Thinking about filing left side of front sight. Any recommendations on what type of file to use? Any other ideas/options? Is there an adjustable after market site for said revolver?
Thanks,
L.P.

Barrel canted?

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Ret. LE, FA Instr, S&W Armorer

Have somebody else shoot it . . .

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Wisdom comes thru fear . . .

Both of the above comments are two considerations that should be given serious thought when it comes to the 642.

Before doing anything, do some diagnostic dryfiring. By that I mean (lawyer-like warning for dumba***es) make double, triple, absolutely sure it's unloaded. Then pick a small target a short distance away (I like a light switch), take careful aim focusing on the front sight, and then dryfire while concentrating fully on that sight. Observe which way it moves as the shot breaks. Assuming it does move (and it usually does), adjust your grip and/or finger position to eliminate the movement.

Only if it stays dead-solid in position throughout the shot and still shoots off should you even consider doing anything more.

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Pisgah

First, DO NOT file on the sights except if the gun is shooting low. All you will do is mutilate the sight and it will not fix the problem anyway! At a range of 10 yards, even if you remove 1/4 the thickness of the front sight, ca. .015", it will move the bullet strike only 3/4" with a 1 7/8" barrel. 1/2 the sight thickness will move it ca. 1 1/2". Just changing ammunition can make more difference than this! (Yes, changing bullet weight, etc., can change windage!)

Second, just how far to the right is it shooting? If just a few inches it is within S&W specification and you should simply learn to "hold-off" slightly to the left.

Finally, be absolutely sure that the gun is at fault and not you. How much experience do you have with handguns? I suspect not much. How you hold the gun, how you apply pressure to the trigger, and how you see the sights all contribute to where the gun will shoot for you. Often you need to make adjustments in hold, etc. with a fixed-sight revolver so it will shoot where it is supposed to.