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Easson 12B DRO lathe install with glass and SRA M-DRO magnetic scales

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Just completed a Easson 12B DRO install on my ERL-1340, I opted for the stock glass scales for the X and Z0 axis for cost reasons, but wanted to use the 3rd input on the Easson 12B DRO head. When I previously looked into the use of magnetic scales a few years ago with the Easson DRO's I was told that they may not be compatible (at least the those from DRO Pros). At the time I went with the EL700 on my mill with 4 axis magnetic scales. On my lathe, I did not need all the features of the EL700 and the Easson 12B is about 1/3rd the price. The stock glass scales are 1 micron slim line scale for the X axis and a 5 micron glass scale for the Z0 axis. The installs were pretty straight forward on the ERL-1340, I almost never use any of the stock brackets that come with these DRO's.

Cross slide was straight forward, I use some small spacer washers to set the standoff heights. Since the reader is directly mounted the holes needed to be spot on. I may at some point add some spacers to standoff the scale further from the cross slide to allow access to the cross slide lock, but so far I have not seen any creepage/movement of the cross slide when turning.

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The Z0 axis is also a direct mount to the lathe bed, fortunately the surfaces are milled on the lathe bed so there are no surface irregularities. One downside of the Easson scales relative to other glass scales that I have installed, is the lack of jacking screws at the ends to adjust for height and tilt. Some kits provide a separate backing plate for the scale that has these adjustment screws. This kit did not come with those. I mounted an aluminum vertical mount to the cross slide using the coolant pipe holder holes and the coolant pipe can now be mounted to the vertical bracket. The reader head mounts to a L bracket which allows adjustment in the vertical and horizontal planes. A protective cover mounts over the scales. I spend more time trying to figure out how to do things, as opposed to making the parts. In this case it simplified the bracket installs for the scales/readers.

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Next was the was the Z1 tailstock magnetic scale, I went with the SRA M-DRO EH-05 - 250mm/10" Reading Length Magnetic Linear Encoder (5 micron) which they said will work with the Easson DRO's so the ES-12B or ES-12C color displays. The magnetic reader and scale are very compact, a glass scale would be too bulky and awkward for mounting on the tailstock. I also wanted to mount the scale on the backside of the tailstock so it would not interfere with the QCTP. I have seen a few variations as to having a moving scale vs. have a moving reader head on a bracket. I choose to fix the reader head to the tailstock and have the scale move with the tailstock ram. I needed about 6" of scale travel so went with the longer scale, better longer than too short. The magnetic scale and stainless cover is easily trimmed to size with a tin snips.

The reader head mounts to a L bracket which straddles the the scale, the back of the bracket is milled with a channel and there is a separate backing plate behind the scale. This allows the scale to ride in a rectangular slot with no play. The scale as mounted was very rigid. I have checked the accuracy over the 5" of travel and it matches the mechanical dial perfectly, it repeats to around 0.0004" so worked out well. I do not know if SRA offers a 1 micron scale, I would have considered this for the cross slide if available. The only criticism I have of these magnetic scales is they are bare bones, so no end caps, covers, wipers, etc. just the magnetic tape, stainless strip cover and reader. The readers are very forgiving as to alignment, I origionally had a 1/4" gap between the reader head and the scale and it read with no errors. I subsequently adjusted the gap to have ~0.1" clearance.

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The front plate for the scale mount is machined to fit over the ram and uses two 5 mm allen screws to hold it to the ram where it fits over it. The plate is 1/2" aluminum, the ram recess is 0.400" which allows MT3 holders to be fully retained w/o interference and eject properly. The scale mounts in a milled pocket and is secured with two 4 mm allen screws.

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The DRO head unit is a straight forward install, but requires a backing plate to prevent the flex where it mounts to the electrical box. So far the ES-12B works very well, I much prefer the color display, the X axis changes from white to yellow when in the diameter mode. The readings are all very stable so no flickering between numbers, X0 reads to 0.0001" and Z axis read to 0.0002" increments. One interesting facet was that on the DRO menu all three displays are set to 5 micron, when I tried the 1 micron for the X axis it read out to 5 decimal places, 5 micron setting reads correctly and shows 4 decimal places. This is the newer Easson 12B display, the power supply is integrated into the unit and on the lathe setting the display shows Z0 and Z1 axis, apparently this was not the case with the previous version that had a separate power supply.

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Comments

Cross slide was straight forward, I use some small spacer washers to set the standoff heights. Since the reader is directly mounted the holes needed to be spot on. I may at some point add some spacers to standoff the scale further from the cross slide to allow access to the cross slide lock, but so far I have not seen any creepage/movement of the cross slide when turning.
Mark:

Very nicely done.

You say you are thinking about gaining access to the cross slide lock using a standoff, should it be needed. On your PM-1340GT, I remember you added a custom-made lock to the front of the cross-slide rather than using the stock lock. Is there a reason you are considering something different for your ERL-1340?

I am asking because I used a standoff to get to my PM-1440GT's lock, but it is inconvenient in some circumstances, so I have been thinking about installing something like you did on your 1340GT.

Thanlks, Bill
 
Thank you for the comments. After installing the tailstock magnetic scale and seeing how well it worked, one consideration may be to go with all magnetic scales with the ES-12B/C DRO head, the total price difference would have been about $200 more. But I have used glass scales before and never had a problem, they are just a bit more finicky on the install. The magnetic scales are small enough as to not obscure the cross slide lock or the magnetic scale which comes with a sticky back and could be directly mounted to the cross slide. One would need to see if they have 1 micron scales.

Bill, thank you for bringing up that point on the cross slide lock. I have given that consideration of doing a lock on the headstock side vs. standing off the scale. Haven't really decided which way to go if needed, personally I hate fiddling with a wrench or allen key for these locks and on my PM-1340GT they all had lever locks. I preferred the cross slide lock on the 1340GT on the headstock side because it was quick and very easy to set the degree of friction. It was really needed because on the 1340GT the cross slide shifted in position when turning, and also the ability to set the level of friction/lock. I used it constantly. So on the ERL I will probably put the lock on the headstock side if needed. The rigidity of the ERL-1340 has been impressive so far, I am getting much cleaner cuts/surface finish with much more aggressive DOC. It is a 2400lb lathe, so the additional weight does make a big difference, also very quiet with no vibration. I was doing some offset boring with my 4J chuck being significantly lopsided jaws the other day, ant the lathe was rock solid.

So far on the ERL-1340 I seem to be using the steady rest and follow rest a bit more, so I am still looking at different options. The ERL-1340 the pitch of the feed threads is different so I have not seen any axis movement when turning/threading, this may change as it wears in. You would think that lathe manufactures would have come up with a better solution for the lock positions given the wide use of DRO's, but the same designs have been around for a long time.
Mark
 
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