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How to Use a Quick Change Tool Post

Guide · Updated October 28, 2026

A quick change tool post lets you swap pre-set tool holders in seconds and land back at the same height. Each holder has a height-adjusting collar, so once a tool is on center it stays there. Wedge-type posts (like Aloris and clones) repeat best; piston types are common on small lathes.

Record repeatable offsets

Check your diameter after each tool change with a mic proved on gage blocks. The free Gage Block Calculator builds the stack.

Step by step

Mount the post: Clean the compound top and post base; tighten the stud nut firmly.
Load a tool: Clamp the tool in the holder with minimal stickout using the holder screws.
Set center height: Hang the holder on the dovetail, turn the height collar until the tip is on center, then lock the holder.
Lock the collar: Snug the collar lock so the height is saved for the next mount.
Set the angle: Rotate the post to the needed tool angle and lock it; many people keep the post fixed and set holder angle instead.
Touch off: Take a skim cut, measure and zero the dial or record the offset for that holder.
Change tools: Drop in the next pre-set holder, lock, and use its recorded offset.

Worked example

Set the turning tool on center, skim a part and measure 1.2485 in, then zero the cross-slide diameter dial at that cut. Swap to a second pre-set holder and touch the same diameter: the dial reads 0.0120 in, so that holder’s offset is +0.0120 in. To turn 1.000 in with the second tool, you need 1.2485 − 1.000 = 0.2485 in off the diameter from the touch-off, so dial to 0.0120 + 0.2485 = 0.2605 in on the diameter dial. Good wedge posts repeat within about 0.0002 in, so a skim cut confirms it.

Wedge vs piston

Wedge posts pull the holder against the dovetail with a lever and repeat best. Piston posts push out against the holder and are fine for hobby work but can rock slightly on heavy cuts.

Common problems

A tool drooping under load means the holder is not locked or the collar is loose. Chatter means too much stickout or a post not tightened to the compound. Height drift means burrs or chips on the dovetail.

Tips

Height: set tool height.
Inserts: carbide insert basics.
Boring: use a boring bar in its own holder.

FAQ

What is a quick change tool post?

A post with dovetail holders that each keep a preset tool height.

How repeatable is a QCTP?

Good wedge posts repeat within a few tenths.

How do I set tool height?

Turn the height collar until the tip is on center, then lock it.

Wedge or piston?

Wedge for repeatability and rigidity; piston for light work.

Should I buy extra holders?

Yes, one per frequent tool saves setup time.

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