You call an all in in position with T8643. Villlain pats. Do you break your 10?

depends...

you have 19 outs (t, 9, 7, 5, 2) to make a ten or better. there are 47 unseen cards. so you will make a ten or better about 40% of the time. its actually a little less than this becouse the villain is probably holding at least two of your outs.

since its an all in situation you need to win half the time to break even (simplification, im guessing you put close enough to half the money in where this is true).

note that your ten is pretty good. if he has a jack low and you drew a jack your hand would beat his most of the time (you're just under a 50% fav to make a jack).

so this really comes down to reading his hand. you didn't describe the betting for us, so this is hard to guess at.

im pretty sure if the worst he would ever get it all in preflop with is a pat ten you need to break, i can say that much.

If you are in position and he draws one, you stay pat, if he stays pat, i think you need to break the 10. If you are out of position, i think you stay pat and keep your fingers crossed

Stacks matter. Playing styles matter. I probably wouldn't call an all-in with a raggy 10 unless I had the all-in covered with a lot of room to spare.

I see a lot of players jam pre-draw and then pat with garbage like a Jack or Queen. They're hoping, if you call, that you have something like a 9 or 10 and that their pat will tempt you to break it and risk pairing up... or they're hoping that you need to draw one and that you don't hit (which is strange because most of the time, a predraw shove indicates a pat hand as it stands). I also see players shove pre, pat and show a 7 or 8, so YMMV.

Against a LAGish player, if the all-in was small, I'd pat and make him show me a winner. Generally, though, I'm more careful about calling all-ins. I generally want a pat 9 in hand or better before I'll do it.

A decision like that would depend entirely on the player for me.

If he was very loose and aggressive and I decided to call with a fairly rough Ten then I would have probably already made the decision to stand pat. If he was more of a tight, conservative player, I would just muck the pat Ten pre-draw. However, if he was short-stacked then he could easily have a pat hand worse than a Ten or maybe even a good one card draw so I might call a more conservative player even then. But I am quite a tight player, so I would generally fold a pat Ten if the all-in raise was significant.