Hold down for board blank...

[harryball]

I just can't seem to get past this issue with this project. I'm cutting a project from 24" x 9" x 3/4" purpleheart blanks. The production file is done. After I zero Z the Master part file touches off the top of the material and calculates exactly how thick that blank is and it's ready to run. Speeds are good, purpleheart is not turning black everything is good but...

Holddown is driving me nuts. No attempt at a vac holddown is successful. The parts are too small and irregular to come up with an easy vac mask to prevent vac loss during cut through.

I tried screwing it down but unless I run off an extra foot on each end the brittle wood will split 25% of the time while machining. If I slow down my feed rate to reduce pressure the wood turns black. If I reduce RPMs the cut starts to turn rough and my RPM's are too low for the power needed to make the cuts. It also takes longer to attach and remove.

I've given clamping a limited try and it's my next focus. I need to keep the block rock solid and held down since I'm using an upcut bit. I've been looking at other threads and have a few ideas, but I don't want something overly complicated that'll take a week and a machine shop to build. I also looked at those back to back clamps and except for the cutting through problem the idea would work.

Just talking out loud here, any suggestions and/or photos of ideas would be greatly appreciated.

Robert

[patricktoomey]

This may sound strange but I've used it in a pinch with Corian cutting in the past. I take a hot glue gun (NOT hotmelt polyurethane, just regular old hot glue) and lay some light beads down on a Corian or MDF or plywood sacrifice board that's a little larger than your work piece. Then after letting it cool for a few seconds, I push my workpiece down onto the hot glue. It holds really well and even supports slightly warped material. Then when the cuts are done you can carefully pry the parts off the sacrifice board and scrape off the hot glue.

The ideal would be if you could lay your hands on some Corian or equivalent material to glue your parts to. The hot glue will easily scrape off solid surface material to release your parts and it will hold down to your vac table incredibly well since it's so smooth and flat. Otherwise, plywood, especially prefinished or even MDF will work.

Like I said, it sounds a little strange but it may work for you.

[richards]

I just finished building a "Festool Multifunction Table" type clamping board that sits on top of my regular vacuum spoil board. The clamping board has 300 holes (20mm diameter, 20mm deep) spaced every 96mm over the surface of a 97" x 49" sheet of 1-1/4" MDF. Using just two Festool Clamping Elements (part no. 488030) to hold down a 6" x 96" x 1" alder board works incredibly well. I'm able to surface plane the lumber, using a 1-1/2" Freud cutter at 7-ips while removing 0.050" of material. Holding down plaques for V-carving couldn't be any easier.

The clamps are only 3/4" inch tall, so they don't interfere with the spindle or dust collector. I'll use 'spacers' (1/2" thick lumber) when there's a possibility of the cutter striking the clamps.

One of the other major benefits of using this type of clamping board is that I don't have to remove it when doing regular work. The Fein vacuums have no trouble sucking through the clamping board.

The main reason that I went this route was that setting the Festool clamps is much faster than digging out the GAST vacuum, hooking up the air hoses, re-taping the pucks, etc. It's simple, relatively inexpensive (the clamping elements cost $80 for a package of two), and extremely versatile.

(By the way, because I have absolutely no extra space in the shop, I've reverted to using my Festool equipment to do almost all of the work that I used to do with my Unisaw, shaper, planner, jointer, and radial arm saw. It's really good equipment, and it gives excellent results.)

[bill_l]

Mike,

Would you be able to post a picture of this setup?

Bill

[richards]

Bill,
These are really poor quality photos - it's 10-degrees in the shop this morning and it seems that even the tripod was shivering.


4893

The Festool "clamping elements" have a 3/4-inch barrel-shaped extension that slips into the 20mm holes, similar to a bench-dog.



4894

This photo shows the clamp with the lever in the closed position. This is a piece of rustic alder that I surface planed last night with a Freud 1-1/2" cutter (the same cutter that I normally use to surface the spoil board). It takes about two minutes to surface a 5-1/2" X 96" board to a depth of 0.050". The resulting surface is equal to the surface finish that I normally get with my 15" PowerMatic planner.



4895

This photo shows more of the table. The piece of 5-1/2" X 96" rustic alder was securely held by two clamps, the one that you can see and another that is positioned towards the other end of the board.

[srwtlc]

Mike, I've often thought about a setup like that, but thought I'd forever be vacuuming debris out of the holes.

[denver]

That looks very versatile. How long are the stems that extend into the table? In other words, how deep do the holes have to be?

Thanks,

Denver

[richards]

Denver,
The holes need to be at least 18mm deep. I went 20mm. That's the main reason that I used 1-1/4" MDF. I didn't want the holes to go clear though the board.

Scott,
All you need to do is post a sign in plain view stating "No Dust Nor Debris Allowed". It works for me.

[bill_l]

Mike,

Thanks for the photos, an excellent set up that I might try out. Where did you order the clamps from? By the way, where are you located and is that 10 degrees F or C?

Bill

[srwtlc]

Mike, where did you get a sign like that! I could use one of them! I don't suppose just any ordinary V-carved sign will do the job?

[aaasigncom]

HOLDING PARTS - I TAKE A SCRAP PIECE OF WOOD A COUPLE OF INCHES LARGER THAN MY WORK. I SCREW TO THE TABLE. THAN I MACHINE A .2 RECESS IN THE SCRAP THE SAME SIZE / SHAPE AS MY WORK. THIS GIVES ME A PERFECTLY LEVEL BASE TO INSERT THE MATERIAL INTO. SINCE IT FITS TIGHTLY INTO THE RECESS, IT CANNOT MOVE IN Y or X. JUST A COUPLE SPOTS OF HOT GLUE WHERE THE WORK FITS INTO MY JIG, ITS NOT GOING ANYWHERE. NOW I HAVE A JIG FOR PERFECT REPETITIVE SURFACE CUTS.

[richards]

Bill,
If no one carries Festool in your area, you can log onto at www.festoolusa.com (http://www.festoolusa.com) to order. In Salt Lake, the local WoodCraft store carries Festool supplies, but they're not a stocking dealer, so large items have to be ordered from the factory; however, we also have M&M Tool, which is a stocking dealer. According to the 2006 Festool catalog, they have dealers all across the country, many that are stocking dealers. (For those who aren't familiar with Festool, until recently, you either had to order from the factory or go to a dealer and then have the dealer order from the factory.)

That temperature was 10-degrees F. Today is much warmer, somewhere in the mid thirties - almost swimsuit weather!

Scott, you're right. Not just any V-carved sign will do the job. How it's done is a closely held secret among us Mormons.

By the way, Tony's idea sounds like an excellent way to setup for repetitive parts.

[patricktoomey]

Another good source for Festool stuff online is McFeely's ( http://www.mcfeelys.com/festool/ )
Direct link to clamps... http://www.mcfeelys.com/festool/product/488030

For anyone not familiar with Festool, they are definitely some of the finest tools in the world, but be prepared for some sticker shock as they are also some of the most expensive. You get what you pay for :-)

[harryball]

Good information and suggestions.

Tony, I've tried the pocketed recess and it still allows for XY movement. The very slight tollerance differences between the blank and the jig show up in the overlap cut.

Mike, I've not found a local source for the Festool clamps, they look promising. How does this method hold up when using an upspiral bit? Does the lift effect ever pull the board out of the clamps?

Robert

[gene]

Robert
Have you tryed an down spiral bit, This should help in the holding and eliminate the lifting . I went thru this same issue and the change of bit helped me alot.

[jseiler]

I had clamps made by black and decker that worked much like the festool clamps. After having run bits into them several times, I posted on the list asking for advice on where to get replacements. The short story is...they don't make them. Bill P. suggested making my own clamps using threaded wooden dowel using this jig.

http://www.bealltool.com/products/threading/threader.php

I have this project on the back burner, but I have the jig. Its great!

John

[bill.young]

What about using pieces of dowel in the holes and then driving wedges between the dowel and the material to hold it tight? You can get a lot of force from a wedge and they can be cut from scrap so it's not a catastrophe if you hit one.

[harryball]

I've changed to a single flute straight bit. Downspirals build up a lot of heat on the 3/4" purpleheart turning the wood black.

I've come put with a hybrid sort of hold down that is working. I'll have to get a photo of it and post. Nothing grand, but it seems to be working.

Robert

[harryball]

Here's a photo of what I came up with. It works pretty well and is a combination of techniques discussed here. The holes under the blank go all the way through and the board is 3/4" MDF that does not allow much vacuum through it.

The cams have a 3/8" dowel in them offset by 3/16" and the back of the board presses against the 3/8" dowels inserted into the MDF. The entire jig is carbide friendly.

First I place the 16" x 48" jig on the table with a section of hard boards to close the vac zone and power up the vac for that quadrant. When I place the blank on it sucks down fairly tight. Then I use small filler strips and turn the cams to pinch the board in place. It works fairly well, my biggest issue is my desire to over tighten the cams. It really doesn't take that much pressure to hold everything secure.


4896

Here is what the final cut blank looks like with the (registered and trademarked)product still tabbed in...


4897

The client has spent a good deal of time and money developing the design. It's by happen stance that I'm involved... but I've enjoyed the challenge.

I've enlarged the blank for the next run. Added a few inches on each end and widened by 1".

Robert

[terryd]

Holy Moley Batman ! Your getting good at this stuff! Every thing you do looks good and your shop always looks clean.. If you ever run away to the great white north (most years, I played golf on the weekend.) and need work, look me up.

TerryD

[harryball]

I'm flattered...

Moving north, very tempting, you don't know how tempting... I've considered moving to Alaska but the wife won't have it. We're looking at Wyoming, but who knows.

Clean shop? The camera must create an optical illusion :-) Seriously though, my shop is attached to the house and disguised as a garage. It does stay clean, my kids come in and clean regularly and work out here also, ages 8 and 11. It's great after I work all day and the cleaning elves stop by. The next morning I walk in and it's all cleaned up!

It really is a shop first, always has been but I have 3 insulated roll up doors on one wall that come in handy. I built the shop to match the house size so I maxed out at 27' x 37' to make things fit... I call it a 30 x 40 to make myself feel better.

I enjoy doing this type of stuff waaaay too much. I spent about 1 hour drawing and laying you what you see and I've spent many hours tweaking. Everytime I cut two units for the guy I tweak the file here and there. I ran 4 of them today. I only get about $40 per completely finished. Machine time is about 12 minutes now. The project is finally "grown up". All I need is a call and how many. I can run it start to finish without any CAD/CAM work. Just load and run.

I like to get a complete process nailed down and then run with it. One offs don't thrill me that much though I've done many. I think I'll develop this hold down method for more projects.

Well, don't want to ramble too far off topic.

Oh, wanted to add, this board is fantastic. Without everyone's shared input and experience I don't think I'd have found this solution. I hope my input will be useful for others.

Robert

[gene]

What does the sign look like put together?
Could you post a photo ? What are they used for?
Thanks

[jhicks]

Looks like you maye have it solved but just in case you havent tried it yet, run the tool path with cuts down to leave approximately .125" as an onion skin layer, then cut through that in the final pass. not much torque so pieces tend to stay pretty stable. of course tabbing would also work but then you need to cut the tabs out. we find the combination of a thin onion skin on the final pass, and vacuum or other hold downs on base stock works well.