Five free practice questions on drill press drilling and tapping: block D of the Red Seal 429A Machinist exam, about 9 of its 135 questions. They are in the exam's format: four options, one correct answer. Answer each one before opening the explanation. No account, no email.
01The questions
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Which drill preparation stops a twist drill from grabbing and pulling itself into brass?
- Grind extra lip clearance behind each lip.
- Grind a small flat on each lip to zero rake.
- Use a high-helix drill for faster chip flow.
- Grind a 135° split point to reduce the thrust.
Show the answer
B. Correct. The helix gives a standard drill a positive rake at the lips, and in brass that rake lets the drill screw itself into the work, worst at breakthrough. Dubbing a narrow flat on the face of each lip takes the rake to about zero, so the drill scrapes and feeds only as fast as it is pushed.
Why not the others
A. Extra lip clearance weakens the edge and makes the drill more aggressive, so it digs in more, not less. Grabbing in brass comes from the rake on the lip face, which is removed by dubbing the lips.
C. A high-helix drill has even more positive rake at the lips, so it grabs brass worse. Fast-spiral drills suit soft, gummy metals such as aluminum; for brass the lips are dubbed to zero rake.
D. A 135° split point is for hard and tough steels: it cuts thrust and keeps the drill from walking at the start. It leaves the positive rake at the lips, which is what makes a drill pull itself into brass.
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A part is clamped in a vise on an upright drill press. For the stiffest set-up, where is the table set before drilling?
- At mid-height, so the quill works at mid-travel.
- With the drill just clear of the work, quill retracted.
- As low on the column as it will go, for chip clearance.
- With the quill run well out, so it can reach the work.
Show the answer
B. Correct. The quill is stiffest when it is barely extended. Raising the table until the drill just clears the work, with the quill up, keeps overhang short and leaves the full quill stroke for the hole. Lock the table to the column before drilling.
Why not the others
A. Starting at mid-travel throws away half the quill stroke and leaves the quill extended while it cuts. The stiff set-up starts with the quill retracted and the table raised until the drill just clears the work.
C. A low table forces the quill to run far out to reach the work, the least rigid way to drill. Chip clearance comes from parallels and the table's centre hole, not from dropping the table.
D. The further the quill hangs out of the head, the more the drill can deflect and chatter. Bring the work up to the drill with the table instead and keep the quill nearly retracted.
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A 10 mm drill's margins are worn round for about 3 mm back from the outer corners. How is the drill reconditioned?
- Touch up the lips and keep the point length.
- Stone the margins to blend in the worn section.
- Grind back past the worn margins and resharpen.
- Grind extra lip clearance to free the corners.
Show the answer
C. Correct. The margins set the drill's size, and a drill tapers slightly smaller toward the shank (back taper). With the margins worn at the point, the body behind is larger than the cutting end, so the drill cuts undersize and binds. Grinding back until full margins remain and forming a new point restores the size.
Why not the others
A. Touching up the lips sharpens the edges but leaves the worn, undersize margins at the point, so the drill still cuts small and binds behind the cut. The point is ground back past the wear.
B. Stoning the margins removes more of the land that sets the drill's size and guides it in the hole. The worn section has to be ground off, not blended.
D. Lip clearance acts on the cutting edges; it does not restore diameter lost at the margins. The drill would still cut undersize and bind. Grind back past the wear and resharpen.
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Two drilled holes, 10.00 mm and 14.00 mm in diameter, measure 62.40 mm between their far walls with the inside jaws of a caliper. What is their centre distance?
- 38.40 mm
- 74.40 mm
- 55.40 mm
- 50.40 mm
Show the answer
D. Correct. The reading spans from the far wall of one hole to the far wall of the other, and each centre lies one radius inside its wall: 62.40 − 5.00 − 7.00 = 50.40 mm.
Why not the others
A. 38.40 mm subtracts both full diameters (62.40 − 10.00 − 14.00), which gives the web of metal between the holes, not the centre distance. Each centre is one radius in from its far wall, so subtract 5.00 mm and 7.00 mm.
B. 74.40 mm adds the radii, as if the reading had been taken between the near walls. Across the far walls the radii are subtracted: 62.40 − 5.00 − 7.00 = 50.40 mm.
C. 55.40 mm takes off only the larger hole's radius (62.40 − 7.00). Both centres sit one radius inside their far walls, so both radii come off: 62.40 − 5.00 − 7.00 = 50.40 mm.
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A 3/8–16 UNC thread must reach close to the bottom of a blind hole in 1018 steel, tapped with a tapping head on the drill press. Which tap is best?
- Straight-flute bottoming tap.
- Spiral-flute bottoming tap.
- Spiral-point plug tap.
- Straight-flute taper tap.
Show the answer
B. Correct. The spiral flutes lift stringy steel chips up and out of a blind hole as the tap cuts, and the short bottoming chamfer carries full threads close to the bottom. Set the stop so the tap stops short of the bottom of the drilled hole.
Why not the others
A. A straight-flute bottoming tap reaches the bottom but cannot lift stringy steel chips out; they pack in its flutes. It suits hand tapping with frequent backing out, not power tapping a blind hole in steel.
C. A spiral-point (gun) tap shoots its chips ahead of it, down into the hole. That suits a through hole, but in a blind hole the chips pack the bottom and can jam or break the tap.
D. A taper tap's long chamfer leaves several incomplete threads at the bottom of a blind hole, and its straight flutes do not lift the chips out. A spiral-flute bottoming tap does both jobs.
02Answer key
| Question | Answer | Sub-task |
|---|---|---|
| Q1 | B | Plans operation of drill presses |
| Q2 | B | Sets up jigs, fixtures and work holding devices for drill presses |
| Q3 | C | Sets up tooling for drill presses |
| Q4 | D | Drills holes using a drill press |
| Q5 | B | Performs tapping using a drill press |
03What block D covers
Block D is hole work on the drill press: choosing the machine, planning the job, speeds and feeds, vises, jigs, fixtures and clamping, and drills, reamers, taps and other tooling. On the operating side it covers drilling, countersinking, counterboring, chamfering and spot facing, tapping with a tapping head, and finishing holes by reaming.
The Red Seal Occupational Standard names this block “Machines using drill presses”. It carries 6.7% of the exam, about 9 of the 135 questions, split across two tasks. The share column is each task's weight within the block, as the standard publishes it.
| Task and its sub-tasks | Share of block |
|---|---|
| Sets up drill presses Selects drill press types; Plans operation of drill presses; Selects drill press speeds and feeds; Sets up jigs, fixtures and work holding devices for drill presses; Sets up tooling for drill presses | 56% |
| Operates drill presses Drills holes using a drill press; Cuts countersinks, counterbores, chamfers and spot faces using a drill press; Performs tapping using a drill press; Finishes holes using a drill press | 44% |
04What the questions turn on
Pilot drill just over the web
A large drill's chisel edge pushes metal aside and accounts for much of the feed thrust. A pilot hole just larger than the web thickness removes that work; a much bigger pilot makes the large drill grab and chatter.
Clamp the vise before big drills
A large drill's torque, and the sudden grab at breakthrough, is more than a loose vise can resist. Clamp or bolt the vise to the table, or set it against a stop on the side it would swing toward.
The rpm formula takes the diameter
On inch work, rpm is 12 times the cutting speed divided by π times the drill diameter. Using the radius doubles the answer and leaving π out more than triples it, so check which figure went in.
Drill size before reaming
A machine reamer needs a set amount of stock. Subtract the drill's decimal size from the reamed size and confirm the difference falls inside the allowance the reamer maker gives, so the reamer takes a light, even cut.
05The other blocks
The 429A exam has eight blocks. Each has its own page of free questions:
The 429A Machinist practice exam page describes the full question bank. How these questions are written and checked: how our questions are made. Found a mistake? Tell us and we will fix it.