Cutting mdf 1/4 up cut bit ( sb kit) problems

[ArtFilmgroup]

I don't have a vacuum hold down system, i am using a bit up cut to cut 1/4 mdf but the power its lifting the material while its cutting, i am using screws to hold it but in some parts it lifting

please i need a help to those have more experience for bit to use and rpm

thanks shopbot friends

[Kyle Stapleton]

Stop using an up cut and use the down cut it will push or mdf into the table.

Also you need tell more about what you are doing (bot you have, bits you are using, feeds, speeds, sizes and shapes you are cutting, ect) if you want better info.

[919RickR]

Kid
A straight or a shear bit will work also.
Rick

[bleeth]

The 1/4" upcut bit in the SB kit, I believe, is for cutting plastic and/or aluminum. A straight upcut bit is not used for wood product panels much.

For 1/4" MDF you should use a downcutter. Your parts still may "jump" a little when they come loose. You can prevent that by using bridges in your toolpath and cut the bridges away by hand afterwards.

[ArtFilmgroup]

thanks

i use this material

Mdf 1/4,1/2,3/4
plywood
formicas
composites
and plexy max 1/2

the speed 12.000

and only i have its the kit from shopbot but i find problems cutting,i will really appreciate if you have a diagram of bit and speed you can send me

thanks so much

[gundog]

I think you might need a better grasp on machining. I believe the bits you have are from Onsrud go to their web site with the bit numbers look up the recommended chip load for your bits. Then using a chip load calculator or these formulas calculate your speeds and feeds don't just guess. Smaller diameter bits generally have smaller chip loads. The proper size chip when cutting is the key the chip takes the heat away from the bit. If the chip is too small it builds heat real fast if the chip is too big you can break the bit.

FORMULAS: Chip Load = Feed Rate / (RPM x # of cutting edges)
Feed Rate = RPM x # of cutting edges x chip load
Speed (RPM) = Feed Rate / (# of cutting edges x chip load)

[hh_woodworking]

Here is a great thread on bits and there looks. A ton of great work and research done in the PDF attachment : http://www.talkshopbot.com/forum/sho...eated-document

[ArtFilmgroup]

thanks a lot for your help i will get in to this with more careful.

[gundog]

I have re-read my response and I don't like the way it came out. What I meant to say is you need to look at this in a logical approach start with the specific material you want to machine, then pick the best bit for that job by going to the manufacturers web site use your bit numbers to see which one is likely to be suited for cutting said material. Look at the recommended chip load for that bit. Also look at your hold down method and the size of the part being cut. Try and stay within that chip load recommendation they usually give you a range for example .004"-.006" then play with that start conservative and work up to get your best results. It is important to be able to figure out your own speeds and feeds either with a calculator or by using the formulas. Listen to the sound the bit is making as it cuts and the finish quality of the cut. If things are going good you will hear it and see it in the cut quality the chips coming off should be warm to hot and the bit should be relatively cool enough to touch but don't if the bit is sharp it will cut you. Use a non contact thermometer you can buy them pretty cheap these days.

If someone were able to just make you a chart for your bits you would not learn what you need to know to use this machine. It is better to teach someone to fish rather than just giving them fish.

Mike