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Polishing screw heads with diamond paste


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I've been making some screw recently out of 316 steel but my stalling point has been polishing the screw heads. After I cut the slot I have been filing them flat then rubbing them in diamond paste.

 

I apply the paste to an aluminum sheet and start with 45 micron diamond paste and rub the screw heads in it. Clean them then repeat with 8 micron and 0.25 diamond paste. However the finish is not good. I'm aware if you buy sets of diamond paste there are 7 grades to go through so it might be I'm jumping sizes to quickly but as the paste is expensive I thought I'd check here first. From start to finish how long should it take to polish a screw head.

 

This is quite frustrating because I feel like I've go the hard bit down but the part that should be easy is not working.

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Doubt that diamond paste will be effective on a filed surface as it will be 'rough' by polished standards.  ! would start with wet&dry papers going down to 2500 grit then go onto the polishing pastes.  Thoroughly clean after every grit/paste size and do on a flat plate.  Dialux bar polishing medium (grey I think for steel) may be better than diamond paste.

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  polishing or restoring screw heads is an art !       with a lathe (or a drill press)  cut the head and then go to "wet and dry" sand paper to 1,000 grit,   you are done.  the slots are a whole different art.     vin  

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How are you holding the screw for polishing? Typically it would be held in a tripod tool if going for a flat polish.

I would recommend a couple of paper steps before polishing, I typically use 20 micron for serious flattening then 12 micron and go straight from there (after cleaning) to diamond paste,
Aluminum is not a good substrate for polishing, the surface oxidizes in minutes and that is as hard as ruby. If you don't want to find or make a tin or zinc plate, thick plexiglass works well. Roughen the surface with a clean file before using.

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16 minutes ago, nickelsilver said:

How are you holding the screw for polishing? Typically it would be held in a tripod tool if going for a flat polish.

I was holding them in a modified collet. Thanks for all the advice everyone on here has given one. Once again I though the answer was simple but it will keep me busy for 6 months.

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2 hours ago, Titanium said:

I'm aware if you buy sets of diamond paste there are 7 grades to go through so it might be I'm jumping sizes to quickly but as the paste is expensive I thought I'd check here first.

What do you use? I buy from China and it's cheap, probably not the best grade but it works fine for me to polish crystals.

Edited by jdm
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This is how I went about polishing clock screw heads. You need a lathe or a screw head-polishing tool that fits in a vice. Start by removing the bur with a flat needle file not to course. Then use emery sticks of various grades down to the finest they have, finish off with the finest crocus paper. Clean the screws. Those screws would be ready to blue. That is how good they will be.   

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On 8/19/2019 at 4:17 PM, jdm said:

What do you use? I buy from China and it's cheap, probably not the best grade but it works fine for me to polish crystals.

I got it from CousinsUK it is £20 to £10 per tube. I know I don't use a lot but that is still £2000 to £4000 per liter (not that I'd use that much in my life). Which is more that most champagne.

I had a second idea. First I cut the head to size -thickness wise not diameter wise- so that it is a little to thick. Then I cut the slot. The head is really untidy at this point. I could then attached a diamond grinding disk (like this one https://www.eternaltools.com/small-diamond-grinding-wheels ).

I could attach this disk into a mini lathe as supposed to a watch makers lathe. I'll clamp the screw into a vice on the cross slide and this will allow me to grind the head to size whilst keeping the head flat and level and prepare it for the first steps of polishing? What does everyone think?

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Are you going for a flat polish or rounded polish? I'm guessing rounded (which is pretty much anything besides mirror flat/black; from slightly rounded to domed). In that case Oldhippy has you on track, chuck the screw by the threads, smooth out the head with a few grades of abrasive paper or stones, then in my case I use a micromotor tool with a felt buff and polishing paste, no need for diamond. White paste for polishing stainless that comes in a stick. Screw spinning in lathe, hit it with the felt buff at 5-10k rpm in the micromotor. You might spend 3 minutes per screw total if they're really rough to begin with.

Micromotor can be Dremel, Proxonn, or fancy pro stuff, the screw doesn't know the difference.

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4 minutes ago, Titanium said:

I got it from CousinsUK it is £20 to £10 per tube. I know I don't use a lot but that is still £2000 to £4000 per liter (not that I'd use that much in my life). Which is more that most champagne.

I guess these are https://www.cousinsuk.com/product/diamond-paste-cousins

They say brand Cousins, which  means made in India or China. Very similar to this https://www.aliexpress.com/item/2028617063.html

12 grades for $7.52 inc. shipping,

I agree with some of the comments above, diamond past is not the best for metal that is relatively soft, other abrasives and techniques can produce better results.

PS, don't worry about Champagne, it's acidic after a while. Italian Prosecco is cheaper, tastier and mixes well to Spritz,

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1 hour ago, nickelsilver said:

Are you going for a flat polish or rounded polish? I'm guessing rounded (which is pretty much anything besides mirror flat/black; from slightly rounded to domed).

I was going for flat. The problem really started because the "normal" polishing techniques were rounding the screw head.

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41 minutes ago, Titanium said:

I was going for flat. The problem really started because the "normal" polishing techniques were rounding the screw head.

My method works with all types. No need to buy bloody paste. If you are going to use a dremel type  tool, you could use emery cloth instead of emery sticks.

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On ‎8‎/‎19‎/‎2019 at 7:42 AM, Titanium said:

I was holding them in a modified collet. Thanks for all the advice everyone on here has given one. Once again I though the answer was simple but it will keep me busy for 6 months.

   if you have a tap and die set,   (and a lathe) just thread a hole in a brass rod and you have the perfect "screw holder".    doe's not work on left handed thread.    vin

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8 hours ago, vinn3 said:

   if you have a tap and die set,   (and a lathe) just thread a hole in a brass rod and you have the perfect "screw holder".    doe's not work on left handed thread.    vin

A very good tip that is Vin.

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There's flat and there's flat. If you're doing a screw for an old high grade (or new) watch that's mirror polished flat you need specific tools and you need to finish on tin or zinc or similar with some sort of paste. Back in the day it was usually diamantine (aluminum oxide), nowadays usually diamond. There's an order of magnitude of effort between pretty flat and shiny and dead flat and mirror finish inspected at 30x magnification.

For a case screw 'pretty flat and shiny' is almost certainly A-OK. No need to get freaky with it.

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  • 2 weeks later...
On 8/19/2019 at 6:18 PM, oldhippy said:

This is how I went about polishing clock screw heads. You need a lathe or a screw head-polishing tool that fits in a vice. Start by removing the bur with a flat needle file not to course. Then use emery sticks of various grades down to the finest they have, finish off with the finest crocus paper. Clean the screws. Those screws would be ready to blue. That is how good they will be.   

I got my emery sticks yesterday and this works very well. I could not find any crocus paper. It is apparently been replaced with something called micro mesh sheets.

I went down to 2500 grit emery sticks then used a felt bob in the micro motor to get a mirror finish. It worked well. I might get some Micro Mesh Sheets and see how they work. Anyone every used these?

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While I've read this with interest and haven't been able to add anything useful to the above I can comment on micromesh.

It's incredible stuff, I use it in model kit making for flatting then buffing clear coat on my car and motorbike models after spraying and curing.

Working through the grades to the finest leaves you with an incredible shiny finish so should fit your needs admirably. I finish with Tamiya polishing compounds but in most cases these aren't really necessary but they also work excellently for polishing acrylic crystals and get regular use for that.

I bought sheets rather than pads as they're better value and would be more suitable for your needs, the pads are small squares and foam backed for modeling to avoid burning through high spots on contours but with the sheets you could attach strips to a flat surface for ease of use.

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  • 6 months later...
On 8/19/2019 at 7:18 PM, oldhippy said:

This is how I went about polishing clock screw heads. You need a lathe or a screw head-polishing tool that fits in a vice. Start by removing the bur with a flat needle file not to course. Then use emery sticks of various grades down to the finest they have, finish off with the finest crocus paper. Clean the screws. Those screws would be ready to blue. That is how good they will be.   

Oftentimes Google translate and other sites for translation and synonyms just isn't enough (english isn't my native language). Can you please try to explain in other words what "the bur" is? I suppose it's part of the screw but I just can't figure it out. :unsure:

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To VWatchie, the burr is the raised knicks from screwdrivers; in machining it's raised metal left at the edge of a cut.

As for different abrasive papers, there are soooo many, and pads and sponges and pastes and so on. If you're going for really shiny, there's a bunch of options. If you're going for original mirror polish there are fewer, and as said above, the techniques get more specific. When you're getting your steel parts checked for micro scratches at 40x under microscope you get really uptight about this stuff.

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18 hours ago, nickelsilver said:

To VWatchie, the burr is the raised knicks from screwdrivers; in machining it's raised metal left at the edge of a cut.

What a brilliantly and well polished way to explain this! Thank you! :thumbsu:

My immediate interest in this topic stems from an idea I have about polishing the bearings of a mainspring barrel and the contacting surfaces of the arbor (Unitas cal. 6325) in an attempt to reduce friction. The barrel already spins sort of freely around the arbor (mainspring not installed) but it's not as good as it can be compared to what I've seen/felt in another barrel. End shake and side shake of the barrel seems sort of fine. Perhaps a tad bit more side shake (can't feel any side shake at all really) would have been desirable but I'm thinking that polishing would both remove some material (we're talking very, very little) and create less friction between the contacting surfaces. I was thinking trying with peg wood and diamond paste, but then I read...

On 8/19/2019 at 4:19 PM, nickelsilver said:

Aluminum is not a good substrate for polishing, the surface oxidizes in minutes and that is as hard as ruby.

Now, this is a silver coloured barrel and I'm not sure what metal/alloy it is made of. I'm thinking that if it is made of aluminium it may not be such a good idea to use diamond paste considering the effect it has on aluminum as you describe.

Perhaps my "problem" is a bit of a luxury problem, but I'd really like to reduce that last bit of friction so that the barrel spins freely around the arbor when given a puff with the blower.

So, any opinions/ideas would be of great interest to me!

BTW, I haven't got a picture of the barrel in question but here is a video of it for anyone interested in seeing it.

Edited by VWatchie
clarification, added video links
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You don't want to use any loose abrasive on a barrel bearing, there's a very real chance it will imbed and then wear away at the barrel arbor. The most common method to improve the finish would be a simple smoothing broach and oil, a little bit from both sides.

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1 hour ago, nickelsilver said:

You don't want to use any loose abrasive on a barrel bearing, there's a very real chance it will imbed and then wear away at the barrel arbor. The most common method to improve the finish would be a simple smoothing broach and oil, a little bit from both sides.

Super interesting! I've seen those smoothing broaches browsing cousinsuk but never understood what they were used for. Would you say that the below video demonstrates how they are used (although I'd add some oil to the broach)? Should I try to get a size as close as possible to the diameter of the holes or what would you recommend?

 

Edited by VWatchie
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They come in sets, and are tapered. The video shows distinctly not the way to use them hahaha. You slide them in the hole, and give a little twist. Sometimes you give a few twists. They don't really remove any metal (yeah microscopically). They burnish the hole. Going from both sides evens out the taper. You want one that fits, but it could fit anywhere along the functional part of the broach.

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