Galling of threaded aluminum parts...prevention?

[EricP]

Seems like every other part I disassemble on this car has an issue I have to fix...

This time, and it isn’t the first, I have a threaded aluminum fitting that screws into the aluminum oil tank. When I removed it to inspect, the threads are buggered. Fortunately it wasn’t threaded very far in.

It may have been misthreaded but since this is isn’t the first, I’m thinking it is due to aluminum on aluminum. Is there a way to prevent this? Maybe it was just over torqued but would a thread sealer or something help prevent this?

[Mike B]

I always use PTFE tape on pipe threads. It not only seals the threads but also lubricates them during installation. It should prevent what you're seeing.
The thread sealant pastes are best left for home plumbing projects, IMO.

[DaveW]

I've had good luck with the pipe-thread sealants like Loctite 565 on aluminum, but I agree, as long as you use the Teflon tape properly (no tape anywhere that could wind up inside) it works fine. As Mike B said, lubrication is the key. When you use tape, be careful with the torque - it's very easy to over-torque and wind up cracking the outer part if it's not super strong.

Also see post #5.

[kea]

It was probably over-torqued at some time.
It appears to be a NPT thread, which should always have a sealant on it's threads. I use Hylomar, but any of the other suggestions will do the trick.
As has been stated, watch you don't tighten it too much.

[DaveW]

Seems like every other part I disassemble on this car has an issue I have to fix...

This time, and it isn’t the first, I have a threaded aluminum fitting that screws into the aluminum oil tank. When I removed it to inspect, the threads are buggered. Fortunately it wasn’t threaded very far in.

It may have been misthreaded but since this is isn’t the first, I’m thinking it is due to aluminum on aluminum. Is there a way to prevent this? Maybe it was just over torqued but would a thread sealer or something help prevent this?

I've had similar situations to this - it looks like the female thread was not tapped large enough to allow proper seating of the male tapered pipe thread. That is evidenced by the fact that it only had a few threads engaged. I've had to re-tap stuff like that many times.

[EricP]

Thanks guys!

I have a tap on order and will tape properly when I install...

[S Lathrop]

I use a product called "Copper Slip" for thread protection and as a sealant. It is a Loctite product now days.

[Mike B]

I use a product called "Copper Slip" for thread protection and as a sealant. It is a Loctite product now days.

Maybe Copaslip?
https://www.pegasusautoracing.com/pr...SAAEgKJa_D_BwE

[S Lathrop]

http://www.amazon.com/Permatex-31163...nkCode=df0&hva

[EricP]

www.amazon.com/Permatex-31163-Copper-Anti-Seize-Lubricant/dp/B000HBIDO2/ref=asc_df_B000HBIDO2/?tag=hyprod-20&linkCode=df0&hva

excellent! I have a bottle of that.

Now... just that or WITH Teflon tape? Or is that like wearing a belt with suspenders?

[S Lathrop]

excellent! I have a bottle of that.

Now... just that or WITH Teflon tape? Or is that like wearing a belt with suspenders?

I use the Copper Slip by itself..

[Charles Warner]

Looking at the threads and overall condition of the fitting, I'd have to ask if you were positive the male and female threads were of the same spec. BSP vs NPT.

[Hawke]

Teflon tape is the work of the devil, as are tapered threads. All it does is give good lubrication to the thread, which allow the fitting to be over tightened and ultimately split or damage the housing. If it doesn’t do that, it allows the fitting to easily vibrate out. If you must persist with the tapered thread, use a proper Loctite thread seal, or convert it to a parallel thread with a proper O ring.

[tlracer]

I would agree with Charles Warner - confirm they are both definitely the same thread. Also, if they are BSP, whether you have a taper fitting going into a parallel hole.

[Rick Iverson]

Yep, what I use. Especially for dissimilar metals.

I use a product called "Copper Slip" for thread protection and as a sealant. It is a Loctite product now days.

[BeerBudgetRacing]

Looking at the threads and overall condition of the fitting, I'd have to ask if you were positive the male and female threads were of the same spec. BSP vs NPT.

Hewlands have BSP "pipe" threads - which makes sense

But, a lot of the "not-original" threads are NPT where people added vents, etc.

[rg2]

I'm not a fan of teflon tape for the same reason other folks have mentioned. That is, it can get into things. I have however, used with success liquid/paste teflon by Permatex sealant particularly on things that get removed and reinstalled often like scavenge screens.

[pakracer]

I have found, at least with Hewlands, that they use BSPP which is British Standard Pipe Parallel (BSPP)as opposed to British Standard Pipe Tapered (BSPT). I have researched and found that the BSPP is the same threads per inch but the thread is a 70 degree pitch as opposed to the American thread which 65 degree or vice versa. I'm not sure of the BSPT and American tapered pipe thread have the same difference on the thread pitch, but it is difficult to tell unless you know the origin of the part.

[BeerBudgetRacing]

I have found, at least with Hewlands, that they use BSPP which is British Standard Pipe Parallel (BSPP)as opposed to British Standard Pipe Tapered (BSPT). I have researched and found that the BSPP is the same threads per inch but the thread is a 70 degree pitch as opposed to the American thread which 65 degree or vice versa. I'm not sure of the BSPT and American tapered pipe thread have the same difference on the thread pitch, but it is difficult to tell unless you know the origin of the part.

Surprising but I found a BSPP tap for the LD200 drain plug on Amazon. Cheap too like $20. I had a box that needed some cleaning up and it worked great.

The P threads will have a washer to provide a seal. In places like the gearbox drain the case just isn't thick enough for a tapered plug to do its job.

[mark elder]

BSP vs NPT
55 vs 60 degree
shape of the thread form is different
ONE pitch different per inch between the two types for almost all smaller sizes (ie. 1/8 is 28 vs 27 and 3/8 is 19 vs 18). The catch is 1/2" and 3/4" are the same pitch but of course different thread angle and form. Bigger sizes then have a pitch difference again. This is a minefield....

So one goes into the other for a bit then tightens (but not in a good way).

For any of these fittings, if the male bit only goes in 2-3 turns, then you need to stop and check if you have the threads that match.

It is really important that you know which one you have (and sort of hard to sort out too; well, not really, but a 2 second look and a quick guess is not good enough).

[mark elder]

And for EricP (first post on this) with buggered threads. My guess is it is due to a mismatch of BSP and NPT (someone put the wrong fitting in) and then tightened it enough to damage the threads.
Just my 2 cents worth.

[tlracer]

Yep, what I use. Especially for dissimilar metals.

Duralac is specifically designed for a corrosion inhibitor for dissimilar joints, especially useful on metals like aluminium and magnesium, which are very prone to electrolytic corrosion where they have a steel bolt, etc. in contact.

[924RACR]

After having my oil return line vibrate loose and kill a motor (not to mention oil down half the back straight at Mud-O), I refuse to assemble any automotive plumbing fittings, racecar or street, without a dab of Permatex 54540:
https://www.amazon.com/Permatex-5454.../dp/B000HBGL14

Explicitly states prevents corrosion and galling, as well as vibration loosening etc.

[kea]

I'm pretty sure he is working on his Citation (American made) and on the oil tank not a gearbox, so BSP is not an option seen.

[Jerry Kehoe]

When in doubt regardless of sealer ,tape or paste, a simple safety wire takes care of the problem and gives a simple visual checkpoint. I like the British straight pipe thread with a o ring or stat-o-seal and safety wire. Makes it hard to screw up the threads or crack anything.

[EricP]

I'm pretty sure he is working on his Citation (American made) and on the oil tank not a gearbox, so BSP is not an option seen.

Correct. I appreciate the caution but it is definitely NPT.

[Rick Iverson]

Gents;

My apologies for taking a bit of an off-course excursion here, but timing is everything. I am rebuilding a Cozy front mounted pump, and desire to replace the 45 degree fitting with a straight fitting. Considering the age, best guess what the threads are?

[DaveW]

From the style of fitting, I'd guess NPT.

[tlracer]

Depending on age, I would have thought either BSP or AN, but the only sure-fire way to know is remove it and measure.

TPI, diameter and angle should confirm.

[scorp997]

Rick, being English, I’m gonna bet it is BSP. Do you have any BSP fittings to try? If that is currently an NPT fitting, AN wont fit the same threaded area.

i have another one of these front mounted oil pumps that had the threaded boss broken, probably due to someone tightening an NPT fitting in too tight. You’ve just reminded me that I need to get that welded up so I can sell it!

if you get an o-ring AN adapter (ORB-8AN) it should thread right in. Use a copper crush washer (or Dowty seal) on fitting.

[scorp997]

Just confirmed on my Cosworth pump that all except the scavenge “In” are BSP-08 and the scavenge Is larger (an ORB-10 threads in)

the threaded area is pretty short so you may have to reduce the length of the BSP fittings as to not bottom out.

[Charles Warner]

All of this is really "neat." However, to the matter at hand, the fitting shown by the OP is buggered beyond use. It has been abused over the years. (I'm not saying WHO abused it, just that it has been abused and is now scrap.) Look at the first 3 threads. Flattened, with no real evidence of galling.

I have seen parts from both sides of the pond that were NPT, BSP, BSPP, and even Whitworth. My (failsafe?) method is to hand tighten the fittings, without thread seal, teflon whatever, etc. If there is resistance before three full rotations then you have an issue. Then it's off to the spare parts bin to see what fittings actually fit.

A full set of taps and dies for all eventualities is a great thing to have. Not cheap, mind you, but a great thing to have. Thread chasers in the appropriate sizes are also a necessity.

[mark elder]

If I was both EricP and Rick, I would be machining/tapping the female part to be a parallel threaded hole of some sort and then inserting the same parallel male threaded part with a decent washer to seal it (and also use a liquid sealant). There are clever washers with O rings build in that often come with the male fittings. You can buy a whole set of these taps for $100. I recently converted an oil pump from Ricks 45 degree style fitting to straight (I think it was 5/8 JIC to -12). Hydraulic shops typically use JIC fittings; read up on them. JIC are designed for high pressure. Just what we want.

Tapered fitting are a cheap and dirty way of getting a seal. But they risk cracking if overtightened. For us, these fittings are all on oil lines so are critical. Cracks are bad and expensive. So are leaks. Parallel has a lot more thread-to-thread contact and gets a proper washer.

Just convert them to parallel once and for all. Job done. How hard is it to drill and tap a hole?

[Rick Iverson]

Gents;

Straight AN male to BSP male. Phenix Industries, PN B6101214-4, -10 to 1/2 x 14 BSP, Blue. About $4.50 each with crush washer. These babies are quite nicely made, and you can’t beat the price.

Gents;

My apologies for taking a bit of an off-course excursion here, but timing is everything. I am rebuilding a Cozy front mounted pump, and desire to replace the 45 degree fitting with a straight fitting. Considering the age, best guess what the threads are?

[JHerscher]

A full set of taps and dies for all eventualities is a great thing to have. Not cheap, mind you, but a great thing to have. Thread chasers in the appropriate sizes are also a necessity.

Now wouldn’t those make great Religious Holiday, Birthday, Anniversary, etc. gifts?

if only I can remember that next December!

[BeerBudgetRacing]

Now wouldn’t those make great Religious Holiday, Birthday, Anniversary, etc. gifts?

if only I can remember that next December!

My birthday is in July - I can remind you...

[mark elder]

Rick; nice work. And so cheap.

Be nice to see what EricP comes up with...