Author Topic: sourcing 600 & 800 grit carborundum in the UK (Read 25179 times)

pipemakermike · « **on:** February 20, 2012, 04:13:06 AM »

I have reached the "lapping the cylinder" part of my engine building project and I am having trouble finding a supplier of the finer grades of carborundum for lapping the cylinder and piston. I have got 400grit but need finer.
Any ideas would be helpful

Bluechip · « **Reply #1 on:** February 20, 2012, 04:43:42 AM »

Hi Mike

Manchester Minerals have 600 in Silicon Carbide ... no carborundum though ...

http://www.manchesterminerals.co.uk/acatalog/Tumble_Media.html#a19_2d007

Maybe other lapidary suppliers have it .. dunno

BC

pipemakermike · « **Reply #2 on:** February 20, 2012, 05:50:41 AM »

Thanks BC I have ordered the 600grit carbide from them
still looking for 800 grit and possibly 1000grit

John Rudd · « **Reply #3 on:** February 20, 2012, 06:03:15 AM »

Isnt Diamond lapping paste suitable?

I'm sure I've seen suppliers of that in various grades available.....

Bluechip · « **Reply #4 on:** February 20, 2012, 07:34:53 AM »

Quote from: pipemakermike on February 20, 2012, 05:50:41 AM

Thanks BC I have ordered the 600grit carbide from them
still looking for 800 grit and possibly 1000grit

The Cerium Oxide is like talc. I have used it on a brass cylinder, but it's very slow .

Why not use toothpaste or Basso if you want that sort of finish.

Not that I've done many cylinders, but I don't bother too much about getting a polished bore.
I have a hone, just used that and left the cross-hatching marks in.

The piston will finish it off when it's run.

BC

pipemakermike · « **Reply #5 on:** February 20, 2012, 07:41:50 AM »

Hi John
I already have most grades available in diamond but, a friend who has made a lot of engines is of the opinion that diamond is likely to become imbedded in the bore where as carborundum doesn't. He only uses diamond for finishing a chrome bore and uses a castiron lap for that. Now, I don't have enough experience to know if this is likely to be a problem - any ideas?

One thing that I am sure of is that the quality of the bore and the piston fit are big players in the easy handling of these small Diesels.

krv3000 · « **Reply #6 on:** February 20, 2012, 07:56:04 AM »

HI just my bit your Friend is right diamond will embed itself into soft metals

Fergus OMore · « **Reply #7 on:** February 20, 2012, 10:30:06 AM »

Surely silicon carbide and carborundum are one and the same?
However, probably what you are wanting is in small quantities and I would suggest that you might contact suppliers to dental manufacturers.

However, there are things like tripoli compound which I know has a 600g and car accessory firms do sticks. I've still got a one from then- a brown grade.

Does this help?

Bluechip · « **Reply #8 on:** February 20, 2012, 01:20:44 PM »

Quote from: Fergus OMore on February 20, 2012, 10:30:06 AM

Surely silicon carbide and carborundum are one and the same?

So it is ...

I never knew that. Always thought Carborundum was a sort of Trade Mark ...

Ah well. A bit late now ...

BC

andyf · « **Reply #9 on:** February 20, 2012, 02:31:59 PM »

Quote

I never knew that. Always thought Carborundum was a sort of Trade Mark ...

I think it might be, BC. Perhaps they initially wanted to create an association with corundum (the non-trade name for naturally occurring aluminium oxide), because that too is an abrasice, though not as hard as silicon carbide, of course. "You've tried corundum; now try our new Carborundum, which is much harder" sort of thing.

Andy

pipemakermike · « **Reply #10 on:** February 20, 2012, 04:29:47 PM »

I just remembered that I have a pot of rouge - no idea if it will work - I use it for polishing violin varnish

Bluechip · « **Reply #11 on:** February 20, 2012, 05:19:49 PM »

I seem to remember from my early days at work, the firm used either powdered pumice or rottenstone as a non-embedding abrasive.

Ground up in oil. Can't really remember which it was though.

( It was last century, or the last millenium if you want to really rub it in ... )

Otherwise there is a proprietory US(?) compound called 'Timesaver' ... excellent, but I don't know that it is available in UK anymore.
Never cheap, but just the dogs gonads etc.

There are several grades depending on what you're lapping..

Once had some ( green tin ? ) .. long gone ..

BC

75Plus · « **Reply #12 on:** February 20, 2012, 06:31:51 PM »

Timesaver is still available but, as BC noted, it is priced right up there with Mother's Milk.

$72 dollars per lb.

http://www.newmantools.com/lapping/time.htm

Joe

Fergus OMore · « **Reply #13 on:** February 21, 2012, 06:02:37 AM »

Mike,
Apologies if there is the 'teaching people to suck eggs' thing. It is certainly not intended!

However, I recall 2 quite important references. One is the freebie of the Holzapffel books and apart from a seemingly myriad of information, describe different abrasive and how to sort out- what you create. Great stuff but there is the classic Amateurs Lathe by Sparey who, if my memory is holding out, described using powdered brick dust at some point or other.

Both are well worth a place in anyone's shelf.

Regards

Norman

PekkaNF · « **Reply #14 on:** February 21, 2012, 06:39:59 AM »

I haven't lapped much cylinders, but pretty much all I read about powder laps has basically fallen into two groups:

1) Diamond seems to be used such way that the lap is "charged" i.e. the diamond dust is forced into lap with hardened roller or plate and all extra is brushed away. I don't recall it used "loose". I think that the idea is to use trough as a single grit.

2) Softer abrassives seems to be used loose, often in oil or such paste, where the idea is in amateur use that the particles breaks down to new smaller and sharp particles. Can't remember exactly, but I think it was GEO Thomas who said that the amateur will get away with a single grit.

Laps must be much softer the part and you should never use the working part as a lap. Once I tried to make one taper fit better to boss and just tried to cut corners using a fine valve grinding paste and "couple of go's". It didn't improve. Two wrongs don't make one right in this sphere.

PekkaNF

Fergus OMore · « **Reply #15 on:** February 21, 2012, 11:56:24 AM »

'Twas Ian Bradley

They-- Bradley, Hallows, Westbury, Chaddock, Tubal Cain, Thomas, Martin Cleeve were like Shakespeare's contemporaries-- 'A Nest of Singing Birds' May not translate- but we are now the losers. There is little left of their contribution today- and we are the poorer.

Arnak · « **Reply #16 on:** February 24, 2012, 01:16:01 PM »

Hi Folks,

Has anyone tried valve grinding past in cast iron bores, does that work?

It is easily available in coarse medium and fine in small tubs.

Arnak

Fergus OMore · « **Reply #17 on:** February 25, 2012, 03:03:09 AM »

Ask anyone who has ground in a set of valves on a cast iron head of a motor car or motor cycle their views.

Ask anyone who has re-bored a single cylinder or a twin or four or six.

The answers will vary from one operator to another.

There IS a wealth of corrspondence on the net about various professional boring tools for vehicles.

There is even the story of having to pack one of the first steam locomotive cylinders - with the foreman's felt hat.

I've always wondered whether my great grandfather was involved

krv3000 · « **Reply #18 on:** March 01, 2012, 08:18:03 AM »

HI can Any one remember the Jules yous for polishing gold and silver and used to polish watch lenses its red in color

DaveH · « **Reply #19 on:** March 01, 2012, 08:46:49 AM »

Hi Bob

Jeweller's rouge ?

DaveH

krv3000 · « **Reply #20 on:** March 01, 2012, 09:32:27 AM »

thats it
it dus not inbed itself in to anything you polish i will have to google it and get a price

bry1975 · « **Reply #21 on:** March 11, 2012, 04:21:17 AM »

YUP SiC and Carborundum are the same thing tho the name should mean carbon and corundum(sapphire, ruby stones).

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Author Topic: sourcing 600 & 800 grit carborundum in the UK (Read 25179 times)