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DIY Bed Gap

Is this a good idea or not?

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Terry Kirkup24/04/2019 13:09:45
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43 forum posts
32 photos

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.

gapmaybe.jpg

gapmaybe2.jpg

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

Simon Williams 324/04/2019 13:35:07
375 forum posts
65 photos

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

JasonB24/04/2019 13:36:09
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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 Lousick24/04/2019 13:38:38
1039 forum posts
472 photos

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 Evans24/04/2019 13:45:49
209 forum posts

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 yet24/04/2019 13:58:20
2803 forum posts
11 photos

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 Dayman24/04/2019 14:05:05
1464 forum posts
37 photos

+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 Kirkup24/04/2019 14:22:07
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43 forum posts
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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 Wood24/04/2019 14:41:39
1871 forum posts
36 photos

Terry,

Why not use them as work mounting platforms?

Brian

Terry Kirkup24/04/2019 14:42:49
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43 forum posts
32 photos

Hi Brian, can you explain a little more please?

Dave Halford24/04/2019 14:56:07
373 forum posts
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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 Poole24/04/2019 14:57:37
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1857 forum posts
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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 Halford24/04/2019 15:00:50
373 forum posts
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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 Kirkup24/04/2019 15:07:12
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43 forum posts
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Thanks again folks, you have definitely put me off the idea!

ega24/04/2019 15:42:25
1133 forum posts
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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:

dscn1557.jpg

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

dscn1558.jpg

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

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

mechman4824/04/2019 16:10:36
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2324 forum posts
374 photos

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

George.

larry phelan 124/04/2019 16:16:00
397 forum posts
11 photos

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 124/04/2019 16:18:20
218 forum posts
5 photos

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 Kirkup24/04/2019 16:42:16
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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 Wyatt24/04/2019 17:42:04
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15811 forum posts
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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

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