I'm Trying to figure a plan of attack on threading some small parts 3/4-10. It's a laser cut stop , for heighth adjustment on a machinery leg, it has to live with 3/4 allthread, also stainless.
I have the concern already mentioned, stainless on stainless is not your friend. It doesn't "have to" be a bad thing, but I've found working with modern diesel engines (and their aftertreatment systems), you can take some increadibly gaull prone combinations and make them disassemblable with a nickel basaed anti-sieze. Just food for thought. Or if you can identify both materials, it may be that it's fine. Just an option if you need to take a cautious approach.
It is .375 thick, and the thru hole is averaging .665. Hand tapping is my only option at this time.
That's not a lot of threads. How much force is going to be against this stop? If it's low, no big deal. If it's high... More thread engagement is gonna be better. Not a fun proposition is most stainless that I've run into.
I'm curious on your opinion of hole diameter, and tap style, also whether to start from the piercing side or not.
You've got an advantage in that the hole isn't that deep. I think that takes a lot of pressure off on the "type" of tap you choose. Personally, if I were doing this, at 3/8 of an inch thick, you're not going to have a real good chamfer to lead you into the hole, I'd probably spring for a taper just to get it going. The trade off is it's gonna be a lot more turning of said tap by the time you're through. I'd also throw in that in difficult materials, I've come to appreciate the value of getting a single, NEW tap that's coated specifically for the application. They make good inventory to see if it's "close enough" in less difficult materials, versus seeing if your existing ones are "close enough" in a more difficult material. I'm also a big fan of machine taps for hand tapping. Gun taps if you can. (Probably that's going to limit you to a plug tap, but that might be fine. Depending on your access to the hole, I might be a little over cautious about calling for the taper tap.).
Here's a couple of links that make handy charts. The first one is not big enough for this thread, but it's AWESOME to keep with your taps, when you're trying to decide if your drill index is close enough or you need a new drill for "normal" holes. It's also awesome when you have an existing hole, to work back into what you might be able to thread into it. The second two are the same information, less convenient, but fit the hole and threads you're working with.
theoreticalmachinist.com
Drill Size Conversion Chart on DrillsandCutters.com.
drillsandcutters.com
