Router Forums banner

Mortising bits vs straight bits

17526 Views 10 Replies 7 Participants Last post by  Terry Q
I am in the process of designing and building a new router table/cabinet. After searching, it seems the preference, to many, is laminating 2 pieces of 3/4" mdf together and then adding laminate skin. I will be inletting for t-tracks. I am unsure what router bit to use for inletting the grooves for the t-track. It is my understanding that mortising bits have some shear angle. Seems that this would help eliminate possible cracking of the laminate skin and create a smoother finish in plain wood. I have a couple of straight bits, a couple of straight bits with top bearings. I also have some HSS spiral end mills with 1/2" shanks.

I have never routed any MDF. I am aware that MDF is rough on people and it's rumored that MDF is rough on bits.

Should I use a straight bit, mortising bit or end mill? Are mortising bits worth the extra investment?

I sure would appreciate any information about the differences between the two bit designs.
BTW: I'm fairly partial to Freud.
1 - 11 of 11 Posts
Hi and welcome. Usually if the laminate is well glued you won't have an issue with routing it. I wouldn't use any bit with an upward shear angle, downward would be okay. Straight will also work. I wouldn't worry about very minute chipping because when you are done you'll probably need to take a flat file and run it down the cut edges at about a 45* angle to get rid of any burrs on the edge. The tracks should be exactly 3/4" so a 3/4" bit should do the job in one pass.
  • Like
Reactions: 1
welcome N/A to the forums...

I used a single thickness of torsion frame supported laminate covered AC fir eons ago and have had no issues......
you'd be miles ahead by using a ready made piece of laminate covered ¾'' Baltic Birch...
it'd be a one time deal and here's a bit of information on Baltic Birch... please don't confuse Birch plywood and Baltic Birch..

now, about that MDF...

Low on strength:
Particle board anything is quite weak compared to other kinds of engineered woods such as plywood. It is less dense and can easily get damaged while handling. It's important to note that their particle board anything just doesn't survive much of anything.

Low life, low durability:
Apart from being low on strength, particle boards are also prone to getting damaged because of moisture and humidity. This means that items made from MDF will not last very long. This is without doubt the major drawback...
Experienced sources and even some shopkeepers selling these particle board furniture clearly inform the customer that they can expect the particle board furniture to last for around 2 to 3 years (and there are others who will say the lifetime is 5 years). Now compare this with plywood which lasts easily for 15-20 years, or with good quality solid wood furniture that lasts for several decades and is handed over from one generation to the next.
Finally the choice of wood depends on the needs of the customers, whether they want cheaper furniture that they are willing to dispose off in the next few years or they want furniture that want to buy once and that which will last a lifetime.

Cannot support heavy loads:
Particle boards are almost never used in applications where the boards will be subjected to heavy weights. Being low on strength, particle boards are only suitable for holding low weights, or as forming the walls of cabinets and the like.

Not as eco-friendly as solid wood furniture:
Particle boards are made from small particles of wood such as sawdust and small chips which are glued and pressed together to form a sheet. The glue used is a plastic resin (phenolic resin), the same that is used in the making of decorative laminates. This is not as eco-friendly as using good quality solid wood furniture that is 100% natural.

So, to summarize the discussion, I would say that the only major advantage of particle boards is that its cost is very low compared to all the other types wood available in the market, and the major disadvantages are its low strength and low durability.
Best to avoid damaging or removing the surface, as the surface is quite different to the inside and it contributes to the strength...
MDF is basically glorified particle board.
Basic MDF is not very good at handling high moisture levels. Water begins to degrade MDF into fine particles, think wet cardboard. Because it consists of such fine particles, MDF doesn’t hold screws very well, and it’s very easy to strip the screw holes. Humidity alone can cause it to puff and crack.
MDF is not a long term product. MDF crumbles easily, so finding pieces that have a clean edge are hard to find.
MDF is not as strong as plywood. It is not suitable for most joints
MDF dust from working it is horrible and it contains toxic VOCs (urea-formaldehyde). so wear a mask. Cutting this material will cause faster blunting of bits and blades as compared to wood
MDF is rarely the best material.
MDF is a pain to work with if you have to remodel later or install hardware several times, as the more you drill it, the less sturdy it becomes and begins to flake.

Verdict: Use anything else, seriously. MDF is cheaper, but you will pay for it in the long run. Especially true for cabinets, as weight of the wood will decrease the amount your cabinet can hold, plus MDF will begin to sag from stress.

Hey!!! it is initially cheaper than plywood...

Medium density fiberboard is weak compared to wood. This means that when you install the medium density fiberboard, there is a good chance that it could split or crack. It is not very durable when compared to the real thing. When you are installing it, you need to be very careful and make sure that you don't break it.
Since the medium density fiberboard is not as dense as real wood, you will have to use more nails when installing it. If you do not place nails at close intervals, the board can droop in the middle leaving you with what looks like an amateur installation.
Another problem with medium density fiberboard is that it does not take nails very well. When you hammer a nail into real wood, the wood will move out of the way and then come back around the nail. When you nail into medium density fiberboard, this will not happen. You will get a "volcano" effect on the outside of the medium density fiberboard. When this happens, you will need to sand down the outside of the MDF. This will result in you having to do a lot more work than you would have had to do if you purchased real wood.
See less See more
  • Like
Reactions: 2
There is a lot of existing information on this site about router tables, both how to use them and how to build them. Here are 3 links to check out.

Router Forums - Router and Woodworking Discussion Community
Router Forums - Router and Woodworking Discussion Community
Router Forums - Router and Woodworking Discussion Community
Welcome to the forum to the new fellow. Hope that Mr. Sticky and Charles help you in your project.

Wao, Mr. Stick.
That was a magnificent explanation about mdf issues. I use it seldom.

BTW, Merry Christmas to you all.
Welcome to the Forum. I'm not a fan of MDF for all the reasons Stick outlined. I do keep a little bit of it around, cut into squares or rectangles to feed pieces through the table saw or router table. Stops chipout, cheap. You can also use ply for that purpose. Definitely wear a mask, not just when cutting MDF. Keep the mask on until the air is filtered clear. I avoid cutting MDF indoors--nasty stuff.
Dunno about all that stuff Stick said, but I used some once. Once. And absolutely hated it.
I appreciate all of the info. Yes, I am a firm believer in Baltic Birch. I was considering MDF, for the top, ONLY. My reasoning was: I am installing t-track into the top. Do you think a 3/8" or 1/2" deep cut into the 23/32" Baltic Birch top would weaken it enough to cause a problem? I have not ruled out the idea of building a torsion box for the top. Weight support is not going to be an issue. The cabinet box will be 3/4 Baltic Birch. I have an old steel frame, made from 2" square steel tubing. The frame is 26X46, just right for a cabinet with 32 X 53 top. This will give me a little hang over for clamping, if necessary.

Over the past few months, I have been gathering parts and pieces. I got one of those Incra LS25 positioners at an estate sale. The thing is brand new in the box and the price was super right. This past Wednesday. I found a guy selling his woodworking stuff out of unit in some mini-warehouses. I got a Jess-em Mast-R lift, looks new, and a used Bosch 1617EVS router, plain with no plunge. I figured that I would build the table around this stuff.

Anyway, back to some torsion box questions.

I have studied a little on torsion boxes. Seems that each opinion varies on construction. 20 different people give 20 different answers. If I used 3/4 VC Baltic Birch for the top, what should I use for the bottom skin. I would "ASSUME" Baltic Birch. If so, what thickness? What material should I use for the core? What would be the minimum thickness of the core? I have seen some folks say 3" is sufficient, others say anything less than 4" is a waste of time. Should the core be of a "Bridle" joint construction or separate pieces?

I know, lots of questions. When I build something, I want it to last 2 lifetimes.
See less See more
The problem you'll have with any panel board is the span. Panels are not meant to cross spans. They will sag even under just their own weight eventually. It's not the material that is important, it's the engineering that goes into it that is.

Here is an example of a table I built that was only meant to be a temporary one that I planned on abandoning when I moved back home from northern Alberta. I had a piece of 5/8" melamine coated particle board left from a project that was the right size. I had never tried using t tracks so I wanted to try them for holding the fence so I grooved the top for them which only left 1/4" of panel under them. This table sat in a shed that had temperatures go from over 100F to below 40F and major changes in humidity. I kept it for about 4 years like that and gave it to my son in law for at least another 2 years before he moved back. I took it apart when I helped him move and it was still dead flat.

The reason for that is that I had it on a solid wood frame that had cross members close to the router plate and I had the grooves over or very close to frame members. I've never used more than 1 layer of any panel to build a router table and I'm on my 6th or 7th now and I've never had a problem with any of them. The rest were all fairly simple but the latest one I needed storage so I built it on a cabinet or I wouldn't have bothered updating from the last one. If you ask most of the people advocating that you must use two layers they would also admit to you that they never done it any other way. I'm the exact opposite. I've never used two layers because I've never had a problem just using one.
See less See more
  • Like
Reactions: 1
I have studied a little on torsion boxes. Seems that each opinion varies on construction. 20 different people give 20 different answers
OK, now 21 answers. I don't have a torsion box under my top, but I do have a spider web of chunks of 2X4, which probably amounts to the same thing. My top is 1/2" plywood. I'm not sure just how long it has been since I made it, over 10 years for sure, and no warp or anything yet. I think the biggest gap I have under there is probably about 3". It isn't fancy, but does just what I need it for.
I have the same set up, it requires a fairly deep router table. The Incra instructions will tell you how far to base needs to be mounted from the bit opening.

I made my router top using 3/4 inch plywood, nothing special, laminated to 1/2 inch mdf on top. I used plastic laminate on both the top and bottom, after bordering the top with a fairly wide piece of oak so I could round the corners. I used cross members under the top as close as possible to the opening for the lift. I also used a Rockler “dust bucket” for dust collection, so I had to leave room for that.

In woodworking there is always more then one way to accomplish something.
1 - 11 of 11 Posts
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.