Lathe Motor Mount Improvements

[Paul Jones]

I used a free Android app to analyze the lathe vibration magnitudes and vibration frequencies before and after installing homemade motor mount pads on my 12” swing geared-head metal lathe. The pads were made from drilling ½ inch through hole in hard rubber furniture foot pads (from Home Depot) and machining Delrin shoulder washers for partially isolating the existing M10x1.25 motor mount bolts. The vibration improvement is dramatic and better than I expected but the phone app really captured the improvement. I included a photo of a machining sample of aluminum rod before and after making various lathe vibration improvements including: motor mounts; flexible drive belt; new change gears; and lathe leveling foot pads. However, adding the motor mount pads made a very significant improvement in the machining finish.

The download Android app is "FFT Vibration Analyzer". The app allows taking x, y and z axes readings and storing the analyses as "before" snapshots for reference benchmarks and then taking more snapshots of the vibration as needed after making the improvements. The app spectral snapshots are superimposed with the benchmark to allow before and after comparisons.

I attached photos of the motor mount improvement parts and installation. There is also a photo of the phone doing the analysis whereby the red bar measurements is before installing the lathe motor mounts and the yellow bars measurements is after adding the hard rubber and Delrin motor mounts. This analysis is for the lathe spindle running at 244 RPM and the graph shows a dominant frequency at 244 RPM/60 seconds = 4.07Hz. Most of the higher frequencies were eliminated with the motor mount improvement and the dominate 4Hz vibration was reduced with the new pads.

I also confirmed it was never the 60Hz causing the any motor vibration (this motor is a 120VAC, 60Hz, 1.5 HP motor). I measured the lathe spindle at several different RPMs and all showed significant vibration improvements (this is one reassure why I previously installed the lathe tachometer so I could accurately measure the RPM, see Homemade Metal Lathe Digital Tachometer). The smart phone was placed on the flat top of the lathe cross slide (app has a 5 second delay before measuring) and the spectral analysis was measured in the vertical z-axis direction.

[Altair]

That's a lot of improvement! Thanks for sharing this great writeup, Paul.

Al

[wormil]

Been having the same issue with little ridges. I will try this.

[Paul Jones]

Hi Wormil,

The vibration problem was very frustrating at first so I rounded up the usual suspects. It is a used lathe and I thought the spindle bearings may be bad. However, I measured the TIR with both a 0.0001" dial indicator and a 0.0001" dial test indicator and the needles moved less than 0.0001" so was not the problem (luckily!). Next I added a set of leveling foot pads (Homemade Lathe Leveling Foot Pads), accurately leveled the lathe and the finished improved with the lathe firmly setting on the floor. I then replaced the drive belt (the red belt in the photo) with one that was more flexible and added two new change gears (Homemade Change Gears). Again the finished improved significantly. Finally I installed the motor mounts and now have an excellent finish. FYI - The aluminum machining sample in the photo is the "gummy" aluminum alloy from Home Depot. I have new test machining samples using 6061-T6 aluminum and 12L14 steel and these a mirror-like finish. I am happy with the surface finish improvements.

Thanks for looking a commenting. I hope this helps with your lathe.

Paul

[kbalch]

Thanks Paul! I've added your Lathe Motor Mount Improvements to our Lathes category, as well as to your builder page: Paul Jones' Homemade Tools. Your receipt:

Lathe Motor Mount Improvements by Paul Jones

tags: lathe, mount, motor

[PJs]

Wow quite a difference in finish. Thanks for the tip on the app. I have a similar problem at about 1k on my peanut and have tried some 1/2" Sorbothane I had laying around...better but not gone. Think a new belt is in order too. However my spindle RO is an order of magnitude more than yours...

Thanks for sharing Paul! ~PJ

[DIYer]

Thanks for this post, Paul Jones. That Android app is going to be useful for me too.

[Paul Jones]

PJs,

Below is a photo of the improved surface finish after doing the various lathe improvements to eliminate most of the machine vibration. This example is a surface cut across a 3" diameter section of 6061-T6 aluminum. The cross feed rate was 0.0006"/rev (at 660 RPM and a finely honed HSS tool bit) which is very fine but also provides a lot of opportunity for the vibration to show up on the finish and I don't see any in this photo. Also sprayed once with WD40 for the aluminum cutting fluid.

I hope this provides some encouragement to make the changes to your lathe.

Paul

[PJs]

Thanks Paul! Your finish is superb especially with a fixed cross feed rate on something this big! I have no auto cross feed on my peanut so something this large takes a deft hand on mine with the changing SFM, runout and buzz.

I have started quite a while ago now, hand scraping and lapping a new 14" bed/extended cross slide and my compound with some new, "Non Beer Can" Gibs, for mine. Didn't have the metrics I needed to measure properly nor a rock big enough...however my new 18 x 24 x 3 rock arrives today. Now I can move forward again. When I breakdown the old one I will also be changing the spindle bearings over to some Timken Tapers I found that are the exact match instead of the SKF that require mods to the gears/bushings. Also have some new ideas thanks to you for the motor mounting. Taking my time on a cheap-n-cheerful budget. Hopefully when I get this done it will be an order of magnitude better for what I want to do... and will probably be a $10k, $500 lathe. ~¿@ Always love old Iron and wish for space to put it! Thanks for Sharing!

~PJ

[Paul Jones]

The homemade anti-vibration mounts proved successful. However, I decided to improve upon the concept by using inexpensive vibration isolators.

I recently purchased and installed four G1101046 Cylindrical Vibration Isolators (those with a stud and threaded hole for M8 x 1.25 bolts) from Zoro for $16 including shipping. I used the four anti-vibration mounts to isolate the motor vibration and also added three rubber washers (left over from a toilet tank repair kit) to further improve the vibration isolation back to the headstock. See the attached photos.