Question on Spline Jigs

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I have a project I need a spline jig for that I need some angles different than 90 degree corners.  Some obtuse and some acute.  So I've come up with a design for an adjustable jig.  But I only have a one-sided design.  All of the jigs I see online have a support for the adjoining side.  Along these lines:


But I'm wondering if there's any real reason both sides need to be supported?  My design only supports the one side and I figure to clamp the work to the jig.  I want support on the back side so there is a backer to prevent tearout.  But when I look at adding a support for the front side of the box, my design gets big and (seemingly unnecessarily) complicated since the angle to the cutter has to be adjustable AND the angle between the two supports would need to be adjustable.

So is there a good reason for the jig to support both members or can I get by with a one-sided jig like my design below?

53 Replies

Make one and try it out on soulme scrap, see how it works,   Go from there.   That is what I would do.   Trust my own experiments.  

Ron

I can only come up with 3 reasons for the 2 sides.  1-You don't have to clamp the box down; 2- I suspect there is some stability issues and 3- it's the way it's done.

I like your idea and will wait impatiently  ;-) for you to post the results.
I would think that positioning for repeated cutting might be an issue with a one sided jig, but that could be overcome. Seems like a reasonable idea. 

Ryan/// ~sigh~ I blew up another bowl. Moke told me "I made the inside bigger than the outside".

Ken if this is for the flag case I made a 2-in-one. Posted here and on LJ in my projects.  Real simple. Works.

Petey

Ken I made a 45 degree spline jig. Then made a 22.5 deg insert for the same jig. It's on my project page. Might be what you need? 

Petey

Thanks Petey.  That does look handy but I also need 37.5 and 52.5 angles for my flag box and I couldn’t use an insert for the 52.5.  Plus I don’t want that many pieces to keep up with.

Ryan, I already thought of positioning.  I intend to add a measuring tape for the fence and key it in one of the t-tracks to keep it square.

Sounds like I’ll keep rolling with what I have😎
I've always just made spline jigs that ride on the fence. Would be easy enough to just install a single leg that can pivot for the needed angle.
I made a simple l, non-adjustable jig from MDF but it got wet and fell apart.  It had only one side and performed just fine.
I think the V is to allow it to sit into the V and be held against potential movement with downward pressure as the piece goes through the blade. As we know contact with a TS blade at anything except straight in can get wiggy. Having the V dispenses with a strong suggestion to use clamps, so they are quicker to use.

Probably a single side on a sled, or against the fence could also be safe as long as the piece couldn't move, IE: clamps.
I would think you’d need to have an adjustable side no matter what, since you need the spline to be centered on both sides, so you’d need to adjust the jig to cut equally on each side. I still think you could do it with one ‘wing’ and clamps, but it’s still got to be adjustable…

Mine is just a simple 90° jig with a miter gauge slide on it…

Ryan/// ~sigh~ I blew up another bowl. Moke told me "I made the inside bigger than the outside".

Ken, I can picture what you are asking. But my thoughts are to use two supports for stability. Looking at the first picture, I would use that design, only make the supports adjustable using a pivot point and a knob and slot to lock in place. Use the rear to set the angle and the front to meet your piece to be slotted. Just an idea.
My one side is adjustable Ryan.  It will swing +/-25 degrees from 45.


That's more swing than it should ever need and once it gets to a certain angle, it wouldn't be practical but I couldn't imagine a scenario where I would need the extremes.  And mine will ride the fence (either table saw or router table) so I can adjust position by moving the saw/router fence in any case the work is too big to just use the adjustability in the fence on the jig.

 
GeorgeWest

I think the V is to allow it to sit into the V and be held against potential movement with downward pressure as the piece goes through the blade. As we know contact with a TS blade at anything except straight in can get wiggy. Having the V dispenses with a strong suggestion to use clamps, so they are quicker to use.

Probably a single side on a sled, or against the fence could also be safe as long as the piece couldn't move, IE: clamps. 

Yeah I could definitely see that George but I'll have a fence on one side and will clamp it to the table either with a quick clamp or maybe with some t-track clamps depending on the size of the work.  And spline cuts aren't heavy cuts most of the time so I certainly think it will be sufficient.  I'll test it on scrap first just to be sure.


So here is my concept for adjustable support on the other side.  It's not fully flushed out, the adjustable piece would require more support on the off side and I'd fine tune the support piece to give more contact with the work at 45 since that's the most commonly used angle.  But essentially the support would just rotate up to contact the work regardless of what angle the joint is.

At the common 90 degree corner:


At a 45 degree corner (like a flag box):

At the 105 degree corner like on my flag box:

And at the corresponding 75 degree corners on my flag box:


I'm still of the opinion that the second support is unnecessary but I'll wait to cut the jig side down until I test it on some scrap to make sure.  I really don't want this build to get any more complex than it already is...
What about a circle for the front support? That way you you’d really only have to adjust it along a linear path, front to rear, and probably a small adjustment at that, and circular shape would engage regardless of the angle of the work piece?

I think the nice part about a front support is that it would provide and anchor to allow you to exert downward pressure in the work to insure it doesn’t lift. Probably not necessary, but added insurance. As you say, most splines aren’t aggressive cuts…although maybe dovetail splines would be considered more so. 

Ryan/// ~sigh~ I blew up another bowl. Moke told me "I made the inside bigger than the outside".

That's a good idea Ryan.  I could just have a round piece with a flat bottom that slides front-to-back in a dado and locks down with screws.  I'm still going to try it one-sided first though.  It's just much easier that way and has a pretty small footprint for storage.
What about just using a biscuit jointer to cut the slot?
I'll have straight splines in one corner Steve but the rest will be dovetail splines cut on the router table.  I don't think my biscuit joiner will cut splines😉
I didn't see this thread until today (and didn't read all in detail so hopefully this isn't too far off topic). 

I don't have any comment about the angle adjustment, but I've been very happy with the one I built (set at 90).  I decided to go with the option of using the miter slots rather than the jig riding on the fence.  I also put t-track in the sled so I could use some "guides."  One is small and simple for larger items, just guides placement while I hold the item in place.

Then I made a couple more stops that could help hold a frame (squeeze from both sides with the plywood stops and hold with my hand down from on top to ensure the project doesn't shift upward).
Put a thick block on the back to cover the blade as a safety reminder to stay clear!

None of this is my invention, but rather a compilation of several ideas I found on YouTube when I was working on my wedding card project.  
It’s a good jig Barb! If you find time, you might want to read through this thread just to follow along, in case you want something adjustable in the future….since you built that jig, you might want to make another at some point? I’ve got it marked since I can certainly see the benefits of an adjustable jig…I really like how splines help a project.

Ryan/// ~sigh~ I blew up another bowl. Moke told me "I made the inside bigger than the outside".

Ryan - yes, I already have it marked to "follow." I think I'll need to get a bigger shop if I really build all the jigs that I want (need?!?)!!