Am I bad or got a bad batch of diamond plates?
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Tagged: Diamond Plates longevity
- This topic has 17 replies, 10 voices, and was last updated 6 years ago by markh.
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@markh good to have a metallurgist opinion here 🙂 I don’t know how to distinguish “good quality” papers… I know it should be obvious but – what to look for? Any brands? Features?
Regarding the sharpening – that’s exactly what I did – got a pack of wet&dry from local store, glued to the (verified) flat piece of granite countertop and went on with flattening the soles and such. However I found out it really unpleasant for any attempts at sharpening as I’m sharpening my knives cutting edge first (as in opposition to some people trailing the edge), so that’s how I did it few times with irons (resulting in cut paper and gluing another piece of paper instead). I got a small belt grinder as a present, so I will probably use it to true up irons that are mighty out of square and then use the paper on granite for the more coarse part of the job, when leaving plates for finer jobs. But I am a curious man and I am planning to spend one weekend on testing my plates and few grits of paper and check the scratches under a microscope to see what grit they are currently are (as I don’t have much finer methods accessible). I Really thank you for your input.
@filadams
to be honest I was waiting for someone that saw a lot of abused plates to speak up here. So scratches from the heavily used “250” plate don’t feel and look like the ones from wet&dry 250. That is interesting. So I wonder what that “250” on the plate description mean – initial size of the grains?10 April 2018 at 10:08 am #521314@kodi
I think that it may well indicate initial size of the abrasive, but I don’t know if they have the same way of determining grit size for diamond stones and abrasive paper. The wet & dry paper does loose it’s abrasiveness after not too long. If there is a lot of stock to remove we sometimes go for a coarser grit. We have a large coarse ezelap plate that we use for flattening and the such, and that has held up well so far and still cuts pretty quickly. It hasn’t been used intensely by lots of students, but we do still restore a lot more tools than your average woodworker.@ed Regarding the grit size – don’t mix sizes to try to achieve a faster cutting rate – 600 grit is just one step along the way of gradually reducing the particle size that you are using to polish. The 240 grit just has to remove the scratches of the 180grit. The 320 is to remove the scratches of the 240grit and so on… We used to rotate the specimen by 90 degrees between each change in grit size so that we could see when we had removed the scratches from the previous grit. Then it was time to move on to the next finer grit – again rotate the sample and remove the scratches then move on ever finer. 600grit was when we moved to diamond pastes on our polishing wheels. The aim was the same – remove the previous scratches and a little more (remember that we were trying to reveal the metallurgical microstructure which meant that we were concerned with the damage caused by the previous layer of scratches – that is not the problem here just polish to a higher finish). The diamond pastes that we generally used were 5or6 micron and then 1 micron – after that we went to an alumina slurry if we really wanted to impress! The issue here is just move up to the next finer grit size and polish a little more until you get to your strop. Don’t dwell too long on each grit size – only enough to remove the scratches from the previous grit. I wouldn’t ever use 600 grit size on a strop -it just beds into the strop (thus reducing the effective particle size) – just use the rouge or whatever polishing compound that you find works.
Be careful of conversions between “grit” size and microns – they may not be equal and each of the grits and micron sizes is actually a particle size distribution centred on the grit size(skewed but a distribution nevertheless).
@kodi I can only give you an indication of what Silicon Carbide papers that I am using – and that is Norton (Saint Gobain). I think that this is widely available, reasonably long lasting and good quality. I have also used 3M carbide paper. I only buy what I need – a few sheets at a time in a variety of grits so that I don’t have to spend too much time on each. I have a few 10mm (approx) thick glass plates (the size of 1/3rd carbide paper sheet) to use as a flat surface for each grit. As a young Met I was using the US Buehler and European Struers consumables, but they were shockingly expensive and I wasn’t the one who had to pick up the tab for them! They were great for scientific work and metallography. Whatever you buy, keep clear of the very cheap offerings. When you are trying some sheets, bend the sheet gradually towards a fold and watch how the binder and the grit separate from the backing sheet. An indicator of quality. Try different brands if they are available and note down which ones perform for you. Quality brands will have tighter particle size distributions.
You can’t sharpen knives edge first on carbide papers – just like stropping them! You will have to accept trailing your edges.
Again I’m not sure what the 250 means – you can’t directly and easily convert grit sizes and micron particle size although there are some conversion charts available US grit sizes differ from European P grits – just can’t lay my hands on them at the moment
I hope that that helps and that I have answered most of your questions.
Cheers
Mark H -
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