“Tooling up” - Lathe issues

Reading the last post over, I didn’t like that I introduced my latest acquisitions just as I had purchased them, dirty and all. Looking back at their picture now, I can hardly recognize them. So, I’ll open a little parenthesis to show them to you once again as they are now, after a complete tear down to the last bolt, and a total rebuild.

Lathe all cleaned up

She's a beauty, ain't she?

Working with this lathe has not been as straightforward as I expected. Its small size introduces idiosyncrasies that combine to make precision work as much of an art, as it is a science. And that’s not a good thing! I am still happy with it, but if I were to do it again, I think I’d lean toward a heavier duty lathe.

I still have a lot to learn, especially in choosing, and using the cutting implements correctly. At this time, I can bring a piece of steel down to maybe 3 thousands of an inch oversize consistently, but I have to finish it down to size with sand paper, to smooth the groovy finish the cutter leaves.

The more I practice though, the better the finish that I have been able to get, up to a point. I just don’t enjoy turning 4130 steel all that much, and it would seem 4130 steel doesn’t like being turned by me either, certainly not as much as aluminum.

One of the design problems that I have encountered with my lathe, is that the speed at which the automatic feed moves the carriage along cannot be changed, and it is determined only by the gears being used. Because of this coupling (good for cutting threads), increasing the chuck’s rotational speed also increases the longitudinal speed of the automatic feed, and produces a lot of excitement, but unfortunately not a better finish. 

So, I have been slowing the feed down by hand-cranking the carriage (longitudinally), which is a big no-no for smoothness of finish, but it is still better than what I’ve been getting with the auto-mode to date.

I also have an occasional tooth skipping issue with the auto-feed, that I have been able to reduce, but not eliminate, by throwing some lithium grease at the problem, but I think I have finally narrowed down its cause. This skipping has ruined a few parts already, by happening during delicates cuts, and forcing the tool to dig deeper into the part. 

It would appear that there’s not enough contact in the rack and pinion mechanism, creating hesitation in the feed, as well as the skipping. The cure should be to mill down the top of the auto-feed casing, to allow the geared unit to ride higher in the carriage, and engage the rack gear more fully.

While on the subject of modifications, I created a small cover for the hand-cranking mechanism. These greasy gears were totally exposed to the metal shavings, and would routinely attract and capture them like a magnet, then chew them over and over, causing wear and tear, as well as difficulty in hand cranking.

Housing with gears removed

Drilling hole #1

Drilling the same hole through the cover and spacer (without moving the drill)

Threading by hand with help from the drill press

First screw is in!

Process repeated twice more

Finished cover

This mod was cheap, using only leftover parts, and has performed flawlessly, and I no longer have to worry about cleaning those gears again.

By the way, that vise no longer looks so big anymore, and it is a real pleasure to use.