Lathe Headstock Alignment: Cutting A Test Bar

August 7, 2018 by Quinn Dunki 39 Comments

Let’s say you’ve recently bought a lathe and set it up in your shop. Maybe you’ve even gone and leveled it like a boss. You’re ready to make chips, right? Well, not so fast. As real machinists will tell you, you can use all the levels and lasers and whatever that you want, but the proof is in the cut. Precision leveling gets your machine in the ballpark (machinists have very small ballparks) but the final step to getting a machine to truly perform well is to cut a test bar. This is a surefire way to eliminate any last traces of twist in the bed.

There are two types of test bars. One is for checking headstock-to-ways alignment, which is what we’re doing here. There’s another type used for checking tailstock alignment, but that’s a subject for another day.

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The Machinists’ Mantra: Level Thy Lathe

July 10, 2018 by Quinn Dunki 69 Comments

Let’s say you’ve gone and bought yourself a sweet sweet metal lathe. Maybe it’s one of the new price-conscious Asian models, or maybe it’s a lovely old cast iron beast that you found behind a foreclosed machine shop. You followed all the advice for setting it up, and now you’re ready to make chips, right? Well, not so fast. Unlike other big power tools, such as band saws or whatever people use to modify dead trees, machine tools need to be properly level. Not, “Hurr hurr my carpenter’s level says the bubble is in the middle”, but like really level.

This is especially true for lathes, but leveling is actually a proxy for something else. What you’re really doing is getting the entire machine in one plane. Leveling is a primitive way of removing twist from the structure. It may not seem like a huge piece of cast iron could possibly twist, but at very small scales it does! Everything is a spring, and imperceptible twist in the machine will show up as your lathe turning a couple thousandths of taper (cone) when it should be making perfect cylinders. All this is to say, before making chips, level your lathe. Let me show you the way. Continue reading “The Machinists’ Mantra: Level Thy Lathe” →

Preparing For A Lathe: How To Move 3000 Pounds Of Iron

June 4, 2018 by Quinn Dunki 90 Comments

You say to yourself, “Self, I want, nay, need a lathe”. Being a good little trooper, you then did all your research, having chosen Import or American, Imperial or Metric, and all your feed options and such. You then pulled the trigger and the machine is en route to your shop. Now what?

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A Buyer’s Guide To Lathe Options

April 24, 2018 by Quinn Dunki 59 Comments

Lathes are complicated machines, and buying one requires weighing a lot of options. We’ve already talked about buying new Asian, or old American machines (with apologies to the Germans, British, Swiss, and all the other fine 20th century machine tool making-countries). We also talked about bed length and swing, and you ain’t got nothin’ if you ain’t got that swing. Let’s talk about the feature set now. If you’re buying new, you’ll shop on these details. If you’re buying used, knowing the differences will help you pick a good project machine.

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Turn Your Lathe Into A Shaper

February 20, 2018 by Adam Fabio 16 Comments

Ingenuity is the name of the game with manual machine tools. You often have to get creative to use the tools you have to create the part you want. That’s exactly what happened when [John] needed to cut internal splines and keyways using his lathe.

Lathes are usually used to turn metal, but internal keyways and splines are operations often performed with a broach. An older tool called a shaper would be perfect here, but shapers are relatively rare these days — or are they? There are many examples of shaper attachments for lathes. These are human-powered devices that scrape a bit of metal off each pass. The lathe itself is used to keep the workpiece in place and move the tool in a repeatable way.

Rather than create a shaper jig from scratch, [John] decided to use his compound slide as the shaper slide itself. He removed the compound slide lead screw, which allowed the compound to slide freely. He then fabricated a double hinged bar and bolted this to the compound slide. Moving the bar causes the slide to move. Just add a cutting tool, and you’re ready to cut a keyway. Add an indexing plate, and you’re ready to cut a spline. You can see the tool in action after the break.

If you want to learn more about lathes and what goes into them, you can learn how to build one from scratch.

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Mini Lathe Makes Tiny Hydraulic Cylinders For RC Snow Plow

February 18, 2018 by Dan Maloney 20 Comments

You can get pretty much any part you need online these days, but some specialty parts are a little hard to come by. So if your needs are esoteric, like tiny hydraulic cylinders for RC snow plows, you might just have to roll your own.

To be honest, we never really knew that realistic working hydraulics on such a small scale were a thing, but [tintek33]’s video below opened our eyes to a new world of miniature mechanicals. You’d think a linear actuator would be a fine stand-in for the hydraulic ram on a tiny snow plow for an RC truck, but apparently no detail is too small to address in painstaking detail. And as with many things in life, the lathe is the way to get there. Every part is scratch-built from raw brass, aluminum and steel on a mini lathe, with the exception of a few operations that were sent over to the mill that could have been done with hand tools in a pinch. The video is longish, so if you’re not into machining you can skip to 16:40 or so and pick the action up at final assembly. The finely finished cylinder is impressively powerful when hooked up to [tintek33]’s hydraulic power pack, and looks great on the plow. He’s got some other videos on his site of the RC snow plow in action that are worth a look, too.

Ready to take the plunge with a lathe but don’t know where to start? We’ve covered the basics of adopting a new lathe before.

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Vintage Logan Lathe Gets 3D Printed Gears

January 13, 2018 by Tom Nardi 34 Comments

In December 2016, [Bruno M.] was lucky enough to score a 70+ year old Logan 825 lathe for free from Craigslist. But as you might expect for a piece of machinery older than 95% of the people reading this page, it wasn’t in the best of condition. He’s made plenty of progress so far, and recently started tackling some broken gears in the machine’s transmission. There’s only one problem: the broken gears have a retail price of about $80 USD each. Ouch.

On his blog, [Bruno] documents his attempts at replacing these expensive gears with 3D printed versions, which so far looks very promising. He notes that usually 3D printed gears wouldn’t survive in this sort of application, but the gears in question are actually in a relatively low-stress portion of the transmission. He does mention that he’s still considering repairing the broken gears by filling the gaps left by the missing teeth and filing new ones in, but the 3D printed gears should at least buy him some time.

As it turns out, there’s a plugin available for Fusion 360 that helpfully does all the work of creating gears for you. You just need to enter in basic details like the number of teeth, diametral pitch, pressure angle, thickness, etc. He loaded up the generated STL in Cura, and ran off a test gear on his delta printer.

Of course, it didn’t work. Desktop 3D printing is still a finicky endeavour, and [Bruno] found with a pair of digital calipers that the printed gear was about 10% larger than the desired dimensions. It would have been interesting to find out if the issue was something in the printer (such as over-extrusion) or in the Fusion 360 plugin. In any event, a quick tweak to the slicer scale factor was all it took to get a workable gear printed on the third try.

This isn’t the first time we’ve seen 3D printed gears stand in for more suitable replacement parts, nor the first time we’ve seen them in situations that would appear beyond their capability. As 3D printer hardware and software improves, it seems fewer and fewer of the old caveats apply.

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