Pockets cutting too deep (repost)

[Saki (Ikas)]

So, 2 of the pockets cut the proper depth as set (.25")…and the last one cut much deeper. I had the toolpath set to exactly .5" (half an inch) and once it got to that depth, it just kept going deeper and deeper until I hit pause before it busted threw the bottom.

-I’m using bit zero
-I made sure the material thickness was set properly at .72
-I made sure the max depth of the pockets was set properly at .5

Since others worked fine, what could be the issue?

See attached.

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[arose87tags (Marc Jensen)]

I’m wondering if the bit was tight enough in the collet.

[WillAdams (William Adams (Carbide 3D))]

Possibilities:

• misconfiguration in Grbl (that should not be possible on an SO5 Pro, since the board is identified by CM and the HDZ is the only option
• wiring fault — usually this is accompanied by an awful noise — power up, wait a bit and feel each connector, any which are warm/hot would indicate high resistance from a loose connection, check in w/ support
• insufficient lubrication — make sure the linear rails/blocks are well-lubricated: CNC Machine Maintenance
• mechanical interference causing lost steps on retract
• as @arose87tags noted, possibly the tool loose in the collet and pulling out — use a good quality pair of wrenches to fully tighten
• high tooling engagement causing the machine to be pulled into the cut, or to lose steps on retract — where possible avoid slotting and add geometry and cut as a pocket

Making vacuum hose adapters

While cutting up vacuum extension wands for this is expedient, it’s a bit problematic given that Shop Vac recently filed for bankruptcy, was bought at the last minute, and production hasn’t caught up. I need a receptacle for the Sweepy 2.0 dust fitting — one option would be to purchase one from Woodcraft, but Carbide 3D sells blocks of HDPE: which looks to be just barely big enough for things to fit. Measuring the hose fitting I get a diameter of ~63.5mm — offsetting that twice we arrive at…

and/or

Adding geometry to cut as a pocket with a finishing pass

One technique which is often suggested to avoid slotting is to add geometry around a part which one wishes to cut out and cut as a pocket down to tab depth — here’s one technique for that. In this case, the project is a bevel gauge which will be cut out of 0.0625" (~1.5mm) thick aluminum: [bevelgauge] Due to the narrowness of the angles, an 0.03125" endmill has to be used, so after importing and scaling the file (we will be cutting out one which is 3") we select the perimeter and offset it tw…

and consider leaving a roughing clearance and taking a finishing pass.

Best Bit for full cut through

One which has a cutting flute length equal to or greater than the thickness of the stock — pretty much any tool should work. Big thing is the toolpaths — if cutting out, rather than just cutting a slot: [image] Offset to the outside by endmill diameter plus 10% or so: [image] [image] [image] Then cut as a pocket: [image] down to tab height or the penultimate pass: [image] then move the contour down to below the pocket and start cutting at the bottom of the pocket: [image] and…

[Saki (Ikas)]

I’ll try these suggestions, but in the mean time, I have two questions:

1. What is the best bit for quick, rough pocketing of a .5" deep 4x4" square in soft wood…and what would be the feed rate for ply or pine? Assuming I do a final pass (slowly) to make the final inside perimeter cut and final layer (maybe .05 depth) of the wood, what would be the best finishing bit?

2. What is the reason for linking the “making a vacuum hose adapter” post?

[WillAdams (William Adams (Carbide 3D))]

1. I use a #201 for most largish pocketing work — been looking into an 8mm tool, since a 4-flute w/ rounded edges I have has worked out well.
2. It shows adding geometry and cutting as a pocket, same as the others do.

[Saki (Ikas)]

So if I’m doing a finishing cut on the inside perimeter of a square, would I be doing a inside contour -or- a pocket cut that’s a square channel (wider than the bit itself) like a thin picture frame shape?

[WillAdams (William Adams (Carbide 3D))]

In Carbide Create you would need two geometries and two toolpaths:

• a smaller/inset geometry to cut the pocket, leaving the roughing clearance
• the actual size geometry to assign an Inside Contour Toolpath