I’m interested in using a wood lathe (Laguna Revo 18-36, 220 V, 2 HP) to turn metal parts on occasion. I don’t expect to have to turn metal parts often, so I don’t want to invest in a metal turning lathe. I plan to adapt a cross slide and tool holder to secure the carbide-tipped tools. My problem is adapting the typical three-jaw metal-working chuck to fit my 1-1/4 inch, 8 tpi spindle. For the life of me, I can’t find the proper adapter. Chucks for metal holding typically come with three tapped M6 or M8 holes on the back. There are a variety of adapter plates for metal lathes, but I can’t find one to fit my wood lathe. I think I can make my own by drilling holes a lathe faceplate, which is made for screwing to the bottom of blanks for bowl turning. I’d rather not do that because I’d probably get the holes slightly off-center and end up with a bunch of runout. If you have any experience or advice, I’d appreciate it.
Robert in Albuquerque
P.S. I thought about using a metal lathe in my local maker-space, but they’re all closed due to the pandemic.
Replies
Your best bet is probably to pay a small machine shop to weld a piece of steel to the back of the chuck, turn it round and cut threads into it to fit. If you have a maker space nearby I'm sure you have a small machine shop close as well, and they are probably working still since they supply many essential businesses. Personally, I think Lathes impart such an immense amount of energy into a system that any solution using screws and such cobbled together would be way too dangerous for use, at least for myself.
For a limited amount if turning, just use your woodturning chuck to hold your metal.
It is certainly possible to turn metal and even stone however there are some limitations:
1. The speed attainable - your lathe does go slow enough, but what is the torque like at those lower speeds? metal turning is often high torque, lower speed.
2. The rigidity of a wood lathe is a problem. Metal lathes are generally considerably stiffer, with thicker stronger ways.
3. You may struggle to fit a cross slide and tool holder.
4. Wood lathe bearings may not be as good as metal lathe bearings.
5. Manual only!
That having been said, there are plenty of 'tubers turning steel and aluminum on the wood lathe, though results reported are variable, primarily due to limited quality gear.
I'd have a look at the achievable tolerances and see if it suits.
As for the lathe chuck backing plate, these are often custom made to match a lathe by an engineering company. There are quite a few videos on how to do that on youtube too. You could use a piece of MDF attached to a faceplate or as you say drill the holes, though getting it precisely centred could be a total nightmare. The way a machinist would do it, is to turn a very accurate disc, the exact size to fit into your chuck's back recess. A bit like a jam chuck. This will be concentric with your lathe centre and also mean you will get minimal runout. Any runout you do get will be due to the chuck squishing the softer materiel from which the backing plate is made, and unevenness in the backing plate - hence MDF as the best option. For short pieces where low accuracy is acceptable, it should be fine.
On a wood lathe, I doubt you would be able to turn a metal backing plate accurately enough to be better than MDF.
Many metal shops use a 4 jaw chuck and individually adjust each jaw to true the workpiece. Can't do that with a wood chuck, but you can use thin sheet copper to shim the jaws to achieve perfection. Do you have a dial guage?
I can't offer personal experience, but this chap can: he drills his holes on the back plate around the 24 minute mark in this video. It also has the detent ring I described. Funnily enough it came up in my feed a couple of weeks ago!
https://www.youtube.com/watch?v=uAQLrM1P-YQ
@Ben_M_CA, that's a great idea; I bet the smaller shops might need the business.
@John_C2, I took your advice and ordered some spigot jaws, which would hold some of the metal stock I need to turn.
@R_SS, my lathe is fairly stout; it has variable speed and can go down to 50 rpm. The manufacturer claims it has plenty of torque, even at low speeds, but they don't give a measurement of the torque. If I turn smaller parts and limit the amount of material I remove, I don't suspect torque would be a problem. That's fantastic advice you give about turning my own backing plate! I found plenty of advice on YouTube about metal working with a lathe (Blondiehacks has an excellent tutorial). Yes, I do have dial gauges, which I used to setup my lathe, drill press, bandsaw, and miter saw, but it has been gathering dust since. Now I have another use for the dial gauges!
This forum post is now archived. Commenting has been disabled