Tapping stripped threads

[tjdonahoe]

Buy the best bit you can ..no home owner bits..they are low budget..if they are broke off..drill new holes..and use a good corded drill

[Rich W]

Originally Posted by RFP

The thickness of the material is too thin for helicoil installation.

I'd have to drill out the bracket holes too. They are exactly 5/16". Even paint stops the bolt from going through. (I made progress today, see my later post.)

[RFP]

Originally Posted by richw46

I'd have to drill out the bracket holes too. They are exactly 5/16". Even paint stops the bolt from going through. (I made progress today, see my later post.)

Rich,

I'm not sure what you are saying here. A helicoil needs fairly thck material for installation. The material in the trailer with "stripped out" holes is pretty thin: 0.150" or so including the thickness of the belly pan.

[Rich W]

I did make some headway today. On the right front, forward 2 holes I used a HFT hammer drill that's been in a box on the shelf for a couple of years. With the reverse 5/16" bit I was able to drill past the snags from the old bolt. I used the HFT tap to run threads in each hole. The drilling was off center because the Irwin bit kept skating across the old bolt so the threads are probably weak. When I installed the stabilizer I got the 2 good holes bolted first, then I bolted the other holes. Since the original drilling was off center the holes in the bracket didn't exactly match the newly tapped holes. With bolts in the good holes first, the bolts in the bad holes are tight against the original hole, with some threads added. It's not pretty but it's tight. It seems to hold it very well.

I tried the drill on the left front hole but succeeded only in smoking the WD40. The bit is burned up and not taking a bite. I tried a DeWalt bit with the pilot tip but it just burned up that (pilot) tip. I'll need to get a regular bit like the Irwin and burn that one up to get that last hole opened up.

Anyway, progress. Maybe on a nice fall day I'll bring the Airstream home and work on it here in the street again, hoping the HOA doesn't see me.

[Rich W]

Originally Posted by RFP

Rich,

I'm not sure what you are saying here. A helicoil needs fairly thck material for installation. The material in the trailer with "stripped out" holes is pretty thin: 0.150" or so including the thickness of the belly pan.

For each rear stabilizer there are 5 bolts; 1 amidships and 4 outboard. When the OEM trilobular (Taptite) bolts were removed one broke off but the others came out. But, of the ones that came out, some stripped out the threads from the hole. I replaced those 5/16-18 bolts with regular ones but they just spin, won't tighten. The other bolts in holes with threads I snugged, afraid to tighten them too much.

The BAL stabilizer brackets that hold the "legs" bolt in those holes. The holes in the bracket match up to the self-tapped holes in the belly. If I go with a bolt larger than 5/16" I'll have to drill out those holes to accommodate the larger bolts, and that's thick steel. So right now I've ordered rivnuts and I'll drill out the existing belly holes and put the rivnuts in there, then I can use new 5/16-18 1" bolts to hold the stabilizers.

[Rich W]

Originally Posted by tjdonahoe

Buy the best bit you can ..no home owner bits..they are low budget..if they are broke off..drill new holes..and use a good corded drill

Hi, I've bought DeWalt bits, 3 sets. They get good reviews and are cobalt and titanium. I got the Irwin reverse extractors and bits. They weren't cheap but about the price of the DeWalt bits. It doesn't say what they are made of but Irwin is a good bit. Drill America has some nice bits but those are very large sets and quite expensive

Cobalt bits seem to be the strongest but for this application I need beveled bits and not ones that have the pilot point. The Irwins have done the best job so far but 1 broke and 1 is now too dull to do any good.

I need 1 more 5/16 cobalt bit with the beveled tip and with the HFT hammer drill I might be able to get that last hole drilled out. I need a 27/64 to drill out the holes for the rivnut too. That's just to make the existing hole larger, I don't have to start new holes. (whew)

If you have a recommendation I'm up for that. I'd like to just buy the sizes that I need rather than complete sets.

[ITSNO60]

Originally Posted by richw46

Hi, I've bought DeWalt bits, 3 sets. They get good reviews and are cobalt and titanium. I got the Irwin reverse extractors and bits. They weren't cheap but about the price of the DeWalt bits. It doesn't say what they are made of but Irwin is a good bit. Drill America has some nice bits but those are very large sets and quite expensive

Cobalt bits seem to be the strongest but for this application I need beveled bits and not ones that have the pilot point. The Irwins have done the best job so far but 1 broke and 1 is now too dull to do any good.

I need 1 more 5/16 cobalt bit with the beveled tip and with the HFT hammer drill I might be able to get that last hole drilled out. I need a 27/64 to drill out the holes for the rivnut too. That's just to make the existing hole larger, I don't have to start new holes. (whew)

If you have a recommendation I'm up for that. I'd like to just buy the sizes that I need rather than complete sets.

I'll maintain that a good sharp bit of any brand will do the job if you drill slowly, use a lubricant and don't allow the bit or the work to overheat. A decent cordless drill will give you more control over speed and pressure than a corded one. I always use my Makita 18 volt for slow drilling on vehicle frames. Even the Harbor Freight bits do the job. I have many sets of bits including just the plain black oxide ones which work great and are easy to sharpen. Drill a pilot hole first before moving to the final size. Also the bigger the bit, the slower the speed if you want it to hold up. Speed Kills.

[Rich W]

I've learned a lot about drill bits these past few weeks, mostly how to burn them up and break them. I always use WD40 and go slow when trying to drill out the bolt or go through steel. I stop frequently and check the bit to see if it's getting hot. To get past that burr left on the bolt that was pushed out of the way I needed something stronger than the DeWalt cordless. The HFT 1/2" impact drill did that in about 2 seconds with the same bit I had been using in the cordless. At this point I think I'm going to leave the front stabilizer bolts alone, the stabilizers seem to be pretty solid. For the rear I'm going to get a 27/64" bit and use rivnuts for the bad, threaded holes

I can't seem to find a single reverse bit to replace the one in the Hanson/Irwin extractor kit. Have to buy an entire kit. Bits that have the pilot point are good for going through some metals but drilling out broken bolts isn't one of them. Shorter bits are better because they don't break as easily. Here are the different types of metal used to make bits.

DRILL BIT MATERIALS
High-Speed Steel (HSS) is a popular material good for drilling into soft steels as well as wood and plastic. IT’s an economical solution for most maintenance drilling applications.

Cobalt (HSCO) is considered an upgrade from HSS because it includes 5-8% Cobalt blended into the base material. This is a great option for drilling into harder steel as well as stainless steel grades.

Carbide (Carb) is the hardest and most brittle of the drill bit materials. It’s used mostly for production drilling where a high-quality tool holder and equipment is used. It should not be used in hand drills or even drill presses. These drill bits are designed for the most demanding and hardest materials.

DRILL POINT COATINGS
Black Oxide (surface treatment) Helps reduce friction and increase chip flow. Not for nonferrous materials.

Bright Not real finish, but polished for increased chip flow. For use in plastics, woods and aluminum.

TiN (titanium nitride, gold color) Can be run faster than uncoated drills and increased tool life.

TiCN (titanium carbonitride, blue-gray color) Great for stainless steel, cast iron and aluminum. Harder and more wear-resistant than other coatings.

TiALN (titanium aluminum nitride, violet color) For use in high-alloy carbon steels, nickel-based materials and titanium. Not used for aluminum.

More information here:
https://www.grainger.com/know-how/in...ase%20material.

[Tim A.]

Originally Posted by richw46

I can't seem to find a single reverse bit to replace the one in the Hanson/Irwin extractor kit. Have to buy an entire kit.

You can find singles here: https://www.mcmaster.com/screw-removers/extractors-7/. For those who don't know, McMaster-Carr is a wonderful source for all sorts of tools and hardware.

Tim

[ITSNO60]

Yes shorter is better for hand drilling which is another case for jobber bits. I also have centering bits which are very stout and allow you to start a divot before using the drill bit, they don't flex or walk as much. I use them on my drill presses but never tried one on a hand drill. A good sharp punch is the way to get a center divot when hand drilling. Once a drill starts a hole off center you are pretty much screwed.

[TG Twinkie]

WD40 is a poor lubricant for drilling and tapping. IMHO

[Rich W]

Originally Posted by TG Twinkie

WD40 is a poor lubricant for drilling and tapping. IMHO

It's what was around the workbench. I Googled using WD40 and most sites said it was OK, some said it was great for aluminum. WD40 makes a cutting oil as well. I found 3 in 1 oil was another recommended cutting oil. The bits never got too hot to handle, I went slow and used a spray every 10 seconds or so. Only 1 bolt remains to be drilled out but the bit I used for the other 3 and most of the remaining one is pretty dull now. I'm not sure yet if I'm going to finish that one or not. I may go fishing instead.

[Rich W]

Originally Posted by Tim A.

You can find singles here: https://www.mcmaster.com/screw-removers/extractors-7/. For those who don't know, McMaster-Carr is a wonderful source for all sorts of tools and hardware.

Tim

Thanks, Tim. McMaster wants $15.73 plus tax and shipping for the one 19/64 left turning bit. I paid $34.69 for the Irwin extractor set, which contains 5 extractors and 5 reverse bits. I can get an Irwin single bit 19/64 right turning cobalt bit for $7.60 plus tax, free shipping. A left turning bit would be ideal but this bolt isn't going to unscrew, there's no head but room to continue going to the right and out. I will keep the link in case I need something down the road.