<VV> Head studs

[Mel Herwald]

This started with a 65 RX case that had rusty top head stud threads. These
would be the threads that the nut goes on , i. e. the ones visible when
looking at the case with the studs attached. I had other cases with what
appeared to be studs with good threads in this area. I have a stud removing
tool with the knurled wheel that grips the stud and it also attaches to a ½”
ratchet. So I removed several studs. Some came out fairly easily-others were
a little more difficult. I cleaned the threads with a wire wheel. I then
proceeded to examine the threads on both ends. I examined the outer threads
for rust and the inner threads for any Aluminum. I discarded any studs that
were questionable. I noticed that my 3/8”-16 die would not thread onto the
inner stud end nor could I get a nut going. But the threads looked perfect
even under a magnifying glass.

 

I then removed most of the studs from the case halves. Some came out fairly
easily and others were more difficult. I was pleased that I didn’t see any
signs of aluminum on the studs. I then took a 3/8”-16 tap and ran it thru
the threads in the case halves. The tap felt fine in each hole. I then
squirted brake cleaner on the threads and blew them out. I applied red
loctite to the stud threads and started installing the studs. The first few
went in fine. They seemed to get tighter as they went in and got quite tight
at the end. Then the first real mishap occurred. As I was installing a stud
about half way in it abruptly got very hard to turn—too hard. I started to
back it out and it again was too hard to turn but I took it out and with it
came some aluminum. Since the threads were only damaged half way down I ran
the tap thru and installed a .006” oversize stud. I don’t understand what
happened because the threads on the stud looked perfect. I intend to use a
suitable pipe and some washers and test this stud before assembling.

 

I went to the second case half and the first 2 studs started easily but got
very  very hard. I figured if I tried to remove I’d pull more aluminum and I
barely managed to get them all the way in. The third one was even worse and
in the process of fighting to install it I managed to bend it. As I tried to
straighten it, it snapped of about ¼” above the case and I could not get it
out  with the stud remover ,vise grips, or a pipe wrench. The red loctite
set up This is where I quit. It was not a good day. I’ll get the stud out
with a center drill and a friends milling machine.

 

Now the reason for this post. I have a few questions. Here goes.

 

1)      What class of thread is on the end of the stud? I’m guessing it’s a
class3. What are the specs on these threads?

2)      How would one test the threads on the end of the stud short of a
go/nogo gage for this thread class? They looked perfect.

3)      Should one never use used studs?

4)      Should I have run a tap thru the case holes where the studs attach?
The tap seemed to work fine.

5)      Why did some studs go in well while others were much harder? What
happened to them? Did it have something to do with the way they came out?

6)      Are the threads in the case standard class 2 threads?

 

I don’t want to ever have a repeat of this and would like to understand what
was going on. I’m hoping some of you have been thru this before and can shed
some light on this for me.

Thank you.

 

Mel Herwald