Chemico grinding paste for valves only?

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Chemico grinding paste for valves only?

This topic has 12 replies, 8 voices, and was last updated 13 August 2012 at 17:58 by JasonB.

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13 August 2012 at 05:17 #22178
Steve Wan
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@stevewan33894
Chemico grinding paste for valves only?
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13 August 2012 at 05:17 #96249
Steve Wan
Participant
@stevewan33894
Hi folks,

Back again after a break, I just bough a can of Chemico with fine and coarse paste on either end. Thinking of ways to lap my small Sherline lathe bed to level up the wear after 12 years of use.

New to this product, any tips and advise how best I use it? Wonder any lapping youtubes here…

Thanks inadvance.

Steve Wan
13 August 2012 at 08:43 #96251
donkey
Participant
@donkey
Throw the grinding paste away you dont want that near your lathe. start practicing scraping. you also need a flat plate larger than your lathe bed. you ideally need someone to show you how to scrape but you can easily scrape your way to success. with engineers blue an old file and a flat plate( I have used a glass sheet carefully supported on a sheet of ply)you tube has scraping sessions. and remember the blueing looks much worse just before it gets better.Not a very good explanation but good luck. oh yes the file is made into a scraper not used to file metal.

Bri
13 August 2012 at 10:57 #96256
Martin W
Participant
@martinw
Bri

A quick question, not related to Steve's problem, but can you successfully scrape or even make an impact on a hardened lathe bed? Its not that I need to do it but info may be of use in the future.

Cheers

Martin
13 August 2012 at 11:17 #96257
KWIL
Participant
@kwil
I thought the Shearline bed was an anodised aluminium extrusion and therefor no suitable for scraping, grinding or any other "remedial" work?
13 August 2012 at 11:41 #96260
donkey
Participant
@donkey
kwil is correct anodized aluminium should not be scraped as you will remove the surface but on no account should grinding paste be used as it will embed itself in the surface and accelerate the wear. a useful link is……..

**LINK**

martin you should be able to scrape a hard surface if your scraper is harder and sharp I believe some of the lathe beds I scraped were hardened but I was using a carbide scraper one lathe I do remember was a dean smith and grace and their website says the following

The bed was made from a semi-steel mixture with a Brinell hardness of approximately 200.

hpoe this helps.

Bri
13 August 2012 at 11:50 #96262
Ian S C
Participant
@iansc
If the bed is warn enough to require resurfacing, the anodising will be warn through, so the thing to do would be to scrape to flat, then get the bed hard-anodised, and it should do at least another 12 years. Ian S C
13 August 2012 at 13:28 #96270
Steve Wan
Participant
@stevewan33894
Hi all,

Thanks for the fruitful advise but Sherline bed is not an extrusion nor aluminium. Totally a cast iron bed as well as the bed base. The width of the bed is only 5mm to 8mm contact, wonder at this so narrow surfaces worth the effort to scrape?

Simply use a grinding paste clean up the high spots is it easier? Of course, it requires a careful cleaning perhaps a light polish to remove any embeded leftovers.

Any comments

Steve Wan
13 August 2012 at 14:51 #96273
Ian S C
Participant
@iansc
Sorry Steve, I was just following up on Kwills comment. I imagine the headstock is removable, os it will be reasonably easy to get the whole bed flat, a bit of plate glass makes a good surface plate, but I imagine that few shop windows get broken by vandals in Singapore. Ian S C Maybe some wet & dry paper on the plate glass or what ever you use for a flat.

Edited By Ian S C on 13/08/2012 14:53:12
13 August 2012 at 15:05 #96274
Russell Eberhardt
Participant
@russelleberhardt48058
When I rebuilt my Atlas lathe I found that the ways were a couple of thou wider at the tailstock end than under the chuck. Not being confident of my scraping ability at that time I trued them up using a new carborundum oilstone, frequently checking the width with a mike. Although not the "correct" way to do it, it worked a treat.

Russell.
13 August 2012 at 15:42 #96277
KWIL
Participant
@kwil
Steve, could you post a photo of your Sherline? All the Sherlines on their website appear to be the al extrusion variety.
13 August 2012 at 17:56 #96281
Ex contributor
Participant
@mgnbuk
I thought the She(a)rline bed was an anodised aluminium extrusion and therefor no suitable for scraping, grinding or any other "remedial" work?

Steel bed section on my Sheline long bed lathe – every thing else anodised aluminium.

I would not let abrasive pastes anywhere near a machine tool !

Nigel B.
13 August 2012 at 17:58 #96282
JasonB
Moderator
@jasonb
Yep if you download the catalogue its a ground steel bed on an alloy casting.(page 8)

J

Edited By JasonB on 13/08/2012 18:11:18
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