Pm 1022 Improvements?

[7milesup]

I attempted to correct an error on my PM1022 lathe the other day, and in doing so, created an even larger problem. I swear this only happens to me. Like trying to dig a well in sand. The deeper and faster you dig, the more sand that just falls in on you.
The cross slide has an indexing mark scribed into it referencing the tool post angle. On my lathe, that index mark was about 1.5 degrees off, and it drove me nuts every time I looked at it. So I figured I would carefully grind it down a tad and fill it it with my TIG welder. What I ended up with was a mess. Apparently there is contamination in the casting, or it is some sort of bizarre alloy, that causes the weld to be porous, no matter how well I clean the casting. My weld area has gotten larger and larger trying to fix an issue from the previous weld. Anyhow, I feel that that part is probably toast at this point.

But, this also has me pondering what else can be done to improve the lathe. (I know what you are thinking..STOP! )
For example, there was a lot of slop (backlash) in the cross feed lead screw due to the cross feed nut. There was supposed to be an adjustment on it, but it was already broke when I got the lathe (not Matt's fault). So today I milled it down a little and screwed an acetal (Delrin) piece to the back side with a hole in it to take the slop out. But this made we ask "Are there better lead screw systems out there? I know ball screw are used on CNC machines, but what about a small lead screw like the cross slide? What other thread system could be used?"

Are there any upgrade/improvements for the cross slide itself?

Would a bunch of time spent hand scraping the cross slide, and tool post ways, significantly improve the operation of the lathe?

I assume that the cross slide gib bearing surface is the flats of dovetail, and not on the "points" of the gibs? I ask that because I discovered after taking this thing apart the gib is really messed up (not even end to end, etc.).

Lastly, just curious what the designation of this lathe is? I know it is similar to the Craftex lathes, but does it have a designation like Seig does with their mills (X2, X3, etc.)?

Please note that I have been very happy with PM and Matt, and these issues were either 1.) created by me, or 2). Matt would be unaware of some of this unless he tore every machine down.

Thank you

 

[tmarks11]

Cast Iron is notoriously hard to weld.

Most cast iron forgings (your lathe included) has a lot of bondo under the paint to make it look nice.

I would just grind down your weld attempt, lay a coat of bondo over the top, sand it down, etch a line in it and paint it. Then blacken the etched line with a permanent marker so you can see it.

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Usually the cross slide nut is a split nut with an adjustment screw through it to allow you to tighten up the two sides to get rid of backlash. You could always make a new one that is like that.

Alternatively, google "moglice leadscrew nut" for another alternative (diy epoxy lead screw nut insert to give you a zero backlash solution).

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Handscraping on a lathe? I would say no. The funny thing about a lathe is that due to the geometry of the cutting point vs the workpiece, a small variation in height of the cross slide doesn't have a huge effect on your cut quality/accuracy. And any variation in the z-axis is probably due to a leveling problem rather than the casting not being straight.

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Name of Lathe? It isn't built by Sieg. Grizzly was the first to import this class of machine as the G0602, so I guess you could call it a "G0602-like machine". Weiss sells machines like this, but as Matt is quick to point out, Weiss is just a reseller who labels machines purchased from various factories in China, not actually the name of a manufacturer.

 

[7milesup]

Hi Tmarks.
I have attached a couple pictures for reference. I also did a search for the Moglice leadscrew nut solution, but I actually like my method of utilizing Delrin for the nut. Delrin is self lubricating and it has significant breakout strength. It can be formed around threads by heating the threads to about 300F. It also machines wonderfully. I guess what I was curious about is there a better thread for a cross slide? Why an ACME thread?

As you can see in my pics, the area of my weld is free of contaminants. I don't think I have ever had a weld turn out so crappy though. I'm hoping Matt has a new cross slide I can buy, because if I had a problem with my index mark, my weld is going to be a problem. LOL

 

[tmarks11]

Ouch. I didn't realize that you were trying a weld on the cross slide itself. Ever welded on cast iron before? I haven't, but I have heard from a number of sources that it is difficult. Did you use a nickel rod? If you do get the weld to look decent, you still should surface grind the cross slide.

Acme screw is used for high load and high friction, both of which are ideal on the cross slide, since you don't want the cutting forces to back drive the lead screw and allow the table to move.

Ball screws are used in CNC due to zero backlash, but aren't good for manual machines because the lead screw is easily back driven. You have to engage the table locks every time you reposition the table.

 

[7milesup]

Well, hopefully Matt has a new cross slide in stock for a reasonable price that I can pick up from him. Then I can hone my cast iron welding skills on the old one. LOL. Actually, I have read that a stainless filler rod will maybe work, but yes, a nickel rod will certainly help. Problem is, a pound of nickel rod probably will cost as much as a new cross slide.
As you mentioned, I was hoping to build it up enough that I could take it over to a guy that I know that has a surface grinder and just take a couple thousands off of the whole thing, but not going to try if the interior of my weld looks like that.

 

[tmarks11]

Problem is, a pound of nickel rod probably will cost as much as a new cross slide.

Ouch! $48 for a point of nickel rods. Not cheap.

https://www.arc-zone.com/nickel-82-tig-rod-ernicr-3

Another option is you could "TIG" with a silicon bronze rod. This would essentially be brazing (since the rod melts below temperature of the steel), but it flows nice and if you build it up proud and surface grind afterwards, it should look okay. At $13 a pound, this might be worth try.

The Bronze can load up the grinder wheel, so it might require a lot of dressing to get the job done.

 

[lpeedin]

Did you happen to talk to Matt about buying a new cross slide? I only ask because I have a situation with my 1127VF-LB where I am now in need of a new cross slide. I emailed him late last night when I discovered the problem. I am sure I will hear back from him ASAP.