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Thread: Boring and Honing Service

  1. #1
    Diamond geezer 500 Club
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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 at 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. #2
    have you put this on facebook also?

  3. #3
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    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 :-)

  4. #4
    Diamond geezer 500 Club
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    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 :-)

  5. #5
    Diamond geezer 500 Club
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    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 :-)

  6. #6
    Diamond geezer 500 Club
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    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 at 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 :-)

  7. #7
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    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 :-)

  8. #8
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    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".

  9. #9
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    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 :-)

  10. #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.

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