Bit to cut through plywood

[bob_reda]

I've searched the archives as I'm sure this question has been asked before. What type of bit does one use to cut through plywood without all the splinters?

Thanks
Bob

[hines]

I was using cheap steel bits and was getting lots of splinters. Once I bought a carbide spiral downcut bit it worked flawless with no splinters.

[harryball]

Use carbide tipped and/or solid carbide bits only. I find hss bits are a false economy, they never last long enough to even finish the job most of the time. Cheap carbide bits are better than hss, but I try to avoid those as well.

Solid carbide spiral bits. Downcut = clean top cuts and the chips will compress holding the vacuum. I use them on up to 1/2" ply in a single pass, 3/4" ply for 2 passes.

Upcut I've just not used much on sheet goods, I use them mainly on solid woods. I've never had much success with upcuts getting clean edges. I've tried coventional and climb and various speed combinations and the upper edge is always tattered even with the new Onsrud bit I just got.

Compression bits do both up and down cuts and are supposed to do well for single pass work. They are expensive and I've not tried one yet.

I find a straight flute cutter is good for pocketing and some cutting jobs. I use them on MDF a lot and it leaves the sides smoother than the spirals. Often I use them on MDF just because it's already loaded to pocket face details on a sign... I just let it cut out the shape and keep going.

I'm still a newbie myself, I'd be interested if anyone else would share their preferences or disagree with mine.

Robert

[paul60]

hi r.ball about the downcut spiral, do u have a problem with the chip removal?
i have never tried a downcut spiral just upcut
the upcut clear the chips by pulling them up
just courious about downcut spiral
thanks paul

[richards]

Because of my limited vacuum, I've stopped trying to cut entirely through sheet material, which also means that I've stopped using compression cutters. Instead, I prefer to leave a 0.030 to 0.050 inch skin on the material to preserve vacuum.

I just finished a run of particle-board shelving units this morning using both upcut and downcut spirals. I started with the upcut, which I had been using to cut plastic yesterday. It worked fine, but there was some tear-out, which I expected. No damage done, since the job was not at all critical.

Then, I switched to a downcut spiral. (Both cutters were made by the same manufacturer and purchased through AA-Carbide, here in Salt Lake City.) The downcut was vastly superior in cut quality - even in particle board. (Normally I save the downcut spirals for cutting melamine and plywood.)

Except for MDF, I haven't had any trouble with the chips packing in the kerf. With MDF I usually grab a flat screwdriver as a 'cleanout tool' to slide along the cut before trying to vacuum up the chips. Even then, those chips are really packed in.

Melamine is a special case in my shop. Again, because of my limited vacuum, I use a downcut spiral and leave a 0.030 to 0.050 inch skin on the material. Next, I use a laminate trimmer with a 3/16-inch cutter and a template guide to center the cutter down the center of the kerf to cut the pieces apart. Finally, on the router table, I use a downcut spiral cutter with bearing to trim the bottom edge of the melamine. That method produces chip-free parts (as long as I don't use dull cutters).

[harryball]

If I don't try to take more than 1/2" in a pass the down spiral does ok, on MDF, however, I make 1 pass even on 3/4 and it does ok. The next pass around tends to clean the previous chips out with my dust collection going despite the fact the spiral is downward.

Except for solid wood, I rarely use up cuts at all.

Robert

[oddcoach]

I use a 1/4 compression bit from onsrud 60-111
I cut all the way thru 3/4 in cabinet plywood all the time with good results. i have a prt and cut at 2.5 in/sec with a spindle or 1.75 in/sec with a router

[jhicks]

We have been very happy with Onsrud 3/8" compression bit on 7 and 13 ply 3/4" thick as well as prefinished maple and birch ply stock. we hold it with a simple vacuum system being run on 6.5 hp Rigid $99.00 vacuums ( 2 for the entire 5x10 table)
Single pass with a ramp in and full depth cut through to .770" at 160 IPM at 16,000 rpm on a 5HP spindle and Ascension control box.
Works great

[jamesgilliam]

Solid carbide is the way to go for cutting plywood. I cut alot of 1/2" (12mm) Baltic Birch in one pass, usually at 1.5 IPS @ 10,000rpm. I am using 1/4" four flute end mills with a 7/8" cutter length that are normally used for metal cutting and getting good finished edges and tool life from them. They normally cost me about $8 each. Normal life for one is about sixteen hours before I start getting some tear out on the edges, and then it is minimal to the finish of the product. On 18mm I take it in two passes, first around .500 deep and then the cut out pass with no problem. James

[paul60]

hi James & Jo-Ann
what is the name of the bits and part number you use.
where do you purchase these from.
thanks paul

[elcruisr]

Onsrud 60-121 3/8" single flute compression spiral with short upcut. Turning 18,000 rpms on a 5 hp spindle at 8 to 10 IPS. Good clean cuts. Over 100,000 parts this way!

[jamesgilliam]

Paul, I got the end mills through Rutland Tools in Houston. The part number is 9000-4428 on the last bunch I bought. Usually I just go in and see what they have on the shelf and get the cheapest ones they have. James