Melamine Chipping and Drill Bit Selection

      Chipping problems encountered while drilling shelf holes on CNC equipment could be fixed by changing to carbide bits, or could be related to panel quality. March 26, 2009

I am currently using brad point drills for my shelf holes, but am finding that the melamine surface is getting pulled up and is chipping. Should I consider a different drill type?

Forum Responses
(CNC Forum)
From contributor S:
Get the carbide tipped ones that are meant for hinge boring machines, like the Blum Mini Press. The shank on it is larger, and drills a 5mm hole.

From the original questioner:
I'm aware of this. I'm using a CNC, not a hand drill. The question is what tip works best.

From contributor S:
I use them in my CNC all the time and they last quite a long time.

From Brian Personett, forum technical advisor:
I'm a big fan of solid carbide bits. I've messed around with V-points, but brad point is the way to go unless you're through boring.

From contributor E:
Us a carbide tipped brad point drill, with the shortest length possible.

From contributor M:
Make sure the spurs at the outer edge of your bits are sharp! They have to be able to score the hole before material is removed.

From the original questioner:
What about speeds? I'm getting frustrated because I've tried most of these things, with the exception of the solid carbide drills, and I'm still getting major chipping. I'm currently running them at 4000 rpm, and have tried several feed rates. I have the machine set up to do 2 pecks for each hole.

From contributor S:
I have been doing mine at 12,000 rpm, but a slow feed rate. I think the feed rate is 75 ipm.

From contributor C:
We use all 70mm oal BP drills at 6mpm and 6000RPM.

From contributor G:
What contributor C said is what we see the majority of time in shops.

From contributor W:
We have been experiencing similar problems here in our shop in eastern Canada. Adjustable shelf holes were chipping out on melamine, but looked clean on veneers. After trying numerous bit types and speeds, we talked to our melamine supplier. Turns out that because of the difficulty in sourcing softwoods for the core material, our supplier and many other suppliers have switched to a hardwood particle core. This creates more chipping in both drilling and cutting. They suggested using bits designed for drilling hardwoods. We have not tested the recommendation yet. I would talk to your material supplier.

From contributor U:
I think the RPM that you are running is a little high. Try cutting it down slowly, do not jump all at one time. Also, you mention that you are running on a CNC. Not sure how you are holding the bits, but you may have run-out in whatever you are using or in your spindle. Also, the board that is coming from China is causing issues.

From contributor K:
I am running 4400 RPM at 300 IPM with good results in melamine, VC, MDF and pre-laminated sheets. This may not be optimum for each material individually, but it seems to be a good compromise for all materials and bit diameters from 5 to 35mm, although I know I am pushing it on the 35mm in pre-lam. I strongly prefer solid carbide, for stiffness and durability, especially at the 5mm diameter, but the carbide tipped bits work well enough. I have found most manufacturers of CNC machines recommend 70 mm length bits, but I almost never have a need for that length. The 50mm length bits seem to flex less at the tip and do the job for every hole I have had need to drill in sheet goods for as long as I can remember. I use these for through-drilling on partitions as well with no visible chip out in nested operations.

I think your problem may well have to do with run-out from the bit backing out of the hole. Try just drilling in one test bore and stopping. If the chip out is gone, then try a full cycle. I bet the chipping is back. I also bet that if this is the case, solid carbide drills or shorter lengths or both eliminate the problem.

From contributor M:
I've said it before and I will say it again. Whether it is melamine or laminate, as they age they become much more brittle and a lot more likely to chip. If you are buying pre-laminated panels it is possible your supplier does not rotate stock, thus you got the bottom of the pile, or that you needed something they don't sell often and sits in their racks.

The aging process to become brittle is only a couple months at most. As for melamine, another factor is, whose melamine is being applied to the substrate? Different brands differ greatly as to how pliable and likely they are to chip or not. Talk to your supplier and get answers to these issues.

From the original questioner:
Solid carbide drills made all the difference in the world! No chipping at all in the same material.

From contributor L:
I think the melamine is your issue. Been there, done it. Talk to your supplier or change suppliers. We try to stick with Roseberg from Montana or Mississippi. Yeah, we request it from these two places and get it at 20-40 pieces every three days, rotating our stock.

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