Official Luthiers Forum!

Do you find that if you cut the purfling channel out first (I use the StewMac binding cutting jig) that because the purfling channel is wider (in relation to the side) than a binding channel that you have more tearout problems?

If that is an issue that you run into every now and then can you tell me what precautions you take to try to minimize the tearout. I am already aware of climb cutting when appropriate but are there any other tips out there?

Thanks

_________________
Formerly know as Mandodiddle.

I cut the purfling channels first to give the bearing more of the side to ride on. A coat of shellac or vinyl sealer on the top seems to help.

I cut the bing channels first. Get them right all around then cut the purfling channels. Only way I’ve ever done it. And I always use a sharp router bit. If I’m in doubt if it’s sharpness, I just use a new one.

The only things that come to mind are shellac the top around the edge before starting and use 2-3 steps with the bearings to allow taking multiple passes.

I’ve only had one binding accident where the router rode up onto the top and I was trying to cut the purfling channel in one shot. I step through the bearings now but I know that folks have success taking it in one pass.

Brad


Sent from my iPhone using Tapatalk Pro

_________________
Insta - https://www.instagram.com/cbcguitars/
Facebook - https://www.facebook.com/cbcguitars

The first (and so far, only) time I cut a purfling channel on the top, I cut the binding channel first and then I had a known starting point to cut the stepped purfling channel. Worked fine. I liked the idea of knowing the binding channel was good, and then I could cut the purfling channel next, deeper by the known thickness of the purfling. I knew the binding channel was good, and I knew how much more to cut for the purfling.

Before this last time, I use LMI's full depth laminates for faux purfling, and cut only one channel, installed the laminate and the binding outside of it after the laminate glue dried. Felt less like a one-armed paperhanger. A second, but for me, more controllable step.

_________________
Peter Havriluk

I always cut the purfling channel first for the same reason Freeman mentioned above. I start all the cuts at the tips of each bout and rout "downhill" to the centerline at the tail, to the waist, and to the centerline at the neck block. I do the cut to the full width of the purfling + binding in one go with one bearing. This has worked even with the smallest StewMac bearing that gives a 0.210" wide ledge. I've haven't had tearout happen (knock on wood) on various types of spruce tops or on redwood tops.

The only tip I have to offer is to be rigorous about not routing past the points where you are supposed to stop (like the center of the waist curve) on the downhill passes.

_________________
Once in a while you get shown the light in the strangest of places if you look at it right - Robert Hunter

I climb cut all the way around the guitar body. I will have the bearing set to the final depth, but I won't hold it against the side for the initial cuts, so effectively I am doing multiple passes. After the final climb cutting pass I will sometimes do a "clean up" pass in the normal direction of travel. This tends to pull the router into the work, but there is so little left to rout that it doesn't usually cause a problem.

Even cutting the purfling first you do not have to make the purfling cut all in one go. You can walk down a few bearings before making the final cut.

_________________
http://www.Harvestmoonguitars.com

I learned a trick here first attributed to Mario Proulx (as far as I know). In order to get a consistent finished binding thickness, it's important to flat/level sand the sides before routing the binding channels.

To make this task easier, it is very beneficial to not simply flush cut the top and back overhang, but to also cut deeper than flush. Call this excess cut rather than flush cut. Then you don't have to deal with the endgrain when you're levelling the sides.

Since you're making that cut, you may as well make it as big as you can.

My typical bindings are .070 x .250.

So my excess cut will be .060 x .240.

Then I will level the sides.

Then I cut my binding channels registering off the levelled sides, so most of the cut is only taking off around .010 in depth and height.

Then I do the purflings, which for me are typically .050-.060 x .080 depth. So you're taking off way less material than if you're doing the purflings first.

Always following climb cut protocol...

dull tool ?
if you are getting tear out on the purfling channel , or are you getting feathering? Chip out tells me your cutting technique may be wrong.
I use a little climb cut but rout most. Don't try and take it all at one time. That is why I use fleishman binding cutters. I can control the direction and amount of cut .
Spruce can be problematic

_________________
John Hall
blues creek guitars
Authorized CF Martin Repair
Co President of ASIA
You Don't know what you don't know until you know it

If you are using the Stew Mac router with the graduated sized bearings you can sharpen the cutter on a diamond plate or similar sharpening instrument It makes an enormous difference. Just be aware that if you grind away some of the cutter it will make a minute difference to the depth of the cut that you get with a given bearing. But that is not really a problem in practice.

I thought dull tool too as John Hall mentioned. Shellac, climb cuts and sneaking up on it as Clay does are all what I used to do and it worked great. When my cuts on spruce started to get a little fuzzy I replaced the bit with new sharp one. IIRC my bits needed sharpening or replacement after only 15 guitars or so to get back to really clean cuts.

Funny thing I was always so very nervous cutting the channels and having read all the things that can go wrong such as the bit coming lose that I had a death grip on the PC-310... As such the bearing left a slight impression in the side wood. Not good. So I started using masking tape on the bearings not just to get a finer channel fit but to cushion my death grip on the Lam trimmer. I once asked here if anyone else had bearings leaving impressions from pressing too hard and no one else had that problem or would admit it.

The purf channel is usually the safest cut too since you are not going all the way through the spruce. That ledge tends to hold everything in place. Or at least that's what I think anyway. Are you cutting all the way through the top on the purf ledge?

I've had that happen when the bearing or dust washer starts spinning with the cutter instead of "rolling" along the side of the work as it should. Keeping the bearing clean and well oiled and getting rid of the dust washer and pressing the bearing a little tighter against the work helps, but on softer woods I still run a piece of masking tape around the sides where the bearing will ride. On the plus side -most bearing rash can be sanded out on wood (with Formica it's forever )

I carefully scribe them with a gramil before routing. Eliminates fuzz and tear-out.

_________________
Jim Watts
http://jameswattsguitars.com

FWIW hesh, had the same problem, but would reclassify it as being overly cautious. Death grip , has a rather negative ring to it. Just relax , breathe deeply and say OHM!!

I cut the purfling channel first-full depth and width and the binding channel second, also full depth.

Sharp bit, climb cut.

One thing I have learned throughout the years about binding is that you need to cut the channel between .010"-.020" deeper than your binding.... I always like to take a little of the side down to the binding to keep the binding full thickness.

It's surprising how much space glue takes up.

The more pieces of purfling the deeper you need to go.

A few items that help me.
1. Use a sharp bit
2. Keep the bit clean, sap will build up on it
3. Go Slow
4. Go in the right direction. This is VERY IMPORTANT. Here is a How-to from StewMac showing the correct direction to avoid tear out

https://www.stewmac.com/How-To/Online_R ... rings.html



T

_________________
Joe Beaver
Maker of Sawdust

sharp bits and what I found are cheap replacment bits at aliexpress

_________________
John Hall
blues creek guitars
Authorized CF Martin Repair
Co President of ASIA
You Don't know what you don't know until you know it

That's it and probably why it was happening, user error on my part. It did sand out as you say but who needs it if I could have avoided it all together. I will tell ya that I was always pretty nervous with Lam trimmers for some reason. Probably not a bad thing to be to a point for safety sake. I never had any mishaps thankfully.

Ohm, ohm, ohm..... darn it where's my scotch! Hope you're doing great Ernie my friend.

Hesh, you just mentioned scotch whiskey. Was watching a military parade of the 75 th anniv of VE day on monday in edinburgh scotland, , and they looked like they all had a good swig of Whiskey !!. Somehow they were not chanting OHM!

I sense some resistance.

That joke was a big hit with my electrical engineer friends.

I suppose you mean .001"-.002". That's what I shoot for.

Pat

_________________
Pat