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Standard V-Belts vs. Fenner PowerTwist Plus Adjust-A-Link Belts On A Round Column Mill Drill (AKA Rong-Fu 31) - The Verdict.
In some previous articles, we wrote about the poor surface finish created by the Dayton Grainger Mill-Drill (AKA Rong-Fu 31 Mill/Drill) using the stock V-belts. In a follow-up article, we decided to try another type of belt that claims to reduce vibration, etc.. which would hopefully lead to a better surface finish created by these benchtop mills.
We are happy to report that based on preliminart tests performed, the Fenner PowerTwist Plus Adjust-A-Link belts indeed reduce vibration leading to better surface finishes.
Unfortunately, there is still vibration to the table and the surface finish isn't quite what we expected.
After removing the stock V-belts from the head, we followed the installation instructions provided in the Fenner belt packaging to achieve the appropriate length of belt.
Creating the loop of belt was actually easier than expected. In all, the entire replacement process took less than 5 minutes.
This is where we'll skip some of the changing back and forth of belts to provide you with the verdict...
We ran test cuts using a 9/16" 4-flute carbide end mill (cheap ENCO import brand) at 1040rpm with a depth of cut (DOC) of roughly .150" at a feed rate in between 10-15IPM (inches per minute). Before we show you the resulting cut, it may interest you to hear the difference between the installed belts (click on the image to see the video - it'll loop twice between the stock and Fenner belts):
While it may seem strange to hear that the Fenner belt created more noise than the stock, it was quite the opposite. Perhaps, it's our little Canon S200 digital camera that's creating that extra noise artifact?
Here's the proof that the Fenner belt makes a marked difference. In the following pictures, we'll show you close-ups of the resulting cuts due to the same bit and cut as described above. The rougher looking finish is the result of stock belt while the smoother looking finish is the result of the Fenner-installed belt. Based on this initial result, it is clearly worth the investment of $60 or so to improve the surface finish of your work if that's important to you.
We should say that it's still not perfect! But here goes..
Wtih a chunk of 6061-T6 aluminum held in the cheap Palmgren vise, you'll note that the top slot is rougher in finish while the bottom is smoother in appearance. It's the difference between the stock belt and Fenner belt. Wow!
Here's another view:
Looks pretty good!
Here's an even more close-up view of the finishes:
There is, however, some residual vibration at the table we need to address. The other issue seems to stem from the spindle cartridge itself. We haven't taken it apart yet, but we have a "funny feeling" that its bearings are loose or need some more preload or something.. There's a very strange noise that eminates from it when the motor's shut off and the spindle winds down. Click on the image below to view the video and listen to the spindle winding down:
We will perform a bit more of a scientific test when we use a noise level meter (or decibel meter) to determine the noise differential between the use of the two belt styles.
Does removing and adjust the spindle bearing preload help? Some.
Is the motor the root of all vibration? Does filling the column with concret/cement/synthetic material make any difference?