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Building the Trent Pinion Mill

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  • #16
    Drilled and tapped the holes for the gib screws, and have officially started scraping. I'm starting with the top and rear surfaces of the knee. I still have some to do on the top surface and then I'll need to get started on internals of the dovetails and the mating dovetail on the column. I think this will keep me busy for a while. I'm just glad it's small!




    Max
    http://joyofprecision.com/

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    • #17
      Originally posted by mars-red View Post
      Drilled and tapped the holes for the gib screws, and have officially started scraping.
      What are you doing your scraping with? I have been avoiding spending $90+ on a Sandvik scraper. I probably shouldn't admit it, but I've been using repurposed carbide inserts that I've slightly reshaped with a set of diamond wheels...

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      • #18
        Looking good Max. It looks like you scraped the top surface of the base. Did you scrape the bottom surface too? I see 4 mounting holes. Will you
        be bolting it down and if so will you scrape the surface you will be bolting it to?

        Originally posted by mars-red View Post
        Location: Long Island, N.Y.

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        • #19
          Originally posted by Dan_the_Chemist View Post
          What are you doing your scraping with? I have been avoiding spending $90+ on a Sandvik scraper. I probably shouldn't admit it, but I've been using repurposed carbide inserts that I've slightly reshaped with a set of diamond wheels...
          I have some carbide inserts that I don't have holders for that I've been thinking about using for exactly that. I personally don't like scraping with a perfectly flat edge, I prefer just the slightest radius, so I'd need the ability to grind carbide.

          In the past I've always ground old files to shape, to use as push scrapers. In preparation for this project, though, I decided to make and try a pull scraper. I liked it so much that it's my preference now. My scraper is pretty crude, just a 5/16" square HSS blank ground to shape and tack welded onto the end of a long piece of 3/8" (or maybe it was 1/2"... really can't remember offhand) diameter steel tubing that's flattened at one end. I use that pull scraper for roughing, and for finishing I still use files ground for pushing. Most of the time the parts are so small that the push scraper I use is one that was ground from a needle file. But getting back to pull scraping, I find it so much easier to quickly rough out a surface that way... like not only quicker, but physically I find it more comfortable and easier to control. Might have something to do with my work height currently being quite a bit lower than what it should be, though.
          Max
          http://joyofprecision.com/

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          • #20
            Originally posted by RichR View Post
            Looking good Max. It looks like you scraped the top surface of the base. Did you scrape the bottom surface too? I see 4 mounting holes. Will you
            be bolting it down and if so will you scrape the surface you will be bolting it to?
            Thanks Rich! Yes I did scrape the top of the base, but only enough to bring in the areas being contacted by the knee support and the column. The plate will ultimately be either painted or cold blued (unless I change my mind, which could always happen!). For the bottom, I want to do something to clean it up a bit, but I sure don't want to do that much more scraping on steel unless I have to. I'm working on getting access to a surface grinder just to knock it out real quick, not sure if that will pan out but it looks promising. I would like to put my initials (or name, or whatever) and year on the bottom but if I don't end up making the bottom look presentable, I'll find another place to put my markings. Like maybe a little brass plate somewhere on the column.

            Regarding mounting, the suggestion in the plans is to mount it to the top of a wooden drawer (like a small cabinet that just has a single flat drawer in it), so the drawer can be used for storing the tooling and accessories (a set of collets and set of indexing plates need to be made, so they'll need to be stored somewhere, plus there will be cutters that I'd want to keep with it)... that's what I'd like to do, I'm not sure if my woodworking skills will be up to the task though.

            I'm going to be using thin, hard rubber mounts between the base plate and whatever it gets bolted or screwed to, just to give some vibration dampening and have some give between the base plate and the mounting surface.
            Max
            http://joyofprecision.com/

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            • #21
              Originally posted by mars-red View Post
              I'm going to be using thin, hard rubber mounts between the base plate and whatever it gets bolted or screwed to, just to give some vibration dampening and have some give between the base plate and the mounting surface.
              Just don't screw it down too tight or the scraping of the base will be for naught.
              Location: Long Island, N.Y.

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              • #22
                Always a pleasure to see your work Max and I am glad you are posting this. I just subscribed to this thread and hope to be able to follow along.

                Originally posted by mars-red View Post
                .................................................. ........

                When it comes to the Chinese suppliers, I can't find any that come right out and say they are epicylcoidal, but Merlin Tools sells many sets that specifically say they are involute, then they have sets in much smaller sizes that do not specify... I suspect they are epicycloidal. They are good about answering questions, but I'm not going to bother since I've no intention of ordering them: http://www.ebay.com/itm/Set-8-Gear-C...item66a40a0efb
                Thanks for the above link. I've looked at these cutters every now and then, hoping to find that they have started to make epicyloidal cutters. The descriptions always mention the pressure angle which is a give away that they are involute.

                IIRC, pressure angle describes the angle at which two curves meet and epicycloidal teeth effectively have no pressure angle. I feel that this is one of the most important reasons that horological gearing has a more accurate transmission of motion than involute.

                For those who might be interested in further study, the book, 'Gears for Small Mechanisms' by W.O. Davis is a rather thorough explanation and comparison of both tooth forms.
                Last edited by jhe.1973; 04-13-2017, 06:17 PM.
                Best wishes to ya’ll.

                Sincerely,

                Jim

                "To invent you need a good imagination and a pile of junk" - Thomas Edison

                "I've always wanted to get a job as a procrastinator but I keep putting off going out to find one so I guess I'll never realize my life's dream. Frustrating!" - Me

                Location: Bustling N.E. Arizona

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                • #23
                  Originally posted by mars-red View Post
                  .....

                  Regarding mounting, the suggestion in the plans is to mount it to the top of a wooden drawer (like a small cabinet that just has a single flat drawer in it), so the drawer can be used for storing the tooling and accessories (a set of collets and set of indexing plates need to be made, so they'll need to be stored somewhere, plus there will be cutters that I'd want to keep with it)... that's what I'd like to do, I'm not sure if my woodworking skills will be up to the task though.

                  I'm going to be using thin, hard rubber mounts between the base plate and whatever it gets bolted or screwed to, just to give some vibration dampening and have some give between the base plate and the mounting surface.
                  Include the screws... a bushing or similar that goes through and pads all surfaces of possible screw contact is best.

                  That wood drawer will act like a drum if you let any screws etc directly touch the base of the machine. You want very compliant isolation so that even fairly low frequencies are mechanically filtered out. Rubber on the bottom is ineffective if the screw touches the top or even the bore of the hole.
                  CNC machines only go through the motions

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                  • #24
                    Originally posted by jhe.1973 View Post
                    Always a pleasure to see your work Max and I am glad you are posting this. I just subscribed to this thread and hope to be able to follow along.

                    Thanks for the above link. I've looked at these cutters every now and then, hoping to find that they have started to make epicyloidal cutters. The descriptions always mention the pressure angle which is a give away that they are involute.
                    Ahhh.... I totally missed that give-away. Yeah options really are limited for horological gear cutters. Making my own will give me a great excuse to give the Hjorth form-relieving (backing-off) attachment a work-out.

                    Originally posted by J Tiers View Post
                    Include the screws... a bushing or similar that goes through and pads all surfaces of possible screw contact is best.

                    That wood drawer will act like a drum if you let any screws etc directly touch the base of the machine. You want very compliant isolation so that even fairly low frequencies are mechanically filtered out. Rubber on the bottom is ineffective if the screw touches the top or even the bore of the hole.
                    Brilliant! I'm 100% on board, thank you for mentioning that.
                    Max
                    http://joyofprecision.com/

                    Comment


                    • #25
                      Originally posted by J Tiers View Post
                      .................. a bushing or similar that goes through and pads all surfaces of possible screw contact is best.
                      .........
                      With that thought, you might consider mounts along this line. Dirt cheap and effective isolation:

                      http://www.globalindustrial.com/p/fa...-m3-x-6-thread
                      Best wishes to ya’ll.

                      Sincerely,

                      Jim

                      "To invent you need a good imagination and a pile of junk" - Thomas Edison

                      "I've always wanted to get a job as a procrastinator but I keep putting off going out to find one so I guess I'll never realize my life's dream. Frustrating!" - Me

                      Location: Bustling N.E. Arizona

                      Comment


                      • #26
                        Max, everything looks great however your scraping looks like it needs a lot of work. You need to shorten your strokes and scrape deeper, around .0002" to .0004" in depth.

                        Sent from my XT1053 using Tapatalk

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                        • #27
                          Originally posted by Andre3127 View Post
                          Max, everything looks great however your scraping looks like it needs a lot of work. You need to shorten your strokes and scrape deeper, around .0002" to .0004" in depth.

                          Sent from my XT1053 using Tapatalk
                          Once again, what's there in the photo is in the process of being roughed. I also have no intention of getting anal about stroke length and depth. I'm making flat surfaces with better bearing contact than the rough machining, so I only "need" to do what gives me that end result. It's probably going to take me a lot longer than someone who knows what they're doing, won't have as consistent spotting, and probably won't be as cosmetically attractive, and that is perfectly fine with me.

                          Sent from my BLN-L24 using Tapatalk
                          Max
                          http://joyofprecision.com/

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                          • #28
                            Quick update, this is as far as I'm taking the two outer reference surfaces. Bearing contact is pretty good in my opinion, and checking square against a 1-2-3 block and the surface plate, that is good too.

                            Starting on the mating dovetails now, that will take some time and I'll have to get a bit creative with the column dovetails since they are open.

                            Max
                            http://joyofprecision.com/

                            Comment


                            • #29
                              Originally posted by mars-red View Post
                              Once again, what's there in the photo is in the process of being roughed. I also have no intention of getting anal about stroke length and depth. I'm making flat surfaces with better bearing contact than the rough machining, so I only "need" to do what gives me that end result. It's probably going to take me a lot longer than someone who knows what they're doing, won't have as consistent spotting, and probably won't be as cosmetically attractive, and that is perfectly fine with me.

                              Sent from my BLN-L24 using Tapatalk
                              You can use 1/2" wide HSS parting blades as scraper blades, you just need to make a holder. I used parting blades for a few years and it worked fairly well! Let me know if you'd like pictures of my scraper handle, it's very simple.

                              Sent from my XT1053 using Tapatalk

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                              • #30
                                Originally posted by Andre3127 View Post
                                You can use 1/2" wide HSS parting blades as scraper blades, you just need to make a holder. I used parting blades for a few years and it worked fairly well! Let me know if you'd like pictures of my scraper handle, it's very simple.

                                Sent from my XT1053 using Tapatalk
                                It sure wouldn't hurt to see a pic, if you don't mind. My pull scraper is a 5/16" hss bit tack welded to a long steel tube, and I like it a lot. For real fiddly work, like inside of dovetails or other cavities I'm just about ready to order a good three corned scraper. I'd welcome any recommendations in that regard. Especially if there existed such thing as a triangular scraper with two sides less than 60 degrees (like a 90, 45, 45 for example).

                                Sent from my BLN-L24 using Tapatalk
                                Max
                                http://joyofprecision.com/

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