Monday, October 10, 2011

Well it's finally done. Actually it was done a week ago, but I've been so busy I haven't had a chance to post. So I am going to do the update now. I have been using it for the past week, quite a bit actually, and it's been working great!

After completing all of the parts, and before installing them I painted them.


The picture doesn't show a lot but if you look close you'll notice the knife itself is missing from here. Because once I got home I checked the width of the knife against the width of the blade. The knife was .135" wide and the saw blade teeth are .120". This was not good, so in order to flatten it I tried running it though my drum sander. That didn't work to well, because after 2 hours of sanding it was down to .130". But fortunately we have a surface grinder at work. So the next day I stayed late and ground down the blade to .110". I planned to paint the knife and figured a little thinner is better than thicker. And with the paint on it's .115.


Now that that was taken care of, the first thing I had to do was to mount the pivot ring. In order to get it centered I turned a stepped cylinder on my lathe.


The smaller end fit's in the arbor hole, and the larger end is the same size as the pivot ring. I slipped this into place and marked the holes on the yoke (I turned it a touch to small hence the tape).



I then drilled the holes for the screws and tapped them for a 10-24 screw.


With the screw holes in place I mounted the ring, and fortunately it came out to be in the center (It looks like the entire ring is painted in this shot, but only the face where the screws are mounted is painted. The parts of the ring and mating flange that touch were masked off and left unpainted.


I then quickly found out that I had to remove the ring to get the retainer behind it. Then I mounted the flange and the retainer. I spun the whole thing a few times to check for interference from other parts and happily it cleared everything.


Then I installed the adjustable arm mounting bracket.


And then the arm.


This is actually an after picture. with the arm installed I found first that I had drill the pivot hole in the wrong location. I must have moved the table on the mill in the wrong direction from my marked point, since the hole was 1/8" above the line when it needed to be 1/8" below the line. So I flipped the piece and re-drilled the hole on my drill press. The arm also hit the letters that were cast into the yoke (visible just below the arm in the above pic) and the yoke casting also flared out a lot from the pivot point and I had to grind some of the arm away to clear these two obstacles. But after that everything moved freely and apparently level.

So the I installed the arbor assembly.


And the next part was probable the hardest part of the entire installation. Putting on the belts. I used a car jack to lift the motor after the retaining bolts were loosened. When installing the belts and lowering the motor I found that the motor had to be perfectly level to the arbor or 1 of the 4 belts would be slack. I had always intended to put the original belts back on, since I remembered them being in good shape when I took them off. But after looking at them when the time came, they were in pretty rough shape. So after calling every place nearby that carries belts, I found that no one had 4 in stock. Actually no one had more than 1 in stock. So I drove to Woodcraft and picked up some link belt. I like link belts since they do a great job of eliminating vibration and they are always the correct size. but they are overkill on this saw since it never vibrated anyway. but here's the arbor in place with the belts on.


I gotta admit it does look pretty cool with those belts on though (of course you can't see them with the top on).

Next was the knife arm.


At this point I pulled out my Wixey angle gauge, zeroed it with one of the cross members and put it on the far end of the arm. I then adjusted the pivot point of the arm up and down and forward and back until I had it pivoting (almost) perfectly. Whenever I would tighten the bolts it would go out just a hair, but when all was done it was only off .8 degrees through it entire rotation, and this is most likely due to the pivot ring not being perfectly centered. but that only translates to .018" of a difference in height of the knife which is about 1/64" so I can live with that.

At this point I put the blade on the arbor and knife on the saw. I had to do a little grinding for clearance from the blade, and shorten it's height just a tad. I also ground a bevel on the front to have a knife edge so the wood would not hit an abrupt edge. So when when I was done it was about 1/8" from the blade, and about 1/16 lower than the top. The split in the arm worked really well, I had to fuss with back of the arm a little to get the knife perfectly aligned with the blade. And the oversized hole design allowed me to do that easily. The knife holding mechanism works great as well. 1/4 turn and the knife comes out. But since this works the way a riving knife should, I will only be removing it when I put my dado stack in.

video

Awesome! So at this point I put the top back on adjusted everything and here it is:


I repainted the knife after taking the picture and forgot to take one after that. But the knife works perfectly! it goes through the entire range of motion of the saw, tilting and up and down.

And after using it a little, I actually had a piece of wood close up and pinch the knife! The blade spun like the wood wasn't there, and I was able to safely shut down the saw and remove the wood. This wasn't something I was trying to do, but not only does the knife work going up and down while hugging the blade but it also works as the safety device it's supposed to be!

So all in all this was a huge success! I have about 40 hours in the design, and another 40 hours in the building of the pieces. I am a much better machinist that when I started (I'm still not that good but better than when I started).

I'm very happy with all of this in every way, and now I'm happy to get back to real woodworking. The next thing I plan to make is an overhead guard that hangs from the ceiling with dust collection built in. I also have to work on the dust collection in the saw, but I was anxious to get back up and running so that will be sometime in the future.

If you decide to build one of these and have any questions let me know.

Thursday, September 29, 2011

Just about done. I did a little clean up and drilled a few holes after the picture was taken but here are the parts basically done. (I don't know why it's rotated blogger keeps spinning it)


I am waiting for larger shoulder bolts to come in. I accidentally drilled the holes in the link arm a little to big so instead of 1/4" shoulder bolts I need 5/16". Not a big deal but a few days of waiting. I took all the parts home last night and will clean them up tonight and paint them. I need to mic the riving knife and the table saw blade to make sure the knife is not to thick. If it is I plan to run it through my drum sander a few times to thin it out.

I'll snap a few pics tonight as I work on it. I hope to get it installed this weekend. If everything goes as planned I'll have a working riving knife by Saturday evening. If not well...

Friday, September 23, 2011

I'm still working on it.

I've still been chugging along. I am almost done, the two mounting blocks are left and a few holes to drill. I hope to be done by the middle of next week.

The one thing I definitely learned while doing this is metal work is so much slower that wood work, and only getting about an hour and half a night makes for slow going. I've made a few mistakes none that really affect to much, but I'm getting more familiar with the machines and the techniques.

I have gotten a few emails asking about the sketchup model, and for a copy of it. I will be happy to post it for anyone who wants it. But I need to clean it up first. Look for it in a week or so.

And also the thing to remember is that this is for a 12"-14" (34-350) table saw. For the most part it's the same as the 10" unisaw, but the parts for the 10" are smaller, so if you decide to make one of these you'll have to scale the model down.

If someone does make one of these for the the 10" and wants to share their model I would be happy to post it here or link to it.

Thursday, September 15, 2011

Progress is happening

A lots been happening in the last few days. I've been busy working on the knife, so I haven't been posting, but here are the video's I promised of the prototype in action. The first with everything in position.

video

The second with the blade (temporarily in place)

video

The work in the machine shop is going well. I don't have metal working equipment in my shop so I have been using the machines at work. I've been staying late after the machine shop guys go home and using the equipment then.

I didn't take as many pictures as I should have, I tend to get working and forget to take pictures.

I bought a rotary table to make the main plate that the pivot disk will mesh with.

(I took these pics with my phone, sorry for the quality)

Here it is lined up on the table.


Here is a pic of milling the final size.



And a close up of the ring (with the bottom milled).


After I was that far there I made the ring.

This was a 4" piece of round stock chucked in the lathe and turned down. The machinist suggested that I turn the end over sized and turn down a post that will fit in a collet. He said this would be safer and give a better level of accuracy. This is after initial turning, before cutting the chunk off.


Here is the piece cut off and mounted in the collet and turned down to size, ready to be bored out.


It Fits!

More to come in the next few days!

Monday, September 12, 2011

It's been a few days since posting but things are moving along well. I made the wooden prototype. and found a few problems that needed addressing. After building the knife holding block I found that I needed everything to be adjustable. I needed to be able to tweak the knife this way and that. So I split the arm and added two blocks face to face to hold the arm, but the one block will have over sized holes (by 1/16") that will allow for tweaks.

The next problem was with the knife, I can put in slots to mount the knife forward and back, but I needed to add a stop to adjust the height of the knife. So in the block I added an allen head bolt that will sit between the legs and hold the knife up.

Here is a sketchup pic of the modified design.

I was able to build this and put the arbor in place and adjust everything. Worked beautifully. So I brought everything to the machine shop at work and will start the actual metal work this week.

I'll try to get a video or a few pics of the wooden proto up this week, as well as a few in process pics.

Friday, September 2, 2011

Riving knife proto 2

So I made a few changes to the prototype in the shop. Not to much but I did lower the parallel arm 3/4". about as low as I can get it. The further apart the arms are the more they stay in parallel. To mount the arm to the trunnion I decided to go with 2 1/4" blocks. I can mount one to the saw to give left right adjustment. and the other mounted at 90 will have up/down/front/back alignment. So I can tune in the position of the pivot. I also increased the size of the ring 1/4. and shortened the overall length of the arm.


The plan is to try and make a new prototype this weekend. But first I am going to mock up the knife and it's mount.

Wednesday, August 31, 2011

Riving Knife 1st proto type



I got a prototype done. There were a few iterations, but the rough one made from wood works well enough to prove the theory.


Here's a video of it in action:

video


A few things I learned, I originally planed to make this out of 3/8" steel, but that is just a little to thick, so it will be from 1/4". My sketchup model appears to be off a little bit (measure don't make assumptions). There is more room around the arbor that I thought. The tops off in this video but there is about 1/2" between the top of the table and the top of the arbor so I can make a larger ring and trap the outside. originally I was going to have some wide head bolts trap on the ring (the arc slots in the sketchup model were the clearance slots for the bolts). But the trap design is better. This is hard to explain so I will be posting pictures once I make it.


I'll have to have a few custom shoulder bolts made, other than that nothing to complicated. The prototype also showed me that I need have some way to adjust the pivot arm if I am off a little. I'll have to put some thought into that.


I need to make a few adjustments to the mounting plate. Nothing radical, trim a few places for clearance, remove some excess, but the basic shape appears to be a good one.


Next step is to make 1 or 2 more prototypes. Once I have the design finished then I'll need to find a machine shop to make one. Hopefully I will find a hobbyist machinist who wants one for their saw and will make one for free!

Monday, August 29, 2011

homemade riving knife part 4

So I didn't get a lot done this weekend, Other responsibilities. But the bearings came in. That was really fast! so I give Accurate bearings 2 thumbs up for having the parts in stock and fast shipping.

I did get a chance to make a quick model in sketchup. After moving things around a bit here's what I came up with.

in the up position:


and in the down position:



Next I plan to make a prototype out of wood. then I'll work out the kinks in my design.



Friday, August 26, 2011

Making a riving knife part 3

So now that the table saw's stripped down I can focus on the riving knife. I decided to focus on this first, and the dust collection second, since the riving knife will determine the room for the dust collection. Here is what I have to work with:

I guess I never really explained what a riving knife is. I'm not going to go into to much detail, but basically it's a table saw splitter that rides close to the blade. Wikipedia has a great description. If you google homemade riving knife what you mostly see are adjustable splitters, and while these are better than the factory splitters they are not riving knifes.


The problem with adding a riving knife is that most saws use a trunnion that rotates from a fixed point. If you just slap a splitter on the yolk, the top of the knife will not stay even with the top of the blade. It will just rotate down into the cabinet.

All of the pictures I found of riving knifes on newly manufactured saw change the trunnion design to lift the blade up and down in a vertical manor. Looking at all this additional complication makes me wonder how these tools will last in the long run. A pivoting arbor will wear and just not raise as high but for the most part will not go out of left to right alignment. But these systems have a lot more parts and allow a lot more room for errors. And besides, I don't have the capabilities of making an new trunnion.

I've been doing a lot of looking around on the Internet, the first homemade riving knife I found was on a saw just like mine! I studied this design inside and out and it works great. But there are a few drawbacks. I would need to make a new pulley for the arbor and motor. I would need to machine the arm, and I would need to buy preloaded linear bearings. The last part was the killer, the preloaded bearings are ~$250 each! Plus I'm not sure how well this will hold up under long term use.

The second design I found was right in line with what I was thinking. The yolk on the saw rotates about a fixed point. If I were to add a parallel arm of equal length a set distance from the from the pivot point as the yolk rotational center, and the arbor center, these 2 things would remain parallel. Here's a picture to illustrate my point:



If the arms are the same length and parallel then the part will remain level. So all I need to do is make a plate to hold the riving knife. In the picture above the top arm would be the Yolk in the saw and I would add the second arm.


The space is pretty tight I have about 1/2" between the blade and the yolk, and even less around the arbor because of the flange that holds the blade on the arbor. I will have to make some sort of ring to go around the arbor that mounts to the yolk. If you look in the first picture you'll see that there is about 1/4" of space to drill a hole and tap into to mount the ring. This might be a problem.


Fortunately this space appears to have been machined, and seems to be parallel with the blade. If not I will break out the file and level it off.


The parts that stick out on the yolk around the arbor hole, pivot hole, and gear rack are about 1/4" So this will provide some clearance for pivot arms etc.


The plan is to take a rubbing of the yolk, get measurements off of it, make a model in sketchup and play around until I get something that fits. Then make a mock up in wood, work out any kinks, and take the mock up and accurate drawings to a friend who is a machinist, make the parts out of metal and start sawing safely!


Thursday, August 25, 2011

Making a riving knife part 2

So I tore down the table saw. When I got the top off (which must weigh more than 300 lbs!) this is what I saw.


So I decided that I will need to improve the dust collection as well. Not visible in this picture is a little deflector that prevents the dust from coming out the slot where the lift lower crank travels when tilting the blade. That's about it for dust collection. So I will try to improve the dust collection as well. I'm thinking some shroud around the blade with some flexable DC host to handle tilting. Hooked up through the factory dc port. I will still need to clean it out once in awhile, but I hope I will be able to collect most of the dust.








After getting the top off, I vacumed out the saw and cleaned it up. Then I removed the motor shroud and using a brass punch a knocked out the arbor. It came out much harder than I expected, which is probably why the arbor didn't move once the retaining nut came loose.



I disassembled the arbor, and ordered new bearings from accurate bearing. They were helpful and with the part numbers from the old bearings it was easy to get the right parts. But when I called the first person I got started to take my order and then said "Wait, are you a woodworker?" I said "Yes"; then she transfered me to someone else who took my order. I thought that was odd. But they told me they would have them out today so that's good. The bad was that the front bearing is a double bearing and was $38.00! thats alot for a bearing even the rear bearing I thought was pricey at $9.00. but both of these are special bearings the front being a double and the rear being a raised flange. And Accurate was the only place that had them in stock, and the other places I called wanted around $75.00 for the pair and I would have to wait 4 to 6 weeks.


As for the riving knife I plan to put some sort of pivot arount the arbor hole on the yolk. I only have 1/4" of room to work with, so it's going to be tight. I will probably lose a 1/2" or so of height, If I lose that I will still have about 4 1/4" of cutting, so I can still get through my 16/4 stock. So I'm okay with that. Forgot to take a picture of that! maybe tommorrow I will get one.

Wednesday, August 24, 2011

A homemade riving knife

Recently I heard my table saw making a funny noise when it was winding down. That's never a good sign. I have a delta-rockwell 34-350 with a 3 hp motor in it, if your not familiar with the saw this saw takes a 12" or 14" blade, and the motor is a real 3 horse, it weighs in at about 150 lbs, and needs a 220V 20 amp circuit.





So when this saw makes funny noises I respect it and try to find out why.








After a little searching this is what I found. This picture is looking down through the insert hole at the arbor. In the middle you'll see the threaded thing. That piece is a retaining ring and threads in to the yolk to hold the arbor bearing in place. Now I'm not a mechanical engineer, but I am certain that loose bearings holding a 12" blade spinning at 3400rpm is a bad thing.


So although I had other projects going on at the time (don't we all) I decided I needed to put the ring back. So after a few checks I wasn't convinced that I could just grab a spanner and tighten up the retaining ring, I was afraid sawdust had gotten around and in the threads and in any space left from the bearing moving. So I decided to pull the arbor, clean it up, and re-assemble.


And of course in order to pull the arbor I have to remove the table, remove the motor, and pop the whole thing out. And when growing up on a farm you learn that any time you pull something from a bearing, you replace the bearings. And since I was tearing it down, and this tablesaw is at least 50 years old, I would have the motor rebuilt at the same time. So this will include a bearing job, and motor rebuild as well. And if you're wondering about rebuilding a motor, it's a really easy job. Just take it to a motor rebuilder and pick it up a week or two later.


At this point your probably wondering why this post is titled a homemade riving knife, since I haven't mentioned a riving knife yet. It's because I decided that since I will have the entire saw stripped down I will add a riving knife. I had a close call a few weeks ago with a piece of wood pinching the blade. Fortunatly this piece was only about 18" long so I was able to finish the cut, but it made me pause. A pause that made me consider going out and buying a sawstop, and if it was in the budget I would have. But anyway over the next few weeks I will post my trials, and try to detail the design process I go through to make the riving knife.


I won't claim that what I'm doing will be successful, or that it's even smart, but I'm hoping that some of you will help in this effort and offer some suggestions on improving my design, and in the end I'll end up with something that's safe and works reliably and well.


Tuesday, February 8, 2011

Dovetails plugin file missing

I have gotten a bunch of emails recently about the plugin missing from the mediafire download link. Media fire removed the file because it had been up there for a long time, and it's time limit had expired.

I am no longer supporting the dovetail plugin, and I am not going to bother providing it for download because there has been no interest in it.