Posted on 03/12/2017 9:53:29 PM PDT by Windflier
I'm trying to replace a broken shaft in my sheet metal extrusion machine, but I've run into some machine screws that just will not budge.
They're 3/16th, Allen type, steel screws, mounted in an aluminum block. They have a patina of rust on them, and I already broke a new bit trying to bust the first one loose. I sprayed them all with WD-40, and gave it an hour or two to soak in, but still no go.
Anyone know of a better lubricating product, or some trick I can use to get these suckers to turn?
Thanks, Red. I’m going to use a good quality lubricant and the heat method to try and break them loose.
I’ll post a follow-up report with pics once I’m done.
Much appreciated.
A lot of others have recommended Knock'er Loose, but I didn't know it had a freezing agent. That could help a lot. I'll stop at Grainger's and get some tomorrow.
Thank you.
I've probably had a couple dozen people suggest that I use heat anyway, just to expand the aluminum block. I'm going to try that, along with one of the better penetrating oils. If there's any Loctite in there, that ought to break it loose,
Thanks for the great info.
“Someone suggested using a soldering iron to localize the heat...”
Sounds like it might be worth a try - interesting idea.
That thought occured to me right after I snapped the first Allen bit. I stopped into AutoZone to get a replacement, but they only came as part of a full set. I settled for a new set of standard Allen wrenches (which I needed anyway).
I will still look for a high grade replacement bit, as this probably won't be the last time I have to work on my machine.
Man, I wish I had the time to upload and post photos of the work area, so folks knew what I'm dealing with, but I just can't do it til this weekend.
The bolts I'm working on pass through an aluminum block/plate and then screw into a solid aluminum spacer rod, which has a mirror setup on the other side. Between the two blocks/plates, are the roller wheels, mounted to the shaft.
It's the separator rods that the bolts are actually tapped into, not the blocks/plates.
Yes, as I described in my previous reply. Thanks for thinking through this with me.
I have no suggestions to add, but I just wanted to say you’ve proved Free Republic is the go-to place for those needing a couple screws loose!
Thanks for the warning. I'll keep a spray bottle of water handy.
Aye aye, Cap'n. I'll do that.
Not today. I was out on estimates all day, and the crew had the machine out on a job. It's mounted in my work van.
I've got to go pick up a new work van tomorrow, then I have a full week of estimates and office work til Friday night. I'll get my hands back on it this weekend. I'll post a follow-up report with pics once I'm done.
Thanks for your help.
Buncha nuts around here, I tell ya ;-)
Did you ever get the fasteners backed out?
This means that the threads should be less tight when the entire assembly is at an elevated temperature and the screw is cooler by as much as possible.
After soaking the screws with penetrating oil at least overnight, I would then heat the entire assembly as high as the delicate parts will tolerate.
Then I would place a layer of styrofoam or other insulator over the screw, with a hole just the size of the screw head. Put the allen wrench into the screw head. Then spray with a can of freeze spray to cool the screw and the allen wrench as much as possible.
Then turn the allen wrench to remove the screw.
I once worked with a mechanical engineer who created alignment pins in an aluminum block by selecting just the right size stainless steel pins and drilled holes in the aluminum. He cooled the pins with liquid nitrogen and while holding the pin over the hole, he had an assistant drive the pin into the hole with a hammer. He assured me that the pin was NEVER going to come out or change position.
I presume that he sized the pins and the holes so that minimum distortion of the aluminum would take place as the pin warmed to the temperature of the aluminum.
That same engineer, on the same project, created a heating stage designed to operate at 300 degrees C out of a disk of aluminum inserted into a ring of stainless steel.
The idea was to have the increased thermal conductivity of the aluminum assure uniform temperature across the disk while the stainless steel, which has a lower thermal conductivity, would minimize the amount of waste heat needed to maintain temperature.
The alignment pins described above worked flawlessly. The heating stage was a total failure. Not enough room was allowed for the greater expansion of the aluminum under heat. The aluminum disk ended up squeezed by the stainless ring and developed a crown where there was supposed to be a flat surface.
Good luck with your project. Let us know what worked.
I suspected as much. Therefore heating the block/spacer may do you no good. The bolts are threaded into the separater rods. The separater rods are where you want to apply your heat and/or apply your PB Blaster. I would imagine that the bolts pass-through unthreaded holes in the block/spacer. You have great input in the thread above for loosening a "frozen" bolt. You just need to sort through it for your unique circumstance. And be sure to check YouTube for the exact repair on the exact piece of machinery you are working on. You may not be the first guy in this situation. (Maybe there's a repair kit?) Meanwhile keep it soaked in the loosener of your choosing right up till the coming weekend. Don't forget that it's seven years of bad luck if you break the mirror. Always wear safety goggles. Use plenty of snake oil and elbow grease and think before you act.
No, that is the way Allen screws let you AVOID using an EZ out.
For example a 3.5M screw (if that’s what you have): punch the center of the hex, drill with a 1/16 bit just all the way through the screw.
Apply penetrant. Install wrench in *unharmed* hex and turn.
This requires MUCH less skill than using an EZ out.
This allows penetrant to be applied to the top and bottom of the screw.
But if you can protect the other parts (wet rags?) and apply significant heat, that should certainly free these little screws.
Frankly, penetrant and shocks should.
Fun thread, good luck.
Your idea of drilling out the centers of these screws to relieve pressure, is a very good one. I can easily see that working.
I’m going to try the simplest approaches first, then move on to more intense handlings if they don’t work.
I’ll post a follow-up report with pics once I’m done with the job.
Thanks!
Now that's the best advice I've had all day! LOL
I really appreciate your seasoned overview of my dilemma and the solutions to it.
Yep. Kroil.
Next, perhaps try a heating and cooling. Heat to expand the metal. Cool to shrink it. So you probably want to run a cycle to get the base hot and the bolt cold.
If that doesn’t work, chisel and drill.
No, the crew had the work vehicle with the machine on a job today, and I was booked out with estimates.
I'll get another crack at it this weekend while the crew is off, and post a follow-up report with pics once I'm done.
Thanks for asking.
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