I have a stripped 1/2" nc threaded hole-no bottom, can I drill out and tap to 9/16 nc, would
I be better off going to nf for new material, would all the old treads be cleaned out with nc? Any suggestions?
What is the application? If you need max strength then a Timesert would probably work better. All these thread repair inserts are sold to fit the original thread on the inside, so you would buy a 1/2 X whatever tpi insert. You will need a special drill to enlarge the hole and a specially sized tap to create the outer thread of the insert so most of the kits you buy will include the drill, the tap and a small quantity of your required insert. The good kits also include the installation tool to thread the insert into the new hole, like this one: https://www.amazon.com/TIME-SERT-2-...535936196&sr=8-2&keywords=timesert+kit+1/2-13
If I understand the OP, your tapped (stripped) hole is (was) tapped through. Is that correct?
How thick is the material?
What material is it?
Is the fastener removed and reinstalled regularly or installed and left alone?
Is it a high vibration or cyclic loading application?
Why did the original tapped hole strip?
Those, and others, are all factors in choosing a insert type for thread repair.
Totally recommend Helicoil or other brands of similar devices. you can buy kits in single sizes., or a range of sizes depending on your need, which include special sized drill, tap and set of inserts.
Highly recommended for situations where a thread has stripped out, or where fixture is regularly tightened and loosened. Also useful in soft metals to prevent early failures. I keep a kit of common sizes on hand, but even then occasionally have to buy an odd size to add to the range.
I am not a big fan of the Helicoil product. They have their place, but depending on the application - other options should also be considered. The reasons I'm not keen on Helicoil is you have to buy the specialty tap and insert, they are not real tough (it is easy to damage the Helicoil - usually you can replace it, but if the hole gets damaged again, the options become a bit more difficult). If it is just one hole, you may not want to purchase a kit for that one time. Again, Helicoils have their place, but consider some other options.
Is there room to simply thread in a sleeve? It depends on how much room you have. Play around with larger NC or NF (or even metric) threads to get one that will fit (and you have / can get a tap for). Drill and tap that bolt for your 1/2" thread - then loctite that sleeve in. Can you use a stud? Then make a stepped stud. Can you just oversize the hole and put in a bigger bolt? Can you make a simple straight sleeve and weld it in?
My little lathe uses British Standard fine threads. The two piece apron cover is made of an aluminum casting and one of the screws holding the two pieces of the cover together was stripped. I had the right BSF tap, so I drilled and tapped a 5/16 bolt, cut it to make a thread x thread sleeve, drilled and tapped the casting. The repair is nearly invisible (certainly once assembled), the bolting is all original and the result is stronger than the original. This is a common issue with this particular old English lathe (which is a very nice machine, but has a few oddities - like weird bolting) and most people tap the holes a bit larger to some size that is easier to obtain. My solution took very little extra time, and I did not end up with one bolt different than the others (or changing the bolting for the whole cover).
Not everyone has to be a fan of every product. But I would hate to be without them. Whilst the options that Chipper makes are all quite valid, when you don't have a helicoil available,and I have used them in those situations, but none of them are quicker or easier, so I fail to see the advantage.
Helicoils are indispensable when working with aluminium castings, in fact some products use at the manufacturing stage, and they are specifically designed so that you always end up with the standard bolts. or studs.