Homier 7x12 Mini-Lathe Review

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If you have not already done so, please read the Disclaimer (last updated 10/18/09)


Spindle

OK, you've all been wondering: does the spindle plate have 3 holes or 6 holes?  If you have been following this discussion on the 7x group, or have read my Versions page for the Homier lathe, you already know that the Homier spindle plate only has 3 holes.  Beginning in March, 2002, however, a few new owners reported receiving Homier lathes having the extra 3 holes needed to directly mount a 3" 4-jaw chuck. We have all been hoping that this is a permanent upgrade that can be expected on all future shipments.

Unfortunately,  mine only has 3 holes. Of course, it may still be true that lathes manufactured after a certain date have the extra holes and that I simply received one that was made before the cutoff date.  I will see if Homier can shed any light on this matter. The inset on the right below shows the 6-hole spindle plate found on the HF and Griz lathes.

spindle1_.jpg (68733 bytes) Spindle_.jpg (53281 bytes)

I have to say, that the quality of the surface of the spindle plate was disappointing. In contrast to the fine quality finish of the ways, the spindle face has a very rough finish. Adding a little more salt to this particular wound, there was considerable swarf and grit in the recesses of the spindle.

spindle_swarf=.jpg (37440 bytes)

OK, griping aside, what's the real impact? Drilling the extra holes for the 4-jaw chuck should be pretty straightforward using a hand-held drill. The swarf can be cleaned up with a brush, so has no detrimental effect other than to cause a little dissapointment with the quality. The rough surface of the spindle face can be cleaned up and trued up with a couple of fine facing cuts.  So, when all is said and done, these issues are really pretty minor. 

You have to expect some tradeoffs like this when you buy a low cost machine tool.  Assume that you are a person who likes to restore old cars. If you found a '57 Chevy with a little rust on it sitting in a barn somewhere, and were able to buy it for $300, you probably would not complain much about the rust. It's kinda like that.


Spindle and Chuck Runout

Spindle runout is the extent to which the spindle bore is not exactly concentric with the center of rotation. It is one of the most important factors in determining the overall accuracy of the lathe, since no cut can be made to a precision greater than the runout.

I measured the runout on the inside of the spindle bore and found it to be less than .0005; around .0002 as well as I could estimate with my dial test indicator.  This is surprisingly good for a lathe in this price range.

spindle_runout=.jpg (33340 bytes) chuck_runout=.jpg (31103 bytes)

Next I measured the runout near the chuck by clamping a 3/8" shank end mill in the chuck and measuring against the round surface of the shank. Initially I measured .009" runout, which is not very good.  A runout of around .003 or less is what we would like to see. 

I removed the chuck, carefully brushed the spindle and the back surface of the chuck to remove any swarf or grit, then remounted the chuck and tested again.  This time I measured the runout at just under .002" so the first reading may have been skewed by a piece of sand or grit between the chuck and spindle plate.


Electronic Controls

As on TOL, the controls are mounted atop a plastic housing mounted on the front of the headstock. The power supply circuit board is mounted inside the plastic housing, exposing it to the same risk of being shorted by metal chips that many of us have experienced.

Controls=.jpg (51241 bytes) red_button=.jpg (42767 bytes)

The control panel includes the following items:

Following the standard set by the Grizzly 7x12, the speed control must be reset to zero before the lathe can be started or the direction reversed. This is a desirable safety feature which prevents the spindle from starting up at high speeed if you happened to have left the speed control knob set there.  It also serves this purpose should there be a power failure or tripped circuit breaker.

The BIG RED BUTTON (BRB) acts as the main power switch as well as an emergency 'panic-button'. To cut off the power, you must depress the outer cap until the yellow cover latches shut.  To childproof the lathe you can insert a small (luggage-style) padlock in the loop of the yellow cover. Pressing back on the cover unlatches the lid and turns on the power. Underneath the cover is another BRB that does the real work. The outer one just presses on the inner one.

In an emergency, if you mash down on the red button, it will shut off the power and stop the lathe.  However, I have found on the Griz lathe and mill, which both have the BRB, that this does not always work quite as well as it should - if you release the button right away the lathe may not stop.


Power Supply

If you remove the electronics box from the headstock and turn it over you will see the power supply covered by a fiber sheet intended to keep metal chips from shorting out the circuitry. 

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Much debate and speculation has surrounded the Homier power supply. SCR's (Silicon Controlled Rectifiers) are at the center of this controversy as they are used instead of the Power MOSFETS (Metal Oxide Semiconductor Field Effect Transistors) used on TOL.  (For more information on the difference, see the Speed Controls page.)  At the heart of all of this is the premise that power supplies based on SCRs provide inadequate torque at low RPMs due to the way the power is switched on and off to the motor in rapid pulses.  I have certainly found that to be true for power supplies that use just 2 SCRs, but this one uses 5 and is obviously a very sophisticated circuit, based on the number of components.

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Well, I'm no expert on power supply design, but I can tell you this: the Homier has pretty good torque at low speed, quite comparable to, but maybe a little less than the Grizzly 7x12.

I measured the minimum speed using a stopwatch and determined it to be about 34 RPM.  At this speed the torque was very weak - I could easily stop the spindle by gripping it in my hand. Turn the speed up to about 50-60 RPM, though, and torque ramps up dramatically.  At these speeds you must really clamp down hard on the spindle to bring it to a stop (subjective Prony Brake).

On TOL, the power supply has earned a reputation for being the Achilles Heel.   Chips ride in on the leadscrew, work their way behind the protective cover sheet and ZAP!   Sometimes the boards  apparently fail due to overload.  The usual symptom is that the motor will only run at full speed, due to blown MOSFETS. Time will tell how the Homier board holds up under fire but the SCRs may well prove to be more robust than the MOSFETs.


Motor

The motor is labeled as 90 VDC, 400 Watts and probably equivalent in actual power despite variations in HP claimed in the ads.  It is somewhat different in appearance from those on TOL, but is basically the same type and size. The height and angle of the motor are set by two bolts threaded into the casting above the motor recess. A translucent toothed fiber belt delivers power from the motor to the drive shaft in the headstock.

motor1=.jpg (37064 bytes) motor2=.jpg (43626 bytes)


Conclusion

Well, that completes our tour of the Homier 7x12 mini-lathe. As is typical of all of the low cost imported machine tools, the Homier lathe has a few cosmetic flaws and manufacturing defects. Usually, these are minor enough that you can easily fix them yourself.  If you discover a more serious problem, you will have to rely on the vendor to replace the part or the entire lathe.

My own dealings with Homier have been very positive. I have received prompt, courteous responses to all of my emails. All of the reports I have seen on the 7x group have demonstrated that Homier stands behind the products they sell and will quickly replace any defective parts under warranty.

In the final analysis, my opinion is that this may well be the world's best lathe bargain. If you buy one, as long as you accept its limitations, I believe you will be well pleased and enjoy many years of service.


Mini-Lathe    Mini-Mill    Bandsaw   Grinder  Anodizing   Lapping    Links   Projects   Safety     Premium Content

Mini-lathe:  Accessories   Adjustments   Capabilities    Chucks    Dial Indicators   Features   Getting Started   Glossary     Introduction   Materials    Modifications   My Shop   Operation    Reviews    Sieg Factory    Tool Grinding    Troubleshooting   Tuning     Versions

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