Question for the woodworking experts

[Dotay]

I finally got around to buying a hardwood top that I will use to finish my subwoofer project. I purchased a piece of raw cherry that I'll use to cut a 20" diameter circle and I'm planning on using a 45 degree chamfer bit on the top edge. Here are a couple pics of the wood.

Images not available

My question is what do you think the best way to cut this piece of wood will be? I had planned on using a router and a spiral upcut bit but the guy I bought the wood from was concerned that I might end up burning the wood on the edges. The other potential problem is the piece is almost 1.5 inches thick and I'm not sure my router bit has that much cutting surface although I think it's over 2 inches long. Could I still use this bit to cut through the wood or will I need a bit with a longer cuttting surface? The guy I bought the wood from suggested cutting the circle to within 1/8" with a bandsaw and then use a trim bit around the edge with the router. Any suggestions? Anything I need to lookout for in cutting around the crotch area?

Also I'm interested in suggestions for finishing the piece as well. My tentative plan is to use linseed oil and a wipe on poly. I realy like the look of Brian's big RS 3-ways and how they're finished but I'm also up for suggestions on that as well.

[cjd]

The guy you bought the wood from is smart. Though I would say don't even go with the router, finish this one with hand tools and patience. You can get VERY close to perfect circles on a bandsaw with the right setup. Though you'll need to rough cut to something vaguely circle-ish before the bandsaw I suspect.

With a router, cut the circle close with a bandsaw or similar and use a trim bit to finish. Cut a template to guide the bit. You will need to take care to pay extra careful attention to the grain or your bit will catch and split the wood, thereby causing you much grief. Been there. This may require you flip the piece, and that is where you start running into problems because it's almost always impossible to perfectly re-align the template. So you may need trim bits with both top and bottom guide bearings. You can tack the template to the wood with rubber cement to help keep it in place while flipping etc. but I would clamp before routing.

The crotch area will be a pain due to the grain patterns.

Beautiful piece of wood there.

C

[ThomasW]

It's a beautiful piece of wood, but I'd really like to talk you out of doing this.....

MDF and the solid cherry will have vastly different expansion/contraction coefficents with regard to moisture. If you glue them together it's likely the Cherry will tear apart the MDF as the Cherry changes size with changes in humidity,

The only successful way to do this is by bolting the two pieces together. Drilling oversized holes in the Cherry and bolting it to the MDF will allow the cherry to float on top of the MDF.

[cjd]

The latest Fine Woodworking has an interesting article on finishing. It seems that plain lacquer is actually the best for bringing out the figure and sheen in cherry. Oil will dull it significantly.

So far I have really liked the results I get with Tung oil.

Ultimately, it is probably best to experiment on some scrap to figure out what you want to do finish-wise.

And Thomas is absolutely correct - you'll want to float this piece, not glue it in.

C

[thylantyr]

Another approach to cutting the circle on thick wood. Cut
the circle with a router and circle cutting jig but set the router
cut depth very small, maybe 1/8" cut depth. Make one pass,
stop, lower cut depth another 1/8", make one pass, repeat.
You get the ideaR.... When people use routers to cut hardwoods
they usually do multiple small cut passes to save the router bit
from frying and to not burn wood.

[JonW]

Another approach to cutting the circle on thick wood. Cut
the circle with a router and circle cutting jig but set the router
cut depth very small, maybe 1/8" cut depth. Make one pass,
stop, lower cut depth another 1/8", make one pass, repeat.
You get the ideaR.... When people use routers to cut hardwoods
they usually do multiple small cut passes to save the router bit
from frying and to not burn wood.

Not sure I'd recommend this process with such a thick piece of wood. My experience is very limited. But for what it's worth: I tried to cut a circle through 1.25" thick pine. I used a router and circle jig. I cut the circle maybe half way through, flipped it over and then cut again. The two circles did not quite match up. Maybe my hole for the jig pin was not straight enough (?) because I used a hand drill for that, not a drill press. Later, I tried it again with a longer router bit that could go through the whole thing without needing to be flipped. That worked OK. But your gorgeous cherry might be too thick for that.

But man, that wood is really beautiful. Drool... Whatever you do with it, you'd better do it right.

[Dotay]

It's a beautiful piece of wood, but I'd really like to talk you out of doing this.....

MDF and the solid cherry will have vastly different expansion/contraction coefficents with regard to moisture. If you glue them together it's likely the Cherry will tear apart the MDF as the Cherry changes size with changes in humidity,

The only successful way to do this is by bolting the two pieces together. Drilling oversized holes in the Cherry and bolting it to the MDF will allow the cherry to float on top of the MDF.

Thanks for the heads up in this regard. That was going to be a question of mine down the road once I got it all cut out. The guy I bought the wood from took great care in making sure he dried it properly (took about two years IIRC) and he thinks it will remain straight. I'm not sure if this makes a difference in regards to what you are talking about but I just thought I'd add that bit of info.

I was hesitant to glue the pieces together to begin with in case I ever wanted to use the piece in some other furniture or something and had planned on screwing it anyway. Would you care to elaborate a bit more on what you mean about drilling the over sized holes? Also would you sandwich some sort of material between the layer to help the float and keep them from vibrating against each other?

If I don't use this piece for the subwoofer top I'm not really sure what I'm going to do with it. I'd really like to use it and I'll take all the necessary steps to do it correctly. If that means hand finishing and using a different material other than MDF to attach it I will.

Thanks for the input thus far...keep it coming. :T

Another approach to cutting the circle on thick wood. Cut
the circle with a router and circle cutting jig but set the router
cut depth very small, maybe 1/8" cut depth. Make one pass,
stop, lower cut depth another 1/8", make one pass, repeat.
You get the ideaR.... When people use routers to cut hardwoods
they usually do multiple small cut passes to save the router bit
from frying and to not burn wood.

This is the way I had planned on doing it and also the way I cut my MDF. My thinking was I could always cut it 1/8 to a 1/4" bigger than what I had planned and then trim if necessary. I still might try the bandsaw method if those that know think it might be the more appropriate way to go. The guy I bought it from had a full wood shop and said he'd be willing to help me out.

[Dotay]

Not sure I'd recommend this process with such a thick piece of wood. My experience is very limited. But for what it's worth: I tried to cut a circle through 1.25" thick pine. I used a router and circle jig. I cut the circle maybe half way through, flipped it over and then cut again. The two circles did not quite match up. Maybe my hole for the jig pin was not straight enough (?) because I used a hand drill for that, not a drill press. Later, I tried it again with a longer router bit that could go through the whole thing without needing to be flipped. That worked OK. But your gorgeous cherry might be too thick for that.

I definitely don't want to have to flip the piece because I don't want to have to drill on both sides. If I were to go this route I'd probably buy buy one of the spiral upcut bits #7468 from MLCS. It is a full 3 inches and has a cutting depth of 2". I also have a pretty nice flat bottom bit that I was thinking about using that I bought from MLCS but I'm not sure how deep the cutting surface is. Is there a general rule as to the cutting depth of bits vs the depth of the wood you're cutting through? Also, would using a two flute flatbit like these be better/worse then a spiral bit for cutting this kind of hardwood?

[PaulHilgeman]

Not so sure about cutting it, but as far as finishing goes, with that deep of a natural color, I would just laquer it. Some of the water based laquers are pretty darn good. I like Crystal Lac from McFeeleys.

If you want to add color, use shelac, it sinks in deeper and gives much better figure and depth to the final product.

Use good shelac though.

-Paul

[Ray_D]

You don't need to drill the wood

I definitely don't want to have to flip the piece because I don't want to have to drill on both sides. If I were to go this route I'd probably buy buy one of the spiral upcut bits #7468 from MLCS. It is a full 3 inches and has a cutting depth of 2". I also have a pretty nice flat bottom bit that I was thinking about using that I bought from MLCS but I'm not sure how deep the cutting surface is. Is there a general rule as to the cutting depth of bits vs the depth of the wood you're cutting through? Also, would using a two flute flatbit like these be better/worse then a spiral bit for cutting this kind of hardwood?

You won't have to drill on either side if you bandsaw it first a little oversize and use a circle template and a template/pattern bit first (one with the bearing on the top or with a template guide that fits into the bottom of your router) to do one side. Then you flip it over and use a laminate trim bit (the one with the bearing on the bottom) riding on the previously routed surface to finish the rest. You can do a deeper cut than a single bit can do alone and get concentric surfaces. The template should be clamped to the wood with multiple clamps and they can be moved one at a time to get access.

[Dennis H]

Would you care to elaborate a bit more on what you mean about drilling the over sized holes?

Lay the cherry piece upside down on the bench and center the MDF piece over it. Drill wood screw pilot holes through the MDF and into the cherry. Set the cherry aside and enlarge the holes in the MDF to something like 1/4"-3/8". Then use large washers (small center hole, big outside diameter) on the wood screws to fasten the two pieces together. That will let the cherry expand or contract a bit and the screws can move in the big holes. Assemble the cherry and MDF on the bench and then glue the MDF into the tube.

If you need to take it apart, you'll need someone really skinny to crawl inside the tube, or a very long screwdriver with a steady hand, but it can be done.

Edit: some 1/8" foam between the pieces might be a good idea, both for rattles and to make sure you get a good air seal. Those big holes are potential leaks.

[cjd]

Any router use is still going to put you at risk for a catch and split.

A spiral flush-trim bit will help fight this quite a bit though.

I would still put together a circle jig for a bandsaw and hand-finish past that. Especially if it doesn't have to be a perfect size (i.e. if it's a top, it can hang over the edge some).

C

[Dotay]

Lay the cherry piece upside down on the bench and center the MDF piece over it. Drill wood screw pilot holes through the MDF and into the cherry. Set the cherry aside and enlarge the holes in the MDF to something like 1/4"-3/8". Then use large washers (small center hole, big outside diameter) on the wood screws to fasten the two pieces together. That will let the cherry expand or contract a bit and the screws can move in the big holes. Assemble the cherry and MDF on the bench and then glue the MDF into the tube.

If you need to take it apart, you'll need someone really skinny to crawl inside the tube, or a very long screwdriver with a steady hand, but it can be done.

Edit: some 1/8" foam between the pieces might be a good idea, both for rattles and to make sure you get a good air seal. Those big holes are potential leaks.

Thanks for the description, makes perfect sense now. I read somewhere that wood screws were pretty much the devil :twisted: and to avoid them like the plague. This person suggested that drywall screws were a much better option for numerous reasons so that is what I was planning on using unless someone can give me a better alternative.

Any router use is still going to put you at risk for a catch and split.

A spiral flush-trim bit will help fight this quite a bit though.

I would still put together a circle jig for a bandsaw and hand-finish past that. Especially if it doesn't have to be a perfect size (i.e. if it's a top, it can hang over the edge some).

C

The more I think about the more this seems to make the most since to me. My tube diameter is 18" and I was planning on making the top ~20". When you say I should finish it by hand what kind of finishing are you referring to? Hand sand, belt sander, palm sander, other?

What about my desire to chamfer the top edge? Will I run into the same potential problems with tear out here too? What about a roundover instead?

Thanks everyone for answering my questions thus far. Hopefully with a good amount of reasearch and some test runs on the bottom section I'm not planning on using I can come up with some decent results.

[JonMarsh]

An even better option might be to borrow from the furniture makers, and used threaded recessed brass inset nuts, and furniture socket flathead bolts to attach the Cherry. You can get hardware like that at places like Rockler and Woodcraft, as well as the better local hardware stores. Osh in California carries it, and some Lowe's do, too. Think Danish furniture assembly techniques.

[jdybnis]

What about gluing the cherry board and the MDF together with liquid nails? It doesn't harden completely when it dries.

[PMazz]

If a router is all you have then that's what I would use. If I had to do it, I'd throw it on my bandsaw circle jig to rough out and belt sand the edges to clean them up. Routing solid wood is fine IF your bits are sharp, you take your time and know your wood. Routing a circle in solid wood means you'll be going against the grain on half of the cut. Small bites and/or taking it close to size before routing help immensly. Larger diameter bits will help as well. So if I had to use just a router, I would start with the top down and use a circle jig to rough out a blank to 1/4" larger than finished size. Then set the jig to size and route to get you down to 1/4" deep. Then switch to a flush trim bit and work from the top taking off small shavings until the bearing finally contacted the routed bottom edge.

Glueing solid wood of that size to MDF will cause problems. I usually use screws. You can glue/screw the center of the piece along the grain to make sure any movement will be equal on each side of center. For the perimiter holes I pre-drill and then open the back side of the hole up with a larger bit, only drilling half way thru. This will allow the screw enough room to flex. You may have to still ose washers so you don't pull the screw thru the MDF.

Pete

[cjd]

Ahh, a real expert chimes in.

Also, drywall screws could be bad news. They shear. They don't have a lot of flex. Very hard and brittle.

brass inserts + bolts is the way to go without a question.

Or just use industrial strength velcro to hold the whole thing in place.

C

[Dotay]

An even better option might be to borrow from the furniture makers, and used threaded recessed brass inset nuts, and furniture socket flathead bolts to attach the Cherry. You can get hardware like that at places like Rockler and Woodcraft, as well as the better local hardware stores. Osh in California carries it, and some Lowe's do, too. Think Danish furniture assembly techniques.

This sounds very similar in principle to T-nuts. Am I close?

So if I had to use just a router, I would start with the top down and use a circle jig to rough out a blank to 1/4" larger than finished size.

I've read this several times and I'm still not quite sure I'm following what you're saying. By top I'm assuming you're talking about the piece of cherry correct? When you say rough out a blank are you talking about making a "blank" out of say MDF that's 1/4" bigger than what I want my finished cherry top to be?

Then set the jig to size and route to get you down to 1/4" deep.

Not sure what you mean here...I guess I need the top question answered before I can picture what it is you're talking about.

Then switch to a flush trim bit and work from the top taking off small shavings until the bearing finally contacted the routed bottom edge.

Are you talking about a bit with a bearing at the top or the bottom of the cutting surface?

Or just use industrial strength velcro to hold the whole thing in place.

Way to think outside the box. :B

I think like the brass insert idea the best so far as far as bolting the two together assuming it's what I've got pictured in my head. Where/how many inserts should I use for something like this? Do I want to use fewer so it can have a chance to move if it needs to or do I want to make sure it's fastened down tight to it doesn't rattle? I guess a layer or thin foam or something like dynamat would help with that though right?

[EdL]

Consider the material outside the circle you want to keep for what it can teach you. You have the opportunity to learn on your way to the "final" size by practicing on the material that will be wasted. Don't try to get there too fast. Use the waste to learn how the router behaves as you make your different cuts. I think you want to build your confidence before you get there. Present the router to the wood in a gentle way...if you do so the wrong way the wood will protest! Expect the grain in the crotch to be the hardest and most likely to burn.
Take some scrap pieces and join them together with silicone caulk. You won't need clamps or 100% coverage. Test it several days later to see if you think the holding power is sufficient.

[Dotay]

Consider the material outside the circle you want to keep for what it can teach you. You have the opportunity to learn on your way to the "final" size by practicing on the material that will be wasted.

No matter which way I go I'm definitely planning on utilizing the scrap to test both cutting techniques and finishing options. One of the things I'm slightly worried about is the fact that the part I'm experimenting on won't have much of the crotch extended into it so I won't get a true feel for how it's going to react. It'll be better than nothing though and I think it'll give me a good idea of how the wood will act while I cut it.

[Dennis H]

I like Pete's method of only drilling halfway through the top side of the MDF. Then you'll get a good air seal between the screw and the MDF and won't need any foam. Threaded inserts are really overkill for this. Screws strip out of MDF easily but they're hella strong in hardwood. And with Pete's method, you're counting on the screw bending as the hardwood shifts. That won't happen with bolts so you're back to the problem of drilling all the way through the MDF and maybe not getting a good air seal. Drywall-type threads are good but you want a round or pan head to use with the washers and probably something a bit bigger in diameter than normal drywall screws.

[Paul H]

Almost OT here, but I've seen screws mentioned a few times in this thread.

The benefit of drywall screws is that they have sharp coarse threads that hold well in mdf and other particle board. As noted above though, they're brittle and standard sizes are too small.

Use "particle board screws" for fastening into mdf, particle board and soft solid woods. They are made with the same steel in the same sizes as regular wood screws, available in flat or tapered heads in any decent hardware/lumber store including the big box places, and have threads designed to hold in the 'less sturdy' wood types.

Paul

[thylantyr]

Not sure I'd recommend this process with such a thick piece of wood.

The process works.

My experience is very limited. But for what it's worth: I tried to cut a circle through 1.25" thick pine. I used a router and circle jig. I cut the circle maybe half way through, flipped it over and then cut again.

Flipping the wood is the problem here, there is no
flipping in the process I described, just make sure you
you enough router stroke.

[PMazz]

I've read this several times and I'm still not quite sure I'm following what you're saying. By top I'm assuming you're talking about the piece of cherry correct? When you say rough out a blank are you talking about making a "blank" out of say MDF that's 1/4" bigger than what I want my finished cherry top to be?

Top down means better face of cherry face down. Route a circle 1/4" larger than desired from the cherry stock as your blank. Now you'll only have to remove 1/8" material to get it to size.

Then set the jig to size and route to get you down to 1/4" deep.

With your blank still face down, set your circle jig to the final size and route until you've achieved a 1/4" deep cut around the perimeter of the blank.

Are you talking about a bit with a bearing at the top or the bottom of the cutting surface?

A flush trim bit has a bottom bearing, a pattern cutting bit has a top bearing. You could use either one but most folks have flush trim bits. I like a 3/4" pattern bit for this type of cut myself. If you use a flush trim bit, you'll need one with ~1.5" carbide.

Pete

[kvardas]

Crotch wood can have spectacular figure, but tends to be very unstable and prone to cracking. If you want to route in crotch figured wood, I suggest using a very sharp bit, route with the grain, if possible (this is contrary to most routing procedures), take a small depth of cut, and use multiple passes. Cherry also burns very easily, so be careful to not stall quickly. I would also suggest keeping it out of hot, dry areas to prevent rapid drying/moisture loss.

Cherry will darken naturally over a period of time into a deep reddish brown. Some people choose to stain the cherry. IMHO this is a mistake, as it will degrade the natural chatoyance (sp. ?) that unstained figured cherry has. Finally, cherry is closed-grain like maple, and will an oil/varnish finish well, if you do not want to go with lacquer.