching its capabilities even though it starts the motor so, a new capacitor and I was back to normal, saving me hundreds...!

Cheers
George

 

[TonyL]

Excellent ideas! I will try the suggested actions. I did not blow-out dust from the controller.
Belt is tight (that was actually what I inspected first), tools sharp motor locked, etc?


Yes, I have two 1221 EVS. The newer and less frequently used one is experiencing the problem. And it happens at all speeds.

Thank you both.

 

[RobS]

If it is new, I would call Jet, their customer service was awesome when I called them last year. They might be able to send you the part needed.

RobS

 

[TonyL]

Thank you. I called them and they said, my bits may be dull AND it is common for this to happen when one is using the high speed belt pulley for materials that require more torque. He recommended that I change belt pulleys.

I will give all a try.

Thanks again.

 

[Charlie_W]

Tony, as you try both 12/21 Jets, are they being plugged into the same receptacle for each of your tests?
Is your belt seated properly on both pulleys....on both machines?

 

[TonyL]

Yes...but, please think of anything else. Thank you Charlie.

 

[KenB259]

When you are using large bits it is imperative that you change the belts to the slowest setting. You cannot just lower the speed via the variable speed knob. There is a reason there are three belt positions.


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[MRDucks2]

When you are using large bits it is imperative that you change the belts to the slowest setting. You cannot just lower the speed via the variable speed knob. There is a reason there are three belt positions.


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Ken is on the right path, torque is inversely proportional to speed. As such, if you use the larger bits and do not use a slower settings it can begin to bog down. IF nothing else is wrong, the difference between the older and the newer model may simply be the motor supplied with each. A motor that breaks over the torque curve more quickly is cheaper to make than one that has a longer period before the break.

In reality, on motors as cheap as are being made these days, it could be the difference in losses between two motors that are supposed to the same. If this is the case, you should notice that the motor that is bogging down is getting hotter, quicker than the one that is not. Motor losses result in heat.

 

[TonyL]

Thank you. That is what the Jet technician said. I only started turning BS's a little while ago and never had the experience. I learned something today; I always wondered about the 3 belts when the fastest one covered all the speed ranges (he said the lower speeds have more torque). Thanks again. Going to give things a try tonight.

 

[KenB259]

I learned it the same as you. The first time I tried drilling with a larger Forster bit, my Jet did the same as yours. Changed the belt locations and the problems disappeared.


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[jttheclockman]

Those by any means are not big drill bits. I drill with the belt on the middle pulley and have not changed it since I owned it and drill just fine and use 1" and larger bits when I drill billiard balls out or making birdhouse ornaments and do it on a 1014 Jet. Sharp bits a key and do not force the bit.

 

[KenB259]

I was referring to my experience, sorry I should have explained that better, I was using a bit that was 2 3/8.


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[jttheclockman]

Tony said he is using 1/2" and 7/8" bits. Those are pen size drill bits at times. That is not large at all and there should be no torque problem drilling those. Just like drill bits you need to keep the hole cleared out.

 

[KenB259]

Tony said he is using 1/2" and 7/8" bits. Those are pen size drill bits at times. That is not large at all and there should be no torque problem drilling those. Just like drill bits you need to keep the hole cleared out.

I wouldn't consider a 7/8 forstner bit small, especially in hardwood. The recommended speed for that size in hardwood is only 500 rpm. You won't get much torque at that speed with a high belt ratio setting.


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[Dehn0045]

My understanding is that variable speed lathe motors work by changing the frequency of electricity going to the motor. At half of the max speed the frequency is 30 Hz rather than 60. This basically means less juice is going to the motor and therefore less torque. By changing the pulleys you can achieve the same speed at a higher frequency going to the motor, so more juice and more torque. In my experience electric motors die relatively fast deaths, if it is the motor failing then I'd bet it will stop working altogether sooner rather than later.

Just my 2 cents. Please correct me if I am wrong about the VFD stuff...

 

[Charlie_W]

I recall years ago someone saying that DC motors will loose some of their uumph over time. Could have been an old auto mechanic referencing starter motors, wiper motors,etc.
I don't know if this is applicable to our modern electronic variable speed motors of this size ( mini lathe) or not.......just a thought......I like having those every now and then :biggrin:

 

[TonyL]

Well, I changed the belt pulleys and worked like a charm. Thanks to all for filling-in my inexperience. Couldn't have done it without your collective input. Much thanks!

 

[jttheclockman]

Well, I changed the belt pulleys and worked like a charm. Thanks to all for filling-in my inexperience. Couldn't have done it without your collective input. Much thanks!

Can I ask what pulley were you using and what pulley did you change over to??

I will not go into the whole motor thing here.

I also could ask how many people change belts on their drill presses and follow recommended speeds. Just saying. :wink::wink::wink::wink:

 

[jttheclockman]

My understanding is that variable speed lathe motors work by changing the frequency of electricity going to the motor. At half of the max speed the frequency is 30 Hz rather than 60. This basically means less juice is going to the motor and therefore less torque. By changing the pulleys you can achieve the same speed at a higher frequency going to the motor, so more juice and more torque. In my experience electric motors die relatively fast deaths, if it is the motor failing then I'd bet it will stop working altogether sooner rather than later.

Just my 2 cents. Please correct me if I am wrong about the VFD stuff...

Not on these type lathes.

 

[TonyL]

Sure. I have always used the fastest 200 to 3500 I believe. I always wondered what the others were for... if there was one pulley range that included the RPMS. Up until a short while ago, I really only made pens (I made less than 5 BSs, but tap them myself). Now I started making more and using a Forstner bit and 1/2" drill to fit a brass, threaded fitting.

 

[jttheclockman]

Tony

This may interest you even though I believe it is in your instruction booklet but it shows the speeds of the belt pulleys and yes the smaller the pulley the more torque but the speed will also compensate for this within the range.



www.manualslib.com/manual/79877/Jet-Jwl-1220vs.html

 

[Dehn0045]

Not on these type lathes.

Thanks JT, I was dead wrong. Looks like the 1221-evs has a DC motor. The manual for the 1221-evs talks about cleaning the motor's brushes, might be something to look at. I know less about DC motors than I do about AC (which clearly is very little), so I will stop there.

Not really relevant to this discussion, but b/c I can't edit my previous post - it seems that a VFD should actually be able to produce constant torque at low speeds. However, this is a pretty complicated issue that depends on the specifics of the VFD and motor. It looks like some higher end wood lathes incorporate VFD.

 

[jttheclockman]

Not on these type lathes.

Thanks JT, I was dead wrong. Looks like the 1221-evs has a DC motor. The manual for the 1221-evs talks about cleaning the motor's brushes, might be something to look at. I know less about DC motors than I do about AC (which clearly is very little), so I will stop there.

Not really relevant to this discussion, but b/c I can't edit my previous post - it seems that a VFD should actually be able to produce constant torque at low speeds. However, this is a pretty complicated issue that depends on the specifics of the VFD and motor. It looks like some higher end wood lathes incorporate VFD.

The Nova line has them.

Boy one of my last jobs (and this is getting off base here) I was part of a team that must have installed over 200 VFD controls for the air handling systems for a Nova Nordisk project. Same basis but a lot larger scale:biggrin::biggrin::biggrin:

 

[monophoto]

My understanding is that variable speed lathe motors work by changing the frequency of electricity going to the motor. At half of the max speed the frequency is 30 Hz rather than 60. This basically means less juice is going to the motor and therefore less torque. By changing the pulleys you can achieve the same speed at a higher frequency going to the motor, so more juice and more torque.

Some misinformation here. Most low-end electronic variable speed lathes have a DC motor, and variable speed is achieved by varying the magnitude of the DC voltage applied to the motor. Torque varies with voltage, so as the voltage is reduced, the amount of torque that the motor can produce is also reduced. If there are pulleys, you can switch to a lower ratio which means that the voltage reduction required to reach a desired low speed will be less than with a higher pulley ratio. That means that in general, you will have better low-speed torque performance when using a lower pulley ratio compared with a higher pulley ratio.

There are some lathes (mostly higher end) that use variable frequency drives in which the motor is an AC motor where the speed is a function of the frequency of the applied AC voltage.

In my experience electric motors die relatively fast deaths, if it is the motor failing then I'd bet it will stop working altogether sooner rather than later.

I don't agree with that statement. Good motors can last essentially forever if they are applied within their ratings and if they are properly cared for.

The key is in applying the motor within its ratings - attempting to operate a motor beyond its ratings results in heating that will lead to premature failure. A fairly common problem today is that motors are marginally applied - primarily because the manufacturer of the motor exaggerates the ratings with the result that motors are often too small for the application.

 

[Dehn0045]

Louie, thanks for correcting me, after a little research I realized my misunderstanding but was not able to edit my post.

With respect to motor failure, my original comment was with respect to AC motors, not really relevant in this situation. What I meant was that AC motor failures tend to be catastrophic, you don't often see an AC motor "going bad". When they die, they die fast. I agree that motors can last an incredibly long time with proper care and use. Just my personal experience, so very limited sample size. DC motors are a different beast.

 

[TonyL]

Thanks to all of the above. I certainly learned a lot and, apparently, solved my problem.

you will have better low-speed torque performance when using a lower pulley ratio compared with a higher pulley ratio.

Louie...Thank you. So do you believe that I got the right advice from the Jet technician? He said that changing the pulleys to the slower pair (of pulleys) would provide me with more torque. I want to ensure that I am not imagining a "fix" or overlooking a lathe malfunction. Thank you!

 

[monophoto]

So do you believe that I got the right advice from the Jet technician? He said that changing the pulleys to the slower pair (of pulleys) would provide me with more torque. I want to ensure that I am not imagining a "fix" or overlooking a lathe malfunction.

Yes - that does sound correct.

And as others have surmised, I suspect that the problem you have had is simply that you are drilling in end grain with a large bit, and the additional torque burden is what is causing your lathe to slow down. That's something that I encounter a lot.

I know others have said that a 7/8" forstner is not a 'large bit', but I disagree. You can't really compare a forstner bit with a standard twist bit; the forstner always takes more torque. And forstner's need sharpening far more frequently than twist bits. Drilling end grain is hard work, and end grain in some timbers is far tougher than end grain in other timbers.

 

[TonyL]

Thank you very much. This is probably the 8th time that i used the bit, and it was definitely used in end grain. I have to learn how to sharpen them. It's also great for me to know to use the correct pulleys. Thank you!

 

[monophoto]

I have to learn how to sharpen them.

Tony

There are many YouTube videos out there on sharpening forstner bits. Some are good, others not so much.

Most of the real work done by a forstner bit is done by the radial blade that 'planes' the bottom of the hole. Dulling of the edge at the top of that blade is the thing that causes the most concern, so sharpening that edge is the most critical thing to learn.

The best advice I have seen is to use a diamond paddle with a drop of either lapping fluid or water containing just a bit of dishwashing solution. Don't try to sharpen the edge itself. Instead, lightly rub the paddle against the flat face of the radial blade - just enough to be able to see that the metal face has been freshened. It only takes a few swipes to make a really big difference in the performance of the bit.

Eventually, it is necessary to sharpen the circular portion of a forstner bit. There are a few videos that talk about doing this with a Dremel. If the circular portion is toothed, a Dremel may not be the best tool, and you might be better of just patiently taking your time with a diamond paddle.

 

[jttheclockman]

I know we are nit picking here but this is what happens when electricians get together. First off saying a 7/8" forstner bit is a large bit is a comparison thing. A 4" forstner bit is a large bit and I will show you those. I do agree using a forstner bit is more strenuous than a standard drill bit because of the amount of material you are removing and the way you are removing it. But those lathes should be able to handle a 7/8" forstner bit with no problem. I do it all the time and larger and I said I operate all the time in the middle range of those pulleys. The chart I showed will give you speed ranges.

Yes Tony lowering the pulley and belt placement will give you greater torque but again speed is relevant to the torque also. You need to let the bit catch up to the cutting action. If you force a bit at any placement of the belt will slow the lathe down. If you use a dull bit this adds to the slowing of the cutting action thus slows the lathe down. I hope this makes sense. So you can see the same thing you see now in any speed range you choose.

I will disagree with the assumption that AC motors just die. There are various types of motors and that is an understatement, and the common ones we deal with are the universal motor and the induction motor and basically the ones that will so call break down is the universal motor used in small tools and appliances because the brushes wear and are not maintained. bearings go on them faster because they are used and abused. This is what causes motor failure. Maintain these and they will last a long time.

As I said I will stay away from all the technical talk about different motors and things like that because they are irrelevant here. But Tony yes lower the belt and slow your feed rate down and use a sharp bit and you will be fine. If the Tech told you this then he is on the right track. Is it the perfect answer only you can tell. Those controllers are also a big part of speed and torque control on those DC motors. Being a newer lathe we can assume the brushes are in good condition as well as motor bearings.

Good luck

 

[jttheclockman]

Tony at one time you said you use the Trend sharpening diamond cards. I have supplied numerous times the Trend site and on it they show how to sharpen Forstner bits along with many other things. If you need me to find that link again I surely will. Good luck.

 

[TonyL]

Thank you JT. I do have one and subscribe to their YT channel. I will look for it. Thanks!