Simple cam grinding jig

Discussion in 'Machine Modifications' started by cooksservices, Nov 22, 2019.

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  1. Nov 22, 2019 #1

    cooksservices

    cooksservices

    cooksservices

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    Hi, I have hesitated a for a few days on posting this as I feel that compared to a few of the gorgeous cam grinding machines/ jigs that guys here have built mine looks rather shoddy and quite inaccurate. That said it has produced some satisfactory results for me and the best cams I have produced so far. So Hopefully it might help others or even inspire them to have a go at building something similar.
    This was built in around six hours and totally from scrap metal. There was no real maths involved which might appeal to some people, just getting the parts to sit square and roughly on centre line of your bench grinder. I can’t comment on any errors this design might introduce into your cam design but I could produce a couple of different cam versions to try in my engine that worked well.

    I worked out that I could have the master cam on the same shaft as the blank and that I would have to make an odd shaped master cam to produce the miniature cam that I needed. I couldn’t quite picture what it would look like so I filed up a rough miniature cam and put it on my machine with a pencil offset by 15mm mounted the the other end of the rotating shaft. I then held up a price of card and turned the spindle that drew the picture of the master cam design, one size of circle then an offset circle protruding from the first circle. It was then that it became clear in my head what the master cams needed to look to look like. The main diameter of the master cam produces the base circle then the protruding circle produces the duration and lift. The base circle on the master cam could be any size but the relationship between that and the protruding circles radius is what seemed to change the duration whilst the amount of protrusion is what altered the lift on the cam. I’m sure the relationship between these two circles and the amount of protrusion could be explored in much greater detail but I have made my cams and they work well.
    I bolted my two disks together so that the second disk protruded from the bigger disk by 2.5mm and had a protrusion duration of 120 degrees. This meant that the cam lobe produced would be 2.5mm high with a duration of 120 degrees. In the engine this resulted in a fair bit les than 240 degrees of duration on the crank as my valve train is quite inefficient. The next master cam I designed allowed for the loss of duration by making the second disk bolted on the master cam slightly bigger to give a longer duration.

    I hope you can understand the way I got this to work. Hopefully these pictures will help clear things up a little. I’ll answer any questions the best I can.

    Thank you for reading, Sam.

    FCCD3648-907D-4953-B19C-AF4D3B4E8F9F.jpeg 4E62A293-0CCA-4804-A98A-245BF1113FA5.jpeg CFAE8750-ADD6-4FCC-8202-D5DB31D34C71.jpeg 4BCBD493-EE94-420B-B200-67FBCD8495BB.jpeg 7F464E9A-1343-46B9-90AC-FD893B6596E9.jpeg 14336001-4B96-493E-9474-F180EC2A1E5E.jpeg D2A898FB-1B7C-4EF7-A3AB-9F9902C7CAD5.jpeg
     
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  2. Nov 22, 2019 #2

    XD351

    XD351

    XD351

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    Nothing to be ashamed of there !
    I find a lot of designs for cam grinders are overly complicated and yours appears to be brilliantly simple and it works !
    I like it !
    Any chance of a few photos side on showing the rocking mechanism ?
     
  3. Nov 22, 2019 #3

    cooksservices

    cooksservices

    cooksservices

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    Hi thanks for your reply :). Here is a video link that might explain slightly better than I can with words.
     
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  4. Nov 22, 2019 #4

    XD351

    XD351

    XD351

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    Thank Sam !

    Am i correct in thinking that the in feed is via the threaded rod and nut at the front ?
     
  5. Nov 22, 2019 #5

    cooksservices

    cooksservices

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    Yes that’s correct, there is also adjustment on the master cam rest to allow for different master cam sizes. As my stone seems quite soft I cut the bulk of waste off the cam with a hacksaw first to minimise the wear. Then they are case hardened cleaned up and set in place on the shaft using the grub screw. I’m sure a one piece cam shaft could be made with this design by adding a degree wheel and pointer on the shaft and master cam as the rocking art can be moved across around three inches.
     

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  6. Nov 22, 2019 #6

    XD351

    XD351

    XD351

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    Being able to grind one piece cam would be a bonus !
    I will have a look at your other videos on your channel later today !
     

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