Straight edge for checking the slide ways on my mill’s knee

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Straight edge for checking the slide ways on my mill’s knee

Home Forums Workshop Tools and Tooling Straight edge for checking the slide ways on my mill’s knee

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  • #503433
    Mark Davison 1
    Participant
      @markdavison1

      I've got the knee off my harrison mill and want to to check the wear on the ways, in particular the narrow ones on the underside. Where can I get a 12" straight edge to apply the blue to? Alternatively any ideas what i can use as an alternative, e.g is gauge plate flat enough? Measuring the side without the V suggests there is some wear in the middle but I'd like to check that the wear is only in the bottom face.

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      #19992
      Mark Davison 1
      Participant
        @markdavison1
        #503435
        Clive Brown 1
        Participant
          @clivebrown1

          I'd have thought ground flat stock was usually good enough for your purpose If you wish to check your GFS, buy 2 similar pieces and check them against one-another, faces 1 to 1 and then 1 to 2.

          #503439
          Anonymous

            Rectangular ground flat stock is ground on the wide sides only. The narrow sides are as sawn.

            Andrew

            #503454
            Mark Davison 1
            Participant
              @markdavison1

              I'd wrongly assumed all 4 sides would be ground, but apparently not I found this on the interweb. Even the thickness doesnt sound very accurate

              Thickness +0.05/-0mm
              Width +0.2/-0mm
              Length +5/-0mm

              #503465
              old mart
              Participant
                @oldmart

                Straight edges do come up for sale regularly on the unmentionable site.

                #503467
                JohnF
                Participant
                  @johnf59703

                  Gauge plate is not guaranteed to “flat” or “straight “ over its length unless ground to be so and I think this is unlikely on commercially produced stock. Better than nothing but IMO not good enough for the job in hand.

                  what you really need is a camel back straight edge preferably with the facility to check the V as well.

                  John

                  Or start from scratch and use 3 pieces to scrap in sequence and end up with a perfectly straight tool for the job

                  Edited By JohnF on 25/10/2020 18:27:44

                  #503471
                  Oldiron
                  Participant
                    @oldiron
                    Posted by old mart on 25/10/2020 18:20:29:

                    Straight edges do come up for sale regularly on the unmentionable site.

                    Sorry I do not understand this statement. Ebay is a perfectly legitimate site to mention even if some of the goods are not.

                    regards

                    #503473
                    old mart
                    Participant
                      @oldmart

                      I have had some of my posts deleted even when they were totally innocuous, when listing some of the totally stupid mistakes made by advertisers on the ebay site by certain overzealous moderators on this forum.

                      #503474
                      not done it yet
                      Participant
                        @notdoneityet

                        And one can post reviews of cheap chinese tat, on the forum, too.

                        #503475
                        Mark Davison 1
                        Participant
                          @markdavison1

                          Nothing on evilbay at the moment, other than a pair of 12" long chesterman parallels, which would do at push but they are £90 posted (with some surface rust). Ive seen cammel back castings but need something ready to use.

                          I'm thinking I'll have to buy one of Chronos' 400×400 granite surface plates and sit it on there upside down on 4 1-2-3 blocks to allow for the v. That way I can use a dti on my scribing block. Becoming a bigger job than I'd expected. My current surface plate is only 8"x12" so not big enough.

                          #503479
                          old mart
                          Participant
                            @oldmart

                            I bought a 24" square cast iron table a year ago for a bargain price, but after getting it in the back of my Corsa D, I hurt my left shoulder and it still isn't right. The plate just fitted in the car without dropping the rear seats and very fortunately, there were four 3/8 unf holes through the top. I screwed in lifting lugs and got it out with the engine hoist at the museum. It is very useful. For home use, I would recommend the biggest second hand plate that can be managed and afforded. With a cover on most of the time, it is a worktop not a liability.

                            #503481
                            peak4
                            Participant
                              @peak4

                              An 8"x12" surface plate would enable you to blue and scrape something longer if you do it across the diagonal.
                              Maybe one long edge of one of the various lattice style cast iron spirit levels. Here's an ebay example, though I'm not particularly suggesting this one. Perhaps a trip to a local scrapyard will show up a length of something cast Iron, from which you can cut, and machine a slice, before you strip the mill.

                              Without wishing to continuously direct people away from this fine forum, I've an album over on Flickr showing the various setups I used when fettling the various straight and V ways during the rather amateurish refurbishment of a Herbert grinder during the first covid lockdown.
                              I've not reproduced the album on here as there's the best part of 150 photos to resize, upload and caption.
                              Doing it on Flickr and also Facebook took me long enough as it was.

                              It may not be the textbook way of doing things, but I used what I had at the time, and some of the more inventive setups might give you some ideas to develop further, and better, to suit your own needs and available equipment.

                              Bill

                              #503482
                              Pete Rimmer
                              Participant
                                @peterimmer30576

                                Gauge plate is not suitable as a scraping reference normally because it's aspect ratio is too high, meaning it will bend under it's own weight. It might get you close but it'll sag in the middle if you support it at each end.

                                For a 12" straight edge look on ebay for kblastmetalworking. He sells 12" versions pre-machined for £180 which need scraping on a surface plate. I have one and it's very nice, a bit softer iron than your usual straight edges but that only makes it easier for the novice to scrape in and I have yet to get any wear in mine which is 3 years old. fOr sure, it's been very stable.

                                That said, checking for wear is only the start. Knee ways wear at the ends so expect your straight edge to rock, which can give up a false print if you're not careful. Then once you have determined where the wear is you need to determine how to scrape it so that it ends up in alignment with no droop or twist. It's not enough to make a way flat – you need to make it flat and pointing the right way too. The alignment on a milling machine is much more critical than on a lathe because the part moves, not the tool. On a lathe you can have a lot of wear and still get good dimensional parts, not so much on a mill.

                                #503490
                                peak4
                                Participant
                                  @peak4

                                  Posted by peak4 on 25/10/2020 19:51:46
                                  ………………
                                  Without wishing to continuously direct people away from this fine forum, I've an album over on Flickr showing the various setups I used when fettling the various straight and V ways during the rather amateurish refurbishment of a Herbert grinder during the first covid lockdown.
                                  ……………………………………..
                                  Bill

                                  Sorry, the link to Flickr on the original post was wrong, I thought I'd checked it.

                                  Bill

                                  #503497
                                  Mark Davison 1
                                  Participant
                                    @markdavison1

                                    You clearly spent a lot of time on that grinder, great work.

                                    I intend to play safe and only tickle small areas with a scraper if it is obvious that I'll improve things. The saddles get a bit tight at either end of its travel and im hoping most of that is caused by wear on the narrow flat ways under the knee. I think it is 0.035mm based on the mic readings. I don't want to go anywhere near the top surface of the knee and certainly not the v! I'm not feeling that brave at the moment.

                                    Edited By Mark Davison 1 on 25/10/2020 23:05:50

                                    #503498
                                    peak4
                                    Participant
                                      @peak4
                                      Posted by Mark Davison 1 on 25/10/2020 23:05:33:

                                      …………… I don't want to go anywhere near the top surface of the knee and certainly not the v! I'm not feeling that brave at the moment.

                                      Edited By Mark Davison 1 on 25/10/2020 23:05:50

                                      I can understand why, particularly if your mill is essentially usable.
                                      In my case, the grinder was £250 delivered, and despite initial optimism was largely unusable.
                                      I'd never scraped anything in my life before, and wasted quite a bit of time just finding a suitable grade of carbide to make a scraper from. I couldn't justify the price of a proper Sandvik insert, or so I thought at the time; it probably would have been worth it with hindsight.
                                      I bought a box of these, which seemed to be strong enough, and also held an edge quite well, though I've nothing commercial to compare it to.
                                      https://www.ebay.co.uk/itm/50mm-Scraper-Blades-For-Tungsten-Carbide-Scraper-Linbide-10-Blades-In-Pack/174321208943?hash=item28965a8e6f:g:EqQAAOSw1IVbt2hm

                                      I made a clamp holder to use them end on, as you saw on Flickr. I also cut one in half and silver soldered it to a length of bar for a wider scraper. Sharpening & honing are obvious from the album.

                                      If I can do it from scratch, so can anyone else, though I do wonder if I've made some areas too flat and not left deep enough depressions to act as oil reservoirs.

                                      Bill

                                      #503618
                                      JasonB
                                      Moderator
                                        @jasonb

                                        Cutwel do straightedges in Stainless, tool steel and granite. Steel ones are good to around 3 microns for a 300mm long one, granite is a bit better than that. at 3 microns on a 500mm length.

                                        #503639
                                        Mark Rand
                                        Participant
                                          @markrand96270

                                          Deleted

                                          Edited By Mark Rand on 26/10/2020 21:17:47

                                          #503703
                                          Nick Clarke 3
                                          Participant
                                            @nickclarke3

                                            While not certain if a straightedge would be wide enough for what you want both Zoro tools and Chronos, amongst others no doubt, list them in various sizes.

                                            In your position I would probably go for the small surface plate.

                                            #503752
                                            Howard Lewis
                                            Participant
                                              @howardlewis46836

                                              My 18" straight edge came from Cromwell Tools. If you are in UK, there should be a branch somewhere near you.

                                              Howard

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