Just this morning I remember I had a number in my phone for a shop about an hour away that was sure to be able to do this. Sure enough, he said sure! Midnight Auto in northern NJ. Going to try and get up there asap.

I made mine out of an adjustable reamer of the correct size, welded a longer shaft onto it and the turned the new shaft down to the bearing size.

There are a number of radius arm rebuild threads, If I remember correctly the technique I used was not considered the best, even though I would think it would stay centered in the bore for reaming.

Having driven a mini with a bent trailing/radius arm, I can tell you the importance of getting it right. The car could be a handful in the wet.

I've only found it fun to drift a mini when you wish to drift the car, not when it wants to.

I made mine from brass bar stock but I have the luxury of a lathe.  You can buy bar stock from online places like McMaster Carr.  It doesn't have to be brass - it could be nylon, Delrin or similar.  I guess even aluminum would be fine but I used brass because it's soft and easy to cut.

Step 1, drill the bar center and tap to fit your all-thread.

Step 2, chuck up the all-thread with the brass nugget threaded on

Step 3, turn the brass to the size you prefer, either the bearing o.d. as Kevin prefers or the bearing i.d. that Doug and I prefer.

Step 4, like we all agree on, swarf is not your pal.  Figure out a foolproof way to manage swarf.    

Where did you get the brass fitting?

You make the reamer's brass/bronze guide bush the diameter that just fits where the needle bearing would be installed.  As long as the guide bushing's bore and OD are concentric with minimal clearances the ream will be properly positioned.

Kevin, I made my ream to fit the needle bearings.  I pack the reamer flutes with grease and advance the reamer slowly thru.  Then I remove the reamer from the drill chuck and pass it the rest of the way through the arm without backing up.  The swarf is caught by the grease and pushed/pulled through the arm by the guide sleeve on my reamer.  It takes a bit of care but there is no swarf in the needle bearings when done.  

I'm guessing the bar would still go straight through, but the turned brass guide on the bearing end would be a tight fit to the bare "shell" of the arm

How do you do them with the needle bearing out? How do you ensure the reamer is perfectly straight?

I always do them with the needle bearing out. The reamer can then go right through. Never fit the new needle bearing first, you will fill it with swarf from the reamer.

If you must ream it with the old bearing in, pull the reamer back out whilst still rotating it clockwise (ie cutting direction). Never reverse a reamer...

So your brass fitting is the size of the arms hole without bearing fitted?......to allow the reamer to be pulled through that end?

edit: oops..just re-read your post stating the bearing is installed....how then is the reamer removed without rotating backwards...or does it simply pull out.

The brass centering sleeve is threaded - but that's not required.  It could have been cone shaped, not threaded and held in place with a spring and a nut for example.  The main thing is to support the reamer so it cuts a true hole in line with the bearing end.  Start with a radius arm that is clean inside, with no leftover grease.  All the shavings have to come out somehow, so any grease will capture the shavings.

Turn the reamer through by hand (T-wrench works great) and while turning you can extract it - once through.

It all seems to make sense. So, the brass end is threaded as well then, correct. As you turn the nut at the top, the treads begin to rotate through the brass bushing, pulling the reamer into the bore? Seems like you should never turn a reamer the opposite direction so how do you get it back out once done?

They are called 'shell reamers'.  //www.ebay.com/itm/13-16-SPIRAL-SHELL-REAMER-HSS-OAL-2-1-2-HOLE-DIA-1-2-NEW-5-155-010-/390459459193?pt=LH_DefaultDomain_0&hash=item5ae9328679

The threaded rod is 1/2" all-thread.  The straighter, the better  I had to turn the all thread on a lathe a few thou for the reamer to fit, then drill a hole through for a split pin to locate and secure the reamer.  It might sound involved but didn't take long.

Thanks. That reamer looks very interesting. i may end up having to go that route. I'm going to start looking now actually. Any luck on where to find that reamer or what it looked like in its original state?

I used the above mentioned reamer and it was still too tight. I used a brake cylinder hone to open it a little, not my best option but when the machine shop did them last time, they only lasted a couple years so I'm not sure what they did....

Interesting! I have access to the correct tool, so its not an issue for me, although I've only done one pair. I can say my arms and shoulders were somewhat achey after.

I restored a Cooper S recently and wrote articles for MM along the way.  Here's a chapter with a pic of the reamer I made and it didn't cost much.  Did the job to a gnats ass too.  The reamer needed is 13/16" which are not hard to locate - but the trick is to keep it on center.  That's what the brass threaded collar does when inserted into the new bearing.  BTW, getting the old bearings out was kind of unpleasant as I recall.

Good luck, you can do it! 

//www.minimania.com/Snarkey_-_Chapter_6

CC, not so. Having worked in an auto machine shop fo 25 years I can tell they don't. I picked up the reamer and a bushing on line from someone here years back. I then machined a couple more bushings that allow me to ream either welded or cast arms with or with out the inside bushings or needle bearing installed. As for lending such tools it does not work out. Turn a reamer the wrong direction and we have a issue. I have been trying to save the metal tubes inside old arms. Cleaning out the arms is important as well. The plastic replacements tend to split when greased. Steve (CTR)

I would think a machine shop should be able to ream them with a lathe or milling machine.

Trying to sort my rear arms currently. I dropped them off at the machine shop that has my motor But he is unsure he has the proper tool for the job. Can the proper tool be rented or does anyone know of a shop in NJ that has lots of experience reaming these bushings.

thanks a lot!