Grace had previously stopped five penalties in three shoot-outs to help the Hellenic League Premier Division club maintain their push for a first-ever final.
The keeper saved two penalties in a second round win at Newhaven in December before returning from lockdown to stop two more in the fourth round success at Fakenham on April 10.
Grace then made a crucial save after the fifth round shoot-out against Hadley had ended goalless - Binfield winning 5-4 on spot-kicks.
He failed to keep out USP’s first three penalties, all confidently converted by Andrew Todd, Tom Jeffes and keeper Tom Price. But he then saved from Cam Quirke and Jack Chandler as US’ elation - they led 3-2 after Price saved from Sean Moore - quickly turned to despair as The Moles claimed a 4-3 shoot-out triumph.
Chandler wasn’t initially down to take one of the five penalties as boss Glenn Turnbull had hoped to keep the running order the same as in the fourth round penalties win against Christchurch.
But that plan had to be ripped up when Dec Seiden - the side’s regular penalty taker who went second against Christchurch - was substituted in the second half.
Seiden was withdrawn as US sent on midfielder Jordan Pile in a bid to stop Binfield – drawn away in every Vase round - piling on the pressure.
Skipper Jeffes was moved up from fourth to second in the spot-kick order, with Todd and Price again at numbers one and three.
Quirke and fellow sub Elliott Turnbull were fifth and sixth to take penalties in the original running order, and so Quirke - higher up the order - was brought on in the closing stages as US’ final change.
Price gave US a 3-2 shoot-out lead when he saved from Moore. But Quirke’s effort was kept out one-handed by Grace, who then had an easier save to make getting down to his left to stop Chandler’s effort.
That set the stage for Binfield sub Jack Broome to step up and fire his side to a May 22 final date against Warrington Rylands - shock winners over holders Hebburn - or Walsall Wood.
Turnbull revealed his pre shoot-out pep talk: ‘I said to the boys, ‘if I had offered you penalties to get to Wembley you’d have bitten my arm off. You’ve been smashing them in in training, go and do it again.’
‘In three weeks of training, literally nobody had missed (practicing penalties).
He explained: ‘I moved Jeffers up to two because I wanted to keep Pricey at three. The thinking was if we could score the first three that would take some of the pressure off the other boys.
‘Cam said when he was getting ready to go on that he was just going to smash his penalty. Jack’s was a bit more tentative, I think nerves got the better of him.’
Turnbull was remaining philosophical after seeing US go so near to realising their Wembley dream.
‘You live and learn, and hopefully they will grow from it,’ he said.
‘Some of the boys were crying afterwards and to be honest that’s all I wanted to do. But I saw it as my job to be positive and try to pick them up.
‘I told them we can’t dwell on this, we have to go again, we can’t let this define us - even though I just wanted to curl up and do what they were doing.
‘Seeing people like Sweeney and Tom Jeffes in tears was hard to see.’
The manager also felt for his unused subs - son Elliott, Dan Sibley, Jay Ripiner and Frankie Paige.
‘I think it was harder for the boys who didn’t get on,’ he said.
‘Elliott did so much work last week, he helped organise the new kit and tracksuits, he organised the commemorative balls.
‘The players like him, Sibbers, Frankie Paige, Jay Ripiner, they didn’t get on and to be honest that’s hurting me the most.’
US defeated six higher division teams in winning through seven Vase rounds, plus Millbrook who won 10 and drew one of their step 6 league games in a pandemic-curtailed campaign.
‘Ordinarily, you win the FA Cup with six wins. We’ve played eight games, seven against higher division clubs and not lost one in regulation time,’ Turnbull commented.
‘That’s hard to take.’