Shopsmith Forums

In my 10ER, the rear mounting screw that holds the table insert in place was broken off. Instead of repairing the broken screw someone had just drilled and tapped new holes to the left, which allowed the insert to be installed upside down. This works fine for the table saw insert but not so well for the jigsaw insert. I’ve had to repair broken stainless steel bolts frozen in hardened steel Harpoon missile launchers in the past, which is a huge pain, but You generally just need to drill a slightly larger hole, tap it, and install a helicoil insert. I’ve never had to try drilling a steel screw frozen in cast aluminum, and assumed the drill bit would easily slip into the aluminum and ruin the any chance of easy repair. After Russ’s encouragement to attempt repair (rather than drill the jigsaw insert or buy a replacement table on eBay) I decided to tackle that project today.


First I filed the broken screw to create a flat surface to work with, and then carefully center punched it to hopefully keep the drill bit from wandering.
I have an inexpensive Ryobi workbench drill press that I hoped would be precise enough to drill out the screw while avoiding damaging the aluminum threads. The distance from the edge of the ShopSmith table to the broken screw was larger than the Ryobi was deep, so I had to remove the head of the drill press to slip the SS table over the pillar, as seen in the image below.
As you can see, I clamped the SS table to the small Ryobi table using scrap wood to shim and level the table with the broken screw. I used a 3/32” bit to make a small guide hole through the screw. It looked to be well centered, so I moved up to a 1/8” and a 9/64” bit, after which I confirmed that the hole appeared to be well centered in the screw. Since I wanted to clear as much of the steel screw as possible, and a 5/32” bit just fit into a good screw hole, with very little clearance, I needed to make sure the guide hole was perfectly centered to keep from damaging the threads of the hole. Here you can see that I was successful.
After using the 5/32” bit I was then ready to clear the remaining bits of steel screw from the table’s aluminum threads using a 10-24 tap. Taking even greater care than I would when tapping new holes, I stopped frequently to remove the steel bits with a small brush and a scribe. While I may have been overly cautious, I was successful in repairing the table, and can now properly install the table inserts!

Nice work!

Hmmm! Thee did better than the 'ME' who moved the hole initially.

Curious how thee aligned the tap to the original thread lead.

I would have used an 'easy-out'.

I totally agree with Dennis except the adjective s/b outstanding.

Very nice precision work!

"...broken stainless steel bolts frozen in hardened steel Harpoon missile launchers in the past..."

Yeah, I hate it when that happens

JPG wrote: ↑Mon Jul 19, 2021 9:10 am
Curious how thee aligned the tap to the original thread lead.

I would have used an 'easy-out'.

Thank you all for your kind comments. I feel a little lucky that my method worked. I moved very slow and methodical, taking great care to get the first 3/32” hole drilled perfectly centered, and then stepped up to the final 5/32” bit to hopefully only have a little bit of the screw left in the aluminum threads. I was sctually kind of surprised that it worked. When I finished running the last bit through the screw a small piece of the screw bent up where I could pick it out of the threads with a scribe. At that point I was able to carefully start the tap, breaking up the steel and clearing the threads.

This only worked because I was able to get that first hole centered. I certainly considered using a screw extractor, and if I hadn’t been able to drill a perfectly centered hole through the screw I would have gone that route, but I’ve had bad experiences with extracting small bolts frozen by dissimilar corrosion, so I decided to first attempt this method. Snapping off a screw extractor in a situation like this is a terrible feeling I can assure you, and the smaller the extractor is the more likely that will happen, and the harder it is to recover from it. But, because I was working with the Ryobi drill press I wasn’t sure I could have the precision I needed to drill that first hole, so that’s where I feel I was most lucky.

Anyway, I’m extremely happy it worked out; I hate broken screws and bolts.

Marc,

I hate broken screws and bolts too. You did a great job of saving your original table and it appears your confidence on working on these tools is building. Now just remember getting Shopsmith tools can be habit forming. At first I was apprehensive about working on them but now I do like working on them and restoring them. It quickly became my hobby.

edma194 wrote: ↑Mon Jul 19, 2021 9:45 am Very nice precision work!

"...broken stainless steel bolts frozen in hardened steel Harpoon missile launchers in the past..."

Yeah, I hate it when that happens

I worked as a tech rep on Harpoon and Tomahawk in the late 80s to mid-90s and often had to install or oversee the installation of ordinance alterations (which in military lingo was also called ORDALTS), and one of them required upgrading the electronics in an aluminum box attached to the base of the hardened steel launcher. We often had those stainless steel bolts snap off. One time I was doing this alone on the Alameda naval base, which was on the island off of Oakland, California. I think all the mounting bolts snapped off and I had to search all the local hardware stores and marine hardware supply shops for as many special bits as I could find as the bits kept breaking too. I ended up having to find a magnetic base drill press to finish this job, but it was a huge hassle due to the position of the 5”x5” hardened steel frame that was the launcher base.

You can see the electronic switching box in the first photo below, at lower rear of the launcher, it’s mounted at an angle under the training missile tube. The second photo shows the launchers fully loaded. The third photo shows a launched Harpoon that has just left its canister.