Hello All, I am trying my hand at some small PVC letters and numbers and I am headed to Home Depot to grab some 3/4" PVC trim boards. I have quite an assortment of bits and wondering which works best and some basic feeds and speeds. This is a very small project and any advice is greatly appreciated…
Thanks!
Hey @JFab,
I cut some 3/4" PVC awhile back when I was building a screen room, to make locating plugs for the aluminum post material. Worked out pretty well using a 2-flute 1/8" end mill. I really don’t recall the DOC or feed rate (probably about 30 IPM, but I run everything rather conservatively). Just start cutting it, and you’ll get a feel for it. Watch that static when vacuuming it though!
Have cut many plastic parts over the years (1970 til now), before, and with my 1F, my basic rule is keep the feed speed high and the spindle speed low, gotta be careful to keep the work cool otherwise it melts the plastic and balls up on the bit.
Think chip load.
Thanks for the tips! I am hearing that a 0 flute bit is the best thing to use. The little numbers and letters I am making need to be clean cut. I am used to using a compression bit when I do my wood products which keeps the top and bottom cut side clean.
Thank you for the information! I am trying not to ruin bits and experiment to the point where I get frustrated so I am asking for all the help I can get. I love this Forum and the onefinity company
For plastic I always use a two flute upcut as I want to get the hot chips out of the cut. Also I use a machinists deburring tool to clean up and break the edges. You can get a set of them for less than $15.
When cutting PVC, I have not had it melt & stick to the cutter as is common with other plastics such as acrylic or polycarbonate. But Tony is correct in the spindle speed/feedrate advice.
Also the machinist’s deburring tool as well! You will wonder how you ever did without one once you use one.
I wonder how come onefinity support and some other folks I have asked outside of the Forum have said I should use a “0” flute bit for PVC? I sure would like to save the money because I have plenty of 1/8" Whiteside up cut, down cut as well as compression.
First, I’d like to acknowledge that I sometimes struggle with remembering the ideal number of flutes, and feeds/speeds, for various materials and types of cuts. With that disclaimer out of the way, here’s my perspective on the matter. Please keep in mind that these are general guidelines, and I may not be explaining them as precisely as possible.
The primary goal here is to strike a balance known as the “chip load,” which refers to the amount of material removed per flute per pass. The aim is to avoid removing too much or too little material at either too high or too low a speed. With each of these factors being relative to each other. Attempting to go too slowly with too high an RPM often results in the non-cutting parts (backsides) of the flutes rubbing against the material, causing excessive heat, burning, and dulling of the bit.
The number of flutes on an end mill serves two key purposes: First, it determines whether more or less material is removed per flute with each rotation of the bit. Second, it affects the quality of the surface finish based on the material being cut.
Fewer flutes typically mean clearing larger chips per pass, while a 3-flute bit should yield a better surface finish because each flute removes less material. I like to think of this concept as similar to higher grit sandpaper, which removes smaller bits of the surface per pass compared to coarser grit sandpaper that employs a more aggressive approach.
Now, let’s consider materials like plastic, acrylic, foam, and PVC. Many people recommend using a single flute bit for these materials because they are quite soft. If you were to use a 3-flute bit, you’d need to reduce the feed rate and RPM to ensure that each flute is cutting as much material as possible without encountering the aforementioned rubbing issue. This rubbing can cause the material to melt and gum up the flutes of the bit. Unfortunately, most hobby-level routers and spindles can’t go slow enough to prevent this issue while still delivering a usable amount of torque.
I can provide a personal example when I first attempted to cut kaizen foam using a 3-flute end mill. I experienced fraying, stringing, and an overall poor surface finish. The foam seemed to be pushed through and out of the way because not enough material was being removed with each rotation. However, once I purchased a single “O” flute bit explicitly labeled as a “foam cutting bit,” I achieved perfect cuts. The single (and very large) flute efficiently cut through the material without pushing it around.
So, can you use a 2 or 3 flute bit for PVC? Certainly, but it’s not the ideal choice. If you’re not careful with the speed and feed settings, you may encounter issues like material melting, bit flutes getting clogged, and an overall subpar surface finish.