Hey Marty, just got thru perusing your impressive webpage again.
I've got a question regarding bringing back metallic surfaces to a nice shine...specifically those which aren't going to be painted.
I see you sandblast the smaller parts, but I'm wondering about larger stuff like the horizontal mill table.
I've got some needs here and there to clean up some lightly surface rusted plain steel or iron surfaces. I've been using crocus cloth with rags spread out to catch any grit which seems to disappear from the cloth.
However just wondered if there is a better way. I should mention that I'm not currently into complete disassembly, just polishing up parts on nearly [img]/ubb/images/graemlins/smirk.gif"%20alt="[/img] complete machines.
I've seen the Roloc pads which work wonders but the abrasive grit made me nervous on those too. GM Powertrain issues a stern warning on remanufactured long-block engines specifically prohibiting useage of 3M scotchbrite-type materials to clean up pre-gasketed surfaces. Apparently there have been multiple incidents of failure on reman engines which have been traced to the 3M abrasive material which got into engines in the wrong places and never left...
TIA
-Matt
Marty, Need restoration advice
Re: Roloc
Matt the thing that many techs don't understand is that 3M Roloc is a great abrasive, and will not only remove the gasket but is capable of removing large amounts of metal also, in any grit. In my shop we use them every day to clean up surfaces, but we first scrape the gaskets off, we then use 4" pads held almost horizontal to the surface to prevent gouging, and I like to leave a 'ghost' of the original machine marks.
The 'butchers' take a 2" disc, which they have to hold at more like a 30 degree angle to the surface to get it to cut using the disc edge instead of it's entire surface, and grind right through a gasket instead of scraping first. (Too time consuming for them, working on flat rate) Another mistake they make is thinking that the 'aluminum' grade is safe for aluminum, which of course used improperly is not. Put enough speed behind just about anything, (including water!) turns it into an abrasive.
So I guess what I'm saying, is that I don't believe it is the grit getting into the remanned engines that GM is concerned with, it is the improper use of the discs. Also keep in mind that just about all remanned engines and cylinder heads are abrasively cleaned anyway, with steel shot and/or glassbeads.
The 'butchers' take a 2" disc, which they have to hold at more like a 30 degree angle to the surface to get it to cut using the disc edge instead of it's entire surface, and grind right through a gasket instead of scraping first. (Too time consuming for them, working on flat rate) Another mistake they make is thinking that the 'aluminum' grade is safe for aluminum, which of course used improperly is not. Put enough speed behind just about anything, (including water!) turns it into an abrasive.
So I guess what I'm saying, is that I don't believe it is the grit getting into the remanned engines that GM is concerned with, it is the improper use of the discs. Also keep in mind that just about all remanned engines and cylinder heads are abrasively cleaned anyway, with steel shot and/or glassbeads.
[url=http://www.hanzenginehouse.com]www.hanzenginehouse.com[/url]
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Forrest_Addy
- Posts: 76
- Joined: Sat Dec 21, 2002 1:54 am
- Location: WA
Removing rust for assembled equipment
Removing rust from assembled equipment requires a little sensitivity about shed abrasive and its possible intrusion into places it isn't wanted and loss of surface geometry.
Light surface rust comes off with a light persistant rub with a Scotch Brite pad and WD 40. The WD is essential for trapping evolved dust. Work clean in areas about 1 square foot going with the length of the surface. Stop frequently and clean so you can closely monitor progress. WD-40 isn't good for much but it is an excellent cleaning aid..
I use the green ScotchBtire pads. When fresh they're nicely agressive. Whan about half shot they're perfect for chasing rust on sensitive surfaces.
I stone rust off ways with a worn fine India slip stone and WD-40 by gliding the stone over the ways until the metal starts to show. Stoning is the same as wear and it affects the geometry of scraped surfaces in proportion to the foolishness of the user. If forced to use Scotch Brite I go no coarser that the gray pads with a micro-surgery approach.
Once the rust is off there will likely be a dark stain. Removing it may require significant metal removal. I reccommend ignoring the stain. I use the stains on my machinery as reminders to take better care of it in my unheated shop.
Rust can be prevented by local radiant heat (possibly expensive over time), metal perservative (which may be messy and time consuming to remove but they do prevent rust), dehumidifiers as applicable, and heat tape like they use for water pipes (In a permanent problem areas silicone a heat tape to the machine all around. Cover it with aluminum trim channel for appearance). It's amazing what you can do with a few strategically placed light bulbs and thrift store sheets and blankets tented over the machinery. Old sleeping bags are even better.
Power equipment on rusted non-critical surfaces like sheet metal and structure, sure but control the dust. I like to use Scotch brite with a random orbit sander (ROS). ScotchBite will eat off the texture of the sanding pad so put somethinng in between. I use worn ROS disks. The residual abrasive grips the pad but it will squirt out from time to time.
Rol-Lock tooling or bead blasting directly on precision surfaces may get you a few head lumps from from any passing mechanics. Consider them justified reminders.
Light surface rust comes off with a light persistant rub with a Scotch Brite pad and WD 40. The WD is essential for trapping evolved dust. Work clean in areas about 1 square foot going with the length of the surface. Stop frequently and clean so you can closely monitor progress. WD-40 isn't good for much but it is an excellent cleaning aid..
I use the green ScotchBtire pads. When fresh they're nicely agressive. Whan about half shot they're perfect for chasing rust on sensitive surfaces.
I stone rust off ways with a worn fine India slip stone and WD-40 by gliding the stone over the ways until the metal starts to show. Stoning is the same as wear and it affects the geometry of scraped surfaces in proportion to the foolishness of the user. If forced to use Scotch Brite I go no coarser that the gray pads with a micro-surgery approach.
Once the rust is off there will likely be a dark stain. Removing it may require significant metal removal. I reccommend ignoring the stain. I use the stains on my machinery as reminders to take better care of it in my unheated shop.
Rust can be prevented by local radiant heat (possibly expensive over time), metal perservative (which may be messy and time consuming to remove but they do prevent rust), dehumidifiers as applicable, and heat tape like they use for water pipes (In a permanent problem areas silicone a heat tape to the machine all around. Cover it with aluminum trim channel for appearance). It's amazing what you can do with a few strategically placed light bulbs and thrift store sheets and blankets tented over the machinery. Old sleeping bags are even better.
Power equipment on rusted non-critical surfaces like sheet metal and structure, sure but control the dust. I like to use Scotch brite with a random orbit sander (ROS). ScotchBite will eat off the texture of the sanding pad so put somethinng in between. I use worn ROS disks. The residual abrasive grips the pad but it will squirt out from time to time.
Rol-Lock tooling or bead blasting directly on precision surfaces may get you a few head lumps from from any passing mechanics. Consider them justified reminders.
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Matt_Isserstedt
Made the sandblasting mistake in my youth...
I made the mistake which Forrest suggested while rebuilding a water pump for a tractor.
Man it was gonna be perfect...shiny inside and out to show my craftsmanship and "love of the game." New bearings, new packing, I brazed the casting where rust had eaten one of the water outlets...
So I threw the castings (less bearings [img]/ubb/images/graemlins/smirk.gif"%20alt="[/img]) into the glass bead cabinet and away I went.
Everything back together, nicely masked and painted. I put on the fan and made a missing part which actually drove the impeller from the fan blade (sounds wierd but it was missing and the previous owner said...it keeps overheating [img]/ubb/images/graemlins/grin.gif"%20alt="[/img]). Fully greased everything, used RTV on the perfectly clean faces of the flat gasket so it would never leak again.
And then I gave the impeller a test spin.
Strange grinding sound. [img]/ubb/images/graemlins/shocked.gif"%20alt="[/img]
A little radial pressure on the shaft and it stopped.
Turns out I had sandblasted the press-fit between the OD of the outer race and the bored hole in the casting back to a nice slip fit, and my outer race was slipping against the casting under zero-load conditions.
Ohh was I crestfallen. I couldn't go into the shop for a week. But I survived and learned the lesson well. I also discovered bearing retaining loctite, good for gaps up to .015" [img]/ubb/images/graemlins/wink.gif"%20alt="[/img]
Man it was gonna be perfect...shiny inside and out to show my craftsmanship and "love of the game." New bearings, new packing, I brazed the casting where rust had eaten one of the water outlets...
So I threw the castings (less bearings [img]/ubb/images/graemlins/smirk.gif"%20alt="[/img]) into the glass bead cabinet and away I went.
Everything back together, nicely masked and painted. I put on the fan and made a missing part which actually drove the impeller from the fan blade (sounds wierd but it was missing and the previous owner said...it keeps overheating [img]/ubb/images/graemlins/grin.gif"%20alt="[/img]). Fully greased everything, used RTV on the perfectly clean faces of the flat gasket so it would never leak again.
And then I gave the impeller a test spin.
Strange grinding sound. [img]/ubb/images/graemlins/shocked.gif"%20alt="[/img]
A little radial pressure on the shaft and it stopped.
Turns out I had sandblasted the press-fit between the OD of the outer race and the bored hole in the casting back to a nice slip fit, and my outer race was slipping against the casting under zero-load conditions.
Ohh was I crestfallen. I couldn't go into the shop for a week. But I survived and learned the lesson well. I also discovered bearing retaining loctite, good for gaps up to .015" [img]/ubb/images/graemlins/wink.gif"%20alt="[/img]
Re: Removing rust for assembled equipment
Back when slick willy was in the whitehouse the dod sold a lot of machinery and I bought lots of it, but Fortlewis , Wash. would recieve alot and store it outside with no tarps or anything to stop the rust. And then it would take a year of red tape before thay would sell the machinery. I bought some of this as well, but if you have rusted machine tools, to clean it up right you have to rip it down and clean everything by hand there is no fast way to sand the rust and leave the metal.There was a lot of machinery that was not worth the fight and went to the iron pile. The best way to deal with rust is not let it happen in the first place!...Phil in Mt
Re: Roloc
Be careful with the 3M roloc abrasive discs, even the fine grade are quite agressive for some applications. 3M does make different roloc disks called bristle disks which the abrasive surface is made of a bunch of little plastic/rubber fingers impregnated with abrasive material. I have been using them for about a year now and have found they aren't as aggresive and they last about 6-10 times as long as the "regular" roloc disks. I am using the green mostly which if I remember correctly are medium. Link below for them.
Eric... 3M bristle disks
Eric... 3M bristle disks