Cutting 4" thick stair treads

[3imoh]

Howdy folks-

I have a job coming up cutting 18 stair treads out of 4" thick fir for a spiral staircase. They are pie shaped with a small radius on one end and a large one on the other (5x2' overall size). The straight edges will already be cut for me, I just need to do the curves.

I have considered various methods including indexing with pins/flipping the part, and cutting 2 inches or so, trimming with a bandsaw and finishing with a bearing bit.

I have found a source of 5/8" spirals that are long enough to do this (6 inches OAL). I was thinking of doing 2 inches or so with a shorter bit, then cut the last couple with a ton of passes with the 6" bit. I would hope deflection would not be an issue with a 5/8" tool...not sure about other issues...I have never spun that much carbide that far away from a collet...

Has anyone tried doing anything like this? Seems like I may be at the limits of the machine/spindle on this one. I have a 4HP HSD, and this is on a long Z PRS.

thanks,
Howie

[dray]

That sounds like fun!

I would try a piece of the same lumber on the bot and see how it goes. Clear DF is pretty hard. i'm sure it will cut it but getting deep might heat up the bit?

[harryball]

Can you treat it like a 3D object and flip it after cutting 2" of one side, then cut 2" of the other leaving tabs to hold it in place? You could then easily cut it free and clean it up with a sander.

Robert

[3imoh]

I thought about that. At a suggestion of another botter, I was going to drill holes outside the part and put dowels in...this is a nice way to register parts for this sort of thing.

The only trick is that the machine has to be dead square. I have checked my machine the other day and the diagonals on a 5x10 foot rectangle are within 1/64" of each other...so it is pretty square, I guess ;-)

I may end up going this route, but I would love to not deal with indexing/flipping the part. Just wondering if anyone has done anything similar with a long 5/8" tool...

-Howie

[garyb]

Howie, pre cut on the bandsaw leaving .125 then throw it on the bot and cut with one pass

[srwtlc]

You could cut offset to the outside and step in a few thousandths with each pass to allow for some tool clearance as it progresses down. That is if the CEL is 4+".

[jhicks]

Not the ultimate in using the bot but I think I would make a template with the bot and hand route with the template as my guide.
Not as fancy or cool perhaps but I would guess the repeatability is perfect and you can run in a single/slow hand fed pass and be done.
Sometimes the time and energy to fixture and develop exactly the right methods are fun but not as efficient as an "old fashioned method"
Good luck no matter which route you choose.

[stevem]

I’m guessing that the small radius will be mounted against a pole and will not be visible once installed. The large radius can easily be cut from both sides and any water marks removed on a belt sander. If the parts are supplied with the straight edges cut with precision, the material would be easy to index (preferable with cut along the X axis) by screwing a template to the table and clamping the material from the sides with toggle clamps or using a vacuum fixture.

[3imoh]

Turns out the place I ordered the 5/8" tooling sent it ground and not 2nd day air. The guys I am cutting this for really needed to get one over to the client, so I went for it with 1/2" tooling, which a local supplier had.

I used a 4 1/2" OAL bit to get down to 3" taking 3/8 at a time, then I came in with the (super sketchy) 6" long spiral to finish off the last 1" doing .20 passes.

I was impressed with how the machine handled it...I was expecting vibration issues with that long of a tool, but so far it is working out well.

I was running 2"/sec at around 13000. Big chips coming off the fir. I probably could have taken deeper/faster passes, but I did not want to push it.

I imagine the 5/8" tooling would work even better, but I am going to try to finish out the job with what I have, and maybe hold on to the larger bits for future jobs.

The only issue I had was with the fir blowing out in big chunks every once in a while. Wide masking tape seemed to help on the edges and I changed the angle on the pocketing routine to be more in line with the grain. The wood is reclaimed Doug Fir, with some pretty bad checks in places...held my breath on a couple of those. I am cutting these upside down, so the upcut bit is leaving a great edge on the finish side.

Still have a few more of these to go but so far so good...hopefully posting this does not jinx me too bad...

I put a video up on youtube if anyone is interesed...it is of the 6" tool taking off the last bit:

http://www.youtube.com/watch?v=ly-wSPUNkPY



8693

8694

[fleinbach]

Howie,

Great video! You've done a splendid job and once again demonstrated the versatility the Shopbot is capable of. When presented with a problem you worked out a solution which I'm sure gives you a great feeling of satisfaction.

[paco]

Good work Howie! That's a hell of a piece! Hwo many of those did you say you'll be milling?!

I sometime climb the cut to avoid chipping of end grain...

The few project which involved very thick wood, I chosen to make the final cut with a flush trim bit (sometime as long as 2 inches).

If you ever get a chance to post details (pictures) of you dust collector swing arm, that would be cool. thanks in advance.

Bot on!

[propellers]

Howie, Are you using a 6" end mill or a wood cutting bit?

[3imoh]

I still have a way to go...on 6 of 18. I hope they get me the rest of the blanks tomorrow. It takes about 20 min of cutting with another 20 or so for setup/removal. BTW, this is my first job on the bot...hopefully the next one will be some nice small mdf squares or something :-)

I am using a standard end mill from the local industrial supply place...made by Gar Tool, I believe. It would be better if the CEL was longer as I am getting a little "burnishing" on the previous passes. All the pockets and ends will be hidden by brackets the stairs mount to so it is no big deal.

Paco, I will try to post some pics of the DC setup when I get some. I am also working on a vac sheet loader/trolley track based on what some others have done this board...

[paco]

quote:BTW, this is my first job on the bot...hopefully the next one will be some nice small mdf squares or something :-)If you got the same kind of customer that I have; good luck!


Frank L. vac. sheet loader as gotten me quite dreaming... I can't wait some more inspiration!

Bot on!