Tap needed to clear out frame threads.

[/quote]Interesting tip, not seen this before, do you think it would work with BB threads and old steel cups ?[/quote]

Never tried but yes it should work fine. Probably just need to be a bit careful when 'starting' to screw in the cup to avoid crossthreading since the thread is fine and a large diameter.
When i was a car mechanic years ago i made a few of these and they were very useful. Imagine scraping an old water pump gasket off a rusty engine block, the old pump mounting holes in the block getting contaminated with rusty coolant, old gasket and maybe ancient dried-up thread lock or sealant. Just run these 'taps' in and out a couple of times, blast of air, drop of oil, good as new!

As mentioned i suggest longer and deeper cuts than the sample photo. And only two cuts as bottle bolts are small diameter. Two long deep cuts will be better than the six tiny cuts shown in the photo. On a larger bolt like something above M10 i'd probably make three cuts. Hold the bolt head in a vice while making the cuts. I expect a steel bolt would be better than aluminium (harder wearing and won't fail in use).

Great tip, I did exactly the same thing with my car when the disc retaing holes in the hub were gunked up:

the slot down the length of a bolt is reasonably ok but a tap is better. M5 and M6 are not that expensive - you can buy online or in tool shops - Machine MArt will sell them and am pretty sure Argos do too (or used to).

Unless it is a non-standard thread, there is no point messing with the slotted bolt and the tap will always cut a better thread - s what it is designed for!

GuyWood":1shfq96f said:

Great tip, I did exactly the same thing with my car when the disc retaing holes in the hub were gunked up:

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Yes! Excellent example!
Yes a real tap tool would be first choice but for the purpose of cleaning existing threads this homemade 'cut bolt' is perfectly acceptable and now i think about it you could even use one to hold your bottle cage on meaning you're always carrying it with you on the trail!

thanks for that, while a tap is obviously better, the specific bottom bracket thread ones are over £50 for ones I've seen whereas undamaged steel loose cups are as cheap as chips or at least they were until this gets out...............

daugs":toqdws3c said:

thanks for that, while a tap is obviously better, the specific bottom bracket thread ones are over £50 for ones I've seen whereas undamaged steel loose cups are as cheap as chips or at least they were until this gets out...............

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Used this method to clean out a very clogged up thread on an aluminium frame only last week.

Most loose bb cups will be hard which makes them even better for cleaning up threads but means that you'll probably need a grinder rather than a file to do the slots.

I got my Taps from good old Lidl/Aldi. Then a few weeks later I was handed some old 'bike' taps. Some funny old sizes in them.

But it's given me an idea on how to get the other pedal tap.

Here's one from this weekend using an old bottle bolt. Yes the proper tool is a tap but if you haven't got one this works just fine for cleaning an existing thread. Use WD40 or similar.

M5x0.8 for bottle bosses etc.

The cuts in an old BB cup trick works very well, used it a few times. The old and very cheap cup n cone ones work best IMO. I even hardened and tempered one once, worked a dream on shonky cross threaded BBs

How about one of these :?:

http://www.uktools.com/thread-file-metric-p-255.html