Sludge trap plugs

[Slymo]

Stripping down this Super Rocket engine and attempting to remove the sludge trap plugs. First the previous person has punched four deep points at the side of the plug. No way it’s shifting with a screw driver ground 5/8 hex bar clamped in the vise. Next drill a 10mm hole and try my biggest easyout (nice quality Sutton one). No joy I can tell it’s simply too tight and any further weight and I’ll bust the easy out. So off to a mate with a bigger drill press and I drill the plug out so that I can see the spiral thread. Seems to be 11tpi 7/8”? Weirdly though I still can’t pick the threads clean it seems the last remnants of the plug is cold welded in there. So at the moment I’m faced with the very real possibility that I’ll have to tap it out to the next size up. Anyone else had a similar situation and have a solution for me?

[muskrat]

G'day Slymo.
Did you drill the pop marks with a 1/8" drill first? I had one that tight I had to weld a nut on it. I think the heat from the weld helped but it still took great effort to get it out. Drilling and easyout would be my very last resort. Drilling out completely is risky but you might be able to run a rap in to clean out the old thread. I've never heard of oversize screws but would be easy enough to make.
Cheers

[beezermacc]

I usually drill the old plugs out by increasing drill sizes until about 1 mm. of the plug edge left, then punch the edge from the outside with a pointed punch, breaking the remaining rim of the plug inwards. It looks like you may have gone past this point but, fingers crossed, you may still be able to find the end of the thread and wind it out. Good luck.

[Rex]

This is my preferred method too, if the "weld a nut on" way doesn't work. Took a lot of lapping to get the new plugs home too, so a horrible job all round really.

[duTch]

 

.... Seems to be 11tpi 7/8”? .........

 That's what I had too which my thread charts say is 7/8" BSF, but there seems to be differing opinions on this...

[JulianS]

Confirm thread 7/8 x 11 tpi.

On reassembly use hex plugs for easy of future removal and fix with loctite (as recommended by BSA in the A65 workshop manuals, with punching only if loctite not available) rather than hit your crank with hammer and punch. Loctite also seals the thread from leakage.

[Slymo]

Yes cheers all, did the hitting with a pin puch but the remaining threads seem welded in. I will likely have to gomfor the next nearesr size maybe 15/16ths ormammetric equvalent 25mm perhaps hopfully smaller. Loctite is all I plan to use, the guy before me was a bit of a brute with the spot punch. He'd put four around the drive side oil seal as well. Fortunately those i could cut off with a sharp chisel.

[BSA_54A10]

We just did a bunch of them .
Most came out easy but the first one the DPO had punched the flywheel rather than stake the edge of the threads so hard & deep the first 2 turns were so deformed there was no way it could be moved so it was a drill out then dig out the remains of the plug from the first 2 turns.
Ended up a real mess.
If the PO has staked properly there will be a slight horizontal deformation so the threads are pinned in.
When you replace the plug you center punch from the plug into the drilled holes from the previous plug.
This forces the steel in the plug sideways into the hole , again locking he plug from turning.
Do not go putting another 1/2 dozen divots in the flywheel.

[Slymo]

Ok folks Ive succeeded in the end with only the loss of a few of the crests of the threads on one side. As suggested by Trevor above the crank had been punched rather than the plug. The first two to three threads I had picked out but the last four were a problem. I tried turning a 7/8"s x11 tpi thread on a length of rod and milling some slots to see if I could dislodge further down the hole but no smoke out chimney. I then saw that in a couple of spots the remainder of the plug spanned the threads so I took out the die grinder and some tungsten carbide burrs and dressed it down until I could see the crests below,  I alsomused this to remove the spot punch crushed spots on the top threads. It then picked out ok. I'll make new plugs on the Myford and make them a snug fit with loctite and I believe all should be good. Thanks for the prompt advise one and all.

[jjbsa]

Yes, these things are V awkward to get out, and replacing them satisfactorily isn't much better!  Loctite do a viscous grade that's good for sealing and holding these plugs, Loctite 577, it has good gap-filling properties and won't run out into places you don't want it to.  Most times I seem to find that when you're fitting it, the plug wants to be screwed in too deep, and the viscous Loctite holds it where you put it really hard once it's set.  I have tried pressure testing the oilway, and this stuff has always sealed wwith no leaks.  Get the plug out by first heating the crank to 150C.

I have got plugs out by using a long 3mm end mill in the Bridgeport to make a deep and wide slot in the end of the plug, so a really large 1/2" drive screwdriver socket could be used.  About 150lbs ft seems to be par for the course.
HTH

Jon

[Wayno]

I usually drill the old plugs out by increasing drill sizes until about 1 mm. of the plug edge left, then punch the edge from the outside with a pointed punch, breaking the remaining rim of the plug inwards. It looks like you may have gone past this point but, fingers crossed, you may still be able to find the end of the thread and wind it out. Good luck.

Thanks beezermacc - brilliant tip.  I have just used your method and managed to remove both sludge trap plugs without damaging a single thread.  Good job to as crank totally blocked as usual.