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  • Boring and Honing Service

    Hello,

    I'm not sure where I should post this, but I'd like to advertise that I've recently acquired a Buma engine cylinder boring bar, and a matching set of honing equipment. This may not seem very ground breaking, as I'm sure others have bought such items for personal use in the past. The difference is that I was trained for 5 years to be an engine reborer and honer when I first left school, so I have some modicum of knowledge on how to use these things. As such I'd like to now offer my services as a professional engine reborer and honer for single, twin, and other multi cylinder engines where each cylinder is a separate item, or a twin cylinder unit, i.e. Triumph, BSA and Norton twins, etc.

    The reason I purchased the boring bar is that I'm going to be retiring from my present occupation soon (SQL and database reporting analyst programmer) and I'd like to take up something that will earn me some money and keep me off the streets when I retire.

    Technical details:

    The Buma boring bar has a boring range from 2.2" up to 4 3/8", so will rebore most if not all of the current Rotax engines, and quite a few others as well, provided they don't have Nikasil liners that is. It will also bore most vintage motorbikes and scooters (Triumph, BSA, Norton, Vespa, Lambretta, etc) so I'd like to advertise my services to those enthusiasts as well.

    However, I don't know if this is the appropriate place to put an advert for such services in the microlight world, or if there is a section that I haven't yet noticed on the forum, where such adverts should go.

    Any advice on where this ad will be gratefully received, and I will be happy to move the ad to somewhere more appropriate if there is somewhere more appropriate to put it.

    Best regards,

    Bob Hood

    P.S. I've added some photos of the boring bar, tools, jig, and honing equipment. Oh, and my location and contact details if anyone is interested are as follows;

    Location: Borehamwood, Herts (nearest airfields London Colney and Plaistows)
    Tel no. : zero, seven, nine, five, six, six, eight, nine, eight, zero, six
    Email : bob [dot] hood [dot] uk [@] gmail [dot] com


    Buma 1.jpgBuma 5.jpgTools 1.jpgJig 1.jpgHone 1.jpg
    Last edited by Bob Hood; 17th January 2018, 16:50. Reason: Added contact details
    XL's forever! Well, one of them anyway. It's all I can afford, not to mention the Raven and the Mini-Max. Oh, and I almost forgot the Spectrum as well :-)

  • #2
    have you put this on facebook also?

    Comment


    • #3
      Mik,

      Not yet, but they will be going up on the microlight pilot's timeline and the SSDR timeline
      XL's forever! Well, one of them anyway. It's all I can afford, not to mention the Raven and the Mini-Max. Oh, and I almost forgot the Spectrum as well :-)

      Comment


      • #4
        Mik,

        I've now added it to the microlight pilot's facebook page and the SSDR facebook page.
        XL's forever! Well, one of them anyway. It's all I can afford, not to mention the Raven and the Mini-Max. Oh, and I almost forgot the Spectrum as well :-)

        Comment


        • #5
          Hello again,

          Just posting up an addition to my advert above for boring and honing services. I now have the necessary clamps for boring car and van engine blocks. So I can now bore and hone anything with a bore size of 2.2" (56mm) up to 4 3/8" (111mm), whether it's a single, twin, triple, four cylinder, five cylinder, six cylinder, or 8 cylinder engine block.
          XL's forever! Well, one of them anyway. It's all I can afford, not to mention the Raven and the Mini-Max. Oh, and I almost forgot the Spectrum as well :-)

          Comment


          • #6
            Hello,

            Just an update to let you all know that I've now acquired a second boring bar. This one is the SPS mini, which is much smaller and lighter than the Buma, and is designed for boring out motorcycle and scooter cylinders. As such it is better suited for boring out our Rotax 2 stroke engines.

            I have an advert on the Car and Classic website, and here's a link to it.

            https://www.carandclassic.co.uk/car/C1053818

            In the ad you can see that I've explained much more about the services I can offer, and also about my pricing structure.

            Best regards,

            Bob Hood

            P.S. I've added some photos of the two boring bars and jigs.

            Location: Borehamwood, Herts (nearest airfields London Colney, Plaistows, and Elstree)
            Tel no. : zero, seven, nine, five, six, six, eight, nine, eight, zero, six
            Email : bob [dot] hood [dot] uk [@] gmail [dot] com

            Bars 1.jpgStands 1.jpgBars and Stands 2.jpg
            Last edited by Bob Hood; 21st February 2019, 18:09.
            XL's forever! Well, one of them anyway. It's all I can afford, not to mention the Raven and the Mini-Max. Oh, and I almost forgot the Spectrum as well :-)

            Comment


            • #7
              Hello again,

              I've been playing with my new SPS toy and rebored my spare 462 barrels again. The pics below show one barrel rebored and the other one bored and honed. The one on the right, with the cross hatched finish is how I was always taught to finish a bore when I worked at Hartcliffe Engineering. However, in the blurb that came with the SPS bar, it says that as the SPS mini bar does a fine cut, the finish is good enough to use without honing afterwards.

              Personally I think you should always hone a bored cylinder, as the surface hardens to a certain extent when it's bored, and the honing stones cut through that hardened surface in order to produce the cross hatching. This wavy angled finish allows the tiny scratches to hold oil and therefore lubricate the rings while they're running in. It also helps to prevent the piston from seizing at the same time. So I don't think I'll be following the advice in the SPS blurb, but will continue to hone every cylinder I bore.

              Bored Honed.jpg
              XL's forever! Well, one of them anyway. It's all I can afford, not to mention the Raven and the Mini-Max. Oh, and I almost forgot the Spectrum as well :-)

              Comment


              • #8
                Nice job Bob. I've passed on a link to this thread to some motorcycle drag racing friends.

                I was under the impression that honing was originally used as the only available means to produce an even finish, especially when the quality of the cylinder material was less than ideal. Theories about oil retention in the honing marks came later. I don't see why the bored finish would retain any less oil than the honed finish.
                Where I work, we make hydraulic components to very fine tolerances (<2 microns) with similarly close constraints on roundness and surface finish. We used to hone and roller burnish the parts, but the new machines and tooling can achieve everything with very little cutting pressure, avoiding distortion and surface hardening.
                I'm not suggesting you do anything different to what you have learned and tested. It is always interesting to understand how the accepted practices were developed.
                Pete T.

                "A closed mouth gathers no feet".

                Comment


                • #9
                  Peter,

                  Interesting post! Back when I worked as a reborer I used Van Norman boring bars. In particular I mainly used a 944, but I also had a slightly larger 905, and a bigger still 777S. They all have a relatively coarse cutting pitch in comparison with the SPS bar I've just bought. Because I normally used to cut a depth of either 0.020" or 0.030" per cut, the combination of cutting depth and vertical speed (pitch) of the cutter, the surface was nowhere near as smooth as that achieved with the SPS. So I was always told to hone the bores in order to finish them.

                  I can understand SPS saying that due to the fine pitch of the cutter, the finished bore is just as good as a honed finish, but for some reason I still (probably irrationally) think that grooves in the cylinder wall that are effectively diagonal to the position and movement of the rings in the barrel, are likely to distribute oil slightly better than grooves that are at 0 degrees to the position of the rings. Furthermore, despite the fine pitch of the SPS, the feel of the bored finish is definitely not the same as that of the honed bore, and on a purely touchy feely level, the honed finish feels smoother.

                  Don't think the bored finish being rougher is due to a blunt cutter either. The cuts I did on the two barrels in the picture were the first cuts I did after sharpening the cutting tool on the diamond impregnated lapping wheel on the boring bar. Furthermore, I only cut 0.008" from each barrel, as I was keen to see how well the centering pegs worked on this bar.

                  My old Van Norman bars had 4 catspaws. These were expanding feet mounted on the outside of the lower end of the boring bar, but not part of the cutting head, and these were wound out using a ratchet wheel at the top of the bar. This centered the bar in the cylinder before it was clamped into position. During the cut these catspaws were slowly expanded by hand once they'd reached the top of the barrel, so that they could support the bar as it went down the barrel and help prevent the bar from any reactive distortion as it went further away from the main bearing sleeve of the bar. That is unless boring a 2 stroke bore that has ports in the side. In that case the catspaws couldn't be used, so I had to use lighter cuts to prevent any movement at the cutting head.

                  The SPS on the other hand has a slightly different method of centering. It has 3 pegs that do the same job as the catspaws, but these spin with the cutting head rather than staying with the main bar. So they can't be expanded during the cut in order to help support the bar. This means that as the cutting head moves further from the main bearing, there is more possibility of it bending under load slightly. This can happen particularly if the cut is a heavy one, and can lead to a difference of several tenths of a thou between the size at the top and that at the bottom of the bore. This is something that may be worse with a small diameter bar in a large bore, I'll let you know what I find as I go on, as the SPS has a 35mm diameter bar. In comparison the Van Norman 944 I used to use was closer to 52mm diameter, and the Buma I now own has a bar diameter of 57mm.

                  Anyway Peter, I just did what I was told to do and didn't question it at the time, as I could see the logic of what I was told to do. I didn't attempt to go against my bosses or I'd have got a right bollocking. As for the future, I think I'll continue honing cylinders when I bore them. I'm sure my customers will expect it, and I'm happy to do it, even if newer tooling and methods might mean that honing is no longer required from an operational standpoint.
                  XL's forever! Well, one of them anyway. It's all I can afford, not to mention the Raven and the Mini-Max. Oh, and I almost forgot the Spectrum as well :-)

                  Comment


                  • #10
                    Interesting that the theories of oil retention are what I've always been led to believe was the principal reason for honing with the almost diagonal marks.

                    To my, non-academic, mind it made a lot of sense particularly with my air cooled two stroke. That is because there is oil there from practicaly the start with a two stroke, but with the alloy pistons expanding initially at a greater rate than the steel bore liners, having increased oil retension in the bores seems a good idea. Particularly as the CHT, in the warm up period, is a lying jade being fitted to part of the combustion chamber that will heat the fastest.

                    Comment


                    • #11
                      Hello,

                      I must say it never ceases to amaze me how ingenious people can be. A customer brought a 1978 Suzuki PE 250 barrel to me the other day, along with the piston. He's been having a lot of trouble starting the engine from cold and after doing all sorts, including replacing the carb with a brand new item, he decided that the compression was at fault. He wasn't far wrong either. The PE is a reed valve induction engine, so it relies on having a good vacuum in the crankcase when cold in order to suck the fuel air mixture in past the reeds. A worn bore and/or worn or broken rings, will reduce the compression above the piston, and the vacuum below it, so that less fuel can get past the reeds, particularly when cold.

                      Here's a photo of the piston he brought with him.

                      Piston holes1.jpg

                      See the two little holes in the area where the piston has previously seized? Some bright spark decided to drill those after the engine had seized and been freed off, so that some of the petroil mixture would be forced through them and into the previously seized area every time the piston went down the bore.

                      Clever? Yes! Good practice? No!

                      Thank goodness the holes were as small as they were, or the piston could have cracked around them, and broken into pieces, which wouldn't have done it any good at all.

                      The standard bore size on these engines was 67mm, with a stroke of 70mm, so it was undersquare. That's understandable, as the PE was designed as a mudplugger trail bike, with lots of low down torque and only 28hp. This particular one had been bored out to 67.6mm. Looking up the normal oversizes for this engine I couldn't find a 67.6mm oversize, the nearest was 67.5mm. However, this one had definitely been bored to 67.6mm, not 67.5mm. I measured it half a dozen times to confirm this, and the boring cutter marks are still in the cylinder wall at this size, so I know it's not worn the extra 0.1mm since being rebored. Furthermore, the cutter marks I just mentioned were in a sort of herring bone pattern, as though the cutter was blunt and chattering all the way down the bore. If I can I'll try to take some photos of it and put them here, as I've never seen cutter marks that bad before (and I saw a few back in the day!), you can even feel them with your finger nail.

                      The piston shown above, was 67.3mm at the bottom of the skirt, which is where pistons are normally measured for clearance purposes. So the gap between piston skirt and the cylinder was over 0.3mm. 0.3mm is 0.012" but the actual clearance on this one was 0.013", and is more than three times the recommended gap for most engines, which is normally around 0.004", or 0.1mm.

                      No wonder he couldn't get the thing to start! There must have been so much blow by at the rings and skirt when the engine was cold that there'd hardly be any vacuum for sucking fuel into the engine when cold. As the engine warms up the piston expands in the bore and takes up much of the clearance, so the compression increases at the top and the vacuum increases at the bottom, thus sucking in the correct amount of fuel mixture every revolution, and the weak mixture problem goes away.

                      We've managed to find a 68mm piston in the US, so he's ordered it. It wasn't cheap, I think the total cost, including postage from the States works out at around 130 or so. When it arrives I'll see about boring and honing the barrel out to match it. I'll let you know how it all works out, and whether his bike starts and runs correctly after the piston clearances have been returned to factory spec.
                      XL's forever! Well, one of them anyway. It's all I can afford, not to mention the Raven and the Mini-Max. Oh, and I almost forgot the Spectrum as well :-)

                      Comment


                      • #12
                        Thank goodness I've never been that clever!

                        Comment


                        • #13
                          Hello again,

                          Further to my last post about the piston with holes drilled in the side. I thought it best to update you all. The customer arrived yesterday with his brand new 68mm piston for his Suzuki PE 250 engine. It was made by Wiseco in America, and the customer had to buy it from there as there doesn't seem to be a UK agent for them. As a result we've had to wait for a week for it to arrive, and the customer was keen to bring it round to me last night.

                          I read all the bumph that came with the piston in the box, and guess what? I was very surprised to discover that if the new piston arrives without the holes, then you have to drill them to match your particular engine! Who knew? It never occurred to me that Wiseco would put instructions in the box with it to drill two little holes into the side of the piston on the exhaust side, and in line with the central supporting bar that splits the exhaust port in two. I've never come across that before, and I've no idea if it's just on this particular make and model of bike that requires it, or whether there are other 2 stroke singles out there that need to have this done.

                          I guess they've had issues with pistons seizing on this particular bit of cylinder wall because the supporting bar's got hot and expanded into the bore. That would also explain why the piston fitting instructions also say to 'relieve' the central support bar by .002" - .004". Interesting eh? Well, I've done what they required and drilled the two holes to the correct size, and in the location they specified. I've also 'relieved the face of the support bar by around .002" and made sure to chamfer the edges of all the ports in the barrel, to help prevent a ring from catching on an edge and breaking.

                          One other thing though was that the skirt clearance is listed as .06mm (.0025") and at the correct bore size of 68mm there was not enough clearance. So I had to take out an extra .0005" in order to get the skirt clearance up to .0025". The problem is that with the skirt clearance now correct, the rings as supplied with the piston, have more than the specified .004" per inch gap, i.e. the gap should be just under .012", but with the extra .0005" to get the skirt clearance, the ring gaps are now just over .014". However, it does say on the Wiseco website that for aircooled engines one can allow up to .005" per inch gap. So all is not lost, and I can breathe again. Phew!!
                          XL's forever! Well, one of them anyway. It's all I can afford, not to mention the Raven and the Mini-Max. Oh, and I almost forgot the Spectrum as well :-)

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                          • #14
                            Well that's a new one to me. It makes a sort of sense but those margins are a bit too close for me, I think I'll stick to cruder engines.

                            Comment


                            • #15
                              Had a text from the customer this morning thanking me for the work I did on his barrel. The engine started no problem today. So a happy customer!
                              XL's forever! Well, one of them anyway. It's all I can afford, not to mention the Raven and the Mini-Max. Oh, and I almost forgot the Spectrum as well :-)

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