'Thread' clean-up

I have an oldish Sigma gauge that needs to be come useable again after years of living in seclusion in the dark recesses of the back of the garage. I want to polish up the main support post and the challenge is the dirty/rusty grooves. They are about 4 to 5mm wide and about the same depth.

Unfortunately the post is just an inch or two long for the centres on my lathe and its probably far too heavy to remove the tailstock and just 'chuck' it. My rotary wire brushes struggle to reach the bottom of the grooves, never mind the sides, and are more intent on rounding off the top edges.

I could mess around with bits the string smeared with abrasive but before I waste a day or so doing this, just wondering if anyone has done this kind of job before and has a well proven, tried and tested, method that might get it done in an hour or two instead ?

Gerry

Hi gerry,

Do you have a fixed steady you could use to support the work without the tailstock?

Bo'sun, no unfortunately not. I did think of a wooden block support but if its not perfect I can see the leverage mangling the chuck jaws and didn't want to risk this. .......But the idea is not 100% dead yet.

Congratulations on having a high precision comparator! Well worth taking care of it.

Maybe the way is the hard, manual, way with a hand held wire brush?

The thread is there to adjust the head up and down the column,ratheyr than to provide a great axial thrust.

So wire brush with regular visual inspection.

Other than that, rwsort to chemical means of rust removal

Howard

Yes they are a lovely robust piece of engineering, aren't they. It will be a pleasure to play with when its looking respectable again and its secrets fully understood.

I think you may be right - honest hard work might be the only way !

Gerry

Fixed steadies are awesomely useful once you've made one, especially for big long pain in the neck jobs

Also allows you to use 100% of your lathe bed

Ady1, you are right.... I must have thought that a million times

Clean the first couplr of turns manually. Bore out a block (tufnol, alloy, wood) to the OD of the post. drill two holw onf pitch apart 90 deg to the bore. fit a pin with diameter = groove width in one and a clean-up cutter in the other. run it up the thread with the guide pin behind the cutter.

.

Recently I've been to pick up a 36" vernier gauge in very good condition; the vendor gave me a 40" very rusty one as a freebee.

I didn't want to risk damaging the engraving, but I had some Evaporust in stock; there's lots of sources, many cheaper than this. I certainly paid less, maybe via eBay or Amazon.
https://www.toolstation.com/evapo-rust-rust-remover/p55677

Initially I brushed it on every day, and stored in a poly bag, but eventually found some plastic waste pipe (40mm maybe??)
A plug was made for the end, and the whole rule section suspended in the de-ruster for a couple of days.

It worked well, without damaging the parent metal at all.

Your round bar looks ideally shaped for a similar treatment, but make sure you do a thorough de-grease first.

Bill

In a similar situation I found the rotary wire brushes made for Dremel's, Multi-Tools et al were narrow enough to get down into the grooves. Life time was distressingly short and care was needed to start teh whole brush into teh groove without poking strands outside. I found putting the brush in stationary and winding up from minimum speed worked best but my slots were pretty much exactly brush width.

Results were good.

Clive

If you are willing to clean it abrasively ... I would recommend using a Garryflex block , preferably lubricated with Autosol polish.

MichaelG.

Hi Gerry and all,

Bill has beaten me to it (and stuck his head above the parapet first) - I would support cleaning it of all grease, wire brushing by hand to remove excess rust, then immersing it in Evaporust in a tube. Wire brushing to remove excess rust reduces the amount of Evaporust needed to clean away the residual rust or the degree to which the Evaporust is "used-up" on a given component.

Alternatively (and this is what I do when the component is too awkward in shape to immerse properly, or if I haven't enough Evaporust in stock to do full immersion), I "bandage" the component in paper towels well-soaked in Evaporust,.then cover it in a plastic bag or cling-film to stop it drying out. That way may need multiple applications (and where feasible I often use wire between applications), but it's probably more effective than just brushing on (others may have different experiences). Be careful not to let the towels or component dry out though, as (in my limited experience) you can end up with a hard-to-remove black deposit when it's been allowed to dry out.

If the rust is very light, you may not see any significant traces of it after treatment. If it's more heavy, the formerly rusty patches will probably be darker and I don't think there's much you can do about that without removing metal.

As I have bought quite a few of my tools and machine accessories at knock-down prices simply because they were covered in rust and looked absolutely horrible, yet cleaned up well with Evaporust, I've had positive experiences of this overall approach! I'd certainly suggest trying it over and above a highly abrasive approach that might cause unnecessary wear. Obviously if the screw surface is really pitted with rust and likely to act as a "file" on any nut etc. that engages with it, then all bets are off and a more aggressive approach may be needed to get rid of the pits.

That's my suggestion anyway! Other experiences are welcome. Usual disclaimer, I have no connection with Evaporust other than finding it useful.

Kind regards

Arthur

I've no idea where that long lead thread would be used, is it on something like a height gauge? But if it's for accurate measurement purposes. Then at the very most, I'd first soak it in a rust remover, then very carefully and gently use maybe a thin fine scotch brite disk (the blue one's are considered to be about 1,000 grit) in something like a Dremel or a verified brass and not brass plated wire brush to remove anything left. Even then I'd still probably oil all of the thread to lessen any cutting action of whatever rotary tooling your using. If it's what I think it might be, then that thread would have been at least precision ground and possibly lapped after. At the levels of accuracy I think it might be manufactured to, you can't be too careful, scratch or alter the thread profile at all. Think about how gentle you'd have to be if it was the thread in a micrometer and do the same.

No fixed steady? Pull your tail stocks handle, dial, feed screw and quill out the casting. Then accurately measure the diameter of the quill bore at the front of the tail stock and the OD of that shaft. Turn up a fairly short nylon or comparable plastic stepped bushing to closely fit both diameters and butt up against the front of the tail stocks casting so it can't be pushed inwards. Oil the shaft well, chuck one end in the head stock and slide the other through that bushing. Low rpm so the plastic doesn't friction melt and rotate it. Obviously you'll have to turn it end for end to get access to all of it. But it should work well enough for the purpose.

Pete,

as per Gerry’s opening remarks

”the main support post”

MichaelG.

.

Edit: __ I obviously don’t know which model he has, but the general principle is presumably like this one:

https://www.ebay.co.uk/itm/256201549864

Edited By Michael Gilligan on 27/09/2023 06:53:06

Thanks Michael, not quite what I was thinking or a brand you'd see over here. It's much like the vertical head adjustment on the Quorn. And that design should be easier to set fine adjustments than even the Starrett or Mitutoyo models that have a plain shaft.

You can get "Evaporust" in gel form: I have seen it used on Hand Tool Rescue on Youtube.

Alternatively, the oxide removal solution supplied by the Allendale Group, for their ultrasonic cleaners seems to do a very similar job to Evaporust. I have used this solution by itself - to remove rust without the ultrasonic cleaner - and it is almost magical how you can place a rusted piece of metal in the solution, and a day later, it comes out completely rust free, and smooth, and in some cases as good as new.

Much easier than laborious scraping, grinding, or brushing off the rust - wire brushing can simply polish rust rather than remove it, and you are going to have a very difficult job to get rust out of that thread manually without damaging the thread walls or profile, and introducing lots of random irregularities.

Chemicals are the answer in this instance, I reckon.

Thanks all for you additional thoughts. I have been meaning to buy some Evaporust since reading about it in MEW many years ago. This might be the excuse I need !

Pete/Michael, yes its not a critical precision thread as its just a crude height adjuster, as per the link. (The fine adjustment is a pillar that sits under the component support block on my unit.) So it doesn't matter if I lose some precision in the 'thread'. I suppose what I'm really aiming for is to get a finish in the grooves that has a similar shiney-ish finish as on the OD of the post.

In the meantime I'll re-look at some lathe mods and see if I can cut up some garryflex blocks into 5mm interference-fit strips and see if they have enough mechanical strength to be dragged along the grooves as it rotates.

Gerry.

With the Evaporust and maybe wire brush treatment, at that point I'd probably use what I have for years Gerry. Made in Germany with the brand name of Simichrome. And probably not too hard to find if your in the UK. With a quick check it looks like Your Amazon UK has it. It's not exactly cheap, but a little goes a long way. Those Sigma gauge stands look to be high quality, the shaft OD and groove should polish up as good or better than factory new. And that polish is pretty gentle so it wouldn't be removing a measurable amount of metal. So far I haven't found anything better than that Simichrome with any metal type unless you go to a whole lot more effort with the felt buffs and industrial polishing compounds that would definitely remove more than you want to. The OD would be most easily done with the shaft in your lathe and that polishing compound on a cloth rag. The groove will be a bit more tedious, but a Dremel or similar rotary tool and the small felt buffs they sell for them, plus that polish is what I think I'd use.

I would use a soft wire rotary wire brush as opposed to the normal hard wire type, the soft ones work very well and leave a pleasing finish without damaging the surface. The wire is around 0.005" dia and often stainless steel.

John

How about trying these mops being loose leaf will enable it to clean in the thread. Pick a fine one so not to round over the edges too much