How to Use a Drill and Tap Chart

When it comes to machining, the key to a finely machined piece is all in the tap. To properly tap a hole, you’ll need to drill it out and use the corresponding tap according to a drill and tap chart.

But, it’s not quite as simple as it seems. Today, we’re going to cover how to use a drill and tap chart and take a look at some of the best drill and tap sets that are on the market today.

What is a Tap?

A tap is a tool that features a threaded midsection, just like a screw or bolt would. A tap takes a hole in the material and adds threads to it, so it’s able to mate with the appropriate fastener. Before using a tap, you need to drill a hole in the material. The size of that hole corresponds with a tap, and once you create the hole, you use a tap to add threads to the piece of metal you’re working with.

Why Tap Holes?

With machined parts, it’s often necessary to add female threads to a piece of metal so that they can mate with a screw to provide a solid assembly. In some cases, you could avoid tapping in favor of using a nut on the opposite side of the fastener. But, in most cases, tapping the hole and attaching the hardware directly to the metal you’re working on is your best bet.

What is a Drill and Tap Chart?

A drill and tap chart is a large chart that provides all the information you need to properly tap holes.

All charts include values for screw size, major and minor diameter. From there, they tell you the proper size drill bit to use to make the hole for the tap. The chart will also let you know the correct size bit to use if you plan on tapping the hole, and the correct size bit to use if you’re just drilling out a hole to attach a fastener with a nut.

This comprehensive drill and tap chart includes everything you’ll need to know. Bookmark this reference so you can recall it whenever you need to.

Drill and Tap Conversion Chart

Fraction (in)	Decimal (in)	Wire (#)	Metric (mm)	Fraction (in)	Decimal (in)	Wire (#) Letter (A-Z)	Metric (mm)	Fraction (in)	Decimal (in)	Wire (#)	Metric (mm)
	0.0098		0.25		0.1065	36			0.3480	S
	0.0118		0.30	7.64	0.1094				0.3543		9.00
	0.0135	80			0.1100	35			0.3580	T
	0.0138		0.35		0.1102		2.80	23/64	0.3594
	0.0145	79			0.1110	34			0.3680	U
1/64	0.0156				0.1130	33			0.3740		9.50
	0.0157		0.40		0.1142		2.90	3/8	0.3750
	0.0160	78			0.1160	32			0.3770	V
	0.0177		0.45		0.1181		3.00		0.3860	W
	0.0180	77			0.1200	31		25/64	0.3906
	0.0197		0.50	1/8	0.1250				0.3937		10.00
	0.0200	76			0.1285	30			0.3970	X
	0.0210	75			0.1360	29			0.4040	Y
	0.0217		0.55		0.1378		3.50	13/32	0.4063
	0.0225	74			0.1405	28			0.4130	Z
	0.0236		0.60	9/64	0.1406				0.4134		10.50
	0.0240	73			0.1440	27		27/64	0.4219
	0.0250	72			0.1470	26			0.4331		11.00
	0.0256		0.65		0.1495	25		7/16	0.4375
	0.0260	71			0.1520	24			0.4528		11.50
	0.0276		0.70		0.1540	23		29/64	0.4531
	0.0280	70		5/32	0.1563			15/32	0.4688
	0.0292	69			0.1570	22			0.4724		12.00
	0.0295		0.75		0.1575		4.00	31/64	0.4844
	0.0310	68			0.1590	21			0.4921		12.50
1/32	0.0313				0.1610	20		1/2	0.5000
	0.0315		0.80		0.1660	19			0.5118		13.00
	0.0320	67			0.1695	18		33/64	0.5156
	0.0330	66		11/64	0.1719			17/32	0.5313
	0.0335		0.85		0.1730	17			0.5315		13.50
	0.0350	65			0.1770	16		35/64	0.5469
	0.0354		0.90		0.1772		4.50		0.5512		14.00
	0.0360	64			0.1800	15		9/16	0.5625
	0.0370	63			0.1820	14			0.5709		14.50
	0.0374		0.95		0.1850	13		37/64	0.5781
	0.0380	62		3/16	0.1875				0.5905		15.00
	0.0390	61			0.1890	12		19/32	0.5938
	0.0394		1.00		0.1910	11		39/64	0.6094
	0.0400	60			0.1935	10			0.6102		15.50
	0.0410	59			0.1960	9		5/8	0.6250
	0.0420	58			0.1968		5.00		0.6299		16.00
	0.0430	57			0.1990	8		41/64	0.6406
	0.0433		1.10		0.2010	7			0.6496		16.50
	0.0465	56		13/64	0.2031			21/32	0.6563
3/64	0.0469				0.2040	6			0.6693		17.00
	0.0472		1.20		0.2055	5		43/64	0.6719
	0.0512		1.30		0.2090	4		11/16	0.6875
	0.0520	55			0.2130	3			0.6890		17.50
	0.0550	54			0.2165		5.50	45/64	0.7031
	0.0551		1.40	7/32	0.2188				0.7087		18.00
	0.0591		1.50		0.2210	2		23/32	0.7188
	0.0595	53			0.2280	1			0.7283		18.50
1/16	0.0625				0.2340	A		47/64	0.7344
	0.0630		1.60	15/64	0.2344				0.7480		19.00
	0.0635	52			0.2362		6.00	3/4	0.7500
	0.0669		1.70		0.2380	B		49/64	0.7656
	0.0670	51			0.2420	C			0.7677		19.50
	0.0700	50			0.2460	D		25/32	0.7813
	0.0709		1.80	1/4	0.2500	E			0.7874		20.00
	0.0730	49			0.2559		6.50	51/64	0.7969
	0.0748		1.90		0.2570	F			0.8071		20.50
	0.0760	48			0.2610	G		13/16	0.8125
5/64	0.0781			17/64	0.2656				0.8268		21.00
	0.0785	47			0.2660	H		53/64	0.8281
	0.0787		2.00		0.2720	I		27/32	0.8438
	0.0810	46			0.2756		7.00		0.8465		21.50
	0.0820	45			0.2770	J		55/64	0.8594
	0.0827		2.10		0.2810	K			0.8661		22.00
	0.0860	44		9/32	0.2813			7/8	0.8750
	0.0866		2.20		0.2900	L			0.8858		22.50
	0.0890	43			0.2950	M		57/64	0.8906
	0.0906		2.30		0.2953		7.50		0.9055		23.00
	0.0935	42		19/64	0.2969			29/32	0.9063
3/32	0.0938				0.3020	N		59/64	0.9219
	0.0945		2.40	5/16	0.3125				0.9252		23.50
	0.0960	41			0.3150		8.00	15/16	0.9375
	0.0980	40			0.3160	O			0.9449		24.00
	0.0984		2.50		0.3230	P		61/64	0.9531
	0.0995	39		21/64	0.3281				0.9646		24.50
	0.1015	38			0.3320	Q		31/32	0.9688
	0.1024		2.60		0.3346		8.50		0.9842		25.00
	0.1040	37			0.3390	R		63/64	0.9844
	0.1063		2.70	11/32	0.3438			1	1.0000
Fraction (in)	Decimal (in)	Wire (#)	Metric (mm)	Fraction (in)	Decimal (in)	Wire (#)	Metric (mm)	Fraction (in)	Decimal (in)	Wire (#)	Metric (mm)

How to Use a Drill and Tap Set

Using a drill and tap set is quite easy. The key to producing properly tapped pieces is to make sure everything you do follows the drill and tap chart.

First, identify the fastener size you’ll be using on the tap chart. From there you’ll be able to find the proper bit to use to create the hole.

Next, put the corresponding bit into your drill. A drill press is optimal for tapping holes, but if you don’t have one in your shop, a corded or cordless drill will do the trick just fine. Put on safety glasses to protect yourself from any flying debris, and drill out your hole.

Once you have your hole, you can tap the hole to add the threads.

First, secure the piece you’re working with. A bench vise is the best way to secure the part, but you can clamp it to your workbench if it’s too large for a vise. Grab the corresponding tap from your tap kit, and attach it to the tap wrench. If you don’t have enough clearance to use a tap wrench, you can use a shorter t-handle wrench.

Stand directly over your workpiece, and place the tap into the hole, ensuring that it’s perfectly straight. Now, apply gentle pressure and begin to screw the tap into the piece. Within a turn or two, you should feel the cutting threads as they bite into your workpiece.

Continue to apply gentle pressure and turn the tap. For each clockwise rotation, you make, rotate the tap back out a half turn counterclockwise. This will break off any loose metal that’s left over as the tap enters the metal, and ensure a correctly tapped hole.

Repeat this process until the tap has passed through the entirety of the workpiece, and then remove the tap. At this point, you should have a correctly tapped hole that’s ready to add a fastener to.

Best Drill and Tap Sets

Now that you’re armed with the knowledge you need to properly tap a hole let’s take a look at a few of the best drill and tap sets that are on the market.

Irwin 117-Piece Deluxe Drill and Tap Set

For the machinist that needs a comprehensive selection of taps, this kit is exactly what you’ll need.

Included in this set are 117 of the most common plug tap, and hex die sizes, screw extractors, drill bits, wrench handles, and pitch gauges. Everything is neatly packaged in a fitted plastic case.

What We Like

• Includes a comprehensive selection of taps
• Multiple tap handles have you covered for every application

What Could Be Better

• Expensive

Bosch BDT11S 11-Piece Drill and Tap Set

If you just need the basics for occasional use, you can’t go wrong with this set from Bosch.

This kit includes #7, 21, 25, 29, and 36 bits, and their corresponding taps. The sizes for each bit and tap is laser etched into the bit itself for easy referencing. The sizes are also printed on the inside of the case, so you’ll be able to put each bit back in its proper place when you’re done. Also included is a deluxe tap wrench. Everything in this set comes in a quality case.

While it doesn’t include a broad range of different sizes, this kit represents the most popular fastener sizes, making it perfect for basic jobs.

What We Like

• Includes the most popular tap sizes
• Included tap wrench is perfect for use in low-clearance situations

What Could Be Better

• Only includes five different taps

AccusizeTools 18-Piece Drill and Tap Set

This set from AccusizeTools is incredibly well made and includes a few extra taps you won’t find in the Bosch kit we covered above.

This kit includes nine popular bits and taps, all enclosed in a steel case that’s built to last. Each bit contains HSS fully ground steel, so it should stand up to anything you can throw at it for many years to come.

Since this kit is a bit more comprehensive than some smaller kits, it’s perfect for the machinist who needs a multitude of different popular taps but isn’t looking to invest hundreds of dollars into a larger package.

What We Like

• Includes a broader range of tap sizes
• Steel case with easy to read bit markings

What Could Be Better

• Doesn’t include a tap wrench

Final Word

Drill and tap charts and sets are among the most mysterious tools you’ll need to have. But, once you have the knowledge on how to read the chart and use the taps, you’re well on your way to producing beautifully machined pieces in your shop.