Chasing threads question ...

[k-rod]

Hello fellow bike builders (and machinists).

I am on the tail end of a thorough re-fresh of a mid-eighties Sherpa/Rocky Mtn bike, and am finding the fender eyelet threads to be fouled with powder-coat material. While I do have a great set of (brand new) taps ans dies (5mm/.8 is the one), I've never embarked on such an exercise and want to ensure I don't 'screw' things up (pardon the pun).

So - the Q is: do I just have at it with the tap, and 'tap 'er in' to each eyelet hole (carefully), while using a bit of oil to lube things through ... or ... is there some sort of thread chasing technique or secret that y'all might wish to share with me, so that I am having the best chance to doing this properly and successfully ... ??

And - thank you gazillions for your time and help!! :!:

kr

 

[Captain Stupido]

Turn them in, don’t tap them in. One turn in, half a turn out to clean the threads as you go... Am I stating the obvious? Sorry if so. No expert, but just did the same job on the rusty eyelets on my Dawes.

 

[Graham_hkr]

Re:

Initially if you're not familiar with the process it may help using an intermediate tap first, it'll just be easier to start & reduce the possibility of cross-threading!

 

[Bimly]

Practice on some old nuts. Rusty, painted, crud filled. Stick them in a vice or mole grips and have a go. Its likely you got taper taps, rather than intermediate, if you got a home kit. They are designed to start a tap in a drilled hole with less chance of cross threading. They are not as good as plug (intermediate) taps for what your doing, but will do the job just fine. Just go steady.

In a pre threaded hole, the tap should go through really easy, even if blocked with powercoat. If you feel any resistance or see anything other than powder residue coming out stop.

It may be good to clear the hole as much as possible first.

Once you have done a couple, you should be fine.

 

[k-rod]

Re:

Thank you people ... will have a go at it in a day or so ....

 

[k-rod]

Re:

Well - that was easy enough!

Pretty simple, really ... just a slight bit of positive pressure on the tap, while ensuring that it remains aligned with the hole ... and gradual turns in and then back out again - using only finger pressure (I turned the chuck by hand, without using the t-handle) with some light oil for a lube ...

and presto - perfectly cleaned/reamed threads.

 

[Bimly]

Great news. Sometimes you just need to have a go. On with the build.

 

[Graham_hkr]

Re: Re:

Well - that was easy enough!

Great stuff..... now we need to see some pictures, we love pictures...