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How to Cut a Taper with a Taper Attachment

Guide · Updated October 28, 2026

A taper attachment moves the cross slide as the carriage travels, using a guide bar set to the taper half-angle. It cuts long tapers with power feed, inside or out, without offsetting the tailstock, and the setting repeats from part to part.

Check taper diameters

Check diameters at two marked points with a mic proved on gage blocks. The free Gage Block Calculator builds the stack.

Step by step

Work out the half-angle: Half-angle = atan(TPF ÷ 24), where TPF is taper per foot on diameter.
Set the guide bar: Set the bar to the half-angle or to the TPF scale.
Engage the attachment: Clamp the slide to the bed and connect the cross slide per the maker's method.
Take up backlash: Start each pass with the carriage moving a little before the tool reaches the work.
Rough: Turn the taper leaving 0.010 in.
Check the taper: Measure diameters at two points a known distance apart.
Adjust and finish: Fine-tune the bar and take finish passes.

Worked example: 3/4 in per foot

TPF = 0.750 in. Taper per inch = 0.750 ÷ 12 = 0.0625 in on diameter. Half-angle = atan(0.750 ÷ 24) = atan(0.03125) = 1.790°. Check: measure 1.000 in apart; diameters should differ by 0.0625 in. If they differ by 0.0600 in, the taper is 0.0025 in short per inch, so the bar needs atan(0.0625 ÷ 2) − atan(0.0600 ÷ 2) ≈ 1.790° − 1.718° = 0.072° more.

Telescoping vs plain

A telescoping attachment leaves the cross slide screw connected, so you feed with the cross slide; a plain attachment disconnects it and you feed with the compound.

Checking tapers

For fits, blue the part and try it in the mating taper or a ring gage; full contact along the length means the angle is right.

Common problems

Taper changes along the length: backlash not taken up. Wrong angle: TPF set on radius, not diameter. Ridges: slide gibs loose.

Tips

Compound: compound for short tapers.
Basics: taper basics.
Measure: measure a taper.

FAQ

What does a taper attachment do?

It moves the cross slide as the carriage travels to cut tapers.

How do I set the angle?

Half-angle = atan(TPF ÷ 24).

Can it cut internal tapers?

Yes.

Why take out backlash?

So the taper is consistent from the start of the cut.

Is TPF on diameter?

Yes, taper per foot is on diameter.

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