# ERL1340 Thread Cutting with a Proximity Stop System



## mksj (Nov 1, 2020)

I often get questions on thread cutting using a proximity stop system, recently I had to make several threaded micrometer shafts out of O1 steel, all with the same dimensions and thread tolerances. I do not have any fancy camera holders or editing software, so just propped the camera on the head stock and hoped it didn't fall off. More just showing how I do most threading with this system, typically on a heavier lathe you can take deeper cuts on the first few passes, but I take 0.01" depth passes until I am close to target (or very deep thread), then a 0.005" or too target depth if step is less than 0.01", and then a spring pass. Use of a center is advised for longer stock stick out or thin stock. There is always some degree of flex when turning so finished dimensions do  not always correlate with dial or DRO readings. There are also some variances based on the material, speeds and feeds. I use lay down carbide inserts, usually by Carmex or Mitsubishi, I have been using the same insert for over 2 years and only rotated it because I banged/broke one of the tips. Previously with vertical threading insert holders, the inserts broke frequently. I use standard thread cutting oil applied with an oil can, and only about half makes it onto the thread.

With an electronic stop system with a VFD, it can turn the motor off at a designated position and then apply quick braking. When using a VFD for threading, I recommend turning down the Hz to the 20-30 range as this will result in quicker braking then a higher Hz range. The repeatability of an electronic sensor system varies based on many factors such as the sense range, refresh rate, and repeatability characteristics of the sensor. There are also mechanical slop in the gear train and feed system, the threading speed and pitch or feed rate. I typically thread steel in the 250-450 RPM range depending on the diameter, aluminum and softer materials up to 600 RPM with the carbide lay down inserts. The limiting factor as to RPM is more about the sense/trigger range of the sensor, the rate of travel (velocity) of the carriage and the braking rate speed. There is a point where the carriage travel will exceed the travel distance once the system is triggered. This is also a significant problem when using a mechanical switch, as they will be damaged in an over travel scenario.

In the attached video I am using 1/2" O1 steel threading at ~400 RPM, the thread length is 1.4" with a pitch of 20 TPI.  I only use the cross slide to advance the thread cutter, and leave the half-nut engaged throughout the threading process, so the threading dial is not used and it doesn't matter if it is an imperial or metric thread. I use the threading insert to cut the relief grove which is usually the target thread depth +0.005". The nice feature of the ERL-1340 and also the larger 1440TL (RML, TRL lathes) is the universal  gearboxes, so no change gears are required unless one is doing a DP/MOD type thread.


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## Aukai (Nov 1, 2020)

Thanks for posting


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## rwm (Nov 1, 2020)

I'm sure I would switch to bypass and turn in on in the forward direction!
Does your proximity sensor require you to use the cross slide? Wouldn't you get a nice finish with the compound?
Robert


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## wrmiller (Nov 1, 2020)

Show off...  

I use my proximity stop (that you made for me) for all my threading. Especially ID threading compensators! Threading into a blind hole still gives me pause, but the proximity stop does help with the nerves.


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## parshal (Nov 1, 2020)

Thanks for that Mark!  It makes me realize I'm cutting my threads just like you do and that says a lot!  I've been taking .015" cuts for three passes and then .010-.005" and then .001-.002" and trial fitting my threads after each.


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## mksj (Nov 1, 2020)

The proximity bypass system has an additional safety mechanical limit switch which disables the system if you go the wrong direction. SInce the acceleration is 5 seconds it has time to shut the system down, it is also a redundancy should the proximity sensor fail (which doesn't happen according to people that use them). Finish is a function of rigidity, and since you are taking a spring pass at speed it gives close to a mirror finish. Main reason for using the compound is for less rigid machines, but this also changes the stopping point of the cutter requiring a wider relief grove. CNC machines using various  thread cutting algorithms but the compound at 29.5 degrees is usually limited to smaller lathes. I started out with the method, but the cross slide is far easier to use for both maintaining the same end position and depth of cut.


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## rwm (Nov 1, 2020)

Thank you for explaining!
R


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## davidpbest (Nov 1, 2020)

Mark, thanks for posting this.  I also use the proximity stop for threading all the time.  I learned early on that it's REALLY important to first make a relief cut where the carriage stops with the proximity stop, and to make that relief slightly deeper than the thread small diameter.   If you forget to do that, and thread to a dead stop without a relief, the carbide insert will most likely fracture.   Been there, done that as they say.

Your new lathe looks terrific.   Are those Prada or Gucci gloves you're wearing?


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## llamatrails (Nov 1, 2020)

Thanks for posting this.

I'd like to have YouTube save the video to my Watch Later or one of my playlists for future reference, but it says:
"This action is turned off for content made for kids."

Bummer, can you disable the kid safe locks ?  Not like you made it X-rated or something ...

TIA,
Rick


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## davidpbest (Nov 1, 2020)

llamatrails said:


> Thanks for posting this.
> 
> I'd like to have YouTube save the video to my Watch Later or one of my playlists for future reference, but it says:
> "This action is turned off for content made for kids."
> ...


Are you sure the kid restriction isn’t at your end?


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## davidpbest (Nov 1, 2020)

llamatrails said:


> Thanks for posting this.
> 
> I'd like to have YouTube save the video to my Watch Later or one of my playlists for future reference, but it says:
> "This action is turned off for content made for kids."
> ...


Are you sure the kid restriction isn’t at your end?


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## llamatrails (Nov 1, 2020)

davidpbest said:


> Are you sure the kid restriction isn’t at your end?



This is the first time I've ever seen the Save button greyed out and the message.  No problem today saving other videos to my Watch Later list, I do it multiple times a day every day.

Could you try to save the video to your Watch Later playlist ?


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## Lonnie (Nov 1, 2020)

Restriction is on Marks end. I can save his other videos no problem but not this one.


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## llamatrails (Nov 1, 2020)

Lonnie said:


> Restriction is on Marks end. I can save his other videos no problem but not this one.



Thanks for checking.


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## davidpbest (Nov 2, 2020)

I dunno - my kids loved it.


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## Boxster9 (Nov 2, 2020)

Mark, thank you for the Proximity Stop.  With it, threading is a joy without the anxiety of disaster waiting to happen.


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## Lonnie (Nov 2, 2020)

Boxster9 said:


> Mark, thank you for the Proximity Stop.  With it, threading is a joy without the anxiety of disaster waiting to happen.


There are quite a few of us using his proximity stop. It's one of the best additions on my lathe. All my threading is done virtually how he shows it in the video. I get super clean threads every time and metric threading is no problem what-so-ever.


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## kb58 (Nov 2, 2020)

What type of sensor is used? I doubt that it's magnetic, capacitive maybe?


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## mksj (Nov 2, 2020)

Induction proximity sensors that sense metallic objects, the same variety as used in CNC homing and electronic limit switches, also widely used in the beverage industry. The DC type have a much higher refresh rate, but you are still limited by the current capacity, shielding type and how it is incorporated into the control system. This is an example of typical operating parameters:








						Eaton E57-18LE12-B1D $183.42 Proximity Sensor, Inductive, 18mm, PNP, NC | Zoro.com
					

Order Eaton Proximity Sensor, Inductive, 18mm, PNP, NC, E57-18LE12-B1D at Zoro.com. Great prices & free shipping on orders over $50 when you sign in or sign up for an account.




					www.zoro.com


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## kb58 (Nov 3, 2020)

Thank you, Mark. One question about the Eaton sensor: what about its $150 price makes it superior to units that cost less than 20% as much? I looked through the data sheet and don't see anything standing out. At first I assumed that it's because it's made in the US, but it's actually manufactured in Mexico. Just curious.

I'm comparing it to ones like these


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## mksj (Nov 3, 2020)

It is an example, I use different sensors depending on the build requirements. It is hard to find a shielded sensor with a 12mm sense range that have high refresh rates and can handle 500 mA of currents. Other sensor I use is shielded with a 1.2kHz refresh rate with an 8 mm sense range and 200 mA. If you have more than 2 relays and indicator lights powered off of the sensor it may  shut down the sensor. I use shielded because it is flush with the face of an aluminum holder, also unshielded is more influenced by metal around it.  Lower refresh rates will be less accurate, and you need a minimum of 8 and preferably 12mm sense range for higher threading speeds. There is also reproducibility of the sensor. The longer sense range is a bit less accurate, but still in the 0.001" reproducibility range.


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## Rich V (Nov 6, 2020)

@mksj 

Mark, I have my PM1340gt lathe set up with a VFD using the original relays etc. as per your previously posted plans. Is there anyway to incorporate a proximity stop with no or minimal changes to my current setup? I'd rather not strip out all of the controls and rebuild from scratch at this point.
Thanks
Rich


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## Buffalo21 (Nov 6, 2020)

We use proximity switches, on the boilers, but the ones your using seem to be of better repeatability than the ones we use.. if I tell it to stop at 3”, it maybe 2.85” or 3.2 “, or anywhere in between. For what we use them for, it close enough, but hardly true precision.


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## mksj (Nov 6, 2020)

The proximity sensor system does not work with the basic VFD install systems using contactors, and for safety reasons should be installed as a complete system with appropriate interlocks and safety redundancy. Accuracy of the proximity sensors can vary quite a bit based on many factors, I looked for specific characteristics in the ones I have used depending on the application. I am a bit surprised at the repeatability of the ones I have used, small variations on the stopping distance have more to do with the drive train slop than the senor accuracy. I am also considering it to disengage the feed system as opposed to an electrical stop. Ultimately an ELS type feed system would be a more ideal solution, lathe manufactures should consider this option as opposed to clunky gear boxes.


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## wrmiller (Nov 6, 2020)

mksj said:


> Ultimately an ELS type feed system would be a more ideal solution, lathe manufactures should consider this option as opposed to clunky gear boxes.



The designs of most lathes and mills dates back over 100 years ago. While I would love to have a hobby lathe designed and built with modern technology, I'm certain I couldn't afford it. My daydream of 'if I ever win the lottery' would have me looking for a true EVS head mill and a lathe with ELS and digital thread/feed. Won't ever happen though, so I guess I had better hang onto what I have.


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## ptrotter (Nov 6, 2020)

I expect that a lathe designed around an ELS and a VFD would be much less expensive to build as it would be much less complicated as it wouldn’t need any gears, only a belt drive for the spindle and a servo for the lead screw.


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## GunsOfNavarone (Nov 6, 2020)

So, do you have a build thread for the proximity sensor setup/install? With a VFD and now ELS under the hood...I feel like this is the trifecta to bring it all together. Although currently, my VFD does utilize a contactor.


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## TX COWDOC (Nov 7, 2020)

Great video, Mark. Tell us a bit about the light bar you've got on the back splash please!


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## mksj (Nov 7, 2020)

As far as proximity system builds, it usually will take me a week or longer to build a complete control system after I have components in, and lots of little details. These do not work with AC systems or contactors, and require a complete redsign of how the control system works. So no videos or build manual, just an accumulation of an evolutionary process as to the design, components, wiring and programming for each application. My newer systems are not VFD specific, but designed to be used with VFD's that have at least 7 inputs and programming features required for the system.

As far as the LED light strips for under the splash shield lip, they make a huge improvement in lighting the whole lathe bed and eliminating the shadows from overhead lights. Any 40-48" light bar will work, the ones I use are either 12 or 24VDC, and I prefer a 3000-4000K color spectrum which is not too yellow or too blue. The one I use on my ERL-1340 is a display counter type, at 42W it puts out a lot of light, but it is angled down so does not shine in your face. It is probably too long and wide for smaller lathes.








						Brand New 48" LED LIGHT BAR 3500k w/12 Inch cord And mount Brackets HIGH POWER  | eBay
					

HIGHEST QUALITY. This is for the light bar only.



					www.ebay.com
				




This is what I used on my PM-1340GT and 1440GT for other individuals.








						NEW 3'3" Long LED Light Bar Ceiling/Under Cabinet Fixture 24V 12W Soft White  | eBay
					

Find many great new & used options and get the best deals for NEW 3'3" Long LED Light Bar Ceiling/Under Cabinet Fixture 24V 12W Soft White at the best online prices at eBay! Free shipping for many products!



					www.ebay.com


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## kb58 (Nov 11, 2020)

@mksj

Mark, I went ahead and ordered the Eaton sensor you used. On the zoro site, it doesn't provide enough information (nor the part) regarding the "micro 4-pin connector." It always annoys me when vendors offer connectorized sensors without the mates. Do you by chance have a part number/source? Thanks again.

Sometime we'll have to meet up, I'm in neighboring San Marcos.


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## mksj (Nov 11, 2020)

The connections are typically M12 4 pin female for the connection cord, you can get them w/o LED's or with LED's.
https://www.amazon.com/uxcell-Female-Connector-Aviation-Electrical/dp/B01MS9PRF6
https://www.automationdirect.com/adc/shopping/catalog/cables/sensors_-z-_switches/micro_(m12)_normal_duty_q-z-d_cables/4-pole_micro_(m12)_cables/evc178


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## TX COWDOC (Dec 12, 2020)

mksj said:


> As far as the LED light strips for under the splash shield lip, they make a huge improvement in lighting the whole lathe bed and eliminating the shadows from overhead lights. Any 40-48" light bar will work, the ones I use are either 12 or 24VDC, and I prefer a 3000-4000K color spectrum which is not too yellow or too blue. The one I use on my ERL-1340 is a display counter type, at 42W it puts out a lot of light, but it is angled down so does not shine in your face. It is probably too long and wide for smaller lathes.
> 
> 
> 
> ...




Mark,
Got my LED and plan to install tomorrow.  Any advise on how to angle the lights down as you did to prevent the light from shining up into my eyes?


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## mksj (Dec 12, 2020)

Mount it under the edge of the lip, I mounted the 2 C clips with aluminum wedges so it shines about 30 degrees forward from down. So canted just enough so it lights the bed but does not shine in your eyes.


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## 9t8z28 (Dec 19, 2020)

Very cool.  How come I do not see the ERL-1340 in PM's website?


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## kb58 (Dec 19, 2020)

I spent some time today in the garage puzzling over how to implement the normally-closed proximity sensor. It's effectively a high-side switch, pulling high when off and going open when metal is detected. I want to also be able to use a foot brake and traditional "off" switch as well, so a transistor will flip its "polarity" so that all three work as expected.


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## Cadillac (Dec 19, 2020)

llamatrails said:


> Thanks for posting this.
> 
> I'd like to have YouTube save the video to my Watch Later or one of my playlists for future reference, but it says:
> "This action is turned off for content made for kids."
> ...



He was only wearing gloves didn’t you see?


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## mksj (Dec 20, 2020)

There are a number of machines and products not on the PM site, a bit unfortunate because people would probably buy more to outfit their machines. The ERL-1340 was a specific order, most people would go straight to the 1440TL which isn't much more. Both are sourced from the same manufacturer in Taiwan. If I had gone with the 1440TL I would have had to replace all my holders and chuck back plates, more than I wanted to do, and also moving the 1440TL is more challenging as it is almost 1000 lbs heavier (3400 lbs). If buying up from a smaller lathe and not having all the tooling, I would have gone with the 1440TL. Been very happy with the ERL, very quiet and solid. The VFD control system was integrated into the existing control box which was quite a challenge.

On the proximity sensors you can get them in either a NPN or PNP configuration, the sensors I use have both a NC and NO switch, have a voltage range of 10-30VDC@200 mA although some can go a bit higher to 500 mA. They are long range 3X shielded. It is not a simple matter of just adding one, as the control system needs to be designed around the sensor and the particular VFD used.  When adding a mechanical foot brake there are additional considerations that one also need to signal the VFD to go into a free run or base block mode, and also a mechanism that the lathe will not restart when the brake is released. The E-Stop also needs to cause a rapid stop and also lockout all the other controls.

I normally do not wear thin rubber gloves but I had hand surgery with stitches and they do not mix well with oil and swarf. They are at least thin enough if that they get caught on something they will tear off. Always wear eye protection and never any clothing that could get caught in the machines.

As far as the video, you should be able to download it, I disabled the kid safe and I guess little kiddies cannot see it anymore. Something new along with their ads, no free lunch on anything. So it goes.


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## Jim F (Dec 20, 2020)

I don't think this will work on my 1947 SB9C..........


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## svideo (Dec 20, 2020)

Kind of off topic, but the YouTube thing is because you told YouTube that the content is targeted at kids.  Note that this is different from “kid safe”.  Unless you are actually making content that is specifically focused on children, you don’t want to tick that box.  YouTube applies a bunch of rules to anyone making content targeting children for several good reasons, none of which are going to apply to your work.


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## kb58 (Dec 20, 2020)

After thinking it over, I have an approach to use MKSJ's recommended sensor, which pulls up but not down. The best programmable configuration for my particular VFD allows using a normally-closed momentary STOP switch. When pressed, it disconnects the VFD's STOP input, allowing it to drop to zero volts, which stops the motor. Because it's normally closed, as many STOP switches as desired can be placed in series, but incorporating a proximity sensor seemed to complicate matters. My concern was that if it failed, the lathe might never turn if the stop input is stuck at ground. The solution is to have a switch to either run the STOP switches directly to +24V, or to the output of the sensor. The switch would be labeled something like "Enable sensor." It's a nice touch that the sensor has an internal LED that lets you know when it's detected something, though it should for its $150 price!


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## 7milesup (Dec 20, 2020)

9t8z28 said:


> Very cool.  How come I do not see the ERL-1340 in PM's website?



I wondered that too.  Ironically, I called them Friday to ask about the ERL specifically.  A guy by the name of John answered the phone and I proceeded to ask him about the ERL series.  His response... He had no idea.  Never heard of them.  He then went on to suggest the ELB series.  I have purchased two machines from PM and love the service but that phone call was an utter waste of time.  
Sorry for the highjack.


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## mksj (Dec 20, 2020)

I had looked at the ERL-1340 about 10 years ago, couldn't justify the cost for a 1st lathe when I had zero experience with lathes. Went with a 1340GT for many years, it is a great lathe at the price point, and only thought of replacing it when we had to move 2 years ago. Since the ERL-1340 is a special order, you would need to speak to Matt on this one. I know of one other forum member that also ordered the ERL-1340 from QMT, and had seen some posts by others in a different forum.  Not a lot around, it would be perfect with a 2" spindle bore, but then one would just get the 1440TL with a 2.5+" spindle bore. Also a comment on the motors, these models come with different motor options, if you are planning powering it with a VFD, go with the single speed motor, they also sell factory VFD versions with a 2 speed headstock.


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## ddickey (Dec 20, 2020)

Love my ERL 13x30 but if I could do it again and if I had the space I'd go with a 40" length and get the RML 1440V. Oh and also if my company hadn't ended OT.


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## 9t8z28 (Dec 21, 2020)

So what is the ERL ?  Who makes it?  Whats the main difference between it and the PM machines?


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## Aukai (Dec 21, 2020)

Heavier machine, from what has been said. This is the "parent" company if I'm not mistaken.





						ERL Series High-Speed Precision Gear Head Lathe Machine Manufacturer - SUN MASTER
					

SUN MASTER ERL Series high speed precision gear head lathe machine with the foot brake pedal and built-in coolant pump and fitting provided. If you are interested in our high speed precision lathes, contact SUN MASTER experience lathes manufacturers!




					www.sunmaster-cnc.com


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## mksj (Dec 21, 2020)

Aukai is correct, Sunmaster makes the ERL/RML/TRL series although they recently revised their naming and models so the TRL is now the TC series. In addition, vendors can have specific models made for them. Several different US distributors carry the Sunmaster lathes in different configurations, the only one listed on the PM site that I am aware of would be the 1440/1460/1660TL series with the larger 2.55" bore of their manual lathe in this size range.  There is always the possibility of special ordering a particular machine, but you may need to wait 4-6 months for delivery.


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## Aukai (Dec 21, 2020)

I checked out both videos that showed up, very cool to watch.  
Now I wish I had more money, or more room, but at my level the GT will take me to old(er) age well I hope


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