Does this sentence phrased correctly and effectively?

[Puellamagi]

The sentence:

"A scarlet haze covered the crucibles while their shafts stretched upwards, like sharpened arrows, to the cross vaults of the ceiling."

I have a question about additional allegory in the second clause: "like sharpened arrows" do I have do separate it with commas from the main body or not? And if it is placed in the right position in the sentence?

[Phil Istine]

The sentence:

"A scarlet haze covered the crucibles while their shafts stretched upwards, like sharpened arrows, to the cross vaults of the ceiling."

I have a question about additional allegory in the second clause: "like sharpened arrows" do I have do separate it with commas from the main body or not? And if it is placed in the right position in the sentence?

When writing a story, sometimes it's better to not judiciously follow the rules of grammar if a better effect can be gained by putting them aside temporarily.

I would probably leave those commas in if leaving the sentence like that, but there may be a case for removing the first one of the pair if you want it to flow more. It's hard to tell what is best without the context of surrounding paragraphs.

Would it work to remove the simile completely and use "spiked" or "arrowed" instead of "stretched"? That way it might add a little power to the scene by introducing a stronger verb.
As always, your piece so your choice.

""A scarlet haze covered the crucibles while their shafts spiked/arrowed upwards to the cross vaults of (in?) the ceiling."

Arrowed might imply motion, but context will tell a reader that this isn't the case. Spiked? I like arrowed slightly better.

Sleep on it

[Olly Buckle]

The 'rules' say that you put commas around a subordinate phrase, that is a phrase that can be taken out of the sentence and it will still make sense as a sentence, so yes, 'Like sharpened arrows' is a subordinate phrase. Having said that, Phil is dead right, the rules only apply if you want them to, if it flows without pause in your head when you read it (And I could see that in this context) why not leave them out? Rules are made to be considered.

PS You blew it a bit on the title 'IS this sentence correctly ...', or 'Does this sentence sound correctly phrased and effective?'

[bdcharles]

The sentence:

"A scarlet haze covered the crucibles while their shafts stretched upwards, like sharpened arrows, to the cross vaults of the ceiling."

I have a question about additional allegory in the second clause: "like sharpened arrows" do I have do separate it with commas from the main body or not? And if it is placed in the right position in the sentence?

It is grammatically correct. However it is stylistically a little less common (I think typically there would be zero commas in this sentence), but you can use that to set a certain tone and voice, one which perhaps emphasises the simile (the arrows), and is perhaps a little cautious as indicated by the two pauses.

It works, for me - it has personality. It just needs to be the right personality. If it carries on in this sort of vein, it reads like something I would very much get into

[Matchu]

Full stop. Remove ‘while’ and remove ‘upward’ and ‘sharpened’. Replace ‘to’ with ‘toward.’

Arrows are sharp already, unnecessary...

[Olly Buckle]

I do wonder about shafts on crucibles, they are usually squat and round to retain as much heat as possible, and smelting under a wooden ceiling doesn't seem right?

[Puellamagi]

Action is settled in the Lonely Tower, which stand above an infinite Abyss. The Tower is gothic kingdom of industry, so everything is placed in the closed gothic halls of stone and works on its own. About sharpened shafts: it is a stylistic choice, i want to create an image of gothic architecture maybe at the cost of factual rationality.

[Puellamagi]

To provide the sentence with a context. There are two paragraphs that includes it:

In her visions, Alle stalked the Lonely Tower for the Core on its top. The Core had a source of all meaning, and she looked for a lost reason to live. The Tower was a machine realm, a gothic kingdom of industry. Here, power plants hummed, and air pumps clattered in the halls of stone. She listened to their melody, which was her beloved. The road seemed familiar but always led to the wrong place, and Alle had a hard time finding the right way. Yet, she did not give up and searched a path to the pinnacle.

Alle found spiral stairs that coiled around the Tower like a helix. She climbed up its iron steps and entered the foundry level, where blast furnaces melted an ore. Kilns surrounded the stairwell that rose to the top of a vast dome, which roofed the mold factory. A scarlet haze covered the crucibles: their shafts arrowed towards the ceiling’s cross vaults. Instead of blazing heat, Alle felt only a pleasant warmth as the stoves lacked the fuel and cooled down, aborting the hot blast. As a result, black smoke flowed out of the smelters.