Mast Foot Screw Removal

[trthebees]

WD40 has it's uses, but I rather like Ferrosol for rusty things. The company does have an extension tube for their wax which fits the Ferrosol can, and it may be that if the screw holes have been through-drilled, then it could be wiggled up and spray some inside to try to attack the threads from the inside. It's what I do up chassis sections for stuck bolts into captive nuts. Tap via heavy screwdriver to keep force straight, test tighten, then try undoing.
It will help lube the casting-to-mast joint. It might even free the sheaves anyway.
Good luck with old stainless into Al., but maybe worth try together with vyv-cox suggestions above before more invasive options.

 

[rob2]

I'm not sure where the shorten the mast idea came from, but that would be the last option if the foot won't come out. Bear in mind that the heel plug is likely to go four to six inches into the mast section so it only needs a slight accumulation of corrosion product to hiold it fast. On the other hand, it also means that simply taking the heads off the existing screws with an oversize drill is acceptable, since there is plenty of space to drill and tap new fasteners for reassembly and the hioles will not significantly weaken the assembly. Indeed one wonders why so many screws were fitted in the first place since their only function is to stop the plug falling out - a function which becomes redundant once a little salt water has seized it into place!

I'd still strongly suggest that you remove the fastenings (even if that means just drilling the heads off) and fit a slide hammer -easily improvised -to pull the plug out whilst pouring copious amount of boiling water over the joint. Only if that all fails should you go to plan B and saw the bottom off the mast extrusion.

I don't know how your mast is stepped. If it is deck mounted on a step then you would need to add a block to replicate the original length and designed to offer secure location. In a tabernacle, a mast foot plug isn't even necessary, although some use one with wedges beneath, so again a block would need to be added. Probably easier to add the missing length with a keel stepped mast as location is subject to smaller forces.

Rob.

 

[macd]

If the OP does succeed in removing the fasteners by whatever means, I'd urge him to fit their replacements into thread inserts (Recoil, Helicoil, etc). The inserts are themselves stainless and thus confine any dissimilar metal corrosion to the area between the insert and the mother metal, rather than between thread and fastener. If the threads are damaged by removal of the existing fasteners, re-threading will be required, anyway.

Selden, to name but one, routinely use such inserts on major mast fasteners for the reason stated (plus, they're stronger), although they neglect to do so with many smaller fasteners. Recoil kits aren't expensive and are simple enough to use.

 

[ghostlymoron]

I think it's unlikely that you'll manage to extract the screws so I would spend your time fishing. If the seized blocks are in sheaves (not sure of terminology), you could remove them and work the blocks to and fro with some penetrating oil - it always works in the end IME. If you have to remove the screws you'll have to drill them out and replace with larger. The screws strength in torsion is bound to be less than corrosion welding force holding them in.

 

[macd]

If you have to remove the screws you'll have to drill them out and replace with larger.

If there's sufficient metal left, and there usually is, thread inserts are the better choice for the reasons I stated.

 

[Seajet]

If it's still available ' Plus Gas ' was the best penetrating oil of my day; it always bemuses me when Ed' from ' Wheeler Dealers ' - obviously a great mechanic - waves WD40 around, I presume there's a financial incentive.

If mixing stainless & alloy, don't forget Duralac anti corrosion paste inbetween, available from any decent chandlery.