Refurbishing old GRS Benchmate

GRS tools are amazing, and expensive and on the wish lists of many starting jewelers. For the longest time the Benchmate from GRS was on my “eventually, maybe, ..when I am better” wish list but it was just way too expensive for me to rationalize the purchase since jewelry is still just a hobby. Recently though I got the opportunity to buy an older model and I decided that it’s a good time for early Christmas 🙂

I like – and hate at times – refurbishing old tools. So when the Benchmate came and was a bit rusty I decided to give it a good polish and clean it up.

I took it all apart and soaked the rusted pieces in white vinegar for a while and whatever didn’t come off with vinegar I took off using a green Scotch-Brite pad with a bit of WD40. Now vinegar is great and convenient for relatively gently loosening rust but what I didn’t know is that it will also strip the black finish the Benchmate comes with. The black finish is something called black oxide and it’s supposed to add mild corrosion resistance and to minimize light reflection.

*Notice that parts of the pieces that were submerged in vinegar are now bright steel instead of having the black oxide finish.*

Now there is no reason for the Benchmate not to work without the black oxide finish and it’s not overly humid where I live so the rusting shouldn’t be much of an issue but I did like the original finish. There are several ways to achieve that look – hot and mid temperature black oxide process is something done in factories that you need special equipment for. Cold oxide – or cold bluing – is something gun owners use to blacken the barrels of their guns when the original coating wears off and you can do that at home. Note that on chemical level the result is a bit different and the cold blue is not as rust resistant as the hot methods, but it will give you that nice look and some added protection.

Based on reviews I picked a product called Oxpho blue. It’s relatively easy to use but it is a strong chemical so you should exercise caution – don’t drink it, don’t put it on yourself or others, just follow the instructions it comes with and keep it away from pets, children and others who might not have as much common sense as you.

Before you can apply the cold blue the parts need to be clean, rust and oil free. After I got rid of the rust I used a rubbing alcohol to get rid of any oils and grease. You can then apply the oxpho blue using a cotton swab dipped in the solution, leave it on for a few seconds, wipe of excess using a paper towel and burnish it using fine steel wool – then rinse and repeat until you’re happy with the intensity of the effect.

In my case I applied it 2-3 times on every part. Because the oxpho blue contains acids I wiped off the parts with paper towel soaked in water with some baking soda afterwards to make sure the reaction doesn’t continue as that might rust the parts. Brownells have a nice short informative video about using the product on their website.

Well and this is the final product. Isn’t it pretty? 🙂 Well worth the effort in my book.

Note on cleaning the bearings

One thing I messed up during the process was the cleaning of the two small thrust bearings. Their casings were pretty rusty but they were spinning well. Despite that I decided to give them a good cleaning too and took the Scotch-Brite pad with WD40 to them. It got the casings clean in no time but it also got some of the rusty slurry into the bearings causing them to turn much worse. So never do that! 🙂

At this point it might be best to buy new bearings – especially if they are on something that puts more load on them like a lapidary saw – but I decided to try and fix them as honestly they don’t get much heavy use on Benchmate. I followed an advice from a machinist forum:

I put the bearings in a zip lock bag with a gentle cleaning solution and put the bag into the ultrasonic cleaner filled with distilled water (I find it better to contain potentially super messy things in a bag so that I don’t have to clean the whole ultrasonic cleaner later). I wrapped a wire around the bearings and hung it over the edge of the cleaner so that I could shake them a bit from time to time and move them to a less messy area if needed.
The ultrasonic took some mess out and also a lot of the grease that was in the bearings so now they turned even worse 😉
I took a bearing grease and filled the inner ring of the bearings with it and then used two saturated towel papers to force the grease into the bearings (as I haven’t figured out how to take these small guys apart).
I kept repeating step 3 until the grease started coming out around the outer seams of the bearings along with some mess and then did it a few more times to clean it out.
Success! The bearings were now free spinning without any hitching!

As much as I learnt about cleaning messed up bearings… It’s not something I wish to repeat any time soon 🙂 That said I am sure there are better ways to do it and if you know some feel free to comment or message me and I might note it here.