Head issiues continued

More work on the head.
As the thread on RH exhaust port had been stripped at some stage it was obvious that I needed to do something about it, I could go the usual way with thread inserts but decided instead to make some oversize nuts. As we all know the standard nuts are made from steel castings which when we consider the different expansion rates from the Alloy head to the steel nuts it probably is not such a good choice as the head will tend to expand away from the nuts to begin cycle of looseness and stripping.
Instead I chose Alluminium bronze alloy that has an expansion rate close to the head material and is quite tough.
I ordered a peice of hollow cast alloy bronze 3'' od x 1/2'' id x 4'' long, not cheap is all I will say about that!
First up I cleaned up the port with a 14 TPI thread scraper to remove the debris and make the threads a bit deeper with good results, then onto the lathe I turned up the blank .060'' oversize from standard. ----






Then start cutting the thread, this is a good nerve test seeing how close you can get to the shoulder without crashing the tool !

Here we go trying the fit in the port, still a bit to come off.




After a bit more fettling the thread is a a real neat fit.





While i was on the lathe I gave the front face some contour to mimic the orignals then it was onto the milling machine,





Put the blanks in to the dividing head, The standard nuts have 18 fins if you count the chunky one as two fins, 360 degrees divided by 18 equals 20 degrees, you will note that I have the chuck set at an angle, this is to copy the taper of the orignals

Here is where I cheated, instead of cutting the fins in the mill as I didnt have a suitable cutter i put the blanks in a vice and slit them with one of those thin abrasive discs ---



And then tidied them up on the linish belt




Theres still a bit of finishing to do but here I am after six hours in the machine shop!



Regards Fred.

Very nice work, Fred. A little different from the usual approach, but they should make an attractive contrast on the bike.

Ken

exhaust-lock-nuts-t7192.html#p73759

Walridge has the bronze ones for 750 (01-0399) and 850 (01-0388) right around $29CAD ea. They are real nice.

Click to expand...

While not oversize they are certainly seem affordable.

Update:

Genuine unplated bronze type - stay tight for 750
01-0399 $35.90CAN

Note: I don't think the 01-0388 part number is correct. At least it wasn't in the 2010 catalog.

Fabulous Furry Freak Brothers avitar takes me back, waaaaaaaaaaay back...totally cool...

Hi Fred,

Yes, nice work.
Can you tell us a bit more about how you enlarged the threads in the head.
You said you "cleaned up the port with a 14 TPI thread scraper to remove the debris and make the threads a bit deeper with good results"
You scaped an internal thread and increased the ID of the bore?

I can see that you reproduced the one thick lug on the nut, as per the original. I think I would have gone for three heavy lugs. Since you made the nut out of aluminum, I think the thin fins will bend quite easily. I have always found that you can't tighten the nut up with using the one heavy lug.

I know, cheap advice from the peanut stand........

Stephen Hill
Victoria, BC

Stephen Hill said:

Since you made the nut out of aluminum, I think the thin fins will bend quite easily.
Stephen Hill
Victoria, BC

Click to expand...

Aluminum Bronze, not aluminum.

Right, aluminum bronze. But my comments still hold. Look at the bronze nut sold by Walridge in the post above. Three heavy lugs. There is a reason.
Stephen Hill
Victoria, BC

Stephen Hill said:

Right, aluminum bronze. But my comments still hold. Look at the bronze nut sold by Walridge in the post above. Three heavy lugs. There is a reason.
Stephen Hill
Victoria, BC

Click to expand...

Perhaps because those are bronze without the aluminum.

I'm not sure about the roadster pipes, but on my S type, I need those 3 heavy lugs on the Norvil style nolts. Other wise I'd be bending up things like I did on the originals.

Dave
69S

Nice work fredful they look really professional. I see there have been some comments about the thick lug but I think three lugs are beneficial because in the manufacturing process there is no guaranteeing where the nut will end up in relation to the thread position, and so will enable the 'c' spanner to tighten them up wherever they end up.

Are they interchangeable or are they machined individually to suit each side?

And I thought they looked good before the fins were finished, it might be an idea to make the next pair with just plain holes and make a peg spanner to suit, (then send them to me! )

Wonderful metal art but now show us the tool or method to nip up a soft single boss style exhaust ring bolt?

There seems to be some misperceptions on this thread about "soft" metals. The common aluminum bronze alloys are as strong as many steels. The common C630 nickel-aluminum-bronze that is commonly available in bar stock, and is widely used for valve guides, seats, and such, has a yield strength of 53.700 psi/370 MPa and a UTS of 110,000 psi/766 MPa. Those are both higher than for common steel alloys like 1018. I don't know what Norton used for their cast exhaust nuts, but I doubt it was as strong as these bronze nuts.

Just my own humble take on the issue, of course.

Ken

Agreed, properties of bronze is up there with steel. Still, the original steel fins fold like a deck of cards, and the bronze fins won't be much better. Hence the need for the thick lugs. If there was no need, why put even one thick lug, which will get the nut half tightened at best.

I am really hoping to hear more from Fred about how he oversized the threads by hand to accomodate the oversize nuts he made.

One of the exhaust spigots on my 1968 Bonneville is loose, because the aluminum threads in the head rattled out.
The problem is there is insufficient material in a Triumph head to bore oversize and sleeve, as per a Norton.
So the fix is to use slightly oversize spigots. You buy them in about three sizes of oversize. And they are supposed to be "self tapping".
Sounds mickey mouse to me.
My preference is to oversize the original threads, along the lines Fred described, then turn an oversize spigot that is a tight fit.
But how do you do that, without making a custom tap, or chucking the whole head on a faceplate and turn oversized internal threads?

Stephen

lcrken said:

There seems to be some misperceptions on this thread about "soft" metals. The common aluminum bronze alloys are as strong as many steels. The common C630 nickel-aluminum-bronze that is commonly available in bar stock, and is widely used for valve guides, seats, and such, has a yield strength of 53.700 psi/370 MPa and a UTS of 110,000 psi/766 MPa. Those are both higher than for common steel alloys like 1018. I don't know what Norton used for their cast exhaust nuts, but I doubt it was as strong as these bronze nuts.

Just my own humble take on the issue, of course.

Ken

Click to expand...

Right there Ken! Allybronze is really tough :!: three times stronger than aluminuim :?:

hobot said:

Wonderful metal art but now show us the tool or method to nip up a soft single boss style exhaust ring bolt?

Click to expand...

This is the BMW tool, I'm surprised someone doesn't make one for the Norton.

This one is even cooler.

swooshdave said:

hobot said:

Wonderful metal art but now show us the tool or method to nip up a soft single boss style exhaust ring bolt?

Click to expand...

This is the BMW tool, I'm surprised someone doesn't make one for the Norton.

This one is even cooler.

Click to expand...

Might work for the early style similar to Fred's but not the three chunk ones.


would be easy enough to mass produce if there was a demand.

Nice work Fred.

Stephen Hill said:

My preference is to oversize the original threads, along the lines Fred described, then turn an oversize spigot that is a tight fit.
But how do you do that, without making a custom tap, or chucking the whole head on a faceplate and turn oversized internal threads?

Stephen

Click to expand...

I can only speculate Fred used a universal thread file for the internal threads (the internal file is the section on the ends you can use sideways. Not all thread files have this.):






or better yet, someone had the bright idea to join 2 old style internal hand thread files together and come up with one of these:


While you can spend hundreds on thread restorers it gets limited when dealing with internal threads.

Source: http://www.icscuttingtools.com/catalog/page_359A.pdf

To get a proper job you may as well spring for a bottoming tap but they are dedicated in size and cost hundreds.

Nice work Fred and nice photos too.

I always snugged mine up with a pipe wrench when hot and I would rotate the pipe wrench around the nut just nipping it a bit each time. Looking at old exhaust nuts it's easy to see the damage happens when removing the nuts more so then when tightening them (most my fins are bent to the left). The pre 73 style with the round ends (look like the bronze Walridge ones) are the worst shape. The big problem with these is the place you apply the force is not above the threads, it's extended out past the threads and the applied force has to transfer from the fins through the thin collar at their base and then turn the length of thread beyond. The post 73 style nut with the big squared off fins (like Fred's) is better because you can apply the force a little closer to the threaded collar than the smaller rounded style. It's probably good the fins bend because soon after that the collar itself will distort out of round. You have to place your tool as close to the cylinder head as possible in the fins so it's as close as possible to the threads and you have to rotate your wrench often so all the force isn't always being exerted in one area on the axis you're pulling your wrench, causing the nut to go out of round. A chain wrench would probably work ok for this too as long as you rotate it also.

Someone's suggestion above about just keeping the holes and using a peg spanner would probably be very functional for directing the force right to the threads.

The answer ot enlargening the threads is so simple you might not believe it.
Dig out an old tap of the appropriate tpi and grind it back short enough that the tapered end is removed. If you happen to have a bottoming tap in the correct tpi, it might work for this without grinding back. I used a regular tapered tap.

Position the head on a bench at eye level. If it is still on the bike get your eye down to that level and get comfortable.
Now use the tap like a scraper to deepen the existing threads. Slowly work your way around taking care to keep the tap threads lined up on the old worn threads as you go.

I used this method to deepen the worn out exhaust threads on my 47 Vincent. Luckily,a friend in the club had a nice set of bronze exhuast nuts that were deemed a little too tight for any of his bikes, hence they had been on his shelf for a few years.



I did this repair 4 years and 24,000 miles ago, still holding and fitting nice and tight.

Glen