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  • #46
    I've done very little in the way of scraping, but I follow all this as it's interesting- and I learn too. What comes to mind at the moment is the nature of lubrication. From watching Dan Gelbarts videos, in one he shows lapping and scraping, and also talks about the nature of 'flat' surfaces. If two surfaces are truly flat, then they will form a hydrodynamic bearing using whatever material might be between them. He demonstrates an air bearing using his granites, and I'm sure most of us have experienced the feel of that sudden reduction of friction when you move one flat object over another. Air is the bearing material in this case.

    But I'm sidetracking. Dan says that when surfaces are flat enough, the lubricant stays in place and keeps the flats apart. This seems to be at odds with frosting for oil retention.
    I seldom do anything within the scope of logical reason and calculated cost/benefit, etc- I'm following my passion-

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    • #47
      Originally posted by darryl View Post
      I've done very little in the way of scraping, but I follow all this as it's interesting- and I learn too. What comes to mind at the moment is the nature of lubrication. From watching Dan Gelbarts videos, in one he shows lapping and scraping, and also talks about the nature of 'flat' surfaces. If two surfaces are truly flat, then they will form a hydrodynamic bearing using whatever material might be between them. He demonstrates an air bearing using his granites, and I'm sure most of us have experienced the feel of that sudden reduction of friction when you move one flat object over another. Air is the bearing material in this case.

      But I'm sidetracking. Dan says that when surfaces are flat enough, the lubricant stays in place and keeps the flats apart. This seems to be at odds with frosting for oil retention.
      One difference between Gelbart's use of granite flats and scraped machine tool surfaces is smoothness. A scraped surface isn't necessarily smooth but all the little plateaus over the surface are the same height withing a very small range, tenths to millionths. However, the valleys between provide a way for oil to migrate out. With moving machine parts they also serve as reservoirs of oil that's dragged in between opposing plateaus by fluid friction.

      I can't speak to Gelbart's machines never losing the air between surfaces since I haven't watched all his videos and the ones I have seen weren't recently. I'd only bring up a counter example of gauge blocks which are very very flat over their small area and can come into close enough proximity that they WILL stick together rather than maintaining a separation. My impression was that Gelbart did introduce pressurized air, at least into the air bearing spindle so perhaps I just assumed the way surfaces as well.

      In any case, it is machine tool users' experience that not lubricating sliding surfaces and expecting air to keep them separated does not work. They see wear and scoring before long.
      .
      "People will occasionally stumble over the truth, but most of the time they will pick themselves up and carry on" : Winston Churchill

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      • #48
        Also, in good quality woodworking, you get a thin even glue joint by rubbing the two boards together, which drives out most of the glue, until it is basically wood-to-wood on the higher spots, with the glue remaining in the lower spots, and the thinnest film on the high places. If you rub too long, the glue rubs right off the high spots.

        The material between WILL get rubbed out of the space between if you move the two back and forth. It's dragged one way, and then the other, each time plowing off some, and not returning 100% of it on the return stroke.

        Scraped surfaces seem to move better on each other when there is NOT pumped oil into the bearing area. With pumped oil, it doesn't matter, ground is fine. Many lathes pump oil under the carriage as it is moved.
        CNC machines only go through the motions

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        • #49
          Got a chance to do more work on the Benchmaster. Pulled the knee, because while I thought I had scraped the dovetails, in fact I had not done so.

          Side #1 making progress, about time to let it be and adjust at final alignment. This is the side the saddle contacts.




          Side #2, not so hot, needs work. This is the side the gib of the saddle rides on, so being apparently worn toward the middle of the travel makes lots of sense, that is where the screws are.




          After some work, starting to come in better.

          CNC machines only go through the motions

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          • #50
            More progress, coming in a bit more.



            Even better, might want to stop here and start checking alignments before trying tp refine it too much



            The tool used on dovetails



            The end is about 25mm wide, with the top surface ground back at a sharpish angle to fit down to the bottom of a dovetail such as these. Bottom bit is ground to the usual 5 degree negative rake used for general scraping of cast iton
            CNC machines only go through the motions

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            • #51
              Too hot out to mess with anything more than just watering everything in the yard that is not actually in the ground (we have lots of things in pots, from stuff that is going to leave at next year's sale, to orange and coffee trees, and some kitchen garden things growing in sheep tanks in a cage where the squirrels cannot get to them.

              So I decided to hit the shop again, because it is nice and cool down there.

              Checking the alignment of the two sides of the dovetail on the knee (they were nearly perfect)



              As I remembered, just needs a bit of refinement and it is good to go.

              Last edited by J Tiers; 07-19-2019, 05:53 PM.
              CNC machines only go through the motions

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              • #52
                As is usual, this project got set aside in favor of more pressing things, and being lazy, and stuff I wanted to do, and all the summertime stuff, and repairing engines, etc, etc. I did work on it from time to time, but no consistent work. Was busy from January to June, then the usual summer stuff this crazy year, and finally got back on it.

                Some random pics.... I did not take many during the on again off again work being done

                Checking alignments of the knee to the column




                A view of the scraped saddle. It was a nuisance to scrape, I did the knee interface, then the table side of it, finishing the horizontal, but only roughing the dovetail part to wait for the table.



                Started with the top of the table, here is a pic partway through.....

                CNC machines only go through the motions

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                • #53
                  Next I did the table horizontal way surfaces, then the dovetails. Here is one



                  I decided to scrape the front t-slotted surface to line up with the other t-slots, and then scraped the dovetails to align with the front. When completed, the table now has the front surface, the dovetails, and the t-slots all aligned, so hopefully I can lay a shaft in any t-slot to align it for cutting a keyway. The "Kingway tool " copy that I made years ago came in very handy for this.

                  The table had another problem. The crank was on the wrong end. There were alignment pins on both ends to put the crank plate either place, but the end I wanted had had the pins cut off. After wondering how to pull them, I finally decided to drill them out, but tried knocking them in a bit to help get a drill centered on them.

                  They ended up going in far enough that I did not need to do any drilling, I just put new pins on top of them. So I have pins in both ends. That's fine, since I will probably put a table drive system on the machine, so the alignment pins at the far end will be useful.

                  The holes after knocking back the existing cut off pins



                  The new pins



                  The plate going onto the new pins





                  Last edited by J Tiers; 12-23-2020, 01:44 AM.
                  CNC machines only go through the motions

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                  • #54
                    So it was time to put the knee onto the column and start assembly.

                    First, the knee had to be put on with the gear going on the lift screw as the knee is lowered down. Then the taper pin goes in to hold it.



                    At that point the knee was ready to receive more parts. But I decided the oiling was no adequate, so I first installed a thrust bearing between the screw collar and the casting, then also installed an oiler in a drilled hole to oil the main bearing, which is a plain journal, steel on cast iron. The oiler is right above the screw in the second pic below. I also installed the dial and crank along with the screw and saddle nut. The added thrust bearing required trimming the dial slightly to fit, due to the screw setting inward 1/16" farther than normal since the new bearing is on the inside.

                    The oiler will be cleared by the saddle because it is in a recess between the way surfaces.

                    The table raising gears really need a cover. That may get done before any more work, if it will clear the saddle feed nut. That looks close. And there may be some oiling arrangements needed.







                    At that point it was quitting time.
                    Last edited by J Tiers; 12-23-2020, 02:18 AM.
                    CNC machines only go through the motions

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                    • #55
                      The thought has come to me that since I have the thing apart, this is the time to work out a good overall oiling system. I am not going to do any sort of one-shot, but it would be good to have a positive way of oiling the major table slides. The column can be done by direct oiling

                      It appears the table may be drilled from the top to provide oiling holes for both front and rear slides, and the feedscrews, with the feedscrews by drip, and the slides by direct oiling into a felt reservoir.. Three may do it, filled with setscrews, and marked as "oil". One feedscrew could be done by oiling through the feed nut, but that might require another oil hole.

                      The holes could be from the surface, which is a pain one way, but good as far as access. They could be in the bottom of the t-slots, which is bad for access, but has no effect on the table top. I am leaning to the idea of the top, though, easy access and cleaning means probably better and more frequent oiling.

                      I'd do side holes, if I could find a place for the back side hole. The other issue is that I wanted to do a felt wick reservoir, and that is harder going horizontal than vertically down. The other carriage slides will likely be by side holes, since there is no top access.

                      The best place for the top holes is in the middle of the table length. Most accessible places for rear-side holes are outside of the saddle/carriage when they are accessible, so the oil would just drop to the base. Use of right angle oilers would restrict table movement because they stick out a long way.
                      Last edited by J Tiers; 12-23-2020, 08:11 PM. Reason: added details
                      CNC machines only go through the motions

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                      • #56
                        So, I made some decisions, and did some work.

                        Decision 1: The Y feedscrew can be lubed when it is exposed with saddle in or out all the way. So no provisions have to be made for that. I can always revisit that.

                        Decision 2: oiling the Y ways can be done from the sides, and drilling the oil passages is not a big deal

                        So I did those things.... I did NOT do anything special about the Y feedscrew, I just lubed it. And I drilled the oil passages, installed ball oilers, then installed the saddle. I will probably take it off again later when I decide about a backside shield, and decide how wide the oil distributor on the way should be.

                        Here is a view of the whole thing as of now. The knee is all the way down, and there is rather a lot of distance that a sheet of rubber attached to the saddle and the column would have to cover. I don't know where all that rubber would go when the knee is all the way up and the table is moved back toward the column. So that is for later.



                        And, here is a close-up of the saddle, showing two setscrews that are loctited in position (to seal them). One is just in front of the end of the leftmost blue line, and the other just in front of the X axis nut. (The blue lines are left over from step-scraping the saddle, used to separate the "steps".)

                        The left one is an inch and a half in from the left side, the other an inch in from the right side, putting each about in the middle of the way. I will extend a groove to the side so that the dovetails get oil also, when I take off the saddle later.

                        What I did was to drill 0.060 holes in from the ends, then drilled through top to bottom with a tapping hole for 6-32 to connect with those first holes. The exits on the slideways were chamfered. The top side half of each hole was tapped, and the holes were enlarged on the sides to fit a 3/16" ball oiler. After the swarf was cleared out, the setscrews were put in place to seal the top, and the ball oilers were installed.

                        After the saddle was installed, I pumped oil in, and it spread out well. It will need the oil grooves to let some get to the dovetails.



                        The ball oilers. They will be accessible to my "oiling spear" oil can that is used for way oil, when the table is run to the right.




                        Tomorrow I will work on figuring a way to oil the table ways. I will also have to order more ball oilers, since all I have left are flip top types in stock.

                        I notice that the unit would not be the worse for some paint. That might get done, depending.



                        Last edited by J Tiers; 12-24-2020, 12:41 AM. Reason: Fixing fat-fingered typing
                        CNC machines only go through the motions

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                        • #57
                          Nice work on this, Jerry. Looks a lot like the one on Tony's site @ http://www.lathes.co.uk/duro/page2.html.

                          When completed, you will have a more comprehensive understanding of all the little plusses and minuses this machine may have, and put it to good use making chips.

                          Dan
                          Salem, Oregon

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                          • #58
                            It is essentially that same version, yes. But that is probably a bit different time period. I don't know if the cranks came before or after the handwheels*. This one has cranks, and zamak dials, the one in the pics has steel dials and full handwheels. The zamak sounds like a later cost-saving method.

                            Interestingly, I see that while on mine, someone cut off the locating pins at one end of the table, on the site's version, someone cut off the SCREWS, and left the locating pin holes open.....

                            As for Benchmaster mills....

                            Pluses.... I have this one....

                            I got it for $150
                            I paid 5 bucks (!) for the vertical head, later, so I don't have much in it.
                            The other mill has a vertical head, but is a much better horizontal, and I wanted a vertical mill.
                            The table has more t-slots than the other one which has just a single central slot (very much of a hassle)


                            Minuses..... nearly everything else.

                            It's made cheap everywhere... About the only differences between it and something made in china or india is that the feedscrew bearings, while they are direct steel on cast iron, have the steel parts well-finished, instead of rough as a cob, the cast iron is decent quality, and the bearings for both spindles are good quality, surplus from WW2.

                            No provision for oiling anything, everything assembled with pins to hold it, I doubt it was scraped OR ground as to the ways, originally. The best characterization would be that it is built like a low-end drill press in most ways, even to the MT2 taper on the spindle.

                            As a horizontal mill, which I have all the parts for, it is a 98 lb weakling, with an overarm support that is slightly ridiculous. I do not plan to ever operate it as a horizontal, but at least I "could".

                            And, finally, the vertical head is the size of west Kansas, and the cutter is right under it, so visibility is "less than ideal". If the pulley had been designed-in upside down from how it is, that would have been superior.

                            But it is MY pig, and if I let it use lipstick, well, that's my problem!


                            * I see that Tony's site says the handwheels were later, and presumably the steel dials are as well.

                            .
                            Last edited by J Tiers; 12-24-2020, 01:07 PM. Reason: added handwheel and dial info
                            CNC machines only go through the motions

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                            • #59
                              Todays (Thursday's) progress was limited to making and installing the handle on the left, which I flatter myself is comparable to that on the right. The handles rotate freely, and are held in place by pegs driven into holes in the crank arm, which pass through a groove in the stem of the handle, locking it n place, but allowing it to rotate. One was missing, and now that lack has been fixed. You can see the peg holes in the arms at the base of the handles.

                              CNC machines only go through the motions

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                              • #60
                                Did nothing in the shop or on the computer on Christmas day. Just recently had a look at the Benchmaster and decided I should pull and clean the vertical adjusting crank, shaft, and gear. I had not done it yet, and I need to before I do any more elsewhere.

                                The problems of doing a project in small steps separated n time by months. I should keep a log, with a list of things to be done. But I think I looked at it, and I seem to remember that there was something I could not get apart, maybe there was a taper pin that would not come out. Tomorrow (actually now it is today) I will look into that.

                                I also decided that the cranks shown in the post previous to this are so rough and nasty that they need to be introduced to the belt sander and the Cubitron belt. The pic makes them look like they were flame cut, and used as-is after that. (They actually are cast parts)
                                CNC machines only go through the motions

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