Drill Bit Sets for a Shop Truck: Which Index and Why

Tape this to the inside of the truck door. Every drill bit on a service truck goes in one of two piles: the index, which is the steel box with a slot for every size, and the sleeves, which are the tubes of 6, 12 or 24 bits in the sizes you burn through. The index is insurance. The sleeves are working stock. Most "which drill bit set" advice online argues about brands. This guide argues about piles, with our own numbers.

What is a drill index, and what do 13, 15, 21, 29 and 115 pieces mean?

A drill index is a drill bit set in a case with one labeled slot per size, usually a hinged steel box, so you can pull the size you need and see at a glance which slot is empty. The word comes from the index at the back of a book: the case points you to the size. People also say drill bit index, drill set, metal index, caddy or clip case. They all mean the same box of bits.

The piece count tells you the sizes inside, and the pattern is always the same:

Index	Pieces	Sizes	Step	Our set	Price	Status
Hex 7-piece	7	1/16 to 1/4 in.	By 32nds, 1/4 in. hex shank	045432 black oxide, 045532 ThunderBit	$30.34, $38.22	Active
13-piece	13	1/16 to 1/4 in.	By 64ths	Triumph 099501	$30.92	Ask us
15-piece	15	1/16 to 1/2 in.	By 32nds	Triumph 099502	$91.50	Ask us
21-piece	21	1/16 to 3/8 in.	By 64ths	Triumph 099503	$78.05	Ask us
26-piece letter	26	A (.234) to Z (.413)	Letter sizes	By the bit		Not stocked as a set
29-piece	29	1/16 to 1/2 in.	By 64ths	099505 steel index, 099504 clip caddy	$164.40, $169.55	Active
60-piece wire gauge	60	#60 (.040) to #1 (.228)	Number sizes	Triumph 099506	$135.43	Ask us
115-piece	115	All three systems	29 fractional + 60 wire + 26 letter	099832 black oxide, 090560 bright	$342.60 each	Active

Prices checked Nov 5, 2026. "Ask us" means Triumph lists it and we order it in; it is not on the shelf page.

The 29-piece is the drill index: every fractional size from 1/16 to 1/2 in. in 1/64 in. steps. The 115-piece adds the 60 wire-gauge (number) sizes and the 26 letter sizes, which exist to fill the gaps between fractions for tap drills and clearance holes. That is a toolroom index. It weighs 5-1/2 lb and has a 118° conventional point, not a split point. A truck does not need it, and the rest of this guide explains why with the only numbers that matter: which slots you will open.

The tap drills a truck reaches for, and which index holds them:

Thread	Tap drill	Decimal (in.)	In a 29-piece?	Single	Per bit
6-32	#36	0.1065	No, wire size	012636	$1.59
8-32	#29	0.1360	No, wire size	012629	$1.83
10-24	#25	0.1495	No, wire size	012625	$1.92
10-32	#21	0.1590	No, wire size	012621	$2.07
12-24	#16	0.1770	No, wire size	012616	$2.57
1/4-20	#7	0.2010	No, wire size	012607	$2.86
5/16-18	F	0.2570	No, letter size	Ask us
3/8-16	5/16	0.3125	Yes	012520	$4.96
1/2-13	27/64	0.4219	Yes	012527	$9.26

Is a 29-piece drill bit set worth it, or should you buy the sizes you use?

A 29-piece drill bit set is worth it as the backup, not as the supply, and our shelf prices show why. The 29 sizes in the 099505 ThunderBit+ set cost $164.40. The same 29 bits bought one each as singles come to $154.30. The steel box costs you ten dollars. So the set is not a discount on bits. It is a way to own one of each size without buying a sleeve of each, because our singles ship in sleeves of 6, 12, 24 or 36. One of every size at sleeve minimums is about $1,518 for 438 bits. Nobody needs that. The set is how you get one of each.

Here is the other half. We sold two complete drill bit sets on the web in the last twelve months. In the same twelve months we shipped 12,106 individual jobber and stubby bits to the trades, by the sleeve. Fifteen of the 29 slots in a fractional index sold fewer than six bits in a year. The trades do not drill 29 sizes. They drill about eight, and they drill three of them most of the day.

So the rule for a truck has two lines:

• One index. The 29-piece at $164.40, so a size you did not expect is in the truck and not at the supply house.

• Sleeves of the sizes you burn. A sleeve of twelve 1/4 in. ThunderBit+ bits (012516) is $38.88, which is $3.24 a bit. The same bit from the set works out to $5.67 a slot, and when it breaks the slot is empty until the next order.

Buy both on day one if the truck drills steel most days. Buy the sleeves first and the index the first time a job asks for a size you do not own if it drills steel once a week. Either way, the sizes that empty the slots go in sleeves, and the index stays full.

Which drill bit sizes does a service truck actually use?

Three sizes do most of the work. Across 12,106 jobber and stubby bits we sold in the twelve months to Nov 5, 2026, to electrical, HVAC, plumbing, fabrication and anchor-installing accounts and to web customers, 1/8 in. was 56% of the count, 3/16 in. was 12% and 1/4 in. was 10%. Add 5/16, 9/64, 7/32, 3/8 and 7/64 and eight fractional sizes are 92% of everything. Three wire sizes (#30, #7 and #20) show up next, and they are tap and rivet drills, not hole sizes you would pick from a chart.

Size	Share of bits we sold	What the trades drill with it	Sleeve (ThunderBit+)	Per bit	Sold in
1/8	56.3%	Pilots for self-drilling screws, #8 and #10 screws, pop rivets, a pilot before anything bigger	012508	$1.70	24
3/16	12.3%	1/4 in. concrete screw pilots, #12 and 1/4 sheet-metal screws, hanger pilots	012512	$2.24	24
1/4	9.6%	1/4-20 close clearance, strut and box holes, cable ties, small anchors	012516	$3.24	12
5/16	4.5%	1/4-20 free clearance, 3/8-16 tap drill, 5/16 hanger rod	012520	$4.96	12
9/64	3.4%	#10 screws into steel, the pilot under a 1/4 in. self-tapper	012509	$1.82	24
7/32	3.2%	#12 and 1/4 screws, 1/4-28 tap drill, 3/16 toggle pilots	012514	$2.72	24
3/8	2.1%	3/8 rod and bolts, box knockouts you enlarge with a step bit after	012524	$7.10	6
5/32	0.3%	#10 wood screws, 5/32 anchors, the size between the two you own	012510	$1.90	24
#30	2.5%	1/8 pop rivets (the rivet drill), #6 machine screws	012630	$1.83	24
#7	1.5%	1/4-20 tap drill	012607	$2.86	24
#20	1.5%	Rivet and hinge holes in sheet, #10 close fit	012620	$2.24	24

Shares are counts of bits, web orders plus account invoices, Nov 5, 2025 to Nov 5, 2026. One anchor-installing account buys 1/8 in. stubbies by the gross, which pushes the 1/8 share up; take the three-size rule as the finding, not the exact percentages. Prices checked Nov 5, 2026.

Notice what is not on the list. Nothing between 25/64 and 31/64. Nothing at 17/64 or 19/64. Those sizes are real, and the index has them for the day a bolt is a 1/64 bigger than you thought. That is the day the index earns its $164.40. Every other day, the sleeves do the drilling.

Every slot in a 29-piece index, with the share of our 12-month jobber and stubby sales it took and what one bit costs in each steel. The number in brackets is the sleeve it ships in. The part number is the steel's prefix plus the size in 64ths: 0125 for ThunderBit+, 0114 for black oxide HD, 0135 for cobalt, 0444 for the stubby.

Slot	Share of bits sold (%)	ThunderBit+ black and gold	Black oxide HD	Cobalt ThunderBit	Black oxide stubby
1/16	0.4	$1.45 (36)	$1.15 (36)	$2.64 (24)	$1.31 (36)
5/64	0.0	$1.45 (36)	$1.22 (36)	$2.67 (24)	$1.31 (36)
3/32	0.0	$1.59 (24)	$1.26 (36)	$2.83 (24)	$1.33 (36)
7/64	1.1	$1.59 (24)	$1.26 (36)	$2.91 (24)	$1.33 (36)
1/8	56.3	$1.70 (24)	$1.36 (36)	$3.40 (12)	$1.16 (36)
9/64	3.4	$1.82 (24)	$1.40 (36)	$3.69 (12)	$1.27 (36)
5/32	0.3	$1.90 (24)	$1.64 (24)	$3.88 (12)	$1.42 (36)
11/64	0.4	$1.96 (24)	$1.80 (24)	$4.17 (12)	$1.53 (24)
3/16	12.3	$2.24 (24)	$1.93 (24)	$4.78 (12)	$1.69 (24)
13/64	0.0	$2.56 (24)	$2.21 (24)	$6.41 (12)	$1.93 (24)
7/32	3.2	$2.72 (24)	$2.35 (24)	$6.69 (12)	$2.18 (24)
15/64	0.0	$2.97 (12)	$2.58 (24)	$6.69 (12)	$2.45 (24)
1/4	9.6	$3.24 (12)	$2.60 (24)	$7.80 (12)	$2.40 (24)
17/64	0.0	$3.88 (12)	$3.56 (12)	$8.66 (12)	$3.25 (12)
9/32	0.1	$4.54 (12)	$3.85 (12)	$9.21 (12)	$3.22 (12)
19/64	0.0	$4.88 (12)	$4.29 (12)	$10.87 (12)	$3.80 (12)
5/16	4.5	$4.96 (12)	$4.42 (12)	$11.46 (6)	$3.71 (12)
21/64	0.0	$5.54 (12)	$4.91 (12)	$12.25 (6)	$4.47 (12)
11/32	0.2	$6.37 (6)	$5.72 (12)	$14.49 (6)	$4.87 (12)
23/64	0.0	$6.94 (6)	$5.98 (6)	$16.16 (6)	$5.72 (12)
3/8	2.1	$7.10 (6)	$5.98 (6)	$17.28 (6)	$5.42 (12)
25/64	0.0	$8.10 (6)	$7.09 (6)	$17.82 (6)	$6.76 (6)
13/32	0.0	$8.38 (6)	$7.60 (6)	$20.06 (6)	$7.09 (6)
27/64	0.0	$9.26 (6)	$8.43 (6)	$20.32 (6)	$7.85 (6)
7/16	0.0	$9.82 (6)	$8.94 (6)	$21.46 (6)	$8.43 (6)
29/64	0.0	$11.53 (6)	$9.78 (6)	$25.89 (6)	$9.47 (6)
15/32	0.0	$11.53 (6)	$10.56 (6)	$25.36 (6)	$9.78 (6)
31/64	0.0	$12.14 (6)	$10.81 (6)	$25.89 (6)	$10.30 (6)
1/2	0.1	$12.14 (6)	$10.56 (6)	$27.07 (6)	$10.25 (6)

Prices per bit, checked Nov 5, 2026. A 0.0 share means fewer than six bits in a year.

Which drill bit set for an electrician's truck?

An electrician's truck carries three things: a hex-shank set on the impact driver, the 29-piece index in the truck, and sleeves of 1/8 and 3/16 in. Here is why it is three and not one.

The impact driver is the drill most electricians have in their hand, and a round-shank bit will not lock in it. The 045432 7-piece hex shank drill set is seven 135° split-point bits from 1/16 to 1/4 in. by 32nds on a 1/4 in. hex shank, made by Triumph in Chisholm, Minnesota, in a plastic case, for $30.34. The 045532 is the same seven sizes with the heavier ThunderBit core for $38.22. Either one covers pilots, device screws and box holes without a chuck change. Above 1/4 in. on the impact driver, ITM's titanium hex-shank jobbers run to 1/2 in.: 255HEX2064 is 5/16 in. at $8.41 and 255HEX2464 is 3/8 in. at $9.34.

The 29-piece 099505 stays in the truck for the strut, the enclosure and the odd clearance hole. Two sleeves ride beside it: 1/8 in. 012508 at $1.70 a bit and 3/16 in. 012512 at $2.24, both sold in 24. If the truck sets anchors in block, brick and the occasional tile, the BLU-SET5 five-piece carbide-tip set ($29.94, 1/8 to 3/8 in.) drills all of them with one bit in rotation only. If the truck taps panels, the HDT-SET8 drill-tap kit ($167.98, 6-32 to 1/2-13, 1/4 in. hex) drills, taps and chamfers in one pass, and it is the one set our web customers bought this year.

Which drill bit set for HVAC?

An HVAC truck drills sheet metal and duct all day, so the working stock is short bits in small sizes, not a big index. A stubby is half the length of a jobber and about six times stiffer, which is what you want in a cordless drill against 24-gauge duct. Our 135° black oxide stubbies are the cheapest bits we sell in the sizes the trade uses: 1/8 in. 044408 at $1.16 (sold in 36), 3/16 in. 044412 at $1.69 (sold in 24) and 1/4 in. 044416 at $2.40 (sold in 24). The length question, and when a jobber is better, is in the jobber vs stubby vs long drill bits guide.

Keep the 29-piece index for hangers, unistrut and the condenser pad, and keep cobalt in the truck by the size for stainless duct and fittings: 1/8 in. 013508 at $3.40, 3/16 in. 013512 at $4.78, 1/4 in. 013516 at $7.80, sold in 12. Anything bigger than 1/2 in. in sheet is a step drill, not a twist drill, and the step drill bit guide picks that one.

Which drill bit set for a plumber?

A plumber's twist-drill work lives between 3/16 and 1/2 in.: strut, hanger rod, clamps, brackets and the holes for 1/4-20 and 3/8-16 hardware. That is the upper half of a 29-piece index, and it is the one trade where the by-64ths steps get used, because rod and bolt clearance holes land on 17/64, 21/64 and 27/64. So the plumber's truck is the 29-piece 099505 plus sleeves of 1/4 in. 012516 ($3.24, sold in 12), 5/16 in. 012520 ($4.96, sold in 12) and 3/8 in. 012524 ($7.10, sold in 6).

Above 1/2 in. the twist drill changes shape. A reduced-shank Silver and Deming bit drills 9/16 to 1 in. from a 1/2 in. chuck, and the Silver and Deming guide sells those by the bit too. Holes through the floor above or down a chase are long bits, covered in the jobber vs stubby vs long guide linked above.

Black oxide, black and gold or cobalt: which steel for the index?

Black and gold high-speed steel with a 135° split point is the right steel for a truck index, because an index gets used on steel, aluminum, wood and plastic and started by hand. The 29-piece ThunderBit+ 099505 is that steel, with a 3-flat shank from 3/16 in. up so a keyless chuck cannot spin it. Black oxide 118° is cheaper and fine if the truck drills wood and mild steel only; the 29 black oxide HD jobber singles come to $135.24 one each, and we can order the plain black oxide 29-piece in. Bright finish is for aluminum and brass on a drill press.

Cobalt is never the right steel for a whole index. The 29 cobalt ThunderBit singles come to $342.81 one each, and stainless work uses two or three sizes, not 29. We stock no cobalt drill bit set for that reason. Buy the cobalt sizes you drill in stainless as sleeves and keep the HSS index for the rest. What each steel and coating actually buys you, with the hole counts, is in the cobalt vs titanium vs black oxide guide; this guide only decides what goes in the box.

What the big-box sets charge for the same 29 sizes (Nov 5, 2026, from the shopping results Google shows for these searches): DeWalt black and gold 29-piece $55 to $65, Milwaukee Red Helix titanium 29-piece $125, Milwaukee Red Helix cobalt 29-piece $150 to $165, Irwin M35 cobalt 29-piece $156. Our 099504 is listed at $189.60 at one industrial reseller; here it is $169.55. The difference between a $60 set and a $164 set is the steel and the point, and it shows up as how many holes a 1/8 in. bit drills before it is a 1/8 in. nail. We sell every size in the Triumph set as a single, which no big-box set offers.

How do you keep a drill index full?

A drill index stays full when every slot that empties twice becomes a sleeve. That is the whole system. The first time you break a 9/64, buy one from the sleeve of 24 and note it. The second time, the 9/64 goes on the sleeve list and never leaves the index empty again. On most trucks the sleeve list stops at five or six sizes, which is exactly what the sales table above says it should be.

Reordering a size is easier than it looks, because Triumph part numbers end in 64ths. The ThunderBit+ jobber is 0125 plus the size in 64ths: 012508 is 1/8 (8/64), 012512 is 3/16 (12/64), 012516 is 1/4 (16/64), 012524 is 3/8 (24/64) and 012532 is 1/2 (32/64). The same tail works on the black oxide HD jobber (0114), the stubby (0444) and the cobalt ThunderBit (0135). Wire sizes use the number itself: 012607 is a #7. Read the slot, write the number.

Small bits snap for five reasons, and none of them is the set. Pushing instead of letting the bit cut, tilting the drill as it breaks through, a flute packed with chips in a deep hole, a bit spinning in a keyless chuck, and a bit too long for the hole. The fixes are in order: ease up, keep square, peck every half inch, use the 3-flat shank sizes, and use a stubby for anything under 7/8 in. deep. The drill speed chart gives the starting speed for every size; a 1/8 in. bit in mild steel wants about 2,750 RPM and almost no pressure.

"Every drill index that comes back across my counter is missing the same three bits: the 1/8, the 3/16 and the 1/4. I have never had a customer call for a 29/64. Buy the index once, and buy those three by the sleeve."

David Castro, President, Eldorado Tools

Which drill bit set, by situation

Situation	Buy	Part number	Price
The one index for the truck	29-piece ThunderBit+ 3-flat, steel index, 1/16 to 1/2 in. by 64ths, 135° split point	099505	$164.40
Same bits in a clip caddy for a drawer or bag	29-piece ThunderBit+ caddy set	099504	$169.55
Impact driver on the belt	7-piece hex shank set, 1/16 to 1/4 in. by 32nds	045432 or 045532	$30.34 or $38.22
Hex shank above 1/4 in.	ITM titanium hex-shank jobber singles, 5/16 and 3/8 in.	255HEX2064, 255HEX2464	$8.41, $9.34
Sleeves of the sizes the truck burns	ThunderBit+ singles, 1/8, 3/16, 1/4, 5/16, 3/8 in.	012508, 012512, 012516, 012520, 012524	$1.70 to $7.10 a bit
Sheet metal and duct	135° black oxide stubby singles, 1/8, 3/16, 1/4 in.	044408, 044412, 044416	$1.16 to $2.40 a bit
Stainless, by the size	Cobalt ThunderBit singles, 1/8, 3/16, 1/4 in.	013508, 013512, 013516	$3.40 to $7.80 a bit
Tap drills the 29-piece lacks	Black and gold wire sizes #7 (1/4-20), #21 (10-32), #29 (8-32)	012607, 012621, 012629	$2.86, $2.07, $1.83
Drill, tap and chamfer in one pass	8-piece drill-tap kit, 6-32 to 1/2-13, 1/4 in. hex	HDT-SET8	$167.98
Anchors in block, tile and steel with one bit	5-piece multi-purpose carbide-tip set, 1/8 to 3/8 in.	BLU-SET5	$29.94
Broken bolts and hardened steel	5-piece carbide-tip hard steel set, right or left hand	RHB-SET5, LHB-SET5	$42.74, $51.69
The toolroom, not the truck	115-piece index, fractional + wire + letter, 118°	099832 black oxide, 090560 bright	$342.60

Prices checked Nov 5, 2026. Singles are priced per bit and sold in sleeves; the sleeve size is on each product page. All of them live in High-Speed Drill Bits: Sets, Sets & Kits and Jobber Length.

FAQ

Why are drill bit sets 29 pieces?

Because 1/16 to 1/2 in. in 1/64 in. steps is 29 sizes. That range covers every fastener clearance and tap drill a fractional shop needs below 1/2 in., and 1/2 in. is where a standard drill chuck stops.

Which tap drill sizes are missing from a 29-piece drill bit set?

The wire and letter ones: #36 for 6-32, #29 for 8-32, #25 for 10-24, #21 for 10-32, #16 for 12-24, #7 for 1/4-20 and F for 5/16-18. A 29-piece does hold 5/16 for 3/8-16 and 27/64 for 1/2-13. Buy the wire sizes as singles (012636, 012629, 012625, 012621, 012616, 012607) and use the tap drill size chart for the rest.

Can I buy a drill index empty?

Yes. Tru-Cut makes empty steel indexes in 13, 15, 21, 29, 60 and 115 slots, and an empty 29-slot index is the right way to build a truck set from sleeves. Ask us for the 29-slot box; it is not on the shelf page yet.

Do you sell a metric drill bit set?

We can order the 25-piece 1 to 13 mm set from Titan or the 26-piece metric ThunderBit+ set from Triumph. Ask us. Most trucks need two or three metric sizes, which we sell as singles.

How do your sets compare with a Milwaukee or DeWalt drill bit set?

Same 29 sizes. A DeWalt black and gold 29-piece sells for about $55 to $65 and a Milwaukee Red Helix cobalt 29-piece for $150 to $165 at retail. Ours is $164.40 for heavy-duty black and gold high-speed steel with a 135° split point and 3-flat shanks, made by Triumph in Minnesota, and every size in it is sold as a single so you never buy the set twice.

What is the 3-flat shank for?

Three flats ground on the shank give a keyless chuck something to grip, so the bit cannot spin in the jaws under load. The ThunderBit+ sets have them from 3/16 in. up.

Can I run the bits from a 29-piece set in an impact driver?

Not without a chuck adapter, and not well. The round and 3-flat shanks do not lock in a 1/4 in. hex collet, and the hammering chips the corners of a split point. Use the 7-piece hex shank set on the impact driver and the index in a drill.

What are the plastic gauge cards in a drill bit set?

Size gauges. Hold a worn bit in the hole that fits and read the size off the card, then reorder that number. The 64ths part number trick above does the same thing with a tape measure.

Is a 115-piece drill bit set worth it for a service truck?

No. A 115-piece index is a toolroom tool: 60 wire sizes and 26 letter sizes exist for tap drills and precise clearance holes at a drill press. A truck uses eight fractional sizes and three wire sizes, so buy the 29-piece and the three wire singles and keep the $178 difference.

Not sure which index to put on the truck? Call our team at (833) 4-ETOOLS or email sales@eldoradotools.com with the trade and the three sizes you break most, and we will build the sleeve list.

Sources: Triumph Twist Drill and ITM product specifications; our web and account order records, Nov 5, 2025 to Nov 5, 2026; retail set prices as shown in Google Shopping results on Nov 5, 2026.

First published [date], with prices checked in our catalog on Nov 5, 2026.