PM940V-PDF, It broke... Be Aware... (FYI Precision Mathews)

verbotenwhisky

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So, I wanted to fine tune the tram on the head of my mill. I loosened the three bolt, adjusted it then as I tightened the lower bolt, M16x2.0 when I hit 20 Ft/Lbs of torque I heard a ting... Me: "what was that? did you hear that?" Wife: "yeah, What was that?.." I reached up under the head after realizing the bolt was no longer turning and pulled the piece of it out attached to the nut... Wife: "thats not suppose to come out".... :rolleyes: ... Me: "Nope, not like that"...:confused: ....

Wife: "Now what?"... Me: "we have to take it apart to replace that"...

20240511_191613.jpg
20240511_191613_1.jpg


What broke and the surprising way it broke:

20240511_191721_1.jpg


What it is suppose to look like...

20240511_191707.jpg


My wife said, "how long will it take to get the part?" and my answer was "I have 4140, I'll make a new part".. I have to admit I forgot to take a picture of the new bolt but it looked a great deal better than the one in the photo. Take a look at the one in the photo, see the dish in the end of the bolt? Additionally there should have been 2 long bolts and 1 short but the one on the right side was a short as was the one on the bottom which broke, the one on the right, when tight, didn't fully engage all of the threads in the nut, there should have been at least 2 threads above the nut.

With all of this said, any of you Precision Mathews guys feel like chiming in on this? that break is like this bolt was 2 parts not one, clean, not a shear. Take a close look at the head it appears as though the case hardening pealed away from a base material, very odd....

PM940 guys, be aware if you are tramming or otherwise adjusting your machines....
 
Those should really be forged fasteners but I'm sure they are not- probably made from two pieces like you guessed
I'm wondering if you can buy some like that but much stronger and one piece?
 
Those should really be forged fasteners but I'm sure they are not- probably made from two pieces like you guessed
I was very surprised when that one snapped, main thing I wanted to do was raise some awareness I suspect the 940's are not the only mills where these are used. I am seriously thinking about pulling it back down and replacing the other 2 bolts, they do not look good and really do not inspire confidence.
 
yea some JB weld and it will be as good as new lol.
sorry about the issue, but at least you can fix it.
 
Well, at least it was something easy to fix or replace. I'd probably go looking for some proper, forged replacements, though I'm sure your 4140 replacement is in every way superior to what it replaced.

It's hard to imagine a two-part fastener, meant to be in tension, designed in such a way, but it sure does look that way.

GsT
 
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