What's this Carbide coating.

[Boyan Silyavski]

Thats definetely non stick teflon coating, similar to Freud .

Now i i don't have something clear. Why use burs instead of some ultra sharp sharp micro grain carbide router bit, say 3 flute straight long reach?

I don't see how you will route faster with these compared to normal router bit. Also if you insist on burrr just buy roughing bits.

What size bit, depth of cut, speed and step over? lets do the calc here. cause i dont see it right using these bits on foam.

[njhussey]

there's these ones from France....http://www.hand-stitched-rasp-riffle...tre-25-mm.html

Or this, I know it's only a ball but it's 30mm diameter? http://www.clasohlson.com/uk/Rotary-Rasp/30-9512

[charlieuk]

The burr style is a prity standard practice when working on surfboards. From experience I have had in the past normal fluted bits can tend to heat up after a long duration and coolant is not a option and on eps this can end up melting the foam which can make a right mess. The burrs also give a great surface Finnish.

im open to ideas ?

I played with the two burrs I have today and even the fine one seams good.

No idea how hard or I fit would be posable but would it be posable to make a blank bit on a lathe and then coat it in some sort of abrasive grit? I'm assuming balancing would be the major problem?

[Boyan Silyavski]

i would give you tons of ideas but you have to give me some data to work with

What size burr, depth of cut, speed and step over you use now? Do you pocket or slot cut? What is your collet size ? Spindle kw and rpm? What speeds your machine is capable of? What rails and ballscrew ?

[charlieuk]

The two burrs I have are 33mm cutting depth and 21dia 64mm overall The ideal would be something around 25mm dia 75-90 mm cutting depth 130mm over all
I have a 2.2kw water cooled huanyang spindle so er20 collet so 13mm max using hywin 20 rails x is on mod 1 rack geared 3.2-1 rapid is set at 10,000 mm/min but capable of a lot more but to scared to set higher at the moment. y and z are 1610 ball screw set at 2500mm min and it is quite happy cutting at 2500mm/min. When cutting a surfboard it is basically just running up and down the length with very small y and z movements most of the time

[Boyan Silyavski]

I remember somebody using plan drill bits for the purpose. A good bit like Dormer is quite balanced. Leave, flatten or ball nose the face. But a proper reamer I belive is what will do the job.
As you can see bellow more or less the special foam cutters look similar.
http://www.3dcutting.com/solutions/frogtools.html

so why not just buy proper foam cutter or try some of what I suggest for a diy solution

Look at this baby
http://www.ballewsawandtool.com/inde...hk=1&Itemid=31

[charlieuk]

The frog tools are pretty expensive at nearly $300 dollars befor shipping and tax and the other is only a max of 1/2" dia so a little on the small side ideally but maybe a possibility if I can't find anything else

many thanks

[gavztheouch]

How big is your max size collet on the spindle?

[gavztheouch]

http://www.mycncuk.com/threads/6770-...r-milling-foam

Here is a thread I started when I was looking for a simlier tool. I also looked into the frog tools but the cost was too high when I was unsure if I even had the ability to mill the foam parts I needed. After completing the job I would say that the vast amount of running time is actually in the final finishing passes and the rough cuts take very little time in comparision. I don't know what sort of finish and step over res you are going to use but I would suggest starting out with some cheap tools to get a feel for what you need to complete the job in an acceptable time.

I bought some cheap indexable insert mills and also some pricey ballnosed mills but half way through the job I relised I could use the endmill to 3d profile and rough the part so the ballmill became redundant. Condsidering the ball mill was twice the price of the endmill it was a costly mistake.

I also think you spindle and machine may not be man enough to take a large frog tool but I could be wrong. I just know even on my thermwood the larger tools cause a hell of a lot of vibration due to off balance tools and jerky machine movement. Burrs dont look like the most balanced tools available with all that carbide glued onto a blank at random angles.

[charlieuk]

Cheers many thanks I took a look at the thread. The burrs I have seam pretty well balanced there's certainly no noticeable vibrations and cut well at around 6-7000rpm I think the way to start is going to be getting a collet extender which luckily come in er 20 1/2" and relatively cheap and will allow me to use the burrs I have all be it having to do a few more passes and get me going then try a few other cheaper bits and and hopefully in the mean time save up for something a bit more specific when I know what works best.