Another Cam Grinder

[Joachim Steinke]

Hallo everyone

My first IC engine operates with a sleeve valve, so I wasn’t in need of making cam shafts in the past. Now, being busy in the design phase of some new IC projects, I had to think about a suitable way to build my own cam shafts in future.

My plan is to make the shafts from silver steel (ore alternative a special sort of hardenable high strength free cutting steel), harden them after finishing all the turning jobs and then grind the lobes out of the full round blanks. My cam lobes won’t get more rise than max. 2mm (0.08in), so grinding without pre forming them on the mill should work well enough.

After reading a lot of articles on the web I decided to build a cam grinding attachment that can be mounted on the cross table of my universal tool and cutter grinder. This self designed grinder is only a tiny table top machine, but I build engines in the scale of 1:5 (eventually 1:4) and the dimensions of the required cam shafts are just small enough to fit in the limited work space of my grinder.

The design is based on a pivoting frame containing a headstock and an extension arm made of 15mm square steel bar which supports a small tailstock. The 8mm headstock spindle is driven by an Escap gear motor using a MXL tooth belt. So the whole construction is much like a very small (and simple) watchmaker lathe.

With this layout I have a maximal working length of 75mm (3in) between the cone points. The cam shafts will be fixed by a small lathe dog, so you can take them out temporarily (for measuring ore inspection) and put them back without loosing the rotary position.

A diamond wheel dresser is placed on the head stocks midsection using an adjustable clamping fixture to assume the needed dressing angle.

Instead of using a spring load I will use a rocker arm containing an adjustable weight for pressing the master lobe against the detector curve. I think this gives me a better control of the required force as the pressure is also needed for a suitable grinding contact. If it will not work to my wishes I can switch over to a spring system later on.

The cam shape is copied from a master lobe which is mounted on the left side in front of a division plate. With this plate I can adjust the offset on multiple lobed cam shafts.

Normally I will use a master with the same lobe rise as the finished product but with a greater main diameter, so this will be no lobe scaling system. The masters can be done in the common way on the milling machine from thicker brass sheet for example, but I think I will make them from 4mm laminate board on my CNC router.

Instead of the ball bearing as a cam follower I use a curve in the diameter of the grinding wheel now, the sampling error of such a small roll is too large which undercuts the side flanks besides the lobe tip.

And here some impressions how the fixture fits on my grinding machine:

Sadly I’m not able to report of first grinding experiences because the fixture is not finished yet. But I started working on it some days ago, as you can see on the first rough pictures (poor quality) I could take this evening:

So the tailstock is the last major component to build and I will continuo this report in the next days and hope to come back with some good results on a first test cam shaft…..ha ha ha….

Achim

 

[Joachim Steinke]

Well, the small grinding attachment could be finished today and I was able to grind my ever first cam shaft……hooray…..

But I should tell the rest of the story step by step.

After building the missing tailstock and some other minor details the complete fixture was finally ready for operation. I think the pictures are more or less self explaining:

And here you can see how the fixture is mounted on my grinder:

This is the diamond dresser moved in its working position:

Before staining the brand new and still clean components with this evil grinding dust I made this more clinical video of the basic functions….ha ha ha….:

http://pl-hi.de/JST/Cam-Grinder/Cam-Grinder_01.mpg

Then, for the first grinding test, I prepared a small cam from hardenable free cutting steel (ETG100).

After harden the cam bar with the propan torch and quenching it in oil the grinding test could be started. As I still haven’t build a dust extraction system the whole machine base was covered with some leather cloths so the table slides get at least a little protection.

I could say that the whole grinding process is working very well, no vibrations, very good abrasion and the machine is running very quietly.

The infeed can be done in two different ways. You can feed the cross table slowly and constantly by hand following the need of the grinding contact, this you can see on the video here:

http://pl-hi.de/JST/Cam-Grinder/Cam-Grinder_02.mpg

Or you can adjust the whole cam elevation at once (but leaving a small rest for the final finish and precise diameter operation) and let the machine do the work all alone. In that case the pressure against the grinding wheel is limited from the ballast lever and its suitable adjustment.

You can have a look at this sort of operation on the last video here:

http://pl-hi.de/JST/Cam-Grinder/Cam-Grinder_03.mpg

I must say the results are really nice, a smooth and clean surface and no problem to achieve precise measures.

The only spot of bother are some small skews on the surface. They are a result of the crooked handmade wooden master lobe that I had to use for the testing today. But this will vanish with the CNC milled masters I intend to make for the operations on the real cam shafts later on.

So one of the sticking points on the way to the new engine concept is out of way and the final designing can go on….ha ha ha….

At last a picture of the lobe profile I used today and how the scaled up master is designed after it.

Achim

 

[crankshafter]

Hi achim.
178wiews on this topic so far and no replys ???.

Really nice work( as allways) on that camgrinder. There have been so much posting regarding camgrinders/ plans but no one have come up with much yet. So your contribution is very welcome.
The surface-finish on everything you make are first class/ superb :bow: :bow:

Best Regards
Crankshafter

 

[crankshafter]

Hi again achim.
You beat me on posting ;D ;D
Your last post, only have to say :bow: :bow: :bow: incredible
Do you have plans on the grinder.
Think maybe you could adapt/mod. a benchgrinder to do the grinding?
Best
Crankshafter

 

[ozzie46]

All I can say is :bow: :bow: :bow: :bow: :bow:


Ron

 

[dsquire]

achim

Another very fine piece of equipment you have designed and built. The way that you present your work and the detail in the photos is outstanding. Thanks very much for sharing it with the members here. :bow: :bow:

Cheers

Don

 

[cfellows]

Very nice piece of equipment. I find myself looking at it trying to figure out how to make it into a tool & cutter grinder!

Chuck

 

[Maryak]

achim

Another very fine piece of equipment you have designed and built. The way that you present your work and the detail in the photos is outstanding. Thanks very much for sharing it with the members here. :bow: :bow:

Cheers

Don

Absolutely, I'm Gobsmacked. :bow: :bow:

Best Regards
Bob

 

[moconnor]

Achim,

Thank you for sharing your cam grinder design with us. It is an outstanding piece of engineering. What strikes me most as I look over all of your work that has been presented here is the elegance in simplicity you achieve. I am certain that you have given many builders the inspiration to build their own cam grinder, which is one of the most daunting tasks in constructing a miniature engine.

Thanks again. I look forward to seeing the engine design that this cam grinder was a precurser to.

Kind regards,
Mike

 

[GailInNM]

Achim,
Beautiful work. The cam grinder is a work of art and so is the test cam that you cut with it.
Thank you for sharing it with us.
Gail in NM

 

[Joachim Steinke]

Hi and many thanks for your interests and warm appreciation.

And to Crankshafter and his questions:

Sure one can realize this with a bench grinder instead of using a universal grinder. I have this plan in reserve if the grinding dust on my tiny tool grinder will drive me nuts some day.

But to arrange things convenient for operation, a fixture like mine needs in minimum one precise linear slide for the infeed towards the grinding wheel. Okay, one can try to handle this infeed with a small adjustment slide directly on the master fixture, but this will make things very limited, as the grinding wheel is getting smaller from grinding and dressing.

So with the only infeed via a master adjustment the pivoting frame will get more and more out of a perpendicular position and that brings the rotation centre of the cam more and more under the centre of the grinding wheel which will create a growing profile irregularity. Using new wheels each time for only a handful of jobs is one solution, but I think no one will do this. Or you can mount the fixture with slotted holes on a base plate and fix it new from time to time, what is a matter of taste and I personally would not prefer this either.

Next is the movement in X direction along the cam shaft. I will not claim that without having this option cam grinding is impossible, but there are some reasons for having this opportunity. For grinding multiple lobed shafts you have to transverse more or less precisely from one lobe to another. And it is very useful if one can travel a little bit from one side to the other over the wheel surface while grinding, so you have to dress the wheel less frequent which saves wheel diameter (and time…..ha ha ha…) Fortunately I had made a lever operated slide combined with two table stops for my machine what makes this things extra convenient in that case.

So, to my opinion, the best way to get things combined with a normal bench grinder is to use a small cross table and mount them both on a robust base plate. I still have one of the same cross tables as on the existing tool grinder in stock here, just for this purpose.

And to your question about publishing some plans:

As mentioned in other articles before I design my projects exclusively in 3D CAD and work directly with the solids out of the computer. That means I don’t have working drawings that can be easily published nor will another person understand my cryptic prints as they don’t relate to normal standards of mechanics. Understandable drawings should be produced first and I don’t have always the time to do this, but maybe I can do it over the next weeks.

Achim

 

[kustomkb]

Achim, you have made a beautiful precision tool.

Great work! th_confused0052

 

[gbritnell]

Hi Achim,
Well as usual you've outdone youself. Your cam grinder is so beautiful I had to go over the pictures several times to take it all in. To heck with making cams, I like the grinder.
I'm sure this tool will provide you with some great camshafts.
I would like to thank you for the outstanding projects and information you provide to this forum. We can all learn from your craftsmanship.
George

 

[lee9966]

Very nice work. Your machines are very nicely made! A nice design too. Thank you for sharing your work with us.

Lee

 

[arnoldb]

Achim, that is beautiful toolmaking of the highest order :bow: :bow:

Truly inspiring!

Kind regards, Arnold

 

[mh121]

Hello Achim, that is one beautiful piece of design and machining. Thanks for sharing it, nice to follow it from design to finished article. :bow:

Cheers,
MartinH

 

[crankshafter]

Achim
Here I am again ;D

"So, to my opinion, the best way to get things combined with a normal bench grinder is to use a small cross table and mount them both on a robust base plate. I still have one of the same cross tables as on the existing tool grinder in stock here, just for this purpose."

This is exactly what I was thinking :idea:but don't write in my post. (was kind of tired last night,the flue-season is here )
Nice videos/pics.
Do we see a crankshaft-grinder in the future : ;D ;D

Regards
CS.

 

[Brian Rupnow]

My Goodness!!! What a beautifull peice of engineering. I admire your inventiveness and machining abilities.----Brian

 

[Brass_Machine]

:bow: :bow: :bow:

wow!

Eric

 

[tel]

That is very impressive - beautifully built and beautifully photographed, inspiring stuff!