91 Civic Si Thread Hole Chaser-Head Bolts

[Gito]

Own a 1991 Honda Civic Si and getting ready to reinstall the engine head.

Need to clean the engine block threads prior to installing new head bolts (OEM Honda).

Are there any recommended thread cleaning chasers that forum members have used in the past. I found a M10x1.25 ARP thread cleaning chaser online but the length of the chaser is not specified.

Any advice is greatly appreciated

 

[Cujet]

You can also cut a single, sharp vertical slot in an old head bolt, using a grinder with a thin cutoff wheel. Makes a great thread chaser as it does not cut the threads to a different shape. Run it in and out with a little light oil and clean the hole properly when finished.

 

[Mainia]

Link image seem the same, but different links to different options for you.



Forming tap would be my choice.

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Other options.

McMaster-Carr

McMaster-Carr is the complete source for your plant with over 595,000 products. 98% of products ordered ship from stock and deliver same or next day.

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[Imp4]

Forming tap would be my choice.

I'm going to have to disagree with you here.

A form is a particularly poor choice for this application because of how form taps work. Form taps cold form threads by displacing and cold flowing the base material into the thread profile instead of cutting it (which is why it's called forming). As such, form taps typically have little to no flute relief to allow chips to move out of the thread profile while the forming action is taking place. Using a form tap to chase dirty threads will just imbed the junk in the threads into the engine block base material.

And we won't even get into differences in tap drill specs and the higher probability for breaking form taps when standard tap drill sizes are used.

What @Gito needs here is either a standard plug tap or a bottoming tap if he wants to ensure fully cut threads as deep in the hole as is practicable.
Both plug and bottoming taps have flute relief so that the junk that the tap removes has a place to go during the chasing process.

Bonus for @Gito in that plug or bottoming taps are typically cheaper than form taps.

The method @Cujet suggested will also work in a pinch but there is a technique to grinding the relief that he shows and frankly whoever ground the relief on that screw did a pretty poor job of it.

 

[mk378]

This is a situation where it is easy to do more harm than good. Clean the holes of any obvious debris and liquids then check if a head bolt can thread in smoothly by hand.

 

[Greasymechtech]

The thread is already there. Forming tap wouldn't be an issue. He is not tapping new threads. Just needs to clean and true the old threads.

Forming tap or thread chaser(works just like a forming tap) would be my 1st choice. I would not use a normal tap from a tap/die set.

 

[Cujet]

The method @Cujet suggested will also work in a pinch but there is a technique to grinding the relief that he shows and frankly whoever ground the relief on that screw did a pretty poor job of it.

That was the only image I could find with a quick search. I agree, a bit of care to do it right and create a sharp edge on both sides is important.

 

[Soft Cars]

I found a M10x1.25 ARP thread cleaning chaser online but the length of the chaser is not specified.

Any advice is greatly appreciated

SKU : 50-2619-0005 - Metric Rethreading Tap M10 x 1.25

Manufacturing professional tools since 1932

www.langtools.com