Help Identifying Clutch Screw Thread Pitch

[GoK4rtFanatic]

I recently bought a small engine replacement clutch for a stihl fs38 string trimmer. I intend to mount this on the mini dirt bike I'm building (the engine is very small so durability is not a question. I have identified the clutch pack itself as a 3/8-24 thread, but I cannot determine the thread pitch of the screw within the drum itself. Does anyone happen to know what the size might be? If not is there an easy way to measure this? The screw obviously is not removable.

Other helpful info

- I believe the screw is a T27 head
- https://www.amazon.com/dp/B07YYX2L8K...roduct_details

(Amazon link to clutch I bought above)

(Picture of clutch drum below)



The screw pictured within the clutch drum



View from the other side

[52 Ford]

If it has a Torx head, it's likely metric. Measure the diameter of the screw thread the best you can. Doesn't have to be to the thousandth or whatever. I'm guessing it's M5, M6, or M7.

Not sure about the thread pitch. Can't tell from that angle.

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[leightrepairs]

Knowing what size torx bit fits would help narrow choices down.

[52 Ford]

Knowing what size torx bit fits would help narrow choices down.

He said T27. That SHOULD be an M5.

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[52 Ford]

Also, this just occurred to me - you didn't mention what the screw did. Does it go into the end of the crank? If so, why not just measure the hole in the crank.

Buy a set of calipers. I've heard good things about these. The price is certainly fair and they read both metric and inch, which is pretty unique amongst dial calipers. https://www.amazon.com/Anytime-Tools...ustrial&sr=1-2

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[GoK4rtFanatic]

So a few updates. I went to the hardware store and it appears to be an M4-0.7 but not exactly sure. Also it does go into a crank yes, but I am not buying it as a replacement part so I don’t actually have the machine it fits. I have some digital calipers but unfortunately they will not fit down the cover well enough to get a reading. I will keep you guys posted, thank you so much for all the help.

[AlabamaJoe]

I bought this a couple of years ago and it has come in quite handy at times.



Here's the current link -

https://www.amazon.com/gp/product/B0...?ie=UTF8&psc=1