Boyar-Schultz 612 surface grinder belt conversion WIP

Bob Ohlemann

Bob Ohlemann

Joined
Dec 5, 2013
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1,180
I had another thread on my thoughts and exploits leading up to and acquiring my surface grinder. It can be viewed here if you're interested.

http://www.bladeforums.com/forums/showthread.php/1168232-Surface-grinder-options-Wuertz-attachment-or-modify-a-dedicated-grinder

I ended up buying a exceptionally clean, low mileage Boyar-Schultz 612 manual grinder. It was my intention, from the beginning, to modify the grinder for use with 2x72 belts. After getting the grinder home and setting it up, I used it for a while with grinding wheels to evaluate the machine and develop some grinding knowledge. Since others expressed interest in how I was going to do the belt conversion and because there was not a lot of info available for me to draw from, I agreed to do this work in progress on the conversion. My original plan was to complete the conversion before beginning the WIP thread. I've made a fair amount of progress thus far but have not completed the build. When my contact wheel showed up the other day, I decided that I would start the WIP so those who are interested don't have to wait for me to finish to see where I'm going with the build.

Here's the grinder in the back of my truck when I got it home.

Boyar-Schultz 612 by Ranger_Bob, on Flickr

This is the technical drawing Sunray sent me after I specified what I wanted. You will notice that the wheel is only 1.125" wide. I decided that since my grinder is only 3/4hp, I would split my belts to reduce the contact area and put less stress on the spindle bearings.

6 x 1.125 Contact Wheel by Ranger_Bob, on Flickr

This is a model I did in AlibreCAD. This arm will clamp to the machined portion of the spindle housing where the wheel guard normally resides. The entire arm and contact wheel can be removed, thus returning the grinder to original configuration. I will post the technical drawings for each part as I get to it.

SURFACE GRINDER BELT CONVERSION by Ranger_Bob, on Flickr

These are the components I had to order for this build; an adjustment knob (yes, I could have made this too), a shoulder bolt for the idler wheel, and a high tension spring. The springs don't look like much but will exert right at 80lbs with one inch of compression. They only came in packs of six.

Untitled by Ranger_Bob, on Flickr

One more component I had to order. Took four weeks from order to ship. Sunray has a selection of colors. I liked orange!

Sunray contact wheel by Ranger_Bob, on Flickr

To be continued...

Bob
 
First up is the clamp sleeve that mounts the arm to the spindle of the surface grinder. In the drawing you will see a 1" hole. I was having trouble getting things to align in my model so I added that. It is not drilled into my clamp as you will see.

clamping sleeve by Ranger_Bob, on Flickr

First I cut a length about .050 longer than needed so I could face and true the ring. This is 3.5x.250" DOM 1018

Cutting a peice of tube for the mount by Ranger_Bob, on Flickr

Machining the ends and boring the inside diameter to 1.125.

Opening the bore to size by Ranger_Bob, on Flickr

Next I cut out, marked and drilled the tabs that will weld to the ring to tighten it down.

making clamp tabs by Ranger_Bob, on Flickr

After drilling the holes, I bolted the tabs together with a washer in between. The washer provides the gap needed to get a tight pinch when clamped on the spindle. I also contoured the tabs to get a good fit with the ring.

tabs fitted to tube by Ranger_Bob, on Flickr

I left the tabs bolted together while I welded them to the ring.

tabs welded by Ranger_Bob, on Flickr

Next, I removed the bolts and washers. I took the assembly to the bandsaw and cut through the area between the two tabs.

opened up on the bandsaw by Ranger_Bob, on Flickr

Here is the clamp fit to the spindle of the grinder.

fit to the spindle by Ranger_Bob, on Flickr

Stay tuned kiddies, more to come.

Bob
 
Next is the rocker that will hold the idler wheel and adjust tracking. Here's the drawing.

SGROCKER by Ranger_Bob, on Flickr

It is made from a solid chunk of 1.5x1.5x3.75 1018 steel. Since I didn't have any 1.5" square bar on hand I cut it from a bigger bar.

Cutting a block for the rocker by Ranger_Bob, on Flickr

I then split that piece to get the rocker and the cap that will hold the adjuster screw.

Slitting the block by Ranger_Bob, on Flickr

I failed to photograph a couple steps here. I cleaned the rust off on the belt grinder then squared up the block on the surface grinder using a standard wheel. I then took the block to the mill and drilled a 1" hole which I then enlarged to a slot with a 1" 6-flute cobalt endmill.

Idler rocker slotted by Ranger_Bob, on Flickr

I drilled and tapped the hole for the idler wheel shoulder bolt. It has 3/8-16 threads. Not a very good picture; I was power tapping this thing and holding my phone with my left hand to snap the pic.

Drilled and tapped for shoulder bolt by Ranger_Bob, on Flickr

This is pretty much where this piece is right now. I cross drilled the 1/4" pivot holes and I started cutting the 20 degree cut off the bottom on the bandsaw. Cutting metal this thick it somewhat arduous so I'm just hitting it for a few minutes at a time. Once I complete that cut, I will clean it up on the mill.

Bob
 
Cool stuff RangerBob!
Converting my SG is on the to do list.
The choice to split belts doesnt have so much to do with horsepower but how much longer it takes to walk a 2" wheel over a part compared to 1"
Can you talk about why you would get one made to 1.125" as opposed to simply just 1"?
 
I just bought a Boyer- Schultz 612 too, and was also on the fence about converting it to a belt. I love the fact that you are making this convertible- best of both worlds. If it works, I may try the exact same thing (hopefully you don't mind borrowing your idea) This is going to be great WIP!
 
I went with a 1-1/8" wide contact wheel because belts sometimes have a little side-to-side play in them. I figured that having a little extra shoulder would keep the belt well supported.

Anyone is welcome to use all or part of this WIP for their own build. That is why I am posting my drawings. Of course, these drawings are for my reference and I make absolutely no claims to their accuracy or suitability for anyone else's build.

Bob
 
Thanks for sharing Bob. I am following this closely since I am about to receive my contact wheel and when time permits, work on my own conversion.
Of course your machining (and welding...pwety!) makes mine look like it was done by epileptic monkeys. :o ;)
 
Okayyyyyyyyyyyyyyyy then...............

Thanks for sharing this in such stunning detail. I'm going to do my Boyar Schultz 612 soon too. I've discovered a neighbor who is a racecar enthusiast with a 4 car garage shop who welds madly and I'm working on a deal to get access to his shop and maybe even some guidance. That, along with this thread and a host of others out there will make a belt conversion a doable thing for me to do.

I can't wait to see how this all turns out Bob. Gorgeous contact wheel btw.

Corey
 
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I finished cutting the angle on the rocker. I threaded in the shoulder bolt to give me a little extra handhold while cutting.

Untitled by Ranger_Bob, on Flickr

I decided after cutting it that I would just take it to the surface grinder and save myself an operation. Since I don't own a sine vise or plate, I clamped the part into a machinist vise using a pair of angles (15° & 5°) to get my 20° angle. I tightened it down as tight as I dared and hoped it wouldn't slip.

Untitled by Ranger_Bob, on Flickr

I ran a few heavy passes of about .002" to hog off the rough stuff then worked down to a final pass of .0002".

Untitled by Ranger_Bob, on Flickr

I will most likely paint these so I probably don't need to get too crazy on the finishing. This part is done.

Untitled by Ranger_Bob, on Flickr

Bob
 
This is how I determined the center-to-center distance for the wheels so I could determine the length of the tubing I would need. The four inch round is going to be my idler wheel and I used a six inch grinding wheel because my contact wheel hadn't come in yet. I believe the measurement was 22.5".

Measuring height by Ranger_Bob, on Flickr

I'll be using 1.25x.120" DOM for the main tube and 1" 1018 bar for the sliding end that will hold the rocker/idler wheel assembly.

Bar and tube by Ranger_Bob, on Flickr

The fit of the spring is close but there's not as much support as I'd like so I decided to add a spring perch.

Spring slop 1 by Ranger_Bob, on Flickr

I turned the perch from a length of 1.5x.125" DOM.

turning a spring perch by Ranger_Bob, on Flickr

I also cut a little notch on the end of the main tube so the I.D. of the spring would register on it and eliminate slop.

Step for spring by Ranger_Bob, on Flickr

Spring perch on the tube and spring pressed over the registration notch. I will drill the perch and rosette weld it to the tube.

Spring on seat by Ranger_Bob, on Flickr

Bob
 
I think this post will catch up to everything that I have already completed and it is pretty brief. In order to keep the 1" rod from twisting in the main tube I will slot the tube and have two 5/16" shoulder bolts that are tapped into the bar riding in the slots. You can see the slots in the model at the beginning of this thread. When I've completed these components and determined that they work properly, I will post accurate drawings for them as well.

Here I have placed my super spacer on the mill table and clamped the tube into it. I've left the spacer mounting bolts just loose enough that I can bump it around with a mallet. I chucked the dial test indicator into the spindle and locked the spindle. I adjust the position of the spacer until there is no movement on the DTI across a couple inches of X travel.

indicating the outer tube for slotting by Ranger_Bob, on Flickr

After locating center of the tube, I center drilled and drilled two pair of 5/16" holes indexed 180° apart. I then ran the slots with a 5/16" 4-flute endmill. The entire slotting operation would have been easier if I had a tailstock to support the end of the tube. I had to take things pretty slow due to vibration and the cut suffered a bit in quality of finish. I need to buy a tailstock.

slotting by Ranger_Bob, on Flickr

So, I think this is everything I have done up to now. I will get some shop time over the next few days so stay tuned for updates.

Bob
 
The next piece I decided to do was the top cap that holds the tracking adjuster knob. I cleaned it up and squared it on the surface grinder. I then took it to the mill to bore and ream the 1" hole to get a good fit to the shaft. I recently purchased a 63/64ths inch silver and demming drill because I often need to ream 1" holes and it is really pushing it to get the reamer through a 15/16" hole. I pre-drilled with a 5/16" and then pulled out the new 63/64". As I started drilling the hole, I thought the hole seemed big. I looked at the drill's case and again verified that it was the correct size. When I finished drilling the hole I checked the size of the bore... CRAP!

I don't know if you can make it out but the drill actually has 1-9/64 stamped into it. Aaaarrgghh!

Untitled by Ranger_Bob, on Flickr

So, I started over. I cleaned this piece up on the disc grinder and called it good enough. Drilled it out to 15/16" and then carefully ran the 1.001" reamer through. Also drilled and tapped it for the 3/8-24 adjuster knob and a 3/8" cross bolt to hold it on the shaft.

Untitled by Ranger_Bob, on Flickr

Next, I needed to bore the holes in the shaft to mount the rocker and the cap. In order to keep alignment between the holes, I placed the shaft through a 5C collet and tightened it into a square block.

Untitled by Ranger_Bob, on Flickr

I also needed to drill and tap the hole for the locating shoulder bolts that ride in the slots.

Untitled by Ranger_Bob, on Flickr

The tapping was going fine. I had run a spiral point tap through the hole but, it didn't reach all the way through the 1" shaft. I ran a longer bottoming tap through to finish it out. Just before it finished the hole...BAM!

Untitled by Ranger_Bob, on Flickr

I spent about an hour trying to get it out but in the end, I had to move the hole a little further up the shaft. It won't affect anything since the top spring perch isn't yet set.

Untitled by Ranger_Bob, on Flickr

At the end of a very long afternoon; mocked up.

Untitled by Ranger_Bob, on Flickr

Bob
 
Bob,
Thank you for posting this informative and detailed thread.
Do you plan on making only 1" wide knives? My experience with surface grinders is limited, I just think it would be easier to run a 2" belt so I could clean up to a 2" piece in that pass. What are your thoughts on why the just over 1" belt will work better for you?
 
Laurence, I don't have a lot of experience with surface grinders either. I did a little grinding on one a few decades ago and I've got maybe twenty hours on this one. The problem with taking wide cuts on the SG is the heat buildup. A thin piece of steel, such as a knife blade, can warp very easily with the amount of single side heat buildup you would get. With a vitrified wheel, on a big block of steel, .200" is about the max stepover width that I feel comfortable running and for finishing passes, I'll go down to as small as .050" stepover at .0002" depth of cut. I'm not saying that I'm doing it 100% right but, I have done a lot of research and I think my technique is pretty standard. It's really easy to know when you're doing it wrong because the piece will burn and/or warp. I am always open to suggestions on how to improve my processes though so, if anyone has any comments, let's hear them.

Thanks for all the positive feedback guys.

Bob
 
I run a 1in wide belt. If your grinding a 1in wide piece of steel with a 2in wide belt then it takes you much longer to travel over the piece.
 
Chuck Gedraitis Knives said:
I run a 1in wide belt. If your grinding a 1in wide piece of steel with a 2in wide belt then it takes you much longer to travel over the piece.
Click to expand...

Hello Chuck, How are you doing?
OK? I'm not getting why it would take longer with a 2" wide belt to clean up a 1" wide billet or blank?
Doesn't it take longer to have to stop, break your magnet hold, move the piece over to get the rest of it cleaned up to size?

R Bob, I had a 2" wide belt converted SG running in my shop for just a few weeks, It belonged to another maker. I suggested and we used Accu-Cool grinding fluid in a squeeze bottle to keep the steel cool. It worked.
I would give it a good squeeze before each light pass. The stuff is Biodegradable and without sulfur. I only was able to spend about one hour on it, but it convinced me as to how handy it could be for knife making.
 
If you want to be at all accurate you cant just pass a 2" belt over a piece and call it done.
You have to walk it the whole way over, and a 2" belt means you have an extra inch to walk off the part.

Additionally I think you'd see a greater difference in wear from the back to the front on a 2"
Very easy to split a belt anyway
 
FTO_Dude summed it up. From my point of view as a folder maker I am not dealing with huge blades so a 1in wide belt works well for me just because of all the extra passes it takes to get a 2" belt off of the part
 
FTO-Dude & Chuck,
OK, that makes sense, I make blades that are 1 1/4" to 2 3/4" tall at the heel, So I will use a 2" wheel someday on my SG. Thanks.
 
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