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Silver and Deming Drill Bits: Big Holes From a 1/2 in. Chuck
Which Silver and Deming bit drills the hole for your bolt or tap, HSS or cobalt, how fast to run it, and every size we stock with prices.
Quick answer: Silver and Deming drill bits are twist drills from 33/64 to 1-1/2 in. with the shank turned down to 1/2 in., so a big hole fits a standard 1/2 in. chuck. Every one is 6 in. long with a 3 in. flute. Pick the size from the bolt or tap you are using, pick HSS for mild steel or M42 cobalt for stainless, and run it slow: about 450 RPM for a 3/4 in. bit in mild steel. We stock 184 bits in 44 sizes, from $18.59 each.
What is a Silver and Deming drill bit?
A Silver and Deming drill bit is a large twist drill with a 1/2 in. shank, so you can drill holes from 33/64 in. up to 1-1/2 in. without a bigger chuck or a taper-shank drill press. Machinists call it an S&D bit or a reduced-shank drill. The cutting end is full size. Only the part the chuck grips is smaller.
Three things are the same on every bit we sell, whatever the size:
Shank: 1/2 in., either round or with three flats ground in.
Overall length: 6 in.
Flute length: 3 in. That is the working depth, so these are plate-and-flange bits, not deep-hole bits.
Sizes run in 1/64 in. steps up to 1 in. and in 1/32 in. steps from 1 to 1-1/4 in., then 1/16 in. steps to 1-1/2 in. That fine spacing is the point. It means there is an S&D bit for every common bolt clearance hole and every big tap drill.
What size Silver and Deming bit do I need for my bolt?
Start from the bolt, not the bit. A clearance hole for a structural bolt is 1/16 in. over the bolt (a 3/4 in. bolt takes a 13/16 in. hole), and an oversized hole is 3/16 in. over up to 7/8 in. bolts. A tapped hole takes the tap drill size, which is smaller than the bolt. The table gives all of them for 1/2 to 1 in. bolts, with the bit we stock for each.
Bolt or rod |
Standard hole |
Oversized hole |
Tap drill, coarse |
Tap drill, fine |
Base-plate hole |
|---|---|---|---|---|---|
1/2 in. |
9/16 in. SD91436 |
5/8 in. SD91440 |
1/2-13: 27/64 in. (outside S&D range) |
1/2-20: 29/64 in. (outside S&D range) |
— |
5/8 in. |
11/16 in. SD91444 |
13/16 in. SD91452 |
5/8-11: 17/32 in. SD91434 |
5/8-18: 37/64 in. SD91437 |
— |
3/4 in. |
13/16 in. SD91452 |
15/16 in. SD91460 |
3/4-10: 21/32 in. SD91442 |
3/4-16: 11/16 in. SD91444 |
1-5/16 in. SD91484 |
7/8 in. |
15/16 in. SD91460 |
1-1/16 in. SD91468 |
7/8-9: 49/64 in. SD91449 |
7/8-14: 13/16 in. SD91452 |
1-9/16 in. (outside S&D range) |
1 in. |
1-1/16 in. SD91468 |
1-1/4 in. SD91480 |
1-8: 7/8 in. SD91456 |
1-12: 59/64 in. SD91459 |
1-13/16 in. (outside S&D range) |
Standard and oversized holes from ANSI/AISC 360-22, Table J3.3. Base-plate holes are the maximum anchor-rod hole sizes in AISC Design Guide 1. Tap drills cut about 75% of a full thread, matching our tap drill size chart. Links go to the Titan HSS round-shank bit; every series is in the size table below.
Pipe taps need bigger drills than their names suggest, because NPT sizes name the pipe bore. From 3/8 NPT up, every pipe-tap drill is an S&D size:
Pipe thread |
Tap drill |
Our pipe tap |
|---|---|---|
3/8-18 NPT |
37/64 in. SD91437 |
071252 $43.38 |
1/2-14 NPT |
23/32 in. SD91446 |
071253 $70.83 |
3/4-14 NPT |
59/64 in. SD91459 |
071254 $96.82 |
1-11-1/2 NPT |
1-5/32 in. SD91474 |
071255 $147.57 |
1-1/4-11-1/2 NPT |
1-1/2 in. SD91496 |
071256 $209.55 |
Which Silver and Deming bit should I buy?
Buy Titan HSS round-shank bits for mild steel in a drill press, 3-flat bits when you drill by hand, and M42 cobalt only for stainless or hard alloys. We carry five series. They differ in shank, point, steel and minimum order, not in size coverage below 1 in.
If you are… |
Buy |
Example |
Price |
|---|---|---|---|
Drilling mild steel in a drill press or mag drill, one size at a time |
Titan HSS, round shank |
3/4 in. SD91448 |
$27.09 each |
Drilling by hand, where a round shank spins in the chuck |
Titan HSS, 3-flat shank |
3/4 in. SD92548 |
$29.65 each |
Restocking a crew, two of each size |
Triumph black oxide |
3/4 in. 092848 |
$27.58 each (min. 2) |
Starting on curved or angled steel without a center punch |
Triumph ThunderBit (split point) |
3/4 in. 094148 |
$33.60 each (min. 2) |
Stainless steel, tool steel or hard alloys |
Titan M42 cobalt, 135° split point |
3/4 in. SD93648 |
$55.58 each |
Holes over 1 in., up to 1-1/2 in. |
Titan HSS round or Triumph black oxide |
1-1/4 in. SD91480 |
$80.36 each |
Prices from our catalog on Oct 26, 2026.
Series |
Shank |
Point |
Steel |
Finish |
Sizes |
3/4 in. price |
Minimum |
|---|---|---|---|---|---|---|---|
Titan HSS, round shank |
1/2 in. round |
118° split |
HSS |
Bright |
33/64–1-1/2 in. |
$27.09 · SD91448 |
None |
Titan HSS, 3-flat shank |
1/2 in. with 3 flats |
118° split |
HSS |
Bright |
33/64–1 in. |
$29.65 · SD92548 |
None |
Titan M42 cobalt |
1/2 in. round |
135° split |
M42 cobalt |
Bright |
33/64–1 in. |
$55.58 · SD93648 |
None |
Triumph black oxide |
1/2 in. with 3 flats |
118° |
HSS |
Black oxide |
33/64–1-1/2 in. |
$27.58 · 092848 |
2 through 7/8 in. |
Triumph ThunderBit |
1/2 in. with 3 flats |
118° split |
HSS |
Black and gold |
33/64–1 in. |
$33.60 · 094148 |
2 on most sizes through 3/4 in. |
Two things stand out on price. M42 cobalt costs about twice as much as plain HSS at every size, so it only pays where HSS fails, mainly stainless. And every series jumps at 1 in.: the Titan round bit goes from $42.91 at 1 in. to $57.58 at 1-1/32 in., a 34% step for 1/32 in. of diameter. If 1 in. clears your bolt, stop there.
Round shank or three flats?
Choose three flats for a hand drill and round for a drill press. A 1 in. bit in steel puts a lot of torque through a 1/2 in. shank, and a three-jaw chuck can slip on a round shank, which scores it and stalls the cut. Flats give the jaws something to bite. Titan sells the same HSS bit both ways; the 3-flat version costs about 12% more. Both Triumph series come with flats only.
HSS or cobalt for stainless steel?
Use M42 cobalt for stainless. Plain HSS softens at the heat stainless makes, and once the edge rubs, the stainless work-hardens and stops cutting. Our Titan M42 bits also have a 135° split point, which starts without walking and needs less push. For mild steel, aluminum and brass, HSS cuts just as well for half the price. For hardened steel or cast iron, see drill bits for hardened steel.
How fast should a Silver and Deming bit turn?
Slower than you think: about 450 RPM for a 3/4 in. bit in mild steel, 350 RPM for 1 in. and 150 RPM for 1 in. in stainless. RPM = 3.82 × cutting speed ÷ bit diameter, using the same cutting speeds as our drill speed chart.
Bit size |
Aluminum |
Brass |
Mild steel |
Cast iron |
Stainless steel |
|---|---|---|---|---|---|
9/16 in. |
1,700 |
1,000 |
600 |
500 |
270 |
5/8 in. |
1,550 |
900 |
550 |
450 |
240 |
11/16 in. |
1,400 |
850 |
500 |
400 |
220 |
3/4 in. |
1,250 |
750 |
450 |
350 |
200 |
13/16 in. |
1,200 |
700 |
400 |
350 |
190 |
7/8 in. |
1,100 |
650 |
400 |
300 |
170 |
15/16 in. |
1,000 |
600 |
350 |
290 |
160 |
1 in. |
950 |
550 |
350 |
270 |
150 |
1-1/8 in. |
850 |
500 |
300 |
240 |
140 |
1-1/4 in. |
750 |
450 |
280 |
210 |
120 |
1-3/8 in. |
700 |
400 |
250 |
190 |
110 |
1-1/2 in. |
650 |
400 |
230 |
180 |
100 |
Starting RPM for HSS and cobalt bits at 250, 150, 90, 70 and 40 surface feet per minute. Rounded to the nearest 50 RPM, or 10 below 300.
Can I drill a 1 in. hole with a hand drill?
Yes, with a 1/2 in. drill in low gear, a 3-flat bit, a side handle and the work clamped. Most two-speed cordless drills top out around 450 to 600 RPM in low gear, which covers every S&D size in steel. Work in this order:
Clamp the work. A big bit that catches will spin loose stock or your wrist.
Center punch, then pilot. A 1/8 or 3/16 in. pilot takes load off the bit's center. A bigger pilot can make the bit grab.
Low gear, side handle on. Brace the handle against the direction the drill wants to twist.
Oil and steady push. Sulfur cutting oil on steel and stainless. You want curls, not dust.
Ease off at breakthrough. The bit grabs as it exits. Lighten up when the point comes through.
When is a Silver and Deming bit the wrong tool?
An S&D bit is the wrong tool for thin sheet, for holes over 1-1/2 in., and for plate thicker than its 3 in. flute can clear. In strut and panels it grabs and leaves a triangle instead of a hole; a step drill is cleaner there.
Tool |
Best for |
Limit |
Ours |
|---|---|---|---|
Silver and Deming bit |
Bolt and tap holes 33/64 to 1-1/2 in. in plate, flange, angle and bar |
Flute is 3 in. long; slow and thirsty past 1 in. |
|
Step drill |
Strut, panels, boxes and sheet up to about 1/8 in. |
Each step is only as deep as its height |
274MC0005, 7/16–1-1/8 in., $75.06 |
Bi-metal hole saw |
Holes over 1-1/2 in. in sheet and thin plate |
Slow in plate over 1/4 in.; needs an arbor |
|
Carbide-tipped drill |
Hardened steel, cast iron, broken bolts |
Brittle; drill press only |
See our hardened-steel guide |
Annular cutter on a mag drill |
Production holes in plate over 1 in. thick |
Needs a magnetic drill |
We do not stock these |
For strut, rod and conduit work, see our guide to drill bits for metal for the jobber sizes under 1/2 in. that do the rest of the drilling.
Every Silver and Deming size we stock
We stock 184 Silver and Deming bits in 44 sizes. Every price is for one bit. Triumph sizes marked "min. 2" ship two at a time.
Size |
Decimal |
Titan HSS, round shank |
Titan HSS, 3-flat shank |
Titan M42 cobalt |
Triumph black oxide |
Triumph ThunderBit |
|---|---|---|---|---|---|---|
33/64 in. |
0.5156 |
$18.59 · SD91433 |
$20.26 · SD92533 |
$36.97 · SD93633 |
$19.70 · 092833 (min. 2) |
$25.28 · 094133 (min. 2) |
17/32 in. |
0.5312 |
$18.59 · SD91434 |
$20.26 · SD92534 |
$36.97 · SD93634 |
$19.62 · 092834 (min. 2) |
$24.50 · 094134 (min. 2) |
35/64 in. |
0.5469 |
$19.62 · SD91435 |
$21.55 · SD92535 |
$44.48 · SD93635 |
$21.10 · 092835 (min. 2) |
$26.88 · 094135 (min. 2) |
9/16 in. |
0.5625 |
$19.62 · SD91436 |
$21.55 · SD92536 |
$44.48 · SD93636 |
$20.85 · 092836 (min. 2) |
$25.28 · 094136 (min. 2) |
37/64 in. |
0.5781 |
$21.06 · SD91437 |
$23.15 · SD92537 |
$46.00 · SD93637 |
$22.62 · 092837 (min. 2) |
$28.53 · 094137 (min. 2) |
19/32 in. |
0.5938 |
$21.06 · SD91438 |
$23.15 · SD92538 |
$46.00 · SD93638 |
$22.62 · 092838 (min. 2) |
$27.70 · 094138 (min. 2) |
39/64 in. |
0.6094 |
$22.14 · SD91439 |
$24.23 · SD92539 |
$47.17 · SD93639 |
$23.33 · 092839 (min. 2) |
$29.57 · 094139 (min. 2) |
5/8 in. |
0.6250 |
$22.14 · SD91440 |
$24.23 · SD92540 |
$47.17 · SD93640 |
$23.10 · 092840 (min. 2) |
$28.02 · 094140 (min. 2) |
41/64 in. |
0.6406 |
$23.20 · SD91441 |
$25.83 · SD92541 |
$49.48 · SD93641 |
$24.82 · 092841 (min. 2) |
$31.43 · 094141 (min. 2) |
21/32 in. |
0.6562 |
$23.20 · SD91442 |
$25.83 · SD92542 |
$49.48 · SD93642 |
$24.33 · 092842 (min. 2) |
$30.40 · 094142 (min. 2) |
43/64 in. |
0.6719 |
$24.67 · SD91443 |
$26.86 · SD92543 |
$50.50 · SD93643 |
$25.82 · 092843 (min. 2) |
$32.88 · 094143 (min. 2) |
11/16 in. |
0.6875 |
$24.67 · SD91444 |
$26.86 · SD92544 |
$50.50 · SD93644 |
$25.43 · 092844 (min. 2) |
$30.92 · 094144 (min. 2) |
45/64 in. |
0.7031 |
$24.76 · SD91445 |
$27.23 · SD92545 |
$53.26 · SD93645 |
$27.05 · 092845 (min. 2) |
$34.17 · 094145 (min. 2) |
23/32 in. |
0.7188 |
$24.76 · SD91446 |
$27.23 · SD92546 |
$53.26 · SD93646 |
$26.58 · 092846 (min. 2) |
$33.08 · 094146 (min. 2) |
47/64 in. |
0.7344 |
$27.02 · SD91447 |
$29.65 · SD92547 |
$55.58 · SD93647 |
$28.30 · 092847 (min. 2) |
$35.77 · 094147 |
3/4 in. |
0.7500 |
$27.09 · SD91448 |
$29.65 · SD92548 |
$55.58 · SD93648 |
$27.58 · 092848 (min. 2) |
$33.60 · 094148 (min. 2) |
49/64 in. |
0.7656 |
$28.73 · SD91449 |
$31.64 · SD92549 |
$58.12 · SD93649 |
$29.78 · 092849 (min. 2) |
$37.73 · 094149 |
25/32 in. |
0.7812 |
$28.73 · SD91450 |
$31.64 · SD92550 |
$58.12 · SD93650 |
$29.78 · 092850 (min. 2) |
$36.60 · 094150 |
51/64 in. |
0.7969 |
$30.20 · SD91451 |
$34.68 · SD92551 |
$59.67 · SD93651 |
$31.78 · 092851 (min. 2) |
$40.07 · 094151 |
13/16 in. |
0.8125 |
$30.20 · SD91452 |
$34.68 · SD92552 |
$59.67 · SD93652 |
$31.63 · 092852 (min. 2) |
$37.95 · 094152 |
53/64 in. |
0.8281 |
$31.36 · SD91453 |
$36.12 · SD92553 |
$64.48 · SD93653 |
$33.32 · 092853 (min. 2) |
$41.98 · 094153 |
27/32 in. |
0.8438 |
$31.36 · SD91454 |
$36.12 · SD92554 |
$64.48 · SD93654 |
$33.02 · 092854 (min. 2) |
$40.47 · 094154 |
55/64 in. |
0.8594 |
$32.41 · SD91455 |
$38.55 · SD92555 |
$64.48 · SD93655 |
$34.27 · 092855 (min. 2) |
$43.00 · 094155 |
7/8 in. |
0.8750 |
$32.41 · SD91456 |
$38.55 · SD92556 |
$64.48 · SD93656 |
$34.02 · 092856 (min. 2) |
$40.63 · 094156 |
57/64 in. |
0.8906 |
$33.73 · SD91457 |
$39.98 · SD92557 |
$66.94 · SD93657 |
$35.98 · 092857 |
$44.93 · 094157 |
29/32 in. |
0.9062 |
$33.73 · SD91458 |
$39.98 · SD92558 |
$66.94 · SD93658 |
$35.50 · 092858 |
$43.32 · 094158 |
59/64 in. |
0.9219 |
$36.73 · SD91459 |
$40.94 · SD92559 |
$69.82 · SD93659 |
$38.98 · 092859 |
$48.13 · 094159 |
15/16 in. |
0.9375 |
$36.73 · SD91460 |
$40.94 · SD92560 |
$69.82 · SD93660 |
$38.22 · 092860 |
$45.43 · 094160 |
61/64 in. |
0.9531 |
$38.50 · SD91461 |
$42.85 · SD92561 |
$73.70 · SD93661 |
$42.18 · 092861 |
$52.20 · 094161 |
31/32 in. |
0.9688 |
$38.50 · SD91462 |
$42.85 · SD92562 |
$73.70 · SD93662 |
$41.23 · 092862 |
$50.30 · 094162 |
63/64 in. |
0.9844 |
$42.91 · SD91463 |
$46.97 · SD92563 |
$83.62 · SD93663 |
$44.42 · 092863 |
$53.77 · 094163 |
1 in. |
1.0000 |
$42.91 · SD91464 |
$46.97 · SD92564 |
$83.62 · SD93664 |
$43.18 · 092864 |
$51.38 · 094164 |
1-1/32 in. |
1.0312 |
$57.58 · SD91466 |
— |
— |
$62.03 · 092866 |
— |
1-1/16 in. |
1.0625 |
$57.58 · SD91468 |
— |
— |
$62.03 · 092868 |
— |
1-3/32 in. |
1.0938 |
$61.39 · SD91470 |
— |
— |
$69.67 · 092870 |
— |
1-1/8 in. |
1.1250 |
$65.59 · SD91472 |
— |
— |
$69.67 · 092872 |
— |
1-5/32 in. |
1.1562 |
$65.59 · SD91474 |
— |
— |
$72.05 · 092874 |
— |
1-3/16 in. |
1.1875 |
$72.62 · SD91476 |
— |
— |
$72.05 · 092876 |
— |
1-7/32 in. |
1.2188 |
$80.36 · SD91478 |
— |
— |
$79.68 · 092878 |
— |
1-1/4 in. |
1.2500 |
$80.36 · SD91480 |
— |
— |
$79.68 · 092880 |
— |
1-5/16 in. |
1.3125 |
$85.00 · SD91484 |
— |
— |
$87.32 · 092884 |
— |
1-3/8 in. |
1.3750 |
$97.91 · SD91488 |
— |
— |
$96.87 · 092888 |
— |
1-7/16 in. |
1.4375 |
$107.67 · SD91492 |
— |
— |
$109.28 · 092892 |
— |
1-1/2 in. |
1.5000 |
$118.30 · SD91496 |
— |
— |
$114.52 · 092896 |
— |
Prices from our catalog on Oct 26, 2026. Browse the Silver and Deming collection.
What do I need after the hole is drilled?
Most big holes need one more step: a tap for a threaded hole, or a deburring tool to take the sharp edge off a clearance hole. These are the ones that match the sizes above.
Next step |
What you use |
Product |
Price |
|---|---|---|---|
Tap a 5/8-11 thread |
17/32 in. bit, then |
$34.23 each (min. 2) |
|
Tap a 3/4-10 thread |
21/32 in. bit, then |
$46.33 each |
|
Tap a 7/8-9 thread |
49/64 in. bit, then |
$73.80 each |
|
Tap 1/2 in. pipe thread |
23/32 in. bit, then |
$70.83 each |
|
Break the edge on 7/16 to 25/32 in. holes |
Hand deburring tool |
$34.07 each (min. 5) |
|
Break the edge on 11/16 to 1-3/32 in. holes |
Hand deburring tool |
$58.07 each (min. 5) |
Prices from our catalog on Oct 26, 2026. Countersinking instead of deburring? See counterbore vs countersink.
FAQ
What does Silver and Deming mean on a drill bit?
It names the bit style: a large twist drill with a 1/2 in. reduced shank. The name comes from the company that made the style popular. Any maker can build one.
What is the smallest Silver and Deming drill bit?
33/64 in. Below 1/2 in., a normal jobber bit already has a shank that fits a 1/2 in. chuck.
Can I use a Silver and Deming bit in wood?
Yes, at higher speed, but a spade bit or auger is faster and cheaper in wood. S&D bits earn their price in metal.
Can I use a Silver and Deming bit in an impact driver?
No. They have a round or flatted 1/2 in. shank, not a 1/4 in. hex, and big bits need steady torque at low speed, not impacts.
Do you sell Silver and Deming drill bit sets?
We sell them by the bit, which lets you build the set your work needs. Nine-sixteenths to 1 in. in 1/16 in. steps is eight bits: $235.77 in Titan HSS round shank.
Need a size or a series that is not here? Call our team at (833) 4-ETOOLS or email sales@eldoradotools.com.
Sources: ANSI/AISC 360-22 Table J3.3 and AISC Design Guide 1, as tabulated by draftsperson.net; Titan USA and Triumph Twist Drill product specifications; Eldorado Tools catalog and drill speed chart.
First drafted Oct 26, 2026, with prices from our catalog that day.
