Perhaps Dickens does this so that we can understand Joes actions better, or at least dont view him too negatively when he cant protect Pip from Mrs Joe. In contrast to his gentle personality, he is a blacksmith, and therefore a strong man. Pip thinks of him like the steam-hammer, that can crush a man or pat an egg shell. He is likening Joe to a machine in the forge, giving Joe a sense of power. Although, crush is quite a violent word, suggesting Joe to be violent, which he definitely is not.
Perhaps Dickens included this detail to make us respect Joe, which is important for later on in the novel, so we dont just view him as a sweet-tempered man. But there is a sense of this good natured man in the word pat, it could potentially have paternal connotations. Perhaps this links to the image of the egg shell as well, as it is a fragile protector of life. Furthermore Joe could almost be seen as the protector of Pips life, as he saves him several times. Also egg shells can be strong, but have weak sides if they are put under stress, just like Joe has a weak side he cant protect Joe from Mrs Joe Gargery.
As well as this, there is the idea that Joe is in control, in the words can and or, he can choose which side of himself to be, strong or gentle. This is a very adult concept, but Joe can sometimes be very childlike. Joe cant deal with the idea of death, despite being a strong blacksmith. When Pip asks Joe if Miss Havisham died, he eventually replies she aint living. This is a very backward way of saying it, a way we dont normally use, showing Joes childish innocence.
He avoids the subject of death again, when Pip asks him if he had heard of Magwitchs death. Even though Joe never knew him personally, he avoids saying the words, instead he says he heard something or another in a general way in that direction. The vagueness of this statement is almost humorous, he cant even just say yes. Joe is unable to confirm a persons death, he just brushes over the subject, not fully acknowledging or possibly understanding it, like a child would. Another way Dickens portrays this childishness is through making Joe illiterate.
Pip writes him a letter, and all he can read is his name: Why, heres three Js, and three Os, and three J-O, Joes, in it, Pip! The exclamation mark at the end implies he is excited and proud that he has managed to read, and that he is wanting Pip to recognise his achievement, like a child would want their father too. This childishness makes Joe a lovable character, the reader wants to see him do well. Perhaps it also makes Pips behaviour towards him seem worse, from the readers perspective, as Joe is such an innocent character.
Whilst Joe may not have great knowledge or academic skills, he possesses something most of the other characters dont have, self-knowledge, he recognises he is illiterate and stupid. He tells Pip on two separate occasions that he is most awful dull. He is accepting of himself, he knows he is not the cleverest, in fact awful suggests that he thinks he is very stupid. Moreover, dull could imply many things, not only that he is stupid, but also that he isnt sharp. Perhaps this is a reference to him being a black smith, that he is like one of his hammers, only good for physically things, hes not sharp witted or clever.
Dull could also intimate that he thinks he is boring, perhaps why he struggles to talk to, or be in the presence of people in a higher class to himself, because he considers himself boring and unworthy. But this dullness does not stop him from being wise. Throughout the novel, Joe gives Pip many pieces of advice, for example if you cant get to be oncommon through going straight, youll never get to do it through going crooked. Joe, even though he is perhaps the most uneducated character (shown in the wording of the sentence) he can sometimes be the most wise and honourable. Because of this he acts as a hidden role model for Pip.
Not only is he honourable and wise, he understands his place: I am wrong out of the forge he tells Pip at their awkward reunion. Dickens suggests (through Joe) that people should stay in their class, and not aspire or try to move up; he argues for social immobility. Joe tells Pip that if he ever came back to the forge hed see Joe the blacksmith, there, at the old anvil, in the old burnt apron, sticking to the old work. Joe labels himself the blacksmith implying that he believes it is all he is good at. The repetition of old makes him seem experienced, as he has been doing it a long time.
There is also the idea that he clings or latches onto his work, in the word sticking, he fixes himself onto it so much that it has become how he defines himself. The fact that he feels himself wrong when not in the forge could be the reason why he cant talk to Miss Havisham: Joe¦ persisted in addressing me. It is like he cannot deal with the formality of he occasion, as he feels he doesnt belong there. Dickens humiliates Joe here, presenting him as a shy and awkward character, making the reader sympathise with him. This is another negative quality, helping to balance out the character of Joe.