Part 1 - Building the bed and ways
Tuesday, 7 June 2005
When you read this book, you will discover that is is broken down into chapters. The first chapter gears you us to get started. It gives you a brief history of the lathe and explains some of the techniques that you will be using to build the project. The next chapter talks about foundry work and pattern building. Finally you get to chapter three where you start the project by building the lathe bed, feet and install the bed ways.
The first thing you have top do is build the patterns that are going to be used to cast the bed and the mounting feet. These are simple enough to make. I learned a couple of things in the process. I used 1/4" plywood to make my patterns. Plywood is not the best material to use when it is so thin. It warps easily. If I ever make another, I think I will use 3/8" stock of either plywood or clear pine. I think that the heavier casting will be less apt to warp. Below is a picture of the two patterns I made for the lathe bed and mounting feet. (Unlike most of the images on my website, I am using a larger version of the images. You can click the image to get a bigger version yet.)
Once the patterns are made they can be cast. Molding these things was a real challenge for me. Both these pattern require a double roll and leave a sand core in the drag half of the flask. This core creates the hollow part of the foot and bed. My problem was that when I opened the mold and tried to lift the pattern off of the core, I would break the core. It took about four tries to mold the bed pattern without breaking the one or more of the core prints off. Finally, I rammed the core prints a little lighter and I was able to pull the pattern off them without breaking them. Below is a picture of the two feet that I cast.
These cast fairly good the first go. You can see on top where I cut the sprue off and drilled a hole to mount it to the bed. (This part of my lathe was already together before I decided to post it. I put it together to keep from losing the parts while I moved from Illinois to Tennessee.) The only other thing that I done was to mount the feet on the faceplate of my Craftsman lathe to face them off. As cast the bottom of the feet bowed upwards and did not sit well on a flat surface. I filed most of it off, then decided to try out my lathe. I figured the worse I could do was mess it up and if I did, I had the pattern and the foundry to make more of them. Casting the bed was more of a challenge to me than the feet. First of all the bed had four cores to worry about breaking off while the foot pattern only had one. Below is a picture of the cast bed.
I had real issues trying to get the bed cast. First with breaking the cores when I molded it, then after that with it bowing when I cast it. After the third cast I said to heck with it and used it anyway. You can see that the center of the bed is less than perfect. This is because when I rapped the pattern to remove it from the mold, some of the sand broke away. I laid a piece of sandpaper (rather a strip about 3 feet long) on my workbench and sanded the top down until it was mostly flat. If you seen the side profile of the bed, You can see where it bows up. Some due to me rapping that pattern too hard to remove it from the sand and some of the bow I suspect is just from the shrinking of the casting itself.
Monday, 04 December 2006
Wow, 18 months have passed since I have done anything with the lathe project and this page. But I have not forgotten about it. I have been doing other projects during that time. I still have a LOT of things demanding my time, but for the moment I have a little time to spend with the project. It is dark and too cold to work on the workshop. But I digress ...
When I last left the project, I had sanded the bed casting a little flatter than what it started out with from when it was shook from the sand. I done this by laying a strip of course sand paper about three feet long on my workbench and sanding the casting until it looked like most of the surface was sanded smooth. Now, that does not mean it was flat, flat would require scraping the casting to some standard. Well Dave suggests that we use the cold rolled steel as a flat testing standard. The process as Dave explains it is very simple. Coat the bed with a thin coat of oil paint, rub the test standard on the casting and then look for the spots that the paint was rubbed off. Take your scraper and scrape these spots. Apply new paint and repeat the procedure until you have at least 75% contact between the test standard and the bed casting. (Yeah Dave, that sure is simple to someone who never heard of scraping anything before) ;-)
SCRAPING - The tools of the trade.
So how do you scrape, and what do you need. Well Dave gives a pretty good explanation on how to scrape but I thought I would give my $0.02 worth of advice. In the picture to the right you see my tools for scraping. A tube of blue oil paint I bought from Walmart, and oil stone and a file. The file has been ground smooth on the end of the face and the end had been ground to a gentle arc. There is a few great articles on scraping at the scraping forum Yahoo group and I have those documents as well. I will try to post them for you to have if you want them. Scrapers can be ground and shaped to most any shape you need for the job, but this seems to work OK for what I am trying to do. Also, It is important to keep the scraper as sharp as you can get it. It will allow you to make finer cuts and control the cut much better than when it is dull. Dave instructs us to apply a thin coat of paint to the bed, rub the steel ways against it and then scrape those areas that the paint has been rubbed off. Well I done that, but to me, the spots were hard to see and I found myself constantly looking at the bed casting at an angle to the light to see the bright spots of aluminum showing through the paint. The paint is applied in a thin coat so it looked a little metallic to me as well. Long story short, I think it made the job even harder to do that it should be. My solution was to apply the paint to the cold rolled bed ways, and then rub them against the bed casting and scrape the paint spots left on the casting off with the scraper.
Here you see the bed during the scraping process. I have been scraping on the bed casting a while now, and at first with varying amounts of success. When I first started it seemed like my indicator was moving around. In other words the spots of blue paint that were left on the casting were moving around instead of getting bigger or more spots. Well, I suspect my problem was that I was cutting off too much material and just left more dips and new high spots. I put the bed aside and decided I need to practice on something I could screw up. I took an ingot from the stockpile I had and started on it. I filed the bottom of the ingot as smooth and flat as I could get it, then smeared my plate glass surface plate with a thin coat of paint and applied the ingot face to it. Here is what I learned and maybe it will help you. The scraper should be as sharp as you can get it, and resharpen it often. The angle of the cutting tooth of the shaper will determine the depth of the cut. When you first start you will only have a few high spots, I scraped mine with the scraper held at a higher angle to get a deeper cut and scraped the area that had paint plus a little around it. As you continue the process you will get more spots of paint on the casting and larger spots. Start taking finer cuts. Also, just like a file, cut on the forward stroke and lift the tool slightly on the return stroke. Otherwise, I have noticed that you will grab bits of aluminum with the scraper and it will dig in like what can happen when you file aluminum. Take your time and don't get into a hurry. Just plan on spending a LOT of time with this casting to get it scraped flat. If you look at the photo I posted you will see that I am near 50% contact. Only 25% more to go and I can install the ways on the bed, well after I scrape the back side of the ways flat. I think because I have such a bad spot in the middle of the casting I will shoot for 80% or more contact on the bed, or whatever it takes to get an ample amount of contact around the center of the bed where the sprue was.
Some thoughts about the project so far.
If you have the whole series of books from Dave on building a metal shop from scrap, you will notice that as he goes along, some of his processes change and get better. A case in point for the lathe would be the bed pattern. When dave gets to the Miller, the bed is made of heavier material and is not solid on the top. Additionally, the ways are attached with two rows of screws rather than a single row in the center. The benefit from these changes is that the ways and bed become more rigid because of the structural thickness and more screws holding the thing together, and the next great benefit is that there is only a small area to scrape flat compared to the bed casting of the lathe. The less time you spend scraping the more energy you can put into other parts of the project. These suggestions have been made as well as many others regarding the Gingery projects on the Gingery group on Yahoo. If you are not a member and plan on building any of these projects, I would suggest you join the group, it is free and there are a lot of helpful people there that can help when you get stuck, share information about upgrades to the equipment and tell you what some of the weak points are. Now, I intend to build the project as laid out, but if I were to do the bed again, I would go with something like that on the milling machine. Till next time, happy casting and building!
Sunday, 14 January 2007
SCRAPING, what more can I say. It turns out that there is a bit of skill that goes into the process and a few variables. Your gauging standard, your tools and your technique in applying the tool to the work piece all affect the outcome. I have been struggling trying to get the technique down so that I can progress with the project. I scraped and scraped and didn't seem to be getting anywhere very fast, so I decided to ask around on the Gingery Forum to see if some help was available. First of all, I cannot say enough kind things about these folks. They are there to help each other and you too. If you have a question about your Gingery project, ask there. You will surely get an answer and extra information to boot. My question to the group was basically their scraping experience to see if I could get past the problems I was having. Soon enough I had a lot of resources to look at and plenty of extra tidbits of knowledge to file away. One thing that came up was the testing standard. The conversation ebbed and flowed about this for a bit. I ask about using the cold rolled metal as a testing surface and was asked in return about how flat was the cold rolled steel. Fair enough I thought. Well after chewing on that question a bit, there is no real reason to believe that the steel is flat at all. Now I think Gingery was correct in saying that the thickness is accurate within a couple of, or a few thousands of an inch, but could I detect a slight bow or twist in it? Well the truth of the matter is, it may be straight and flat, it may not be. So I started asking about what standard to use. There are a number of options. Here are the ones that make the most sense to me. (1) Use an existing milled surface like a table saw or other steel surface that has been milled down. (2) Use rather thick plate glass that has been lapped together. I would recommend at least 1/2 inch but thicker would probably be better. (3) Get a surface plate. These are not too expensive as far as buying the plate goes, but shipping will eat you alive. It was suggested that you could use a granite tile or counter top too, but I don't know.
Now I am back to scraping. I ordered an 12 x 18 surface plate from ENCO and with the free shipping offer they had made it a good deal. In the mean time I used the milled surface of my table saw as the test standard. I immediately noticed a different pattern of high spots. Seems like the surface of my table saw and the surface of the cold rolled plate were not the same. Additionally, the group taught me a few things about the indicator. (1) During the start of the project, use a heavier coat of indicator when you start to scrape. Scrape the high spots aggressively. When you have a lot of surface area being indicated like the image above, you need to start using thinner coats of paint. You will discover that your high spots are spread apart and your scraping should be lighter so as not to remove as much material. (3) As you near the end of the scraping task, you will have more and more high spots, grouped closer together. At this point you want a very thin layer of paint and only gentle pressure applied to the plate so that you are picking up only the high spots. Keep working these down until you have several spots per square inch of surface area. The more spots the better and the remaining low spots will hold oil.
Here is the surface plate as I received it from ENCO. It came in good shape save for a dinged corner. But that will not affect the use of the plate. Now the plate that I bought was 12 x 18 and as you know the bed is 24 inches long. So to get as much use of the plate as possible, I painted my indicator from one corner to the opposing corner across the plate. I rubbed my bed a few strokes across it and the results were nothing that I expected at all. What is seen on the bed casting were some high spots near the ends and a few inches from each end. That confused me a bit, but I thought that the plate must know. By the way, I received a certificate with the plate giving its inspection date and its government compliance and its actual flatness. The paper said that it was flat to a tolerance of +/- .000050. Man that sure seems flat to me. Well, I started scraping and retesting. I had nearly the same results on the bed with the indicator. So I scraped and tested again, and again, and again, and again. The more I scraped the more story the process told me.
Now I suggest you click on the picture of the bed and give a good long careful look at it. Here is what I take on it. You notice that there is indicator on both ends and none in the middle. As I watched the indicator grow on the bed from each scraping that the bed is bowed from end to end. A close look will show you heavier indicator on the ends and as you move towards the center of the casting the indicator gets lighter. Well, I must be getting somewhere because more and more is starting to show up where it wasn't before. The bed is bowed for a couple of reasons. (1) The center of the bed is cast with a pop gate, you are supposed to rap this srpue before you open the mold. Truth be told, I rapped too hard and caused the pattern to flex and bow which shows up very clearly at the bottom of the casting. (2) The top of the bed is solid while the bottom is hollow. As the casting cools and the metal shrinks, it makes sense that the bed should or would bow as it cooled. Maybe a heavier section thickness would have kept it to a minimum. I really don't know. Maybe someone could expand on that sometime for me. The next thing you notice is that there is more indicator on the bottom left and top right of the casting. I take from this that the bed is twisted as well. Now as I set the bed on the surface plate I cannot detect any wobble that would indicate that the bed is not making contact with the plate. I will continue to scrape this casting to see where I can go with it. I am hoping that the indicator will slowly start to show up closer and closer to the center of the casting and at the same time start showing me a balance of indicator on what would be the front and back of the casting. I am going to continue to use a good coat of indicator on the surface plate until I get what appears a reasonable flat casting, then will start using lighter coats of indicator on the stone to show me the real high spots.
I will post my progress as soon as I can show some. For those of you that have not scraped yet, you are in for a treat. Gingery says that it is tedious to do, and well, he didn't lie to us. It must be the longest, most boring task I have ever set myself to do. But hey, I am not going to give up. I want to say someday, LOOK, I WON!!! HEHEHE Thanks for your support and check back once in a while to see where I am at with it. If you have questions, feel free to email me and I will answer them the best I can. HAPPY CASTING!
Wednesday 17 January 2007
Well I have sent quite a few emails back and forth with the Gingery Machines group on Yahoo. Lots of great advice and information was taken in. As a result, I created a resource section to the lathe. Be sure to check it out.
One thing in particular was a bit of advice I got from Mr. Williams. As you see the lathe bed is bowed and twisted as it stands. Mr. Williams suggested that I lay the casting on the surface plate and see how much bow there was. Then indicate and grind it off. Here is part of his comments to me on the group.
Joe, this might be illuminating: Some years ago a friend showed up with a 1968 Chevy 6 cylinder exhaust manifold. It was severely warped into a bow and he asked me to mill it flat. Putting it on my big surface table it was clearly .160" = 4 mm out of plane. As I puzzled how to hold it I decided to just take the high spots off with a disc grinder. Rechecking it showed it had gotten so much flatter I took another pass with the grinder, then progressing from the grinder to a coarse file to a finer file in about 30 minutes left me at a maximum bow of .002" = .05mm in less time than it would have taken to secure it to the mill table!
Bill in Boulder, "Engineering as an Art Form!"
Well, I used a heavy coat of paint on the surface plate and slid the casting across it marking the ends of the casting. I took my die grinder and ground the paint off the casting. I had to repeat this about four or five times until I had indicator showing across the whole casting. So at this point, I think the casting is flat enough to start working. The next trip into the garage, I plan on indicating and draw filing with a course file to get the casting cut down to something closer to flat. Eventually, I will start scraping on it. After my next session, I will try to post a picture for you all to see.
Tuesday 23 January 2007
I have managed to get a little more time here and there to work on the lathe bed. I did not draw file it before starting to scrape because I didn't have a good file to do the work with. So I set out to scraping. I wish I would have taken a photo of the bed as it looked after the grinding session, but as they say hind sight is 20/20. One thing about aluminum is that you have to be light on the touch if you grind the stuff. It does not take much pressure to take a lot of material off the surface. The result was I had quite a few grinder marks on the casting to contend with as well. Fortunately, as I went along the marks were getting less visible and starting showing more and more indicator. The photo you see here is after the 9th scraping and after the 12th scraping. If you click on the image you will get a better view of it. If you look close you will see that there are more areas of the casting starting to come into contact with the plate. The amount of indicator will change the results slightly from scraping to scraping. I try to use the same amount of indicator on my surface plate with each application. Keep in mind that I am using too much indicator for a fine job. As more of the surface of the casting is indicated, I will start using a thinner coat of indicator on the stone and taking lighter cuts from the casting. Dave tells us that we should have at least 75% contact with the ways that are to be bolted in place. I am still a good ways off from that mark. I will keep plugging at it. One thing for sure, I don't like scraping. This must be the worse task I have ever set myself to. BUT, I know that if I keep at it, I will be alleviated of it someday, or at least less of it. Check back once in a while, as I make progress I will post it. In the mean time, HAPPY CASTING!