Tap Set Advice Please

Badly damaged threads in Marvel cast iron carb body while trying to remove Old Stuck Float Valve Seat using a drill.

Any advice for a newbie with a tap set, and for finding/making a New Sleeve for the Float Valve Seat piece to bulk it up so that it fits the new hole?

What's the carb for? If you have a # on it I or someone else may have the base you need.

Having done a similar repair, I don't think you will find the tap you need in most sets. I am thinking you will need a bottom tap in order to get threads deep enough to repair the hole and allow the new seat to thread all the way into the housing. You start the thread with a regular taper or plug tap and finish the last 2 or three threads with the bottom tap.

I am aware that you can purchase a set of three taps that have the same thread, one of which is the bottom tap through businesses that supply tooling to machine shops.

I usually get special taps from NAPA. So far they have always been able to help me.
My personal tap set is a Craftsman. I've used the Snap-On set at work and its o.k. (But much more $)

With a drill press and tap drill sizes as needed. Choose a tap size that will allow the seat to be corrected mut not
larger. Position the carb body so the location of the hole you make is perpendicular to the drill. (very critical)
Drill the hole slowly so the hole does not wander. Drill shallowly so as not to get into other passages (or Air) use a
normal tap for that size, but stop short of the full depth of the tapered part. Use an aluminum rod as a plug. Use a
die on it to create the same partial threads. Fit the two together several times as you make the threads deeper on both
pieces. When it seems to thread together at least 2 threads deep, stop. Cut the aluminum rod just above the break
(1/16th") Cut a screw driver slot in the remaining threaded plug. (no deeper than what is exposed) Use teflon tape on
the plug (one rap only) then tighten the plug into the hole. Use a dremel tool with a diamond burr to flatten the plug
to flush and flat. Drill and tap the new plug for the new seat. Jim

It's likely a thread ''FINER" than "NF", likely "NS" or something in that area, and you aren't going to find that tap in an "off the shelf" in a standard tap and die set.

At this point, if you have access at a reasonable price to a well-equipped machine shop, this could probably be dealt with for less than the price of an alternative carb upper casting, if NOT, chalk it up to experience.

Or, check out fleasay, or simlar for similar wcffms

It is too late now but if you heat the brass fitting until the flame shows green then let it cool it will come out real easy.

Without seeing the the amount of damage it is hard to recommend a correct path forward. As Janicholson said a tap isnt going to put metal back in the hole that you removed with a drill bit and the tap you need is likely not going to be in any tap and die set found at a hardware store. In your favor is the fact that the seat does not depend on the threads to seal it to the carb body. That is accomplished by the gasket. If the threads are good enough to pull the gasket tight you are OK. If bungled to the point that the new seat will not thread in you need to measure the major diameter of the thread (which is close enough to the O.D.) and then you need to know the number of threads per inch by using a thread gauge. Look at a tap and die chart and if it is not a USS or SAE thread (likely not) you need to find a machine tooling supplier and they will have odd ball taps. You will need a bottom tap. If you have messed up the hole beyond this then you need to do as advised by Janicohlson, make a bushing and thread it. Some have reported success with JB weld in such repairs in lieu of making a bushing but I have not had much luck with it where it is in contact with todays fuels.