Leveling Bit...

[brian_h]

I'm on the phone with my bit supplier and I said I needed a flat bottom bit to level my table. I remember somewhere someone used a 2" bit so they could cut time and see imperfections with the alignment of the z axis. She said, OK, what kind of 2" bit? 2-flute, or straight, or what? I didn't know. I figure price would determine the choice, but since the forum is right here next to the phone, what should I choose? I tried a quick search, but it didn't give me a "quick" answer.

Exactly what kind of bit would you recommend for surfacing?

[brian_h]

OK, I've learned quite a bit today (pun intended). There is a "spoilboard surface cutter". Who knew. I have a choice to make so I thought I'd pass it by you folks.

These are a bit pricey. They seem to have replaceable blades, which are sold for much less.

2 1/2" cutting dia., 1/2" shank, 2 wing......$223.08
4" cutting dia., 3/4" shank, 2 wing..........$226.92
4" cutting dia., 3/4" shank, 3 wing..........$250.00

10-pack of replacement blades, $19.70

I'd rather spend the $$ for production bits, so if you have some tidbit of information about what you did, I'd love to hear.

[patricktoomey]

Wow, a 4" bit would surface a board in a big hurry! I use a 2" 2 cutter bit for surfacing but I would be happy to move up to 4" to speed things up. The extra money would be well worth it to not loose so much time surfacing your table. Also, surfacing bits should last a long time as it's not much stress on them to cut thin passes on MDF (I'm assuming that's what your spoilboard is). My only fear at 4" would be that your Z axis had better be SUPER plumb or you'll notice ridges where the passes overlap. I have never had trouble with the 2" bit and see no reason that a 4" wouldn't work, maybe someone else here has used one that big and could comment on it.

[drodda]

The shopbot starter bit set had a 1.25" planing bit to surface your table included in it and it only runs $195.00 for the whole set. I use this bit every time I surface my table.


Dave

[brian_h]

So the question is, would it be better to use a 4" bit to try to achieve a super-plumb Z, or is that such a difficult feat that it would be better to save the frustration. Any thoughts?

[kerrazy]

do you have arouter or spindle?

[brian_h]

3HP Colombo spindle.

[myxpykalix]

here is a bottom cleaning bit 2" for 35.00. I use these on my legacy from magnate.net
http://magnate.net/index.cfm?event=showProductGroup&theID=136
I don't think i could justify 200.+ for any bit!

[john_david]

using a 4" surface bit is a good way to see if your "Z" axis is square to the table



JD

[dhunt]

I recall someone issuing what sounded like fairly dire warnings
re. using seriously-large-dia. bits (over 2 ins. dia.)
for safety reasons!

Like... considering just how much metal mass you have spinning
at around 15-20,000 rpm!

Think about it..the outer portion of a 4in. dia bit
are moving at several hundred miles and hour(?)
- or it seems like it.

If/when anything fractures, or comes loose...

[brian_h]

Anyone else want to comment about Jack's bit??? I think that seems pretty darn good, unless there's something I'm missing. *Am* I missing something???

[patricktoomey]

I wouldn't worry about the RPM's since you're running a spindle. At 4" you can run at a pretty low RPM since the edge speed of the cutter will still be high enough to cut well. I run my 2" bit at 9K RPM. Unless you're running a really high feed rate I don't think you'd have to run the 4" bit higher than 8-10K RPM.

For the squareness to the table, I would say go for it. I got my 2" so that there is no mark at all, I'm sure a 4" can be done too it may just take a little time. But once you do it all your cuts will be better.

The only real reason to spend the extra money for the larger bit is to save time while surfacing the table. In my case any downtime is very expensive and I surface my top probably once a week. If I could gain 15 minutes per week by cutting my surfacing time in half, the bit would pay for itself in a month or two which would be worth it for me. Many other people don't surface their tops that often and maybe have more downtime in which case it probably wouldn't be worth it for them. I think Jack's bit looks fine if you don't mind the extra surfacing time.

[gerald_d]

Do not take the comment about the speed lightly.

Bigger is not better. A 4" does not make your table any flatter than a 2" bit. And it doesn't do it any quicker when you have to turn the speed down by half. (at half speed, your router/spindle puts out half HP - at best)

Sure, a 4" bit will show an out-of-plumb spindle/router better than a 2" bit, but a trammel does a far better and safer job of showing you out-of-plumb.

(Why do companies then sell 4" bits? They are for people whose routers/spindles cannot get to the high speeds that we talk about. Also check if that 4" bit will fit in your collet - it is probably too big, because it is meant for a slower, higher torque head. Some big bits are meant as "planers" to be used in slow drill-presses)

[gerald_d]

Here is an extract from Onsrud's catalogue:


6875

Remember that Onsrud supplies premium quality - do not extrapolate their speeds onto other brands. They also have a safety note relating the max runout (wobble) that is allowed for the collet - reduce speeds if you have a suspicious collet, or dubious router.

[patricktoomey]

If you have an Alpha I guess that would mean you would have to slow down your feed rate. I can't get more than 5 or 6 ips out of my PRT so I should be able to run the 4" at my max speed and clear my table about twice as fast as with the 2", unless I'm missing something which is entirely possible.

[gerald_d]

Patrick, can you get a 3/4" shank into your collet, and have you got enough spindle horsepower to "mow" that wide? (Or do you want to do 2 very shallow passes?) Could be like eating your supper with a garden fork.

[patricktoomey]

Gerald, I like to eat with pitchforks, more manly that way ;-) I have a 5hp spindle and usually I just take maybe .050 off when surfacing so I think that would work. One crucial part I missed however was the 3/4" shank, I think the biggest one I could get is 5/8" (ER-25). I could probably get an adapter that hangs out and gives a bigger collet size but that would be suicidal with that big a bit hanging off the bottom of it. I once hung a 3" Corian bowl bit too far out the bottom of a hand router and lost it during a cut, not pretty at all. So it looks like I'm sticking with my 2" bit or maybe I'll upgrade to 2 1/2 to squeeze a little more speed out of the job.

[wcsg]

I bought a 1-1/2" planer for about $35 from rockler wood workers too. Works good

[brian_h]

Update: I went with the 2-1/2" because of the 1/2" shaft. $223.

[brian_h]

And here's what the bit looks like. Notice that when the blade dulls, you loosen the allen screw and turn the square blade to get a fresh edge. The initial investment is high, $223, but the replacement blades are super cheap, and you get 4 edges for each blade. It says max rpm is 14,500.


6876

[patricktoomey]

Brian, did you try it yet? I'd like to here how you like it. Also, what brand and model is it?

[brian_h]

Haven't tried it yet and may not for another week. Making money keeps getting in the way.

The bit comes from Carolina Specialty Tools, p/n CST252ST. I purchase through a distributor, BERNIE CHURILLA MARKETING, INC. in Minneapolis. So far I've been very happy with price and service.

BERNIE CHURILLA MARKETING, INC.
763-785-2222

[brian_h]

OK, I found some time to level the table. Here is the result "out of the box". I thought the bit worked great. 12,000 rpm. I just took off 1/8, just so I didn't have to mess around finding the low spot of the table. I know where the low spot is now. I bumped up the contrast and sharpened the picture a little to get the lines to show better. Remember the lines are about 2-1/2" apart.


6877

[paco]

If it's smooth to the touch, don't mind the visual.

[brian_h]

This area is the worst part. These are along the X axis travel, where Y is less than 24". The worst line is in the middle of the picture. It's a little more than 2 pieces of paper deep. All other areas have lines that are less defined. I'm probably not going to mess with the attempt for perfection yet. I'd probably make it worse. Let's see if it's an issue. I still have quite a learning curve to tackle with Rhino and Millwizard.