Screw extractor - Pilot hole size and which size extractor to use

[mickyd]

That makes the end mill cheaper!:D Maybe my 'previous' mention of one was in a PM???

I see it now. It was in an email, buried between how Arnold pronounces 'Callyfornya' and telling me to use a Jet Fuel soak.

[a1gutterman]

If you have virgin thread that is accessible from the back side, can you tap from that side. If you can, it would almost quarantee perfect alignment.

If so, I would hog out the intereference, fill with JBWeld and go from there. Taking care NOT to inject JBWeld into the area of the virgin threads Run a screw into it while doing the JBWeld.

If you can center the right sized drill bit, why knot use the right size tap and run it through the virgin threads from the back. The virgin threads should keep the tap lined up correctly and the tap should only cut the old bolt material out. Am I missing something?

[reible]

Once upon a time I had an old tool (not made by shopsmith) with an aluminum casting being held in place by 4 screws though a steel support. I did not have the access you do to get at them so directly but I used several versions of penetrating oils including some now banned products. I give them a spray in the morning before work, again at night and of course an attempt to loosen them. This went on for at least 10 days, it might have been even longer.

A friend stopped over to give me a hand. We clamped the table to a work bench and got out the breaker bar. I guess he was feeling his oats (farm people can understand that) and with some tugging bang first one then the others turned. I couldn't believe it! How ever the happiness was short lived. When we went back to a smaller socket set to take the bolts out they were so easy to turn, mostly because the bolt and ALL the threads came out in one piece. The threads sheared.

I was lucky as it turned out, the remainder of the threads in the holes was in good shape and there was enough of it to screw into with longer cap screws. Of course I added some anti seize compound first.

Since I have not seen these ideas in the thread let me add them. A job shop might not cost to much and they will do what ever it takes to get them out and fixed. Machine shops, auto repair places, hey even motorcycle or other pedal type bike shops.

You can also get thread replacement inserts if you can manage to drill out the holes, they need to be over sized to fit. You can also look at Helicoil systems depending on how bad things are.

Sears also sells a different type of extractor then the type you pictured, a comb drill extractor as an example.

I'm guessing you have already searched the web for tools and methods under stud removal etc.

I know in my tool box I have several different types of these tools and they have come in handy many many times.

Ed

[Ed in Tampa]

Again I don't mean to dishearten you but let me say on my aluminum blade spindles with the steel bolts broken off. I managed to snap three different easy out/ screw extractors. All that did was make it even more difficult to drill out the holes on center.

I took the spindles (2) to a machine shop, they looked them over and told me to go buy some new ones since the price to set up a machine and drill out the studs and do repairs should they be needed would be more than the cost of two new studs.

I live close to Bill Mayo who does these kinds of things and his response was go buy two new spindles.

The problem in my case was moisture that got in around the bolts. I think there was some galvanic action between the steel and aluminum (dis simlar metals) that more or less wielded the bolts into the aluminum.

I'm convinced that nothing could have loosen those bolts/studs.

If I ever have to replace the spindles again, I will drill out the bolts and use through bolts with nuts to affix the blade spindles to the mower deck.

[JPG]

. . .

You can also get thread replacement inserts if you can manage to drill out the holes, they need to be over sized to fit. You can also look at Helicoil systems depending on how bad things are.

. . .
Ed

If he doesn't want to spend $16 on an end mill, he ain't gonna spring for a helicoil tap!:rolleyes: or insertion tool!;)

[Ed in Tampa]

On the front inside picture we can see a lot of unused threads in the casting. Why not simply drill out the remaining studs from the front and use a longer bolt and the remaining threads to accomplish what you want.

On my mower spindles the steel bolts were self tapping screwed into the aluminum spindle housing which wasn't pre threaded. Add years of being wet ( we do have to mow in rain sometimes in Florida) and I'm convinced the studs would not come out with anything short of dynamite.

I'm sure you guys have seen enough snapped screws / bolts in your days but since this post has absolutely NO PICS yet, here's what I'm facing. The views are looking down the length of the extension table.
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front (inside)
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[mickyd]

Once upon a time......

I'm guessing you have already searched the web for tools and methods under stud removal etc.

I came across this type of screw extractor that I wasn't aware of. It's advertised for high torque needs. Obviously it's much sturdier than the spiral fluted version I have. Inexpensive too. ~$3 at McMaster Carr.
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Again I don't mean to dishearten you ......
The problem in my case was moisture that got in around the bolts. I think there was some galvanic action between the steel and aluminum (dis similar metals) that more or less wielded the bolts into the aluminum.
....

Your post isn't viewed as disheartening Ed. That happened already when I snapped the heads off. Your experience is what it is and I'm glad you take the time to share it. This possibly ain't gonna be a slam dunk but I KNOW that one way or another, I will tackle this economically without part replacement.

As an FYI, galvanic action to a degree that one needs to be concern about won't occur between plain carbon steel fasteners and aluminums. These two materials have good galvanic compatibility. If however, the fasteners were stainless steel or zinc plated, concern of galvanic action would exists since both stainless and zinc do NOT have good galvanic compatibility with aluminum. Not knowing your specific materials, can't say whether it was galvanic corrosion or just plain iron rust.

[mickyd]

The thrill of victory is sweet!! I managed to maintain an original threaded hole on the extension table vs having to do a JB Weld repair job.

The first step was to try and correct the offset error that I made when I drilled the original pilot hole. I was able to do that by carefully reaming the hole concentric to the original threaded hole using a dremel tool with a high speed cutter. This cutter is like a square face end mill since it cuts both on the side and end.
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I worked on the hole on the right side of the photo below. The hole on the left with the bolt shown in the backside still has the snapped screw. The bolt on the backside is there as a stop reminder to protect the vigin thread once I start drilling.

Once I got the right hole concentric, the next step was to drill a thru hole one size smaller than the one recommended for the tap size. I went one size smaller since there were already threads there, although they were covered with the left overs of the fastener material and not fully visible. I started the tap from the backside where the virgin thread was. This helped maintain the original thread position. This was a little slow since I had to turn the tap with an adjustable wrench 1/4 turn at a time. It took a while but it was very controlled.
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End result is I hit the original thread. I guess this would be considered "chasing" the thread as jpg mentioned.
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Only 3 more to go, one more on the extension table, and 2 more on the work table. To make sure I hit the center of the fastener this time, I am using the right angle method to "find the center of a circle" from this post. You can see the scribe lines on the left screw already. I hit it with a center punch already and it looks like it's dead on. I used a corner of metal scale as the right angle then I scribed the lines with a razor blade.

Off to do the others.

[judaspre1982]

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[mickyd]

Persistence pays off Mike. Your efforts remind me off a song from way back. Like to hear it? Here it goes---------- http://www.youtube.com/watch?v=urLa7y50reE -----Dave

Go Ozzie!! (Sounds like Montrose in places, KISS in others).