Cutting a spoil board

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Cutting a spoil board

Postby edowney » Mon Oct 01, 2018 11:51 pm

This may sound crazy but I use vcarve to design my spoil boards. My boards are also act as jigs to hold the material I'm cutting in place. In the past I've used end mill bits to create 3/4" round 1/2" deep holes followed by 1/4" holes in the center of that cutting all the way through the MDF spoil board. It's been really hit or miss for reason using this process. From time to time my CNC Shark forgets where it is and loses its accuracy which is why I use it to make my spoil boards. I just bought a CNC Shark II and need to make a spoil board for it so I've decided I wanted to use forstner bits to do the drilling this time - just seems faster. The problem I'm having is that I can't find tool definition files for my new Freud 3/4" and 1/4" bits so I can redesign my vcarve spoil board. Any suggestions? Thanks!
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Re: Cutting a spoil board

Postby IslaWW » Tue Oct 02, 2018 12:02 am

Are you planning to chuck them up in the spindle? What is the operating range for the Forstner bits? Will your spindle turn slow enough to operate them properly? Is your machine rigid enough to handle a bit that diameter?

In any case, should you decide to go a head, simply enter the Forstner bits as an end mill of the proper diameter.
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Re: Cutting a spoil board

Postby martin54 » Tue Oct 02, 2018 12:31 am

I don't know anything about the shark machine or control software but doesn't it have homing switches so the machine can be homed to a machine zero which will in effect re zero the machine to a particular part of the table so it knows exactly where the table is again? Bottom left corner is where the control software I have used homes the machine. Once homed any loss of steps that may have occurred at some point will be corrected :lol: :lol: :lol:
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Re: Cutting a spoil board

Postby edowney » Tue Oct 02, 2018 12:47 am

First thanks everyone for the quick replies - that's awesome! My original CNC Shark is running with a Dewalt DWP611 compact router. I have a touch plate attached to it so I can zero it out against the spoil board which is great. When I make my spoil board on the old shark it takes around 40 mins. It has to cut 17 3/4" holes evenly spaced around the board and the 17 1/4" holes centered in the 3/4" holes. For some reason I've noticed that after it cuts several holes it, on occasion, it doesn't cut a whole where I would expect it to. Usually when it get's into the 1/4" holes. And it also takes forever. So now with the new CNC Shark II which is a beast compared to the old shark I'm running a Bosch 1617 which came with a 1/2" collet. I thought this would be a good time to look into using a 3/4" forstner bit to just do a plunge into the board and make the wholes - sounds a lot faster to me. So I bought a Freud 3/4" forstner bit and 1/4" forstner bit and a 3/8" collet for the larger bit and a 1/4" collet for the smaller bit.

Thanks for the suggestion IslaWW I was kinda thinking about doing something like that since I didn't see forstner bits listed but I did see that you could import tool definition files so I thought maybe that was an option I should be looking into.
't
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Re: Cutting a spoil board

Postby tomgardiner » Tue Oct 02, 2018 12:48 am

I would define the forstner bit as a drill and give it a 180 degree tip angle (I may be off about tip definition). You will always be using the bit as a drill so don't risk confusion by defining it as an end mill.
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Re: Cutting a spoil board

Postby ger21 » Tue Oct 02, 2018 1:33 am

At router speeds, your 3/4" forstner bit will dull almost immediately, and will probably start a fire, or stall the router.
It also won't be balanced, and may have a LOT of vibration.

A 3/4" forstner bit should be run between 250 and 1200rpm, depending on material.
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Re: Cutting a spoil board

Postby dealguy11 » Tue Oct 02, 2018 5:14 pm

I agree with Gerry on this. A router runs way too fast for a forstner bit, or for most drill bits for that matter. Learned this the hard way very early in my CNC career cutting holes in a spoilboard like you're doing. Good thing I had a fire extinguisher handy.
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