What does the jig look like to ...

[BadeMillsap]

OK I admit it --- I'm an idiot ... I cannot for the life of me get this pictured in my head (or on paper) so I can build it ...

The project is basically some mission style (arts & crafts) work on a baby crib ... simply tenoning in the slats along the gate, sides ... simple enough ... I have a Delta table top mortise machine. The slats are 2" wide and 7/8" thick ... I intend the tenons to be 3/8" wide' (have a bit/chisel on the machine for that), 1" 'long' with side shoulders of 1/2" and edge shoulders of 1/4" ... the mortises will be in the edge of the 'rails' which are also 7/8" thick. Depth of mortise/tenon not yet established but I expect 1/2".

In any given rail I need a series of mortises evenly spaced 4 3/8" leading edge to leading edge (right most edge of 1 mortise to the right most edge of the next mortise).

So ... since I need in some cases 15 or so of these mortises in a given rail ... I want a jig that allows me to 'EASILY' move the rail along through the mortise machine making each mortise the same length ( 1" ) and in the correct place.

I'm sure this is a straight forward exercise and one of you helpful folks will be able to give me a shove in the right direction ... for some reason I just cannot 'see' what this jig looks like.

I've made sure the fence is square & true and correctly set for the 1/4" edges and the chisel is square to the fence but the trick of getting the lateral movement of the workpiece through the machine to evenly space the mortises is simply escaping my poor weak mind. Surely, this is not a case where each mortise has to be 'laid out' and lined up in the machine 'by eye' ... ... that would seem like a sure fire way to disaster.

Thank you in advance for any help offered!!

[cgallery]

I'd lay them out on both the top and bottom rails simultaneously with a pencil, and then eyeball it.

[shoottx]

On center for the holes install a small hinge on the fence with a tenon attached to the other side of the hinge. After cutting the first mortise move the rail down so the tenon on the hinge locks into mortise. Repeat 15 times.

[poolhound]

OK - Just so I can ensure I have got my head around this with a mortise every 4 3/8" that will make the rails somewhere between 5 and 6 feet long - right?

I would assume that your mortise machine does not have a fence this long or base support so that would need to be factored in. While the 4 3/8 dimension would be ideal to be perfectly spaced (ie with in a few thou) the key must surely be to ensure that the mortises in both rails are in the same relative spacing with respect to each other. this means creating a jig that has repeatability.

The other issue is that, as mentioned before the rails are long and therefore to create a stop system at some point it will be approx 5' from the chisel. You could do something that was attachd to the base or fence but this would mean making registration marks or even holes in the workpiece so if you did that you may as well layout the whole dang lot

I can think of two similar solutions. both will require you to have some form of support to the left, right or both sides of the mortiser.

1. Create a bunch of blanks 4 3/8" wide and one 1" minus the size of the chisel. Create a stop that will align the chisel at the edge of the last moretise. make the first cut then insert the small spacer and make the last cut (in the mortise). remove the spacer and make the inner cuts. Now insert a 4/28" spacer and repeat until done.

2. basically the same thing but the base has holes for dowels laid out at the appropruiate points. insert the dowels in a similar fashion as with the spacer technique.

You could even do a combination with the dowel holes spacing the 4 3/8 and then a spacer for the 1" size of the mortise.

I hope this is what you were looking for.

[Pappy]

Probably a fancy flip stop set up to do this but this should be easier.

Clamp an 8/4 board solidly to the front of the table with a deep dado front to rear the size of the mortise chisel. Line the right edge of the dado with the leading edge of the first completed mortise. A lip on the front and closest side edge of the table would help maintain alignment.

Mill a piece of stock the same thickness as the width of the dado and cut it so it sits in the dado with a 'hook' that will fit into the completed mortise. This would register the leading edge of the next motise and provide a stop for the length.

[tribalwind]

are you trying to not have to lay them out with a pencil/marking knife?

without thinking too hard and hurting myself, what bout 2 scraps squared up .
one 3-3/8" and another 4-3/8" to mark each new mortise 1 at a time,referencing off the right edge of the previous? could even have it notched so there were a 1x3/8 tenon to quickly fit in the previous mortise.
or if you made the 2nd block 4" then you could just butt the piece with block up to the chisel-bit and i guess wouldnt need to mark then.

that work ?

[poolhound]

Probably a fancy flip stop set up to do this but this should be easier.

Clamp an 8/4 board solidly to the front of the table with a deep dado front to rear the size of the mortise chisel. Line the right edge of the dado with the leading edge of the first completed mortise. A lip on the front and closest side edge of the table would help maintain alignment.

Mill a piece of stock the same thickness as the width of the dado and cut it so it sits in the dado with a 'hook' that will fit into the completed mortise. This would register the leading edge of the next motise and provide a stop for the length.

This is a good idea Pappy. I was trying to think of a good flip stop solution but registration seemed like an issue. Of course the previous mortise provides this - silly me - duh

[cabinetman]

A simple way of spacing the mortises is to make the first mortise. Then make a sample tenon that fits. Measure from the leading edge of the first mortise to where the leading edge of the second mortise will be. Drill the second mortise, and without moving the wood, set a stop from the fence to the front of the first tenon. Remove the first tenon, place it in the second mortise, and push it forward to the stop, and drill the third mortise, and so on...
.

[cgallery]

The reason I said to lay 'em out w/ pencil and use your eyes is that, if your jig is off by a small amount, the error will be cumulative over the length of the rail.

Nahm doesn't use stop blocks for mortising, does it?

[JR]

I recently did a project in which I had number 1/2" by 1/2" spindles separated by 1/2". I used a stack of scraps from the spindles as moving stop block, removing two pieces after each cut.

Now, this project was a bit different than yours. I as acutely interested in the spindles being 1/2" apart. But the group of spindles was centered in the stretchers they were installed in, with a ~2" gap at either end of the run. My concern was that the individual gaps be perfect, but I wasn't too concerned abou the end gaps.

I'm with Cgallery on this. I'd lay it out with a sample splat with tenon and us a pencil to mark the tenon locations. You're interested in making sure the gaps at the ends are symmetrical, which may not happen if there's an error on your jig. If there are minute differences in gap between each splat it will not be noticeable. Manual layout will identify any problems before you start cutting.

My 2c

JR

[JoeyGee]

C-Man beat me to it, that's the way I would do it.

I would put a board perpindicular to the fence, with a rabbet against the fence, rabbet facing down. The rabbet would match the size of the work piece, it would slide under the rabbet. Inserting a dowel or something the same size as the mortice into the mortice would serve as the stop, hitting the top of the rabbet.

Mortice, move dowel into new mortice, slide, repeat. I am sure this is what others have said, but sometimes I have a hard time picturing things.

[BadeMillsap]

Thanks ... weighing the options ...

You guys are GREAT! Thank you for all of the responses ... I've got to mull them over and see which seems the most suited to my skills...

To PoolHound ... actually I believe I only need 11 slats in the rails max (the orig plan called for 17 but I've modified the plan) and the rails are 50" 11/16" ... so yeah pretty long. As observed, I will have to rig up some sort of infeed/outfeed support just to be sure everything is supported as I go along.

I had assumed all along the solution would require some sort of registration/index pin to make the spacing repeatable but couldn't picture best way to accomplish that.

To CGallery ... I know the traditional way would be to lay them out with pencil/scribe and eyeball it but honestly figured I had a better chance of correct alignment between upper and lower rail as well as "near perfect" spacing with a jig ... maybe I'm wrong about that but I've SEEN my eyeball work ...

The suggestion of TribalWind is appealing because of the simplicity ... have to see how accurate that turns out to be after 4 or 5 executions on scrap.

I'm a little thick I guess because I can't visualize Pappy's solution but I'll sleep on it.

I THINK I understand Cabinetman's notion but have to build it to see if I understand ...

So ... I have lottsa options to think about

THANKS GUYS!!

[tribalwind]

felt like practicing with sketchup,
fun tool! anyhow,this's what i meant.
id just do layout lines though prob.

click for larger image with dims.

[JoeyGee]

The reason I said to lay 'em out w/ pencil and use your eyes is that, if your jig is off by a small amount, the error will be cumulative over the length of the rail.

Nahm doesn't use stop blocks for mortising, does it?

Actually, he does--sort of. He made a jig for his DP to drill holes for the plantation shutters. That has been driving me nuts since last night. I couldn't remember which project he did it for. Finally I remembered.

[BadeMillsap]

THANK YOU!! and as demonstrated ... it's sooooo simple!!!

Well I sit here red faced with embarrassment and smiling with glee all at the same time ... once I saw TribalWinds's sketchup ... it hit me like a senior with a rock ... well duhhhh ... of course!!! that solves the problem and allows me to avoid having to lay out all but the 1st mortise on each work piece ... by having TWO "memory sticks" fashioned as suggested ... I can simply plug the shorter one in the previous mortise, and bump the leftmost edge of the memory stick against the right side flat of the chisel, lock the work piece in place, cut the mortise right most 'hole', put the longer 'memory stick' in the same previous mortise and move the workpiece to again have the right flat side of the chisel against the memory stick (now the workpiece is moved 1" to the right), lock it down and cut what is now the leftmost 'hole' of the mortise being fashioned ... then just cut the center out of the new mortise and repeat ... very simple, doesn't require any mods to the fence or building anything exotic other than the two simple memory sticks that took about 10 minutes including the 'guessing' on the router table until I had the bit set to correctly cut the mortise on the scrap stock I used.

So ... thanks to all with a special shout out to TribalWind for the 'picture' ... indeed worth a 1000 words ...