View Full Version : Best method for drilling 5 evenly spaced holes. In a circle.

02-28-2005, 12:20 PM
I am working on my wheel adaptors for my Chevelle and I have a question for you machinist/smart people.

I have the adaptor sized correctly, now I need to drill and spot face all of the holes for the adaptor. I have two possible methods to do this. First my mill has a digital read out and I could zero the DRO on the center of the adaptor and then use the X-Y coordinates to determine the proper spacing of the holes. Or secondly I have a rotary table for the mill. I could center on the adaptor again and then move out to the C/L of the bolt circle and drill my 5 holes every 72 degrees of rotation.

Any thoughts on this? I would hope if done correctly they should come out with the same results. Just checking for some suggestions.


02-28-2005, 02:50 PM
Use paper….lots of it!!

I have done this before however I had CAD at my disposal. If you do as well have it drawn up and printed at full scale. Place the paper over the part and use a center punch (cause I didn’t have a mill – sill don’t) and go at it. I suppose you could use a pencil and paper to do the same thing but where is the fun in that?

02-28-2005, 03:59 PM
Make yourself a jig.
Use a flat piece of 2 x 6 or a piece of aluminum plate and make an arbor that fits the center I.D. of your adapter with very little slop. Screw this to the 2 x 6.
Set the jig up in your mill, zero the center and then drill two holes spaced for your bolt pattern. Spend some time making sure the radius and 72* angle is deadnuts between the two holes. The easiest way to do this is to use a rotor. Set up the center arbor and use the rotor as a pattern.
You can now set one of your adapters in your jig and drill the first lug hole. (Don't move the jig or you'll have to re-zero the holes to your cutter.) When this is done rotate the adapter 72* and pin it through the "extra" hole in your jig. This establishes the 72* angle so it had better be right. Drill the next hole, spin the adapter again, pinning it through this new hole to the jig.
You can drill all five holes this way and if your jig is right the adapter will be right.
Have fun

02-28-2005, 05:02 PM
Mark, with all due respect, you're making it too difficult.

RJ, You allready know the best method. Clamp it to your table, find center, zero x,y. Go to your coordinates and drill. Easy.

If I were you, I'd either use an endmill and plunge it, or drill undersize and ream to your final size. Much more accurate and consistent that way.

If you want to get fancy, then you chamfer the outside of each hole, and use a small dovetail cutter to put a nice chamfer on the inside of each hole to ease installation.

...Well damn, I have a picture of one I did, but it's too big. I'll email it if you want to see.

02-28-2005, 08:28 PM
The ONLY reason not to simply use x,y on the DRO is if your Y travel isn't long enough. ( I know a guy with a mill like that :( ).

Then use the rotary table and do the 72 degree thingie.

Be sure and use a spot drill to mark the centers before using drill bits, or use end mills and a reamer (as suggested by Matt).


02-28-2005, 09:19 PM
Thanks John, I didn't think of the mini mill factor. :)

This is part of the reason I bought a Newall C80 DRO...it computes bolt circles for you, right at the machine. :) This was before my CAD days though. Either way, if you can come up with the coordinates, it's super simple.

03-01-2005, 02:30 AM
This could help. 5 on 4.75" Diameter Bolt Circle

03-01-2005, 04:15 AM
Mark, with all due respect, you're making it too difficult.

It's not difficult at all Matt;
Actually this is very easy and it makes drilling the adapters a very quick process ONCE the jig is made... Make the jig using the rotary table to drill two holes and the rest of the process is simply drill and pin. I use this process all the time for making model car wheels and it sure beats having to worry about getting every tool move exactly right every time. It turns the process into a no-brainer, especially if you are doing a few pieces.

03-01-2005, 08:30 AM
how about a lathe to find center of bolt spacing and degree wheel or compass. thats how we always do them @ work for couplings if the mills are tied up.

03-01-2005, 09:51 AM
or you could always use a hand held gps!!! :bananna2:

03-01-2005, 11:02 AM
Thanks Guys.

I am most familiar with the rotary table method since I did this allot at the shop that I worked at. However we didn't have a DRO there. The one detail that I left out is that I have several operations on each hole, so I don't think the jig/pining method would work the best.

I will try the DRO. Thanks for the layout Wicked. I work on CAD all day at work, but it is very helpful to have data from someone else to double check your work.

Hopefully I can post some finished photos soon.

And Matt, any photos would be great. [email protected]

03-01-2005, 04:47 PM
Mark, you're absolutely right about making a fixture for doing several pieces on a machine with out a DRO. However, for four pieces, I'd be done with mine before I could be half way through the fixture.

And not that this helps RJ any, but that's the cool thing about the Newall C80 DRO...after it figures your bolt hole locations for you, all you do is start at #1 hole, do your operation, press the "next" arrow, and move to zero,zero again, etc etc. It's super fast, and impossible to screw up once you have it set.

RJ, email on it's way. :)

03-01-2005, 05:30 PM
First choice...3 jaw chuck in my VMC ..
Write a program... set up/touch off tools and run :naughty:
If you are most familiar with a rotary table..I believe that would be fastest on a manual.
Just use light spots to check that the pattern is right, and then use a paint or permanent marker to mark your divisions...less likley to make a mistake when indexing:icon996:

03-01-2005, 05:35 PM
Jeff, out of curiosity, why chuck this instead of machining soft jaws?

What do you use to hold your chuck on the table?

03-01-2005, 06:03 PM
Hey Matt,
We have 3 Jaw chucks that will clamp down flat on the table...Alot faster to clamp down a chuck..Chuck up the part..and indicate your center.
I just made a set of spacers just a couple of months ago...Thats how I did them.
We don't have premade soft jaw blanks where I work..But that is an option

Also...If the spacers are not hub centric..Most lug nuts use a 60deg seating angle...and you need a large enough dia. hole to fit your socket in.
Instead of pressing in studs I used socket head allen bolts..grade 8 with .5" of thread in the spacer with lock washers and locktite.
I made these out of steel because it was free and they were going on a truck..P.S. the pics were taken after they were used ...

03-01-2005, 06:37 PM
Jeff, that sounds like a good project for me. Plain back chuck, make a mount for it and bolt the mount to the table or rotory table. That'd get the hold downs out of the picture.

Do you have a picture of the chuck setup?

03-01-2005, 07:37 PM
Sorry Matt,
I don't have any pictures of the set up.
I have been after them for years to get a digital camera.
So we can take pictures of complicated set ups and save them in a folder with the program on the computer....
But I feel like this :banghead: :hammer:

03-01-2005, 07:43 PM
No biggie, seems pretty simple anyway. Thanks for the tip!

03-02-2005, 11:50 AM
No probleemo.
That is one thing about fabrication and machining.
You NEVER know it all...you can always learn new tricks

03-03-2005, 09:48 AM
Thanks guys. At the shop that I used to work at we commonly drilled and tapped Fluidampers for 6 bolt blower drives. We had a rotary table with a flat back chuck mounted to it. Similar to what Jeff is talking aout I believe. Worked very well, just center and then locate on an existing holes and go from there.

I like the Socket Head Capscrew idea Jeff. Too bad I already bought ARP studs. :hand: I might go with the Cap Screws anyway.

And Matt thanks for the photos and tips. I remebered most of those things, but for us weekend warrior machinist it never hurts to be reminded. :headbang:

Elusive R
03-03-2005, 04:23 PM

I'm planning on eventually running the Z06 wheels on my Elky. Are you making your own adapters because no one makes the proper size or just because you can? I don't have the wheels yet, so I have no idea how thick the adapter needs to be, but I am curious.

Good luck!

03-04-2005, 05:23 AM
I'm making them myself because I now had a desk job and I have free access to a machine shop still. It stinks not being able to work in the shop more.

Basically I am making them for a little less money (excluding time) with higher grade materials. 7075-T651 vs. 6061-T6