3.2: Radial Arm Saw
- Page ID
- 67174
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\(\newcommand{\avec}{\mathbf a}\) \(\newcommand{\bvec}{\mathbf b}\) \(\newcommand{\cvec}{\mathbf c}\) \(\newcommand{\dvec}{\mathbf d}\) \(\newcommand{\dtil}{\widetilde{\mathbf d}}\) \(\newcommand{\evec}{\mathbf e}\) \(\newcommand{\fvec}{\mathbf f}\) \(\newcommand{\nvec}{\mathbf n}\) \(\newcommand{\pvec}{\mathbf p}\) \(\newcommand{\qvec}{\mathbf q}\) \(\newcommand{\svec}{\mathbf s}\) \(\newcommand{\tvec}{\mathbf t}\) \(\newcommand{\uvec}{\mathbf u}\) \(\newcommand{\vvec}{\mathbf v}\) \(\newcommand{\wvec}{\mathbf w}\) \(\newcommand{\xvec}{\mathbf x}\) \(\newcommand{\yvec}{\mathbf y}\) \(\newcommand{\zvec}{\mathbf z}\) \(\newcommand{\rvec}{\mathbf r}\) \(\newcommand{\mvec}{\mathbf m}\) \(\newcommand{\zerovec}{\mathbf 0}\) \(\newcommand{\onevec}{\mathbf 1}\) \(\newcommand{\real}{\mathbb R}\) \(\newcommand{\twovec}[2]{\left[\begin{array}{r}#1 \\ #2 \end{array}\right]}\) \(\newcommand{\ctwovec}[2]{\left[\begin{array}{c}#1 \\ #2 \end{array}\right]}\) \(\newcommand{\threevec}[3]{\left[\begin{array}{r}#1 \\ #2 \\ #3 \end{array}\right]}\) \(\newcommand{\cthreevec}[3]{\left[\begin{array}{c}#1 \\ #2 \\ #3 \end{array}\right]}\) \(\newcommand{\fourvec}[4]{\left[\begin{array}{r}#1 \\ #2 \\ #3 \\ #4 \end{array}\right]}\) \(\newcommand{\cfourvec}[4]{\left[\begin{array}{c}#1 \\ #2 \\ #3 \\ #4 \end{array}\right]}\) \(\newcommand{\fivevec}[5]{\left[\begin{array}{r}#1 \\ #2 \\ #3 \\ #4 \\ #5 \\ \end{array}\right]}\) \(\newcommand{\cfivevec}[5]{\left[\begin{array}{c}#1 \\ #2 \\ #3 \\ #4 \\ #5 \\ \end{array}\right]}\) \(\newcommand{\mattwo}[4]{\left[\begin{array}{rr}#1 \amp #2 \\ #3 \amp #4 \\ \end{array}\right]}\) \(\newcommand{\laspan}[1]{\text{Span}\{#1\}}\) \(\newcommand{\bcal}{\cal B}\) \(\newcommand{\ccal}{\cal C}\) \(\newcommand{\scal}{\cal S}\) \(\newcommand{\wcal}{\cal W}\) \(\newcommand{\ecal}{\cal E}\) \(\newcommand{\coords}[2]{\left\{#1\right\}_{#2}}\) \(\newcommand{\gray}[1]{\color{gray}{#1}}\) \(\newcommand{\lgray}[1]{\color{lightgray}{#1}}\) \(\newcommand{\rank}{\operatorname{rank}}\) \(\newcommand{\row}{\text{Row}}\) \(\newcommand{\col}{\text{Col}}\) \(\renewcommand{\row}{\text{Row}}\) \(\newcommand{\nul}{\text{Nul}}\) \(\newcommand{\var}{\text{Var}}\) \(\newcommand{\corr}{\text{corr}}\) \(\newcommand{\len}[1]{\left|#1\right|}\) \(\newcommand{\bbar}{\overline{\bvec}}\) \(\newcommand{\bhat}{\widehat{\bvec}}\) \(\newcommand{\bperp}{\bvec^\perp}\) \(\newcommand{\xhat}{\widehat{\xvec}}\) \(\newcommand{\vhat}{\widehat{\vvec}}\) \(\newcommand{\uhat}{\widehat{\uvec}}\) \(\newcommand{\what}{\widehat{\wvec}}\) \(\newcommand{\Sighat}{\widehat{\Sigma}}\) \(\newcommand{\lt}{<}\) \(\newcommand{\gt}{>}\) \(\newcommand{\amp}{&}\) \(\definecolor{fillinmathshade}{gray}{0.9}\)3.2 Radial Arm Saw
The radial arm saw is the first machine used in the standard lumber-milling sequence.
Its primary job in WMT 101 is simple:
Cut rough lumber to rough length.
It is not used to bring a board to its final finished length.
Learning Outcomes
After completing this section, you should be able to:
- Explain the primary purpose of the radial arm saw.
- Identify its major parts.
- Explain why lumber is cut oversize during rough milling.
- Describe the basic safety requirements for using the machine.
What the Radial Arm Saw Does
On the radial arm saw, the lumber remains stationary against a fence while the motor and blade assembly moves along an overhead support arm toward the operator.
The saw is especially useful for rough crosscutting long boards.
In the WMT lab, the radial arm saw is used for rough crosscutting only.
It is never used for ripping.
The machine is well suited to rough work, but it is not the machine used when the final length of a project part must be highly accurate.
Major Parts
Important parts include:
Table — Supports the lumber.
Fence — Provides a reference surface behind the board.
Support Arm — The overhead arm along which the saw assembly travels.
Trunnion Assembly — The motor, bracket, blade, and related components that move along the arm.
Blade and Guard — Perform the cutting operation and help protect the operator.
Handle — Used to control the saw during the cut.
Power Switch — Starts and stops the machine.
Figure: Radial Arm Saw
Rough-Cutting to Length
During the standard milling sequence, cut the board approximately:
Finished length + 1 inch
That extra material gives you room to square both ends later.
For example, if a finished part will be 18 inches long, the rough blank might initially be cut to approximately:
19 inches
Do not try to make the final finished cut at this stage.
Before Cutting
Inspect the board.
Consider:
- checks or splits near the ends;
- knots near the cut line;
- severe bow or other warp;
- whether the board sits securely against the fence; and
- whether the piece will be long enough after defects are removed.
Sometimes you must cut beyond an end check before measuring the rough length of the part.
Basic Operating Principles
When using the radial arm saw:
- Place the board firmly against the fence.
- Make sure the board contacts the fence at the cut line.
- Keep your hands and fingers at least 6 inches from the line of the blade.
- Allow the blade to reach full speed.
- Pull the saw through the stock at a controlled rate.
- Do not force the saw faster than it can cut.
- Return the saw completely to the rear of the support arm after the cut.
- Remove the stock only after the saw has been returned.
Because of the blade’s direction of rotation, the saw has a tendency to pull or climb into the work. The operator must control the rate of cut.
Important WMT Limits
For normal student use:
- Use the radial arm saw for rough crosscutting only.
- Never rip lumber on the radial arm saw.
- Cut only one piece at a time.
- The minimum stock length is 12 inches.
- Maintain at least a 6-inch margin of safety from the blade.
- Special setups require instructor approval.
Warped lumber requires extra care because the kerf may close and pinch the blade.
If the board, setup, or cut does not feel secure, stop and ask your instructor.
Why This Machine Comes First
Long rough boards are harder to flatten accurately than shorter pieces.
Rough-cutting a board close to the length of the required part can:
- reduce the amount of warp in the blank;
- make the board easier to handle;
- reduce unnecessary machining; and
- preserve useful material elsewhere in the original board.
This is why rough crosscutting is the first step in the milling process.
Check Yourself
- What is the main purpose of the radial arm saw in WMT 101?
- Why is a board cut longer than its finished length?
- What is the minimum stock length for normal use?
- What is the required margin of safety from the blade?
- Why should the saw be returned to the rear of the arm before removing the stock?