Cutting a binding channel

[belbein]

OK, so I'm a little over 1/2 way in my Octave mandolin and I've hit a frustration point. I was trying to cut channels for binding with the StewMac router head and the added binding attachment. I'm getting tear out and inconsistent depths (the horizontal depth is fine, but the depth of the cut into the instrument body is whacky). I tried to cut the 3 mm of depth in about 3 or four cuts, but what should have been my last cut turns out to produce something that looks like a sine wave with a short frequency. I'm sure there's a trick to this, and I'm sure someone out there knows it. I would greatly appreciate your help.

By the way, when I got frustrated I sharpened up on of my chisels and tried that. I might work on softer wood, or maybe if I were better with a chisel, but that didn't really work either. So, any hints on that would be fine, too.

Thanks in advance for your help. (I'm on the road for the next week and may not be able to respond, but know that I will greatly appreciate any assistance!)

[Goodin]

Are you using the Stew Mac router bit with bearing set? To prevent tear out always take a few shallow passes instead of going right to the bearing and make cuts following the grain or whats called "downhill" cuts. You need to make sure all bumps/ripples/imperfections are sanded out as when the bearing goes over a these spots it will show up in the cut.

Maybe you could post some pics so we get a better idea of what the problem is you are having.

[the padma]

Sharpen up an old chisel, then put a hook on it like you wood on a scraper and start scraping the rabbit. Much easier to scrap the rabbit into shape then to try and pair it down with a blade. Lay down masking tape and scrape to the edge.

Then
1/2 in thick sanding blocks shaped sorta like them French curved scrapers. Paper on edges and on one flatside as well....I have several of them with different curves and shapes and grits. I glue to the flat side, but on the edge there are 2 wedge cuts that the strip of sand paper being wrapped around the edge is held in place with~ wedges of course.

If you have to scrape the rabbit deeper to get an even consistency so what...just use additional layer/s of banding.

From experience this is what I have to sometimes do cuz my instruments usually have curved ribs with dome carved backs and tops which make routing difficult, so I often rout out smaller and then scrape to size. Sometime I even hand cut the channels with a Purfling/Binding Groove Cutter knowing that the router just ain't gonna make it.

Finally them dremel head attachments are one step removed from a Mickie Mouse toy...they do work best if you make several incremental cut passes using a carbide bit.



blessings
duh Padma

[sunburst]

You didn't say whether your working on a flat top/flat back instrument or a carved top instrument. The Stewmac set only works on flat top/flat backs, and any induced arch will throw things off a little too. When I make flat top instruments, I use the Stewmac set and follow it with my purfling cutter, working by hand. A little filing with flat files and curved rifflers cleans things up the rest of the way, when needed.
The Stewmac set should give you a cut as smooth as the surface you run the bearing against, so as Goodin says, sand the sides smooth and to the proper contours first.

[belbein]

Thanks for all of the answers. To answer the your questions: It's a more or less flat top and flat bottom. Sides were sanded baby's butt smooth. I did about four passes. I also did the recommended sections first where the cut would be parallel to the grain.

I'm not inexperienced with using a Dremel, but this sucker just taught me real fast that I'm missing some crucial technique. What speed setting do y'all use? Fast or slow? How do you make sure that the bearing rides smoothly on the side? That was obviously a problem for me, judging from the undulations.

Does everyone use the Stewmac for the gross cuts and follow with hand tools? Perhaps my expectations were too ... gross.

[sunburst]

What speed setting do y'all use? Fast or slow?

I use the Stewmac cutter/bearing set in an old laminate trimmer with two speeds: fast and off.
I'm starting to think we may not be talking about the same tool...

[StevenS]

Throw away the StewMac Dremel attachment and get or make a gramil. Unless you are doing many instruments, cutting the binding channel by hand is far better in every way (particularly for your mental health) compared to the Dremel attachment.

Steve

[the padma]

Ok belbein

The first pic is using the older Stu Mac dremel rabbit cutting attachment




The second is using the dremel flex cord extension with a home made attachment




This next pic shows the attachment for the dremel and the home made attachments that each cut out a bit more till I end up with the desired depth of cut.




Here is a walnut curved sanding block showing the wedges used to stretch and hold the sandpaper. The other side of the block has sandpaper held on with double sided tape. I have several of these sanding blocks with different curves to them.




And finally the sanding block cleaning up a cut away.




Hopes this helps.


As mentioned before, sometimes I use a gramil or purfeling cutting tool and sometimes a small hand held laminate trimmer and sometimes a stationary 1/4 inch router....all depends on the shape of the instruments sides and plates and the type of wood thats being cut.


blessings
duh Padma

[Goodin]

I think Sunburst and I do the same method using the router bit and bearing set from SM (http://www.stewmac.com/shop/Tools/Sp...r_Bit_Set.html), using a laminate trimmer. I dont have experience routing with a Dremel. I have heard it's not ideal to use a Dremel for routing binding channels because it doesn't have the power of a laminate trimmer. The Padma's advice might be best for you if you are using a dremel. However I would suggest getting a laminate trimmer like the Bosch Colt and use the SM bit/bearing set. It cuts flawless channels in just a few minutes with no need for hand work.

[belbein]

Maybe we aren't talking about the same tool. Here's what I'm using.

[sunburst]

Yep, different tool. I'm using the set that Goodin linked to.
The Dremel housing is plastic and it flexes, the tool itself is underpowered for the job of cutting binding channels, the small diameter cutter doesn't have enough chip clearance to cleanly make deep cuts, the bearings are too small for the load of binding channels... I'll stop here... just know that there are better tools and procedures for the job.

[Dobe]

[QUOTE=belbein;1067623] What speed setting do y'all use? Fast or slow?

Dremel on high, move it along slowly (in multuple passes, getting gradually deeper)

[peter.coombe]

The Dremel housing is plastic and it flexes, the tool itself is underpowered for the job of cutting binding channels, the small diameter cutter doesn't have enough chip clearance to cleanly make deep cuts, the bearings are too small for the load of binding channels... I'll stop here... just know that there are better tools and procedures for the job.

Yep heard all that many times before. Plus they wear out quickly blah blah blah. Fact is I still use a 19yo Dremel and the old head attachment to cut binding channels, even on guitars. New Dremels are more powerful, but I bought one 18 months ago and it died just after the warantee ran out. The newer adjustible binding attachment that Stew Mac sell nowadays is the most useless piece of rubbish I have ever wasted my hard earned money on, so don't bother with it. The older attachment as pictured by Padma works, but don't use the router bit that Stew Mac sells for the Dremel. The router bit cuts quicker, but chip out is almost garanteed. Use the 115 Dremel bit, a new one for each instrument you make, run the Dremel at max, and take at least 3 passes. Simple, cheap, effective, and does not take up precious bench space. You can go to a lot of trouble and expense on setups for cutting binding channels, but as a believer on keeping things simple, I have never seen any need to change.

[the padma]

Yep heard all that many times before. ..... but as a believer on keeping things simple, I have never seen any need to change.

Amen.

[wwwilkie]

Don't know if anyone has mentioned this yet. For cutting the binding channel on my mandolins and archtop guitars I use different size "doughnuts" in combination with the LMI bearing set on my router table. I just measure the height of the arch first then use the corresponding doughnut to keep the cut at 90 degrees. I don't think it's even really necessary to make different size rings, one that is approximately the right height should be fine. The only real trick is to cut the whole thing in one continuous motion with no stops and starts. Very quick, easy and extremely accurate. I climb-cut the whole way to avoid tear-out. Works great for me.

[peter.coombe]

I think in regard to this it is - whatever floats your boat. Use whatever method works for you. Personally I intensly dislike routers so avoid them if I can. A couple of very dangerous near miss incidences was enough to make me wary. I still use one to cut the channel in the neck, but it is not my favourite activity. Sure, a laminate trimmer (or router) is much more robust and more powerful than a Dremel, but it is bigger, heavier, noiser, more expensive, more dangerous and capable of doing a lot more damage (to you or the instrument) if something goes wrong. Not only that but they can quickly cover everything in the workshop with dust in no time if you don't have good dust extraction right up close to the router bit. I do have a laminate trimmer but only use it to cut sadddle slots in guitar bridges. I prefer to be safer with the Dremel and cut my binding channels outside so the dust stays outside, but that is just me. Other people love routers, and good luck to them, but please be careful and stay safe.

[sunburst]

In fact, I hate routers too and the small laminate trimmer is the only one I use. I might use it for something else once in a while, but the binding slots are the main reason I own the thing, and I only use it for flat tops, mainly guitars. I had a pretty good Dremel tool about 30 years ago, but have almost completely given up on them since, other than the flex shaft tool that I use for inlay and most of the other things Dremels are usually used for (other than bindings). It truly is a matter of "whatever floats your boat", and wwwilkie's router table/shaper method is a good one.

[Rick Lindstrom]

I completely agree with John. I don't feel like the Dremel has enough guts to do a decent job of cutting a binding channel. I use a Makita laminate trimmer with its adjustable guide mounted upside down in a recess cut into an MDF table. Even with this much horsepower, you have to use a nice sharp bit and observe grain direction when making the channel. As always, test on scrap before committing to the actual cut.

Never failed me yet, and no drama involved.

Rick

[hobbspal]

As always, test on scrap before committing to the actual cut.

true....... so true.

[dunwell]

Peter sez "...115 Dremel bit.."

Peter, just FYI, a similar item in solid carbide is available from MSC
http://www1.mscdirect.com/CGI/NNSRIT...MTERM=85285682
and I believe McMasterCarr. Search for rotary files in milling bits and be sure to get the end cutting versions. I too used the 115 bit but they, like you indicate, are burnt and dull after one maple body mando. The carbide ones last quite well.

Alan D.

[Rob Grant]

I always use a Dremel with the simple older style Stewmac attachent (like young Padma and Peter). I recently switched to the newer Stewmac Dremel "router-style" BIT because I was jack of paying so much for an individual #115 and I was tired of their short life span when routing silica rich Queensland Walnut. The newer "router-style" bits worked perfectly for me. Even after doing three mandolins and one octave mandolin the one bit still seems to have tons of life left. The trick I find is to set your Dremel to the highest speed, take light multiple cuts and try to concentrate on maintaining the proper position of your tool on the instrument. Also, and most important, find a secure method of holding your work down so that you don't have to rely on your knees, lap, elbows, etc. to secure the instrument while cutting the binding ledge.

Padma's advice on the ledge cleanup is spot on and well worth following.

[Jim Hilburn]

This is from my funky little tools drawer. It's like a final depth check -slot cleaning tool. Pretty self explanatory. The bigger piece of wood is to clamp the blade tightly in the groove. I don't remember what I used to make the blade slot but I got it very crooked which is a good thing because it also helps hold the blade tightly in place.
It's easy to assume you've correctly cut the binding rabbet but this is just a little insurance to make sure you have a consistant depth.

[mando andy]

Looks like a neat tool Jim....is that a razor blade you are using---or what? Also--just so I understand..which side bears against the top? Seems like you could use this in multiple positions.

Andy

[Jim Hilburn]

Not as self explanatory as I thought.
Single edge razor with the upper portion edge ground down to make it less hazardous. Nothing rides the top. the bottom of the blade rides the bottom of the rabbet (it doesn't trim the bottom since it's not sharp) and the lower part of the wood rides against the side of the instrument. All it's meant to do is scrape the inside wall of the rabbet to a consistent depth all around.

[AaronVW]

My experience is very minimal but I made a jig for my router table after seeing the one Lynn Dudenbostel used and it worked very well for me. I also used a quarter inch down-cutting spiral router bit and had absolutely no tear out, even on my non-instrument grade cedar top with tons of grain run out. Any little imperfections were easily cleaned up with a sharp chisel and small sanding block. http://dudenbostel.leanside.com/6.html