QCTP - T Nut

You dont want that T nut to be a press fit; you need a close sliding fit. Also, make double sure that when its pulled up tight there is still a little clearance between the top of the T nut and the bottom of the tool post.

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Too tight of a fit and you run the risk of cracking your cast iron compound mount. Also, make sure that the top of the T-nut is below the top of the compound. You want the QCTP pulling down onto the compound, not the T-nut.
 
i would agree that the t-nut should slide relatively free.
i'd suggest removal of the T-nut and removal of the offending metal on the T-nut

if you take a sharpie, or other layout fluid, and ink up the nut edges and the step you cut in
then insert the nut into the compound rest as far as you can by hand and remove the T-nut
observe the parts that are now missing ink, that was there before
these are the high spots.
a few strokes with a file will reduce their height.
repeat the ink up process and re install the t-nut
repeat until the nut slides freely!
 
actually it wasnt far off, i lifted slightly as I had allowed a little vertical movement, and it slid straight through, surmising that it was the corners that were the issue i chamfered the bottom edges, and it was a perfect sliding fit.
 

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Grendel said:
actually it wasnt far off, i lifted slightly as I had allowed a little vertical movement, and it slid straight through, surmising that it was the corners that were the issue i chamfered the bottom edges, and it was a perfect sliding fit.
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That is what you want. A perfect sliding fit, with the nut completely beneath the surface of the compound side. Then you aren't putting any stressor larger than normal on the compound. Kudos!

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On a lathe I picked up second hand, the t-nut hadn’t been finished to the same depth on each side. Not enough difference to see by eye but definitely with a caliper. As a result when tightened the bolt through the toolpost leaned off angle a bit, and caused the qctp to wedge and not easily come loose when the top nut was loosened. Took a bit of headscratching to figure it out but fixed easily in the mill once spotted.
 
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