As always Jan I'm very thankful your willing to detail and document your procedures. It's a fantastic resource that explains some of where the Connelly book may have been a bit less than well explained. I suspect the factory either didn't do the greatest precision alignment on that column foot, or they purposely misaligned it in an effort to help compensate for the head weight flexing the column forward. The friend your doing this work for may want to consider building a proper temporary dam for the Z axis feed screw and it's feed nut and then casting an epoxy / granite mix for the rest of the columns internals. That might help quite a bit to prevent that probably unavoidable column flex. Compared to my Bridgeport clone and it's 3 point support of the knee, that's a fairly long and light weight casting with a lot of head weight cantilevered out from the column. I would think with that head weight it would be fairly easy to see a considerable amount of deflection of that column depending on where the head is positioned on those vertical ways.
A quick n dirty calculation shows around 0.02mm per 100kg so not super problematic. Some people proposed that it's actually the base buckling which makes sense to me as it is even flimsier than the column and a small deflection there translates to a big deflection at the spindle because of the lever. Would be very interesting to see some measurements before and after epoxy granite filling. There are a few people on RU-vid who have done it but i don't think anyone ever showed the improvement.
You're welcome. Thanks also for commenting. I think my friend made the same measurement, but with the head mounted, meaning that the situation already was present then. It would anyhow present a problem I guess if the column tilt/head weight compensates one another for alignment purposes to this degree. The high in the middle/less contact area situation is not ideal as it really lowers the stability and probably limit the depth of cut you could take. You could make the column tilt by tightening the screws around this "central pivot point", but it would be better then to actually scrape it flat to have 2 mating surfaces with the usual properties, but at the desired tilt you may want to induce. The whole design has it's limitations of course and I reckon it is not ideal for heavy milling anyway, but I am also confident that the better the base-to-column contact gets the more this would transfer to improved cutting results. Yes, I have seen several that have improved their column in the way you suggest, and I will suggest this. Could also gain from having the column anchored at the top I guess. The B'port is a much better thought out design and made to higher standards.. but at a premium price compared to this mill-drill (and a host of similar types). That said, It is not a bad machine, especially considering the (relative) low-price. You just have to factor in this when you buy and don't expect it to be more than it is..
Thanks for uploading this really interesting video Jan. Out of interest, could you please explain how you ensure the ways are at the same heights in relation to the column? The dial indicator would show parallelism but I'm not sure how you would measure the height. Is it the case of using a depth micrometer from the upper surface on each side or just measuring from the surface plate to each side? Thanks, Morgan
Thnks for commenting. Which part of the column do you mean? The top of the dovetails are no-contact areas, and the flat ways are plane-parallel to the angled dovetails (checked by the micrometer- and indicator readings), and then these 4 flats are aligned at right angle in tbe 2 planes to the base. That said, I have also tried to get these top (no contact) surfaces as good as possible (aligned to the way surfaces) for possible use as "reference" . There are also 2 narrow flats on the upper edges that are tested and will prove as useful references when measuring sideways tilt
@@jansverrehaugjord9934 Thanks for getting back to me. It was the flat ways I was thinking of, although they are parallel could there not be a difference in level in relation to each other ie. One could be lower or higher than the other (looking axially along the column)? I was just wondering how this is checked as I'd like to attempt some scraping of my own. Many thanks, Morgan
@@TheOnlyMosesMalone Aha! I see.. yes, true. As you say, you should be able to detect this if you rest the ways dow to the plate and measure the height at each side
@@TheOnlyMosesMalone Thnks for this comment! It is usually not a big problem as far as I have experienced, but if sufficient will of course show up as an error when you try to mate the saddle onto the ways, and then would need to be corrected (possibly doing this on the shorter saddle, but as it would then be "out of true" with a surface plate test and these 2 parts only then match to one another.. not ideal. I will get back to this and include this explanation also to show this measurement 😀
Hello Jan, I enjoyed this video and the previous one... One question that came to me was regarding the difference between power scraping (Biax) and hand scraping. Is there any correlation between the two methods with regard to pressure applied, my thoughts are not as with the Biax some of your effort is used to manage the weight of the machine, where hand scrap the is no real weight. Take care. Paul,,
Thnks! As a rule, the BIAX being a power tool is used to facilitate the process of removing metal, and is used in industry to improve efficiency, ie. faster and easier vs. hand scraping. Therefore, as I am also taught and have experienced, it will remove more metal. However, I tend to lean more onto the hand scraper and therefore have a tendency to actually remove more material this way when roughing. That said, you don't last long hand scraping this way as it gets tiring after a while. This has an effect on scraping depth, which at least for finishing is not optimal. I therefore normally just take a few cycles with the hand scraper, but could of course also have used roughing techniques with the BIAX here also. I have learnt, and try my best to keep a constant scraping depth as this will also make it easier to predict things like how many strokes it will take for a certain operation. For consistent results I therefore favor the power scraper. It is advisable and indeed useful to find out just how much metal you remove with these different tools and with that knowledge apply this in the planning stage so that you can have a good understanding of the job at hand.
The medium sized BIAX (10 version) is a bit easier to use as it is not as heavy, although for my projects I cannot say it would matter much. Then the heavier (40 version) has the possibility for a longer travel, although this also don't matter much for the projects I am normally handling. I just happened to pick the medium sized now.. :) A flaker otoh is a totally different animal, purpose made for a different application, not to remove metal for alignment/regular scraping purposes, but to put on half-moon marks on top of an already finish-scraped surface.. for the purpose of having evenly distributed equal sized oil deposits, normally on the non-exposed ie. hidden side of a matching/mating pair of surfaces. While I am onto this.. in other words, not like you see they have done on the base of this milling machine.. namely having made an attempt to "beautify" the exposed surface (ie. the top side you can look down on).. so called eyewash.. not very evenly made and directly onto the milled quite rough surface. I could make a claim that this would even make it worse because you are actually taking away support points doing so (although the milled surface offers a less than optimal surface anyway), but worse so that the marks on an exposed surface will make grit and dirt stick better and probably make it easier for this to get under the way wipers (if such exist..)
