how to deal with "staked" screws

[JohnD1956]

I've heard the term before and have a mental picture of what this is, but I'm asking if someone would mind sharing the proper way to work with these.

What is Staking, and how is it done?

Is removal as easy as applying more torque to get the screw out?

Or should something be done before removal to extract the screw without damaging the threaded hole?

Can it be recreated with a simple nail punch upon reassembly?

Or are special tools needed?

Thanks for all ideas on this topic.

[Barney Eaton]

Staking a screw (or fastner) is a nice way of saying "damaging the threads"

The purpose is to prevent the fastner from coming out. This was done (in the old days) before Locktite was invented.

In the attached sketch, I show a bolt going into a plate and with a punch or chisle the threads are damaged at the junction of the fastner and mating part (could be plate, part, or nut) Sometimes there are more than one "stake".

Assuming you have decent access, you need to cut off the excess threads and ideally drill a center hole in the fastner, enlarge the hole until it removes the stake. If you have a Dremel tool, you can also grind away the damaged area.

If there is a nut staked to the fastner, you can cut away the nut or split it.

It get complicated if you need to save the fastner, careful drilling or grinding away the damaged threads may be your only solution.

[JohnD1956]

Thanks Barney. I imagine careful drilling to remove the damaged thread is rather difficult when trying to remove throttle plates from the base of a carb. I think I'll just leave that alone when I open up my 56's carb.

[carbking]

In the case of carburetor throttle plate retaining screws, many older carburetor manufacturers would use a screw with a pilot hole in the threaded end. Once the screw was tightened, a tool would be used to "spread" the edges of the pilot hole such that the screw would not back out and end up somewhere in the internals of the engine.

One such device we acquired from Stromberg was a large set of pliers with a hardened steel point welded to one of the jaws. The jaws of the pliers were sufficiently long to be able to crimp the edge of the pilot hole.

One can remove the "staking" by careful application of a Dremel tool with a burr to grind out the edge of the thread; or one can do the same with the application of a flat file.

Even though we have the tool and the special screws, we no longer stake throttle plate screws. The Carter factory school instructor taught me to use a drop of blue Loctite on each throttle plate and choke plate screw.

Obviously, if you remove the screws, you will wish to replace them with new screws. Several different sizes were used. In recent history:

Carter used 3 x 48 for most choke, and either 4 x 40 or 6 x 32 for most throttle.

Holley used mostly 6 x 32.

Rochester used 3 x 48 and 6 x 32.

Stromberg used 6 x 32.

Zenith used 4 x 40, 5 x 40, 6 x 32, and 6 x 40.

Some of these sizes may be difficult to find locally, but all are available mail order.

Jon.

[JohnD1956]

Jon, are you saying here " One can remove the "staking" by careful application of a Dremel tool with a burr to grind out the edge of the thread" that the thread should just be ground away?

[carbking]

Jon, are you saying here " One can remove the "staking" by careful application of a Dremel tool with a burr to grind out the edge of the thread" that the thread should just be ground away?

I think so:D

More precisely, if one will use the Dremel or a file and remove ALL of the screw that protrudes on the side of the shaft opposite the screw head, then the screw will GENERALLY come out without breaking.

Jon.

[JohnD1956]

Makes sense. Thanks for the help Jon.

[Guest Rob McDonald]

Oddly, I've never knowingly run across a staked screw in a car, although I have heard of specifying this for locking fasteners on structural members in buildings. The answers provided here sound very good but we should probably back up to Johndee's original question, "Is removal as easy as applying more torque to get the screw out?"

I think, no, that's likely going to result in a broken bolt and all the extraction hassle that results from that. It's best to consider if a fastener has had its threads intentionally fouled, before reaching for that 2 ft snipe or cranking up the torque on your air wrench.

Other than on carbs, where else was screw staking typically done by car makers?

[Bill Stoneberg]

I speak from experience.. If you try to remove a staked screw in your carb It will break and then you will need to call Jon and get a new throttle shaft.

More torque does not do it. It only makes it break quicker.