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I am a widow and starting out in the world of DIY. I tried replacing several broken trellis panel fencing last year. I bought a 7.2V Bosch drill and used 3in screws to hold the panels onto the wooden posts. The screws did not penetrate all the way and have been left protruding. I wish to smarten up the unfinished job!

Did I need a stronger Drill? What type of drill would be advisable for small and larger jobs?

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Most low voltage drills are targeted toward hobbiests than anyone else, and a 7.2V drill is likely not going to be much use for driving screws. It will likely do fine for drilling holes, but there is generally a pretty strong relationship between voltage and torque.

If this is something you'll be doing enough to justify the purchase, I'd look for something 14V and higher from a reputable manufacturer (Bosch, Dewalt, Makita, and Milwaukee spring to mind). Avoid the cheap store brands or cheap imports (I'm looking at you, Harbor Freight), and read some reviews from websites or magazines that are aimed at contractors (I usually start at FineHomebuilding - they do a ton of tool reviews).

Finally, keep in mind that the majority of what you are paying for are the battery packs. This means that you can generally get better deals on tool combo sets than individual tools because they'll share batteries.

BTW, on your protruding screws you'll want to back them out about a quarter inch before setting them the rest of the way - it's easier if the driver isn't at full torque when you start.

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  • Thanks for your helpful advice, I will take heed regarding purchasing one of the more reputible makes, was thinking of Dewalt, as Ive seen one in action and will also check the reviews on FineHomeBuilding as suggested. – Patricia A Jun 7 '15 at 21:46
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Did I need a stronger Drill?

Perhaps not, often you can just lubricate the screws before driving them. People suggest soap, I've sometimes dipped screws in a light grease (which can leave marks on the wood). This really makes a huge difference.

Another alternative is to drill small pilot holes before inserting the screws. The width of the drill needs to be less than the full width of the screw threads.

If you are driving a lot of screws and wish to avoid these extra steps, I'd buy a stronger drill/driver.

What type of drill would be advisable

You might own a Bosch 7.2V screwdriver (model PSR7.2-LI) that has a torque (turning strength) of 6 or 10 Nm.

A 10.8V Bosch GSR 10,8 V-EC HX has a torque of 20 or 18 Nm.

A 14.4 V PSR 1440LI-2 has a torque of 17 or 34 Nm.

(The two ratings are usually for hard and soft materials)

You could buy a tool with a higher torque rating. Usually this is associated with a higher voltage rating (for battery powered tools). Bosch always provide torque ratings for this type of tool.

Remember that higher voltage tools are usually bulkier and heavier. smaller tools are often more convenient in confined spaces and less tiring for extended use.

It is usually advisable to buy a driver with an adjustable clutch (a turnable ring with numbers) that allows you to reduce the torque to avoid driving the screws too deeply (or from damaging the screws). Not all electric screwdrivers have this as standard but most do.

Emma's answer lists the basic types of tool available for this task. You don't need to drill into masonry so it is useful to distinguish between an axial hammer-action drill (mainly for masonry, but not especially good at that unless you buy a mains-powered or SDS-plus drill) and a rotary impact driver (advertised as good for driving screws into wood). See When would one use an impact driver versus a regular drill?

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  • Good call on lubricating the screws. I actually use wax - I usually grab a wax ring for seating a toilet and just stick a bunch of screws into it and pull them out as I drive them. It's super cheap, lasts practically forever, and works great. – Comintern Jul 23 '15 at 22:45
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The low voltage drills like the one you have are mostly good as a powered screwdriver for assembling flat pack furniture. This type of application usually already has a pilot hole drilled, so the drill doesn't have to work to displace material as it drives the screw. The key performance parameter that your drill is lacking is a high enough maximum torque.

For a short term, low cost solution (if you don't want to spend a bunch of money up front), you could try drilling a pilot hole for the screws. The pilot hole should be about the same diameter as the shank of the screw. If you want an exact size reference, you can use a pilot hole screw chart and look up the size of screw you're using:

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(Source)

If that doesn't work, you may have to buy a new drill. The newer 12V lithium ion drills are surprisingly powerful for their size, and are still rather affordable for homeowner uses. Comintern lists some good brands, but I'd also encourage you to look at Ridgid, a manufacturer who makes a good product at a slightly lower price point. This 12V drill packs a whopping 350 in-lbs of torque, compared to the 60-100 in-lbs your 7.2 drill likely has. (Note that it only comes with one battery, so you'll have to wait for it to charge when it runs out.)

If you're going to be doing a lot of drilling and screw driving, you could look into a combo pack as well. This Makita set comes with an impact driver (800 in-lbs of torque) and a drill (200 in-lbs of torque). The impact driver will be able to drive screws much faster, and in much tougher material than the drill will be able to. This kit comes with two batteries as well, so you won't have to pause work while waiting for one to charge.

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  1. Hammer Drill: good for drilling holes in masonry and stone.
  2. Percussion Drill: good for use with screw-driving jobs into metal and wood. It ensures the best performance.
  3. Drill Driver: good for drill setting for boring holes, or the driver setting for loosening screws.
  4. Powered Screwdrive: good for easy handling.

According to your convenience use any of above.

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Personally, I never use battery powered drills and would advise against them.

The drill bit should be the size of the screw minus the threads. In other words, if you filed off the threads of the screw, the rod left behind is the diameter the drill bit should be. Machinists call this the "root diameter".

In many cases you need to actually drill three pilot holes: one for the threads (root diameter), one for the shank (the unthreaded part at the base of the screw), and one for the head of the screw (for which you need a countersink).

If you wipe the screw with soap using a paper towel it will go in easier.

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  • You don't provide any reasoning for "never use battery powered drills." The tool industry has come a long way in powerful and long lasting batteries in the last few years. The convenience of not running an extension cord is well worth it. Drilling three pilot holes is completely unnecessary in most newbie homeowner applications. Maybe that's good advice if you're drilling in metal, but the softwood construction of the trellis OP mentions will only need one size of pilot. I think your answer has some merit, but you completely missed targeting OP's demographics for this question. – Doresoom Jul 22 '15 at 13:44

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