Challenges Cutting Hardwood - cutting moves panel with vacuum

[kenakabrowncom]

I just got my BT-32 up and running and after some great onsite training here in Dallas by Grant we are now dealing with trying to get the machine and our product to cooperate.

I have the Bt-32 Alpha with the 2.2 spindle

99% of the cutting we will be doing is into glued panels that have a comination of hard woods. Typical thickness if 3/4 to 7/8.

I have setup the machine with a "Brady Vac" hold down using the Fein for the vacuum.

We started yesterday trying to cut a panel of mostly Red Oat at 1.5 IPS and 1/4 per pass and found that the cutting ended up moving the board.

I was using a 1/4" downcut sprial (Onsrud 52-910)

I changed the pass to .125 and found the same problem. I next decreased to .7 IPS and .125 and that worked but the finish on the edge is very rough....

Any thoughts from you experts? Wrong bit?

Ken

[knight_toolworks]

sounds like our hold down does not suck (G) something is not working as it should I cut hardwoods at 1 or 1.5 ips using any size bit up to 1/2" and I take 1/2" passes. the downcut is usually the best bet.
so you need to figure out whats wrong with your hold down. is the wood flat?

[srwtlc]

You can loose a lot of vacuum right through the face grain of red oak. If your parts/blanks are all the same size, try a dedicated fixture that will focus more vacuum right under the blank and use some form of gasketing around the perimeter. Something like the "Brady Vac II".

Downcuts are good if you need the top edge chip free and they force the material down, but I feel that they can require more lateral force especially when you're not cutting all the way through. On subsequent passes, you can start recutting chips and cause heat build up which greatly reduces tool life.

[kenakabrowncom]

Thanks Steve and Scott... I am using a dedicated fixture... but I could open vacuum hole a bit more and get more suction. I had also not thought about the addition of the gasket.

Steve - thanks for the info on the speeds your doing...are you using vacuum hold down to get that much cut depth and speed?

[myxpykalix]

What type of spoilboard do you have? You will lose vacumn thru the sides of your spoilboard so I would suggest you take some silicone caulk and coat all 4 thin sides of your spoilboard to seal them from losing vacumn. That might help. you might also turn your vacumn on and at all your connection points take a match (the smoke from a blown out one) and see if you have any leaks.

[knight_toolworks]

I have done it with vacuum but most of the time the wood is clamped since I do a lot of one off things. solid wood can be a challenge to vacuum clamp depending on the wood.
so far in my tests I have found a downcut bit will cut hardwoods more accurately then any other bit when your using under 1/2" bits. once I went from a regular upcut a roughing upcut to a downcut in a 3/* size I got less bit defection then any other bit.
usually in 1/4 and up the chips don't jam much in the cut.

yellow glue is easier to seal with it dries really fast and seals in one coat.

[rcnewcomb]

Try putting some masking material on the bottom side of your material. I found that some oak leaks. We usually use gasket material and then use masking tape between sides of the wood and the spoil board.

[knight_toolworks]

or coat the back side with yellow glue. this works great but it is a bear to remove if you can only sand it.

[ljdm]

My 2 cents worth - when cutting oak, I use vac hold down, but if the wood is too smooth, I use cheap rolls of shelf liner, the rubberized mesh looking stuff, and if I dont want to cut the liner, I leave a thin skin. Easy to trim that skin when I'm done. It helps on smooth wood, and helps vac loss through the board itself. I can cut oak at least 2-2.5ips 1/4" per pass with 1/4" bit. Down spiral helps, just have to keep the kerf from clogging up.

[kenakabrowncom]

Some great suggestions! These comments and suggestions for this newbie is why I leaned towards ShopBot... you guys are great!

FYI... my spoil board/jig is expanded PVC. So there should not be any leakage there. I do need to use the match suggestion and check all of the joints.

Ken

[tkovacs]

I've used Lou's method with good success too.

[woodworx]

Throw another piece of material over your spoil board and pocket out the area (-.05) where your hardwood piece can fit into. This will really hold things tight. Otherwise just screw into your spoil board.