Heavy Duty Spark Plug Gapper

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Part# 12-03389
MFR Model# ATS420


This professional heavy-duty spark plug gap setting tool is completely portable for field use, yet precise enough to set gaps to within 0.001". The precision screw drive with its comfortable knurled knob gaps any type of Massive Electrode Aviation Spark Plug reliably and without any danger of damaging the spark plug. Simply screw the spark plug into the base of the tool and turn the knob to the required gap width. Very easy to use.


  • Sets gaps to within 0.001"
  • Precision CNC Machined from 4160 Tool Grade Steel
  • Attractive Nickel-Cadmium finish resists rusting
  • Knurled palm grip keep the tool from slipping in hands
  • Compatible with all Champion, and AutoLite Massive Electrode Spark Plugs
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Please note, Aircraft Spruce's personnel are not certified aircraft mechanics and can only provide general support and ideas, which should not be relied upon or implemented in lieu of consulting an A&P or other qualified technician. Aircraft Spruce assumes no responsibility or liability for any issue or problem which may arise from any repair, modification or other work done from this knowledge base. Any product eligibility information provided here is based on general application guides and we recommend always referring to your specific aircraft parts manual, the parts manufacturer or consulting with a qualified mechanic.

Q: Does this Heavy Duty Spark Plug Gapper tool fit 14mm plugs?

No, this unit is used on 18mm aviation spark plugs.

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