Twisting window assembly

[orphalese]

Hi all,
I'd appreciate a bit of trouble shooting help please. I'm making some windows from unsorted redwood. Timber is sawn and then dimensioned on my 16 x 9 Dominion DAA planer/thicknesser 65 x 76 section. Tenons cut on Sedgewick SE tenoner. Moulding and rebating on Dominion spindle moulder and mortices on a Multico morticer. All 3 phase. When I assemble a light it won't lay quite flat. It isn't far out but enough to concern me. I'm using digital gauges and have measured everything I can think of and am buggered if I can work out what is out. I've swapped the tenons around and still the same thing. Any advice would be really appreciated.

Adrian

 

[tomouse]

As a start I would suggest checking the squareness of both the mortices or tenons. Just a slight bit out can throw the whole frame into twist........

Also are they dead flat when your clamping up? Always clamp up on a dead flat surface to make sure, it's easy enough to get a twist in clamping that will hold through when you take them off.

 

[RogerS]

How much are they out by? What style? Are you talking about the frame or the casements sitting within the frame? Or just casements? TBH I wouldn't fret. You can usually nudge them back square when you fit them in situ.

What does worry me is that you say you are using digital gauges...why? They never had digital gauges when Georgian sash windows were made originally and they work just fine. I use a couple of winding sticks when I make windows and eyeball for flatness, adjusting accordingly.

 

[orphalese]

Thanks for the speedy replies. Yes these are casements and even dry assembly on a cast saw table shows a twist. I've measured shoulders at both sides etc and checked it's all square. There is an ovolo moulding with scribed tenon. Tenons are 20mm and pretty snug. I can push them home by hand and if I hold them up they won't fall out so assume that's about right. Hopefully when I put the glass in and fit the beads it will hold it flat. Just bugs me not knowing why it's out.

 

[Chrispy]

I would check and make sure the tenoner is running true if it's cutting each tenon very slightly intwist and not parallel to the face of each rail then the whole frame will be in wind, if you are sure that's OK then check the same for the morticer.

 

[orphalese]

Getting warm now. One end of a shoulder on a 76mm wide tenon is 0.3mm higher than the other so over a 1.4m window would account for it. Now how to fix it.......?

The tenonner table runs on a rail which is bolted to the body with allen bolts and no adjustment. The table itself has 3 runners and again no obvious adjustment...........

 

[custard]

I've used a Sedgewick Tenoner and it drove me to distraction. Adjust one thing and everything else changes, but just by a teeny weeny amount so you don't immediately notice. You have my sympathies, I really like the Sedgewick Morticer, but their Tenoners should come with a large packet of sedatives!

 

[Chrispy]

I don't know the Segwick but with my Multico its not the trackway you need to adjust it's the way the carriage sits on the track if that helps.

 

[RobinBHM]

If the bed is not parallel to the cutting heads, it shows most on door bottom rails due to their width.

Its probably worth machining a few trial pieces and taking an average before making adjustments. Tenons often measure slightly different from side to the other, it only takes a slight twist in the wood or a trapped bit of wood chip.

When I get Tenoner problems, I start by making sure the cutters are sharp, then clean off any dirt build up on the guide rails and bearings.

Unfortunately, I dont know how to adjust the beds on a Sedgewick, although I used to one. But Im sure somrbody on here will know!

 

[Jacob]

Laying it flat, light clamping and looking at a high corner - you can drop a saw down the shoulder joint then clamp a bit tighter and it might pull it straighter. Difficult to describe but it works!

 

[Bradshaw Joinery]

0.3mm is a teeny amount dust could make that difference. But if all else is good then it may be. I usually guage the mortice chisel with vernies then machine the tenon .3 smaller off the machine for a sash, bit more clearance for doors.

I would, as advised above, check each piece of timber for twist with winding sticks, tis the usual culprit for a twisted sash.

Is it just this sash that is twisted?

 

[richarnold]

I'm not sure if I'm missing something here, but I have been using a Sedgwick tennoner for years, and adjusting the bed could not be easier. There is a bolt with a locking nut at the end of the swinging arm. If you slacken of the locking nut you can move the whole bed up or down. I tend to lower the bottom block level with the bed then using a steel strait edge, check it lines up with the front and back scribing cutters.
Cheers, Richard

 

[orphalese]

Hi Richard,
It's in the other plane so I'm wondering if the back of the rail needs shimming?

I'm getting identical problem with each sash Olly. I'm wondering if when I plane and thickness it's important to face mark the squared sides before thicknessing and arrange so they are internal jointed faces? I'd kind of assumed with wood square it didn't matter so was selecting for any knot position.

I'm self taught so I could easily have missed something obvious. Appreciate the tips above!

 

[Jacob]

Laying it flat, light clamping and looking at a high corner - you can drop a saw down the shoulder joint then clamp a bit tighter and it might pull it straighter. Difficult to describe but it works!

Repeating myself here sorry. I've made hundreds of window frames and easing them into square and flat (as described above) is just normal procedure. You can set up machines perfectly but it only takes a gnats whisker of error to throw a frame out, so some adjustment before glue and wedges is often necessary.

 

[orphalese]

That's very useful Jacob thanks. I've just put a washer under the back of the tenoner rail and it's now running true. I have a feeling I'll still be trying your technique though!