DIY Bed Gap

[Terry KirkupParticipant @terrykirkup37827]

I'm just about getting used to my Warco WM290V lathe after buying into the game in November, very late in life. One of the things I had in mind was re-facing the discs from the family's cars and my van which only seem to last a year these days. However the biggest of these discs is up to 10mm bigger in diameter than the lathe swing will accept.

Therefore, my question is, can I cut the bed to give me the room I need or not? The red outlines on the photos show the only chunk I'd need to remove, a few inches of the inverted V section. The green lines on the ways show the limit of apron travel.

I'm also curious as to why the chuck/spindle is centred the way it is, neither over the flat ways or the inverted vees?

Edited By Terry Kirkup on 24/04/2019 13:12:26

[Terry KirkupParticipant @terrykirkup37827]

Is this a good idea or not?

[Simon Williams 3Participant @simonwilliams3]

Hello Terry, good afternoon.

It's your lathe — but…..

I'm in the no don't do it camp, though not because I wouldn't buy a lathe which had been modified so drastically. I might look at it and marvel at the bravery, but I suspect the resale value of said machine has just plummeted. I'm also not too bothered by the argument that you will have affected (detrimentally, but how much I know not) the stiffness of the machine.

I'm anti because I don't think you're going to be able to resurface a disc even after chopping a bit out of the lathe bed. Firstly I don't rate your chances of mounting the disc in a three jaw chuck (run out and grippability) but I don't think you'll get a surface finish worthy of the name. It's a big flat disc and the tool surface speed at the outer periphery is going to be off the scale and chattering (screaming) like fun. As I understand it a 290 is inverter drive, you need low speed torque for this job, not speed.

The finish on the disc would be much better ground, and frankly I think you'll get better results with a linishing disc on a hand held angle grinder!

And how certain are we that there is enough meat on a modern brake disc to allow for a re-surface anyway? What's the thickness lower limit?

There, that's put the kibosh on it! Sorry!

Best rgds Simon

[JasonBModerator @jasonb]

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

 

I'm also curious as to why the chuck/spindle is centred the way it is, neither over the flat ways or the inverted vees?

 

As the carrage sits on the front vee and the rear flat the cutting loads are not going to be over a pair of either. I think you will find the spindle is centered over the whole be give or take a few mm.

Regarding the other questing I'd be looking into why your discs wear so fast unless you are doing many miles or the car is sitting with them rusting away.

You will also find that the two legs of the carrage stop you getting near the disc so tool overhang will be a lot, I have found this when turning 10" flywheels which will hit the yellow bits.

Edited By JasonB on 24/04/2019 13:40:19

[Paul LousickParticipant @paullousick59116]

You will lose the rigidity of the bed which is probably not that stiff already. The new cheaper lathes are built a lot lighter than the older ones and can twist when under load.

Paul.

[Andrew EvansParticipant @andrewevans67134]

I think it would be crazy to do that to a new lathe to save a few quid on new discs. As Simon says if there is a lip on the discs and enough thickness left take it off with an angle grinder with a flap wheel.

[not done it yetParticipant @notdoneityet]

The centre height is given as 150mm. If that is from the ways to centre line, then the lathe should actually swing very slightly more than double, due to the ways being separated? A tool post grinder would finish off the surfacing better than a cutting tool, I think?

I would not be carving up my lathe like that. Even though it is 50 years old! If surface hardened, the bed could easily warp, let alone the risk of reduced bed stiffness.

New discs, unless ventilated, are dirt cheap anyway – unless you are buying from a dealership (when they will likely double the price just for supplying them). Hardly worth the bother, what with time, etc taken into account.

[Jeff DaymanParticipant @jeffdayman43397]

+1 on not cutting a gap into the new lathe. You will compromise its' rigidity.

To reface car disks years ago a friend made an adapter mandrel for the back end of the spindle, and an auxiliary toolholder at the back end of the headstock on his Standard Modern lathe for cutting large ID parts. This setup came in handy for car disks but also for large flywheels. The only thing was, the spindle speed could not be slowed down enough for cutting larger dia items. Sometimes chatter would start when cutting close to the 10 or 11" OD's of the disks and flywheels. It was not easy to slow the drive down mechanically on that lathe and a VFD was out of the question for cost reasons.

Back to the car disks – You are aware that many newer cars have disks that can not be refaced? And that these disks are much less expensive on some cars that they used to be? If you are working on stuff for old cars, fine, but if you are doing newer car repairs I would not bother setting up to reface disks.

[Terry KirkupParticipant @terrykirkup37827]

Wow! Thank you all Gentlemen, I think we have a winner. I half expected a negative reaction and I'll forget all about the idea now under such a deluge

The disc thing is of course incidental, not the main reason for buying the lathe but just an add-on idea, and Simon, I did get a four jaw chuck with the machine so would have been using that if you'd all said "yes". I will now dispose of (or cut up and utilise) the old discs I have laying around, some vented, others solid.

Thanks again All.

[Brian WoodParticipant @brianwood45127]

Terry,

Why not use them as work mounting platforms?

Brian

[Terry KirkupParticipant @terrykirkup37827]

Hi Brian, can you explain a little more please?

[Dave HalfordParticipant @davehalford22513]

Posted by Brian Wood on 24/04/2019 14:41:39:

Terry,

Why not use them as work mounting platforms?

Brian

That's what round drill press tables from the far east are for.

[Mike PooleParticipant @mikepoole82104]

Snap on used to make a slide that bolted on to the car to face the disc in situ powered by the car. The minimum thickness is often stamped on the disc and you may find that refacing will take you under as they don’t leave too much to wear away.

Mike

[Dave HalfordParticipant @davehalford22513]

Posted by Jeff Dayman on 24/04/2019 14:05:05:

Back to the car disks – You are aware that many newer cars have disks that can not be refaced? And that these disks are much less expensive on some cars that they used to be? If you are working on stuff for old cars, fine, but if you are doing newer car repairs I would not bother setting up to reface disks.

This was true back in the seventies as well.

If you go under thickness they warp and thump like crazy through the pedal.

[Terry KirkupParticipant @terrykirkup37827]

Thanks again folks, you have definitely put me off the idea!

[egaParticipant @ega]

Before getting a larger lathe I made and fitted a 9" flywheel to the quill of my mill/drill. This was made from black MS but the idea came from someone who had used a brake disc for the purpose. Mine was faced on the Super Seven by bolting to the faceplate. The finish is adequate but far from perfect:

Another job in the Myford just fouled the ends of the shears and I confess I trimmed them to clear it:

This is not to suggest that I would encourage the OP's suggestion!

Edited By ega on 24/04/2019 15:45:51

[mechman48Participant @mechman48]

+ 1 for all the other comments, don't do it ! … you can get discs reasonably cheap from euro parts / eBay.

George.

[larry phelan 1Participant @larryphelan1]

When I read this post,I blinked,shook my old grey head,and thought,this must be a miss-print !

From my experience [all of which could be written on the back of a stamp ],I would have to say that this is not the brightest idea I have come across,for two reasons.

A It will not do much for your machine,may even do harm,as others have pointed out.

B I would not even attempt to clean up old discs,or indeed attempt to "repair" anything to do with the brakes on my car/van.. These parts are made to last X miles,no more. Like tires,your life depends on them,so,forget it. New discs are cheaper than a wooden box.

Am now going to make a cup of STRONG tea,while I get over this "idea".

[Clive Brown 1Participant @clivebrown1]

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

[Terry KirkupParticipant @terrykirkup37827]

It wasn't a wind-up Stewart

Disc skimming was always an emminently do-able job as many have done in years gone by (nice one Clive, nice one ega), and indeed many garage services provided but 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.

If Simon is right (above) about torque production on my lathe, or lack of, then I can't really see how the bed could twist with 50mm of the vee removed 20mm deep and only on the back way. I manage to stall it now and again trying to part off or take too big a bite, unless the belt's too slack which is quite possible as there wasn't much guidance in the handbook. It's bolted very securely to the stand and the stand to the concrete floor pads and absolutely square in both planes.

However, I bow to all of this opinion and absolutely do not mind being the butt of a (tasteful) joke!

[Neil WyattModerator @neilwyatt]

Raising blocks for the headstick are the obvious answer. You might even get away with using some good solid hardwood, like mahogany from old furniture.

Neil

[not done it yetParticipant @notdoneityet]

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

….

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

Not particularly quirky or only Saab. Peugeot rear brakes had drums for the handbrake. They changed, between 2002 and 2005, to hand brakes using the discs.

[David Standing 1Participant @davidstanding1]

Posted by not done it yet on 24/04/2019 17:43:23:

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

….

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

Not particularly quirky or only Saab. Peugeot rear brakes had drums for the handbrake. They changed, between 2002 and 2005, to hand brakes using the discs.

If I recall correctly, at one time under the Motor Vehicle Construction and Use Regulations in force at that time, from a safety point of view, handbrake mechanisms had to be mechanical, and not hydraulic, operated. The drum within a disc arrangement got round this requirement.

[David George 1Participant @davidgeorge1]

Hi Terry I worked on a 3 ft swing flat belt flat bed lathe and we needed to swing some plates with a 3ft 6 inch swing so we just got some 8 inch packing blocks under the head a bit more extreme than your disks but it solved a problem without major mod to lathe.

David

[SillyOldDufferModerator @sillyoldduffer]

Well, it's Terry's lathe and he can do what he likes with it!

Bodge maybe, but it's an inexpensive modern machine unlikely to become a collectors item. It's just a tool.

Cutting off the section of prism Terry highlighted is unlikely to effect the rigidity of the bed much; I think on the 290 the rear V stops at the headstock anyway. The rear prism has no function at that point – the tailstock can't get anywhere near the proposed gap unless the saddle's been removed.

Jason mentioned the problem that would put me off most which is the difficulty of getting tools close to a large disc on these machines. On these machines the saddle design makes it awkward to approach an unusually large diameter object without overhanging the tool risking chatter and poor finish.

Why Terry's brake discs have such short lives only he can answer. Moving heavy loads in hilly terrain near salt water would do maximum damage. Friend of mine traced his problem to being a keen musician performing 2 or 3 times a week. With the band's heavy kit packed into his car his late night drive home included a long empty ring-road where he would hammer up to several roundabouts at 70mph (possibly faster, ahem) and then slam the brakes on just in case. His discs lasted a lot longer when he took to driving less enthusiastically!

Dave

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