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M8 × 1.25 is a metric thread designation: M identifies the metric thread system, 8 is the nominal outside diameter in millimetres, and 1.25 is the pitch—the distance between adjacent threads—in millimetres. For a cut-tap setup, a technical reference lists a 6.8 mm tap drill as a common starting point, but the right choice depends on the tap and application.
How to read M8 × 1.25
- M identifies a metric thread. Yamawa explains that “M” is the symbol for the metric thread standard: Yamawa’s thread explanation.
- 8 is the nominal major diameter: 8 mm, measured across the outside of the external threads.
- 1.25 is the pitch: 1.25 mm between corresponding points on adjacent threads.
- × separates the diameter and pitch; it is not another measurement.
Yamawa describes the metric thread angle as 60°. The designation tells you the nominal diameter and pitch, not every detail needed to establish a particular fit.
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How M8 × 1.25 differs from another M8 thread
The diameter can stay the same while the pitch changes. For example, Yamawa contrasts M8 × 1.25 with M8 × 1: both have a nominal 8 mm diameter, but their adjacent threads are spaced 1.25 mm and 1 mm apart, respectively. Match the pitch as well as the diameter when selecting a mating fastener or tap.
What drill size is used for an M8 × 1.25 cut tap?
ShopMath lists a 6.8 mm tap drill for M8 × 1.25 with a cut tap, corresponding to approximately 73.9% thread engagement under the table’s assumptions: ShopMath’s tap drill chart (data verified August 1, 2026). Treat this as a common reference, not a universal instruction. Material, tap type, and the required thread strength can affect the appropriate setup; consult the tap maker’s guidance and the requirements for your application.
#1 Best Overall
- Combination Drill and Tap Bit: Thread Size: M8 x 1.25; Hex Shank Size: 1/4". Combination drill and tap bit set can complete hole drilling, tapping, deburring and countersinking. One-step operation greatly saves processing steps and improves working efficiency.
- Wide Applications: Suitable for processing blind holes. Used for tapping aluminum, die steel, stainless steel, bronze, hard plastics, etc.. Recommended feed rate: general steel: 6-15m/min; harder steel: 5-10m/min; stainless steel: 2-7m/min; cast iron: 8-10m/min.
- Features: Self-centering point, do not need assistant center drilling or center punching. Quick change 1/4-inch hex shank can be used on power tools more easily and securely. A tapered end on hex shank can prevent excessive tapping.
- Titanium Coating: Titanium coating provides excellent corrosion resistance, greatly improves wear resistance and hardness, and reduces the coefficient of friction. High speed steel tool has high hardness and toughness, wear resistance and heat resistance.
- Tips: Use on drilling machines, tapping machines, CNC and milling machines. Use with tapping oil to get higher quality threads and more durable taps. Machine taps are suggested to be used with tap collets with overload protection.
How to identify an unknown thread
- Measure the fastener’s outside diameter. A measurement near 8 mm is consistent with an M8 nominal diameter, but diameter alone does not confirm the thread.
- Use a metric thread-pitch gauge to check the spacing. A leaf marked 1.25 should fit the thread profile consistently if the pitch is 1.25 mm.
- Confirm that both measurements match the proposed designation, then check the specified tolerance class and mating part before assembly.
This is a basic identification check, not a complete inspection or tolerance procedure. The designation M8 × 1.25 by itself does not specify every tolerance, fit, or mating-part condition, so it cannot guarantee that any two parts carrying that label will fit together.
Quick Recap
Best Value
- 【Tap Size】Length: 72mm, Thread Head: 22mm, Square Head: 5.0mm x 5.0mm (L*W), Shank Diameter:6.3mm, Pitch: 1.25mm.
- 【Drill Size】Length: 109mm, Cutting Diameter: 6.75mm.
- 【Feature】Made of M2 high-speed steel, it has high hardness and toughness. The titanium coating improves wear resistance and prolongs service life.
- 【Application】Suitable for most metals, copper, alloy steel, cast iron, aluminum, brass, abrasive steel, A3 steel, iron plate ETC.
- 【Package Included】1pc M8x1.25 Ti-Coated tap and 1pc 6.75mm Ti-Coated drill bit.
Rank #4
- Set contains high speed steel plug hand tap and matching high speed steel drill bit
- High speed steel plug hand threading tap is popular for use in general machine tapping or cnc tapping
- Black oxide drill bit is ideal for production, maintenance or portable drilling jobs
- M8 x 1.25 hss plug tap and matching 6.75Mm hss drill bit in plastic pouch
- Set comes in plastic pouch
Rank #3
- Tap and Drill Bit: Tap thread size: M8 x 1.25, drill bit diameter: 6.8mm / 0.27". High-speed steel tool has high hardness and toughness for wear resistance. Good for general purpose applications.
- Spiral Point Tap: Spiral point design, downward chip removal, right hand thread cutting. Suitable for processing through-hole threads, and tapping aluminum, stainless steel, bronze, hard plastics. Titanium coating provides excellent corrosion resistance and wear resistance.
- Twist Drill Bit: Spiral chip space design for fast and clean chip removal. Sharp cutting edge provides smooth cutting and no glitches. Cobalt high speed steel tool features high hardness (HRC65-66) and high red hardness, high wear resistance
- Usage of Tap: Used on drilling machines, tapping machines, CNC and milling machines. Use with tapping oil to get higher quality threads and more durable taps. Machine taps are suggested to be used with tap collets with overload protection.
- Tips of Drill Bit: Suitable lubricant is conducive to cutting or cooling, making cutting easier, improving smoothness and dimensional accuracy. Select an appropriate feed rate and cutting speed to improve the tool life.
Rank #2
- 【Size】Include M8x1.25 M2 steel tap and 6.75mm M2 HSS drill bit with round shank,all stored in a storage box for easy carrying.
- 【Top Quality】All the taps and drill bits in our tap tool sets are made of top-grade M2 steel and are titanium-plated to ensure its high hardness, rust proof, sturdy and durable.Fits most drill driver brands on the market. The taps in this set can be driven by hand and machine.
- 【Widely Applications】This drill tap set are designed to Create new threads or re-thread damaged or jammed threads. Thread tap can process through holes or shallow blind holes, with downward chip removal, right-hand cutting, and fast and accurate tapping. Suitable for most metals, stainless steel, cast iron, aluminum, aluminum alloy, bronze and hard plastics.
- 【Warm Tips】Drill holes with a twist drill bit first, then tap with a thread tap. Tapping and drilling angle should be 90 degrees vertical and stable. The higher the hardness, the slower the speed. The tapping depth should not exceed 1.5 times the diameter of the tap (For example, the diameter M6x1 is about 6mm, and the depth should not exceed 9mm.)
- 【Satisfaction】RURITKIT aims to provide high-grade products and customer service to all customers. Any problems, just contact us and our after-sale team will solve your problems ASAP.
Before choosing a tap or mating fastener
- Verify both nominal diameter and pitch; an M8 fastener with a different pitch is not interchangeable solely because it is also M8.
- Use a matching M8 × 1.25 metric tap when making an internal thread, and select the drill size using guidance appropriate to the tap type, material, and application.
- Check the required tolerance class and the counterpart’s specification where fit matters. Those details are not encoded by M8 × 1.25 alone.
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