View Full Version : Drilling an axle flange ?

07-16-2013, 10:47 AM
A friend has asked me to drill a new bolt circle on a car axle flange. This is a new one for me.
I have no problem drilling the bolt circle but I'm having trouble imagining how I'm going to clamp it securely to the mill table.
Mill is a typical 9x49 Bridgeport clone.
Anyone have any good solutions ?
Pictures would be great.

Frank K
07-16-2013, 12:11 PM
You might want to read some of the threads about not getting sued if something you make fails and someone gets hurt.
As far as the job goes, you need to look carefully at how close to the existing holes the new ones will be and realize that wheel studs generally have a splined section under the head and need to be pressed into the axle flange, hence the holes need to be pretty much round. Possibly rounder than just drilling will produce.
As far as work holding goes, I'd lay it out, then do it on the drill press with the axle hanging thru the hole in the table and the flange supported on blocks and clamped to the table. But then, I'd only do it if the axle was from MY car. Can't sue yourself.

07-16-2013, 12:34 PM
No fear of being sued, lots of meat there. ~ 1/2" thick flange, full circle of steel. I plan to space the new bolt circle so that its spaced evenly between the other pattern.
Plan is to thread the holes and use socket head cap screws threaded in from the back side of the flange as studs. Nearly all aftermarket axles for drag race cars are done like this.
As for layout, I'd prefer to use the digital readout on my mill for the sake of accuracy.
Just daydreaming about the setup, I'm visualizing making a V-block / clamp to clamp the axle to the side of the table, swing the head out over it and "away we go".

07-16-2013, 01:40 PM
This is what I use, spare chuck bolted to a plate with a thru hole,swing the turret over and its ready to go.


Rich Carlstedt
07-16-2013, 01:48 PM
Do you have a DRO ?
If so, trig the holes.
Mount two ( or three) scrap blocks of the right height to the table.
Drill and tap holes , and use bolts to hold the flange using the existing holes.
Done carefully, you will have drilling clearance and automatically be centered on the flange

A.K. Boomer
07-16-2013, 02:02 PM
Geeze JR, nice shiny stuff...

I remember when my mill was new and I had one of my machinist friends over and we were having a beer checking it out, I briefly go upstairs to take a leak and come back down and he's acting like hes just pulling up his pants,,, im like - "you fuque what did you just do to my stuff? " he's like - "thanks for the moment alone",,, really disturbing the way the average machinist thinks about shiny new material things,,,

but have to admit your mill looks pretty damn nice about right now...:p

07-16-2013, 03:23 PM
Mount two ( or three) scrap blocks of the right height to the table.

That won't work when there is 28"-32" of axle shaft underneath the flange.

07-16-2013, 03:39 PM
A Bridgeport head goes 90deg sideways ya know.


07-16-2013, 04:07 PM
Rich said: Do you have a DRO ?
If so, trig the holes.

I used to use Machinery's Handbook's Jig Borer section to calculate the holes, but it's now simpler. Do a search for "bolt circle calculator" and have at it. Here's one: http://cncexpo.com/CircleCoord.aspx

07-16-2013, 05:05 PM
I have a DRO on the mill and it calculates bolt circles, so that's not a problem, its mounting / clamping it that I was having trouble with.
And No, I can't just stand it on the table, its too tall (either way)(flange end down, the mill head interferes with the axle shaft).
And Yes, I know the head will tilt 90 deg. sideways but then what ? I DO have a 8" H/V rotab but the thru hole in the rotab is too small for the axle shaft. Mounted in the vice, I think the head would bottom out on the table before I got it low enough to get the bottom holes.
So far J.Ramsey's solution works best for me, I can take the chuck off my rotab, the chuck has 1 3/4" thru hole. I have a piece of 3/4" Al plate that I can bolt / cantilever over the table edge - that will work for me.
Thanks for the ideas guys.
Anyone with a different / better idea is considered / appreciated as well.

Rich Carlstedt
07-16-2013, 06:55 PM
That won't work when there is 28"-32" of axle shaft underneath the flange.

Poster did not say that and did not provide photo.
When fellows ask for help, it would be nice to post pics as not everyone works with his parts !

Since that is the case, you need to clamp two beams ( 2 x4 x 18 ie.) to one end of the table with beams extended outside the table, and rotate the turret of the mill and extend the ram. Piece of cake . Drill the mounting holes in the beam


Edit: missed one word

07-16-2013, 07:05 PM
I use the same method as J,and I just use the brake drum and a transfer punch for the hole pattern.

Nice sharp drill and pretend your drilling stainless,slow speed and some cutting oil.

07-16-2013, 08:02 PM
Turn the head 90deg.
Clamp the axle in V-blocks or in a vise.
Use coordinate drill hole locations with trig
or Machinist handbook.
Y becomes Z and X becomes Y, feed with X.
(Spindle is always Z, but you get the idea.)
Done. Make sense or??


07-16-2013, 11:30 PM
Sorry guys, I assumed everyone would know what I meant by "car axle".

http://i726.photobucket.com/albums/ww262/cuslog/683-MG25154.jpg (http://s726.photobucket.com/user/cuslog/media/683-MG25154.jpg.html)

So, yeah, its far too long to stand on the table (26" long) and the flange is roughly 6" dia., so too large for any V-blocks that I own ( I'd need them about 12" tall to be able to drill them with the head laid over).

07-16-2013, 11:46 PM
You can use a 90 degree head to get the drill going horizontal. I've done that a few times and it worked OK.

A.K. Boomer
07-16-2013, 11:54 PM
absolutely - like Doozer and Toolguy said.

you would be surprised at what you can fit on a mills table if you don't try to stack it...

http://i146.photobucket.com/albums/r249/AK_Boomer/DSC02512.jpg (http://s146.photobucket.com/user/AK_Boomer/media/DSC02512.jpg.html)

you have bolt hole calc, fire it up and run it through and write down all the coordinates, then just drop the X and sub out the Z for it...

as far as holding goes, turn your vise sideways and grab the lower flange... stack jacks at the other end of shaft and shim and anchor accordingly for stability, where there's a mill there's a way...

07-17-2013, 07:26 AM
Bang! You've got it.
That's what I'm talk'in about.
It makes sense if you don't think about it.

07-17-2013, 08:42 AM
If you can't get it under the mill, turn up a piece of scrap plate so it can sit over the axle flange and locate on a diameter, drill the plate in the mill using your DRO then clamp it onto the flange and drill through the holes - by hand if necessary.

07-17-2013, 01:24 PM
No disrespect to those that want me to roll the head over on its side but J.Ramsey's solution looks to me to be the best for ME and what I have at hand.
That appears to ME to be the simplest / cleanest solution.
Thanks to ALL.

07-17-2013, 03:12 PM
Turning the head would mean you would have to re-tram the head.
From the talk around here, that could take weeks and require many


A.K. Boomer
07-17-2013, 03:24 PM
Right - much simpler to build a separate Jig then to use the machine in a way in which it was intended for :p

although, if he ever decides to go into axle production things could pay off big...

I like JR's rig - nothing a matter with it, just thought he was still looking for a simple solution since after post #4 of JR's he was still seemingly looking for answers, whatever works just "git er done"...

07-17-2013, 03:42 PM
I have hung long objects off the front and back edges quite a few times "J. Ramsey" style. You have to swing the head left or right to clear the knee but its no big deal. With a dro its super easy to pick up center and run the bolt hole program, and it steers you right to the spot.

A.K. Boomer
07-17-2013, 03:52 PM

but I do kinda hate to move my turret because I got it dialed in for lathe mode and it's not as easy as a simple tram, so I try to lay stuff down sideways any chance I get...

07-17-2013, 04:46 PM
No, I won't go into manufacturing axles, But I am a hot rodder / racer and do some work for some of my buddies to help pay for my addictions and re-drilling axle flanges to take a different wheel bolt pattern is not an un-common job and there might be more of it in my future. So a fixture that looks like it would be a quick and easy setup is attractive to ME.:)

07-17-2013, 09:02 PM
Do not use allen bolts get official press in bolts , measure over the splines and drill/bore the holes just a little bit smaller, do not free hand the holes they are accurate for a reason, if its pilot mount with flat seat nuts then go ahead and free hand drill, otherwise the angle will try to make the bolts line up where they are supposed to be. The official bolts can be pulled in with tubular spacers and lubed threads.