Table reconditioning

[MrRage]

I’m in the process of restoring a Clausing 8520 milling machine I just picked up and was wondering what my options are for resorting the table. It has a bit of surface rust on the table that make it rough to the touch and a few areas where rust has built up. I want to remove the rust and make the table flat, so would having the table top reground be overkill or should I look into lapping the top of the table?

I really want to rebuild this thing right because it’s a beautiful machine and it still has a lot of years of service left in it.

Some pictures for you guys to check it out – the table directory shows the start of my restoration.

http://epyon.54.org:8000/~dustin/workshop/

[Mcgyver]

offhand, I'd say there is a greater chance of making things worse than better. how bad is the rust? unless the piting is so bad that it's effecting the accurancy, , I would just clean it off - you say its surface rust? The table is integral to the accuracy of the machine don't remove material for appearance sake unless you are solving a mechanical problem.

If its so beat up that it does require resurfacing, I agree doing it on a large surface grinder is the way to go, with a bit of effort put into the set up such that the top will come out parallel to the dovetail - if the dovetail is flat!

if you are resurfacing the table on say a big surface grinder, support it by the dovetails but check for wear with an indcator - its maintaining the same distance from the dovertail surface to the table top the matters. Now chances are that dovetail wear isn't even so a proper job has you scraping the dovetail...can't fly on one wing, so now you're also scraping the mating dovetail. etc etc.

clean up the rust, run over the surface with a steel wool and then a broken file with the teeth ground down (to catch any dings and bruises) then check it out with an indicator to determine if there is a problem before cutting. if the is a problem, its more likely in the dovetail than table top. imo your restoration efforts would be better focused on bearing surfaces, screws, spindle, etc - the places where wear occurs.

Lapping would be the toughest way to do this imo, as it would be difficult to maintain the accuracy of the distance between the top and dovetail.

[cbass]

Isn't there a way to do this on the mill itself without removing the table by using a fly-cutter and extremely light passes? I'm kinda curious about this myself...

Carlo

[Mcgyver]

Carlo, I've not heard of it being done, but that doesn't mean much. The challenge would be will the fly cutter reach the whole table and will your spindle turn slowly enough for a cutter of that dia.

Still I wouldn’t do it just for appearance, a sort of ‘mill-vanity’. If you’ve a problem with the mill that you want to recondition, its likely not with the table top but with the dovetails (because thats the bearing surface), and the first rule with reconditioning a machine is figure out exactly what the problem is before you start removing metal. In a worst case scenario doing so would just replicated a dovetail (wear) problem on the table top

[cbass]

I see what you're saying. I wasn't imagining that the dovetails would be so out of true.

So the only scenario where milling the table in place with the mill might make sense is if the dovetails were in good condition but the table's flatness was compromised due to corrosion or other surface damage (for example, a mill that had been sitting outdoors). Unlikely, I know, but possible, no?

Carlo

[Mcgyver]

sure, and the dovetails probably aren't that bad, I was more trying to point out that unless the rusting was bad enough that it effected the use of the machine, machining it away for cosmetic reasons produced no mechanical win or upside and had the possibility of downside, unless testing showed the the table as warped or something. go ahead and get it ground for cosmetic reasons, just be carefull....my point is that i wouldn't bother if its not solving a mechanical problem, try cleaning it first then start at it with an indicator to see if there is a problem

[RotarySMP]

The problem with fly cutting is that is magnifies the out of tram errors. Just clean off the rust and accept the pitting and discoloration as "Character".

[sdantonio]

Naval (not bellybutton) Jelly will work. I have seen it recently in Lowes. It may not be called naval jelly anymore, but I saw it in the paint section. It is a pink translucent jelly formulation containing phosphoric acid as the active ingredient, used by the navy to remove rust from the hulls of ships.

Coca-cola will work too as it also contains loads of phosphoric acid too. But it also contains lots of other things that are bad for your teath and probably bad for the metal too. Coca-cola was once a popular thing to remove rust from lug nuts on car tires.

******************

Naval Jelly

Description

For safe and easy removal of rust from iron and steel. Naval Jelly is useful for preparing metal surfaces for painting. Paint will adhere better to iron and steel surfaces when cleaned will Naval Jelly. It is also an ideal pretreatment for all galvanized surfaces prior to painting.

Technical Information
Appearance: Clear Viscous Liquid Solubility: 100%
Density: 8.67Lbs./Gal. pH Level: 1
Odor: Mild Rinsing: Complete
Flash Point: None Stability: Stable
Foaming: Moderate

Directions

For general cleaning of iron and steel, apply full strength with a paint brush, roller or sponge. Allow a dwell time of 5 to 20 minutes depending on the amount of rust to be removed. If heavy encrustations are present, use a wire brush to clean before applying. In severe conditions, it may be necessary to apply Naval Jelly several times. If this occurs, allow a longer dwell time, overnight if possible.

Material Safety

This product is for industrial and institutional use only. Corrosive, contains phosphoric acid.

Steven

[cbass]

Thanks for the tips,

Luckily my table looks to be in great condition and I am not about to beautify it. I was just thinking hypothetically. I may end up adding a larger surface on top of my table complete with t-sections in which case I'll try my hand at fly-cutting (after tramming the head properly!).

I still can't understand why they build a knee mill with 17" of y travel and supply it with only a 10" deep table. But this is probably best left to a seperate post.

Thanks again.

Carlo

[MrRage]

Well the table has gotten a lot better with nothing more than some Wd40 and steel wool and some 200/320 grit sand papering.

There are still gouges of metal in the table that are about 0.001” deep and the tables warped about 0.001”. It is hard to say for sure where and how it’s warped because my master surface is 6” short of the entire table length. Once I mark up the table I will get a better idea of the contact points and the geometry of the table.

I plan on scraping the surface down 0.001”, then refining it into a bearing surface. I’d use a surface grinder for this operation if I had one, but I don’t. After the tables flat I’ll flip it over and straitening out the dovetails and the rest of the bearing surfaces.

A lot of work just to clean up and level the table don’t ya think?

PS. Its time I get a digital camera so I can keep updating my projects pictures...

[DareBee]

Mr Rage.
I don't know your line of business, but a table true within 0.001 is usually way more than accurate enough.
Considering that you have identified "where" and "how much" it doesnt take much to shim your vise approprietly if needed.

You gotta do what you gotta do.