Cutting a Cam

Hello,

I’ve been pulling out what little hair I have theses last few hour trying to work out how to cut the Cam for my build of the Upshur I/C Engine.

The plans appear to show an offset on the mandrel of 0.312”, I can not get this to work.  When I was unable to cut the Cam shape I altered the offset to 0.156”….. this did not work!

I have attached photos of the Cam plans and two of my results.

Can anyone explain where I’m going wrong?

Regards
Tom

Edited By Tom Gullan on 17/09/2017 00:01:17

Edited By Tom Gullan on 17/09/2017 00:03:29

Hi

I think the idea is that you take a number of incremental cuts. After taking the first cut the cam blank should be rotated a few degrees and a second cut taken, then repeated for a third cut, forth cut and so on untill the full cam profile is complete. This will leave the cam with a number of facets which will need to be blended using a file, emery paper and or stone.

Your first cam looks right for the first cut, it needs setting up in the fixture again and several more cuts rotating the cam on the fixture a few degrees each time.

Nige

As Nige says you have just done the first flank cut, now you just need to keep rotating the cam on the mandrel in steps of say 10 degrees and take a cut at the same setting each time. Keep doing that until you are left with 0.250" or uncut cam at the full dia.

Think of the blue circle as your first cut which gives the flank of teh cam and the subsequent green circles as your 10deg cuts and you can see how they strat to firm the base radius of the cam.

Edited By JasonB on 17/09/2017 07:45:03

Gentlemen,

Thank you. I’m off to my workshop try that.

Regards
Tom

lHello,

At the moment I am turning the blank Cam... would it make a difference if I turne the mandrel?

Tom

That won't work, as you will only have the previously cut flank passing the tool in effect all you are doing is moving the mandrel just as it would rotate as the lathe goes round

Thank you.

Gentlemen,

Thank you for all your input, after several attempts I manage to get the desired effect.

Regards

Tom