Minimum HP on mini-lathe for stainless steel cutting?

The_Apprentice

The_Apprentice

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I am very new to the hobby (though long ago I did have experience in machine-shop in high school).

I would like to purchase my first ever mini-lathe, but the horse-power is what worries me. I am wanting to work on creating some jewelry, as well as other small metal projects. This may involve working on 15mm diameter round bars, to 2-inch diameter tubes. The material will usually be either 304L stainless steel, or 316L stainless steel.

The main worry here, is if these mini-lathes have enough power for harder metals like that? I have read reviews of some of these mini's as stalling at times, to the point of being un-usable.

Being in Ontario Canada, there are mainly three choices to choose from.

Princess Auto sells a 1/3HP lathe for around a grand. I think enough is said on that...
https://www.princessauto.com/en/detail/1-3-hp-mini-metalworking-lathe/A-p8507659e

BusyBeeTools is seeing a 1/2HP lathe for just under a grand (due to Father's day weekend sale).
http://www.busybeetools.com/products/la ... cx704.html

And the other choice I have is KING CANADA. Which is in the same range:
http://www.kingcanada.com/detail/7-x-12 ... 0712ML/308

Maybe I am over-simplifying things, but the last one does not mention HP rating on the motor. So doing some simple math, their motor is 5.5 Amp, and since voltage is 110V, 1 phase, 60 Hz....

That should give us:
(110 * 5.5) / 746 = ~.81 hp.

If I am oversimplifying this, please let me know of my mistake, LOL.

So, going with King Canada, I am getting more than 3/4HP of power on my mini.

Does this make sense, and would this seem sufficient for machining 316 SS material?

Thanks in advance all.
 
Your equation neglects the efficiency rating, most likely the HP would be closer to 1/3 or 1/2 HP.
Mark S,
 
markba633csi said:
Your equation neglects the efficiency rating, most likely the HP would be closer to 1/3 or 1/2 HP.
Mark S,
Click to expand...
I had been thinking on that. But when I did some research, I read that efficiency is only thrown in when going the reverse, calculating backwards starting from HP.

In any case, I get more suspicious on things. Even using 100% efficiency, the 3 Amps and 110 Voltage from the Craftex lathe (for example), is quite a bit under the 1/2 HP that is listed... either I am still missing something, or it's a little fraudulent where companies are rounding 1/3 values up to 1/2 when ever they can for a better sale...

In any case, I will try calling King Canada tomorrow and see if anyone is bright enough to know the hard HP value of theirs.
 
Lots of marketing simply do same regarding motor size.

Basic math to what it consumes but not what it does.

Just think how cars would be rated...

Issue with stainless is work hardening so small cuts are somewhat out but small power in machine tends to direct one to that.

No clue to how these will work with your plan but you could request test drive or demo of them if you have some material to cut then see how they operate.

If your budget is a grand one can go old iron and do far better where they can locate say an old sb 9 size then if a bit more power is needed simply swap the motor.

Many options

Sent from my SAMSUNG-SGH-I337Z using Tapatalk
 
"Lots of marketing simply do same regarding motor size."

But does most marketing also claim their lathes come with a quick-change-gearbox, when this does not seem to be the case? I noticed these Chinese lathes keep indicating this, when I see so no such thing. Even after reading through the on-line manuals... no such thing. Yet outside box indicates there is a QCGB.

Grrrrrrrrr.
 
Them folks can work "quickly" to change the gears....

One can quickly change the gears since they are just under a simple cover...

"Quickly Changable Gears in a Box"...

Sent from my SAMSUNG-SGH-I337Z using Tapatalk
 
Well, I sent King Canada an email today of some information on their (hidden HP)...

"We typically do not use Horsepower because it can be very misleading. We are required to use amps as a rating. I will give you an example and you can draw your own conclusions. Grizzly has a very similar model that is 3.3 amps and calls it a 3/4HP, which is high by any calculations or conversions that you find online. Ours is a 5.5 amp. and therefore would be higher."​

I do know the KC looks almost identical to the Grizzly (with minor differences), but the Amps may be one of the better selling points. Especially since I can pick it up practically for the same price.
 
Amps at what volts and what power factor?

Sent from my SAMSUNG-SGH-I337Z using Tapatalk
 
The_Apprentice said:
I had been thinking on that. But when I did some research, I read that efficiency is only thrown in when going the reverse, calculating backwards starting from HP.

In any case, I get more suspicious on things. Even using 100% efficiency, the 3 Amps and 110 Voltage from the Craftex lathe (for example), is quite a bit under the 1/2 HP that is listed... either I am still missing something, or it's a little fraudulent where companies are rounding 1/3 values up to 1/2 when ever they can for a better sale...

In any case, I will try calling King Canada tomorrow and see if anyone is bright enough to know the hard HP value of theirs.
Click to expand...

I had a Harbor Freight 7x12 which looks to be the same as the ones you are listing. They advertise as having 3/4 HP, but thats pretty much nonsense. I also have a HF mill advertised as having a 4/5 HP motor (roughly 600 watts), but it isn't even close. When tested, it was never drawing more than 350 watts. However, the motor says it is rated for 110v @ 6 amps which gets you to the 600 watts they advertise. I would say its dangerously close to false advertising, though technically they aren't wrong. The motor is rated for a max of 4/5 HP, but the mill itself is only capable of a little under .5 HP.

I am pretty sure the lathe I had was 250 watt tops. I cut plenty of 303 stainless with it with no trouble, I would just have to take light cuts. I also could never get HSS to cut well on that little lathe with stainless, so it was always carbide inserts. I cut 304 stainless a few times and it wasn't easy, mainly because of the lack of rigidity on the little lathe. I needed to cut at least .01" deep to actually take a cut, and there was so much deflection, I had to go in .0175" to get it to take that .01" cut. Not fun, but it got the job done.

I have a 10" lathe with a 1HP motor now and it cuts 304 with no trouble. If I was planning to cut that regularly, I would start bigger.
 
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