Quieting a Noisey Bench Top Lathe. How ??

Home Model Engine Machinist Forum

Help Support Home Model Engine Machinist Forum:

This site may earn a commission from merchant affiliate links, including eBay, Amazon, and others.
Hmmm, thanks Scott. Glad the Gauntlet is working out with its new air supply goodies.
I was in the middle of installing the rear bearing and pulling it up with the lock nut. I would term it a light press fit, but with no stick-slip. I will definitely get the pulley and key to a slip fit. If I get it together and it feels bad, I will just take it back apart and fix it.

The rear pressure tube on the .51 cal in the pic was my first experience with 3Al2.5V cwsr titanium tubing. The yield is 105ksi, and the uts is 125ksi, so perfect for large diameter pressure vessels. I had to single point thread both ends with a short solid carbide bar, with a 4 jaw chuck and steady rest. I was shocked. After some fiddling around and lapping the carbide with a diamond hone, the threads came out so pretty they almost brought tears to my eyes. For me, it seems like the higher quality materials always yield better surface finishes. Or maybe I just treat them better, LOL.
We will talk another time about my fav. Past time but very nice grouping. It is truly amazing how far air rifles have come from the old daisy red Ryder. I also want to mention to you about checking turning torque if you have a lab torque wrench. Or
A very good quality beam torque wrench. The bearing company’s should be able to give you this information if not I used to have a formula for figuring this out if I can find it I will pass it along. But as long as you get the end play down to .0003-.0005 you should be fine.
It's all back together. It is better, but not fixed.
Here what was done:
Thoroughly cleaned the bearings and all parts.
Stoned, sanded, fitted parts as needed.
The bearings are a light press fit onto the spindle, everything else is now a transition/slip fit.
Worked with the bearing preload, tightening and loosening , and tapping the end of the spindle to shift it on the bearings, and checking for "running noise" under power.
Settled on zero endplay on the spindle. That seemed to give the quietest running.
I gained an appreciation for the little oiler balls for the 2 spindle bearings. The bearings are not at all sealed and the oil is the only thing that flushes out the debris. They need oil every day I use the lathe.
It is now set in the higher speed range than it was, and we'll see how it does. Noise is better.
I still might get new bearings, now that I know how to work on the spindle.

Overall, a good learning experience, it is an improvement, and it didn't take that long.
You mentioned earlier that the motor was also noisy. Can you tell if the motor is a contributing factor?
Maybe it deserves a set of bearings too ?

You mentioned earlier that the motor was also noisy. Can you tell if the motor is a contributing factor?
Maybe it deserves a set of bearings too ?

Yes, the motor might benefit from some new bearings also. The only thing is that 3 of the motor bolts are accessible, and the 4th one is in a "you have got to be kidding me," location. So I never did get the motor removed or the noise isolators installed. I think I will consider this effort exploratory surgery, with the thought of going back in at a later time. to do the job correctly. It removed some of the intimidation factor of the lathe inner workings..... Just another machine. ;)
And they are so much quieter.
Here is a .51cal I built. Weighs a ton. The big guy in the video would have been in the right side of the pic down near the 100yd targets.
Target is 4 shots at 100 yds, 950fps using 2,800psiair.
I hope nobody gets upset, but we are discussing machining the parts. We'll get out of the ditch very shortly.
View attachment 148887View attachment 148886
Most of us like guns. Also, technically, guns are engines as the word engine comes from the Latin for such things as catapults, balistas and other tools of war. We all like engines.
Never underestimate the amount of noise even minor imperfections in bearings can make (ball and roller)

I have a few war stories of outrageous noises being traced to bearings - which disappeared on replacing the bearings - on cutting open the old units I have found very minor causes like brinelling and fretting corrosion as well as storage corrosion pitting.

In every case you kind of scratch your head in disbelief that such minor damage was the cause of the noise.

Regards, Ken-I
Never underestimate the amount of noise even minor imperfections in bearings can make (ball and roller)

I have a few war stories of outrageous noises being traced to bearings - which disappeared on replacing the bearings - on cutting open the old units I have found very minor causes like brinelling and fretting corrosion as well as storage corrosion pitting.

In every case you kind of scratch your head in disbelief that such minor damage was the cause of the noise.

Regards, Ken-I
Ken, I think you hit the nail on the head. The spindle bearings exhibit all the characteristics you mentioned. They feel smooth, but do not have that nice mirror finish of a new set. Also, oiling them every day would have helped.
Trouble from unsealed bearings

One thing that became obvious while working on this lathe spindle is that the tapered roller bearings are wide open to all sorts of debris. I am thinking anytime I use sand paper, or a Craytex stick, or a tool post grinder, or any kind of abrasive, that it all has a clear path to get into the bearings.

The picture of the spindle nose shows a 1.5mm wide gap that is directly open to the end of the rollers. Not just abrasives, but just the normal chips while machining. The picture also shows that when the headstock was masked for painting in the factory, that the ends of the bearings were open to over-spray. I wonder if that is how the overspray on the middle of the spindle in post #11 got there?
I haven't ordered new bearings yet, and I will look for some sealed ones in the 45x75x20mm size.

In the meantime, I will fabricate some sort of external seal or slinger to keep the garbage out of the bearings. This might be how the bearings got into such bad shape, mainly noise, not accuracy,....yet.

Maybe I can make a few suggestions.

I suspect all that noise you mention is being generated from multiple sources. Fresh spindle and motor bearings should help to reduce some of it. Even better in my opinion would be to go with a 3 ph motor and VFD combination. Yes a fair amount of cost, but the lower end single ph motors used on these lathes are built down to a price point as well. And 3 ph motors simply operate much smoother and quieter. It's mostly why there universally used on any industrial level machine tools with even fairly low HP motors. I'd also bet that lathe has slowly gotten a bit noisier over time just from added wear on items such as change gear bushings or those stub axles they run on. That causes unavoidable and variable backlash on the spur gearing. Anything you can do to reduce that wear on the gear bores or those stub axles will help a lot. Again those assemblies are built down to meet a price point, and for most of these lathes, it definitely shows with that extra gear noise. Properly re-boring spur gears to add anything like oilite bushings or better, is still touchy work to do it right. In my opinion, a decent 10ths capable DTI to align and re-bore truly concentric to the gear teeth really isn't optional. Shimming or building custom machined and sized washers to fit against the gear faces will lessen the side to side clearance float and help with some of that extra noise.

Some of these lathes come with a couple of plastic gears, many seem to think those are inferior and buy steel replacements that are being made available for some of these lathes and mills. Engineering wise, there's some good reasons for the manufacturer to chose that gear material. It's in general a cheapest part first after the shear pin situation in the event of a serious crash, and they help the machine to run quieter. Myford for example could have easily produced there tumbler reverse gears in cast iron or steel for there Super 7 lathes, instead they used phenolic to help with that noise and as a secondary fail safe. Lots of other manufacturers do the same. I believe Emco used at least one or two fiber change gears on there fairly expensive gear head Super 11's. Even my little South Bend shaper uses phenolic on its bull gear to help quieten that noise.

If you can drastically reduce that gear slop back to acceptable levels, then setting a known gear clearance for backlash between each pair of gears can also help to quiet them a lot. For any that don't know it yet, I've seen some on Youtube just squeeze the gears together by hand and then tightening them down in that position. What that does is bottom the gear teeth against each other which they were never designed to be set or operated like that, and it creates high rates of excess wear as well as that extra noise. For spur type gearing, there's actually a cheap, quick and easy method to set that gear lash to a known and repeatable point. Simply use a fairly narrow strip of sheet paper between those gear teeth as there squeezed together and fastened in place. Since paper products can be found in a whole variety of thicknesses, experimenting a bit with different amounts of gear clearance can quiet them even more. If it were me, and if you don't already do so, I think I'd try a strip of normal printer paper first (about .003") and then work in either direction to see what your own particular set of gears works the quietest with. I sometimes use the very old machinist trick of cigarette rolling papers as edge finders, my Zig Zag brand measure for all intents and purposes at .001" thick, folding it or using more than one can get you paper thicknesses in .001" increments.

Fwiw and since I mentioned those gears. I've also seen many advocating the use of grease or even motorcycle chain lube products on there lathe change gears to both reduce the oil mess being thrown off and help quieten the gears a bit. Unfortunately either of those products will help to retain any contamination and wear particles created from just using the machine. And those are then being continuously cycled back through the gearing creating even higher rates of wear. In reality there's simple and unarguable physics about what lube products you should be using and where. You also don't need a flood of oil, those spur gears when compared to something like an automotive transmission are under pretty light loads, a few drops of oil each time the lathe is used are all that's needed.

I've never been able to re-find the South Bend WW II era advisory they published. It's somewhere on the net, but during that war, quite a few with home shops were producing short runs of parts for that war effort. The story I read was that inaccurate surface finishes and dimensions were becoming a real issue due to parts being rejected. Apparently enough so the Department of Defence contacted South Bend for some kind of easy and cheap solution. South Bend put there engineers to work on it. What they finally came up with was for the owners of those home shops to cast a heavy thick steel mesh reinforced concrete bench top to bolt those bench top lathes down to. The old drawings I saw gave the important dimensions for cast in stud locations etc for different models of there lathes. Why that helps is pretty simple, it adds rigidity and a large amount of mass back into the lathe bed. Now just how true that story may or may not be I can't say. But it's a proven idea. There's other methods as well. On my first little 5" swing lathe bolted directly to the bench top, part taper was easily measured. I finally added a 1" thick 95 lb piece of steel plate under it. In my opinion that totally transformed it. Far quieter, it was then down to a few 10ths taper over almost 12" of it's longitudinal travel (once it was properly aligned and leveled) And it could produce much better surface finishes with the exact same material and cutting tools.

The lathes surrounding sheet metal can also add or help to magnify that noise. Every consumer grade drill press I've had was especially bad for that. Something as simple as adding a small O ring just slightly larger than the screw diameter and between the parts being joined together helped deaden the rattles and extra noise. As I said, your issues are most likely a combination of problems and there's very likely no one single fix that will instantly cure all of it.
Just a thought here setting your bearing’s to zero play may not be a good thing. By doing that you are not including any play for thermo expansion when the spindle warms up. Just a suggestion here. One other question is do you think maybe the bearings have to have some pre-load. Some setups need pre load which is complete opposite of allowing play for Thermo expansion. Just a couple more things to keep you awake at night lol
Hi Lloyd
Just for fun I looked on Amazon for your spindle bearings "The Results" Show many options.
Some Timken's for $24 Some SKF's for $35 and many others. I looked at the Timken and it did not specify an ABEC rating, they all have a letter suffix that I did not look up. like 32009X or J or Q

I had to buy some bearings for a BP mill. I found the type but not understandeing the nomenclature, I had to study a while to understand. I found quality bearings for outrageious prices but eventually found two quality ones from TURKEY! for just over 50USD. In doing this, I found that dismantling the BP was not too difficult at all. So I decided if I needed to do further repairs, it would not be that difficult. It was comprable to pulling an engine out of a car before all the modern miracles were computerized.
Maybe I can make a few suggestions.


Thank you for taking the time to offer that well thought out list of possibilities. Some of them I had thought about, some I had heard about, some of them were totally new to me, but all were things that I had not sincerely tried.

The split phase motor noise is a new one on me. I have a way to use a different motor via a belt, uncoupled from the existing bench. There did seem to be a lot of motor noise and that test might show just how much.
The sheet metal parts I can try by taping some deadening material on. I had used constrained layer dampening for projects at work but don't have the correct materials here at home. But yes, should be able to remove some resonance from the flexible pieces. I had worked some on the gear train noise with shaft spacers and shims, some made out of soda cans. It helped some. Using the paper as a gear backlash setting gauge is a great idea. Right now I just set it by pushing the gears together and them moving them apart until I can barely feel some backlash.
I would hope that the gear PDs are concentric to the center bore. That is usually the case with hobbing machines, but I will check a few just to see.

The concrete base intriguing. There are a number of empty cavities on the machine that would be good candidates for filling with concrete or non-shrink grout.

The entire machine is bolted to the top of a military surplus steel desk with extra drawers filled with heavy tooling, so it is quite heavy and mounted on a box frame that is shimmed level with the floor. The lathe is bolted thru about 4" of solid wood laminated top, but it only has one bolt at the headstock and one at the tail stock. It might be able to rock a little bit.... I am not sure.

You have given me plenty to experiment with. I will proceed!
Thank you,
Thanks everyone for the help. I am anxious to see how this all plays out, and I would imagine some of you are too. That's a great thing about these forums.
I will keep you up to date.
I have a G4003G that doesn't seem to be all that noisy, however, after doing some work on it, my ears tend to ring. I find that very curious.
Pete and all,
I started looking at this Moore Accuracy book from where you referenced it in the boring head thread. Pretty serious reading that requires a clear head. Mr Moore knew his stuff.
When I was much younger and cnc machines were not quite readily available, I was working in a gear house in Detroit as a brand new manufacturing engineer. But I had some really good mentors and I was all ears. A project of making some special profile pump gears came along and the plan was to rough the gears on a shaper, carburize and harden, then finish grind the tooth spaces on a surface grinder with the tooth space profile dressed onto the wheel with a Moore Template Dresser. (There is the Moore reference) But they were having a heck of a time with the profile and it just wouldn't roll correctly with the master gear furnished by the customer. As a febble last resort, they brought me into the discussion. They were using standard methods to generate the involute profile, but the gear required a modified profile. I knew just enough Fortran (showing my age) to generate some code from what my technical mentor had taught me about gear tooth geometry. They made the template using my code and the one cnc machine, punch tape driven, dressed the wheel and ground a gear. We are all really excited, but, sh#t, what a buzz kill, my gear didn't roll any better than the others. Poop. Luckily, my mentor and I had confidence in each other and I showed him step by step how I had calculated my code.
Mentor: so you calculated the tooth thickness as a chord?
Me: Yes, isn't that correct?
Mentor: Hmm, I must have missed teaching you that. Its measured as the arc length, not the chord.
Me: (all excited) OK, let me redo my calculations.

This time the finished gear rolled with the master and the center distance was rock solid.

Shortly afterwards, my mentor and I were talking with our boss after the good news, and the boss said, "So what happened?"
I said, "can you believe it, I calculated the tooth thickness as a chord instead of an arc!"
Big loud belly laughs from all 3 of us. Damn, what a bunch of geeks! But the best of times!
Yes the original gear centers should have been concentric to the teeth Lloyd, as you said, the gear hobbing should ensure that. But any wear to the bores and/or stub axles they run on can throw that off more than enough to matter. I only have hands on experience with a few off shore lathes, the gear bore and axle fit tolerances all seem a bit on the loose side to be honest. And if they are worn enough, then re-boring and adding press fit bushings and making new axles are about the only solution. Sloppy fits from that wear can also create more noise. To me, a quiet smooth operating machine is vastly more enjoyable to use over having something that sounds like the early stages of a train wreck. :)

As far as those 3 ph motors, 30 seconds after starting up my then brand new BP clone mill was more than enough to instantly convert me to just how smooth they are, and I've seen nothing since that changes my mind. One I forgot though, cheap, poorly joined and lumpy drive belts are another cause, it just depends on what you have and how well it was made. Probably the ultimate fix would be adding poly V drive pulleys and belt. Again more effort and money obviously. Since you already have that dampening experience, then you probably already know more than I do about how it's best done or what to use.

Nice recovery on that gear. A totally different type of career, but I was fortunate to have a few good mentors as well.

Yeah that Moore PDF can get pretty deep into it for sure, and afaik those are just the general basics. Then there's actually knowing the proper engineering, scraping etc to put even some of that into use. I think a great addition to the Moore book would be this PDF. http://www.etech.net.au/Testing Machine Tools.pdf Almost required reading if your ever trying to improve the accuracy of what you already have, or analyze when part accuracy's and/or surface finishes may not be what you expect. And very little of it is ever mentioned when the topic of lathe leveling or tramming a mill in comes up. The information is out there, the hard part is just finding what your looking for and where it might be.
Lloyd, I have a similar lathe and almost all the noise that I detect is from the straight cut gears.

Also if you are thinking of uprating to 3 phase or an inverter (as suggested in this thread), see my post on uprating my lathe here:-

Single Phase To Three Phase Rewind - Lathe Uprate

I took my single phase underpowered 550W single phase motor and rewound it to produce up to 1.4kW off a single to 3 phase inverter. For short duty cycle it can punch out as much as 2.4kW. This might sound outlandish - it isn't.

The overall improvement in lathe performance was phenomenal.

Part Off performance and overall chatter reduction from greater available smoother torque was a much needed and unexpected bonus.

There is a video clip and you can hear the gears plus a whole bunch of additional tips that might be useful to you.

Regards, Ken I
Last edited:

Latest posts