I think I have Problem!

[COMachinist]

I was doing small project for my John Deere compact tractor and this happened.The machine us the PM12x36T precision lathe.
I was turning a piece of 4in 1144 down to a 2.335dx3" tail stub and I took too big of a bite?? .050 and I heard a loud, crack and hit the big red button. Started looking and sure enough the compound top slide was cracked. Removetaild it and it came apart. Did not even break or chip the insert. It just popped! Any ideas if I can get new top for the compound or what should I do. I knew I should have got the 13x40

 

[Asm109]

Call PM and get your visa card ready.

 

[ChazzC]

Would not have thought that the compound would have cracked like that leaving the insert untouched unless there was a flaw: it would be worth discussing with PM, even offering to send the pieces to them.

 

[RJSakowski]

Take a look at the break to see if there is evidence of an older crack. It seems very unlikely that a break like that would occur unless the the top slide was extended so the bottom ways couldn't support the top. Another possibility is that the tool post was threaded too deep so that it was applying pressure to the bottom of the tee slot although that usually ends breaking one of the ears.

 

[Reloader1776]

Take a look at the break to see if there is evidence of an older crack. It seems very unlikely that a break like that would occur unless the the top slide was extended so the bottom ways couldn't support the top. Another possibility is that the tool post was threaded too deep so that it was applying pressure to the bottom of the tee slot although that usually ends breaking one of the ears.

I would guess the tool post bolt was threaded too deep as well.

If you get the part under good light, an existing crack area should show up darker/discolored a bit compared to the freshly broken surface.

 

[markba633csi]

Defect in the casting- piece of Planter's peanuts can in the melt

 

[projectnut]

The first thing I would check is the mounting stud and nut plate. Most quality nut plates will have the last thread upset so the stud can't continue to thread through it. The bottom side of the nut plate should have what looks like chisel indentations across the threaded hole. They should be deep enough to stop the stud from going through. If the indentations don't exist there is the possibility the stud has gone too far through the plate. If it did go through the plate, there should be some evidence on the cross slide. If the stud has gone through the nut plate, I would create indentations in the plate to prevent the stud from repeating the problem


Secondly, I would check the broken cross slide for evidence of failure due to poor casting, air pockets, hard spots or any other abnormal conditions that could weaken it. An .050" cut shouldn't cause the cross slide to break. I have been known to hog well over .125" on my Sheldon machine. It doesn't show any signs of distress let alone break.

 

[sdelivery]

I think it was a defective casting.
I think this way because I have serviced machine tools for decades and I have never seen results as shown in you picture.
I have seen many cross slides and compound slides that have been run into spinning chucks without braking the casting, there is generally some pretty ugly damage but not a broken casting.
I can see I'm the third picture where your tool post has extended through and rubbed a tell tail mark, this could have a bearing as others have pointed out.
See if you can get the casting otherwise make one, cast iron would be preferred but steel will work as well.

 

[55fairlane]

I have investigated several forging & casting failures, the trailing end of the t slot is where the "spallus" started. You have a a poor quality casting. A manufacturer defect. And now your left holding a broken machine. PM's customer service is good. They should offer you a replacement

 

[55fairlane]

You can also see oil wicking back up into the Crack at the dovetail. My guess, very poor casting & poor manufacturing