# Trunnion Design



## kolias (Dec 26, 2008)

I know my question is not related to routers but perhaps one of you may have the info I want

I’m building a small table saw with a 5.25” blade. It’s a hobby project and l looking on the web for any tips I noticed a Trunnion is used to have the blade tilt but I can’t find any info on how to design a trunnion.

Basically I want to know how the half circles used on the Trunnion are designed. Are they based on the blade diameter and if yes what’s the relation to the blade?

Does anyone has an idea how to design a trunnion or where I can find any related info?

Thanks


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## FixitMike (Aug 14, 2011)

The center of the trunnion radii should be located where the blade intersects the table surface. That way, as the blade tilts, it will remain in the slot instead of moving to one side or the other.


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## kolias (Dec 26, 2008)

FixitMike said:


> The center of the trunnion radii should be located where the blade intersects the table surface. That way, as the blade tilts, it will remain in the slot instead of moving to one side or the other.


Very important to know

Thank you


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## sunnybob (Apr 3, 2015)

there are a series on how ro make, and full plans available from Mathias


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## JOAT (Apr 9, 2010)

sunnybob said:


> https://www.youtube.com/watch?v=RBucMKhrL8M
> there are a series on how ro make, and full plans available from Mathias


He definitely has talent. And I like the fact that he uses push sticks so much.


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## kolias (Dec 26, 2008)

sunnybob said:


> https://www.youtube.com/watch?v=RBucMKhrL8M
> there are a series on how ro make, and full plans available from Mathias


The tilt blade mechanism he is using (with hinges) is not the same as using Trunnions. I’m only looking for info on how to make the Trunnions.

Thanks for the video, quite interesting


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## Cherryville Chuck (Sep 28, 2010)

You can get an idea by looking up the parts schematics of various makers saws. Just pick some models and then search for their parts diagrams. Making one that doesn't tilt is really simple. You just need an arbor and some pillow block style bearings but you won't have much depth of cut with a blade that small. Maybe only an inch.


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## MEBCWD (Jan 14, 2012)

The radius of the trunnion can be any size and is only limited to the size of your overall project. Like Mike pointed out earlier you want the radius point to be centered on the intersection of the blade and the table top or you will create other problems that will limit the usefulness of your tool. You will want tight tolerances between the two trunnion parts and it would be better to right or left tilt the blade instead of tilting both ways to help maximize the bearing surface of the two parts. 

One part is basically a curved slot and the other part would have a mating raised slide. These two parts would be a set and you will need two sets for the mount. You might want to see if there is a CNC owner near you that can help cut parts.


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## JOAT (Apr 9, 2010)

The more I think about the Mathias saw, the more I think I may make a simplified version. His homemade saw fence is what started it. For now anyway, all my sawing is plywood, in just straight lines, and repeat widths - so with a set of homemade spacers, could change my cut widths in seconds. My old HF saw works, but needs tuning, and a couple of other issues, so thinking of converting that to a large disc sander, which it would be perfect for. I've got a old circular saw my younger son gave me, he pulled it out of a trash can, it had the cord cut off because the trigger switch now is continually on. Other than that it works fine, and would be perfect for my use. For smaller length pieces have already figured out a simple saw sled to use with it. I made a saw with a sabre saw mounted on the bottom of a plywood top awhile back, and it works great for odd jobs. Seldom use my bandsaw now - but that's mostly because I haven't made a stand for it so I can sit and use it - as is I have to stand to use it, and that kills my back after a few seconds; same with my bench drill press. For the saw all I would need to do is screw the saw down to a top, cut thru, raise the blade to just cut thru a piece of 3/4" plywood, and that's about it; I won't be cutting angles, just straight lines. Already got some ideas for variations on this - think I need another circular saw. I 'know' I need another circular saw; just thought of a 'sort of' portable panel saw.


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## kolias (Dec 26, 2008)

MEBCWD said:


> The radius of the trunnion can be any size and is only limited to the size of your overall project. Like Mike pointed out earlier you want the radius point to be centered on the intersection of the blade and the table top or you will create other problems that will limit the usefulness of your tool. You will want tight tolerances between the two trunnion parts and it would be better to right or left tilt the blade instead of tilting both ways to help maximize the bearing surface of the two parts.
> 
> One part is basically a curved slot and the other part would have a mating raised slide. These two parts would be a set and you will need two sets for the mount. You might want to see if there is a CNC owner near you that can help cut parts.


Mike you hit it right on! that’s what I was expecting since I have seen a lot of trunnion schematics but I could not figure out where the center of the curves was. Also I thought the curve was related to some part of the saw.

Now I have enough to get going and although a cnc would make the task much easier I can do the same with my router and my circles jig.

Much appreciated.

BTW as I mentioned this is a hobby project and I know my small blade would not be very useful cutting bevels to any serious depth but I plan to go into ships modeling where I will use thin pieces of wood and this saw will be useful


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## MEBCWD (Jan 14, 2012)

kolias said:


> Now I have enough to get going and although a cnc would make the task much easier I can do the same with my router and my circles jig.


A good circle jig should work alright. Keep us posted on your progress, might be a few people interested in making a small hobby saw.


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## kolias (Dec 26, 2008)

No problem Mike but it will be sometime before the final project is done. The attached pictures is my interpretation of various info I gather from the web and they show a sample made out of 5/8” MDF to complete a rough model. (MDF is very easy to work with making a model)

The first pictures show the Up/Dn arm of the blade which was easy to do and works fine. Next I’m working on the blade tilt mechanism which I have problems to understand. What is shown in the pictures is wrong but I just wanted to see how some alternatives may work. With the info I got now from the answers on this forum I will have to make the new trunnions and then establish their location.

My main problem is that my 10 amps router is too big to make small radius and I struggle with various jigs to complete the curves. I also have a manual mini Taig Lathe and Mill with a rotary table so I’m thinking to try the Taig to do the curves which is time consuming especially now in the summer when I don’t stay long enough in my workshop. That should have been a winter project when we all are cooped up inside up here in Canada, lol


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## kolias (Dec 26, 2008)

MEBCWD said:


> ......Like Mike pointed out earlier you want the radius point to be centered on the intersection of the blade and the table top or you will create other problems that will limit the usefulness of your tool. .


Mike can you please explain which radius point you mean? On the attached snip is it Point A or Point B?


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## MEBCWD (Jan 14, 2012)

Nicolas here is a picture of what I am talking about. The pivot point is at the intersection of the table top and the centerline of the blade. The trunnion radius will be whatever will fit your cabinet.


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## kolias (Dec 26, 2008)

Excellent schematic Mike, thanks for your time

Now I got it and hopefully by the weekend I will have the trunnions done


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## sunnybob (Apr 3, 2015)

Matthias has made most things;
here is his trunnions


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## kolias (Dec 26, 2008)

I got the trunnions done today (used 3/8” plywood) and after the installation I noticed a few mistakes.

First I have to lower the trunnions brackets by 5/8” to clear the table top when the blade swings. Also the base turned out not wide enough to fit the trunnions inside and I will have to fix this.

The trunnions radius turned out by mistake 1-7/8” and it should have been 2-1/8”. I will see if I have to make them again.

Overall it looks good but I have to install the mechanism to raise the blade to really see if I did the trunnions correct. For now it “Looks” good

BTW if anyone wonders the motor is 12-24VDC, 8K to 15K RPM.


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