Lateral Force?

[shilala]

Is there somewhere a chart that relates lateral force and our bit/speed/feed?
Maybe some sort of calculator?

What I'm thinking is "what is the lateral force generated on the material when I'm running a 1/4" bit 1/4" deep at 3.0ips, 12000rpm in cherry, expressed in psi?"
Or something on that order?

I just thought it'd be useful to calculate how much carpet tape I needed to use, (saving waste and time cleaning the goo off the project) or if I had a vacuum table, how agressive I could be with my tooling without having to worry about crashing.
I understand there's a brazillion variables (like shear force of carpet tape, hardness, size and weight of material, etc.) and I'm not remotely capable of mathing that hard, but it'd be a handy thing to use, at least until I got a feel for things. It wouldn't even need to be super accurate, just an "all things being the same" representation for basic guidance.
From chipload calculations, I've found that my guesses are sometimes wildly incorrect. That's not often anymore, but it's the calculator that taught me.

I avoid tape like the plague and screw most everything down, but this is one of the big reasons I avoid tape, and I waste a fair amount of material in some instances because of it.

[myxpykalix]

Scott,
I think the variable combinations of materials, bit sizes, feeds, speeds and other things are enough to make your hair hurt trying to figure out something like that.
If i were you i would invest in making yourself some nice holddown jigs and forget all that other stuff. I started out when i made my table plumbing it for vacumn holddown with 2 feins and got so i just didn't trust the vacumn. Mainly i didn't want to run the 2 feins for 6-8 hours for a 3d file.

I made a simple jig (can't find pics) of a piece of mdf with a 90 degree corner. I just butt my material up to the corner and screw down a small piece of mdf for a holddown and clamp the jig to the table. Simple easy not worries about tape.
Some guys have t tracks embedded to use T nut holddowns. Jigs will make your life easier then what you are thinking of doing.

[garyc]

Scott....
There is an Android app that calcs just that. CNC Force Calculator. Free

[shilala]

Thanks, Gary!!!
I'll hunt it up, hopefully it's available for iphone. If not, it's probably available for Chrome.

Jack, I'll be making a couple jig setups for my table. I screw most things down, anyways.
When I learn stuff, and it doesn't matter what it is, I absolutely have to learn everything. It comes from being a mechanic all my life. I need to know how everything works, no matter what it is, and I have to know it inside out.
By studying and knowing the forces involved, it'll give me a better feel for my machine, just like "feeling" a motorcycle or car under my ass. Whether I use the information practically or not, it'll help in ways that I'm not even able to see just yet.
It'll certainly help me to understand the stresses I'm putting on my bearings, bits, motors, etc. In turn, that'll help my machine last longer. I'll intuitively run it within it's limits.
I've been uncomfortable from day one because I can't "feel" my machine and worry about how I'm treating her. This will go a long way toward fixing that. :)

That was the esence of why I wanted the calculator, but the holddown parameters where what made me think of it, so I mentioned a couple practical applications.
Who doesn't want to save carpet tape, right? lol

[curtiss]

Put your cherry board on the table on top of some wax paper. While your bit makes the cut. Measure the force exerted with some sort of small fish scale attached to wood.

[Brian Harnett]

Well your ears will tell you a lot, especially if you are going too fast, the scream just before it all gets quiet after the bit snaps off.

[Brady Watson]

Been there...done this. These types of calculators are practically useless. I don't say that to poo-poo the science behind it, but more to bring up the fact that there is no feasible way to account for all the variables involved in getting meaningful numbers.

None adequately account for upward lift against the part due to the helix of the tool (what angle helix?) in literally hundreds of materials. These calculators are very general. Also, lateral force is practically meaningless if you stay in the ballpark of recommended chipload. It's the effect of part lifting, not shifting that is the issue, especially if you have a vacuum system. Even the smallest amount of vacuum will yield TONS of lateral force & slide resistance - but lift the part just a few thousanths, and it's out of registration.

Thinking about this is good (so kudos for that), especially if you visualize things like backlash getting taken up under load and the like.

If I could offer a suggestion, it would be to get some type of homogenous material like MDF etc on your spoilboard and flatten it with the CNC. Plywood is **** for your spoilboard. It will shoot you in the foot over and over and over again, since it will NEVER be flat.

-B

[myxpykalix]

Well Scott..."Knowledge is power, and experience is....well, experience!":D

What i mean is that you will understand more if you use your EARS and EYES to tell you what works and what doesn't when you watch your feeds and speeds and get "tuned in" to what it sounds right when cutting.

[shilala]

Well Scott..."Knowledge is power, and experience is....well, experience!":D

What i mean is that you will understand more if you use your EARS and EYES to tell you what works and what doesn't when you watch your feeds and speeds and get "tuned in" to what it sounds right when cutting.
I got ya, Jack.
I listen really good. That's how I stopped griping about breaking bits. :D
Chip load calculations helped a lot, too. And I pay very close attention to make sure my bits don't get hot. You guys straightened me out there a long time ago, Thank God. It was getting expensive!!! :)

[GeneMpls]

(saving waste and time cleaning the goo off the project)

The cure to this problem is application tape as used in sign shops- apply
the tape to the substrate and the spoil board... and the two side tape
to the tape = easy cleanup. Learned from Prof Joe Crumley.