I am re-using some baseboard trim to make drawers. The baseboards came as a single batch. I measured the first section … and assumed (my bad) that the material would be the same thickness. It is MDF, a manufactured product. I would have bet money that it was the same thickness throughout. I would have lost … the second chunk (this is 3.5 in by 1/2 in baseboard) was a full mm thinner !
Surprised the heck out of me … I mean the production line is set up and it doesn’t magically change …
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Different suppliers or factories ?
Yeah, that’s probably the reason. Very annoying though …
@Jens If it is stored in high humidity or very cold, MDF will move that much.
Not that it was exposed to cold or humidity but are you saying that MDF that is 13mm thick can shrink to 12 mm from humidity or temperature changes? I can see it going the other way (from 12 mm to 13 mm) if it got wet …
I use a lot of MDF in my climate controlled shop for jigs, molds, and templates in guitar building. I used to be able to measure one spot on a 4x8 sheet and use that thickness for the entire milling process. I have noticed over the last 6-8 months that consistency has gone way down and that single measurement is no longer viable. This has been from a couple of different suppliers too.
I am extremely surprised that this is an issue. I can see it with plywood since it is made up of layers which are pressed together and heat cured. Any sort of variation will not be evident until the sheet comes out of the press and then it’s too late. MDF though is a very controlled process and once the production line is set up, there is no reason to change anything until another product is run. Even with a change-over, because it is such a controlled way of manufacture, it is hard for me to understand how a variation in thickness beyond maybe a tenth of a mm can happen. Maybe my understanding of the production process is wrong (I am assuming it is a continuous process similar to for example drywall production)
Anyway, thanks for confirming that this can indeed be an issue.
On a side note, while I was surprised that there can be a variation with different batches or suppliers, I am amazed that there would be thickness variations in the same panel.
On a side note…I was a Wildland Firefighter, and during the shoulder season,s we would travel around the US West to do thinning projects. This one place(can’t remember exactly where) was a small factory for MDF and plywood. They used to have all of their bay doors open during the hot months, with giant fans going on with stacks and stacks of their product outside under large roofs(They also had large enclosed warehouses). Not sure where it was going, but I did look up the company at the time to see what kind of operation was going on. The smell passing by it every day was not pleasant.
A couple of my first test projects with my machine, I had some of the same issues. I have decided that it might be better in some cases to use the “machine bed” in Vcarve Pro instead of the typical “material top” as the reference. Of course this doesn’t work for all projects so YMMV.