How to remove these countersunk bolts

[Ken Fitzgerald]

I have some experience with screws/bolts, large wrist pins and dissimilar metals.

In this thread there are several recommendations that rate consideration IMO. I would try them in this order (1) I would try the manual impact wrench, (2) try the thin lubrication and the manual impact wrench (3)cautiously drill the head off with a drill smaller than the head but only slightly larger than the threads, stopping when the bit reaches the threaded portion. (4) Heat would be my last choice.

Once when working air traffic control maintenance, I was involved with removing a surface search radar's aluminum reflector that was bound by the effects of electrolysis set up by aluminum attached by a stainless steel pin holding the reflector to a pot metal/iron base. We actually blew the seals out of a number of power hydraulic jacks including a "jaws of life" trying to press the wrist pin out. Finally we put a torch to the hinging "wrist" of the aluminum reflector. I was amazed, utterly amazed how quick and easily that aluminum melted back. Heat will also warp the aluminum. JMHO.

[Roger Feeley]

If you have a dr friend, talk them out of some liquid nitrogen. If you can cool the bolt, it might break loose.

[Alex Zeller]

Can you remove the guard from the rear or is it held in place by fasteners behind the disc? I ask because it's possible that there's nuts on the backside you can't see. If so you'll need to remove the nuts first. I assume that the disc is bolted to a hub that's clamped to a shaft. On some of the larger disc sanders it'll clamp directly to the motor shaft. If you can get to that then it would be possible to remove the hub from the shaft to work on it.

[Tom M King]

The hand impact driver would be my first try. I don't remember it ever failing on fasteners around this size. I've used a number of penetrating lubes, but like these little bottles with the tiny applicator. https://logrite.com/Category/bluecreeper

You can probably find such a manual impact driver at Harbor Freight, Amazon, or any number of places. It great on very small machine screws too.

[mike stenson]

Assuming that I knew these were right hand threads, and that cleaning out the heads and using an impact, penetrating lubes, etc didn't work.. I'd bust out the left handed drill bits. But I possess them and they tend to grab and back out the screw while drilling it out. So if it just backs out, it's an easier win.

[Scott T Smith]

Years ago I used to own an automotive machine shop, and dealt with a lot of stuck fasteners.

Lots of good advice so far. Here is what I would do, in order (and credit to others who have already posted).

1 - Understand that removing the bolts with a driver is much more desirable than drilling them out.

First option is to use the manual impact, hitting it with a hammer to alternatively tighten and then loosen the bolt. Do this several times. It helps to keep the impact pre-loaded in the desired direction by twisting it with your hand while striking it with the sledge hammer.

If the manual impact doesn't work, There is a strong possibility that they are locked in place via Loctite. Most Loctite requires heating to 500F temp in order to release. To do so properly, you want to heat the housing that the bolts thread into, instead of the bolt. If you can apply heat to the mandrel surrounding the thread, but not directly to the bolt thread itself, this is the best approach. The objective is to expand the size of the hole around the bolt, thus loosening it, and at the same time release the loctite.

After heating the mandrel, use a cordless impact driver to remove the bolt. It may be necessary to alternate between tightening and loosening a few times.

You need to be quick in terms of applying the impact after pulling the heat away from the mandrel, as the heat will migrate into the bolt and soften it. This is not good, as you can twist the bolt off if it gets too hot.

If this method doesn't work, then option three is to heat the head and tail end threads of the bolt cherry hot, and then let it fully cool. The objective is for the heat to cause the bolt threads to expand - compressing any corrosion, oxidation, etc that are stuck in the threads. After cooling down, the threads should shrink, leaving the oxidation compressed and releasing it's hold on the bolt.

If none of these methods work, then next I would try a set of left hand twist drills. Size them one size smaller than the inside diameter of the threads. What you want to avoid is drilling into the threads on the mandrel, but only leave a thin sliver of the old bolt in place that you can remove via a punch by deforming it. Often times the drill bits will bite into the threads and back the bolt out, which is why you want to use left twist drills.

Some of the best release agents that I have used are Blue Creeper (formerly Rust Reaper), Kroil, PB Blaster and Break free.

Best of success to you.

[Wes Grass]

I forgot about the welding a nut on trick. But I'm mainly a machinist, so I think 'Mill' instead of 'MIG'.

I've also had some luck with smallish screws, #6/8 scope mounts, by using a flat end punch on the head and giving them a good whack with a hammer. I think it compresses the material under the head a bit relieving some of the load on the thread. Helps even with Loctite on them. But you really don't want to be doing that with this in place on the bearings. Just a future reference sort of thing. Unless this has a removeable flange as noted above.

[Doug Dawson]

I cannot shift these countersunk bolts, either by hand or with an impact driver.

They hold a 12" sanding disc, by the way.

Attachment 458369

Any advice on how to free them?
They take a 5/32th hex bit.

Thanks, Mark

The problem with a manual impact driver (Lisle makes a good one, available at a well-stocked auto parts store,) is that it may not have a 5/32” hex driver attachment. I would suggest a 5/32” hex bit chucked in a long enough breaker bar (18+” ought to do it.) Apply pressure, proceed slowly, hear the squealing, and smile. You may need an assistant to apply reverse pressure to the wheel itself.

Alternatively, chucking the bit in a real impact wrench might suffice, again perhaps applying some inwards pressure so the bit doesn’t cam out (with a good bit and a clean hole it shouldn’t.)

[Adam Herman]

manual impact tools are amazing.
i would also apply some heat/ pb blaster

sometimes I have luck heating it up good then cooling it quickly with the pb blaster a few times. I have a set of good allen head sockets in 1/2 in drive if I want to get serious.

good luck.

[Alex Zeller]

The welding a nut trick works better on larger fasteners. Being flat headed you can't get too close to the edge of the head. If you use a smaller nut the hole fills in pretty quickly, sometimes before getting a good bit on the fastener.

[mike stenson]

You can also hammer in a slightly bigger hex. Normally, since for me it's stripped allens on bikes I go for an imperial. You'd want a metric in this case. But, that's if the head socket was stripping. That doesn't seem to be the case?

[Mark Gibney]

Well, the bolts are now free. Before I got to my shop this morning my metalworker neighbor came in a freed them.
He won't tell me how, just to bug me, but I'm guessing he used his handheld impact tool, the one Ken and others suggested trying.
Going by all the good advice on the thread I'm guessing this is a problem we all come up against and have dealt with.
Thanks again for the good advice.

SandingDisc2.jpeg

[Adam Herman]

Well, the bolts are now free. Before I got to my shop this morning my metalworker neighbor came in a freed them.
He won't tell me how, just to bug me, but I'm guessing he used his handheld impact tool, the one Ken and others suggested trying.
Going by all the good advice on the thread I'm guessing this is a problem we all come up against and have dealt with.
Thanks again for the good advice.

SandingDisc2.jpeg

its like the stuck bolt fairy visited your shop! what luck!

im sure we would all like to know your fairies method.

[Tom Bender]

Here's where you test your neighbor's temperament, introduce him as the stuck bolt fairy