What Size Hole To Drill For 1/4 Npt Tap

As an Amazon Associate we earn from qualifying purchases.

Information technology doesn't happen often around the house, only sometimes you lot demand to tap new threads into metal. When drilling the initial pigsty before borer, it needs to exist smaller than the tap just big plenty that the tap will cut the edges. One of the most common sizes is a quarter-inch with 20 threads per inch, so you will desire to know what size drill bit for 1/iv″ 20 tap.

Contents

What Size Drill Fleck for 1/4″ xx Tap?
Other Considerations for Drilling 1/4″ 20 Tap
- How to Drill for Tapping
- How to Use a 1/4″ 20 Tap
- Pecking
Conclusion

What Size Drill Chip for 1/4″ 20 Tap?

The best overall size drill bit for 1/4″ 20 UNC tap thread is a #7 drill bit, the measurement being 13/64" (0.203″diameter).

Screw Size	Drill Bit	Drill Bit Size
1/4″ 20 Tap	#7	13/64″
1/4″ 28 Tap	#three	7/32″

The concept of borer threads is relatively simple, but in practice, it can get complicated.

If the hole is besides modest, the tapping volition extend too far into the center making information technology hard to spiral the bolt into the pigsty.
If the drilled hole is too large, the bolt will not mate well enough with the threads.

There can be exceptions to this dominion when information technology comes to the hardness of the material being drilled, which may brand a departure with the tap drill size y'all will be using.

The standard tap drill is 75% for boilerplate or softer materials, but you would may 50% for harder materials that need a tighter connection with the screw or bolt.

Harder materials may include steel, stainless steel, and fe. For softer materials you are looking at aluminum, plastic, brass, and more. If yous are not certain, be sure to check the manufacturer's instructions for the right size tap drill to apply in your detail use example.

When tapping harder materials, you may want to use the finer threading of 50%. This tin can alter your drill bit size – the recommended size drill bit for 1/4″ 20 tap when using a 50% tap drill is vii/32".

Here are different drill sizes when yous accept different threads per inch for i/4″ screws:

Spiral Size	Threads Per Inch	Drill Bit Size 75% Thread	Drill Chip Size 50% Thread
ane/iv"	20	#7	7/32
1/4"	28	#3	#1
one/4"	32	7/32	#1

Every bit you can meet, there are some commonalities, but likewise some differences in what size drill flake to use when taking threads per inch into business relationship. In general, the higher threads per inch, and the more than fine the threads are, the larger (slightly) your drilled hole that you will be borer should be.

Selecting what size drill bit for 1/4 20 tap

Other Considerations for Drilling 1/4″ 20 Tap

When you drill any type of material for borer, be sure to decide beforehand whether you will be tapping with 50% or 75%. This may change depending on the hardness of the material, then if yous are able to drill through a scrap piece first, that may give y'all a amend idea of how you should tap.

How to Drill for Tapping

When you have decided on which size drill bit to use, yous will and so need to move on to the drilling process. When drilling into metal you will want to mount that cloth with at least two clamps to reduce the take a chance of the metallic spinning and possibly injuring yous. Wear safe goggles and consider thick gloves also.

You volition first need to mark the area to be drilled. Apply masking or painters tape not only to leave a nice surface area to mark, but likewise to help keep the step drill fleck in one place. Using a center punch with a hammer will help too by leaving a divot for the bit to residuum in. If drilling into a thin or flexible cloth, be sure it has solid bankroll so y'all do not deform information technology.

Make sure your drill is completely perpendicular at 90 degrees to the textile you are drilling. Any angle created may create problems with both tapping and screwing in bolts. If possible, utilize a drill printing or a guide for your handheld drill. Use cutting fluid and regularly sharpen your drill bits, make certain to practise your all-time to keep the drill chip from getting also hot.

How to Use a 1/4″ 20 Tap

The purpose of tapping is to create a threaded hole for a screw or commodities to enter, so e'er have the bolt ready for a visual comparison that y'all are headed in the right management.

After the initial hole is drilled, you will kickoff want to de-burr the border of the hole and remove any precipitous edges. Additionally, calculation a chamfer at this point will brand the tapping become easier. Information technology is easy to chamfer with specialized drill bits, but you tin use normal drill bits every bit well.

Be sure to clean out the fries, dust, and other droppings that may accept accumulated in the hole or around information technology.

When setting upwardly the tap, it helps to utilize a 90° tap guide. When we add and so much downward pressure to the pigsty and tool that nosotros are working on, information technology is like shooting fish in a barrel to lean to the side, catastrophe up with a crooked tap. Use the guide and take your fourth dimension.

Pecking

I way of tapping threads into a pigsty is chosen "pecking." This procedure involves going forward a brusk distance, and so backing off. Information technology helps keep your tap or drill scrap from overheating or fifty-fifty breaking under the farthermost torque used to get through metal.

The most common class of pecking involves turning a full plough of the tap in, and then a half turn out. To be even more careful, yous could become a full turn, remove the tap completely, clean out the pigsty, go in two turns, and repeat until the hole is fully tapped. This takes quite a long time but will create the most even thread tapping.

Run into our article on the right size bit for a x-24 bit.

Conclusion

Selecting the correct size drill bit for a ane/4″ xx tap depends on the coarseness of the threads you will be borer, which is in turn based on the hardness of the cloth you will exist drilling through. Brand a decision beforehand and exam with bit material if available and so yous are able to take the right tools on paw.