Cam making basics

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There's also Achim Steinke's "Eine kleine, aber feine Nockenschleifmaschine", or "Small but fine cam grinding machine", at
http://www.metallmodellbau.de/Nockenwellenschleifmaschine.php
It's in German, but there's lots of pictures and drawings (paper + CAD), and Achim described some years ago (in English) their machine. A lovely machine, and lovely cams

An english description of the above was posted by Achim here at HMEM:
http://www.homemodelenginemachinist.com/f13/another-cam-grinder-10361/

 

[stevehuckss396]

Sorry if this is a silly question....

Steve, I understand everything in your offset method guide (I think), except I can only count 45 cuts in any particular cam lobe column instead of the 47 calculated at the start of the guide?

That might be correct. I have 3 or 4 different charts for that engine. The chart with 45 cuts has more duration and gives a bumpy idle. This video is the actual cam in the V4.

[ame]http://www.youtube.com/watch?v=1-JRQGPswVA&list=TL0WM3WLLdNts[/ame]

 

[Engineeringtech]

If you have a 4 jaw chuck on the lathe, you can offset it from center. Cut with HSS. The shock will damage a carbide insert.

 

[stevehuckss396]

Cut with HSS. The shock will damage a carbide insert.

Not exactly. I have made more than one cam and used Inserts for all of them. One insert lived through the entire camshaft for my V8.

 

[canadianhorsepower]

Steve,

That V4 sounds like a top fuelThm:Thm:
Is the Demon with super charger sound like that

cheers

Luc

 

[Engineeringtech]

Not exactly. I have made more than one cam and used Inserts for all of them. One insert lived through the entire camshaft for my V8.

I guess it depends on how agressive you are with cuts, and what type of material you are using. Interrupted cuts on steel apply a lot of shock to inserts.

 

[stevehuckss396]

I guess it depends on how agressive you are with cuts, and what type of material you are using. Interrupted cuts on steel apply a lot of shock to inserts.

I use 0-1 drill rod/silver steel to make my cams. I make multiple .005 passes to get to depth. The insert was a grooving tool .050 wide. Made it all the way through the cam, all 5 hours and slightly chipped the right corner. The left corner was still in great shape. The chip was from a bone head move or i'm sure it would have made it also. It can be done and not stopping to resharpen and reset the tool is why I use the inserts. Helps to speed things along.

 

[stevehuckss396]

Steve,

That V4 sounds like a top fuelThm:Thm:
Is the Demon with super charger sound like that

cheers

Luc

I don't know. I m moved up to a 5/16 tubing for the pipes on the V8. The V4 only has 1/4 inch tubes. The blower motor will have 300 degrees duration so it will sound different from the V8 even with the same tube size. Be honest, I don't know what to expect.

 

[Metal_slicer]

For a simple 1 lobe cam I just machine a blank to the major diameter of the cam,with the required shaft size in the centre. Then mount the blank in the rotary table / dividing head and mill a flat down as if I was going to reduce the blank to the minor diameter of the cam. So if the major diameter was 20mm and the minor was 15mm, I'd mill down a flat 2.5mm deep and lock the quill at that. Then simply rotate the blank 10 degrees or so, mill it and repeat. Eventually you'll have milled away everything except your lobe (the red bit in the shocking drawing below is what's removed), in a series of small steps that are easily blended with a file.

There are many other ways, and more experienced builders will post their methods I'm sure, but this is how I've been doing it.

I was thinking - Could it be possible for small lobes to be cut by milling down to the minor diameter of the lobe, lock the Z-axis, zero out the hand wheel, and then simply rotate (slowly) the hand wheel and stop at the calculated maximum degree instead of multiple facets? You should end up with the basic profile, and then all you have to do is blend in the cam nose.

For larger lift lobes a series of facets my be required if the depth of cut is to deep. But shallow lift lobes might be able to get away with continuous milling to the proper max angle.

What are your guys thoughts on this?

 

[mu38&Bg#]

I was thinking - Could it be possible for small lobes to be cut by milling down to the minor diameter of the lobe, lock the Z-axis, zero out the hand wheel, and then simply rotate (slowly) the hand wheel and stop at the calculated maximum degree instead of multiple facets?

Common endmills do not have a flat bottom. So you'd end up with a radius on face of the lobe. If you had a true flat bottom endmill it would be possible, but the feed direction isn't ideal for a setup that might not be very rigid.

Greg

 

[Cogsy]

Chuck Fellows has a great method for making single lobe cams with a boring head. The flats are barely visible. I've used it and it works well. Here's the video.

[ame]https://www.youtube.com/watch?v=ohqO0GIdoLU[/ame]

 

[Walsheng]

Chuck Fellows has a great method for making single lobe cams with a boring head. The flats are barely visible. I've used it and it works well. Here's the video.

He has a couple of videos on Youtube using this method. I am about to start building the Lil Brother and I think I will try it.
I bought the kit from Paul Breisch back around 1980 so it didn't come with the machined cam like the new kits from Ministeam.

John

 

[gbritnell]

John,
Chuck's method won't work for a hit and miss engine cam lobe as it's not a uniform shape. The cam has to open the exhaust valve but also needs a secondary flat to operate the ignition points. In other words it's not just a true cam profile like Chuck has shown. Another thing you might check when doing the 'Little Brother' cam is the amount of dwell built into the cam to operate the points. I found that for the rpm the engine runs at there was way too much close time to charge the coil so I modified the cam shape. I no longer have my drawings for the Little Brother so I can't redraw the needed shape.
gbritnell

 

[Cogsy]

If the Lil Brother has an abnormal cam shape then it won't work but for 'normal' hit and miss cams it will work. I have used this method sucessfully for the Rupnow Hit and Miss. I think I'll have to investigate this Lil Brother engine, it sounds like it might have some interesting features.

 

[Metal_slicer]

Common endmills do not have a flat bottom. So you'd end up with a radius on face of the lobe. If you had a true flat bottom endmill it would be possible, but the feed direction isn't ideal for a setup that might not be very rigid.

Greg

I want to correct my self from the last post. I said zero the hand wheel but what I meant to say was set the rotary table to zero degrees after the depth of cut is made and then rotate the rotary table say 240 degrees with the z locked. You should end up with the basic profile.

I don't understand what you mean radius. Are you saying flat endmills are slightly cupped on the bottom?

 

[mu38&Bg#]

I want to correct my self from the last post. I said zero the hand wheel but what I meant to say was set the rotary table to zero degrees after the depth of cut is made and then rotate the rotary table say 240 degrees with the z locked. You should end up with the basic profile.

I don't understand what you mean radius. Are you saying flat endmills are slightly cupped on the bottom?

I understand what you're saying. Yes, the bottom of the endmill has a ~2° relief toward the center called dish angle.

Just try it on a piece of stock. Nothing like a real test to prove an idea.

Greg

 

[Metal_slicer]

I understand what you're saying. Yes, the bottom of the endmill has a ~2° relief toward the center called dish angle.

Just try it on a piece of stock. Nothing like a real test to prove an idea.

Greg

I didn't know this, but it makes sense. I am going to try this anyway on a test piece as soon as I can get my hands on a rotary table.

I appreciate your input on this.