Tapping question.

[wvmedic]

Can I use an 8-40 tap to re tap a bushing that was taped using a 8-48 tap?
I know that 8 has a major dia. of 0.164 and that 40 and 48 respectfully indicates the threads per inch, but can one re-cut the the threads to 40 vs 48 threads per inch?

Thanks, Jeff

[marvelshooter]

Short answer - no. If you run an 8-40 tap in a hole that was threaded 8-48 there will be virtually nothing left.

[wvmedic]

Thanks marvelshooter, I wasn't sure.

Jeff

[MBTcustom]

Just curious, why do you want to change thread series?
Also, the only way to do this is to weld the hole shut and retap, or drill and tap it to a much larger thread, glue a threaded plug in place, finish it flush with the original surface, and retap it for the new thread.
Certainly a plug is nothing you want to do most of the places that you find 8-40 threads.

[wvmedic]

Tim, I received a part that was cross threaded that I paid in the ballpark of $75.00 with shipping. This part has what I think is an aluminum bushing that is taped @ 8-48, I was going to chase the threads out and by the part that goes in the bushing.

When the part came in I knew the threads were messed up and being an aluminum bushing with a steel part that screws into that. I figured that I could use a pair of pliers to run it in and kind of cut its own threads. Well it wasn't real hard turning it with the pliers just couldn’t do it with my fingers after screwing it in about a 1/8 of an inch. So when using the pliers I didn't tape up the jaws and I marred the part. I should have just sent it back when I got it, but there was a shipping problem with this vendor in the past. It wasn't there fault, the problem I had with the vendor is that they let my order lay on their shelf without contacting me after they couldn't print a shipping label due to my address not hitting correctly with the USPS. They did have two phone numbers for me but neglected to call me, I called them the first time and was told my order had already shipped and if I didn’t receive it in a week to call back. I called back after a week and was then told oh yeah we couldn’t ship it because of the bad address. So they sent the package to my old address at my request and I received two orders. Me being an honest person I contacted them and returned it on my dime, I was told they would reimburse my shipping which was only half of what they charged me to ship it. After all of that I received the same order a couple weeks after they received that order back, again I called and told them what had happened and shipped it back to them again on my dime for the second time without reimbursement. If that wasn’t enough there prices are high, before I knew better I ordered a part from them that I could have gotten from a major manufacture retail not wholesale with shipping included for less than they sell the item for, and it is the same item from the same manufacture.
So I was going to get the tap and bit so one I will have it on hand and by the same piece from another vendor for less than half the cost to replace it minus the bushing.

Sorry for the rant and the length, but that is my reason.

Jeff

[wvmedic]

Just to note about the above shipping, two weeks had went by before I called them the first time and was told my parts had already shipped. Even though that was imposable because they couldn't even print a shipping label. I had to go around with the USPS with my new 911 address, still lived in the same place just a new box number and street name. Like I said the address issue wasn't there fault but not even contacting me about is in my opinion a problem.

So after the above and getting a damaged $75.00 part the last order, I would rather not deal with them again. I've bought from them three times and had two bad experiences, not a good track record.

Jeff

[MBTcustom]

Boy that sucks rocks!

[Marvin S]

You could put a heli-coil in it. Or if you need a larger repair use a keen sert or one of the many others.

[MBTcustom]

You could put a heli-coil in it. Or if you need a larger repair use a keen sert or one of the many others.

That's what I was thinking too, but I don't know if they make Heli-coils in that size?

[W.R.Buchanan]

Tim: They make Helicoils in just about every size imagineable from 2-56 up. 8-32 and 8-36 are the normal sizes so 8-40's or 8-48's might be a problem so he will ahve to check.

Check McMaster Carr as a quick source. Then go strait to Heli-Coil.

A helicoil kit which you need to install them is about $32 right now.

I have 1000 10-32's sitting in front of me right now. Going to have a real ball installing them.

Randy

[Marvin S]

If you cant find that pitch then make your own solid body type insert and lock tite it in.

[MBTcustom]

Tim: They make Helicoils in just about every size imagineable from 2-56 up. 8-32 and 8-36 are the normal sizes so 8-40's or 8-48's might be a problem so he will ahve to check.

Check McMaster Carr as a quick source. Then go strait to Heli-Coil.

A helicoil kit which you need to install them is about $32 right now.

I have 1000 10-32's sitting in front of me right now. Going to have a real ball installing them.

Randy

I know they make all of the standard sizes, but I have never seen specialty sizes. That's not to say they don't exist, just that I have never seen them.
The special tools are a real help, but you can make installation tools easily enough in a pinch.

[I'll Make Mine]

If you can't get a helicoil in the correct thread, I'd suggest drilling the hole oversize and installing a sleeve with metal-filled epoxy (like JB Weld), then tap the sleeve to the correct thread. For a #8-48 original, you'd want the sleeve ID to be about .136 (8-36 and 8-32 both use a #29 drill at .137 for 50% thread), and the OD large enough that the sleeve isn't too thin (plus enough to allow a few thousandths all around for the epoxy). BTW, an 8-48 tap will cost around $10 plus shipping if you don't already have one, while a #29 drill is likely to run under a dollar (but you may have to buy a dozen to get one). For the sleeve, you're on your own; 1/8 K&S tubing is too small, but the next size (5/32) is too big -- maybe you can get some 1/8 brass, anneal, and stretch it over a mandrel for the required length?

[wvmedic]

Thanks for all of the suggestions everyone. I have another part I can use for the bushing, I'm going to drill and tap it.

The problem with that is, I'm limited to an electric drill. I let my drill press go a few months ago because I never used it. If I can't borrow one I just have to go slow and be careful with the drill.

Jeff

[W.R.Buchanan]

Tim: Why don't you come out for the weekend and help me install some of the 1000 I have to do in the next few days. Or maybe you can drill and tap a few hundred of the holes for me?

I can make you a world class expert on helicoils in 2 days. Practice makes perfect,and Iv'e got plenty of practice waiting for you.

One part needs 12 HC's in it and the other needs 20 in it, there is 32 of each part.

I would even feed you!

Randy

[MBTcustom]

Tim: Why don't you come out for the weekend and help me install some of the 1000 I have to do in the next few days. Or maybe you can drill and tap a few hundred of the holes for me?

I can make you a world class expert on helicoils in 2 days. Practice makes perfect,and Iv'e got plenty of practice waiting for you.

One part needs 12 HC's in it and the other needs 20 in it, there is 32 of each part.

I would even feed you!

Randy

Sounds like my regular day job. Ive got enough practice as it is, but thanks for offering.
Sounds like a royal turd of a job. I much prefer threaded inserts to helicoils from a design standpoint (even though they are an even bigger PITA), but some engineers just can't quite grasp the reasoning. Oh well....

[W.R.Buchanan]

These idiots from Raytheon "Specified" Tangless helicoil inserts. The tool to insert them was $238 from Mcmaster Carr, and the inserts aren't cheap either.

I tried a few on my scrap part and they are about a 50/50 shot of going in. Since I am not completely stupid these parts are getting regular inserts and since nobody could tell the difference after the things are in the hole anyway,,, TFB!

These guys have NO PRACTICAL EXPERIENCE whatsoever and they just sit in their offices and look thru websites and find something and think, Oh that would be cool, lets use those. Only problem is "they" aren't ever going to use "those," I am!

I however am not about to scrap any $125 parts for some idiots ego. So we'll do it my way!

You can make anything work in your head, The real world is a harsher environment.

Also you can design anything you want, especially if someone else has to make it for you.

The liberal mind never looks past it's goals to consider the consequences of it's actions.

I make this ship up as I go, and I really like the last one?

Randy

[MBTcustom]

Hmm, indeed so.
Now, I have used many many helicoil inserts, and I'll tell you a trick, that has saved my but soooo many times when dealing with the federal governament: Install with red locktight and follow with a tap!
Ha HA! They wonder how I do it!

[smokeywolf]

8-40 is "National Special" and is not to uncommon. It is the next pitch up from National Fine: 8-36.
Both Weaver and Remington use this thread in various places.

smokeywolf

[MBTcustom]

Well, I have been searching the web looking for some place that sells 8-40 heli-coil inserts, and I am coming up dry. I have never heard of such a critter, and that usually means its not too common.
If anybody finds where such a thing exists, I would love to hear from you hear or in PM because that would be a possible fix for a stripped out scope thread.