Branch secretary Dean Hall has previously said he welcomed the chance to clear his name given more than three months had passed since many of the claims, some of which were based on third party hearsay evidence, were first made.

He declined to comment on Tuesday, saying it would not be appropriate to speak before his appearance.

ACT CFMEU organiser Johnny Lomax will also give evidence between now and the weekend.

Mr Lomax had been scheduled to testify in Canberra in July. That appearance was deferred following his arrest on a charge of blackmail, while the commission was sitting in the territory.

The charge, condemned as a political stunt by the CFMEU, was effectively dropped last week when police said they would not be bringing forward evidence to support it when the matter returns to court on October 19.

Mr Lomax is likely to be questioned over a covert phone tape of a conversation between himself and a Canberra builder, whose name has been suppressed, made on May 22 this year.

Mr Lomax told the builder he was with the assistant branch secretary, Jason O'Mara, who was not happy at the small number of union members among the man's workforce.

He said: "My bosses are very upset and I can't control that. We'll be delivering some action unless we get this meeting [to discuss generating memberships] sorted out straight away".

Asked what sort of action, Mr Lomax said: "One would be my suggestion of ripping up your EBA ... without the EBA you won't be doing any work on commercial sites."

Mr Hall is expected to be quizzed over a range of allegations including whether or not he had been aware former organiser Halafihi "Fihi" Kivalu had been allegedly taking payments from contractors in exchange for promises he would find them work.

Mr Kivalu has been charged with two counts of blackmail in relation to payments in excess of $100,000.

The royal commission was also told Mr Hall had browbeaten a WorkSafe ACT inspector, Joseph Bartlett, into closing down a concrete pour against his better judgment.

Advanced Plumbing and Drains owner Jason Hooper, who refused to sign a CFMEU EBA, said he had been told if he "carried on" the way he had been doing Mr Hall, a former history teacher, would deal with him "the old fashioned way and meet me in the paddock".

The warning had come from the Master Builders Association, not a union source.

An ACT police officer, Detective Sergeant Mark Battye, said that when he arrived at a building site where the CFMEU was interrupting a concrete pour in December 2012 Mr Hall had acted aggressively, encroaching on his personal space.

A succession of witnesses over the past three months accused Mr Hall, Mr Lomax and other CFMEU officials of using safety as an excuse to interrupt concrete pours and disrupt work sites; claims the union has repeatedly denied.

Mr Hall has previously cited the ACT's poor safety record, which culminated in four deaths on Canberra building sites in 2012 and 2013, as proof local employers were willing to cut corners to reduce costs.

Under cross-examination by the union's lawyer, Canberra builder Samuel De Lorenzo told the commission hazards could always be found on a building site and that it was a question of managing risk.

Builders also said they were pressured into taking out "ghost memberships" in the CFMEU as well as paying fees for any flesh-and-blood employees who were happy to be in the union.

Mr O'Mara, told the commission organisers were expected to generate 125 new memberships a year.

"We [do] have a quota," he said.