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MG TD TF 1500 - Never Cross Thread Again??

"I know they are not cross threaded. Though very easy to do I use a technique that makes this impossible."

Peter, could you expand a bit on that? I've ruined enough screws and other fittings to need a good lesson. Thanks. Jud
J K Chapin

Sure Jud. When you are going to fit a bolt or machined screw, first ensure the threads on both the screw & the nut or threaded item are intact & clean. Carefully remove any signs of rust, minor burring or damage with a wire brush or fine Geneva file. If the damage is moderate, clean up both items with a tap & die. Failing that, replace the items.

The first action is to gently turn the screw in the opposite direction about half a turn until you feel that it seats & that the thread is engaged. If any resistance is felt, stop, remove the screw & examine both for any sign of damage. NEVER just start turning in the correct direction! The key is to ensure that both parts engage & can be started easily using just the fingers. I was taken aside & shown this technique during my fitter's training in the 60"s after buggering up a few threads. Works every time. I've never cross threaded anything since. Cheers
Peter TD 5801
P Hehir

Not sure where I learned that technique Peter, but I have been applying it for many years. Thanks for sharing that again. Cheers - Dave
D W DuBois

Don't mean to hijack this thread but I'm trying to contact Dave DuBois. Would you kindly e-mail me as I have a question about a fuel pump rebuild. Thanks,
Lou
stallerl@socal.rr.com
L Staller

Yep, I do the same thing, Peter ... my dad taught me over 45 years ago... turn the screw backwards while applying light pressure and listen (or feel) for the 'click' where the threads have engaged, then reverse direction and it will thread properly every time.
Kevin McLemore

It's useful to have sets of taps and dies to clean up the threads on any fastners you are going to reuse. You need only a few to cover the bulk of the thread sizes. The Hotchkiss ones on the engine are a problem though but I suspect they are available. I have just had to remove the sump and timing chain cover to fit a 35mm lip seal rather than the 36mm one supplied by a MG parts company. The threads were all clogged up with Wellseal (superb stuff) and the slots in the sump bolts with paint. I soaked them in hot caustic soda for about half an hour and they came out like new. Use a stainless pan for the caustic certainly not an alluminium one.



Jan T
J Targosz

I have used this method since my apprenticeship days in the 1950's. As you say Peter works every time and I subconsciously do it as matter of course.

John...Sydney
John Walton

I will typically use a thread restorer/chaser/file rather than a tap and die. They are designed to clean and straighten the threads rather than cut them. For most folks and operations the distinction doesn't matter much, but a tap will more easily damage existing threads if it goes catawampus, and it will tend to cut material off the thread that you may not want to cut.

The thread restorers are easier to use, IMHO, because you can get a standard wrench on them rather than dealing with a two-handed tap or die wrench. Again, not a huge deal for most folks, I just find them more convenient.
David Littlefield

It's a great procedure if you have sorted out your fasteners. Between our Whitworth world, coarse and fine metric, coarse and fine SAE and BA fasteners, the threads can be ALMOST the same. Bud
Bud Krueger

David L. where can one get thread chasers for Whitworth, BSF, Nuffields Mad metric and BA fasteners. I always cringe when trying to straighten a thread using a standard tap & die. What I had done is to bead blast a set of taps to take the edge off of them, which helps a bit, but is still not fully correct (particularly when trying to repair the threads in the aluminum fuel pump bodies). Cheers - Dave
D W DuBois

Thanks Peter. I don't have your training but I've always instinctively used that "reverse turn until it mates" method without even thinking about it. From the other posts I suspect that my cross-threading destruction of bolts and holes is more from reusing unrepaired damaged goods than from technique (except for the part about "If any resistance is felt, stop." My impatience sometimes overcomes my better sense in that regard. Jud
J K Chapin

DW--

You're SOL for chasers for Whitworth, BSF, and BA, as far as I know. Metric are available as it is the head not the thread that is "mad." :)
David Littlefield

This thread was discussed between 28/10/2014 and 29/10/2014

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