LumberJocks

Ripping African Mahogany

  • Advertise with us

« back to Wood & Lumber forum

Forum topic by clin posted 10-20-2015 05:57 AM 765 views 0 times favorited 10 replies Add to Favorites Watch
View clin's profile

clin

514 posts in 461 days


10-20-2015 05:57 AM

I need to rip some African Mahogany that is 1 3/4” thick (is that called 7/4?) and I need to get finished pieces 1.5” wide. The two boards are about 7’ long and 7.5” wide. Hoping to get 4 pieces form each board, but all I really need is 6 pieces.

I do NOT have a jointer. But do have a 3 hp table saw. The boards are pretty straight as is with relatively straight grain. My plan is to use a 8+ ft straight edge clamp I have (typically used with a circular saw), and clamp that on the boards giving me a true straight edge to following the table saw fence on the first cut. Then of course use this new edge for the other cuts.

I expect the wood to release some stress and warp, so was planning to make the first cuts as over sized as possible. Figuring 4 initial cuts at 1/8”kerf is a loss of 1/2”, that leaves 7” of wood divided by 4 giving me rough cuts 1 3/4 wide. I.E., 1/4” over sized.

Is 1/4” likely enough?

I realize anything is possible, but I don’t want to waste wood. Or perhaps I should be more conservative and just get 3 pieces out of each board. That would allow initial cuts of over 2”.

Also, when is a rough cut too big? In other words is there a rule of thumb for how much to take off on a final cut. Obviously there is some point where if you take too much off, you can relieve more internal stress and get more warping.

Hope all that made some sense.

-- Clin


10 replies so far

View jerryminer's profile

jerryminer

528 posts in 906 days


#1 posted 10-20-2015 08:03 AM

I don’t know how you’re going to straighten things out after you rough-cut your parts without a jointer, or whether straight even matters for your intended use (which is…?), but my normal process is to rough-cut 1/8 to 1/4 over size in width, then face joint, edge joint, plane to thickness, saw to final width.

A 7” board can get pretty squirrely when ripped into 1 1/2” slices. You may want to rip down the center first and learn something about that individual board’s stress characteristics and adjust your rough cuts accordingly.

View Tennessee's profile

Tennessee

2410 posts in 1979 days


#2 posted 10-20-2015 12:13 PM

African mahogany is pretty stable, but I agree with Jerry. I think you can depend on some release of stress and bow. Without some kind of jointer and planer, you are relegated to hand tools to flatten the boards, if you can at all.

-- Paul, Tennessee, http://www.tsunamiguitars.com

View clin's profile

clin

514 posts in 461 days


#3 posted 10-20-2015 04:06 PM

After the rough cuts, I’ll screw or clamp the pieces to some other straight edge and run them trough the TS again.

The other dimension (original 1 3/4” board thickness), is not critical, so will straighten edge in a similar manner and take whatever thickness I get.

Problem with ripping it down the middle first, is if there is a lot of movement, I may then only be able to get one piece out of each half after that. Then again, if I rip a 1/4 strip and it moves too much, it will be unusable, and the remaining would apparently only be good for two pieces at that point.

So either of those options seems to give the same result. I.E., might get all 4 pieces, or just two. The other option is to just just go for 1/3 sections to start. This ensure I won’t get 4 pieces, but extra allowance increases likelihood of at least getting 3 pieces. But that approach assures a lot of waste.

Jerry, from your description of leaving 1/8 to 1/4’, it sounds like my idea of leaving 1/4” and getting 4 pieces is a reasonable approach. I have two boards to cut up. Both of these 7 footers were a single 14 footer cut in half. So to some degree what I learn about one board may carry over to the next.

-- Clin

View daddywoofdawg's profile

daddywoofdawg

1010 posts in 1040 days


#4 posted 10-20-2015 04:10 PM

After you cut it let it sit for a week so it has time to move,twist,cup or whatever it wants to do before you start your milling.it most likely will do something,so let it do it’s thing before you spend the time milling and then have to do it again.

View clin's profile

clin

514 posts in 461 days


#5 posted 10-20-2015 04:21 PM

woofdog,

That sounds like a good idea. I’m not in a hurry.

-- Clin

View HokieKen's profile (online now)

HokieKen

1770 posts in 603 days


#6 posted 10-20-2015 08:26 PM

What’re you using the boards for? If it were me, I’d rip the boards into 3 or 4 equal pieces, let them stabilize then mill to final dimensions. Unless I was going to be gluing them up into panels. If you’re going to glue them up, rip them to size and get ‘em glued, cauled and clamped as quick as you can. Orient the grain properly in the glue up and they’ll take care of keeping each other straight.

-- Kenny, SW VA, Go Hokies!!!

View clin's profile

clin

514 posts in 461 days


#7 posted 10-20-2015 09:01 PM

The end use is just as a frame in a large door. This frame is not the primary support, but contributes to the stiffness of the door. Therefore it is still something I want to stay straight over time. I was initially going to laminate some Baltic birch ply, but was talked out of this due to this being an exterior door and this wood being on the edge.The concern was that regardless of finish, it might start to separate over time.

So I decided to go with solid wood and thought a hardwood might be best.

As is, these edges will not be getting glued (other than a thin plywood panel that will attached to this frame).

I hadn’t thought about the possibility of actually making them out of two pieces and laminating them such that they would help to keep each other straight.

Would that make any sense?

In other words, while I could cut a 1.5” thick piece, would I be better off cutting two 3/4” pieces and gluing them together. I guess reversing the facing edges so if one warped in one direction the other would tend to warp the other way.

-- Clin

View jerryminer's profile

jerryminer

528 posts in 906 days


#8 posted 10-21-2015 06:40 AM

clin—any chance you could post a sketch of what you’re planning to do? Your explanation has me a little confused—parts that are not structural but “add to the stiffness” of a door and were originally designed as laminated plywood, and are glued to a plywood panel….

View rwe2156's profile

rwe2156

2198 posts in 946 days


#9 posted 10-21-2015 11:58 AM

I would make the first cut like 1 7/8 and if its dead straight, ie. no stress, you can still get 3 more cuts at 1 5/8.
You can do the math, but if you want to conserve wood, this might work.

Safest thing is start out at 2”.

-- Everything is a prototype thats why its one of a kind!!

View clin's profile

clin

514 posts in 461 days


#10 posted 10-21-2015 02:48 PM


clin—any chance you could post a sketch of what you re planning to do? Your explanation has me a little confused—parts that are not structural but “add to the stiffness” of a door and were originally designed as laminated plywood, and are glued to a plywood panel….

- jerryminer

Jerry, thanks, but I’m not looking for more input on the actual application. I’ve got enough cooks in that kitchen already. Just looking for advice on how best to approach creating 1.5” x ~1.5” boards that will remain as stable as possible, with the equipment I have (table saw, no jointer). At this point I’m doing that out of African mahogany.

But, I’m not trying to be secretive here. The primary structure is a steel frame for a large door. This wood is going to be attached to that frame so that a panel can be attached to that. But while the steel and exterior metal panels are the primary structure, the wood will contribute to stiffening the door, especially in combination with the interior panel. Rather like a torsion box. Decision was made to go with something more rigid than just white wood and hopefully something more stable to reduce the chance that this wood will warp the door over time.

As I mentioned, original idea was to use plywood for this, figuring it would be stable, but since some of this wood is exposed on the edges of the door, there were concerns that regardless of finish, plywood might delaminate over time.

At this point, I’m going to rough cut 1/4” over-size, let sit for a week or so. Then final cut. Of course if the wood seems unusually squirrelly, I will modify the approach as needed.


I would make the first cut like 1 7/8 and if its dead straight, ie. no stress, you can still get 3 more cuts at 1 5/8.
You can do the math, but if you want to conserve wood, this might work.

Safest thing is start out at 2”.

- rwe2156

Not a bad idea. Increases the chance the first cut would be usable, and perhaps get the remaining 3, or fall back to getting just 2 more pieces.

I’ve got some time to think about this. Before doing this, I’m going to build some sort of “jointer jig” and actually need to build an outfeed table for the TS before tackling this.

Also, the originally 14 ft board went from 7.5” to 8”. So now that that is cut in half, one board is more like 7 3/4” minimum. So I may start with that one first allowing me to leave a little more extra on the rough cut.

I did select a piece that appears to have very straight grain, as compared to some rather figured pieces, so I’m hoping that helps.

-- Clin

Have your say...

You must be signed in to reply.

DISCLAIMER: Any posts on LJ are posted by individuals acting in their own right and do not necessarily reflect the views of LJ. LJ will not be held liable for the actions of any user.

Latest Projects | Latest Blog Entries | Latest Forum Topics

HomeRefurbers.com