Setting Blocks or Glazing Blocks
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Ms. Chips



Joined: 01 Sep 2006
Posts: 9
Location: Northeast Kingdom, VT

PostPosted: Tue Sep 12, 2006 10:52 pm    Post subject: Setting Blocks or Glazing Blocks Reply with quote

We have some big 1 over 1 windows to restore and I'm trying to get at least 8 more sashes done before it gets REALLY cold. This brought up a question that I had posted previously:

- How does one use setting blocks? Are they something you have to make yourself? I used be-headed wooden matches on one sash but they are smaller than the ones I removed with the old putty. Too bad I threw them out...
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johnleeke
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PostPosted: Wed Sep 13, 2006 12:50 pm    Post subject: Reply with quote

Setting blocks hold the lower edge of the pane of glass up off of the neck of the lower glazing rabbet.



This becomes important with larger panes of glass, say bigger than 36" x 36", because its good to have the edge of the glass "cushioned" by the glazing compound all around. It's critical on larger thicker plate glass panes, and is standard practice in "store-front" glazing.

The blocks are spaced no closer to the corner than 1/4 of length of the edge of the pane.



When glazing vertically the blocks are usually placed for the bottom line of putty after spreading all the bedding putty. Then the pane is set into the bedding putty, then the blocks are placed at the side edges and the top edge.

If glazing horizontally, set the pane of glass in the bedding putty, set the setting blocks at the bottom edge of the pane, set the glazing points, then raise the sash vertically and lightly tamp it on the bench so the pane will settle down onto the blocks and the blocks will settle down onto the neck of the glazing rabbet in the rail.

With the setting blocks the stress on the glass is parallel to the plane of glass and so is less likely to break the glass during sash handling and later during the service life.

Making Wooden Setting Blocks:

Rip out a few sticks of wood the right size on the table saw, then cut off 1/2" pieces as needed.

If you don't have a table saw, or cannot safely rip narrow pieces, cut 1/2" off the end of any wooden board or stick, and then split out little blocks.



Take a look at the wooden blocks and pieces to the right in this photo. While the photo shows me trimming pins for sash joints, I have just split a few pieces off the block with the chisel and mallot, which I then split into pins. Instead of making pins you could use the same method to make some setting blocks.

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by hammer and hand great works do stand
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Last edited by johnleeke on Mon May 02, 2016 9:25 am; edited 4 times in total
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emrude



Joined: 21 Aug 2006
Posts: 17

PostPosted: Wed Sep 13, 2006 4:01 pm    Post subject: ??? Reply with quote

So what are setting blocks? When and why do use them?


Marion
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johnleeke
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PostPosted: Wed Sep 13, 2006 4:25 pm    Post subject: Reply with quote

Setting blocks hold the lower edge of the pane of glass up off of the neck of the lower glazing rabbet. This becomes important with larger panes of glass, say bigger than 36" x 36", because its good to have the edge of the glass "cushioned" by the glazing compound all around. It's critical on larger thicker plate glass panes, and is standard practice in "store-front" glazing.
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by hammer and hand great works do stand
by pen and thought best words are wrought
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Ms. Chips



Joined: 01 Sep 2006
Posts: 9
Location: Northeast Kingdom, VT

PostPosted: Wed Sep 13, 2006 5:16 pm    Post subject: Reply with quote

Thanks for the info John,

I can DIY setting blocks w/ a hand saw and chisel, but I'm still not sure what size they should be - does it matter? I would guess from the photo that they're about 3/16" square x 1" or so long. Would my lazy way of using matchsticks not suffice? The setting blocks go into the back bedding, then more putty on top of them?

I'm having a hard time understanding how raising the lower edge UP off the rabbet helps. That would put the glass at an angle and the glazing points could eventually bow or work themselves out of the wood, no? And you'd have to use flat triangle points (which I have a really hard time with) rather than the shoulder type, wouldn't you?

Cornfused,

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emrude



Joined: 21 Aug 2006
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PostPosted: Wed Sep 13, 2006 5:45 pm    Post subject: Reply with quote

Thanks, I didn't know that's what they are. I guess there are a lot of terms and ways to do things that don't get passed on because of the lack of formal training. I guess we are making up for that on forums like this.

Marion
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johnleeke
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PostPosted: Wed Sep 13, 2006 6:57 pm    Post subject: Reply with quote

Using 1/2" to 1" lengths of match sticks would be fine for panes of single- or double-strength glass. I though you were finding them inadequate because your original blocks were bigger and you were looking for a way to make custom-sized blocks.

I think there is a confusion here with the words up, down, upper and lower, top and bottom. I always use these words in relation to the sash's position when installed in the window. You might be thinking "up & down" when the sash is laying flat on the bench while you are working on it.

The glass is always laid flat against the shoulder of the glazing rabbet, with a thin layer of bedding putty between the glass and the shoulder. The setting blocks are always between the lower EDGE of the glass and neck of the lower rabbet. The block is touching the edge of the glass that is about 1/16" wide, not touching the broad face of the glass.

(sometimes these things are hard to describe with words alone, and I don't have time today to make a sketch or moch-up a photo. If you think you still don't get it, suggest this as a topic for one of the live video conferences.)

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by hammer and hand great works do stand
by pen and thought best words are wrought
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Harold Pomeroy



Joined: 26 Apr 2006
Posts: 25
Location: Chesham Station, NH

PostPosted: Wed Sep 13, 2006 8:11 pm    Post subject: Reply with quote

A setting block I have seen in mid-20th century windows is glass. People would cut 1/8" wide by 1/8" thick pieces of glass, and use them to shim glass in place. This was on small, less than 1 square foot, panes. I think this was a really dumb idea.

With better putty, like UGL Glazol, I don't see the need for setting blocks, except when the glass is cut too small. The glass seems to stay put until the putty sets up. At a certain weight of glass, this no longer holds true.

In larger work, the setting block will be sure that the weight of the glass is borne on two soft points, not one high, hard, spot on the sash rabbet. Putting the entire weight of a larger piece glass on one point is a good way to start a crack. One would not want to have a customer open a window to yell at the loud neighbors, slam the window closed, and then be embarassed by smashing glass, all because you were slacking in the setting block department.

Harold Pomeroy
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johnleeke
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PostPosted: Wed Nov 19, 2014 11:37 am    Post subject: Reply with quote

Sometimes spacer blocks (of soft wood or hard rubber) are added between the edge of the pane and the neck of the glazing rabbet, especially with larger panes and thicker plate glass. The blocks are spaced no closer to the corner that 1/4 of length of the edge of the pane.

When glazing vertically the blocks are usually placed for the bottom line of putty after spreading all the bedding putty. Then the pane is set into the bedding putty, then the blocks are placed at the side edges and the top edge.

With the spacer blocks the stress on the glass is parallel to the plane of glass and so is less likely to break the glass during sash handling and later during the service life.

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John

by hammer and hand great works do stand
by pen and thought best words are wrought
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