Adapting Metal Lathe Headstock to Accept Woodworking Spindle Accessories

[Tom Hartranft]

I have been turning wood for about 10 years. I am considering buying a small metalworking lathe to facilitate some new woodworking projects/jigs/tooling. Considering either a 7x16 mini-lathe with 500w brushless DC motor (https://littlemachineshop.com/produc...ory=1271799306) or an 8.5x20 metal lathe with 1000w brushless DC motor (https://littlemachineshop.com/produc...ory=1271799306). Both metal lathes are called HiTorque because of their brushless DC motors. Both come with headstock flange-type back plate of 4 inches diameter for chuck mounting. Both also come with MT3/MT2 for their headstock/tailstocks.


I already have a significant investment in accessories for my NOVA DVR/XP woodturning lathe that has MT2 in tailstock and MT2 in Headstock plus 1-1/4 x 8 TPI spindle threads in Headstock. I am looking at compatibility of some of my Headstock and tail stock woodworking accessories with the HiTorque lathe. The HiTorque specs show MT3 / MT2 for headstock / tailstock plus 4-inch chuck mount in Headstock. I already have a MT2 / J33 adapter and 1/2 inch Jacobs drill chuck (2-1/2 inch long MT2) so that should be compatible between my NOVA DVR/XP and the HiTorque lathe tailstocks.

However, the headstock accessory compatibility has me puzzled because my NOVA lathe uses 1-1/4 inch x 8 TPI spindle for mounting my woodworking drive accessories. So they won't be able to directly mount onto the metal lathe chuck back plate mount or the metal lathe MT3 taper mount.


I have a Beall Collet Chuck and set of ER-32 collets ... https://bealltool.com/products/turning/colletchuck.php The collet threads onto my NOVA 1-1/4 x 8 TPI spindle threads.

I have a number of NOVA scroll chucks with 1-1/4” x 8 TPI threaded inserts to mount directly onto my NOVA DVR/XP male 1-1/4 x 8 TPI threaded spindle. I am thinking that having an ability to mount them onto the metal lathe headstock back plate mount would be useful for some machining such as single point thread turning of wooden projects like lidded urns, homemade wooden "jam" chucks to screw onto my NOVA spindle, threaded aluminum face plates to screw onto my NOVA spindle, etc . By doing wood turning of all but threads on my NOVA then moving the NOVA chuck (with wood project still clamped in NOVA chuck) over to the HiTorque for single point thread machining, I could ensure good concentricity ... and even go back to my NOVA wood lathe with project still firmly clamped in the NOVA chuck for final tweaking. However, I have not found an adapter via Google search that would go from the metal lathe MT3 or 4-inch diameter headstock back plate mount directly to my NOVA chuck female threads ... 1-1/4 x 8 TPI. I wouldn’t do heavy metal cutting/machining with this metal lathe – NOVA chuck arrangement so I don’t feel that stresses would be excessive.

One option I'm considering is buying a 4 inch diameter chuck adapter with 1-1/2 x 8 TPI center hole threads ( https://littlemachineshop.com/produc...ry=-1110836144 ) and then turning a metal nipple with 1-1/2 x 8 TPI male threads on one end and 1-1/4 x 8 TPI male threads on the other end. Would need to drill ~0.8 inch ID thru-hole through the length of the nipple billet before cutting the screw threads to facilitate passing long turning stock into/through the headstock spindle bore ID. Screw the 1-1/2 x 8 TPI end into the chuck adapter and screw my woodturning accessories onto the 1-1/4 x 8 TPI other end. Would need a shoulder in middle of the nipple in order to properly register mounting for concentricity. Would be best to mount the chuck adapter onto metal lathe with nipple already threaded into chuck adapter then do the 1-1/4 x 8 TPI thread cutting on the installed nipple in order to get optimal concentricity.


Your thoughts / recommendations please on adapting my woodworking 1-1/4 x 8 TPI female-threaded headstock chuck and collet drivers to mount onto a metal lathe headstock back plate mount.


Regards,

Tom

[Richard Coers]

The metal lathe is the only machine that can nearly reproduce itself. Buy either of the lathes and a pile of steel, and make your own adapters.

[Brice Rogers]

You can buy an MT3 to MT2 sleeve for the headstock. But anything that you add may also add runout.

I think that most people who want to thread a chunk of wood either use a spinning 60 degree dovetail cutter (with a threading jig) or do thread chasing. There are a lot of woods that would do poorly with single point threading. Single point threading is likely to cause the threads to chip out and not look very clean. But I suppose that you could make a mount to hold a small router or dremel-like tool with a high-speed cutter and attach it to your metal lathe compound. If your three jaw metal chuck is reasonably concentric (say a couple of thou) the threads are probably going to look and work fine. But if not, then your idea of using your Nova chuck would work.

I bought a 12 x 36 metal lathe before I got involved in wood turning. I have done some single point threading, including doing male threads in the 1-1/2 x 8 variety. I have also made an adapter to go from 1-1/4 x 8 to 3/4 x 16. Doing single point metal thread turning takes a bit of concentration, some math, A Machinerys Handbook, practice, some technique or process. I don't know where you are on the learning curve, but for a "first project" on your metal lathe, it could be a challenge. Here are some options that come to mind:
1. Try to find an adapter that goes from 1-1/2 x 8 female to 1-1/4 x 8 male
2. Buy an MT 3 to 1-1/4 x 8 male thread that'll screw to your Nova chuck. I bought an inexpensive MT2 to 1-1/4 x 8 male to do chuck reversing. Worst case, if you can't find one with an MT3, then get a MT3 to MT2 sleeve. You will need/want to use a draw bar to keep the adapter seated.
3. Take a cylinder of steel (I'd suggest getting 12L14 freecutting steel because it is strong but more importantly, it cuts like butter - - you'd buy it on-line) or a cylinder of aluminum and single point thread each end. Cut the 1-1/2 x 8 FM threads first. That way, once you mount it on your metal lathe, your 1-1/4 x 8 male threads will be concentric to the axis of your lathe. The challenge is making the FM threads that actually thread onto your metal lathe spindle. If, after you cut the threads, you find that they are too tight and it won't thread, you will have taken it off of your 3 jaw chuck and lost that registration. So, maybe the first step is to turn a 1-1/2 x 8 male test piece that you can check for fit with your 3-jaw metal lathe chuck. I'd suggest making the test piece on the larger end of the tolerance and then cut the FM threads a little large so that things thread together with the first try. Turning coarse FM threads takes a little practice because you are running your cutter into the cylinder and you need to stop before you slam into the bottom of the cylinder - - otherwise stuff can break. On my lathe I have a back gear and even with that the thread cutting goes quickly and you have to be poised on the half nut to disengage. Some lathes require you to stop and reverse out. Having a substantial "landing zone" is really helpful.

[Timothy Thorpe Allen]

some options that come to mind:
1. Try to find an adapter that goes from 1-1/2 x 8 female to 1-1/4 x 8 male\.

You can find it here: https://bestwoodtools.stores.yahoo.n...tspadwith.html (it might even solve your MT2 problem, too!)

[Tom Hartranft]

Tim ... thx for the link. However, need a male-to-male threaded adapter; not a female-to-male.

Bryce ... appreciate your thoughtful reply/considerations.

Am attaching two photos of options I have found for adapting metal lathe 4 inch headstock to my woodturning 1-1/4 x 8 TPI female threaded accessories.

1) The top photo option is to use a commercial MT3 spindle adapter (shown in photo) and machine 1-1/4 x 8 TPI male threads for my woodturning accessories to mount on. The piece shown in photo has a 1.5 inch dia x 1.5 inch long end for thread cutting. Would need to include a shoulder at end of threads for woodturning accessories to register against for optimal concentricity. Downside of this approach is no through hole in MT3 adapter for long rods to pass through headstock 0.8 inch ID bore. Also not good is depending on morse taper to drive the turning apparatus. Likely be ok though if limit to only threading of wood or light cutting passes on brass/aluminum turning/threading of items held in my ER-32 collets.

2) Bottom photo option is what I described in my original post and that Bryce also offered. This would require machining a threaded male-to-male nipple to go from the chuck adapter 1-1/2 x 8 TPI female threads to 1-1/4 x 8 TPI at the other end for my woodworking accessories to mount onto. Would need to machine a shoulder in middle to register both the chuck adapter and my woodworking accessories against for optimal concentricity. Would also need to face cut the face of the chuck adapter out to ~1.5 inch diameter for optimal seating concentricity of the 1-1/2 x 8 TPI threaded end shoulder. Would need to bore/drill a 0.8 inch dia through hole through the nipple to facilitate passing long rod through headstock bore. I prefer this option over the MT3 adapter option because a) accommodates through hole and b) more secure mount for tangential forces of turning.

Regards,

Tom

[Timothy Thorpe Allen]

Tim ... thx for the link. However, need a male-to-male threaded adapter; not a female-to-male.

Sorry, missed that part -- but BestWoodTools, or really any decent machine shop, might be able to make one for you if you can't make one yourself (to go along with what Richard said about the metal lathe being almost capable of reproducing itself, my dad refers to his metal lathe as "the tool to make the tool, to make the tool that gets the job done!"

[Peter Blair]

Ya that's what I thought only the learning curve for me to make some of the pieces I need would be longer than I have left. Buy the adaptors as suggested.

[Tom Hartranft]

It's been two months since I initially posted about wanting to adapt my new metal mini-lathe to accept my 1-1/4 x 8 tpi threaded woodworking chucks and ER32 collet set. In that time, the new lathe was delivered and I have been learning the ins and outs of metal lathe operations including changing gears for various thread pitches. So, going to document my results in the event another creeker wants to do something similar.

Here is the metal lathe headstock with flange-mounted 4" metal chuck that came with the lathe. The headstock includes a MT3 arbor for use when the chuck is removed from its flange.
IMG_4951 (800x600).jpg

As mentioned in the previous post, I couldn't find a ready-made adapter to mate with the metal lathe and my 1-1/4 x 8 tpi female threaded woodworking accessories. Closest I could come was the following MT3 adapter that needed to have threads machined on the end.

Here is the MT3 adapter after I finished machining the 1-1/4 x 8 tpi threads.
IMG_4946 (800x600).jpg
Took a day to do this as I did it with a hand crank on the lathe to control the geared carriage movement ... slow. Only able to cut about 0.001 inches thread depth per cut this way and the major to minor thread difference is ~ 0.150 inches. So that's about 75 hand-cranked passes from right to left on the lathe, withdraw the cutting tool after finishing right-to-left cut, crank cutting tool back to right end of adapter, advance cutting tool into adapter again and add 0.001 inches cutting depth to previous setting, handcrank the cutting tool across the threaded section again. Repeat and rinse 75 times. I don't ever care to do that again. All of my other mini-lathe work will be brass and aluminum ... hard steel is not pleasant to work with on a lightweight mini-lathe. I used carbide cutting tips on my cutters, but even they were challenged by the arbor adapter steel. Anyway ... got this one done ok.

Here is a photo of the mini-lathe headstock with the metal chuck removed to make the MT3 taper accessible for the adapter. All photos that follow are taken from directly above the metal mini-lathe.
IMG_4948 (800x600).jpg
And here is the newly machined adapter inserted into the MT3 headstock MT3 taper ... ready to mount any female-threaded 1-1/4 x 8 tpi accessory.
IMG_4947 (800x600).jpg

Here are a couple of photos showing use of my NOVA chucks and ER32 collet fixture on the mini-lathe.

IMG_4949 (800x600).jpgIMG_4950 (800x600).jpg

I checked runout and found it consistently ~ 0.003 inches after removing and reinserting the MT3 adapter. When installed on my NOVA DVR XP, the runout is less than 0.001 inches. I can live with 0.003 inches.

With this adapter I can move combined wood/metal turning projects back and forth between my NOVA DVR XP and the metal lathe. I can also use my NOVA chucks and the ER32 collets on the metal lathe for added flexibility without needing to buy more metal working chucks / collet systems.

Took a while to do, but pleased with the outcome. Have used the metal mini-lathe for a couple of other small turning projects and pleased with it on soft brass and aluminum, which is why I opted to get it in the first place.

Regards,

Tom