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Southbend and Hercus 9” DRO Install

neevo

Plastic
Joined
Feb 22, 2014
I’m trying to do a discrete install of an optical glass scale DRO on my Hercus 9C (which is a copy of the Southbend in almost every way). I love this lathe and it’s served me well, has a VFD and Clough42’s ELS. Is a beast of a machine for everything I need to do… but I think it’s time I take that last step and install a DRO.

It’s not essential but it really will be a nice to have feature. Especially considering I tend to machine in MM but the machine is imperial.

Surely there are a million DRO installs on a Southbend 9? Well not one that ticks all the boxes for me:

1. No extra contraptions hanging off the crosslide
2. As discrete as possible
3. Ideally hangs off the front of the crosslide so I don’t limit tailstock travel (might not be possible)
4. Trying to avoid those systems that are a bit more bespoke and use iPads as the screen
5. I would like the scales to be moveable on the crosslide not the read head

The Z axis will be easy as anything will fit on the back of the lathe. But for the crosslide it’s a different ball game as the casting is not straight on any face, plus the locking screws for the compound seriously restrict the scale I can use.

I have a Chinese SINO DRO on my mill and it’s been faultless. So I am looking at using their optical glass scales for this too.

1. Crosslide: KA200 which is a 16x16mm glass scale. Pretty equivalent to magnetic scales
2. Z: KA300 standard scales

Here’s the lathe:

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Here you can see the contours of the crosslide and the locking nuts that will have to be avoided/still accessible. If I can fit to the front I might also be able to incorporate a chip cover for the ways:

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The rear might be a better option but trying to maintain the tailstock travel:

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In preparation I have 3D printed a model of the KA200 slide. Using 150mm of travel which is more than enough for my 9” swing going from max out on the crosslide to past centre on the tool post (I don’t do any turning on the rear of the parts as my chuck is threaded on to the spindle only). It’s a working model with the read head sliding inside it.

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This really lets me visualise where I can mount it. And gauge where all the issues are going to be. The scale length and hole placements are exactly as per the KA200 so hopefully if I mount this, the real one should just bolt right up.

Test fit on the front:

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I might look to replace these with hex cap head bolts to buy some more clearance and not have to worry about the corners of the bolts.

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The casting is quite thin at the end so I’ll have to be careful how I bolt it.

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This is mounting on the reverse side. Which arguably is a little more discrete than the front. But the tailstock travel that is lost is not ideal. The challenges with the locking bolt and the thin casting are the same on both the front and the rear. So no major benefit of one over the other.

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I also remembered another reason why I was keen to put it on the chuck side. The gib adjusters are on the opposite side:

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Playing around I’ve found a pain point. There is minimal room to have the cable come out of the read head, bend down into the central channel. Looking at the read heads on my mill they need about 33mm to curl around. So I’m not sure that’s going to work. However I’m wondering if I can just print an elbow to get the cables where I want them.

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Pretty much all the reasons you’ve explained is why I put mine on a contraption and hung it out the back of the lathe. On bigger lathes you can use mag tape and hide it in the cross slide/ carriage, but these just aren’t big enough.
 
Pretty much all the reasons you’ve explained is why I put mine on a contraption and hung it out the back of the lathe. On bigger lathes you can use mag tape and hide it in the cross slide/ carriage, but these just aren’t big enough.
Yeah that’s pretty much the only solution I found when I did my searches. Or people used those cheap caliper type scales but they have the tiny screens. I really want a proper big DRO screen like I have on the mill.

Fingers crossed I can make it all fit.
 
You'll see most dro's mounted on the cross slide on the tail stock side for good reason. For small diameter work it wouldn't matter, larger work piece diameter, using the face plate and/or chuck jaws extended out from the chuck far enough are going to eat that scale and reader head the first time you forget it's there. And that's when and not if it's going to happen. Imo at that point your going have to find and pay for the new replacement and move it to that side anyway. Those glass scales are fairly large and obtrusive on the smaller machine tools. The magnetic tape type are far less so, or there's the Newall design that would work much better. Probably a lot more money of course.
 
You'll see most dro's mounted on the cross slide on the tail stock side for good reason. For small diameter work it wouldn't matter, larger work piece diameter, using the face plate and/or chuck jaws extended out from the chuck far enough are going to eat that scale and reader head the first time you forget it's there. And that's when and not if it's going to happen. Imo at that point your going have to find and pay for the new replacement and move it to that side anyway. Those glass scales are fairly large and obtrusive on the smaller machine tools. The magnetic tape type are far less so, or there's the Newall design that would work much better. Probably a lot more money of course.
That’s a good point well made. Hadn’t considered the chuck jaws smashing the scale. A bit of tailstock loss seems better than destroying a scale.

I’ll work on putting it on the other side then. The mounting challenges are the same.
 
I will be interested to see how you make out. For what it's worth, both of my SB lathes have socket set screws to lock the compound angle. They are flush with the surface. I like the idea of making a model of the parts.
 
The flat blade set screws are terrible to adjust. I’ve already bought some 3/8 UNC cap bolts to replace the square headed ones, I’ll do the same for the gib adjusters on the compound and crosslide.
 
Fwiw, and since it wasn't mentioned, adding lock nuts on either extended length set screws or those cap screws would be a good idea as well. For smaller less complex lathes, G. Thomas in his book The Model Engineers Workshop manual advocated pulling the top or cross slides feed screws while adjusting the gib screws. You then slowly adjust each screw and run the cross or top slide back and forth by hand until you get the best smooth, no side to side slop, yet not too tight adjustment over the full travel of the slide. When I can that's now how I do mine.

But until I read that book, I also hadn't understood the non tapered gib design with those side adjusted gibs all have a built in design flaw. Most or maybe all of these gib screws are pointed and have at least some shallow depressions in the face of the gib. What happens when the slide is moved is the gib tries to move as well. At that point those pointed screw tips and depressions act like a wedge and will help self tighten the gib further. His solution was to use a single pin through the side of the slide that was a light press fit into the gib and with maybe .001" reamed clearance fit through the side of the slide to allow it's removal at any time. In case it isn't obvious yet, that pin requires an angled face that matches the dovetail angle of the gib to then get the most bearing surface for the pin into that thin gib.

He also pointed out that many had a habit of keeping there gib adjustments too tight. If Youtube is any example of the average, and I've seen quite a few mention doing so in forum posts, then I think I'd agree with him. All that does is greatly accelerate feed screw, nut and slide wear. It's then also impossible to make very small movements since the load on the screw against the nut has to build up enough until it overcomes all that extra friction. At that point it will generally overshoot how much your dialing in for any small amount of slide advance since you then have that stick / slip condition. Ideally the dovetails are designed to be supported on a film of oil which is what makes them easy and smooth to operate.

Obviously there's a lot of our lathes with a fair amount of wear on them, so a slide may not be able to be adjusted to that ideal condition. That's also a sure sign some re-machining and/or scraping might be required. If my SB shaper and A###s horizontal mill were any example, I'm firmly convinced more of the smaller machine tools we might be using at a more hobby level are sent to an early grave from poor, no or incorrect lubrication and maintenance due to a lack of knowledge than are ever worn out from what they were designed to do. At one time I was just as guilty of that myself.
 
Good idea on the gib adjusters. I’ll look to buy some long set screw and put some locking nuts on them. The original flat blade ones are horrendous to use.
 
I’m printing a mount for the read head that will attach to the travelling steady holes on the tailstock side. I have the option to make from Alu or steel on the mill, so the design reflects that. But I reckon the 3D printed part would probably be fine too. I’ll see how it goes.

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The print is really to just continue with the mock ups and make sure I’m happy with the design before I start making parts and drilling holes in things.
 
Make sure you design in a hard stop so the tail stock can't hit any part of the dro scale, reader head or the mount any time it's moved up towards the carriage. It can be mounted either on the side of your carriage facing the tail stock, or to the lower front of the TS itself.
 
There is a alternative configuration, which unfortunately may require more space behind lathe than you have available... On my Hercus 9A, I milled a flat on the side of cross slide (tailstock side) behind the rearmost gib screw and mounted the scale on a length of aluminium (aluminum?) angle. Then constructed a bracket, using some AlIMG_20230212_114726.jpgIMG_20230215_155217.jpg flat bar and chopped up sections of the Al extrusions provided with the scales, to carry both read heads which was mounted using the fixing points, provided (I assume) for a taper turning attachment, on the rear of the saddle. With the 200mm (8") scale the set up requires about 18-19 inches from the spindle centerline to the wall behind.Cross slide DRO.jpg
 
If I remember rite the 2 bolts for changing the angle on the compound are either 5/16 or 3/8's , Its been a while since I had mine apart . Just get yer hands on some long socket head set screws to replace those bolts . Don't know if it means anything but my 9A came with the long set screws .
animal
 
I just did some digging & it looks like the 9" lathes came with the square head bolts for the compound . Though I've never dealt with those square head bolts , lookin at them & their location I gotta think that the SH set screws are easier to deal with .
animal
 
I’ve bought a few bolts to try a few different things. Looks like the compound lock bolts are 3/8, so I’ve cut down some cap heads to potentially replace the square heads on there now. Simply so I don’t have to worry about getting a wrench on them and can drive them from the hex inside.

Also the travelling rear holes appear to be 5/16, so I’ve ordered some button head bolts for those as I plan on attaching the read mount using those.

Annoyingly the casting is all kinds of curves, so my mount has no chance of sitting flat:

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Instead of trying to match the mount to the lathe, I am printing a new mount with 4 set screw holes in it. As I am thinking I can use those to get a solid mount to the crosslide whilst keeping the mount itself quite simple.

Have a new mount printing now.
 
I have the new mount off the printer and checked to see if the concept will work. It looks like it will, however I haven’t worked out a solution for a tailstock stop yet as the scale covers completely where the tailstock casting slides up, so not sure how to fix that one yet.

The set screws will work perfectly to get the mount sitting flat. I don’t have any grub screws yet but test fit was done with some cap heads:

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I then mounted the scale to the mount and tested to see if it looks like it will all work. It’s tight but I think it’s looking like it just might work and it’s the minimal install I was hoping for:

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I thinned down the bolts for the compound lock so that I can get a little more clearance to the scale. They are now a 12mm head and I cold blued them to get them looking even:

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Clearance is clearance and this I think is more than enough for what I need and I just need the clearance to keep the scale off the crosslide legs:

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