How to mill a guard slot .............

[Karl B. Andersen]

Not sure what your question is, Nick.
Each successive plunge was slightly deeper than the one preceding it, until full depth is attained.
Then work backwards to eliminate the stair-steps.
We're just clearing a center path to begin stock removal of the width.
Most of the people on this forum either do not even own a mill, or might have a bench top mill.
This makes it easy on the tooling and the equipment and minimizes breakage to almost zero, which is a challenge in lower grade equipment.
If you are "...curious what the reason behind it is." I will say that it's because it works and saves time and results in a slot that FITS virtually every time with little deviation.
Take it for what it's worth, or don't take it at all, but I will repeat that Jerry Rados taught me this and Jerry had forgot more about knife making than most people I know will ever learn.
And he taught me on a Bridgeport. With a DRO. But he still did the stair-step and used a dial indicator.
That method eliminates just about everything that can go wrong.
It's stupid simple.
And I do really good with stupid simple.

I'm not talking about cutting full depth in one pass. He made his cuts by plunge cutting a little and traveling in the X-axis a little, and then did that progressively across the slot. I've never seen it done that way, so I'm curious what the reason behind it is.

 

[butcher_block]

i think the steps would keep the mill from mayeb walking of a bit in a sloppy tool (im with you tho nick plung a bit and then traverse then plunge a few tho more and tak full length cuts )

 

[Karl B. Andersen]

Probably ends up being about the same amount of time. Lots more back and forth, however.
My method only goes one way in each direction.
Either way, the idea is "baby steps". Don't push the end mill more than it can handle.
I did this post in response to a thread about breaking end mills.
Small bites is the solution.

i think the steps would keep the mill from mayeb walking of a bit in a sloppy tool (im with you tho nick plung a bit and then traverse then plunge a few tho more and tak full length cuts )

 

[Brett Mathews]

The more I think about this method the more it makes since to me. I will give it a try some time.

 

[Salem Straub]

I like the method and the pics are good, too. I'm a bit hung up on the stair step approach too, though. Just so I understand- you are starting with a light plunge, traveling x-axis about .040, taking another light plunge, x travel again about .040, and so forth, all in the same direction until the other side is reached? So that, when reaching the other side, you've incrementally plunged the full depth of your cut?

It seems as if by the end of the slot, in both directions, you are taking a much heavier side cut than when you started. If this is the case, are you feeding slower in the x-axis by the end of the cut, so as not to deflect or break the cutter?

Taking full length light cuts back and forth would not do this- a lot more table cranking, yes, but seemingly a more even cutter load throughout. It's what I've been doing, and while I wish mightily for x-power feed all the while, it makes sense to me and works. Actually, I locate and drill a hole at each end first- I figure a drill bit removes material faster than a milling cutter, nice to have the slot ends but not the web drilled for location without a truly interrupted cut.

Not trying to be a smart aleck or anything, just trying to understand. Thanks for teaching, Karl.

 

[Karl B. Andersen]

You're not being a smart aleck at all.

I like the method and the pics are good, too. I'm a bit hung up on the stair step approach too, though. Just so I understand- you are starting with a light plunge, traveling x-axis about .040, taking another light plunge, x travel again about .040, and so forth, all in the same direction until the other side is reached? So that, when reaching the other side, you've incrementally plunged the full depth of your cut?

Correct.

It seems as if by the end of the slot, in both directions, you are taking a much heavier side cut than when you started. If this is the case, are you feeding slower in the x-axis by the end of the cut, so as not to deflect or break the cutter?

This is where my thinking differs. I am, in fact, NOT! taking heavier sides cuts than when I started. In fact, I'm taking NO sides cuts at all! All cuts are straight DOWN with no lateral side pressure on the end mill. This greatly minimizes the risk of end mill breakage.
I might be a little easier on my downward pressure to get to my depth of cut as I go deeper and deeper, but my speeds remain the same.

Taking full length light cuts back and forth would not do this- a lot more table cranking, yes, but seemingly a more even cutter load throughout. It's what I've been doing, and while I wish mightily for x-power feed all the while, it makes sense to me and works. Actually, I locate and drill a hole at each end first- I figure a drill bit removes material faster than a milling cutter, nice to have the slot ends but not the web drilled for location without a truly interrupted cut.

I'm utterly against any type of hole drilling during the process. Interrupted cuts are hell on carbide.

Not trying to be a smart aleck or anything, just trying to understand. Thanks for teaching, Karl.

Don't worry about being a smart aleck - you're in good company.

My end mill breakage is next to zero.
My guards almost fit themselves.
It doesn't take a rocket scientist to follow my procedure.
I share this to help others who are having problems. They can hopefully gain something from my dozen or more years of using this process.

Those who are not having any difficulties with their methods should feel free to continue using them.

I didn't post this up for controversy or challenge or defense of my methods.

Someone had a problem and I tried to help.
Since posting this my email box is loading up with questions and my phone doesn't stop ringing with words of thanks.
So I would say I did, indeed, help those who were in need of some solution to difficulties they were having.

 

[crimsonfalcon07]

Thanks for the tutorial. I don't have enough room in my "shop" right now for any more large tools, but when I get a larger space, a mill will be on my list. I've added this to my bookmarks.

 

[Salem Straub]

I see, it seems that you are doing a series of plunge cuts only. Lifting the cutter to travel in X, then plunging again. If you are doing that, I can see why you'd be stepping down.
Thanks for the further explanation.

 

[Karl B. Andersen]

Certainly. Keeping in mind that's only to create the center slot from which to being the lateral milling to achieve the target width.
I often see the BEGINNING of the process as that step which seems to cause so much grief. (and broken end mills!)
This avoids that issue.

I see, it seems that you are doing a series of plunge cuts only. Lifting the cutter to travel in X, then plunging again. If you are doing that, I can see why you'd be stepping down.
Thanks for the further explanation.