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How many passes..........

3010 Views 6 Replies 6 Participants Last post by  Putzger
I am curious to know if someone has a reference table as to how many passes should be done when ,let's say for an example, a spiral or straight-cutting bit is used to make a desired slot.Of course this depends on the thickness of material and its density or type( Hardwood as opposed to softwoods).My owner's manual does tell me what speeds to use according to pliability of woods being cut,but not if it can be completed in 1 pass.Any ideas..................
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Well I have heard not to make a pass that is any deeper than half the diametre of the bit you are using. I use it as a general rule of thumb and it seems to work. However, it does worry me that if I chuck up a 12mm straight flute and try to take off 6mm in one pass that it is too much. In this case I only take off 3mm at most. So I guess what I am saying is 3mm cut maximum. (ALthough the last cut I make is a very light one to clean it up).

Hope this is not too confusing.
Whilst I agree with Aaron.
The depth of cut will vary with the type of material being cut (hard or soft) and I suppose we should take into consideration the sharpness of the cutter. But always leave that Imm for the final cut as Aaron suggested.
I have found if not sure start with shallow passes and get the feel for the material/bit and how they are reacting together. Then adjust accordingly.
Thanks,basically what I thought,but always appreciative from other input.
Although many will use different depths of cut, I find it's something you get used to depending on the material.
You would make a shallower cut in a hardwood than you would on a softwood.
I like to use a bit of waste wood to try a few cuts on before going to the workpiece.
That way I can get the feel of the wood first.
I spent all my working life in a toolroom mainly using a vertical mill which is like a huge overhead router.
When you are cutting 5% chrome steel you soon learn to get the feel of the material you are cutting or the cutters will overheat and break.
ejant said:
I have found if not sure start with shallow passes and get the feel for the material/bit and how they are reacting together. Then adjust accordingly.
That's dead-on advise :sold:

As an example of it, I was cutting a 28" long slot through a piece of finished 3/4" particle board today (It's the adjustable pivot point slot for a band saw circle cutting jig).

The first plunge cut with a 1/4" spiral up-cut bit seemed to go rather quickly so I tentatively began a full-depth route. I went quite slowly, but it just didn't seem "quite right". :eek:

I changed over to making an 1/8th- deep pass and WOW! The bit bore across that material as if there were no tomorrow. So shallow cuts it was. :p

I think I was finished and cleaned up after making several passes in less time than it would have taken me to make a single dep pass. (And I'm sure the router bit liked the several-passes way of doing it better as well :) )

So yeah, playing it by the feel of the material is the only realistic way to go. Some stuff just cuts faster and cleaner than other stuff -- but you aren't going to know 'til you get into it :eek:
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