/2 swingarm threads

[WooHoo]

I need some ideas on how to clean the female frame threads where the rear swingarm pivot bolts attach on a 55 /2 (Yes. I know it's not an airhead, nor a 'real' /2).

Mine came back from being resprayed with some paint in the threads, preventing the pivot bolts going in. I (mis)measured and bought a M20 x 1.5 tap but it's too wide across (the pivot bolt is 19.83mm wide).

Open to ideas.

Thanks

Tim

[datchew]

i went thru this.
You need a correct sized tap or else to do it slowly and painfully with an angled pick and a soft wire brush.

M20 x 1.5 taps are not all the same. There are + and - sizes with designations in letters or numbers (depending on standard or metric... don't remember which) which designate in .05mm increments of diameter.
These are for tapping situations which would use coated bolts or oversized bolts, etc.

you could also get a small brass/aluminum bottle brush and put it in a drill.

[datchew]

found it.

hopefully this alleviates your frustration.

LINKY

[WooHoo]

Thanks for your trouble datchew,

I don't have the tap handy at present but I'll check tonight to see if there are any 'D' markings. I don't recall seeing any but I really only checked to confirm it really was a M20x1.5 (although I'm going to caliper that too now)

I read the link you provided and found it informative. Never knew that. I think I'm well over a D12 however as the chamfered leading edge of the tap, which I'd guess takes at least 1mm off the diameter, was still too thick/wide to start on the frame thread. The link you provided had a chart citing a D12 as providing 0.0060" (0.15mm) slack which I don't think is enough to account for the difference I'm experiencing.

The problem I think is with me, and my assumption that a 19.87mm OD bolt would go into a M20 tapped thread.

Like you, I find buying taps retail for single use somewhat painful and having tried once already (It was a $20 ebay jobbie, second hand reputable brand so not a dead loss). I'll check for D markings but expect I'll try your earlier suggestion of patience and a right-angle pick... promptly followed by a brass wire wheel in a power drill.

Ta

Tim

[datchew]

my pleasure. best of luck.

ps - i forgot 1 other method which is crude, but effective. If you have a spare swingarm pivot bolt, machine a notch axially to make it into a sort of tap. the cutting face should be working when you screw it in. Of course you ruin the thing, but then you have it forever. it's basically a paint/crud chaser at that point.

[Renner]

+1
and you may consider a careful, local application of JASCO Premium Paint & Epoxy Remover to soften the stuff before removal.

Originally Posted by datchew

my pleasure. best of luck.

ps - i forgot 1 other method which is crude, but effective. If you have a spare swingarm pivot bolt, machine a notch axially to make it into a sort of tap. the cutting face should be working when you screw it in. Of course you ruin the thing, but then you have it forever. it's basically a paint/crud chaser at that point.

[WooHoo]

I checked the tap and there's no 'D' or 'H' markings.

In the end I took the cheap option and sat with a right-angle pick, a small brass brush and a can of wd40 and worried the bolts in . Took a while, but they screw in OK now and the threads look fine.

It did cross my mind to run the dremmel across the bolt threads to make an impromptu chaser. It wasn't necessary in the end and saved me a three week wait for a new bolt to arrive from the US or Europe.

I'm hoping I have all my ducks in a row to put the bike all back together once the wheels come back from a rebuild and I get permission to use the oven to bake the case.

Thanks for the advice.