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| PekkaNF:
Really like this thread and YT videos. Very educational and nicely edited. I am building up tooling to start some scraping projects too. I have some questions. 1: How do you hold down the parts when you scrape dovetails? 2: I think I saw a dove tail scraper (Sandvik handle? Dapra scraper?) in some picures. Any pictires and advice on dovetail scrapers? Thank you, Pekka |
| philf:
Hi Andrew, This is quite inspiring but I don't know if I have the patience! My Capco is all stripped down, 5 layers of paint removed and in grey primer. I have the knee sat on my milling table and with an 8" square I can see 0.3mm wear in the Z-axis! Too much to scrape I think so I'm wondering how I can machine it on my mill which is really too small. I'm currently thinking I can clamp the knee flat to the table and spin the head through 90 degrees. I'm not sure how much the dovetail is worn or if it's just the face. Looking at your method I would need to get the face perpendicular again before testing the dovetail. I have a 55 degree dovetail cutter but the face width isn't enough to re-machine the dovetail in one go - it's about 21 mm. I have a good reference face to the lhs where the 4 tapped holes are. This is for a block gib so sees no wear. You can almost see the shadow created by the 0.3mm step at the top. (Very little wear at the bottom.) Phil. |
| Andrew Wildman:
Pekka, I just stood the table on the 'workmate' (this is a diy type trestle table that has a clamp action top) and clamped it lightly. this was more than sufficient for the light loads from scraping a dovetail. I have a sandvik scraper and the standard sandvik blade for roughing. For finishing and dovetails I clamp a carbide paint scraper blade that i have dressed the end up of. This holds up as well as the sandvik blade and cost me about £1 rather than the £15 for a proper sandvik one. :D --- Quote from: PekkaNF on August 12, 2017, 01:13:50 PM ---Really like this thread and YT videos. Very educational and nicely edited. I am building up tooling to start some scraping projects too. I have some questions. 1: How do you hold down the parts when you scrape dovetails? 2: I think I saw a dove tail scraper (Sandvik handle? Dapra scraper?) in some picures. Any pictires and advice on dovetail scrapers? Thank you, Pekka --- End quote --- |
| Andrew Wildman:
Phil I suspect if you have that amount of wear on the knee then the column face and definitely the column dovetails also have some serious wear, as obviously they are both made of the same material. If you set the gibs to allow free movement along the whole length of the knee is the knee loose at the most work point? Would give you an indication if you column needed work to make the grinder serviceable. You could scrape the column in a similar manner to me, even if your plate was not as big, but you had a precision level to ensure that each of the smaller scraped sections were in the same plane. This would then allow you to scrape the knee too it. You might want to take most of the material off in the mill to save your time and your mind! :bang: your solution looks the best way to do this. BTW your knee is a bit different to mine as mine has a oiler and double vee ways for the carriage (aligning these is a headache that I am now solving!) --- Quote from: philf on August 12, 2017, 03:28:20 PM ---Hi Andrew, This is quite inspiring but I don't know if I have the patience! My Capco is all stripped down, 5 layers of paint removed and in grey primer. I have the knee sat on my milling table and with an 8" square I can see 0.3mm wear in the Z-axis! Too much to scrape I think so I'm wondering how I can machine it on my mill which is really too small. I'm currently thinking I can clamp the knee flat to the table and spin the head through 90 degrees. I'm not sure how much the dovetail is worn or if it's just the face. Looking at your method I would need to get the face perpendicular again before testing the dovetail. I have a 55 degree dovetail cutter but the face width isn't enough to re-machine the dovetail in one go - it's about 21 mm. I have a good reference face to the lhs where the 4 tapped holes are. This is for a block gib so sees no wear. You can almost see the shadow created by the 0.3mm step at the top. (Very little wear at the bottom.) Phil. --- End quote --- |
| philf:
Hi Andrew, I thought I'd fix the knee first before testing the column. The dovetail currently flat on the mill table might be OK as there isn't a cantilever effect like on the knee. Having said that the z leadscrew is in the centre so it's hard to imagine why there's so much wear. All the oiling points on the machine were clogged with grease which probably couldn't reach where it needed to be. Rather than trying to clean the nipples out I ordered a batch of new ones. There doesn't appear to be any provision for lubing the z-axis! I think the most critical axis is the x-axis which needs to travel in a straight line. It doesn't matter if it's not perpendicular to the z axis. Similarly the Y axis - if it's a touch out of perpendicular to the Z axis then when the wheel is dressed it will be parallel with this axis. The grinder doesn't owe me much and I'm in no great hurry. Like Pekka I was going to ask what sort of tool you used to scrape the dovetails - a photo would be nice. Cheers. Phil. |
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