What size drill bit for lug stud.

[Root Cause]

I would find out what press fit you need and go to Grainger or MSCdirect and get the decimal sized reamer you want. It will cost the least and probably the easiest way to finish the job. Just make sure you use some oil when cutting with the reamer and I would run it a lot slower than drill speed. For this size, I would want to run it 150 rpms or so if possible.

 

[brokeasajoke]

Do you have a part number and/or proper application that the stud is supposed to be used for? Maybe it can be looked up that way?

What side are your current holes? Do they match the .542 at the knurl of the old studs?

It seems 35/64 is gonna be as close as you can get without some kind of special tool. 17/32 is smaller than you have now, and 9/16 is too big.

2005-2014 mustang.

 

[LD1]

What size are current holes.

It looks like they must be front wheel studs for those mustangs.

Looking up various other studs.....quite a few actually list knurl size as well as a acceptable hole range.

For example, I saw a .615 knurl stud and said for hole size .606-.613

So it looks like .002-.009 under knurl is a good target.

But you said these new studs were closer to .555???

Everything I saw online for the application said .549"

 

[brokeasajoke]

And I'm pushing hard. Shank that knurl is on is about 530.

 

[LD1]

I wouldnt be afraid to try a 35/64 bit and see what it does.

 

[SPYDERLK]

@Root Cause post #11 says what is needed. A professional result matching that of the original studs is not a job easily accomplished freehand and in place on the vehicle. You need a rigidly controlled aligned setup to assure the hole goes through round accurate and square. What is easy on a machine takes some real planning to do in situ. If only they made the exact size you need in a carbide ball burr. You could pull it through the hole using a variable speed hand drill.

 

[Root Cause]

A reamer is what all machine shops use to make holes a specific size.
Dull reamers cut oversized because pressure = wobble.

You can find a chart that will show you what size pilot hole to drill for a given reamer for a reason.
A reamer will cut oversize if the pilot hole is too small. (more pressure= wobble)
From what the Op states, the current hole size sounds about right.

Freehand reaming with a hand drill will give you a tapered hole until you get some penetration where the reamer finally follows the existing hole. This job requires a good drill press or milling machine.

FWIW, drill bits drill oversize when one flute is wider than the other. Quality drills with a good setup will give you the exact size hole if you drill a pilot hole close to the same size and the drill bit is sharp. Higher rpms and slow travel can give you a decent finish.

 

[/pine]

Why not try shaving a few microns (at a time) off the knurls ?

 

[bcp]

Buy an extra stud or two and get a scrap hub. Use a drill press. Drill or enlarge a hole and and try the stud.

Bruce

 

[brokeasajoke]

Plenty of good thoughts and ideas to chew on here. Thanks for all the replies.