A question for the drillbitists

[8ob]

I could use the new discs as a drilling jig if I spun up some drilling bushes, I can cut the broken bolts down with the gas axe. I have tried to mill off the top of the bolts but they are way to hard for any of the cutters I have here.

There are four of these hubs to do.

 

[God mode restorations]

I have drilled 12.9 HT studs and bolts with cobalt at a very slow speed. Took a while but definitely doable

 

[123hotchef]

The trick with decent carbide is to get it spinning so fast it doesn't have time too break.

hum i have broken them on the lathe too

 

[Agroshield]

The bolts corrode so badly, you will never find the centre of all of them with a bit of tube...

Presumably the holes in the disk are aligned with the bolts. If the bolts are too corroded to pick up their centre from the OD, I wonder if they could be leveraged into helping locate the bolt centres using a bush. You'd just have to get the rotational position of the disk correct and clamp or tack it into place.

Anything you do has to be better than a blind guess with a centre punch.

Edit: 8ob types faster than me!

 

[PhillipM]

Never had much trouble drilling out bolts with carbide tipped drills even in a wobbly hand drill, how do you lot manage to break them all the time?

 

[m_c]

A decent cobalt drill will go through those bolts without any issue. Even HSS would, but it's not likely to last as long.
As has been suggested, I'd use the new disc as a guide, but I'd concentrate on just getting two bolts drilled first, then bolt the disc in place for doing the rest.

As it's only M8 bolts, I'd probably just go straight for a 6.8mm drill, then run a tap through to clear out the threads.

Despite carbide being very tough, it's quite brittle, so any jamming is likely to result in breakage.

 

[Blobber]

Or just send them to Johnny bravo, by the time you've cursed and sworn at them you might as well have paid him

 

[Screwdriver]

If it was me using my limited tooling and experience, I'd chop them down with a Dremel cutoff wheel and grind the stub with a small grinding wheel. Centre punch the concave surface (the bolt position should be visible) and drill it out to tap size.

 

[Kram]

These are excellent, hard but not brittle.

https://www.ebay.co.uk/sch/i.html?_...olsuk&_oac=1&_nkw=cobalt+motamec&_dmd=1&rt=nc

Centre drills, swisstech from zoro are very good but more expensive now.

Dormer A002 are good drills.

I found their recent stuff to be brittle, chip easily, need constant resharpening. Nothing like old Dormer which were great. I have a set from about 1980.

 

[Arclikeharrypotter]

Dormer, guhring, titex, would be brands I’d look at. You’d probably be fine with a dormer A002, but if you want something with cobalt look at dormer A777.

 

[Trevorleach]

Done loads of them, so many it makes me shudder just looking at the pics, what you have there actually looks real good.
You have enough shank left there to either weld an m8/10 nut onto and undo that way or use one of the tapered stud removal tools, 5/16-8mm is the size you need.
When they are real bad you have a bolt that the shank is so waisted, as you undo the head it shears off leaving a ****ty little stub, then its a tapered chisel to remove the bulk of the remains, die grinder to get the remains flat, then dot punch and drill away.
Think the bolts are std M8 8.8 Iirc tightening torque was 30nm ie nowt special
It sounds real bad but the new holes do not have to be perfect so long as the bolt tightens it will be just fine, ie the work would make an engineer cry but will hold just fine.

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[striker]

I would use a spot drill not a centre drill to start. Then a cobalt drill. I use Heller from Toolstation. They will go through those no problem. Use cutting fluid.

 

[gaz1]

cut off as low as you can arc weld above so you get loads of heat into that bolt

should be the same method for those types of bolts to remove them

 

[Moose McAlpine]

https://www.amazon.co.uk/dp/B00MDIFU0M/ref=cm_sw_r_apan_i_1B2AHMR9CNMVB4X9HQDY

These are what i use. They drill through everything i chuck at them, last for ages. I've used them to drill out 12.9 bolts with no issue. You can get them in jobber length too. Got me out of many binds.

 

[bricol]

I could use the new discs as a drilling jig if I spun up some drilling bushes, I can cut the broken bolts down with the gas axe. I have tried to mill off the top of the bolts but they are way to hard for any of the cutters I have here.

There are four of these hubs to do.

I'm all for DIY, but I think I might be reaching for the Yellow Pages and "general engineers" - clamped on a locating bush on a decent sized mill and clock it round for each bolt - repeat for each hub - once set up, should be reasonably quick. Remove the remnants, drill out, helicoil, done.

Or days with a drill press, even a big 'un . . . and wasting time that could be spent better elsewhere.

 

[graffian]

HSS cotter pin drill and a simple guide/bush?

 

[sako243]

@8ob - is this preventing you coming west? If not and you can bring the hubs with you then we'll pop up to Roger's (half way between Guy's place and mine) and he'll have them out whilst we drink a cuppa (you'll like his workshop - and no you're still not getting his shaper, I've had first dibs on that!).

I'm all for DIY, but I think I might be reaching for the Yellow Pages and "general engineers" - clamped on a locating bush on a decent sized mill and clock it round for each bolt - repeat for each hub - once set up, should be reasonably quick. Remove the remnants, drill out, helicoil, done.

Or days with a drill press, even a big 'un . . . and wasting time that could be spent better elsewhere.

Trouble is @8ob has a better equipped workshop than most of the "general engineers" in Surrey. Trouble is he can't find most of it.

 

[Agroshield]

Highly unlikely your insurance company would take the same stance of ,”the new holes do not have to be perfect”....

Highly agree with your remark above about carbide. It is seen as the magic material but for any less than optimal conditions (not so rigid machine, not so rigid workpiece, not so uniform material) its brittleness counts against it. At least when it does break off in the hole, its ability to shatter at a glance helps you to remove it.

You are strictly correct in what you say, but I think the bolts only locate the disk, just like the countersunk screws on a car disk. It looks like the big notches transfer the braking force. I do not think 12 M8 bolts in shear will do much when the brake pads grip the disk. Compare and contrast the size of those bolts with the ones holding the wheel on, which transfer the braking force to the ground. Even if every bolt is removed, once the caliper and pads go over the disk, it cannot go anywhere.

 

[8ob]

Here is where I am with this, I mounted the hubs up on my mill and there is not enough height under the quill with a short drill in a chuck/ collet chuck with a milling cutter to do the job. There is enough height on both my drill stands if I can find suitable drill bits, it wouldn't really matter if these holes went out to m10 but ideally I would like to be keeping them m8. The bolts are only keepers, the rotational forces are taken up on the drive lugs. Cant have the truck off the road too long so I will do one axle at a time. @Johnnybravo could you PM a price per unit and some idea of timescale, I can get them down to you or you can collect from doggers paradise

Bob

 

[sako243]

I would love to see this . Either you drink very slowly or serve tea in 44 gallon drums …
Ive done probably 10 or 12 of these hubs over the years. None were done in a cup of tea‘s time….

I was rather expecting Bob to get lost in Roger's scrap pile for a good few hours first then he'd be distracted by the workshop and eventually he'd get around to realising his tea was cold but before he'd get there Anoush would have cooked us all some delicious biscotti before a meal of roast lamb. Then he'd eventually remember to make a fresh cup of tea and finish that just as the last bolt was being drilled out.

But this is a guy who has the ability to make his own drive gears and hubs for a 45t excavator in the barn workshop out back. I phoned him up a few years ago asking if his lathe was big enough to bore out the centre of a flywheel I wanted for a Land Rover. He said hold on, I'll go and check I can't remember if it's a 4 or 5ft capacity I've got... He came back a few minutes later and said 5ft, I asked if he was expecting me to want him to turn the whole Land Rover at once...