Painted T Slots

I recently bought a new mill (Amadeal VM32L - pretty much like a WM18) and it came with the T-Slots having a thick layer of paint.

So thick that the T nuts had trouble entering the slot. A mild bit of brute force sorted that out, but of course the paint is chipped in places.

I wanted to ask if the paint had any real value. I imagine the idea is to prevent corrosion, particularly in the parts of the T you can't easily get to to clean.

However, I had in mind to use the slots for lining things up. There was an article in one of the mags recently about a vice aligner which I quite fancied.

I might also add that this mill seems to attract condensation more than my CMD10 did, though it's hard to compare like with like.

So, should I strip the paint off to expose the metal? If so what kind of stripper should I use?

Or is the paint a necessary protection?

Thanks as always.

Iain

As I clean T slots with a T shaped scraper then the paint is not going to be around for long. The top of the slot should not be painted as it should be a reference surface to allow tenons on vices or dividing heads to be accurately located. I would think most tables are oily enough to keep rust at bay. I keep mine lightly oiled but wipe it clean before fitting a vice or clamping work on the table.

Mike

I've never seen painted T slots. Usually they get full of oil and swarf and so don't corrode.

If they are binding your T nuts and stopping the alignment of vices and dividing heads etc, I'd scrape the paint back to the metal.

I brought one of these just before Xmas Iain, exactly the same issue bud and did the same thing, brute forced T-nuts so I could hold down my vice. I am new to milling but my 2 cents is to leave the paint finish on if you can, I imagine it would be an absolute nightmare to get some kind of oil in all the nooks and crannes after stripping to protect the bare metal. I'm just going to re-apply paint (albeit less haphazardly). Couldn't you just remove the paint where the vice aligner is going to go and leave the rest (I've not seen a vice aligner so using my imagination at this point).?

Strip it off! PITA and useless. Protect from corrosion by keeping dry / applying oil.

None of the T-slots on my three milling machines are painted and I have no issues with rust. On two of the mills I use flood coolant most of the time and on the third I give an occasional spray of WD40.

I use gauge plate and close fitting cylinders in the T-slots for alignment so it'd be a right royal PITA if they were painted.

Andrew

At a guess, this is of a piece with the practice of picking out parts of a machine with a contrasting or distinctive colour (or, perhaps, leaving those parts in primer or undercoat).

Tee slots in machine tables are machined. The throat, the slot which is at the table surface, is toleranced so that a register can be fitted from it to a holding device and make it easy to fit it parallel to the column. The bottom of the slot is there to hold the tee nut. I suppose these days the slots could be cast in but I doubt on small machines. Just check the size of the throat and machine some keys to fit and align with these.

The consensus seems in favour of removal. But is it best to use paint stripper (and do I need to consider the type of stripper) or scrape? Scrape has been suggested, but that sounds like a lot of work and of course impossible to get into the slot proper...

Many thanks.

Iain

How about using an old end mill, and just run it down the side of the slots. I don't expect the travel will allow you to get right to the ends, but it will break the back of the job.

Try a little paint stripper on a small part. When it has had time to work, try scraping with a bit of aluminium plate, the paint should come off easily. It needs to be removed from the front and back of the tee slot, and also from the underside of the slots to give metal to metal contact for the tee nuts.

Avoid trying to get every trace of paint off, it may compromise the important milled dimensions.

Edited By old mart on 26/01/2020 14:29:26

The paint needs to be removed, so that the sides of the slots can be used to locate keys or dowels for vices, etc, accurately. Paint on the top (the Table ) is a definite No No, that is a reference surface.

FWIW, paint stripper followed by a light hand scraping, so as not to remove any metal.

Once one slot is clean, you could make up a close fitting T nut, and push / pull that along each slot to clean off the remaining paint. (hold it in a chuck in the spindle, and wind the table to and fro, brushing away the paint, as you go.

Howard

My tee-slots in a Warco GH mill (RF-45 clone) was the same. Tee nuts would not slide freely. I made a tee slot scraper from some sheet steel, and the single layer of brittle black paint came away fairly easily. As Howard suggests, a nee nut slid along the slots removes any remaining paint.

Bill

But remember that the tee slots are machined and as long as parallel to the table travel are a useful reference surface. So milling the paint off definitely not recommended and only scrape gently after applying paint removed.

Wait till you have to clean up the paint stripper

I would certainly NOT try to mill it out, nor use anything else that can cut the metal.

Paint-stripper should be OK provided you clean it all off thoroughly immediately after scraping the paint, in case it is corrosive. An alternative depending on the type of paint, would be old brake-fluid, but that is very fluid so be careful not to splash it on the areas you want to leave looking smart.

Generally the T-slots' internal surfaces become oily in normal use, but it would do no harm to run a plug of oil-soaked cloth through to clean them thoroughly and lightly oil the metal.

I use old brushes to clean the swarf out.

Just remember that brake fluid will spontaneously combust on surfaces over 400C. thankfully it likes water a lot too.

I have a Herbert milling machine that was the DEVIL to scrape the swarf out of the tee slots because it was getting hung up on the rough as-cast surface and packing in tight. I painted the bottom of the slots (all of the coolant well in the table in fact) and afterwards the slots were easy to clean out. I use a T shaped scraper like Mike Poole.