Teardrops n Tiny Travel Trailers

I have an old dado blade set and a molding head set (with various profile cutters, including a rectangular set of blades that are described as "jointer/planer"). They are both older Craftsman brand and were left behind by my dad who used them in an old Craftsman radial arm saw. I never used them before, but experimented with the dado set tonight getting ready to make some 3/4 wide x 3/16 deep rabbets in soft pine boards. (More details in my build thread here.)

The dado set isn't cutting very cleanly and smoked a bit when I used it to plunge cut the table insert that I made. I'm sure the side blades could use a good cleaning, though they don't appear to be damaged or horribly dull. I did notice, after installing, that one of the rake blades is chipped and I should swap that out for one of the others and try again.

My questions are:
1) What tricks and/or standards do you use to get a good clean rabbet or dado when using a stacked blade set?
2) Is the molding head a suitable option (or not) for making rabbets? If so, any advice on set up and use in this application?

TIA

You don't absolutely have to have a dado set to cut rabbets or dados. Several passes with a standard blade will do the trick. Otherwise, chances are your non-carbide blades are dull, and you will save yourself a lot of time and hassle by simply buying a carbide dado blade set, as opposed to trying to have them sharpened. These can be found in 6" or 8" size and cost between 50 and 100 bucks.

KC,

I don't have much to offer other than a few tips below which you probably already know:

1. Be sure to stagger the outer and inner chipper blades so there is no contact of adjacent blade teeth.
2. If you use spacers or shims to get the correct width of the dado, don't place them side-by-side. They should be alternated with the blades.
3. Have plenty of scrap wood of the same species as your finish materials so that you can "sneak up" on dado width and depth.
4. Experiment with rate of feed. You want to keep the blade rpms up and not bog down the saw, but you also don't want the feed rate to be unnecessarily slow that the blade teeth remain in contact with the wood too long. It can be a balancing act.

It doesn't take much resin build up - less than what is visible - to cause saw blades to drag and burn/smoke. There is a lot of discussion pro and con, but I've always had good luck cleaning my blades with Simple Green and a brass brush.

Sometimes incorrect table saw setup can contribute to burning of wood. I'm referring to making sure that your fence and miter gauge slot are parallel and perpindicular to the centerline of your saw blade spindle (or saw motor depending on the type of table saw you have.) You may not notice incorrect setup on a standard saw blade but it could become apparent using a dado blade.

When I check my table saw, I use the miter gauge slot on the left side of the blade as the reference point. I attach a 1/4" thick machined steel plate to the blade spindle. I have a jig that fits in the miter slot that holds a dial caliper and I measure both sides of the reference plate and adjust the saw until they are the same distance. (How you adjust depends upon the saw. Cabinet saws are the easiest because you adjust the table rather than for almost all others you have to adjust the spindle or motor.) Then I set the fence parallel to the miter gauge slot. (Actually I tow it out a few thousandths at the outfeed side.)

Lastly, you may want to check runout on your saw blade spindle (or motor.) Too much runout can cause burning although usually it will just cause a wider cut than the saw blade.

Take care,
Tom

When I was outside sales for a local lumber yard I always liked stoppin' in at Ol' Charlie's cabinet shop. This old cigar chewin' wood wizard had a tiny cabinet shop but put out some exquisite (high dollar) custom cabinets. I caught him dressing a dado set with silicone spray. He would hand turn the blade set while spraying at a 45 degree angle to the left and then the right. He said it cut down on tearout and burning. I asked him if he had problems with the spray when it came time to stain and finish his project. He told me most areas where he had rabbeted and shaped were not in the direct eye but he would clean with isopropyle alcohol and burnish with dry unscented un colored powdered soap then rinse with water.

Woodywrkng, Those were my thoughts, too. The new carbide set is probably the answer.

Tom, Although we did not check parallel with a dial indicator, we did go to great lengths to get it very accurate to the blade as best we could using a tape measure (down to less than splitting 32nds. The spindle had no visible run out or perceptible free play in the bearings. Unfortunately the new 10 inch blade measured +/- 0.010 with an indicator. Each setup I am very careful to triple check the fence is parallel to the slots, again down to splitting 32nds with the graduated eyeball. The ground reference wheel is a great idea for checking arbor vs blade run out, and for setting the table true; that would eliminate flex and a variable. I think the real issue I'm seeing with the quality of the cut is the condition of the rake blades (one in particular). I'll swap that out first, and if it doesn't work, either buy a fresh set, or switch to the router.

Bob, I was thinking cutting wax might be okay... or neatsfoot oil, just because I have it handy. Sometimes listening from the old masters yields the best "dope" (i.e. specification for precision).

All good advice from earlier posters. I will add three things:

1) Silicone oil is a terrible thing to introduce to a shop if you ever intend to use lacquer. It causes fish-eye (little bubble looking eruptions in the finish). It can be terribly hard to repair because you can't ever seem to get rid of the silicone-even if you sand down to fresh wood. Once introduced you may forever have to use an additive such as 'Fish-Eye Buster' in your lacquer.

2) If you opt to re-sharpen the dado set you have make sure to sharpen all the blades, not just the dull ones. If you only sharpen the dull ones you end up with uneven depth of cut.

3) I have a Craftsman molding head which I only use in dire emergencies. At best, a molding head in a table saw or radial arm saw is a poor substitute for the right tool which may be a molding machine, a router, a shaper or a planer. The big issue is that a saw simply does not generally generate enough speed to do a good job.

Best,
Tom

Keep in mind that if you do not have the cutter heads properly secured in the base, they can eject a head and cause major damage and/or injury.

I never did resort to the molding head. The thought of flying chunks of metal had occurred to me (... I was going to say "crossed my mind", but decided not to tempt fate by being punny).

Thanks for the advice, everyone.

Tonight I tried swapping out the bad rake blade. It didn't really improve things much, so I went ahead and used the router table with a straight cutter to make the rabbets. Much better results.

For what I need right now this will do. If I decide to remodel my kitchen or bathroom cabinets I might get a new/better dado set, but I don't really have much more need for it at the moment.

Thanks again for your input!

Not that anyone mentioned it...but steer way clear of the "wobble" dado heads as well. They are junk! Just my experience. Doug

Danny, Glad you get by with using silicone spray. I've had one bad experience with it and that was enough. My views on it were shaped by that and from reading Bob Flexner. By the way, I love kimchee--even make my own here at home.

Best,
Tom