Date: Sat, 21 May 2011 13:48:44 -0500
Reply-To: Jim Felder <jim.felder@GMAIL.COM>
Sender: Vanagon Mailing List <vanagon@gerry.vanagon.com>
From: Jim Felder <jim.felder@GMAIL.COM>
Subject: Re: Steering wheel locked after replacing blower motor
In-Reply-To: <4dd7f990.4969e50a.33ba.ffff9fad@mx.google.com>
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David,
Great job of describing thread restoration and handling taps. I have just
one thing to add that came my way as an army machinist, and I'll bet most
folks don't know it. When tapping, is is best not to just keep turning the
tap (or die) in. It should be turned in about a quarter turn, then backed
out to break the chip, then forward again, then back until the job is done.
Don't forget a lubricant and don't be in such a hurry that you fail to
remove the taps to clean the flutes of material before proceeding.
Jim
On Sat, May 21, 2011 at 12:42 PM, David Beierl <dbeierl@attglobal.net>wrote:
> At 12:58 PM 5/21/2011, Scott Daniel - Turbovans wrote:
>
>> that's just how persistent and determined one needs to be occasionally,
>> to produce the result.....
>> when working on cars. Takes real tenacity sometimes.
>>
>
> Especially the first time, or if it's been long enough that you've
> forgotten the little twists you learned the last time.
>
> The especially fun part is going through nineteen of the twenty
> reassembly steps and discovering that you left out step four. Or
> being *sure* you'll remember what all the various nuts, washers etc
> are for, then having to wait a week...baggies and a Sharpie are your
> friend.
>
> And Phil - do yourself a favor, get a couple torque wrenches, one
> 3/8-drive one that goes to say 75 lb-ft and later a bigger one for
> maybe 150 lb-ft. All fasteners have a proper torque, and especially
> when you're working with bolts threaded into the aluminum parts it's
> remarkably easy to suck the threads right out of the hole. If you're
> tightening a fastener and the torque starts to drop instead of rise,
> it's too late, you have to put in an insert.* This may well be the
> fault of the guy ahead of you. I've been working on a van from New
> Mexico where it seems as though every second fastener is stripped
> out. Forward transmission mount (this is in steel) had one good
> bolt, two stripped holes, and one hole with a broken-off tap in
> it. And it was at least two different people who did it. One of
> them stripped the alternator mount bolts, put in inserts and then
> stripped out the inserts. That takes talent.
>
> Click-type wrenches are convenient but their calibration is
> iffy. Beam-type are much cheaper and calibration is permanent if you
> don't wreck them. I have a click-type that goes from 20-150 lb-ft
> and has a ratchet (that's the convenient part), and a three beam-type
> of descending sizes. The big one I use to check the calibration on
> the click wrench, as well as for more critical fasteners.
>
> *Thread inserts work by drilling and tapping a larger hole, then
> threading in an insert that acts as a new set of threads. Helicoil
> and Time-sert are two brands. Drilling is not hard if there's enough
> space; tapping is difficult to get lined up straight because the tap
> will eat its way in whatever direction it gets started. Also taps
> are extremely hard, which means they're extremely brittle; and once
> you've broken one off in the hole you've got a whole new set of ugly
> problems. Tapping is both an art and science unto itself, and
> good-quality taps aren't cheap. The thread-insert ones are special
> sizes and come with the insert kit (tap, inserting tool, a few inserts).
>
> I find it very useful to keep taps and dies on hand in M6x1, M8x1.25,
> M10x1.5. These are mostly for chasing existing threads to clean them
> up, you'll be surprised the difference this makes on
> reassembly. Bottoming taps (google) are harder to find, so I
> typically get two plug taps and carefully grind the end off one to
> make a bottoming tap.* Those are for chasing closed holes. Pep Boys
> sell Vermont-American taps and hexagonal dies which are what you want
> for chasing the threads on bolts. V-A is a nothing-special brand but
> they work ok. Beware tap wrenches that have you apply your force on
> one side - recipe for a broken tap. Slide the handle so you're
> pushing on both sides equally. Hex dies you can use a wrench on
> carefully, or clamp them in a vise. You can also get handles for
> them, and if you're actually going to make a thread you need
> one. For chasing you can often do it dry, but tapping fluid is
> better and oil is better than nothing.
>
> *If they're carbon steel taps (give lots of bright sparks on the
> wheel) you have to keep them cool with *frequent* dips in water. If
> the end turns blue or even straw color you've softened the whole
> end. High speed steel (minimal dull sparks) it's better not to dip
> in water, ok to let them get hot.
>
> Yours,
> David
>
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