DIY Bed Gap

[Dave HalfordParticipant @davehalford22513]

Posted by Clive Brown 1 on 24/04/2019 16:18:20:

I once wanted to skim the brake discs from a Saab 99. These wouldn't quite fit on my Boxford ME10 so I put spacers under the headstock, which turned it into a ME10.5. Job went quite well as I remember with a carbide tiped tool.

Being a Saab, these discs were quirky in that they included a drum for the separate hand-brake shoes. The working surface of these drums corroded very badly, as they didn't ever do any real work,. I could skim them with the same set-up.

Clive

latest Jeep Grandcherokee has the same system.

[martin perman 1Participant @martinperman1]

Surely the simplest method is to find a hire company or garage who has one of these **LINK** , no dismantling, quickly done.

Wheeler dealears use one in their programme, no connection with the company shown.

Martin P

[Clive Brown 1Participant @clivebrown1]

Posted by Terry Kirkup on 24/04/2019 16:42:16: I agree that current steel discs ain't what they used to be quality wise. I've lost count of the ones I've changed just over the last five or more years, mainly on French motors but also Ford and Fiat. And I wait for Eurocarparts sales before buying new discs, they know my face well in the local branch now.

The Saab discs that I skimmed did have a minimum specified thickness for such work.

I'm not a car enthusiast but I thought that the reduced life of brake discs since the "olden days" stemmed at least in part fom the change from asbestos based maerials for the pads. This forced a change in the material spec. for the discs to a softer value.

[The Novice EngineerParticipant @thenoviceengineer]

HI Myford did a special conversion of the ML7 that used raising blocks , catch up with the details here

http://www.lathes.co.uk/myfordcapstan/ Here

did consider doing this once, …. wokred out quicker and cheaper to buy new discs!

Steve

Edited By The Novice Engineer on 24/04/2019 19:46:02

[Dennis PatakiParticipant @dennispataki22631]

To modify your lathe for more swing, you might consider fabricating an auxiliary spindle pedestal with it's centerline higher than that of your lathe's spindle.

This auxiliary spindle would be mounted on it's own bearings, it's pedestal be bolted to the lathe's bed, and be driven from the lathe's spindle via belt, gears, or roller chain.

You would have to set your cutting tool to a greater height to match the auxiliary spindle.

Accurate alignment would be necessary to avoid turning, boring, or facing tapers, although this might be an easy way to cut tapers if they are needed.

[Alan Waddington 2Participant @alanwaddington2]

Did a pair for a mate once as he was skint, foulest shittiest job ever, rust and crap everywhere, took forever to clean up afterwards, lathe, workshop and myself………..never again.

Unless they off something exotic rare or classic, not worth the aggro, modern discs are dirt cheap and consumable

Personally wouldn’t consider butchering a lathe for the purpose.

[Former MemberParticipant @formermember32069]

[This posting has been removed]

[HopperParticipant @hopper]

Posted by Terry Kirkup on 24/04/2019 13:09:45:

… re-facing the discs from the family's cars and my van which only seem to last a year these days.

Whaaaaat? Something ain't right there.

How many pairs of brake pads are you wearing out in that same one-year period? A disc should outlast many pairs of pads, or at least several.

Are you running cheapazz aftermarket brake pads that are gouging the discs up prematurely? You really need to pay for good quality pads, and discs. No way good quality ones will wear out in a year — unless you are doing incredible high mileages which seems unlikely if you have multiple cars and a van.

You need to fix the cause of the problem, not go hacking up your perfectly good lathe to address the symptoms, over and over again every year.

[Andrew EvansParticipant @andrewevans67134]

Not sure what car you are running but a pair of quality discs for a Ford Focus are less than 30 quid and i would have thought would last 30k miles.

[robjon44Participant @robjon44]

Hi all, add Astra GTE to list of cars with added drum for handbrake, would stick occasionally if left on for long periods ie on forecourt, I carried a hefty plastic mallet to deliver a clout to the middle of the wheel, only happened twice in 40,000 miles, otherwise car behaved like scalded cat.

Bob H

[Howard LewisParticipant @howardlewis46836]

using an Angle grinder on a good machine, sounds like sacrilige and butchery to me.Our last two cars, (Toyota Yaris ) needed new pads after 64K miles and still had the original discs when they left us.

If the discs need refacing every year, it sounds as if the vehicle must either must be standing in a vey saline atmosphere, or being driven and braked VERY hard.

Howard

[Terry KirkupParticipant @terrykirkup37827]

As I said, you all have me convinced it's a bad idea so thanks again for that!

Here's the price of discs for my van, just for info. If I bought the best that would be £216 for the front only. Not as cheap as claimed elsewhere! But I don't buy the "best" and wait for cheap deals coming up. My offspring and their hubbies are all heavy-footed so-and-sos just like me, the wife's car is driven least and suffers most. There probably is something valid about the lack of asbestos in pads now but I think the steel is much inferior too. Most of the changes I am forced to make are due to steering wobble setting in, immediately cured with new discs, not heavy grooving or scoring.

I'm sorry to have dragged model engineering into a driving instructor's course! No further advice (on lathe butchery) required

[Dave HalfordParticipant @davehalford22513]

Terry,

Next time they wobble try driving at 70 on a quiet road and do a 'nearly' emergency stop, but don't actually stop. Then immediately do a second one, after a mile or so when the discs have cooled down try braking normally, the wobble should have gone.

The object is to get the brakes good and hot and re-distribute evenly the resin (glaze) that can form under the pads when people do a big stop at the top of motorway slip roads and leave their foot on the brakes to prevent rolling back. The patches of resin catch unevenly as those areas are 'grippyer ' than the rest of the disc and feel through the steering like the discs have warped (warped discs also make the brake pedal pulse a lot)

Of course you could get the same result by using a dial gauge on the disc to prove it's not warped, then sanding to glaze bust both sides of each disc, but that will take another hour per side.

You should save enough cash to buy a new mill instead.

[Terry KirkupParticipant @terrykirkup37827]

Cheers Dave, appreciate the advice. I will certainly give this a go, shouldn't be too long

Edited By Terry Kirkup on 25/04/2019 15:36:53

[BufferParticipant @buffer]

Isn't it funny that Terry has Golum as his picture but doesn't think his lathe is that precious!

[Nigel McBurney 1Participant @nigelmcburney1]

in the past I have skimmed discs because I am mean,I have a blank of cast iron which has numerous tapped holes so that various dics will fit ,each time the blank is mounted in the chuck I skim the face of the cast blank ,absolute minimum,to ensure it is running dead true ,then make sure the mounting face of the disc has no burrs or dings and the car hub is clean and likewise free from burrs, clean off the disc,with wire brush and and use angle grinder to clean the o/dia where the pads do not touch. if after cleaning and grinding the disc brakes really do need skimming the bolt the disc to the iron blank this gets them really true,then skim to the desired finish,if the lathe is big and the disc small,there the possibilty of skimming both sides at one setting.I had one volvo that covered120000 miles without changing the discs,the o/dia was just cleaned with an angle grinder, one thing I did learn from a specialist volvo mechanic was always use genuine volve pads,I was using ferodo pads at the time and they squeaked and despite using all the well known remedies they still squeaked ,changed to genuine pads and the problem disapeared.My wife had a peugot 306 from new,ran it for 21 years and never replaced or skimmed the front discs ,again only the rusty outer o/dia was cleaned off occasionally. Our cars are always garaged which does help stop the corrosion.

[HopperParticipant @hopper]

Posted by Terry Kirkup on 25/04/2019 14:33:08:.

Most of the changes I am forced to make are due to steering wobble setting in, immediately cured with new discs, not heavy grooving or scoring.

Again it sounds like you are addressing symptoms and not the root cause. Take a look at your steering rack play, ball joints, tie-rod ends, shock absorbers and suspension bushings etc. If those items are in good condition, a slightly out-of-balance partly worn disc will not cause steering wobble.

Some suspension specialist shops will do a free inspection and give you a report on what items are worn and need replacing. Might give you an idea of which way to proceed.

[Terry KirkupParticipant @terrykirkup37827]

Very good Richard, but that picture is actually me

Nigel, I love that!

And Hopper, I don't think that quite explains how brand new discs cure the problem as other issues would surely prevent such an instant fix. I did have a duff wheel bearing once on the van but it manifested itself in other ways too, not just steering wobble. Thank you for the input.

This morning I will speak to the lathe and tell it to relax, it won't be going under the knife after all.

[HopperParticipant @hopper]

Worn out shock absorbers, or worn out shocker mounting rubber bushings, will allow a slightly out of balance disc to bounce up and down a small but critical amount at speed, creating "steering wobble". When you put new in-balance discs on the problem appears to go away — until the new discs also inevitably become slightly out of balance due to wear, and the "steering wobble" returns.

Wear in your steering rack, linkages, joints and bushings will also all add up to amplify the effect.

That's been my repeated experience.

Edited By Hopper on 26/04/2019 09:02:52

[Terry KirkupParticipant @terrykirkup37827]

I'll watch for that, but I've just renewed the wishbones, track rod ends and anti-roll bar bushes on the van so it's as good as it can be for the time being, cheers Hopper.

[HopperParticipant @hopper]

Sounds like you've delved into it then. Strange one. I guess if you are going to be doing discs for multiple vehicles every year you might as well notch that lathe bed and do it yourself rather than buy new discs all the time. Could be a lot of metal to remove from that inverted V way with an angle grinder though. Maybe a hacksaw cut at each end of the section you wish to remove then chip out the area in between with a hammer and chisel. Then finish it off with an angle grinder for a smooth finish.

[Grindstone CowboyParticipant @grindstonecowboy]

Just a thought, but if you were going to remove a section of the ways for a circulr workpiece (i'e' the brake disc), wouldn't some sort of flycutter / boring head held in the chuck and with the tool appropriately orientated make a neat job of it? Some sort of auto-feed to extend the tool each revolution would be required as well. Difficult maybe, but not impossible?

[Terry KirkupParticipant @terrykirkup37827]

Thanks for that thought Rob but the weight of opinion on here is massively in favour of me not touching the thing so I'm running scared now. I'm bowing to all this collective experience. And yes, I think your idea would be difficult for me as a newbie, I think I'm a bit of a "twister" rather than "turner" At least the kids pay for their own discs (usually, eventually!).

[HopperParticipant @hopper]

Ah well if the kids are footing the bill, no point in good old Dad compromising his nice lathe then. New discs all round. Too easy.

[Dave HalfordParticipant @davehalford22513]

Posted by Terry Kirkup on 26/04/2019 11:07:38:

I'll watch for that, but I've just renewed the wishbones, track rod ends and anti-roll bar bushes on the van so it's as good as it can be for the time being, cheers Hopper.

And all of these issues would have been found during the MOT

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