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I'm going to be doing some screwing/unscrewing of screws that provide both a utilitarian and aesthetic function, so I'd like to protect the painted coating on the heads as best I can when I remove and re-insert them.

These are Torx (T45) rather than Philips head, so fortunately the heads are less likely to strip or be damaged than they otherwise would be. But having never used an impact driver before, while also having stripped plenty of Philips screw-heads with regular screwdrivers in the past, I am wondering what the best option for this job would be.

In short: in general, which is gentler on the coatings of screw-heads: regular screwdrivers, or impact drivers? (Impact drivers sometimes shearing off screw heads in the case of overtorqueing notwithstanding)

Addendum (added from comments):

I'm doing some automotive work on a new vehicle. The bumper has a bunch of T45 bolts on it that are removable to add / remove accessories, and I'd like to keep them in the best shape possible, both for aesthetics and to prevent rust. While I'm specifically asking this question for this project, knowing whether or not impact drivers make screw head stripping less likely will help me decide whether or not buying an impact driver is worth it for the few projects I do.

 

The screws in question are actually just going through the sheet metal of the bumper and aren't structural - but yes, in fact the "regular screwdriver" I was originally planning on using actually will be a socket wrench with a T45 socket.

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    A T45 Torx is 0.308" (almost ⁵⁄₁₆ in) across the points. This makes a 'regular screwdriver' a little underwhelming for bumper bolts which are likely grade 8 and torqued into place. Short of an impact gun (air or electric), have you considered a T45 socket bit for a ¹⁄₂ (preferred) or ³⁄₈ drive socket wrench? – user109695 Jan 13 at 1:51
  • The screws in question are actually just going through the sheet metal of the bumper and aren't structural - but yes, in fact the "regular screwdriver" I was originally planning on using actually will be a socket wrench with a T45 socket. – Dee Eye Why Jan 13 at 3:15
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That’s funny , sorry but force is needed to break the screw loose , an impact if at the wrong angle will cause problems as a hand held driver will. If there is paint both will damage the paint. But a t45 is large and if the bit is fully inserted and perpendicular there is really no difference as an impact only hits hard enough to get the screw moving. Once the breaking force to remove the screw is achieved there is no real difference except the impact will be faster.

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    Not sure what the OP is working on, but when it was originally assembled an impact was probably used so it's probably a bit tighter than a regular screwdriver.+ – JACK Jan 12 at 23:48
  • I'm doing some automotive work on a new vehicle. The bumper has a bunch of T45 bolts on it that are removable to add / remove accessories, and I'd like to keep them in the best shape possible, both for aesthetics and to prevent rust. While I'm specifically asking this question for this project, knowing whether or not impact drivers make screw head stripping less likely will help me decide whether or not buying an impact driver is worth it for the few projects I do. – Dee Eye Why Jan 12 at 23:54
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    I have never stripped a torx. I have broken a few bits and snapped the heads off smaller screws but the torx design is really tough I would not worry about stripping them out as long as you make sure the bit is in the hole. – Ed Beal Jan 13 at 14:30
  • You haven't stripped a torx? I mean yea they are tough but never? How about a square bit used for concrete board? If there is a screw type I have stripped it. – DMoore Jan 13 at 20:03
  • No a torx in my pouch is getting thin after more screws than I can count , it was getting close , but that bit that drove hundreds of deck screws , maybe a thousand I don’t know but I usually loose them ,, star bit / torx. Absolutely not a square that I hate square bits as they are crap and I have said this since my apprentice years in the 70’s. I will put up a thousand point bounty for any one that can prove a square bit can make it even close to that of a torx, I would say 50% on a diy sight would be a good wager! Square sux , pozzi is better and torx is the best. – Ed Beal Jan 14 at 3:16
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Given the addendums to your question culled from comments, I would recommend a T45 Torx socket coupled with a ³⁄₈ drive socket wrench.

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You can use the heel of the palm of one hand to hold the socket firmly in place while applying rotation with the other hand.

If the female torx bolt heads have enough paint that a solid socket-to-bolt connection is compromised, use a soft or 'dead-blow' mallet to seat the male torx head into the female bolt head before attempting removal/reassembly; even taking the time to remove stripped paint accumulated in the bottom of the female torx. A true and solid 'seat' between wrench and bolt is more important than preserving the original paint. There are many 'touch up' products available; I've found the right shade of nail polish a cheap and widely available option.

With all that said, an impact gun would be overkill unless it was in the order of an 18V ¼" drive model and even with that, the main issue becomes the paint that is clogging the female torx.

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To answer the essence of the question (regarding which is gentler), undoubtedly the standard driver. The reason is control. You have no real control over how much torque is applied via an impact driver--it just does its thing. With a standard driver you can both modulate the motor force (assuming a modern variable trigger) and set a clutch, if available. Therefore you only apply the force necessary to do the job.

The key to either scenario is tool usage technique, through. Straight-on alignment and adequate engagement pressure are critical, as is the condition of the driver bit. Either tool will mangle screws with poor technique, and damage is more likely with worn bits.

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Making sure the bit is properly engaged is the first step - square and fully seated.

Then a screwdriver with the relevant torque setting is usually sufficient - only resort to heavier tools when needed ie when theycare too tight or seized.

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The Torx T45 drive is beefy enough that it's pretty safe unless the head of the screw is very very shallow, so you'll probably be fine any way you go.

That said, an impact driver is far less controllable than a drill / driver. Once it starts hammering, the impact applies torque in bursts, not continuously. It's harder to control the torque by partially pulling the trigger.

Most drills have a torque dial on them. You can use this to make sure you don't overtorque things. You can work your way up one or two clicks at a time if you want - you could tighten everything with the drill on a low setting to get them seated something like finger tight, then adjust the dial up a few clicks, re-tighten everything, and repeat until it's at the desired torque.

Of course the safest thing is to not use a power tool, drive them with a ratchet, short extension, and T45 socket.

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I am going to heartily disagree with some of the other answers with an asterisk *.

Yes I agree you have more control with a standard drill. Yes an impact drill does not allot you the ability to adjust torque. I agree with the other sentiments on this - I am sure there is science and facts that back this up.

However asterisks alert (*)...

  • If I have a situation where my screw heads are getting damaged and the screws are getting in (so it isn't that the screws are "stuck). Examples of these are binding cabinets together or the perfect example is putting in cement or hardibacker screws into wood framing.
  • If you can keep a 90 degree angle with your screw.
  • If you can apply a good deal of pressure for at least a couple seconds.

I will take an impact driver every single day. In fact if I am working on something this is the number one reason I go out to get a tool - my impact driver (losing screw heads).

Using an impact driver like this is an art. You get your angles aligned, get your pressure on it, and give it a tap (varies by model and some you give a half squeeze). Rinse and repeat. You might align yourself 3-4 times for a screw, but if it starts going in like butter you just let it do its thing. Again I am not telling you to hammer the impact driver, if you don't have a good touch for it - and it isn't rocket science - then yes the impact driver will eat up a screw head.

The issue with regular drills is that when you slow them down and start applying a lot of pressure they stick while the motor is still trying to move. Either you will keep applying pressure hard and slightly dial up the motor or you will end up losing pressure over time - and bam the same thing happens - your bit slips on the screw head.

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