150mm dia grinding wheel, 30mm width ...is such available ?

Basically the question is in the title.

I need to be able to grind the edge of a 25mm x 50mm  aluminium bar in one pass.

I will be cobbling up a shop-made "surface grinder " for the purpose, but I don't seem to be able to source a wide enough wheel.

Any help gratefully received, TIA.

Edited By murrmac on 28/02/2014 15:14:21

Won't you just clog the wheel with the soft alloy as it does not really grind well. Maybe some form of linisher

J

Edited By JasonB on 28/02/2014 16:08:46

Normally you would only grind materials that are too hard to machine in other ways, and a normal wheel should never be used on non ferrous metals.

Yes it will clog eventually but I am only removing like .0015" , and the final finishing will be done by lapping on a granite surface plate with PSA abrasive..

I normally lap the aluminium ( which is cut to 500mm long) on the surface plate without any preparation, and the process goes off fairly quickly, but the latest batch from the supplier has a concavity on the 25mm edges of about .0015", and it takes forever to lap it flat, even starting off with 40 grit abrasive.

Hence the need for prior grinding of the edge.

Edited By murrmac on 28/02/2014 15:53:27

It would help if you could explain what you are making. Grinding aluminium is not normal practice, as has been pointed out, the wheel will clog and glaze and burn the material even if you use a coarse grit wheel. Lapping aluminium is a very strange practice. It is normal for the lap to be softer than the object being lapped, using a surface plate for lapping is only going to ruin the surface plate.

Agree with all the comments above, but perhaps this

http://www.centre-des-abrasifs.com/EN/PRODUITS/detail.php?tid=301&id=366&proid=2487

is close enough for what you want to do. Niko.

Edited By speelwerk on 28/02/2014 17:26:17

Thank you for that link Niko ...I have a feeling that that is exactly what I want.

Dusty, yes, lapping aluminium probably is a very strange practice, but it is in fact one which I have been carrying out for the last 5 years ...it is responsible for a not inconsiderable part of my income.

What I manufacture and sell to the trade are sanding beams of various lengths for use by guitar technicians, to enable them to level frets and fingerboards on guitars, and other fretted instruments. The sanding beams are made out of 25mm x 50mm aluminium box section, and, in use, the 25mm edge has PSA abrasive of varying grits affixed which enable the technician to level the frets ( or the bare wooden fretboard) perfectly.

I have always made these sanding beams by affixing 5 foot long strips of PSA abrasive to my 5' x 3' x 6" Crown granite surface plate and just using brute force and elbow grease to get the edges perfectly straight and flat along the length and across the width. It is fairly demanding work physically but at least it keeps me in shape ...

There is no wear on the surface plate btw ...all the wear is on the aluminium oxide PSA which gets renewed whenever it gets too worn.

The problem I have now is that the latest batch of aluminium box section has been extruded with a slight concavity of about .0015" on the 25mm sides , with the result that it takes forever, and also a great deal of physical effort, to lap the 25mm side dead flat and straight.

Hence my need for a "surface grinder " ...I use the quotation marks because obviously it won't be a Jones and Shipman but I have every confidence that I can rig up a contraption which will enable me to feed (manually) a 500mm length of aluminium under the wheel , which will remove enough material from the edges so that the subsequent lapping becomes markedly less tedious than it is at present.

Instead of a grinding wheel you would do better to feed this under a linishing belt to take the bow out of it.

Could probably rig something up with a woodworking belt sander, the method is often used to thickness thin planks for box making etc. Or find someone with a belt/drum thickness sander and just feed the strips through.

Thanks, John and Jason ...the linishing belt might well be the way to go ... whatever I decide has got to be able to be mounted (ie clamped down) onto the surface plate, so that I have a totally flat reference plane.

Originally I had envisaged a standard bench grinder with a 32mm wide wheel fitted which I could mount upside down on my surface plate with a threaded fine vertical adjuster ( the carriage would be made out of birch plywood). I still favour that idea over the belt sanding concept, simply because I believe that the sanding belt could induce undulations along the length of the workpiece whch might be equally difficult to eliminate in the lapping process.

I have read the posts so far, some years back I had a chap who ran his Alu cylinder head over a large cup wheel on a grinding machine used for cast iron cylinder heads. It needed a new wheel and work was lost for a week if I remember. Management were not best pleased at all as the wheel was very expensive and needed expert truing up on fitting. Under no circumstances would I grind Alu in any way.

Your answer is to use a powerful router, make a jig and get a 1/2" router with a big cutter and clamp it down in your jig and take off as little on each pass as you can. The jig can be a base plate in ply and 2 accurately planed wooden laths and just use the sole plate of router with cutter showing through.

Clive

As others have said grinding Alu is not the best idea, Remember Alu dust and iron oxide make for a interesting sprint out the workshop. Probley best not to name the substance the two make, but you don't want it in your shop

Hi Murrmac

I would make a custom linisher out of a 5 foot? flat bar with a flanged pulley each (Or alternately domed pulleys with one adjustable to track and centre... the belt) and order some custom belts made up, most industrial abrasive suppliers will make custom belts. The flat bar could be supported on a heavier base, that would allow some adjusting jacks (mild steel bolts welded on the back, or better still tapped and flush ground to the face) to be used to level the bar to straightness. You will need to incorporate some sort of stop on the linisher to place the work against and resist the force of the cut,

For an abrasive I would look at Aluminium oxide rather than silicon carbide. The abrasive supplier will know the best grade and type anyway.

You may not even need the surface plate if the jig is made correctly and you use fine grade belts for finishing.

Regards
John

It's okay Mark, we are all (well mostly) grown ups on here. The combination of the two make Thermite, Magneseum and Iron Oxide burn that bit faster than Aluminium and Iron Oxide but believe me, as Mark has indicated it is not a desirable combination and it supplies it's own oxygen so not something you can extinguish.

graham.

Mark, might be worth hunting around your locallity for an engine reconditioner that offers a cylinder head grinding facility, alluminium alloy cylinder heads and blocks have been surface ground by such shops for decades without any fuss!

The cost 'may' be an issue, but most shops will 'talk' about it for oneoffs and may well be offset by the length of time saved jury rigging a (possibly dangerous) machine allowing you to get on with stuff that actually earns you money instead of taking time up - and potentially a trip to A&E!

John

Edited By RJW on 01/03/2014 08:49:00

Thanks to all for replies and suggestions ...

@RJW ... hi John, I did actually ask my car mechanic (who sends his cylinder heads out to be ground) about this a couple of weeks back, and he was adamant that the cost would be prohibitive ...if it was in fact a one-off then maybe it would be doable, but I sell many of these sanding beams every month, so I need an economical way of surfacing them. Your suggestion does raise an interesting point however ...how do these shops prevent the wheel from clogging when they grind the aliminium cylinder head ? Is it in the composition of the grinding wheel, is it by using copious amounts of coolant, or a combination of both ?

@John McNamara ... hi John, good idea in principle, but I doubt I could create a flat enough platen that would generate a totally straight and flat surface on the workpieces. Not to say it couldn't be done , but it is beyond my abilities and facilities at the moment.

@ Mark & Graham ...hi guys, if I was to rig up a home made surface grinder I would have the nozzle of my shop vacuum mounted at the grinding point, so there would be no aluminium dust escaping, and no thermite created.

The other safety issues I would of course take great care with .. the workpiece would be mounted and clamped in a long sled which would be fed manually along the surface plate (and riding against a fence) and my hands would never come anywhere near the grinding wheel (which would be shrouded anyway with a shopmade plywood shield..)

However ... the suggestion that appeals to me the most so far is that of Clive Hartland ... thanks Clive. I am annoyed with myself that I didn't think of that in the first place! The way I will implement it is by using my router table ... the fence will be set just under 50mm from the cutter, and the workpiece fed along (against the direction of rotation natch!) and will be held tight against the fence by featherboards. It will require a dead straight fence at least one metre long and I will also have to give one side of each workpiece a preliminary skiff on the surface plate abrasive just to ensure that there are no high spots on the side which will register against the fence.

The one slight concern I have is that the cutter might leave ripples on the surface which will show up when I take it back to the surface plate and give it a final truing. It might take as long to remove the ripples as it would to do it on the surface plate from scratch. These ripples would not actually affect the functionality of the beam, but I would have to explain this to my customers ... ,hhhmmm ... still I will give it a shot and see how it works out.

Thanks again to everybody for their input.

Murray

Edited By murrmac on 01/03/2014 10:04:31

Edited By murrmac on 01/03/2014 10:05:58

Hand feeding metal into a cutter or grinding wheel is an absolute NO NO, it is one of the most dangerous things you could do in a workshop. You must have complete control over your workpiece, if not the consequences could be horrific. It is apparent that the answer to your problem is for the 'beam' to be milled on the face this would also obviate the need to 'lap' it. Yes, I am also aware that you would need a milling machine with 600mm of travel, which from what has been written is not something you posess. I am afraid you are between a rock and a hard place, do you risk the dangers of what you are proposing or pay for the 'beams' to be machined. I wish you luck. Remember metal will not behave in the same way as wood which can be forgiving, metal will go it's own sweet way unless you have absolute control over it.

Hi

I don't know the answer to this but would a diamond impregnated grinding wheel with plenty water as a lubricant be a non clogging solution to surface grinding aluminium?

Just a thought.

Nigel

Murry, all the shops I've used all have overhead grinders, regularly dress their stones and use coolant, no idea what the composition of the stone is, that's their domain!
the finish can be as fine or coarse as you want, and in fact I've occasionally had to request heads to be lightly skimmed again with a slightly more coarse finish because they got the surface finish looking like a mirror!

If you have several beams to grind, they'd probably set them up and clamp down as a batch and grind the lot in one go, the guys that use these grinders on a daily basis are very savvy when it comes to holding down very wierd cylinder head shapes, your bars would be a piece of cake by comparison!

As regards prohibitive costs, it depends what you call prohibitive, it would be best to go to a shop and ask them, deals can be done but I'm not going to elaborate on that

A typical 4 cylinder 16 valve head costs me around £35 and a V12 head around £50, but V12's are Very long indeed!
I've just measured a Renault 4 cyl 16V head I have here here ready to be taken for machining and it measures 140mm x 430mm and a head around 500mm long wouldn't cost me any more, it should give you an idea on which to base cost, but of course every shop is different and dependent upon your location!
Well worth taking a batch and getting an opinion, it's also very quick, my heads are usually done under an hour including setting up while I wait if arranged in advance!

As others have mentioned, I'd be Very wary of hand feeding metal objects through any grinder or milling machine, metal goes through flesh like a knife through butter, and picking fingers and body parts off the floor is too late to be wishing you hadn't done so! machine shops clamp stuff down with good reason!

John