Without question, I'd replace the original with solid maple, more like 1/8" thick, with grain oriented PARALLEL to the top grain and the pull of the strings. That puts the greatest stiffness in the direction to resist bending with the obvious forces in the area, and completely eliminates any possibility of cracking between the bridge pin holes.
Some folks use ply, and others run the grain at a diagonal to improve stiffness and reduce cracking, but I still insist that the best grain orientation for bridge plates is parallel to top grain.
Forgot to mention that I'd also evaluate the general stiffness in the area and not necessarily cover as much area as the original.
If I may add please that often there is no need to remove the bridge plate if string ball wear and some chip-out is the issue.
Instead there is always the option of overlaying a bridge plate cap. Mine are typically around .060" thick, 1/2" longer than the pin spacing and about 1/2" wide. Minimal is better, grain direction as per what Frank said about bridge plate replacement. Bevel the edges just like you would with a bridge plate. I use 100+ year old maple flooring that we scored just for bridge plates.
I prefer to drill all pin holes in the cap before installation and then use 3/16" delrin or teflon pins ( so the glue does not stick to them) on the two outer pin holes to properly locate the cap and prevent it from sliding out of place while clamping.
Then it's drill the pin holes again to remove glue, ream to fit the desired pins and Bob's your uncle. It's also not a bad time, justification wise to convert the instrument to slotless pins which the primary benefit is that the string balls won't be resting on the edge of the pin holes anymore which is likely what damaged the plate in the first place.
Looking at vintage stuff that had slotless pins I've yet to see damaged plates from the string balls. The industry went to slotted pins to eliminate a semi-skilled process of slotting the bridge, top and plate likely to save production costs but this time the unintended consequence was excessive plate wear from the string balls.
On my own stuff that I build when I have time I've always used slotless pins for exactly this reason. Slotted pins can be used as slotless pins simply by turning them around but I prefer to replace the pins with slotless pins to avoid any chance of someone someday not understanding and positioning the pin slots against the box slots, not good....
I'm attempting to replace the bridge-plate on a Gibson B25-12. I've read Frank Ford's blog on Frets.com about replacing a bridge plate but I have not yet been successful removing this one (pictures attached).
Can anyone give me some advice about how hot the bridge plate needs to get before the hide glue releases? My guess was about 140-degrees, but I notice Frank's aluminum caul was a whopping 375-degrees. I tried a 6" bridge heating-blanket up to 170-degrees with no joy. So, I figured I'd do a little research before my second attempt. Maybe I'm just being too cautious? I'd like to avoid damaging that great old sunburst finish.
All clues are appreciated.
I don't think this is HHG, Mark. In my limited (hobbyist) experience, it's pretty common for these bridge plates to be destroyed by the removal process. The pictures show a lot of damage but if you could clean it up, fill the damaged areas and skin over the existing bridge you may be better off than risking the top by removing all of the original plate.
Thanks for replying, Ned. I think you're right. My second-choice approach is to fill and cover. It's much safer and seems to be a fairly well accepted method in the repair/restoration community. For clean-up I am thinking of crafting a sort of miniature router plane about the size of those little Ibex planes, so I can get a clean bottomed channel and then fill with maple. Wish me luck.
Mark, I have to agree with Ned, that Red stuff looks like Weldwood urea formaldehyde glue that Gibson used in the past. It is a non reversible plastic resin glue that is unaffected by reasonable heat, water or any solvent that I personally am aware of. It is rather common to run across instruments that have braces and such falling off that have been glued with this stuff. I believe this is due to the unyielding nature of the glue to deal with woods natural expansion and contraction from moisture and heat.
If you have given a good go at prying and prodding to get the plate off with no give, you're probably best off to try and repair the existing bridge plate, as Hesh and Ned have suggested..
This is especially helpful. My best guess so far was marine epoxy. I emailed the Gibson repair shop who replied that "It should have been hide glue and a 1/8th 3 ply bridge plate" and I wish it was. But this guitar has a full 1/4", 3-ply plate and that weird red glue all over, even in the kerfs. So I'm guessing you're probably right about Gibson doing it (especially after reading "Kalamazoo Gals"). In any event, it's really solid and I can't get it to budge. So the next stop is explore how best to cleanly remove the damage to the plate, replace that section, and maybe add a plate cap. I've read about using epoxy as a filler in this situation but I don't want to add insult to injury.
You guys are great-- many thanks for all the help on this project.