Cam Grinder questions / suggestions

[werowance]

just contemplating a cam grinder. never used one and know very little about them. research is indicating that the gene switzer grinder plans are the ones most talk about that can be had from Strictly IC magazines. but here is where i kind of run into all my questions and such. i cant seem to find any decent photos of said grinder or how it works or any build logs. - not just for his grinder but for any mini grinder for that fact. im certainly not above paying for plans or anything but at this stage i dont even know if i would be capable of building one with my skillset yet. right now i use the boring head method but thought it would be nice to make solid 1 piece ground cam shafts. was thinking of maybe some sort of duplicator grinder and i just 3d print a cam as the master or something. at any rate im not asking for free plans or to copy copyrighted material or anything here. just looking to see some details of the simplest cam grinder anyone has built that maybe someone with my limited skill set could produce and if it looks like something i could make then i would be happy to purchase. one problem i have with magazine articles is they are often very dificult to follow and offten have mistakes in them. (even read on another forum where someone was trying to make Genes grinder from the magazine articles and was having the same issues. so maybe there are easier to build versions, with build logs or something so i can see how dificult the setups required would be and if i have whats needed to do it.
at any rate right now its just research that im doing.

 

[GreenTwin]

This is PeterL's cam grinder.

I have not built or used one, but I think I see how it works, and it does not seem too complex.

My guesses: (perhaps PeterL can chime in and give us first hand info on his grinder)

There is a round shaft at the base.
Above the round shaft is a U-shaped piece that resembles the ways on a lathe.

The support for the left end of the cam bolts onto the U-shaped piece, with a bearing to allow the cam to rotate.

One the right side is another support that bolts to the U-shaped piece, and that end has what looks like a locking collar.
Bearings on the right side also.

The entire U-shaped piece with the two support blocks, and with the low-speed drive motor pivot forward/back on the round shaft at the base.

There are two wheels on the right side.
The wheel towards the rear appears to be bolted stationary, and does not move, but I guess can rotate.

The wheel towards the front moves with the entire u-shape/supports/camshaft/slow-speed motor assembly.
The wheel towards the front is a large scale replica of the cam, and it has to be positioned exactly for the lobe that will be ground, before starting the grinding process.

I don't understand the terms "additive" and "multiplicative".

The stationary round wheel towards the back appears to be mounted on an arm that is pivoted at the bottom, so that it can swing forward and backward.
The micrometer pushes against a stationary piece that does not move.

If the round back wheel moves forward far enough, it keeps the cam profile and camshaft from making contact with the grinding wheel.
By adjusting the micrometer slowly, the back wheel moves towards the back, and allows the cam profile and camshaft to move closer to the grinding wheel.

I would recommend a shield on the grinding wheel, just in case it gets jammed and explodes.
Stuff does happen sometimes.

I am not sure about the size/diameter of the wheel and cam profile, or the relationship between the size of the two wheels.

I see how it works.
I could design/build one.
I don't know much about cams or multi-cylinder engines though; that is a whole new level, and I am not sure if I will ever reach that level.

 

[Charles Lamont]

There are a couple of pictures of my camshaft grinder about 2/3 of the way down this page:
http://www.charleslamont.me.uk/Seagull/camshaft.html

It was designed to be (reasonably) simple to build and (mostly) economical in materials, and geometrically accurate. It is mostly made of aluminium rectangular bar and plate and precision ground mild steel bar stock. I can go in to more detail if you are interested but I am not offering drawings.

 

[werowance]

This is PeterL's cam grinder.

I have not built or used one, but I think I see how it works, and it does not seem too complex.

My guesses: (perhaps PeterL can chime in and give us first hand info on his grinder)

There is a round shaft at the base.
Above the round shaft is a U-shaped piece that resembles the ways on a lathe.

The support for the left end of the cam bolts onto the U-shaped piece, with a bearing to allow the cam to rotate.

One the right side is another support that bolts to the U-shaped piece, and that end has what looks like a locking collar.
Bearings on the right side also.

The entire U-shaped piece with the two support blocks, and with the low-speed drive motor pivot forward/back on the round shaft at the base.

There are two wheels on the right side.
The wheel towards the rear appears to be bolted stationary, and does not move, but I guess can rotate.

The wheel towards the front moves with the entire u-shape/supports/camshaft/slow-speed motor assembly.
The wheel towards the front is a large scale replica of the cam, and it has to be positioned exactly for the lobe that will be ground, before starting the grinding process.

I don't understand the terms "additive" and "multiplicative".

The stationary round wheel towards the back appears to be mounted on an arm that is pivoted at the bottom, so that it can swing forward and backward.
The micrometer pushes against a stationary piece that does not move.

If the round back wheel moves forward far enough, it keeps the cam profile and camshaft from making contact with the grinding wheel.
By adjusting the micrometer slowly, the back wheel moves towards the back, and allows the cam profile and camshaft to move closer to the grinding wheel.

I would recommend a shield on the grinding wheel, just in case it gets jammed and explodes.
Stuff does happen sometimes.

I am not sure about the size/diameter of the wheel and cam profile, or the relationship between the size of the two wheels.

I see how it works.
I could design/build one.
I don't know much about cams or multi-cylinder engines though; that is a whole new level, and I am not sure if I will ever reach that level.

that one doesnt seem overly complex, not sure i would fully understand everything enough to build it without plans or one to measure by, but yeah that one looks like i might could do it.

 

[werowance]

There are a couple of pictures of my camshaft grinder about 2/3 of the way down this page:
http://www.charleslamont.me.uk/Seagull/camshaft.html

It was designed to be (reasonably) simple to build and (mostly) economical in materials, and geometrically accurate. It is mostly made of aluminium rectangular bar and plate and precision ground mild steel bar stock. I can go in to more detail if you are interested but I am not offering drawings.

Charles, thank you for sharing that. yall keep em coming please and thank you

 

[GreenTwin]

In short, it is a powered rotating shaft (camshaft) mounted on a hinge, and the pattern mounted on the right side of the hinge/shaft controls how far in and out the hinge moves towards the grinding wheel.

Easy to say than to build I guess, but it is not really a complex design in my opinion.

Getting the pattern in exactly the correct orientation with regards to the camshaft could be tricky.

Technically you could cut the camshaft on the lathe, with all the lobes round, and then grind your way down, but that would be an excessive amount of grinding.
So the cam lobes would have to be cut to a rough approximate shape before the grinding started.

I wonder if anyone casts their camshafts slighly oversized, and then final grinds them, such as with ductile iron.

.

 

[Charles Lamont]

There is some more info on my grinder here:
https://www.modelenginemaker.com/index.php/topic,9872.msg224859.html#msg224859
Couple of quick points not mentioned:
The cams are rough machined, hardened, and Loctited to the camshaft in the correct orientation before grinding.
The wheelhead, designed to suit a suitable 2700rpm motor I already had, slides along the lower bar to the position
of each cam.
The wheel guard was carved out of solid - there are other ways.

 

[gbritnell]

While I think a cam grinder is a neat and useful tool, to go to all the work to build one to grind one or two cans is a little overkill. It has to be built very accurately otherwise the cams being ground won't be.

 

[GreenTwin]

There is some more info on my grinder here:
https://www.modelenginemaker.com/index.php/topic,9872.msg224859.html#msg224859
Couple of quick points not mentioned:
The cams are rough machined, hardened, and Loctited to the camshaft in the correct orientation before grinding.
The wheelhead, designed to suit a suitable 2700rpm motor I already had, slides along the lower bar to the position
of each cam.
The wheel guard was carved out of solid - there are other ways.

I can't access that site, so I can't see it.
.

 

[werowance]

While I think a cam grinder is a neat and useful tool, to go to all the work to build one to grind one or two cans is a little overkill. It has to be built very accurately otherwise the cams being ground won't be.

well, the boring head way of doing cams works for me. i was just contemplating a multi cylinder engine and a sold 1 piece cam and i just dont see how i can do it without a grinder. but i also agree they look complicated to build, i was just hoping there would be a simple duplicator or something that i could just resin 3d print a master cam and then grind copy it.

 

[peterl95124]

I could probably be persuaded to clean up my plans enough that someone could use them

my grinder was inspired by Bob Hettinger's (BAEM Club member), it is based on the tilting bed type (the cam shaft moves), not the type where the grinding wheel moves, and mine uses the additive master cam (see Don Bell's article "Master Cam Design" in StrictlyIC Oct 1994) rather than the multiplicative (scaled up) master cam type (it looks like Charles' uses the scaled master cam type, his master cam is linked to the being-ground cam via cogged timing belt). I decided on the additive-master type after scouring StrictlyIC and other publications for cam grinder plans and didn't like what I saw (now seeing Charles' for the first time, that seems to be the best of that type and now consider maybe it too is worthy).

it was built around these parts: a DuMore mini tool post grinder that I already had, and a Sherline lathe bed that I found used on eBay. the DuMore wasn't designed for such large grinding wheels as I use, so I slow it down with a Variac.

the only part in the entire machine that is critical is the master cam itself, none of the other dimensions matter and none of the other parts have to be precision made.

I found that an additive cam is tricky to get right, glitches on its surface that are invisible to the naked eye on the master can show up as facets on the ground cam, so use a test bar to grind some test cams while fine tuning the master cam. Also somewhat to my surprise a new master cam has to be made for different cam base circle diameters even if they have the same lift.

I now make all my cams from A2 (air hardening) tool steel, we never need so much that cost is an issue and I've never had one warp during hardening (do so after turning into a cam blank but before grinding, hardened steel grinds better than soft), like I have with 4130 chrome moly. I also now use a CBN wheel and get through a couple entire cam shafts before it needs re-surfacing, whereas Alumina needs to be re-surfaced after a couple cams (IE a couple times per shaft for a inline-4 or inline-6).


so let me know if you're serious and if you'd like additional info, photos, and drawings.

 

[werowance]

I could probably be persuaded to clean up my plans enough that someone could use them

my grinder was inspired by Bob Hettinger's (BAEM Club member), it is based on the tilting bed type (the cam shaft moves), not the type where the grinding wheel moves, and mine uses the additive master cam (see Don Bell's article "Master Cam Design" in StrictlyIC Oct 1994) rather than the multiplicative (scaled up) master cam type (it looks like Charles' uses the scaled master cam type, his master cam is linked to the being-ground cam via cogged timing belt). I decided on the additive-master type after scouring StrictlyIC and other publications for cam grinder plans and didn't like what I saw (now seeing Charles' for the first time, that seems to be the best of that type and now consider maybe it too is worthy).

it was built around these parts: a DuMore mini tool post grinder that I already had, and a Sherline lathe bed that I found used on eBay. the DuMore wasn't designed for such large grinding wheels as I use, so I slow it down with a Variac.

the only part in the entire machine that is critical is the master cam itself, none of the other dimensions matter and none of the other parts have to be precision made.

I found that an additive cam is tricky to get right, glitches on its surface that are invisible to the naked eye on the master can show up as facets on the ground cam, so use a test bar to grind some test cams while fine tuning the master cam. Also somewhat to my surprise a new master cam has to be made for different cam base circle diameters even if they have the same lift.

I now make all my cams from A2 (air hardening) tool steel, we never need so much that cost is an issue and I've never had one warp during hardening (do so after turning into a cam blank but before grinding, hardened steel grinds better than soft), like I have with 4130 chrome moly. I also now use a CBN wheel and get through a couple entire cam shafts before it needs re-surfacing, whereas Alumina needs to be re-surfaced after a couple cams (IE a couple times per shaft for a inline-4 or inline-6).


so let me know if you're serious and if you'd like additional info, photos, and drawings.

im serious enough that i would definately like to see a few photos before going further. yours sounds more like what i had in mind but i will also have to say that what ive seen so far im afraid that im not up to the task. utilizing a used lathe bed and such makes it sound like it would be easier but then again i am now a little iffy on whether im up to the task.

Edit: i should also say that i really appreciate the time you and everyone has taken to show your solutions and such. it means alot to me.

 

[peterl95124]

im serious enough that i would definately like to see a few photos before going further. yours sounds more like what i had in mind but i will also have to say that what ive seen so far im afraid that im not up to the task. utilizing a used lathe bed and such makes it sound like it would be easier but then again i am now a little iffy on whether im up to the task.

Edit: i should also say that i really appreciate the time you and everyone has taken to show your solutions and such. it means alot to me.

first take a look at this video, then ask some questions, that way I'll know what parts need the most detailed drawings, FYI DoMore tool post grinder, 4" CBN wheel, variac for speed control, Sherline lathe bed, a micrometer head, ER-16 collet holder with long 1/2" straight shank, a couple XL pulleys and cog belt, some 3/8 ACME left hand threaded rod and delrin nut, everything else is bar stock,

 

[werowance]

first take a look at this video, then ask some questions, that way I'll know what parts need the most detailed drawings, FYI DoMore tool post grinder, 4" CBN wheel, variac for speed control, Sherline lathe bed, a micrometer head, ER-16 collet holder with long 1/2" straight shank, a couple XL pulleys and cog belt, some 3/8 ACME left hand threaded rod and delrin nut, everything else is bar stock,

some questions, what is a CBN wheel? griding wheel im sure but dont know what the CBM means, then on the cam blank, since its not a 1 to 1 copy, how do you actually come up with a blank that will do the end result? for the drive motor to rotate the cam - anything specialized on that? like hard to source or anything or is that perhaps the head of the sherline lathe? im trying not to be to pushy or dumb with my questios so just say shut up or go away if start getting that way.

 

[timo_gross]

While I think a cam grinder is a neat and useful tool, to go to all the work to build one to grind one or two cans is a little overkill. It has to be built very accurately otherwise the cams being ground won't be.

I think it boils, once again, down to the question if the grinder is the project or the tool for a project. And.... how many cams you want to grind.
It seems that it can be a useful tool for someone who is proficient and productive. For a (many) complicated engine it may be worth it?

Not too long ago there was a discussion about cams started by Brian Rupnow "tabletop CNC", some interesting input, as far as I remember also some video links to cam grinders.
https://www.homemodelenginemachinist.com/threads/tabletop-cnc.35934/#post-408294

 

[timo_gross]

some questions, what is a CBN wheel? griding wheel im sure but dont know what the CBM means, then on the cam blank, since its not a 1 to 1 copy, how do you actually come up with a blank that will do the end result? for the drive motor to rotate the cam - anything specialized on that? like hard to source or anything or is that perhaps the head of the sherline lathe? im trying not to be to pushy or dumb with my questios so just say shut up or go away if start getting that way.

CBN, Cubic Boron Nitride.

• rel. expensive, usually more expensive than corresponding diamond wheel
• nasty hard,
• aggressive cutting, (good thing, less heat in work piece)
• if treated with care lasts a long time and does not require as much re-dressing (difficult to re-dress in the home shop)
• Bonding methods, shapes and types are similar to diamond wheels. (Chinese re-sellers mix up CBN and PD/PCD (Poly-crystaline Diamond?) all the time resin bond wheels are sometimes called diamond. It ends up in descriptions like CBN diamond. )

I am following along, so I appreciate that you ask the questions that I do not dare to ask .

Greetings Timo

 

[peterl95124]

some questions, what is a CBN wheel? griding wheel im sure but dont know what the CBM means, then on the cam blank, since its not a 1 to 1 copy, how do you actually come up with a blank that will do the end result? for the drive motor to rotate the cam - anything specialized on that? like hard to source or anything or is that perhaps the head of the sherline lathe? im trying not to be to pushy or dumb with my questios so just say shut up or go away if start getting that way.

there's no such thing as a "dumb question" !!!

as you have by now noticed CBN is "cubic boron nitride", much longer lasting than alumina

I use the method of Don Bell in "Master Cam Design" StrictlyIC Oct 1994. basically you start with a 3-arc cam design, keep the centers of the three arcs in place but add the same constant 1" to each radius and re-draw from the original unmoved / unscaled centers and you end up with a perfect ~ 2" master cam. I'll photo copy the 1-page article if needed.

I made my own head stock and tail stock for the sherline lathe bed, the bores need to be either slightly taller than mine or slightly off center for a 4" grinding wheel to not touch the lathe bed,mine isn't offset and its always nerve rackingly close to getting ground. I have a third piece of dovetail that I can make into a steady rest if/when that becomes necessary,
but so far haven't needed one, not even for the long thin Merlin cam shafts I made (3/16" journals, 7+" OAL).

in the head stock is an ER16 collet that came on a 1/2" x 5" straight shank, which spins
in a bronze bushing in the headstock. You'll want to buy a small 55-deg dovetail cutter
to mill the headstock and tailstock to match the Sherline lathe bed. I found all of this on
fleaBay, my Sherline lathe bed was used (abused) and cheap, used might not be findable
anymore.

30 RPM (gear reduction) motors are cheap on fleaBay, I think they're used in microwave ovens so will never go out of abundance.

 

[petertha]

Chinese re-sellers mix up CBN and PD/PCD (Poly-crystaline Diamond?) all the time resin bond wheels are sometimes called diamond. It ends up in descriptions like CBN diamond.

I've noticed this same issue related to tool cutter grinder wheels. I have tried clarifying with seller beforehand but replies can be just as or more confusing. Someone told me the substrate for diamond is always that brick brown color but that may not be reliable indicator because I've seen them in other colors.

Anyways, my question: is diamond considered a bad choice for carbon/tool steel camshaft grinding, not so much for the grinding wheel aspect, but because it does something detrimental to the part surface? The wheel alters carbon at elevated temp or something like that? I never knew this was a thing until someone pointed out dressing HSS cutting tools with diamond was a no-no. What exactly is the issue, I'm still not clear. I guess regular AO type wheels would be OK if one could find the right size & dressing etc?

 

[werowance]

there's no such thing as a "dumb question" !!!

as you have by now noticed CBN is "cubic boron nitride", much longer lasting than alumina

I use the method of Don Bell in "Master Cam Design" StrictlyIC Oct 1994. basically you start with a 3-arc cam design, keep the centers of the three arcs in place but add the same constant 1" to each radius and re-draw from the original unmoved / unscaled centers and you end up with a perfect ~ 2" master cam. I'll photo copy the 1-page article if needed.

I made my own head stock and tail stock for the sherline lathe bed, the bores need to be either slightly taller than mine or slightly off center for a 4" grinding wheel to not touch the lathe bed,mine isn't offset and its always nerve rackingly close to getting ground. I have a third piece of dovetail that I can make into a steady rest if/when that becomes necessary,
but so far haven't needed one, not even for the long thin Merlin cam shafts I made (3/16" journals, 7+" OAL).

in the head stock is an ER16 collet that came on a 1/2" x 5" straight shank, which spins
in a bronze bushing in the headstock. You'll want to buy a small 55-deg dovetail cutter
to mill the headstock and tailstock to match the Sherline lathe bed. I found all of this on
fleaBay, my Sherline lathe bed was used (abused) and cheap, used might not be findable
anymore.

30 RPM (gear reduction) motors are cheap on fleaBay, I think they're used in microwave ovens so will never go out of abundance.

Thank you for the explanation - actually thank everyone for the explanations and advice. ill say this would sort of be more of a project for me and not just a tool. something that im just interested in and want to learn more about and think it would be nice to have one. so on the cbn wheel, do you think aluminum oxide wheel would work ok for the ocassional smaller cams? figured i would not do a tool post grinder but just make an arbor and belt drive a wheel with it. on the lathe bed, yep i was looking on fleabay and they arent cheap but then started thinking about perhaps a wood lathe bed. might give me the extra height and long enough. what are your thoughts of that idea? not sure i fully follow the master cam redrawing but im not at home right now so i dont have a compass to test redrawing one and see if i can do it by description or not. that said ill search for Don Bell and see if can find pictures of it being done or something in the mean time

 

[werowance]

also, just ran across another photo and it looks like the cam stock is hand rotated wtih a crank. any issues you all know of doing it that way? would eliminate some cost and initial work but might end up with a sore arm after a while of using it.