Poor Man’s Lathe DRO (ARO?)

My lathe doesn’t have a Digital Read Out (DRO). This isn’t an issue on a high quality machine because the hand-wheel increments are accurate. Well, on a cheap lathe, they’re merely suggestions at best. At worst, a quick way to scrap parts.

Given that, I’ve been thinking for an age on how to go about making accurate measurements on the lathe itself.

Carriage travel is fairly straight forward: A 2″ dial indicator on a magnetic base, plonk it down on the ways perpendicular to the carriage.

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The hard part is the cross-feed. Bigger lathes have plenty of places to put magnetic bases, but real estate is pretty sparse on this one. There’s plenty of space on the cross-slide itself, but that is what I need to measure, so it’s a non starter.

Finally, I found the solution. A Mighty Mag base. It’s a strong magnet, with a very narrow footprint. With that, I can steal the arm & indicator holder from a Noga-style indicator base, make an adapter(on the lathe!) to connect the 2, and that would allow me to affix the indicator to the carriage, and indicate the amount of travel in / out.

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I wipped up the adapter:

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I used the drill press to drill a 3/16″ hole about half way into the shank to give the pinch bolt something to bite into and secure it… securely… into the mag mount:

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The parts, laid out for assembly.

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And finally, on the lathe. The left side of the carriage is about the only spot I could reasonably put it where it wouldn’t interfere with the hand-wheels or power-feed controls and be bumped around. Almost as though it’s made to go there:

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Boom. Analog Read Out (ARO? Is that a thing? It is now…) complete!

Shop Project – Small Lathe Rebuild Part 2

With the rest of the supplies to clean it in hand, it’s time to get back to it.

I really want to show the Before and After in the same shot. 0000 Steel Wool and WD40 (and some elbow grease) did the business on that crud.

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The spindle face got a similar treatment, though it took much less effort. Load up a piece of steel wool with WD40, then turn the motor on and it basically cleans itself.

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With the big cleanup done, it’s on to the ol’ “install is reverse of removal.” First the carriage goes on…

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Followed by the apron and lead screw.

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Then the cross-slide, compound and spindle go back on. She cleaned up fairly well if I say so myself!

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The shear pin for the lead screw was pretty well boogered on removal. Thankfully, I had this handy-dandy lathe with which to make myself a new one:

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After getting it back together, the cross-slide feed was still really sticky. I thought maybe the feed screw was bent (because it’s super skinny). I took it all apart and everything measured fairly straight, so I dove a little deeper and found that the graduated ring was binding up against the screw’s housing at the same spot on every rotation. If I took the ring off, the handle turned perfectly smooth.

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I could make it loose enough to work but then it wouldn’t hold its position, or I could make it tight enough to hold its position and it would be impossible to turn through that rough spot. You can sort of see where it’s interfering here, on that dark ring. I broke out the emery cloth and a fresh can of elbow grease and spent a few minutes knocking it back just enough that it turns nice and freely now.

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Next, the tail-stock’s alignment was an unknown quantity, so I wanted to take the time to center it up correctly with the bore of the chuck. Usually you’d use a couple of tapered centers for that, but, well, I don’t have any of those yet. I turned a center from a piece of scrap steel rod, and then used a centering bit in the tail-stock (which also comes to a point) and used those 2 points to get it trammed in. It’s probably not *perfect*, but it’s well within good-enough range.

Before:

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After:

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Next week, the quick change tool post arrives. I’ll need to make a spacer for that, get the tools aligned, and get some feet made for this thing. After that I’ll…probably… have motivation to clean it’s spot in the shop, and then, at long last, put this thing to work.

Shop Project – Small Lathe Rebuild Part 1

I know, I know. It’s not a Miata build, but it is Miata adjacent. I’ve already got some parts I’m looking to turned on it for my car. And it’s an interesting process, so I figured some of y’all might be interested.

I’ve been shopping for a small lathe for the shop for some time now, but kinda had a deal fall in my lap for a used, neglected, Emco 8×20 lathe. A buddy had bought it at a “used tool” auction at his work many years ago, then had a kid (and inherited his grandfather’s lathe that also needs work), so this one was just collecting dust.

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Only a moderate sketch factor with the rigging, but I stopped a couple times in the first few miles to cinch the straps down as it settled in place (and secure the rear door that had swung open), and it was fine the rest of the way back home.

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And just for fun, I turned Baby’s First Chip just to say I had before the teardown started. Because boy did it need to be gone through.

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With a little help from a couple friends, we got it down to my workshop. If you’ve ever seen where my shop is, you know how sketchy THAT was. I backed the trailer down the hill, then used the winch to slowly slide it off the trailer and into the workshop, with someone on each side to steer.

One of the first things I noticed (and was pretty worried by) was the runout on the chuck. Hopefully the entire headstock won’t need to be rebuilt, because I found the most likely culprit: a bunch of swarf built up between the back of the chuck and the lathe’s face plate. Hopefully tidying this up will improve that situation, or else I’m going to have to figure out what’s crooked in the system. The nice thing is that the lathe can be used to true itself up if need be.

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Next up was the sticky lever in the quick-change gear box for the power feed for the compound. Apparently they’ve been using grease in this thing instead of machine oil. This…will become a running theme. I let it soak in simple green then oiled it while the machine ran for a few minutes and that freed the lever up to move freely side to side. The lead screw will need to be taken off and THOROUGHLY cleaned, however, as it is caked in fine chips. This too will become a running theme.

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My next biggest problem is both the free play and stiction in the cross slide. The free play can be tuned out by adjusting the gibs and the tension on the nut that the adjustment screw rides in, but a lot of the stiction is from old, crusty grease. So, the entire compound / cross slide / top slide and apron are going to come apart to be thoroughly cleaned up. I’m not going for “car show” levels of cleanliness, but I want it to run well even if it’s not the most beautiful belle at the ball. Once again, a ton of crud under the tool post. I actually couldn’t find the witness mark for setting the tool post angle because it was caked in dirt and oil. It should turn much more freely now.

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Got the cross slide wheel & screw out. Again, CAKED on grease everywhere I turn (unintentional lathe joke!). To be clear, this isn’t grease as you think of it, just heavily applied. This is stuff that’s been on there for 20 years, dried up and left a thick coating of dry crap that has to be scraped off by a fine pick in many instances.

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And finally, the compound comes off the ways. This is the bottom of the compound, where it would slide on the lathe bed. As you can see, some surface rust (not anywhere it actually touches the lathe ways, thankfully), and a lot of old oil & dust and grit that will need to be cleaned off.

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With the compound, apron and lead screw off, she’s now pretty stark naked.

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Up next was to work on the apron (ie: the gearset that uses the lead screw to run the power feed for the compound, and rides under the compound). This is what greeted me when I took it off. Take a moment to click the picture and zoom in on just how bad it is. The amount of crud caked in the threading half-nuts, the caked on grease (more…). After I’d run it for a while, the handle for the power feed was jammed on and couldn’t be disengaged because of what ended up being a chunk of dried grease getting caught in its working. It was bad.

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A bath in the parts washer made almost no difference in the grease on the gear train there. I ended up to have to disassemble the power feed engagement lever and gear assembly and then go through the entire gear train and the lead screw, tooth by tooth, thread by thread, with a pick to actually get the hardened gunk out of the system.

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The compound angle was really tough to set earlier. This is what I found between the angle dial that’s pressed onto that arbor, and the tool post.

20171205_133947  It was a ton of work, but MAN everything turns smoothly now. It’s such a huge difference. I put the barest whiff of white lithium grease on it per the factory service recommendations, and then it’s maintained afterwards with 140W gear oil. 20171206_115325

She still needs work, but we’re getting close. I’ve got the final cleaning supplies (specifically, some 0000 steel wool to clean the ways and gibs) coming in the next day or 2, and a handful of replacement parts and upgrades that should be coming next week.