Date: Sat, 18 Aug 2012 12:48:15 -0500
Reply-To: mcneely4@COX.NET
Sender: Vanagon Mailing List <vanagon@gerry.vanagon.com>
From: Dave Mcneely <mcneely4@COX.NET>
Subject: Re: windshield wiper repair
In-Reply-To: <502f280e.9496cc0a.153a.5c9a@mx.google.com>
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Once I had a good hole with the drill (and I did), I had no trouble with tapping. I did not use a jig. My tap set includes a double handled handle (hows that for mangling the language). The tap fits into a center clamp and one turns the tap from two sides to keep even pressure. That is the only kind of tap handle I've ever seen, but I'm no machinist. Working very slowly, with oil, I was able to keep the tap moving without it going off course. After flushing the hole repeatedly with oil until I could get no debris to rise out of it, a 6 mm bolt turned in smoothly. It did not bottom on the threads, shimming with a washer was required to get the bolt to tighten on the wiper arm axle. I just think the washer arm axle is too worn to have enough metal left to respond properly to the splines. The wiper did work for 3 minutes by my watch, and I was about to say, "Ok, decent job after all," and turn the wipers off when the wiper started to only travel part way on its course, then just stopped moving. I could see that the shaft was turning inside the axle.
I'll do better next time. I do know how to drill, just doing jobs like this so seldom, and being older than God, I just forgot to drill a pilot hole first. I've learned from trying to do this job, and I appreciate all the pointers given. I'm less frustrated with myself than I have usually been when I've found a job eluded my efforts.
BTW, Alistair, I did use a prick punch and then a larger center punch. The stud (which was cut down actually into the conical shaft in order to get a flat surface to work with) showed no tendency to move, though I whacked pretty good, but with a light ball peen hammer.
So far as center is concerned, I hit what I perceived as center with the prick punch, and examined the stud with a 3x botanist's field lens. I accepted that I had hit center, and then whacked it with the center punch. I had used this procedure originally, when I forgot to make a pilot hole and the drill moved sideways. I did try to enlarge the dimple a bit by hitting it again three times around its circumference. It seemed to work, and with the lens I was satisfied that I was on center. A micrometer would have made for better precision, and one might scribe lines through the diameter of the stud surface, I suppose, marking the center. But I did not do that.
Though I did not accomplish this job as I'd hoped, I really do appreciate all the pointers and advice given.
I might as well try the LocTite. As I remarked before, I have nothing to lose except an already damaged part.
mcneely
---- David Beierl <dbeierl@ATTGLOBAL.NET> wrote:
> At 10:40 PM 8/17/2012, Alistair Bell wrote:
> >I want to add to this excellent description, maybe differing a bit...
>
> Awww...I was hoping you'd go a little into how to actually find the
> darn center in the first place. And how to walk a punch mark sideways. ;-)
>
>
> >I'd use a fine prick punch to mark the hole, then if you want punch
> >again with 60 degree point pu[n]ch.
>
> Good point (no pun intended). But on the shaft we're talking about,
> it's probably only held up by an E-clip, so we can't bang on it very
> hard without injuring something; so we can't make a big hefty
> center-pop with a hammer since we can't reach the back of the shaft
> to back it up with a weight. The fine punch wants a small hammer
> (8-oz or less ideally, I think), and a spring-loaded automatic center
> punch may be safer for increasing the size.
>
> > Then as Bill Monk has said, use a small (1/16") drill to enlarge
> > punch divot. The small flexible drill does a better job in this
> > case than a centre or spotting drill.
>
> Yes, I agree. Keep the center drill in the tool room. It's actually
> quite unforgiving with its little stiff point and rigid body.
>
> > You do not need to drill very deeply with the 1/16" bit, just make
> > the punch mark a hole. Then go on to the 1/8" bit and follow with
> > tap drill size.
>
> I still like the 1/8" pilot point bit. Probably can start right from
> the beginning with it, the pilot makes it disinclined to wander
> whilst drilling, and it's still quite flexible (but not as fragile as
> a 1/16" bit). I haven't measured the pilot but it's pretty small.
>
>
> >Tapping the hole in situ is tricky. Hard to keep tap perfectly
> >aligned, as is it is hard to keep drill bit aligned.
>
> And of course whilst the drill bit will flex a bit, the tap is
> practically glass hard and won't. Which is why you use a proper tap
> handle or die stock that lets you pull from both sides of the tap, as
> you're much less likely to break it off short that way. Don't use a
> tee-type handle with its crossbar stuck out to one side, balance it.
>
> Starting the tap is the trickiest part, that part you use a drill
> press or other solid jig for if at all possible. Getting the first
> few partial threads to bite at all, and precisely straight in, can be
> very difficult; and whatever angle it starts at it will continue
> until the job is finished or it finally gets an impossibly large bite
> of the wall, jams and breaks off.
>
> >All in all, I'd say it is a tricky job to get a good tapped hole in shaft.
>
> Amen, brother.
>
> Yours,
> David
--
David McNeely
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