Title Change: Should You Lap Brass Gears?

[Django]

https://www.youtube.com/watch?v=ByX9pCKU7pQ

I saw this earlier today, (a different post). It concerned me enough that I started this post with what should be an obviously odd question. Basically, lapping is a final machining process that uses an abrasive paste. The abrasive particles are embedded into the softer lap, making the softer lap into an abrasive tool, (or if both parts are equally hard, the abrasive is suspended between the two, but here we are talking about gear trains, with a combination of hardness and materials). If you apply a hard abrasive to a brass gear, it also becomes a lap and will wear the harder gear. If all of the gears are the same hardness, the abrasive particles become suspended and both gears will wear intil teh compound is completely removed or breaks down to the point that is is no longer abrasive. I don’t like to offend or preach, but this video alarmed me and I feel that anyone that does this is ruining that gear train. The gear train of your phonograph is a transmission.

I just read up on Flitz and they say that it is a cleaner, not an abrasive, so I can’t say that it will harm your gears. If it is not an abrasive it will not lap anything either. It is probably dislodging contaminants. So my revised advice is, please don’t apply an abrasive to your gears. Flitz will not lap your gears and it may clean them. I am not a chemist, so I don’t know. Please, do not lap gears is still the heart of the post. On the bright side, running the Flitz on the gears for a short time may clean them , so lapping bad, cleaning good. The poster of the video may be onto a good process, but the terminology that he used concerned me.

[AZ*]

That's TMF member cheryla's video.

[JerryVan]

Would not use Flitz for this purpose. Might try Time Saver lapping compound however: https://www.newmantools.com/lapping/time.htm

Used by lots of old car guys to lap babbitt bearings. I know, that sounds crazy, but I've used it and it works. They also have a grade for brass.

[Django]

Would not use Flitz for this purpose. Might try Time Saver lapping compound however: https://www.newmantools.com/lapping/time.htm

Used by lots of old car guys to lap babbitt bearings. I know, that sounds crazy, but I've used it and it works. They also have a grade for brass.

I understand running in plain bearings. The recommendation of lapping gears is what concerned me. As I said, the person in the video was not using an abrasive polish, so he was not actually lapping anything in and the Flitz cleaner may be deep cleaning the gear, and this may be a good thing. When someone says they are going to lap a gear train that has soft gears, I feel a need to ask them to reconsider. More to the point, if you have a damaged gear tooth, you can often carefully remove the any raised material with a jeweler's file. Running an abrasive paste on a gear train will wear it and not simply remove a high spot.

I wasn't trying to offend or embarrass anyone and if I did, I am sorry for that. The Fliz method may or may not be a good thing. I don't know. I do know that if you actually try to lap the gears by adding an abrasive that you will wear them, which will increase backlash, and that is not the goal. Cleaning the gears and inspecting the condition is the best thing. If the gear has some raised material, remove it. If the gear is badly worn, replace it. If the gears are not worn, but they are slapping, adjust them.

[Wes K]

I have done the lapping method a few times, and when I do, I take the motor apart and clean the parts again after the lapping process has produced the desired result. I am not sure if the person demonstrating the use of a lap is going to do the same, but anytime I have used a lap, and the people I know who have used a lap on engines, you do not leave it in place, you wash it out or take the machine apart and wash the parts again. Just like lapping valves, the lap is washed off after the process is done.

[startgroove]

Lapping in gears is an old trick. I've used it several times, and find it a valuable procedure when installing used gears into a machine which is well broken in. The two have different wear patterns, which sometimes results in improper mesh, unwanted extra gear noise and even non-smooth running.

Lapping two gears together is a procedure which can also make tight new gears run more smoothly.

The video as shown left out some important last steps, and that is to completely clean off any abrasive material, apply the proper lubricant, and re-adjust as needed.

Just my take on Gear Lapping. Cheers, Russie

[cheryla]

I lap with Flitz because it polishes the gears out and removes micro burrs. I start with Flitz, then go to a lapping compound, then back to Flitz, TOTALLY CLEANING in between each. I keep testing with sewing machine oil to see if I have any noise. When the gears sound like I want I fully disassemble everything again, clean thoroughly, and reassemble. These gear trains were not precisionally made and have some slop.

[Django]

I lap with Flitz because it polishes the gears out and removes micro burrs. I start with Flitz, then go to a lapping compound, then back to Flitz, TOTALLY CLEANING in between each. I keep testing with sewing machine oil to see if I have any noise. When the gears sound like I want I fully disassemble everything again, clean thoroughly, and reassemble. These gear trains were not precisionally made and have some slop.

I hate to beat a dead horse, but here I go again. I don’t think that the Flitz harms anything because it is a non-abrasive cleaner, (that I do not know). Lapping compound, or any abrasive should only be used to lap in hard gears, (at least 45 Rockwell on the C scale). Please don’t take my word for it. The information is readily available. Lapping gears will increase wear and “slop”, not reduce it. Lapping compound will become embedded in the soft metal and it will continue to lap and erode the harder gear. Good lubricants will reduce or temporarily eliminate metal to metal contact and reduce the effects of the lapping compound. In the end these machines are personal property and can be serviced as the owner sees fit. I was alarmed by the thought of lapping soft gears and my comments were meant as cautionary. I do have some background, being a Mechanical Engineer and former Journeyman Tool and Die Maker. That doesn’t give me the last word, but I just wanted the readers to know that I am not pulling this out of thin air.

[startgroove]

I think your experience and advice are relevant, valuable and useful. Many of us have good experience and as they say there is more than one way to perform any task. My remarks were not intended to disqualify yours, only to add some insight. Thank you for sharing your thoughts. Cheers, Russie

[Django]

I think your experience and advice are relevant, valuable and useful. Many of us have good experience and as they say there is more than one way to perform any task. My remarks were not intended to disqualify yours, only to add some insight. Thank you for sharing your thoughts. Cheers, Russie

No offense taken. I was hoping that some of the clock people, metal workers or mechanics would comment. I try not to but in too much, but in this case, I felt the need.