Steel Part Seized in Aluminum

[Richard Wasserman]

This just keeps getting more and more interesting. What you say makes sense to me, but I'm at a bit of a loss as to how to proceed. I need to pull the shaft out of the aluminum part, and I don't know how to do that without damaging it. I wish it was as simple as squeezing it in a press, but I need to go the other way.

It sounds like you have either galling (transfer of aluminum to the steel) or corrosion of the aluminum. In either case, you will probably need to exert some longitudinal force while you twist, or you will eventually have a freely rotating but non-removable part. If it is galling, rotating the shaft will eventually create a groove in the aluminum, and when you finally extract the shaft there will be considerable damage to the hole, possibly preventing you from reusing aluminum part.

It is sometimes possible to use a bench vise, C-clamp, or large Vise-Grip pliers to press out a small shaft. An appropriately sized wrench socket, or even a stack of washers, may allow you to support the outer part as you apply force to the shaft. Of course, an arbor press is even better, under the hands of an appropriately skilled craftsman. (You probably want to avoid hydraulic presses, as one would have to proceed with the utmost delicacy, and this is not what those machines were really designed for.)

In any case, I suggest that you give some thought to pushing or pulling shaft straight out; if the problem is galling or a burr due to a setscrew tip, a single groove parallel to the shaft will be less problematic in the long run than an oversized hole would be.

Good luck!

[Richard Wasserman]

I've checked obsessively for setscrews and they have been removed. Good idea though!

I just thought of something... are you sure there isn't still a setscrew holding it? I've seen two setscrews used, one to lock a piece and a second to lock the setscrew. One on top of the other.

[gustavus]

Ultrasonic cleaner will loosen those parts.

[Ivan J. Eberle]

I'm guessing it's galled and needs pressed out. You may not incur as much damage doing that as endlessly rocking back and forth if you've got galling (essentially mechanically transferred metal--the aluminum-- onto the steel shaft). At least you're not needing to seal it hydraulically when it goes back together. If the aluminum is badly scored or corroded and the piece is big enough it may be possible to have a machine shop ream and/or hone it oversize for pressing in a brass or bronze bushing. I had a Norma and expect that there's enough aluminum in that piece that this would be the worst case.

[Harold_4074]

Ah. I had overlooked the post with the photo.

It appears that you have a steel shaft (with the pinion on the end inside the housing) which runs in an eccentric carrier, thereby allowing you to adjust the engagement depth of the pinion with the rack. From the discussion to date, it sounds like the steel shaft is seized in the carrier, but your statement that you need to pull it out rather than push it suggests that it is the carrier which is stuck in the housing. It looks very much like the carrier is aluminum, and aluminum on aluminum is one of the worst combinations for galling.

If the the steel shaft (with the drive pinion) turns freely, and it is the carrier which is stuck, you might be able to use the collet threads (the ones which allow you to squeeze down the carrier onto the shaft) to pull the carrier out of the housing. Any appropriate spacer will do, and if the bearing surface on the carrier is not sufficiently parallel to the back of whatever you screw onto the threads you may be able to heavily wax the housing and then use something like J-B Weld to create a (removable!) seating surface. If you are lucky, the designer was smart enough to use something other than aluminum for the female threads, but in any event you should use a good anti-seize on them before trying this.

Since the carrier doesn't rotate in the housing except for adjustment, I really suspect that it has either a burr from the tip of the setscrew or a very short primary setscrew still hiding at the bottom of the hole. In either case, trying to force penetrating oil through the setscrew hole and out along the shaft would be revealing.

In the worst case, you will likely either have a machinist provide you with a pull-type collet so that you can use a slide hammer to yank the assembly apart, or he will drill a hole through the opposite side of the housing, in line with the shaft, to permit it to be punched out. Because the eccentric controls the rack and pinion engagement, you really don't want any play there, and continuing to work the parts around is very likely to create some

[E. von Hoegh]

Ultrasonic cleaner will loosen those parts.

Read the thread.

[gustavus]

Read the thread.

When aluminum and iron come into contact, electrolysis takes place a white oxide powder is formed. An ultrasonic cleaner would have worked the oxides out freeing the parts.

By soaking the parts there is the possibility of the aluminum oxide expanding enough the break or crack the aluminum part.

When dissimilar metals are in contact with one another in the presence of an electrolyte, galvanic action occurs, resulting in the deterioration of the metal with the lower galvanic number. The electrolyte may be rain water running from one surface to another, or moisture from the air containing enough acid to cause it to act as an electrolyte.

[E. von Hoegh]

I'm guessing it's galled and needs pressed out. You may not incur as much damage doing that as endlessly rocking back and forth if you've got galling (essentially mechanically transferred metal--the aluminum-- onto the steel shaft). At least you're not needing to seal it hydraulically when it goes back together. If the aluminum is badly scored or corroded and the piece is big enough it may be possible to have a machine shop ream and/or hone it oversize for pressing in a brass or bronze bushing. I had a Norma and expect that there's enough aluminum in that piece that this would be the worst case.

It's hard to say for sure about galling. Definitely a possibility, but soaking and thermal cycling won't worsen that. If I could just get it in my hands for 30 seconds, I'd know what was going on.

[E. von Hoegh]

When aluminum and iron come into contact, electrolysis takes place a white oxide powder is formed. An ultrasonic cleaner would have worked the oxides out freeing the parts.

When dissimilar metals are in contact with one another in the presence of an electrolyte, galvanic action occurs, resulting in the deterioration of the metal with the lower galvanic number. The electrolyte may be rain water running from one surface to another, or moisture from the air containing enough acid to cause it to act as an electrolyte.

Read the thread. He's had it in an ultrasonic. More cannot hurt, though, especially now that it's moving a bit.

[gustavus]

Read the thread. He's had it in an ultrasonic. More cannot hurt, though, especially now that it's moving a bit.

You have my humble apologies.