Set-based INSERTS Rather Than A Loop

I have a table with a series of rows for period 1 - these always exist

drop table tblmain
create table tblmain (period int, rfreq int, pfreq int)
insert tblmain (period , rfreq , pfreq )
select 1 , 1 , 1
union all
select 1 , 1 , 3
union all
select 1 , 1 , 6
union all
select 1 , 3 , 3
union all
select 1 , 3 , 6
union all
select 1 , 6 , 6
union all
select 1 , 6 , 12


select * from tblmain
period rfreq pfreq
1 1 1
1 1 3
1 1 6
1 3 3
1 3 6
1 6 6
1 6 12
*/


I need to do a whole lot of inserts with incremented period values up to and including
a number assigned in a different table, FMaxes based on JOINing the two tables on the rfreq column


CREATE TABLE FMaxes (RFreq INT , MaxFINT)
insert FMaxes (RFreq , MaxF)
select 1 , 5
union all
select 3 , 3
union all
select 6 , 2


select * from FMaxes
RFreq MaxF
1 5
3 3
6 2


Ive been scratching my head for hours trying to figure out a set-based approach rather than a loop
solution which I could produce

The desired result would be inserts from period 2 onwards - result set below



select * from tblmain

period rfreq pfreq
1 1 1
1 1 3
1 1 6
1 3 3
1 3 6
1 6 6
1 6 12

2 1 1
2 1 3
2 1 6
2 3 3
2 3 6
2 6 6
2 6 12

-- no period 3 or higher for rfreq value 6 because table FMaxes holds an MaxF value of 2 etc
3 1 1
3 1 3
3 1 6
3 3 3
3 3 6

-- no period 4 or higher for rfreq value 3 because table FMaxes holds an MaxF value of 3 etc
4 1 1
4 1 3
4 1 6

5 1 1
5 1 3
5 1 6

Thanks in advance