So last night I made a secondary MDF wasteboard with threaded inserts and flattened it. That went perfectly. My spindle could use some minor tramming, but nothing that should cause an issue. This morning I decided to make some hold down clamps to go with it. I had a some oak hanging around of the right size. Threw that in the machine and sketched up a pretty basic clamp in Carbide Create. I was using the stoke #201 endmill that comes with the machine and figured the Carbide team know their endmills and their machines so I was using the stock settings for hardwood. The cuts came out beautifully but for some reason they were not to the proper depth.
My stock is 12.7mm thick and I set max depth to 12.9mm to make sure it fully cut out. However when the cuts were complete I could still see oak and not MDF. Figuring the piece was just a bit thicker in this spot I reran the tool path with the max depth set to 13.1. Still the same thing. Without taking the piece off the board, I measured the depth of the cut using a pair of calipers. 11.2mm??? I then moved the spindle over some solid material and jogged down to Z = 0 in the software. The cutter was well above the stock. I ended up having to move it down by 2.5mm. I checked all the belts and the eccentric nuts and everything was tight.
I reran the tool path over a fresh section of the stock. When the endmill started to plunge into a pocket meant for a bolt hole I heard a dull âthumpâ sound. When that hole was complete and the next cut started about 2mm above the stock. This was the point I started to troubleshoot Z slipping issues. I figured the cut settings in Carbide Create might be the problem and started tweaking things. Once I had that done, I went to zero my end mill. When I did so though I accidentally rammed the cutter into the stock and chipped one of the flutes of the #201 cutter.
I have a set of cheap cutters off Amazon that I planned on learning with. It includes a two flute down cutting end mill. The problem I have at the moment is I really do not understand feeds and speeds all too well. Like I understand what they are, but not how they relate to the material and cutter. Can someone advise a reasonable set of feeds and speeds for this cutter in Oak?
For a 1/4" endmill in oak I would pick a 0.0015" target chipload, so at say 18000RPM with that 2-flute that would require a feedrate of 0.0015 * 2 * 18000 = 54 ipm.
For depth per pass I would start shallow in oak and considering the downcut endmill (poor chip evac) so e.g. 0.05", and plunge at 20ipm or so.
I did not check whether this is even remotely consistent with Winstonâs advice in that video, so in case of doubt follow his advice !
The âfeed and speedâ you need to focus on to minimise Z slippage is your Plunge rate.
An endmill is designed to cut on itâs sides, not on its âendâ. This means if you âPlungeâ the endmill down into the work piece too quickly (especially any harder materials) then the force created before it can begin cutting effectively may be sufficient to make your Z axis miss some steps and miscount your depth.
So I tried using your settings and it still did it. I then tried tightening the belt and it still did it. I took a video of what it is doing: Skipped Steps Maybe.zip (3.2 MB)
No. @neilferreri had it right. The bristles are causing the issue. When plunging the bristles straight down into the work they put up a good fight. Enough that it could cause issues.
I can think of two different solutions. The first is to just heat the bristles with a heat gun and gently bend them outward slightly. 70 degrees should probably do it. The second is to use my 3D printer and print my own âbristlesâ that are shaped more like flaps and made out of flexible filament.
I use clear PVC âcurtainsâ on my 3D printed dust boot so I can see what the cutter is up to, but sweepy is clear so you can do that already.
Alternatively, thereâs lots of folks on eBay selling the bristle strips for making CNC dust shoes with so you can get ready made bristle in various lengths, thatâs where I got my bristle strip, that I still havenât used, from.
For what itâs worth, Iâve heard it sucks (in the good way) with no brush.