# Cam making basics



## Putt-Rite (Jun 18, 2013)

Can somebody point me in the direction on the subject of how cams are made (no cnc or anything like that) using common machine shop tools?


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## Cogsy (Jun 18, 2013)

It really depends on what type of cam you need. Simple single lobe cams are easy, but comlex multi lobe cams I have no idea about. What are you trying to build?


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## Johann (Jun 18, 2013)

Hi All, this will help me too...I am busy with my first engine (Webster), and the cam making must be done in the near future. I have a Maximat V10 with milling attachment and rotary table in my little workshop available...


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## Cogsy (Jun 18, 2013)

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.


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## canadianhorsepower (Jun 18, 2013)

http://www


> you should find all your answer here


.

http://www.popularhotrodding.com/tech/0607phr_camshaft_basics/

enjoy


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## gbritnell (Jun 18, 2013)

Here's one I did when I made the camshaft for my Holt engine.
http://www.homemodelenginemachinist.com/f31/holt-camshaft-build-tutorial-5052/
gbritnell


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## gus (Jun 18, 2013)

Cogsy said:


> 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.



Hi Cogsy,

Thanks. This tip is J.I.T.(Just In Time) as I am about to cut the cam for "Webster".


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## Johann (Jun 18, 2013)

Hi Cogsy, thanks seems quite straight forward. Now the mental planning can begin. Do you think EN36 is the right material for camshafts ? I happen to have it available..


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## Cogsy (Jun 18, 2013)

Johann said:


> Hi Cogsy, thanks seems quite straight forward. Now the mental planning can begin. Do you think EN36 is the right material for camshafts ? I happen to have it available..


 
I honestly have no idea about metal selection at all. I use whatever I have available to me, if it wears out fast I'll do a bit more research when I rebuild it. Sorry, but I'm sure someone knowledgable will help you.


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## gbritnell (Jun 18, 2013)

I make my cams from water hardening drill rod (W-1) I don't harden the cam but do harden the tappets if they are the flat type. If I use roller lifters I harden the roller. 
gbritnell


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## Putt-Rite (Jun 18, 2013)

How about the duration, or size of the radius for the pointy end, is there a simple explanation for how that is determined?


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## gbritnell (Jun 18, 2013)

Luc sent an excellent link to all the information one could need. There are no hard and fast dimensions for cam lobes. It all depends what one wants his engine to do. 
gbritnell


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## stevehuckss396 (Jun 18, 2013)

I make my camshafts in the lathe using a simple fixture and excel spread sheet. I'll attach a file that will explain the whole thing. The artical covers a cam for a V4. Here are 2 others. They are all made using this method.


V8 cam





V twin



 

View attachment Offset turning the camshaft.pdf


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## Art K (Jun 18, 2013)

Hi Putt-Rite,
I guess my method is very similar to Georges method but I use a program called CamCalc found at this web site.
http://modelenginenews.org/design/CamTable.html
This takes most of the math out of the calculation. There are parts of the parameter fields you must fill in, such as base circle radius, valve lift, flank radius, increments and it gives you a table very much like George's. starting at the base diameter as zero and amount of lift for each degree of rotation. You can have a fairly complex cam shape. On my Upshur single I used 2 degree increments and hardly needed to file the cam when I finished machining. I have never used it on anything but a single. Here is the best photo I have of the cam.
	

	
	
		
		

		
		
	


	













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Art


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## Ripcrow (Jun 19, 2013)

How would a simple wheel with a high spot work as a cam,even running a small bearing on the wheel so that the lifter will work smoothly and dependent on degrees of rotation covered by your raised spot you could time the length of time that the valve is open for.to obtain the right amount of movement at the valve you may have to alter the pivot point on the rocker to gain mechanical advantage. I am in the same boat no Cnc so this is how I plan to make my cam lobes. Just an idea


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## Putt-Rite (Jun 19, 2013)

Here's another good article:

http://www.iskycams.com/degreeing.php

I find I have to read something like this, let it digest for a day or two, then read it again, etc, until it sinks in. I gather it's not hard to do or critical either. In fact, if I read it correctly, any overlap between 0 and 30 deg will run, in fact, the more overlap, the better.


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## stevehuckss396 (Jun 19, 2013)

Putt-Rite said:


> if I read it correctly, any overlap between 0 and 30 deg will run, in fact, the more overlap, the better.




That depends on what your goal is. The more duration and overlap the harder it is to start the engine by hand. My engines have alot of both and will not start with a flip of the flywheel. I have to use a starter for RC planes to get them going. Not the end of the world for me but to somebody else it might be a problem. On the upside a low idle seems easier to attain on the multi cylinder engines. 

No one cam is great for all engines.


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## cidrontmg (Jun 19, 2013)

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


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## mu38&Bg# (Jun 19, 2013)

I hand start RC airplane four strokes with 60° of overlap all the time. RC glow engines are started with a wet cylinder though and are easy to prime without flooding. Early engines built had little or no overlap. Overlap is mostly related to power. Because the valve takes many crank degrees to open, opening the intake valve before the piston is at TDC allows for the valve have greater open area when the piston begins downward travel. Later when tuning intake runners and exhaust headers became common this was used to further improve flow through the cylinder with overlap.

Greg


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## Iggsy (Jun 20, 2013)

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?


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## /// (Jun 20, 2013)

cidrontmg said:


> 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/


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## stevehuckss396 (Jun 20, 2013)

Iggsy said:


> 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]


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## Engineeringtech (Jul 29, 2013)

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.


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## stevehuckss396 (Jul 29, 2013)

Engineeringtech said:


> 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.


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## canadianhorsepower (Jul 29, 2013)

Steve,

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

cheers

Luc


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## Engineeringtech (Jul 30, 2013)

stevehuckss396 said:


> 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.


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## stevehuckss396 (Jul 30, 2013)

Engineeringtech said:


> 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.


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## stevehuckss396 (Jul 30, 2013)

canadianhorsepower said:


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



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.


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## Metal_slicer (Apr 25, 2015)

Cogsy said:


> 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?


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## mu38&Bg# (Apr 25, 2015)

Metal_slicer said:


> 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


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## Cogsy (Apr 25, 2015)

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]


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## Walsheng (Apr 26, 2015)

Cogsy said:


> 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


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## gbritnell (Apr 26, 2015)

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


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## Cogsy (Apr 26, 2015)

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.


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## Metal_slicer (Apr 26, 2015)

dieselpilot said:


> 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?


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## mu38&Bg# (Apr 26, 2015)

Metal_slicer said:


> 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


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## Metal_slicer (Apr 26, 2015)

dieselpilot said:


> 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.


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