Sandblasting / gritblasting tools & machinery

Hi all, my first ever “thread” and a complete newbie so hopefully this is not too stupid a way to start!

I inherited some tools, some of which had seen better days, some with surface rust, grime, and some with more serious pitted rust etc.

I have a small gritblasting setup and restored an alloy Eclipse hacksaw so that it looks like new, together with some basic jigs (e.g. drill sharpening). None of these so far, are “precision” items but next on my list are a set of Angles, and a rusty surface plate.

My question is whether this type of treatment ruins precision surfaces (I’m assuming it would ruin/blunt any cutting surfaces) and to what degree. Would it render a surface plate, lathe bed, angles, slip gauges useless? Also how to protect delicate surfaces if I decide to remove paint from non-precision surfaces to re-paint and to bring to an as-new condition.

There seems to be a lot of old tools on eBay etc. Some are in a poor state, but surely restoring is better than buying from new, better for environment etc as long as the process isn’t more damaging

(I admit I’m also being a bit lazy in avoiding Emery paper and wire wool (and associated elbow grease) but these are also potentially damaging if done over-zealously!)

I’d appreciate thoughts/views and advice from anyone with this kingpin of experience.

Thanks G

If the items just have small amounts of rust and discolouration you might be better with bead blasting. This used small glass beads and is not abrasive. The beads come in a variety of sizes and can be used in sandblasting equipment but you would need to clean all the abrasive out of the equipment first.

Brian

Hi Geraint, personally I wouldn't do any kind of grit blasting or emery cloth on precision ground surfaces. A wire brush and some medium of fine Scott bright type would be about all, followed with white spirit or some other solvent to clean down.

Regards Nick.

The cleaned surfaces need treating quite soon after blasting as they will flash rust given half a chance. So have something ready to treat them when you strip them if you are not going to paint them as the next step.

Martin C

Geraint, I have good results removing rust using low-current electrolysis. Have a look on You Tube - there are numerous demonstrations available.

Good luck,

Brian

It is a myth that glass bead is not an abrasive. That is only true for the first time it passes through the gun and hits something.
As that happens it starts to break down into smaller, but sharper angular particles which can be very abrasive.
In industry we monitor the size of the beads and progressively remove undersize media during the process, in a home environment this will not be possible to achieve with a great deal of success, so you end up with a mixture.

We have some customers who replace the media entirely after only one use, just for this very reason.

I agree, it is best not to blast any critical surfaces with it, you can mask them off if you need to blast other areas for paint removal. You could use walnut shell media which is nice and cheap and is non abrasive.

Phil

My question is whether this type of treatment ruins precision surfaces (I’m assuming it would ruin/blunt any cutting surfaces) and to what degree. Would it render a surface plate, lathe bed, angles, slip gauges useless?

Answer - Yes!!!

Reminds me of the time I went to look at a lathe for a friend of mine to find a really nice 'quality' machine absolutely wrecked by a professional restorer eBay trader. The bed had been attacked with a Scotch Brite mop angle grinder! Nice and shiny but as straight as a dogs hind leg. Never ever use abrasives on precision surfaces unless you are restoring with the correct tools (like a slideway grinder)

For removing flaky paint I find air driven needle guns are excellent if a little noisy.

Martin

All, thanks for your replies. I’ll keep my blasting/emery cloth for suitable hand tools where I can regrind an edge as needed and non precision surfaces and also watch out for the eBay “restored” bargains!
All the best

G

As to rusting AFTER blasting, in a damp emvironment it will start in less than 1/2 an hour ! A protective coating is needed as soon as the work is done. Noel

3M Scotch Brite has aluminium oxide in it just like a grinding wheel only not so much.

If you are unable to use wire wool, try a phosphoric acid rust remover like Jenolite rust remover, you don't want anything that converts rust.

If your surface plate has flaky rust on it then a suitable use for it will be a doorstop. Likewise rusty slip gauges may already be scrap, try cleaning two and see if they still wring and stick together

I have walnut shell media for paint but never did get around to trying it on light rust.

Any pvc insulating tape will resist media providing it will stick down, the soft surface has 'give' to the grit. Same goes for any plastic sheet roughly the same thickness as long as it's held tight enough not to flap in the air blast.

I've found if you don't have a proper filter on the airline you get rust, if you end up with a blasted surface thats grey with little black spots you get rust circles coming out of them, uniform grey and no rust. For this use it's good to have some worn media in with the fresh, the smaller worn grit can get into the rust pits.

Agreed - very noisy but effective. It might be worth noting a small compressor will not keep up and the needles will mark softer metals.

Look into soda blasting for a more gentle 'abrasive'

I was dismayed to find my lever-action tailstock chuck fitting had rusted while in its box, luckily not deeply. A foam nest in a cardboard box (the original packaging) is clearly not best for long-term storage.

Obviously I did not want to damage its M2 taper shank, but I dismantled the device and treated the rusty parts with Restore rust-remover (from ARC - usual disclaimers). It seems very effective, leaving a matt grey surface that needs immediate cleaning and protecting, but didn't seem to have attacked the steel. Admittedly the rusting was only shallow.

Afterwards I greased the device lightly and put it back in its box, but having wrapped it in a greaseproof bag.

On things like slip-gauges, small, scattered pits might not be a problem but if the entire surface has rusted the chances of restoring to full accuracy are slim to say the least.

Careful wire-brushing with a brass-bristled brush might work on delicate surfaces..

If you can mask off the machined parts and just blast the painted areas, you will not do any damage. No trace of the abrasives must be left afterwards. The rust on machined areas can be removed with oily steel wool, much less likely to alter the dimensions.

I have two sets of these one for woodworking and another for working with metal they come in various grit sizes. https://chestnutproducts.co.uk/product/nyweb-pads-single-sheets/

I find them very good the white ones I use on my bandsaw cast table before applying wax which I find keeps the rust away and allows wood to slide but without contaminating it