Basic Tap and Die Question

A-Jay

A-Jay

Senior Member
I screwed up the end of the bolt on on of the rear crome/stainless bumper brackets, so I borrowed a tap and tie set. The first thing I did was take a tap to the nut to find the size so I could later use the correct size Die to repair the bolt. My stupid question is if the tap I used for the nut was 7/16 - 14 should the Die I would use to clean up the bolt be the size size. It won't start on the bolt and looks way to small on the back end. I know the die has a side to start with. Could someone tell me what is the correct size and thread for a bumper bolt. 30 coupe if that would Matter ??? Thanks for you reply's.
 
Hi Jay;

I am not quite sure which "bracket you are talking about but, if you are talking about the bumper clamps. these I believe are 1/2-20 (fine Thread). A 7/16 -14 tap may sort of fit the nut. You may want to look at everything very carefully.

Let us know what you find outr.

Chris.
 
Last edited:
I have a pair that I bought at a flea market with screwed up threads.They are old repro's,and they turned out to be metric.The guy bought them years ago,then tried to use them with new nuts,then tried to run a die down them to straighten them out,and made them worse.Then he went to the second one and repeated the procedure.I bought them for a dollar and have them on a truck today.I figured it out with a thread pitch guage and ran the correct die down them.
 
Guys thanks, yes I did mean the bumper clamp bolt, I will check the tap set, don't remember seeing that size in there. I did have 1/2-20 die. Hey whats another trip to the Home Depot. Thanks again.
 
Funny you should talk about this...my 1930 [?] bumper clamps are

1~A rough casting. Not forged, not stamped and threaded. Chromed. Not stainless.
2~An odd size. 9/16" bolt shank and a appropriate thick nut.
3~The thread is a fine thread.
4~I measured one inch and counted 18 threads.
5~The dumb thing was I towed the 'A' home with a nylon strap and BLAM! Both of these clamps fractured and off came the bumper turning into my drive way.
6~Now I have to order two replacement bumper clamps.
7~In the mean time I'll bore out the center of the clamp [the broken 9/16" stud] to a 9/16" hole and purchase two flathead steel machine screws to go into a new counter sunk hole through the bumper clamp, through the backing, flat washer, lock washer, and screw into that thick 'special' nut. Screws need to be 2-1/4" long. There going to be tough to find.

8~'Cause they are cast, can't effectively weld them back together...I don't like cast bolts.

When I was in high school, a swim team member left the starting block with such force he blew the block clean off the edge of the pool and slamming it hard against the building wall. Yep each block was held down with two tee screws and a cast fat washer all one piece. The threads sheered off flush with the socket right under the cast fat washer screwed into a threaded pocket at the pools edge. And yes each bolt was a threaded casting.

The result is he lost balance and dived deep into the shallow end [starting end] of the pool and broke his neck. In a wheel chair for the rest of his life.
The next meet all bolts were steel machined screws. Not threaded cast crap.

So my question is were the original clamps threaded cast?
And should I go with costly cast chrome or cheaper stainless steel. Would the stainless still be cast as well?

OK I did something stupid again. skip.

"I think the original clamps were forged.

I have seen what appears to be cast reproductions that I would not want on my car.

Chris."


Thanks. I agree and think forged makes much more sense. Thanx. skip.
 
Last edited:
skip said:
So my question is were the original clamps threaded cast?
And should I go with costly cast chrome or cheaper stainless steel. Would the stainless still be cast as well?

OK I did something stupid again. skip.
Click to expand...

I think the original clamps were forged.

I have seen what appears to be cast reproductions that I would not want on my car.

Chris.
 
I have a set of thread chasers that have a 4 sided thread file (8 different thread profiles) that I've found invaluable for cleaning the threads at the ends of bolts or studs before starting the chase nuts. I've had it for 20 years and was my fathers as far back as I can remember. Maybe you could check out the tool sites someone may carry these files. Clyde
 
Here is a trick for chasing threads on a stud or bolt. Take a proper size nut with good threads, mark it and cut it in two pieces, each piece being a crescent shape. put it together on the stud where the threads are good and clamp lightly with vicegrip pliars. Back it off and you have restored the threads on the stud. Sometimes you have to do it twice and use some oil also.
 
Richard, your home made die is good cheap way to go, if you can cut a nut in half clean.
Skip, you can try JB weld for the bolt that is in the casting, I expoxyed mine with that but screwed up the end of the bolt while clamping it down after applying the expoxy. The JB weld is supposed to be the greatest thing since PBJ (peanut butter and jelly) Also I orderd one new clamp from brattons should get it today. I will let you guys know about the quality of it. There are lots of different ones to choose from.
 
A-Jay, the nut is easy to cut clean enough using a fine tooth hack saw. Also, at least on the larger sizes, you can cut clean through one side and mostly through the other side and spread the nut far enough to go over the stud. I never saw anyone do this and I figured it out at work trying to restore damaged threads on a heat exchanger that had male thread connections.
 
More kludges: There is a decently made tool with an adjustable grip, 2 fingers that go on one side of a bolt and a cutting blade that goes into the threads on the other. Adequate for cutting almost any size that is not too badly damage, can easily start in middle of a bolt.
If you can get a die with (preferably) four relief holes, you can put it in a vise with 1/2 sticking out and break it in half with a hammer blow.
Little Giant brand (industrial supply sources) makes split dies that go into a special stock making them adjustable. They can go over the threads to reach middle and then be run several times, tightening more for each pass. They are marked at proper dimension so you don't cut the thing to undersize. Expensive but not prohibitive, an excellent pro grade approach.
Part of your goal is tryiing to push and roll some of the damage back home, not to cut away everything.
 
You must log in or register to reply here.
Back
Top