When to Cut a Dora
One of the hardest recurring questions is when to discard a dora.
Too early is bad, but too late is bad too.
When the Dora Is a Value Honor
The most troublesome kind is a dora that is also a value honor.
If you ask me for the best timing to discard it,
I would answer: on the very first discard, or when you reach tenpai.
Why is the first discard good?
Because the tile that is least likely to be pon'ed or ron'ed is your first discard.
For example, suppose you are in first place in the South 4 hand and your opening draw looks like this:
Example 1
Tsumo 
Dora
You should discard 
on the very first turn.
This is a hand where simply winning is enough, and it looks likely to settle into Pinfu, so there is no need to cling to the dora.
However, situations where “just winning is enough” are very limited.
In most cases, simply pairing the dora already raises the value sharply,
so most of the time you will keep it for points.
Example 2
Tsumo Dora
Discarding the dora from a one-shanten hand like this is completely wrong.
If the dora pairs up, it can become your head and even bring mangan into view.
"Holding a dora too long is dangerous..." is not a valid reason.
That is simply the wrong way to think about it.
If the dora gets pon'ed, every tile at the table becomes dangerous anyway.
For this hand, the right time to cut the dora is when you reach tenpai.
The dora should become your riichi declaration tile.
Theory Summary
Discard your truly useless tiles before you discard the dora.
The kind of one-shanten shape where you may start discarding the dora is when you draw 
.
☆ Tsumo
If the hand becomes a one-shanten shape waiting on 
, then cutting the dora has real value.
It is also worth considering if you draw and gain extra shanpon acceptance.
☆ Tsumo
If the dora is relatively easy to cut, or if you absolutely want to fight for the win,
then you may let the dora go here.
More concretely, cases like these:
- You are dealer
- It is still early and nobody has called yet
- The dora is already visible on the table
In situations like these, cutting the dora at one-shanten can be fine if the conditions fit.
However, if you still have clearly useless tiles and discard the dora first anyway, that is still sloppy play.
Other Cases
Personally, I am not the kind of player who treasures dora too much.
If I have to narrow my acceptance just to keep the dora, I usually will not keep it.
Example 3
Tsumo 
Dora
With a shape like this, I would cut the dora without hesitation.
The hand is far wider, and it still has routes to Pinfu, Ittsuu, and Iipeikou,
so I do not feel any need to keep the dora.
Example 4
It is not impossible to use both dora,
but if you play with winning speed as the priority, discarding the dora gives the widest hand.
(See the tile-efficiency chapter.)
With draws like 
, the hand becomes a Pinfu one-shanten;
and when you look at the score situation for all four players, this is not a spot where a huge hand is required, so you should cut the dora here.
In most one-shanten situations, I think it is correct to prioritize hand width over dora.
Of course, if cutting the dora is highly likely to deal in, that is a different matter.
Original Japanese page: http://beginners.biz/dora/dora04.html