trouble with my mini lathe

[jeff oldham]

I have a 70-100 rikon mini lathe and I turned a large bowl on it,,well it was just 7 1/2 inches but that’s about all I could turn on it,,but I tried turning another one,,,and I got a lot of vibration so I slowed the speed down,,and when I got it round I turned the speed up a little and still had the vibration plus it looked like I was actually slowing the lathe down as I was cutting on it,,and I kept sharping my tools,,actually I believe I could have stop it if I had pushed much harder,,i didn’t know maybe if the shaft was bent or maybe I need a new belt,,,could anyone help me to solve this problem,,so far it has been a good lathe and I hate to trash it,,

[Bruce Pratt]

Sounds like a loose belt, at least in part. Belt tensioning is controlled by the weight of the motor and the small locking lever on the lower front left of the lathe. Loosen the lever, push down on the motor until the belt is reasonably tight and then lock the lever. Also check to be sure that your belt is in matching top and bottom pulleys. You didn't say if you were using a faceplate or chuck, in either case, make sure it is completely threaded onto the spindle on the headstock

[Dennis Ford]

Vibration can come from several sources, tracking it down will take some effort. This lathe does not have much power so it slowing down during a cut may be or may not be significant. Some possible sources of vibration (not in any specific order):
* Work piece is out of balance
* Work not mounted securely
* Wood deflecting due to cutting forces
* Lathe not mounted with all feet touching
* Cutting forces greater than lathe built for
* Bad bearings
* Bad belt

[Stan Calow]

My Jet mini does this too. I believe it is lack of power.

[Geoff Whaling]

Jeff,

The Rikon 70-100 is the same as our Woodfast M305 and both are specified as 1/2 hp motors. It doesn't take much of a cut on a bowl to make the motor struggle, but it is one of the better mini's in my experience.

I've turned on a number of mini lathes and most will exhibit the issues you mention. The original motor & VS unit on my Nova Mercury mini lathe was one of the better units and performed far better than an after market replacement "1/2 hp" motor we retrofitted after the original died (8 years old?). All 1/2 hp motors are not equal in performance on a lathe.

The best "mini/midi lathes" I have turned on are the original Vicmarc VL100's with a full 1 hp motor and the new VL150 (62 kg) but these are not what many turners would class as a portable mini lathe. The VL150 is a brilliant lathe.

One of the biggest issues turners struggle with is understanding that wood is not homogeneous material, it has varying densities across the growth rings, voids, and can be vastly different from one side of the tree to the other (wind blown, leaning etc). Where the bowl blank was relative to the original log section dictates how the grain runs through the blank and also the changing density of the wood across the blank. Wet / green turned vs dry blanks will perform differently and affect the dynamic balance performance. Wet blanks left overnight or for extended periods can change in dynamic balance as moisture is removed from the timber. One reason for wrapping green blanks in plastic wrap while taking a break in turning. This all affects the dynamic balance of the blank while it is spinning. Rough "out of round" blanks create havoc on small lathes so it is well worth the time spent preparing bowl blanks and mounting them well.

The mass and dynamic balance of the bowl blank relative to the mass of the late & stand also affect how the whole rig will perform when an "out of balance" blank is turned. Its somewhat like getting a wheel balance done on a motor vehicle to overcome wheel vibration. Lathe vibration is like wheel vibration - the vibration can be present or worse at certain rpm, but almost unnoticeable at lower or higher rpm, which is why most turners now like variable speed lathes. Adjust the speed to remove the vibration, but that only works to a certain extent and can be quite hazardous if very high rpm's are used on "unsound" blanks.

The vibration will reduce as the rough bowl blank is trued up to "round" and will markedly reduce as the "out of balance" mass of the bowl is reduced. The relative mass of the bowl blank to lathe/stand weigh ratio improves markedly as the bowl reaches the final size.