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Trouble rouging out blanks, min RPM too high

Matt Meadows

Matt Meadows

Joined
May 13, 2005
Messages
171
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111
Location
Charleston SC
Howdy all,

The cabinet shop I work in has a ShopSmith, which can be turned into a pretty decent lathe (how I got started in this quaint obsession). Small turnings are a breeze, but I'm learning the hard way that larger objects are very hard to mount and round-out.

The ShopSmith's min RPM is 750, which is *insanity* 😱 with an 8-10 inch hunk of log that isn't exactly harmonic in motion. (put a bowling ball in your washing maching on spin cycle, yea, kinda like that) It already slung one off, fortunately I was expecting something like that and was out of the way.


The main thing we use on the motor-side of the lathe is a plain old 4-blade drive center. Would a faceplate center be safer, or would I risk damaging the ShopSmith motor should the wood go Scud missile on me?

Also, any tips for pre-rounding the log? We do have a bandsaw but it's too small to be of help on anything taller than say, 8 inches.
 
Well, I think it's insanity to try and turn an 8-10" diam. chunk of wood, more than 4" long on this machine. So your bandsaw should be usable for pieces that are safe to turn. This is the one with a 5/8" setcrew spindle, correct?
The shopsmith isn't really designed to turn heavy chunks of wood, it's more of a spindle-turning lathe. But if you're set on turning bowls, the 4-prong drive center is the best way to go, since you'll have the tailstock at the other end.
Getting the chunk balanced as best you can before turning on the lathe is very important. When you have the chunk of wood between centers, the heavy side will swing down and you should trim that down somehow, even with a hatchet if nothing else. Or relocate the centers until it's balanced. Then it can be rough-turned with less chance of flying off, or making the lathe dance across the room.
 
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750 RPM is not a safe speed for roughing 8"-10" blanks if they are out of round and not secure. Even if you successfully attach the blank to the lathe, sometimes 750 RPM will be too much.

You might try to trim the blank down with either a bandsaw or a chainsaw so that it is more symmetrical. Or you can make it into a smaller blank.

Another possibility is to get a smaller (or larger) pulley put on the shaft so you get a slower minimum speed. This might be your best bet.

If it feels dangerous it probably is. And it's not worth it just to make a wooden bowl. You could injure yourself severely.
 
Best advice is to make good use of the bandsaw, even to the point of tilting the table and taking a couple of slanted pieces off the endgrain. Not as if the curvature of the log in a standard half will allow you to use it anyway.

Then do something else, like use a pin chuck or pin jaws to keep a hold in the blank. If you're forced to, go to a faceplate. Holding with spur centers isn't really necessary, and with a bit of bad technique you're in the flying business. Keep the fat end toward the headstock, get support from the tail, and peel center to edge on your piece. Don't try to poke at a rotating edge.

Low on my old lathe listed as 600, by pulley and motor speed should have (might have) been 688, but it turned at 12" capacity through a couple thousand pieces, never once launching one after I replaced the Masterchuck abomination. The pin chuck configuration is all I still use from that purchase.

Also makes sense that when you reverse the piece to hollow, you should make use of the tailstock as long as possible. No problem for small gouges leaving a pillar in the center until the majority of hollowing is done. May actually save time as you can be much more aggressive in stock removal.

Remember the first rule of turning - keep yourself out of the throw zone. Especially when turning the lathe on. Worth a secondary switch near the tailstock.
 
I'm curious...I don't have anywhere near the experience of most of the people responding to this thread, but I wonder...

I have Jet mini (1014).

I don't have a band saw. All I have is a small electric chain saw.

My lathe is sitting on a bench...not bolted down.

But after roughing out blanks with the chain saw, I have more or less regularly rounded blanks that are 8-9 1/2" in diameter and 4-6 inches long.

Sometimes the lathe walks a little on me and I have to take it slow. But I've never launched a blank (knock on wood) after I started using a wood screw or faceplate.

I guess what I'm wondering is why a faceplate or wood screw isn't an acceptable solution? I don't know...like I said, I'm still learning. But I've never had any problem and aside from having to chase the lathe a little bit, I don't expect to. Am I crazy to expect my Jet to turn to iclose to its capacity?


DW
In the High Desert of Central Oregon
 
Hi DW and Redfish,

What folks are saying is basically correct. Shopsmiths are great in their ability to be many tools, but not great as any tool in particular. If you want to turn 8-10" bowls, hook up with your local turning club and spend time on a larger lathe then consider buying one.

As to the Mini, if it's not bolted down and you're not using the tailstock for roughing, you've been pretty lucky so far. All it takes is one blank with an internal void to one side and the lathe will walk right off the bench or rip off the faceplate/wood screw. I'd recommend bolting or clamping the lathe down for safety. Also, roughing is always best started between centers. It's kinda an airbag thing. Never been in an accident bad enough to need one but....... Safety is always a good consideration, even at the loss of some convenience or comfort.

Good luck to both of you,
Dietrich
 
Dietrich,

Thanks for the response (in both threads). I do use a live center when roughing out blanks. I should have mentioned that. I wouldn't think to try to rough round an unbalanced blank without the tailstock. But I tried using a heavy duty, two pronged drive center and not only did I get slipping (no matter how tight I cranked down the tailstock) but it was the one time a blank came loose on me. Since then I have been using faceplaces and wood screws (along with the tailstock) and never even had one threaten to come loose.

I wish I could bolt down my lathe, but the rubber bumper feet seem to keep it pretty stable except in extrordinary circumstances. It seems I've read, more than once, about other turners with full size lathes mounted on stands that are chasing their lathes around the shop while rough rounding. I know that this isn't good. And it's not only an annoyance but worrisome when my Jet begins to travel.

[sigh] Maybe a Stubby would solve my problems.


DW
In the High Desert of Central Oregon
 
Thanks all. Could someone educate me on what pin-chuck/pin-jaws are? Never seen them, sounds interesting. In fact, anyone know of a page describing the different types of chucks out there? I know there are more than I can count.

And yes, the Shopsmith is definitely more of a spindle-turning device for sure. I've turned out a few goblets out of some cedar, was good for that as well.
 
DW, pick up a couple of quick clamps and use those for stability. The other option is bolting it to a piece of plywood and then clamping that.

The other fun thing to know is that spur centers aren't meant to be set by cranking the tailstock. That's actually a good way to wear out your headstock bearings as they're not built so much for lateral pressure. Take a good dead blow hammer, or mallet and pound that sucker in deep then take it out, mount it on the headstock, and line up the piece onto it with a nice, solid pressure from the tailstock. The other nice feature of doing it this way is no screw holes in the piece.

Redfish, a pin chuck is a chuck consisting of a metal post with a flat spot on one side. You put a cylindrical metal pin on this that, when on the center of the flat spot, matches up with the outer diameter of the post. Insert this into a similar diameter hole in the piece and rotate. The pin will roll to one side and jam as it's surface moves past the diameter of the post (picture a post that, from end on, looks like a D with a circle perched on the flat side <oD>). To remove, simply rotate in the other direction.

Pin jaws, on the other hand (correct me if I'm wrong) are jaws that mount on a chuck and are long and narrow, making a small extended cylinder at the center of the chuck when fully closed (usually 3/4" or smaller and extending at least 1"). You insert this into a drilled hole and open the chuck, giving you an expansion hold on the piece.

How's that?

Dietrich
 
Redfish:
A pinchuck, more accurately known as a lockpin spindle, is a round shaft held on the lathe spindle, with a flat milled, filed, or ground on the business end to a depth of about 1/4 to 1/3 of the shaft's diameter. A small shaft (the lockpin) whose diameter is equal to the flat's depth is placed on the flat, you drill a hole in the bowl blank's top end to fit on this, and give it a turn against the lathe's rotation so the small pin locks the shaft in the hole. It works great in hard woods, but not so good in soft woods.
I know a company has one on the market, but can't remember offhand which. Most turners make them or have them made by a machinist--I have a metal lathe and made a set of varying sizes. If I'm correct about the Shopsmith's spindle, you could get a 5/8" setscrew collar long enough to fit on the lathe spindle and also hold a 5/8" shaft with a 1/8" flat filed on it, and a headless nail for the lockpin. Don't know if this will be enough for an 8-10" bowl blank, though!
Anyway, here's a pic of my lockpin spindles, which I use mostly to hold drilled vases that will take glass tubes:
 

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You can try the Shopsmith speed reducer to get the intial speed down to something more manageable to turn on. Once rough turned, you should be able to remount the bowl on the shopsmith with little or no imbalance. The speed reducer, however, cannot take too large a bowl. Because of the weight of the bowl blank and internal structure of the speed reducer, I am convinced I was getting a whirling action if I turned something too large (> 12"). Could never get the bowl stop whirling. Sent the speed reducer back to Shopsmith and it all checked out, but I still had this whirling action of the blank on the speed reducer. If you use their faceplate, it was recommended that #12 screws be used to attached the blank to the faceplate to prevent any movement. I moved my turning to a DVR 3000 and haven't turned on the Shopsmith since.


DGD
 
Great pic, I think I get it. I believe I'm going to be getting a 4" faceplate soon and a decent jaw chuck. Are there any brands/sizes that are decent (jaw chuck) for turning up to a 10" or so bowl that do well as used goods?
 
Albertabob, I'm not quite sure what I'm looking at on the pic with the router. Lol, I'm guessing that big blank isn't connected to a router about to spin it at 24,000 rpm like most routers we use. Make a nice mess of toothpics.
 
Ah, now I got ya! The only thing I don't have sitting around to do it with is the spare motor to turn it slowly, but I think we have a low-rpm drill that would.

What type/shape of router bit are you using?
 
shopsmith speed reducer

Redfish-shopsmith has a speed reducer for $244. I have stopped using my shopsmith as I purchased a Oneway 1640. The speed reducer worked ok, but I hate having to set up stuff. Contact me is interested in mine at a good price, : 😀 Gretch
 
Redfish said:
Howdy all,

The cabinet shop I work in has a ShopSmith, which can be turned into a pretty decent lathe (how I got started in this quaint obsession). Small turnings are a breeze, but I'm learning the hard way that larger objects are very hard to mount and round-out.

The ShopSmith's min RPM is 750, which is *insanity* 😱 with an 8-10 inch hunk of log that isn't exactly harmonic in motion. (put a bowling ball in your washing maching on spin cycle, yea, kinda like that) It already slung one off, fortunately I was expecting something like that and was out of the way.


The main thing we use on the motor-side of the lathe is a plain old 4-blade drive center. Would a faceplate center be safer, or would I risk damaging the ShopSmith motor should the wood go Scud missile on me?

Also, any tips for pre-rounding the log? We do have a bandsaw but it's too small to be of help on anything taller than say, 8 inches.
Click to expand...


Redfish,

I own a Shopsmith and bought the speed reducer for turning larger bowls. The reducer slows the SS down to 100 RPMs and I had no trouble turning it round and was able to increase the speed with out any trouble. I know you said you use the SS at your cabinet shop so maybe you wouldn't be willing to spend the $$ to purchase the speed reducer but it would be alot cheaper than buying a lathe.
 
Lol, Dietrich, that thought's crossed my mind more than a few times (today alone). Alas, if I was to shoehorn another piece of equiment into our shop, much less one that's not profitable for a cabinet shop, I think I'd get more than a few evil stares. That, and I live in an apartment so I don't have a garage.

If I can get the blanks roughed into round, and get some decent chucks, I think I can turn this shopsmith into a decent (and I said decent, not great) hobby-grade lathe. I know for sure I'll be upgrading when I have the personal space for it.

DGD, I apreciate the advice and offer, I'll run it by the boss (the owner of the shopsmith). If he's interested, I'll let you know.

Thanks,

Matt
 
Shopsmith sells a speed reducer for doing large bowls. it's more expensive than a jet mini however so I never considered one.
If I remember correctly the shopsmith drive is a 5/8" rod with a flat milled in it. You might be able to simply put a pin on the flat and use it as a pin chuck. I would worry about bending this drive rod however. That's the key to the entire shopsmith system.
 
Well, I guess if it spins metal it'll spin wood. I've never seen a metal lathe in action, save for a really oddball looking one (actually twelve of them) at a auto wheel factory I worked at for less than a week. Was a wet lathe, they had to spray the wheels with water (I guess it was water) while turning them. Was years ago and I was a naive teenager, so I didn't give it a second look. I'm thinking they were CNC b/c the booth was fully enclosed and all the operator do was load the wheel and push buttons and watch the machine make steel smoothies.
 
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