A few weeks ago I finally acquired my first metal lathe. It’s an import (Model: CQ6123B-750) from all the small Chinese bench lathes, this is probably one of the best, aside from the newer series with the spindle gearbox.
Before buying this lathe though I had looked into the available mini-lathes, they seemed nice but they didn’t meet all of my requirements, for instance a Unimat looks like a toy compared to this lathe. Don’t get me wrong, a well tuned mini-lathe can be a very useful piece of equipment, I just required a bigger distance between centers and some extra throw.
That said, lots of work can be accomplished with these import lathes… As long as you take them apart, clean them up, lube, reassemble and finish them with a nice calibration. There’s even some repainting involved, But it’s well worth it!
Well, you’d think since it’s a new lathe you’d just set it up and go at it, but no. It’s nothing like it. Forget about the inspection sheet they give you, it’s a massive lie.
To begin with, familiarize yourself with the exploded views on the manual, you’ll need them because you’ll have to take the entire thing apart and reassemble it; that’s right.
The only portion I left in place was the headstock, my reasoning was that it should be aligned from factory and I didn’t want to go through the trouble of re-aligning it (plus I don’t currently own some of the tools required to do it properly).
Another good reason to take it apart is to make it easier to move and also to put less stress on the bed while doing so. But primarily because as-is it’s not really usable, or better put… You won’t get the most out of it and you may get into premature wear on several parts due to reasons I shall now explain.
You see, some parts are not even lubricated. Most of the lathe is covered in what’s called “shipping oil” which is most likely used, filtered motor oil. Similarly to cheap chainsaw bar oil (but in that case they may add thickeners, not always but quite often they do)
Here’s the problem with the shipping oil, as it dries up it ceases to provide lubrication, instead it provides protection. Well, that’s the intended goal, but it’s a problem for us because if we don’t fully remove it and oil everything up, we risk extreme wear of parts in a very short period of time.
One of the biggest shockers for me was finding no grease on the belt tensioner ball bearings, none whatsoever! — There have been instances of people complaining about “whining noises coming from the drive box” and it turns out it was the tensioner seizing up.
Another massive lack of lubrication was spotted on the apron, most of the gears were bone dry.
The lubrication ports provided are too small for most grease guns, they’re actually meant for thin machine oil but on an open gear system (that is, with no sump) you want grease on those gears, not thin oil. Unless they’re exposed to swarf, in which case you may want to stick with the lighter oil.
As per the actual lube ports, they’re of very low quality in fact the one by the side of the saddle (meant to lubricate the bed ways) had come apart causing the ball bearing and the spring to come loose inside the saddle. Not good at all.
Now, let me pause to make it clear this is not a series of complaints and assorted whining, it’s a narration of what I’ve encountered and what I’ve done to solve it. We all know what we’re getting into when we buy Chinese equipment like this, some of us have no other option so it is what it is.
I also haven’t gone through honing or “mating” the saddle to the ways yet, this is mostly a guideline on what I’ve done to get the lathe on a running state, we’ll deal about precision and feel later.
To begin I ran a quick inspection to determine whether everything was functional and nothing of importance was missing from the main assembly of the lathe. While the handles had massive play and everything had backlash, the gears where noisy and the overall feel was crap, it was all there (except for a live center and two combined wrenches which I suspect were stolen by whoever inspected the box prior to shipping it to my place, at the store) — Oh well…
Removing the apron
There are two variations to this method, I will explain how I actually did it and then I will present an alternative solution (now that I know how everything is assembled).
To remove the apron first you have to take the saddle off, and beforehand you have to remove the crosslide, and before that you have to remove the compound with the toolpost. Indeed, quite some work goes into getting to the actual apron, but don’t worry it’s doable and you don’t have to risk damaging anything if you follow the instructions carefully and you do it with patience.
The apron is held to the saddle by three allen screws, one of which is not visible due to the carriage being on top of it.
It’s a good idea to move the entire carriage to the far left of the bed for reasons that will soon become apparent.
To begin, remove the compound by undoing the two small nuts to the sides then pushing it up and sliding it off (or just remove the nuts and pull it up, then remove the two square bolts and replace them on the compound so you don’t lose them).
Now it’s a good idea to move the crosslide away from you, once you hit the limit back it off a couple turns. Remove the two allen screws holding the handle mount, keep it steady with one hand while turning the handle with the other, you’ll notice the shaft slowly begins to draw toward you. Be very careful not to bend or damage the leadscrew. Once it’s off, use some cotton cloth or bubble wrap on a clean bench to place it away from harms way.
The crosslide is now free to slide off, push it out carefully until it’s all the way out, the gib and the leadscrew protector will fall, so be very careful to put them back together and keep them together. The gibs you’ll most likely have to re-adjust anyway, but don’t worry we’ll get to it later. So far there’s nothing to worry about!
Now we can actually see the elusive third allen screw keeping the apron and saddle in place. To remove the saddle you’ll have to remove the two slide blocks, one is at the far end and the other one at the front. The big one at the back is held by three allen screws, the one at the front is held by two. Don’t be fooled by the third allen in there, it’s for the carriage lock, the tiny plate underneath locks the carriage when you fasten this allen screw. Surely we will soon replace it with an actual handle and a better block, but that can wait so let’s not get into a tangent!.
Before you go ahead and remove the three allens keeping the saddle and apron together, place some wood planks underneath the apron so that it doesn’t move once we do remove the bolts, reason being we don’t want to stress the leadscrew. If we bend or damage it in any way, we’re in deep trouble.
As the apron is now supported, feel free to remove the 3 allen heads and lift the saddle up, if it won’t budge double check that you’ve removed both slide blocks and the rest of the screws.
Once the saddle is off, make sure you don’t place it on the ways of the bed, instead have some more bubble wrap ready and place it somewhere else to clear the way.
The apron is now free, alright I lied. It’s free from the saddle, but not from the leadscrew. To proceed we have to roll it all the way off the leadscrew, however this is only possible if you move the saddle toward the left, not toward the right as you’d initially assume, because the leadscrew has a keyway that only goes to a certain point, this limits the movement of the apron for safety reasons.
First, the second roll/shear pin has to be punched out of the leadscrew shaft near the gearbox (toward the left), don’t worry these pins were a pleasure to remove on my lathe (I’ve had my “instances” with roll pins) since I didn’t have the right size punch tool (and you don’t want to use a center punch here, because it would expand the pin and we just want to push it out) I ended up using the shaft of a broken Dremel sharpening disk since it sits right over the roll pin. I braced the leadscrew mount with a 2×4 and some other scrap wood, so I wouldn’t impart force onto it’s rolling surface. A small (100 gram) hammer was used to punch the pins out, make sure as you are about to finally punch them out, that you turn the shaft to a side for clearance, otherwise the pin nearest to the gearbox will hit the cast iron shoulder and you won’t be able to remove it until you push it back and turn the shaft.
It’s not required to remove both pins to extract the leadscrew, only the far right one has to be removed. I removed both because I didn’t know this until I finally removed the leadscrew and noticed it’s only held by one of the pins.
Remember, this is not a race — take your time, be patient and very careful. We don’t want to harm the leadscrew or the halfnut in any way! — If you get frustrated, take some time off to do something else and come back with a cool positive mind. You can do it!
Now we have to remove the leadscrew mount at the far end of the bed. It’s held by two allen screws. However, first you should undo the grub screw on the leadscrew nut (look at the end of the leadscrew by the side of the mount and you’ll see it, regular allen grub screw right there on the nut!)
Now we need to remove the lock nut (that’s what I call it, the end nut that keeps a bit of tension on the leadscrew) to do this I had to use a vise grip, lots of cotton cloth and a 10mm wrench on the nut. Oh by the way, to do this you must be slightly insane or have a big pair of bawls. Maybe I’m tired but I have not found another solution that didn’t require shoving something into the drive gear to prevent the leadscrew from moving (I don’t like the idea and by the way the cotton rag protected the leadscrew and left no marks)
The only other way would be to clamp by the shoulder where we removed the roll pins, but that would impart torque all throughout the leadscrew, which is something I didn’t like either. When it comes to torque, keep everything as short as possible!
Removal of leadscrew mount on the lathe
The trick is to wrap enough protective layers on the far end of the screw (to the left of the mount) so that we can grab it but not damage it with the vise grip, said vise grip will be set to a “light” clamp, not too tight — just enough so the leadscrew won’t move under a bit of torque.
Now we can remove the nut and undo the vise-grip.
DO NOT try to vise-grip the end of the leadscrew thinking you’ll get away with it, there’s a thread and you will damage it, in turn you will then damage the nut while trying to remove it and it will all become one big mess.
At this point we can actually knock the mount off, in my case it wasn’t budging because the paint was keeping it in place (they paint after assembly and often assemble while some parts are still wet).
The solution?, wooden mallet. You could try a brass or rubber hammer, I really really like the wooden ones. Don’t pry it with anything, just light taps to either side (horizontally, length wise and mostly toward the right — don’t knock on it from the vertical axis) until it releases gracefully.
After the mount is off, you can now slide the apron and leadscrew off. While you do this, make sure the wood planks track underneath it so that we don’t load the leadscrew down and risk bending it, likewise with the halfnut and gear assembly. We’ll be moving the apron to the left. It would be ideal to ask for help at this point, someone should keep the apron steady while we carefully slide the leadscrew off to the right.
There’s no way to remove it to the left (ie. moving the carriage to the right), since the key notch won’t allow it.
If all went well you should now have the leadscrew apart from the apron and the apron apart from the lathe bed!
Second alternative to removing the leadscrew:
In theory you should be able to pull the pin out from the coupling, remove the grub screw and the nut, remove the leadscrew mount and proceed to “unscrew” the leadscrew out to the right while leaving the apron in place. Make sure the half-nut is not engaged. This method should work, but I haven’t tried it yet. If this works, it would mean you don’t have to take as many precautions because there’s no leadscrew to be damaged anymore.
Don’t force it, if something won’t budge don’t go nuts with a hammer, don’t try to cut corners. This takes time, I had to take several pauses and study the diagrams more than once before I went to remove each specific portion. I even asked around to see if others had done the same in the past or had any suggestions on the matter. A quick google search revealed no such information.
Asking for help is not a sign of weakness. If you know yourself you’ll know your limits and you’ll accept them for what they are, knowing that someone else may have already experienced what you are about to experience allows you to take a pause and listen to what they have to say on the matter. You can take it or leave it, but if you don’t ask and you don’t have the knowledge or experience, you may end up damaging something or worse. So by pure intelligence on your side, ask around. Asking for help is actually a sign of strength and not weakness.
I’m sorry for the lack of pictures, I actually wasn’t planning on documenting this. Once I put the lathe back together I’ll take pictures and post them here (in reverse order, of course).
More on part two coming soon (removing the motor, gearbox, electrics and more)
Have fun. Cheers!