View Full Version : Chamfering and deburring gears on new lathe

02-04-2010, 12:47 PM
After running my new lathe PM12x36 (http://www.machinetoolonline.com/PM1236.html) on all speeds for 30 min. I've took the top lid off the headstock.
Oil is pretty clear, just some tiny metal particles on the bottom, no sand.

The gears are slightly chambered but not deburred.

Before I change the oil I want to deburr the top gears(they are accessible without taking headstock apart)
I don't feel adventurous enough to take headstock apart even thought extra chamfering and deburring would help to change speed easier. Right now you have to "play" with the speed change handles before gears will engage.
I don't have experience with high quality gear lathes but I guess if gears are properly chamfered and deburred it'll be easier to change speed.

What tool should I use for deburring? I don't want to use sand paper. Some abrasive particles might stay even after changing oil and find it's way into bearings.

02-04-2010, 01:14 PM
if you mean the gears are getting 'stuck' midtravel, then what I did to fix that was open it up and just massage the gears back and forth (using my fingers right on the gears) along the keyed shaft about 20~50 times and after that the burrs wore themselfs off.

If you mean it sometimes won't engage till you rotate it, thats due to tooth alignment, get used to manualy rotating the chuck a little when gears won't engage. I would'nt try and deburr the teeth to fix that.. that would take a LOT of grinding to change the profile to engage at any alignment.

they say to never shift the speeds while its running, likey a good idea as the spindle/motor are rather high momentium.

You can likey however switch your feed speeds while its running at low RPM, since the rod connected to it will be low momentium, and while the carriage is really big, its not moving fast enough to have much momentium. Iv once tryed it at really high feed rate at medium RPM and got gear grinding however, so id only attempt it if your feedrod/leadscrew is rotating rather slow, and not on the faster spindle speeds.

My leadscrew reverse switch will also grind the gears if switched above like 100RPM spindle speed but also suffers from often having to manualy move the spindle a little to get the teeth to line up, What I usally do is turn off the lathe, and flip the lever JUST as the lathe comes to a stop, so its only doing 1~5rpm when I flip the lever, no grinding then.

Some say they can flip the spindle speed lever on there lathe while its running(at least on the lower gears)... Unless its one of those fancy electronic clutched gearboxes, I doubt it it does the gearbox any good as theres no clutch to let the gears reengage properly before applying load other then the belts that should be reasonabley tight, and no clutch (except the belts) to slip to let the motor and spindle speed resync.

02-04-2010, 01:19 PM
You ran the lathe at each of the 9 speeds for 30 minutes each ? OMG !!! It's ruined now !!! Didn't you know that you can only run it for 30 seconds at a time, then let it cool down for five minutes ? Otherwise the gears overheat and the temper is ruined ! ! !

Oh, well, it's still under warranty, right ? Maybe they'll exchange it ? Just don't tell them how you abused it.

Now you want to chamfer the gears ?


The 12x36 does have sloppy gears, and they don't shift smoothly.

But, I can't envision chamfering them in situ. :(

At the risk of sounding like a unhelpful smartass, I suggest saving your time and money for a 3ph/VFD upgrade and then you will seldom need to change gears. Best. Mod. For. The. 12x36.

Limy Sami
02-04-2010, 01:24 PM
Like everything, gears have to bed down.

DON'T remove metal from any gears while the box is still assembled - you WON'T get it all out,....... same goes for ANY abrasive process.

In your position I'd;-

Change the oil and apart from using it, leave it to run for a few hours in all speeds, FWD & REV, change oil again.

Then ''keep an eye'' on the oil and change it when you think fit.

02-04-2010, 02:03 PM
I suggest saving your time and money for a 3ph/VFD upgrade and then you will seldom need to change gears. Best. Mod. For. The. 12x36.
I know. My current single phase 220V motor is 2 hp. If I were to replace it with 3 phase motor + VFD the new motor has to be at least 3 hp or better 5 hp to get similar(to 2 hp motor + gears) torque on low RPM.
Am I right?

The Fixer
02-04-2010, 03:47 PM
Just change gears while its running, that will chamfer the gears! Just kidding....
If you're worried about the metal filings throw a magnet in there, and don't waste your time deburring/chamfering the gears. Put the lid back on and use the darn thing, it's not a space shuttle.
just my 2 bits

02-04-2010, 06:29 PM
Alex you do not need a bigger motor....
I just put one on a PM1236, a real american 2 hp 3 phase inverter duty motor.

The Gearing is still used in headstock. Just put in 70 rpm position and turn VFD down to 10 hz or so. 11.6 rpm and plenty of torque for Normal work...

The PM has the tiniest MT 3 tailstock spindle I have ever seen. It is not a heavy duty lathe, even by chinese standards...

The factory chinese 2 hp motor, comes with wiring sized for 1.5 hp worth of current draw...

The shift linkage/detents are roughly done. Gears are fine... You need to turn spindle by hand to engage gears(right lever first, then left lever...). No syncronizers or hydra shift in Headstock..

02-04-2010, 10:08 PM
Just run it and change the oil after 20-30 hours, then every whatever.

My lathe has a 300 hour break-in period before you are supposed to run it over 2000 rpm...