# 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


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## 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


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## 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


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## 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


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## ozzie46

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


  Ron


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## 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


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## 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


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## Maryak

dsquire  said:
			
		

> 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


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## 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


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## 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


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## 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


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## kustomkb

Achim, you have made a beautiful precision tool. 

Great work!  th_confused0052


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## 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


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## lee9966

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

Lee


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## arnoldb

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

Truly inspiring!

Kind regards, Arnold


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## 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


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## 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.


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## Brian Rupnow

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


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## Brass_Machine

:bow: :bow: :bow:

wow!

Eric


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## tel

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


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## minerva

Achim,
A beautiful example of toolmaking :bow:
I only wish I had the persistence to achieve such results, thank you for documenting the process
Kindest regards,
Terry


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## walker

Hi,
congratulations for the excellent work, an essential tool for finishing the cam internal combustion engines. I am also interested in the production of camshafts for micro motors, wanted to know if the design of this tool is available. I mean the dimensional drawings of all components that constitute it.
I await your reply, regards.
Ignazio


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## larry1

Achem,  Thank you for sharing this piece of art with us, This is a very great looking machine.   larry


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## metalmad

Hi Achem
This post is just what ive been looking for!
I recently bought a fellow model Engeneers shop tools and a Quorn was with it.
I have been thinking about setting it up as a Cam grinder with the Master behind the degree wheel in much the same way you have done but was worried about having the master 1-1.
It never occured to me that only the lift and duration has to be 1-1.
Thank you for the inspiration, I need to study this.;D
here is a pic of the quorn with the tailstock installed, and another with its box of bits.
Pete


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## Lykle

Hello Joachim,

After seeing this beautiful tool and looking over your website with even more wonderful machinery I can't help noticing that you use a lot of bronze. 
Why is that? Isn't that an expensive option? 
Don't get me wrong I think it is a wonderful combination and it makes your tools look absolutely beautiful. But I would hesitate just because of the cost.

Lykle


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## agmachado

Hi Achim and Pete,

Very cool your work!!!

Cheers,

Alexandre


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## cforcht

excellent work on the cam grinder. nice and simple, may have to make one some day. thanks for sharing.


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## ConductorX

I am totally in awe of the incredible work and precision of both machines and machinists.

"G"


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## chalee

hi sir achim can you tell if this capable of doing camshaft for scooter?single cylinder?because this is really a dream machine for me pls help me..


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## wallynfo

why isn't the master cam the same shape as the finished cam?


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## ICEpeter

Hello Wally,
Welcome here at this forum. Noticed you joined today but don't know much about you at this time. May be you could tell us a bit about you.

To your question: I must admit that I was stumped myself initially until I figured that when you make a scaled up master cam, you can not simply multiply the dimensions of the desired cam for use as the master cam to grind the cam. By scaling the cam profile by multiplying it by a factor of say 5, you will have a master cam that looks like the desired cam but when using it to grind a cam it will look a disaster.

The reason that the master cam shown in Achim's excellent thread looks distorted and not like the desired cam is, because in the scaling up of the master cam, you are not using multiplication but addition of certain dimensions. I have attached a sketch of a master cam that I made for use in a cam grinder based on Achim's design that will allow you to figure out how it was done. I also attach a picture of my cam grinder that I built inspired by Achim's design and concept which I shamelessly adopted. I give Achim full credit for that excellent design.

Peter J.


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## Rickl

Achim,

That is a great piece of work.  Thanks for letting us look at your work.

Rick from Sth Australia


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## wrljet

ICEPeter, 
Very nice.  Do you have any other pictures of your version of the machine?

What did you use for the X-Y table the grinder sits on?

Bill


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## ICEpeter

Hello Bill,
Yes I have other pictures. If you are interested I can send you via e-mail an information package I put together for five other HIMEM
members. To do that, I would need your e-mail. The package I 
have contains sketches / drawings / pictures and description of
the features I incorporated into the design. It also described
what I used for the X / Y table. Mind you the sketches and 
drawings are not CAD but pencil drawings / sketches.

When e-mailing, you will receive the information in 14 e-mails due to 
limitations in the package size my e-mail provider applies.

Sorry for the strange reply format. I experience the display 
problems other users are also having. Can not post or reply 
properly because of that.

Regards,

Peter J.


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## wrljet

Thank you Peter.  PM sent.



ICEpeter said:


> Hello Bill,
> Yes I have other pictures. If you are interested I can send you via e-mail an information package I put together for five other HIMEM
> members. To do that, I would need your e-mail. The package I
> have contains sketches / drawings / pictures and description of
> the features I incorporated into the design. It also described
> what I used for the X / Y table. Mind you the sketches and
> drawings are not CAD but pencil drawings / sketches.
> 
> When e-mailing, you will receive the information in 14 e-mails due to
> limitations in the package size my e-mail provider applies.
> 
> Sorry for the strange reply format. I experience the display
> problems other users are also having. Can not post or reply
> properly because of that.
> 
> Regards,
> 
> Peter J.


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## RManley

Hi Achim, amazing work and very inspiring.  Can you please explain why you have used a follower the same size as the wheel instead of a roller, does this stop inaccuracies creeping in?  

I am well on the way to having one based on your design and this is the final point.  

Kind regards, R


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## ICEpeter

Hello R..,
Although I am not Achim I might be able to answer your question. To get the answer, please read through Achims very first post about 1/3 through the first post is a bit of text that answers your question. Looking further down through the first post you will find a picture that corresponds to the earlier text where Achim shows the different shape follower he is using instead of the roller follower shown in an earlier picture. Hope this helps.

Peter J.


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## RManley

So, just to get my head around it, if it was a scaling system whereby the pattern was scaled down I could use a bearing cam follower.  But, as its a 1:1 system a large radius follower is needed. 

R


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## bluejets

We have the same problem with inaccurate reproduction on the cam in relation to the master.
It all comes from the geometry of the rocking action mechanism.

Two similar "rocking arm" machines were made here a few years back.
One with mechanical operation on the adjustments, cut depth etc.
The other with largely electronic "automatic" control.

The way it was overcome by George Punter was to make the "following mechanism" linear in motion.

The necessity came from the need to produce replacement complex cams from old motorcycle engines for which he has made a name for himself.

The outcome of the linear motion grinder is that a cam of "any" size can be made which is, as I said earlier, an exact reproduction of the master.


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## ICEpeter

Hello Jeff,
I am certainly no expert on the subject of cam geometry and the geometric closeness of a cam that is generated using a master cam in a swing frame grinder. 

The master cam I created for use in my cam / crankshaft grinder is five times the size of the actual cam that I needed to grind. My master cams were created in CAD and machined on a CNC mill and the master cam geometry was confirmed after machining.

If certain requirements in the design and building of a swing frame grinder are adhered to, it appears that the resulting cam being ground is very close to what the cam geometry requires. In testing my grinder initially, I made a cam ground to the 2 dimensions that could easily be measured during the grinding process such as base circle diameter and total cam height. These dimensions correlated to each other as per the cam geometry to within 1/2 thousands of the design geometry. After stopping the grinding at that point the cam was mounted to my lathe spindle in conjunction with a degree wheel and the cam profile was measured / compared to the design profile vectors and it was found that the vector length of the ground cam matched the theoretical design vectors within about a thousands of an inch. I figured that was good enough for me. So I left it at that and was satisfied with the results - kept on making my camshafts accordingly.

I am of the opinion that the cams I am grinding are accurate within close tolerances because the use of the oversized master cam being made using CAD and CNC reduces any geometrical errors during the grinding by possibly a factor of 5.

As I said I am no cam expert, maybe somebody who knows this subject better than myself can enlighten me. 

Peter J.


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## hanermo3

Absolutely !
You are using geometric scaling.

All machines, more or less, use the same ideas, to get better precision, resolution, repeatability and accuracy.

The same, even better, is common and used on modern cnc machines.
The support guide blocks are relatively far away from each other.
Say 500 mm midpoint (== 1 m bed VMC, typical, 45-55 mm linear guides).
Each might have an error of say 0.005 mm max.
But the midpoint will have much less error, => 0.002 mm, especially over 4 blocks.
This is geometric averaging.
You trade size and volume for accuracy.

The longer your lever arm//error, the lesser your error at the controlled point aka cutting tip.
In practice, it gets better since mass works for You, by always preloading (bias) in the same direction.
This is one way how it is relatively easy to make more accurate components, given some time, area, money for components, and a bigger machine.

It is quite easy to make a flat 2-5x more accurate, than the guide you have.
Similar applies to everything, including screws, that need special techniques.
e. Offset cam followers made 1 micron accurate screws 50 years ago.
SIP machines and Moore jig bores were the famous ones.

At that time it was very hard, and very expensive .. due to measuring mostly.
Today, it is vastly easier.

I spent 12-14 years so far learning to make very accurate cnc screws.



ICEpeter said:


> I am of the opinion that the cams I am grinding are accurate within close tolerances because the use of the oversized master cam being made using CAD and CNC reduces any geometrical errors during the grinding by possibly a factor of 5.
> 
> As I said I am no cam expert, maybe somebody who knows this subject better than myself can enlighten me.
> 
> Peter J.


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## Charles Lamont

The accuracy of the master cam is only one aspect of the matter. The geometry of the mechanism is also critical to its faithful reproduction.

Not long ago I completed a rocking frame grinder, shown here:  

http://www.homemodelenginemachinist.com/showthread.php?t=25362&page=7

 In a purely mechanical cam grinder, the geometry of the mechanism is crucial. My grinder provides the correct geometry by using the principle of similarity. (For those whose maths may be a little rusty, that is things of identical shape but scaled to different sizes.) 

Firstly the master cam is scaled up by a factor of 5, and works on a 5:1 ratio of arm length.

Secondly, the follower shoe for the master cam has a radius 5 times that of the grinding wheel.

Thirdly, obviously, the grinding wheel and follower are mounted at a 5:1 ratio from the rocker pivot.

Finally, and this is the crucial step that ensures the geometry remains correct, missed in several designs I have seen, the contact points ("top") of the follower and wheel are in a straight line with the pivot point. In my grinder this is achieved by setting the pivot point at the same height as the top of the wheel.
Any deviation from this straight line would result in the 5:1 arm length ratio being compromised, and probably other errors I have not bothered to think through. 

The height of the follower is adjustable to provide the depth of cut, but it ends up the same height as the top of the wheel when the cam is to size.

This geometry is straightforward and fairly easy to understand, though also quite easy to misunderstand. It would be perfectly possible to design a rocking frame grinder that used a flat follower shoe, but, for accuracy, that would require the master cam profile to be modified in a way that I did not want to spend time getting my head round.


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## bluejets

bluejets said:


> The way it was overcome by George Punter was to make the "following mechanism" linear in motion.
> 
> The necessity came from the need to produce replacement complex cams from old motorcycle engines for which he has made a name for himself.



As I said, I not knocking the design. My grinder follows the same as yours and it is quite satisfactory for the work.

What I was pointing out for any who may come along later, that there is an alternative that will produce "exact shape" cams of "any size" from "any size" blank. The one George punter built will do exactly that.


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## ICEpeter

Hello Jeff (I assume that is your correct first name, if not I apologize),
As the saying goes, there is more than one way to skin a cat (Apology to the cat)

As long as the method and equipment used accomplishes the desired result regardless of the approach, its goal was reached and it can be considered a success. I wouldn't rate one or another approach inferior or superior in comparison because of the ingenuity of us model engineers we travel different roads to get to the same destination. Cheers.

Peter J.


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## john_reese

A truly beautiful job.  Did you build the tool & cutter grinder?


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