Increase centre bore by 1.7mm

[pipshady]

Ok so I want to fit a set of Jag Wheels to my Volvo V70, same pcd (5x108) but the Jag wheels have a centre bore of 63.4 and my volvos pcd is 65.1. From my research I ve found that most CNC places wouldn't touch them with the cost/hassle involved in doing it? Are there any other ways I can open up the bore myself or am I just going to have to keep searching for a machine shop that will do it.

T.I.A.

Phil

[jaykay]

I used a dremel with a grinding bit, and some valve grinding paste to stop.it clogging.

Took curse word ages.

[Dez]

Router, standard straight cut bit and wd40. It give a surprisingly accurate cut. Doing a 0.85mm cut may be tricky though as the cutter will be so thin, so I'd cut oversize then fit some cheap plastic eBay spigots if you're bothered about it being hubcentric.

[colnerov]

Hi, I did similar once using a hole saw, Use a 65mm hole saw on its arbor and push a 63mm hole or piece of tube saw into it. It will hold itself in because of the set of the teeth. The 63mm acts as a guide to hold the 65mm central. Use WD40 as a cutting lubricant. It's unlikely the saw will be bang on 65mm and will cut the .1mm over or you can take out by hand with coarse emery if needed.

Colin

[g40jon]

For such a small amount of material removal (0.95mm around the edge), I would just mark around the edge with a marker pen, use a half round hand file or a dremmel type rotary burr and a drill mounted flap wheel to tidy up. It doesn't need to be perfect. The centre bore is there to help locate the wheels on the hub, but clearly the better job you make of it, the easier it is to fit the wheels.

[jaykay]

Jan 24, 2017 22:23:09 GMT Dez said:

Router, standard straight cut bit and wd40. It give a surprisingly accurate cut. Doing a 0.85mm cut may be tricky though as the cutter will be so thin, so I'd cut oversize then fit some cheap plastic eBay spigots if you're bothered about it being hubcentric.

Ive never even thought bout using a router on ally. Do just use a standard wood bit? And how easy does it chew through it? Could open up a lot of possibilty for other bits an pieces.

[Dez]

Excerpt from one of my build threads that covers your questions-

Nov 4, 2015 20:45:17 GMT Dez said:

then, on with the window frame. id cut out the centre section and filed most of the edges square yesterday, on and off between other things. id erred on the side of caution when cutting, and made sure id backcut each side so there was more material than there needed to be on the opposite side to where id marked itout , if that makes sense. but this meant there was quite a bit of material to remove to get them square, so i dragged out the big b@stArd file and set to, and that ripped it back pretty quick- but theres no denying it was quite a lot of work! my arms and shoulders know about it today thats for sure. theres probably easier ways to do it, but for a one off piece i was happy doing it this way.
cut out-


and squared up-






its important the edges are dead square and smooth, as the guide bearing in this is going to have to run against them-


that right, its a router. ive seen this technique used before, mostly on alloy wheel centres- id even tried it myself once years ago with mixed results. its very much down to the bits you have being suitable really. but id never seen it used for a cosmetic job like this, where it has to produce a good result.

the test piece on an offcut to get the cutting depth right. it was a bit chattery at the end but i figured it was because it wasnt adequately supported so could vibrate-




so, i clamped the real frame down to my handy lump of RSJ, covered it in lube, and took a deep breath. the results are surprisingly good i think!


i did get a bit of chattering on the corners until i got used to it, but its nothing that didnt sand out easily. more in progress pics-






but be warned, it makes a *bit* of a mess-


once id gone round both sides with the radius, i decided to get real cocky and do a rebate on the inside for the glass too. the results here werent quite as good as the first cut, they required a bit of cleaning up after as the cutter was smaller so tended to clog more, i had to stop quite a lot to scrape all the ally out of it. but with a bit of patience it turned out well-








will deffo be using this technique again, I'm amazed at how well it worked. the router bits were nothing special either, a cheapy £7 for a dozen set from lidl.

[chris y]

You don't need a fancy machine shop with good CNC machines, you need a small company that has a large manual lathe or even the most basic CNC milling machine and will charge you for the one to two hours it will take to do it.

If they are designed to use the centre bore then you shouldnt be using any of the hand tool ideas, it makes balancing of the wheels a bit pointless as a fraction of a millimeter will offset the weight.
Unless you don't care about the spigot and make the hole too big and let the studs do the work.

[g40jon]

Jan 25, 2017 23:15:11 GMT chris y said:

If they are designed to use the centre bore then you shouldnt be using any of the hand tool ideas, it makes balancing of the wheels a bit pointless as a fraction of a millimeter will offset the weight.
Unless you don't care about the spigot and make the hole too big and let the studs do the work.

I can't say I agree with you. For one the centre bore, is in the centre where the effects of any rotational mass would be insignificant. The weight of the material removed would be next to nothing. It will have zero effect on balancing. They are a location aid, nothing more and in any case you can file the centre perfectly accurately using hand tools.
The only work the studs are doing is to allow you to bolt the wheels up to the correct torque. The wheels are held in place by the friction between the two mating surfaces of the wheel and the hub, not the bolts/studs. Think about it, do you really think for example the wheel bolts 10mm are going to survive the amount of shear force a car could apply to them? This is the whole reason wheel bolts shear off when people don't do them up to the correct torque. The are designed to have tensile strength, not shear strength.

[darrenh]

Jan 26, 2017 6:26:32 GMT g40jon said:

Jan 25, 2017 23:15:11 GMT chris y said:

If they are designed to use the centre bore then you shouldnt be using any of the hand tool ideas, it makes balancing of the wheels a bit pointless as a fraction of a millimeter will offset the weight.
Unless you don't care about the spigot and make the hole too big and let the studs do the work.

I can't say I agree with you. For one the centre bore, is in the centre where the effects of any rotational mass would be insignificant. The weight of the material removed would be next to nothing. It will have zero effect on balancing. They are a location aid, nothing more and in any case you can file the centre perfectly accurately using hand tools.
The only work the studs are doing is to allow you to bolt the wheels up to the correct torque. The wheels are held in place by the friction between the two mating surfaces of the wheel and the hub, not the bolts/studs. Think about it, do you really think for example the wheel bolts 10mm are going to survive the amount of shear force a car could apply to them? This is the whole reason wheel bolts shear off when people don't do them up to the correct torque. The are designed to have tensile strength, not shear strength.

agree

the primary load transfer between two mating faces is friction. the nuts/studs provide the clamping load to generate that friction.

so, for nut centric wheels (i.e wheels with a taper in the bolt hole, and nuts or bolts with tapered head) being a snug fit on the hub centre bore is nothing more than an aid to fitment

[fad]

Just don't cut a square when you do it lol

[chris y]

Jan 26, 2017 6:26:32 GMT g40jon said:

Jan 25, 2017 23:15:11 GMT chris y said:

If they are designed to use the centre bore then you shouldnt be using any of the hand tool ideas, it makes balancing of the wheels a bit pointless as a fraction of a millimeter will offset the weight.
Unless you don't care about the spigot and make the hole too big and let the studs do the work.

I can't say I agree with you. For one the centre bore, is in the centre where the effects of any rotational mass would be insignificant. The weight of the material removed would be next to nothing. It will have zero effect on balancing. They are a location aid, nothing more and in any case you can file the centre perfectly accurately using hand tools.
The only work the studs are doing is to allow you to bolt the wheels up to the correct torque. The wheels are held in place by the friction between the two mating surfaces of the wheel and the hub, not the bolts/studs. Think about it, do you really think for example the wheel bolts 10mm are going to survive the amount of shear force a car could apply to them? This is the whole reason wheel bolts shear off when people don't do them up to the correct torque. The are designed to have tensile strength, not shear strength.

You have misunderstood me.
That tiny bit of weight that might not have been removed evenly in the centre is indeed fairly insignificant, what I'm talking about is the possibility of forcing the entire wheel to be slightly off centre. A very small amount will make a big difference to balance.

Of course you could just make it oversized so the wheel cant be held off centre by any inaccuracy in the centre bore and rely only on the studs for centreing, but most car manufacturers  design them to be hubcentric.

I didnt make much effort to look but quickly found info such as this about spacer rings and the importance of centreing - "Centric rings are usually needed only for post-sale rims, since the original rims usually come with a center bore of the right size. Usually the hub centric rings are used with alloy wheels, but sometimes steel rims may need hub centric rings.

The purpose of the centric ring is to perfectly center the alloy wheel to the wheel hub and hence prevent vibration to the steering wheel during driving and the shaking which typically appears around speeds of 40-60 mph.

I'm saying that a manually increased bore makes the hubcentric feature useless.

BTW, I understand very well indeed how fasteners, clamps, forces, tolerances and machining etc etc work and what the purpose of the studs and the centre bore are.
If they were my wheels I'd either bore them out on my own lathe if they fitted (some wont) or use one of the precision sub contractors I use at work and agree a method for them to do it. Probably clock the centre in to within microns on a CNC milling machine and whip it out in one cut.

[slater]

Don't get too excited about it. Wheels just aren't made to a particularly tight tolerance in the first place so a competent file operator shouldn't have an issue.

[DavidB]

If you want to spend a bit of money take it to an engineers who will put it on a lathe and have it done 'properly'
I've had wheels with a too small centre bore and just don't have big enough goodies to do it myself.

[penski]

I'm not sure of the necessity of machining the centre within microns when factory wheels often run a couple of mm out.

*n

[ChasR]

I guess it depends on:

1) How fast you want to go (i.e over 60)
2) How bothered you are about a minor vibration.

I will be honest ; my Stag located on by the nuts and seemed to be OK. The car was not completely vibration free though if I am honest by design ; the driveshafts and torque converter were suspect. But many people have had issues with the GKN wheels, because they locate poorly onto the hub (i.e off centre) and I've been in a couple of cars with this issue ; it's one reason why a few Stags are no longer on their wheels. I again can't comment there as I had a horrendous vibration at 50MPH due to a propshaft issue when I had my stock wheels.