Projects MDF vs HDF

I'm wanting to make a buck to fab some panels. Curious if I would be better off with one over the other. FWIW, I'm wanting to make multiple copies.

 

In the past I did a lot of stuff with MDF, and some with HDF. The HDF is heavier (in my experience more that the attached quote shows), but it finishes to a nicer sanded edge. Unless you need that or a generally stronger piece (you going to check fit or hammer on it?) I wouldn’t pay the price or fight the weight for HDF.

Lifted from the net.

“HDF is denser and heavier than MDF due to its smaller and more tightly packed wood fibres. HDF typically has a density of around 50-65 pounds per cubic foot, while MDF has a density of around 30-50 pounds per cubic foot. HDF is stronger and more durable than MDF due to its higher density and smaller wood fibres.”

 

Are you making a buck or a hammer form? It sounds like when you mention making multiple copies you are wanting a hammer form. A buck you offer the metal up against to check if you have the right shape so you could make infinite copies as all it is a shape form and should last forever. A hammer form has to hold up to being hammered on.

 

Hammer form.

 

Both those material will chip on the edges. For repeated use I’d ask around, I’m thinking plywood might be a better choice. I don’t have enough experience to say for certain.

 

I tend to agree with plywood. MDF as a finish carpenter I have used it many times.
It is wonderful stuff to cut down and use a router on and make incredible looking painted fireplace mantels or other types of trim. .... It is easy to work with and could make a very nice buck.
It paints very nicely and is used often in high dollar homes for custom trim. .... There is a different version of mdf that actually works well for painted exterior signs .....

As a Buck for fenders, as soon as you start pounding on it the fibers will loosen and collapse and change the shape of the project you are working on.

Good quality plywood is what I would use .... They even make better quality where it is smoot on one side .... doubt that is worth the extra $$ .... Same as if you bought smooth cabinet grade plywood ... is only a cheap veneer over the plywood and would fail as fast as mdf. .... Better off with plain old plywood.

Working with mdf we had a nickname for it .... Mother F'n Dusty.
You cut, sand, shape it and it leaves 4 times the amount of dust that plywood will .... but it is so soft and easy to shape it looks great for painted house trim.

 

What are you trying to make and how many copies do you have to make? MDF will work as a hammer form. I have used it many times, made multiple parts with the same form and it has worked very well. It is super easy to work with and relatively inexpensive but it does break down eventually. How quickly will depend on how you are using it for a hammer form.

 

Any of that fiberboard stuff is subject to swelling and deforming when wet (like when it rains).
But if you are really stuck on 'fiber', the flooring underlayment type is treated to be a degree or two better at resisting water issues.

 

I used 3/4" plywood and was able to use it several times without degradation. I was using 20 gauge metal.

 

I'm making a header panel for my 34 Dodge coupe.

 

I have never had a mdf hammerform not be useful for at least 2-3 copies minimum unless it was something where the edges of the steel were digging into the form.

If you are not going into production I would say mdf would be fine.

 

When the quan***y increases, I would look at Delrin or Aluminum.

 

One could coat the MDF or HDF with thinned down JB weld with acetone or lacquer thinner allowing it to soak in and create a harder surface.

 

Whether using MDF or HDF you can increase the durability and make it very water resistant by using the method big duece just mentioned.
I have done similar but instead of JB weld, I use ABS plastic that has been dissolved in acetone. Start off with a thinned mixture that will penetrate deep into the fibers and then use subsequent coats of a gradually thickened mix. This allows a great bond and adhesion in between coats. Very inexpensive, durable and moisture resistant. I always save my ABS plastic sheet s****s just for the purpose of making this mix when needed.

 

Fascinating. Thank you. I learned a whole lot right there. Never would have imagined mixing up ABS and acetone.
I will have to do that.

 

In regards to ABS or styrene, the M.E.K. solvent is probably a bit hotter than acetone, but it's dangerous stuff to breath.