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Author Topic: Stretcher bars that match!  (Read 2125 times)

mcpix

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Stretcher bars that match!
« on: August 15, 2011, 12:54:35 am »

I don't do a lot of canvas work, but I just recently completed two 36"x36" pieces and ran into a problem I've had before. I've ordered "heavy duty" stretcher bars from several well known manufacturers and I still have the problem that they don't always fit together properly. I can usually get them to square up, but even then the corners don't always mesh perfectly and sometimes when stretching, one of the pieces will move. It's very frustrating and sometimes leaves a bump on one of the edges.

Any suggestions? Am I doing something wrong? Theses latest bars were from Utrect. I also tried some from Daniel Smith, with similar results.

-Max
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dgberg

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Re: Stretcher bars that match!
« Reply #1 on: August 15, 2011, 05:57:49 am »

Before I started selling bars for my canvas business I did quite abit of research.
 After purchasing bars in pine 8' lengths for a year (Quality was hit and miss.) I decided to have mine custom made several thousand feet at a time in 10' lengths.
The product I have made locally for my own use and to resell is 1 1/2" and 2"  bars in kiln dried poplar. We cut standard miters with glue and staples for assembly. (No tenons)
No adjustability but I have determined thats a good thing. YOMV
Can be sold in lengths or custom cut to size. All you have to do is put a spot of glue on the corner and staple.
When I assemble I use my framing underpinner (ITW Amp) but a 1/2" crown stapler works perfectly.

To give your present vendors the benefit of the doubt not having seen their bars.
They may need a slight touch up at the corners after assembly especially if they are not glued. A piece of 100 grit sandpaper and you can ease any sharp edges or irregularities in a second.
Typically a shop will get 2 or 3 of your pieces out of one length.
 The final piece is cut from another length which may have come through the molder with a slight twist or warp.
You go to put it together and its slightly off at the corner. Not necessarily a quality control isssue, it's just wood.
« Last Edit: August 15, 2011, 08:50:27 pm by Dan Berg »
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davidh202

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Re: Stretcher bars that match!
« Reply #2 on: August 15, 2011, 08:54:05 pm »

I haven't used commercial tounge and groove bars in years, I also buy lenghts and cut and then assemble with an underpinner to order as Dan does.

A trick to remember...
when you get the corners aligned and the whole assembly square,staple or even thumbtack 4" cardboard corners of matboard or 3x mounting board (with one or two staples or tacks), on  to the back of each corner on both legs of the corner. This serves to keep the assembly totally rigid and square until you are finished with the stretching, and then the corner restraints can be removed when done. You can even leave them in if your doing a wrap and the corners get covered on the back.I always chamfer (sand), the corners and corner edges slightly to take off the sharp edges.

pardon my lousy Paint drawing ;)
« Last Edit: August 15, 2011, 09:07:58 pm by davidh202 »
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mcpix

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Re: Stretcher bars that match!
« Reply #3 on: August 16, 2011, 03:03:12 am »

Thanks for the tip with the mat board. When you say 4" do you mean a 4"x4" square piece?

I thought about just stapling the corners of the wood itself. However, that can be problematic as there is sometimes a gap between the two pieces (i.e. they align at the outside edge but have an ever widening gap as you move towards the inside edge). I always figured that since the stretcher bars are all cut at the same angle, that they should all fit together nicely. Some do, some don't.

I'm also surprised at how many people cut their own bars. I just assumed everyone bought the tongue and groove variety.
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Colorwave

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Re: Stretcher bars that match!
« Reply #4 on: August 16, 2011, 03:08:10 am »

Add a new name to the chorus that cut their own.  Too many odd sizes to depend on keeping them all in inventory.  Plus, I live on a rock in the middle of a very large ocean.

FWIW: I've never had significant quality control issues with Fredrix stretcher bars.  With cheaper brands, Ive had issues with bars not being the size they should, but never with miters being cut at incorrect angles.  Perhaps yours are coming from the wrong part of China or Vietnam (Vietnam got the stretcher bar and donut franchises, for some reason).
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-Ron H.
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dgberg

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Re: Stretcher bars that match!
« Reply #5 on: August 16, 2011, 06:37:34 am »

This is what we use to cut miters and then staple.
Third shot is how the joint should look on the bottom side.
Joint should be tight at the top and bottom,no gaps.
If you are properly stapling good mitered joints with glue the corners should never move,even when stretching.
« Last Edit: August 16, 2011, 08:51:36 am by Dan Berg »
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davidh202

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Re: Stretcher bars that match!
« Reply #6 on: August 16, 2011, 11:09:25 am »

 4"  Square will work or a little larger on big pieces, just big enough to give firm support.  As long as you square up the bars first.THe angle in the middle of the miter doesn't matter at all as long as the outside dimensions are square. The cheaper bars are not always perfect but the end result will be fine as long as the bars are not warped
Measuring from corner to corner diagonally  is the way to get that right.
Look for a used power miter saw (Makita ,Dewalt) to cut stock if you don't want to invest in a new one.
Though it can't hurt, I don't bother to glue. Once the canvas is stretched it wont go anywhere ;-)
« Last Edit: August 16, 2011, 11:13:20 am by davidh202 »
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