Materials Question: Using Threaded Rod as a driveshaft in a wood lathe.

Train_Fan · Sep 3, 2013

So I am making myself a wooden wood lathe as seen here: http://www.homemodelenginemachinist.com/f31/making-myself-handy-tool-lathe-21664/
And I have a question regarding my material choice for the driveshaft that will run the chuck.
Reposted from the thread:

After assembling what I have shown for a shaft, my father told me that the 1/2" All-Thread I was using was not a suitable item as a shaft, and after some thought I'd tend to agree given that it is a material designed for tension, not torsion. As you all deal with this material more than I do and have better understanding of the forces involved, what is your input? Is it fine as-is, or should I order in real shafting, along with bearings and blocks?

Thanks for any input!

tornitore45 · Sep 3, 2013

Being made for pulling rather than torsion is not really a consideration in this case. I doubt you can snap the rod turning anything smaller than 4" dia.

1/2" threaded rod can work, you can not expect much strenght but you are cutting whood.

One problem is that you will not find any chuck that threads on a standard 1/2" 13 TPI, however you can find a Jacob Type chuck (power drill) that threads on a 1/2" 2o TPI. This will give you the flexibility to mount various tools/driving dogs.

Also consider that you may need to build some driving spurs such as a Nut with 3 spikes or a coupling nut (long nut) to add a point (center) to the shaft.

You can buy a castle nut and file it so that has sharp theet to drive the work.

ShopShoe · Sep 4, 2013

Train_Fan,

Questions of strength aside, I have found that threaded rod is often variable in dimensions and centering. This may be OK in a wood lathe, but I would think you want the shaft to run as true as possible, especially if you want to run at higher speeds for sanding and polishing. The same thing would be true of the pulley you show: some of the cheap cast ones are not machined and balanced to run at higher speeds without vibration. Again, this may be Ok for what you are doing but be aware that vibration may be present.

Perhaps you can get your lathe up and running, then use it to make parts for improving itself.

Good luck and welcome to home engineering.

--ShopShoe

wackyvorlon · Sep 4, 2013

I'd be inclined to use drill rod for the spindle. Straight, dimensionally accurate. You can then thread the end.

mcostello · Sep 5, 2013

I would be afraid about getting wacked upside the head with plain allthread. At least You should find the higher strength stuff, M7 I think it's called. Or find a way to use a Grade 8 or better bolt.

MachineTom · Sep 5, 2013

There are wood lathe headstocks on ebay right now, one for 40 buck bid, the other 50 BIN or best offer, both have step pulleys. and that was just the first page. "Delta wood lathe"

Wizard69 · Sep 9, 2013

Train_Fan said:
So I am making myself a wooden wood lathe as seen here: http://www.homemodelenginemachinist.com/f31/making-myself-handy-tool-lathe-21664/
And I have a question regarding my material choice for the driveshaft that will run the chuck.
Reposted from the thread:

Thanks for any input!

Technically he is right, all thread isn't suitable for a wood lathe. It might work in a limited number of cases for rough work on small stuff.

Someone already suggested a piece of drill rod. Honestly though I'd go a bit larger in diameter so that you can screw on common spindle accessories. That would mean new bearings though.

There are a number of plans out there for shop built lathes. ShopNotes issue 73 has an article on a DIY lathe. They make use of 5/8" threaded rod and 5/8" bolt. The bolt is used to make the spindle. It is a very interesting design and I would suggest finding a copy of that issue. After all is said and done though this is still a relatively small lathe of limited capacity. The big problem here is that bolts vary in quality so you may or may not escape the runout issues.

If that doesn't work search the net for similar DIY wood lathes.

Your other option is to do a machine in metal. The Gingery process is one avenue here. The lathe would have to be adopted for the higher speeds of wood work though. The Gingery process involves a lot of wood work that you have patterns to cast parts out of aluminum. If casting aluminum is more than you want to bite off there are approached that uses steel

In any event lots of luck with your lathe.

ELM6061 · Sep 9, 2013

I would tend to agree with Brian on this one, "Not Suitable".
Honestly, what size/brand grinder are you planning to run that all thread off?? If it's a 9" Makita, god help you...

From what I have seen/shared of wood lathes, for any initial cuts to center balance the wood, is pretty slow, after that they need to spin pretty quick to get any sort of finish and if anything is out of balance, you soon get breakage of either the lathe or the piece of wood. Either way, you do not want to be around when it does happen.

One of the best cheap wood lathes I have seen, was a pedestal drill mounted on its side. Need a drill, stand it back up.

Eddie

Train_Fan · Sep 18, 2013

Alrighty. I assembled what I had and gave it a whirl to see what is of concern, and so far its holding a .015 tolerance with no noticeable vibration.

Let me make this ring at least:

I'll see if it continues to be satisfactory, then depending on price either buy shafting or go down MachineTom's or similar route.

Eddie, it is a no-name 1/2 or 3/4 HP bench grinder. I'll keep this information in mind as I go further but fine finish work is not a high priority for me, just circular items so its not too high of a speed.

Thanks all!

Materials Question: Using Threaded Rod as a driveshaft in a wood lathe.

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