55.2-59 Changing rear axle lugs

[8man]

I have a ZR2 rear axle, and I've started rebuilding it. The lugs on the rear are metric and don't match the ones on the front hubs I got from TCI - 7/16 x 20. After talking to TCI and having the axles out of the tubes for the rebuild anyway, I decided TCI was right and it was going to be easier to replace the rear metric lug bolts with 7/16 x 20. I measured the knurl and got some from Summit that have the measured knurl size of .557".

Now, I need to drill the hubs out, but I talked to an axle shop today and they said the real problem was centering the new hole.

I thought I could just use a drill press, and using the right size drill bit, it would follow the original hole and be centered. Am I missing something?

Thanks.

[1project2many]

With such a large pilot hole, I think the knurls that have formed in the existing holes could cause the drill bit to bounce. Even without the knurls it might be tough to keep a bit centered.

Are you able to sharpen your own bits? It might help to make the bit less aggressive by reducing the face angle.

Masonry bits can be very useful. It may be possible to use a carbide tipped masonry bit on low speed to open up the existing holes. You may have to grind the sides of the carbide tip if it is larger than the hole.

You may also find a tapered carbide burr does a better job of staying centered in the holes. It's not the fastest way to remove metal but it works.

[8man]

Thank you! I know little about being a machinist, so I think I'll let the pros do this one.

[leegreen]

I am not a machinist.
I'd expect a good drill press to have no problem with this. FWIW, here is a guy doing it: https://www.youtube.com/watch?v=ld5aL898qnk

Perhaps naively I'd even think I could do it with a hand held drill.
Given a spare axle I'd grab a hand drill and see what happened. If that left a wobbly hole I'd get a block of steel maybe 1/4" thick, drill it and then clamp it to the axle to guide the drill and stop it chattering.

If I was still not happy I'd look for something like this: https://www.travers.com/product/ttc-...mer-04-090-009
and figure out exactly how far down the reamer I needed to go for the fit I needed.

[dsraven]

have you thought of a step drill to get the hole started symetrically? possibly check the size of the hole you need so that the knurled part has the correct "bite" or it may simply spin when you try to tighten up the wheel. wheel studs should be a "press fit".
the other option is to simply template and drill new holes between the original ones. pilot drill with a drill that has the same size as the web of the final drill

[dsraven]

also, if clamping the axle for drill press or whatever, be aware that the nice smooth area that is the obvious place to use for clamping is also the bearing surface for the axle bearing. use soft jaws in your clamp so as not to mar the surface or clamp further down the axle tube
something like this couldbe a handy tool for a simple redrill on a new surface of the axle flange
https://digital.classictruckperforma...ired%20pattern.

[dsraven]

a piece of rubber hose that fits thebearing surface well wouldbe a good idea to slip on the axle and cover the bearing surface as insurance. otherwise all the work could be for naught if you get a dent or a nick in the surface of the bearing area. even a few wraps of tape would be better than nothing.
personally, I like the redrill on a new surface idea if you don't have the correct tooling to ensure the hole is centered in the old hole's center

[1project2many]

If that left a wobbly hole I'd get a block of steel maybe 1/4" thick, drill it and then clamp it to the axle to guide the drill and stop it chattering.

This could help.


It's not too hard to make a template to drill new holes in the axle. A compass or a set of calipers and a piece of cardstock work well. You'll need to draw two circles first. One that's just slightly larger than the axle pilot so you can put the template over the axle. The second will be the diameter of the bolt pattern. From there you set the compass or the caliper to the distance between the center of two adjacent studs, place the point on the larger circle, and draw a half circle that crosses the bolt hole circle in two places. Move the compass to the center of one of the crossing points and draw another half circle. Repeat until you have a crossing for each wheel stud location. Cut out the center and place the template over the axle.

[dsraven]

I have used an old brake rotor with the outside part cut off when I redrilled a ford 8.8. It already fits. Make a poster board template with the old pattern and then put the new pattern in between those. Punch out ghe old pattern to fit over the existing bolts. Put the rotor part on the axle, slip the template over that. Tape it down or screw a couple lug nuts on with washers under them to hold the cardboard. Then centre punch your new marks onto the rotor part. Remove the whole mess and drill your piot holes through the rotor. Place the rotor back on the axle, bolt it up with a couple of nuts, then drill your new markings onto the axle through the predrilled pilot holes. Just drill enough to leave a center mark on the axle and that way you are not possibly wearing your pilot holes larger in your rotor template.

[8man]

Ok, now you guys have me thinking I should try it. I'll let you know how it turns out.

[mr48chev]

Personally unless the studs aren't the correct length I can't see any wisdom in changing studs. Yes you will have different threads on the rear lugs than the front lugs and if you use chrome lug nuts you may have to buy two sets rather than use one set to have chrome nuts on both ends. Lug wrench size might be an issue but a cross bar lug wrench with both sizes solves that. Being anal to have both ends match really isn't reason enough to go to all the trouble.

The only viable reason for changing is that you have an older set of mag wheels that use the shanked nuts and washers and they only come in SAE threads.

Your main concern is having the correct taper on the lug nuts that work with the wheels you run and not the actual thread of the lug nut.