Drilling Out Cylinder Head Studs - Tooling Question

Heya Joe,

First thing to find out is why is the tool breaking? My guess would be he's using a hand drill and the drillbit isn't going straight, or he's in the hole and the drill moves one way or the other, grabbing and snapping.

My suggestion would be getting a magbase drill, and some left hand drills. Sure the magbase will be a somewhat expensive purchase, but at least it will keep the drill straight to the stud and he'll end up having to buy less tooling.

Tom

I don't think a mag drill will be feasible on an in-vehicle engine by itself due to a lack of suitable surfaces to mag it to. I think it might work if you were to weld/machine some adapter plates that could be bolted over head stud holes that did come out and then mag the mag drill to the adapter plate.

Honestly, I think a drill technique training session or two for the folks doing the drilling is likely what is really required. Many of the auto techs I know don't have any machining experience and simply don't understand that they need to keep a drill drilling straight to keep from breaking it.

For bits, I'm thinking that a carbide tipped bit might have some advantage between carbide to drill the hard head studs, and a more ductile steel shaft to be more tolerant of flex.

True, I was thinking that the engine was taken out to rebuild. If it is in the vehicle, a magbase drill would be kinda hard to use.

I've used HSS for this use for a LONG time. Breaking bit's is due to not holding the drill straight. There used to be a drill guide that you could buy that had adjustable hollow legs that you adjusted to rocker studs or exhaust studs and used them to hold the drill straight. I have seen them in a couple catalogs, not sure if MSC or McMaster have them as they wouldn't be considered "precision tools"

Promax 79251 Wolfcraft 28796

Are similar items. With a rework of the base to provide adjustable alignment pins it would be almost the same tool.

I would suggest HSS-cobalt. with TIN or other coating might help alittle more too.

Those studs are semi hard and real tough, the cobalt is the edge you need to get through them.

HTH.

Thank You, Randy

Remove 333 from email address to reply.

You might do some searches on S.E.J.W on bolt removal. Or suggest your neighbor do some looking. The welders suggest putting a nut over the end of the stud and welding it to the broken stud. The heat help free the stud and the nut provides a way to turn it out.

Also ESAB sells something for removing broken bolts.

This is from a post back in 2001 by Michael Bolster

Find a Welding distributor that carries the All-State line of maintenance electrodes from ESAB and ask for Stud Plus. (I know Praxair or Airgas can order them if they do not stock them). The electrode is excellent for removing studs that have been broken off and are recessed down inside the threads. While the electrode burns, the flux coating protects the threads and allows the filler metal to build up to the top of the threads. Then all you need to do is weld a nut on and remove the broken stud.

The following was taken off the ESAB web site:

Stud Plus:

A specially formulated AC/DC reverse electrode designed to be a cost effective way of removing broken studs, bolts, and taps from holes. Work on all grades of steel fasteners - stainless steel, grades 2, 5, 8 and case hardened steel bolts. "Kit" package contains 8 sticks 3/32" diameter, 5 sticks 1/8" and 4 sticks

5/32". Also available in Handi-Pack Display unit. Tensile strength: 120 ksi to 180 ksi Current temperature: AC/DC

Diameter (in.) Length (in.) Wgt(#) and Container Stock No.

3/32, 1/8, 5/32 1# Tube Kit 69001015 3/32 14 1# Tube 69201006 1/8 14 1# Tube 69201007 5/32 14 1# Tube 69201005 3/32 9 5# Tube 69200006 1/8 14 5# Tube 69200007 5/32 14 5# Tube 69200005

Dan

Left hand thread cobalt drills. Forget the tiN

For drilling out studs if they are flush I put a washer and then a nut on top of them and then weld up the nut to the stud. While it is still hot I spray it with kroil oil.

They make a special welding rod for recessed holes but I have never used them but other people say they work great. the flux adheres to the existing thread and keeps it from being damaged and the nut again is welded to the center core developed by the rod.

John

It is not usual to find HSS drills, in a size to drill out head bolts/studs, breaking very often, in fact the usual problem in drilling out bolts is not starting the hole in the center of the bolt or not drilling straight. I suggest a little training.

(Blushingly) I've been using straight HSS drills for drilling almost everything for 50 years, or more, and if you can convince the guy to use a slow drill RPM and a constant feed rate he should have no problems drilling almost everything.

I've never used L.H. drills but I think that they would be an advantage.

My experience with carbide is that they are very difficult to use, in sizes suitable for drilling out bolts, using a hand drill, as they are very brittle.

Most studs come out pretty easily and the last thing to do is to drill them out when all else fails. If the stud is flush take a dremmel with a slitter and cut a screwdriver slot in the stud. Sometimes a tap with a center punch on the outside perimiter will break it loose. If the stud is recessed you can sometimes stick a welding rod to it and turn it out. Experience is a great teacher, in the sixty years that I have been removing broken bolts and studs I tried a lot of methods but every broken stud is different. If you do drill a good colbalt drill works or even a carbide tipped drill.

John

Agreed - I would not try carbide bits for this job. I have found quality cobalt bits to be excellent for the job, particularly when run with a low speed drill motor. My big air drill works well for this, as does my half inch Makita electric (which is not much bigger than many

3/8 inch drills but runs less than half the speed.)

Recall that I didn't suggest solid carbide bits, I suggested carbide tipped bits.

And if it will come out that easily, the left-hand cobalt drill will spin it out in a jiffy.

The brazed carbide bits generally available (used for concrete drilling) do not work well for drilling studs unless you reconfigure the tip (sharpen to the right angle) and the spiral shank does not clear chips well (they are designed to clear cement dust). Sharpening carbide drills requires the special grinding stones used for sharpening carbide tool bits (which many but not all RCMers will have, and also know)

There are likely other carbide tipped drills available that would do the job, but I've never seen or used them. They would definitely be pricier than cobalts - and getting them in left-hand feed might be more problematic as well.

I vividly remember, about 1979, having to remove a broken stud from a turbo manifold on a big Case loader. All the older more experienced guys in the shop had taken a crack at it and burned off the tips of every drill they could think of while I was out on a service call.

I asked them what the worst would be that could happen if I tried something, and they said it's $600 worth of scrap untill someone gets the stud out, so go to it. I blew that sucker out with the acetylene torch, and picked the threads out with a pick. The shop foreman said it was the first time he'd ever seen someone drill and tap a hole with a torch.

Wasn't arguing, just reminiscing :-)

As they say in Catholic Churches, "Bingo!" ...I'm Sicilian so let me slide with that one.

I totally agree and talk about this often. Even micro-vibrations from a machine that is simply not secure or heavy enough can damage carbide's cutting surface in most cases.

If you had an EDM machine available.....

...That fit inside the engine compartment of various vehicles.

Cole drill, or a fabricated equivalent with a foot that can be bolted onto the block surface for nearly perfect alignment.