27 replies to this topic

[Guess-Works.com]

Yes, as you'll need the cone compressor to install the new ones...

 

Even though Doug's home made tool is up to the job, in the UK I would suggest buying the tool, over using some of the monkey metal threaded bar which is available over here... or go to an engineering shop and buy some HT steel threaded bar

[Vipernoir]

½" UNF and 14mm are extremely close together.
A '74 is right at the changeover point of Imperial to Metric, so be absolutely 100% certain you have a UNF thread as a 14mm will screw in and then let go big-time as you compress it.

End result is usually a ruined thread in the spring and damage to whatever stops the cone compressor...

[tom1]

My mate made me a pair (Ex Rolls Royce engineer) which included a under cut on the thread to clean up the threads in the cone.

[newenglandmini]

I'm embaressed the say that all I did was to try threading a 1/2"X13 bolt into the cone.  It threaded in a thread or two, so I assumed that the cone is 1/2"X20 UNF.  I'll purchase a 14 MM bolt and try again.

[dklawson]

The link I posted earlier was not for the tool I have but for one similar in concept.  On mine I made a longer foot with gussets welded to the foot to give it more support when resting on the bulkhead. 

 

Corey, you can make your own tool similar to what was shown in the link but if you do, I encourage you to order your threaded rod from McMaster-Carr (www.mcmaster.com).  Do not get the stuff at the hardware store or home center.  If you are unfamiliar with McMaster, you need to browse their web site.  They sell virtually every item you can imagine.  Their prices are not the best but they are likely to have what you need and 95% of what they list on the web site is in inventory.  Their shipping is incredibly fast.  If you order rod from them you may want to add to it some assorted UNF nuts and bolts for your restoration project. 

 

At the search field on the McMaster web site, enter "threaded rod" in the FIND field.  From the picture links that appear, select "threaded rods and studs".  Then scroll down the left side of the screen and select "steel" and "metric" (or inch).  On the next screen you will be presented with many material types.  The medium grade metric material is 4140 chrome-moly with a tensile strength of 124,000 PSI.  Likewise, if you go back and select 1/2-20 inch rod you will be presented with rod made of "B7" material.  That is also 4140 steel with a slightly higher stredngth of 127,000 PSI.  Those are the materials you want, not the stuff you may find at local hardware stores.  Don't forget to buy metric nuts at the same time.  You will find the 1/2-20 nuts locally... you will have a harder time finding the M14x2 nuts unless you contact a local industrial supplier. 

 

As was noted above, your car was made right about when the thread size changed.  The problem is, the through hole for the 14mm tap is just small enough for the 1/2-20 threaded rod to start in the hole.  As soon as you put any load on it, the threads will pull out.  That's not the end of the world but it may startle you when everything is tightened up and it lets go.  It is also dangerous if you are working "above" the threaded rod.  Make sure the tapped hole is as clean as possible and that the M14 rod will not go in before you attempt to use the 1/2-20 rod.  Regardless, always work standing to the side of the rod, never above it and never put your face above the end of the rod.

[dklawson]

1/2-13 WILL go into the M14x2 and be very, loose, dangerously loose.  The 1/2-13 bolt will NOT go into the 1/2-20 hole, not even one turn.

 

Therefore, assume you have the M14x2 threaded cones and buy rod accordingly.  If the M14x2 rod does not appear to fit your cones, assume their threads are full of rust.  Buy a tap to chase the cone threads and then try the rod again.  Inexpensive metric taps (and this is one you won't use hardly at all) can be purchased on eBay for less than just about any place you can imagine.  To access the threads in the cone you will need to do something like tack weld a piece of long steel tubing onto the tap's shank to reach the threads in the cone.

 

When you put the new cones on, be sure to use anti-seize on their threads during installation.  The anti-seize will help slow corrosion of the threads so the job will be easier in 5-10 years when you or a future owner face this task again.

[newenglandmini]

Thx Doug.  The link is sufficient...same design as yours.  One additional question.  I'm removing my front subframe intact (with powertrain) and I'm going to disassemble the front suspension to replace all of the bushings and joints.  Will I still need the cone tool to replace the cones?

 

Can you confirm that I won't need the compressor tool to remove the old cones?  If so, I will need only the 14MM tool to install the new cones, and I'll purchase the Minispares economy tool.

 

http://www.minispare.../tool.aspx|Back to search

[dklawson]

The rear cones can be taken out without the tool. 

 

Unless your car has adjustable trumpets (Hi-Los) on the front, I would not plan on getting the front cones out without the tool.  There are people who will tell you it can be done, I am not comfortable suggesting you try it.  There are several old threads on this board where members have taken the front apart without the puller but many of those guys have resorted to breaking their old cast trumpets to remove them.  That's OK if you don't mind breaking the parts and are planning on fitting H-Los... but it is not something I would do.

 

You said earlier that a 1/2-13 bolt seemed to go into the cone threads, that suggests that your car already has metric cones.  Make or buy the metric puller and you will have it for both removal and installation of the cones.  As I mentioned, the 1/2-13 bolt will not go into a 1/2-20 thread (like the early cones have).  You can confirm this yourself by trying to thread the 1/2-13 bolt into a 1/2-20 nut.

 

In one of your earlier threads on radius arms I suggested you contact the guys at NEMO about selling the used radius arms.  I was pleasantly surprised to see a NEMO member post a reply.  Did you make any contact with him/them?  It might be worth making that contact see if one of their members already has a cone compressor you could borrow.  They may also have the piloted reamer you need to rebuild your own radius arms.

[dklawson]

½" UNF and 14mm are extremely close together.

 

Minor correction.  The 1/2" thread has a major diameter of 12.7mm, significantly smaller than 14mm.  It is the pitch of 1/2 UNC (13 threads/inch) that is close to the "standard" M14x2 (13 thread/inch = 1.95mm pitch vs 2mm pitch on the 14mm rod).  The tap drill (through hole) for the M14 tap would nominally be 12mm.  So a 1/2 UNC bolt will be a very loose (dangerously loose) fit in an M14 tapped hole. 

[s3swiss]

Some sound advice on here. My fronts were corroded so my compressor wouldn't work. Got them out eventually by lots of levering and pulling using a rope behind the trumpet. I suspect I could only manage it as they were seriously flattened by age (original 60s items I think). I bought a full-on dual thread compressor to install the new metric rubbers. TOP TIP - keep the thread in the compressor oiled - as you do it up to compress the cone, it really tightens up unless oiled. These things are holding a real force (compressed rubber) which can do serious damage - be careful!!

[A-Cell]

....and keep your fingers and hands out of the way please.

[Guess-Works.com]

Normally I would not advocate such a course of action, however as the subframe is on the bench it is possible to remove the front cones without the tool... especially if the cones are pancaked.. 

 

Release as much tension on the cone as possible by removing the top arm bump stop, and then knock the top arm pin out with a punch and hammer...

 

I would recommend wearing safety goggles and rebuilding the tops arm anyway while it's out.

[newenglandmini]

Normally I would not advocate such a course of action, however as the subframe is on the bench it is possible to remove the front cones without the tool... especially if the cones are pancaked.. 

 

Release as much tension on the cone as possible by removing the top arm bump stop, and then knock the top arm pin out with a punch and hammer...

 

I would recommend wearing safety goggles and rebuilding the tops arm anyway while it's out.

 

Doug, I re-tested the cone threads and confirmed that a 1/2"-13 bolt will thread in only about 1/4 turn.  Therefore the cone is the old UNF configuration. As such, and per the above advice, I plan to remove (carefully) the cones on the bench without a tool, and purchase the Minispares metric tool for reassembly.

 

I looked at McMaster-Carr and concluded that the cost of the components and work required to DIY the tool was not worth the effort.  If I run into disassembly trouble, all I will need to do is add a 1/2"-20 rod to the Minispares economy tool.

 

Thanks for all the information and help.