View Full Version : Stretcher Bars
10-27-2005, 04:40 PM
Does anyone know where I can get a plan for the joint with wedges to build my own stretcher bars :clap:
10-27-2005, 09:15 PM
Hi, welcome to WC! and the Studio Tips forum. I would try to look online first, you're sure to find something. Even just an image search in Google might turn up basic drawings or even diagrams of the corner joints.
Failing that you might check with a woodworking magazine, I can't imagine there wouldn't have been an article on home-made frames at some point in the past.
10-28-2005, 04:51 AM
I have done extensive research on this subject and can find no reference on the net.I have tried without success to reproduce them using a router table.
I think they could be reproduced quite easily using a table saw, or even a hand saw if you have the patience and expertise.
11-01-2005, 12:38 PM
Thank you all for trying, if I find an answer, I'll post it
11-02-2005, 01:42 PM
i think the joint is called a mitred open mortise and tenon, or a mitred corner bridle . Heres a good pic
You can see that you will need a dado cutter for yer table saw and a high fence or jig to hold the bars upright as you cut the tenons and slot the mortises.
The bead on the inner side of the bar is important - you could cut that easily on a table saw too , but you'll have to do that last because otherwise you wont be able to mitre off the mortise face .
You could also do a splined mitre joint - might be easier that way . For that you'd have to make a jig like this . be harder to figure a way to key em out though
11-02-2005, 02:12 PM
That is the joint. Unfortunately I don't have a table saw to try it out but it looks feasible. For smaller bars you would probably get away with just a saw blade with a wide set on the teeth.
11-02-2005, 02:51 PM
Hey Mick ,
Hows things ?
It might be possible with a long straight cutter on a router table but i dunno - the cutter would flex like hell i think
11-02-2005, 03:14 PM
The problem is, there is not a small diameter cutter made commercially that is long enough. Best I could find was 1/4 x 5/8 long. The other problem is they don't like cutting end grain, even at that size it was almost impossible to control. So think a table saw is the way to go.
11-02-2005, 03:19 PM
heres another version
11-03-2005, 04:38 AM
These are both good joints, the first one is used in top quality closed corner frames that are carved after assembly. For Keying out I am thinking triangular corner piece with elongated screw holes. Will give it a try.
11-03-2005, 12:14 PM
I was thinking the same thing - a routed slot for keying i mean . Really, I dont see why you couldnt do an easy mitred half lap joint wi slots and then use little carriage bolts wi wing nuts to tighten it down . Its not like it has to be pretty ... Most of the stress is compression anyway so even though the mitred half lap is a pretty weak joint I dont think with the bolts and washers it would rack so very much out of plane ...
About the long thin router bit -- theres probably a reason they dont come that long -- they'd have to sell Kevlar body armor to go along with it :) Ive never had one fly around the room but ya do hear stories ...
12-20-2005, 05:02 PM
does somebody know how or where can i build my own stretcher bars?
which kind of wood to use ?
what kind of tools?
can i buy a long strip with degree cut in all ready? and where?
or i need to do the degree alone how can i do it?
12-20-2005, 07:52 PM
Hi Stila77 and welcome to WC.
If you use the "search" at the top of this page it will give you all the previous threads on this subject. Search for stretcher bars and strainer bars in forums.
Strecher bars are avaliable in precut standard lengths and you need no special tools to put them together.
Making your own stretcher bars from scratch is a totally different kettle of fish requiring specialist tools. Strainer bars are relatively easy to make.
12-20-2005, 08:07 PM
what is it strainer bars?
12-21-2005, 05:21 AM
Stretcher bars have "keys" or wedges in the corners for tightening the canvas.
Strainers are just a simple frame with no adjustment.
12-21-2005, 11:17 AM
that's exectly what i want, i have miter saw so i can cut the angle but my problem his how to make a degree to the wood
12-21-2005, 12:07 PM
Sorry, I am having a little trouble with your English even though it is very good. Not sure what you mean by "my problem his how to make a degree to the wood" Can you try another explanation. Also what nationality are you as we may be able to get someone to translate for you.
01-02-2006, 08:00 AM
Hi Colin and others,
Happy New Year.
Seems we have been trying to over complicate making stretcher bars.:rolleyes:
I recently acquired a book on framing from 1899, long before complicated machinery, and found this.
A good saw and a chisel is all that is needed to make them, but could be easily made on a saw bench or router table.
I have marked the extended cuts for the wedges in red. A piece of small beading could be glued to the outer edges to lift the canvas clear of the main frame.
02-03-2006, 10:34 PM
The method I have found for making stretcher bars, is to cut the corners on 45deg. Then using a plate (biscuit) jointer, cut slots in both of the miters just a little more than half of the biscuit length, measured from the inside.
I then dry fit, square up the corners, and staple across the miter on the back side of the frame. This holds it in place for stretching the canvas.
After stretching the canvas, remove the staples. When the canvas needs to be tightened, just tap the free end of the biscuit.
02-04-2006, 09:34 AM
Hi Jerry and welcome to WC
Does this work if you only want to move one rail?
02-05-2006, 12:02 AM
Yes, because each corner has it's own biscuit, which also acts as the wedge.
The secret, if you can call it that, is to cut the slots, so that each biscuit protrudes from each inside corner and of course, no glue. Since the biscuit is oval shaped, it will be retained in the slots.
I found this to be the fast way to make stretchers and so far it has worked very well for me.
Hope this feeble explanation works.
02-05-2006, 12:09 AM
I reread your reply, and I missed yor main concern."can you move only one rail "
The correct answer is no. It will spread both miters equally of the corner you are adjusting.
02-05-2006, 05:26 AM
Thats what I thought, they are some where between a strainer and a stretcher, at least it gives some adjustment.
02-09-2006, 11:37 AM
Do you use the wedges/keys that (sometimes) come with the stretcher bars? (Some vendors give them to you and some other vendors sell them to you.) Can you 'over rely' on wedges/keys to tightening canvas? It's possible to tighten the canvas without the use of the wedges/keys.
One instructor told us to throw the wedges away. I simply square-up the corners of the stretcher bars (bought or homemade - strainers I guess to be precise) and then put in a couple of staples on the backside corners. If for some reason the canvas doesn't seem tight enough, I just restretch it.
What I'm more concerned with is an off-square or off-kilter canvas when it comes to framing the painting. There is little tolerance around the inside of the frame where the painting rests. I don't want a canvas too off-square that leaves space between the canvas and the frame on one or more sides.
I've seen photos of the back of canvases painted by 'masters' such as Picasso. On these particular canvases the wedges were used. I know that 'masters' such as Picasso have their canvases stretched to custom sizes and constructed by firms that specialize in stretched canvases.
So, I'm a little unsure whether the wedges/keys are worth the hassel or not.
02-09-2006, 11:59 AM
I simply square-up the corners of the stretcher bars (bought or homemade - strainers I guess to be precise) and then put in a couple of staples on the backside corners. If for some reason the canvas doesn't seem tight enough, I just restretch it.
Mick will undoubtedly have some input on this but the keys do provide a valuable method to retighten stretched fabrics as and when they loosen. They may not be ideal but with any natural fabric there is a natural slack/taut cycle (particularly in areas with a wide range of humidity).
Can you 'over rely' on wedges/keys to tightening canvas?
Sort of, you can over tighten but using them for their intended purpose isn't really relying on them too much. It's worth remember I think that for the majority of members they're buying readymade canvas so restretching isn't something they'd want to mess with and they may not have the appropriate tools.
One instructor told us to throw the wedges away.
All due respect to your instructor but one can get wildly-varying advice from teachers, much of which doesn't tally with what another will say! :)
02-09-2006, 12:07 PM
No it is not a waste of time, the keys are there to take up any slight slack caused by humidity changes, not to rectify a poorly stretched canvas. Strainer bars are a poor substitute for stretcher bars, and are fine for artwork that has minimal value.
It is a good idea to square the bars and staple the corners, after the canvas is stretched the keys are then just pushed in by hand, these staples can then be removed.
Remember you are framing a lot of your skill, hard work, time, blood, sweat and tears, not just a picture, so it should be done to the highest standards :-)
It makes my job much easier framing a well stretched squared up canvas than one that is all over the place.
07-09-2010, 08:47 PM
wow, i didn't even know you could stretch stretcher bars even after the canvas was mounted. how does that work exactly? doesn't it mess up the corners?
09-07-2010, 04:56 PM
I think strainers can be very good when conditions met. Stretchers are generally best but if a canvas is stretched on a humid day it is very nearly as good. The keys used in a stretcher are used to tone up a flabby canvas an a humid day so tone it up on a humid day to begin with. Also if one uses acrylic primer and polyester or nylon based canvas the reaction to humidity changes is very little. So, I say use a polyflax canvas with an acrylic ground an eliminate much archival related woes. :thumbsup:
09-17-2010, 11:30 AM
For anyone interested, here is an in depth article about keying out canvases:
The CCI... Canadian Conservation Institute is a wonderful resource.
11-29-2010, 02:28 PM
For paintings smaller than 24x24, I just use commercially available stretcher bars. For larger paintings, I have found that heavier stretcher bars are advisable. I do not like to go thicker since they stick out too far from the back of the frames. What I do is use wider lumber, usually a good piece of 1x4 pine, usually available at Home Depot from tree farms in Finland.
After cutting the miters on my super accurate Kreg Precision Miter Gauge, I raise the blade on my 10" table saw, slant the blade about 7 degrees, and cut a bevel on each of he 4 pieces using the rip fence. Do not cut the bevel from one side to another, but for only about 3" out of the 3 1/2" width of the each piece, leaving the outer edge flat for about 1/2".
I then use my Porter Cable biscuit joiner to cut each miter and join together with biscuits. Measure across the diagonals to ensure that the assembly is square. This process makes a very strong stretcher assembly that is still only 3/4" thick. After the glue is dry, I then stretch my own canvas tightly over the bars. If I ever have to tighten up the canvas, which is rare, I simply pry out the staples and restretch.
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