Pattern Bits And Trim Bits

[Woodenspoke]

Well today I had to use a template bit and cut out a body. Because this was a recreation of a fender bass I ordered a template. Of course they sent a template that was only smooth on one side which to me is the incorrect material. Oil hardened hardboard is the proper material which is hard and has two flat sides.

To make a long story short I found the thickness very hard to deal with. Some of my older bits would not even work as the gap between the bearing and the cutter was almost 1/4". Even a new whiteside pattern bit had a 1/8" gap. Why should you care well this is why.

So in order to make these patterns useful I used the 1/4" patterns to make make a 1/2" MDF pattern. I like MDF over plywood, I just think it makes a better cheaper pattern. I do harden the edges with a thin epoxy prior to use but I have done with out. Unless you spend big bucks on plywood the cheaper grades are not always solid in the core and you wind up filling the gaps.

Anyway the bottom line is a 1/4" template has issues. You will most likely be unable to get the bearing centered on the pattern and have the gap between the router and bearing not leave a lip. As in the first illustration above. The larger the bearing the harder it will be to get it centered.

[erikbojerik]

I don't know what other folks do, but when I use a purchased 1/4" template I will always use it to make a working template out of 1/2" or 3/4" MDF and save the original as a master. That way if I accidentally cut into the working template or damage it somehow, I don't bugger my only template. I can always make another one.

Yeah that little edge problem is the reason I use 1/2" or thicker for working templates.

[westhemann]

I had the same problem and used the same solution you did...

[Tim37]

dude i made a template for a pickgaurd today out of 1/4 inch. and was honestly thinking after using it i need to get some 1/2 and make another template. i wish i had read this yesterday.

[SJE-Guitars]

I don't know what other folks do, but when I use a purchased 1/4" template I will always use it to make a working template out of 1/2" or 3/4" MDF and save the original as a master. That way if I accidentally cut into the working template or damage it somehow, I don't bugger my only template. I can always make another one.

Yeah that little edge problem is the reason I use 1/2" or thicker for working templates.

Yep 1st thing I do with any templates is make one to working with and store the originals safely away from my router!

[Woodenspoke]

I thought about 3/4" templates but they are too big for a single pass pattern bit on my router table. With a 2" long cutter that extra 1/4" on the template makes it more difficult to get the router bits shaft all the way up into the routers collet (safely in I mean) and still have enough travel in the router's lift to get the bearing riding far enough up on 1/2" template to make a single pass. With a bottom bearing bit this would not be an issue. But I like the bearing on the bottom for some unknown reason, maybe it time to try a different bit.

In order to use the 1/4" templates to make my 1/2 MDF templates I used a small laminate Trim bit or bottom bearing bit in my router table, using the router table makes the process that much easier as you don't have to worry about the possibility that you may tilt the bit as you work. You only have to concentrate on keeping the bearing riding along the template.

This reminds be I have to duplicate another working custom template just in case. I also have to to add some pickup routing holes in the new one. Then I may just duplicate that one as well. You can never have enough backups.

[Mitch]

Can't you just do this?

[Supernova9]

Or you do one pass on the template and then another pass using the body to cut the ridge off. But yeah, I think the major american website does them in 1/4" because he knows most people will be making child templates to use in anger. I prefer it that way - saves me paying extra for shipping when I have 1/2" MDF/ply always laying round.

[Woodenspoke]

Can't you just do this?

Sure but I think it would just be easier to make a 1/2 to 3/4" template. The price of 1/2" MDF (4' x 8' sheet) in my area is about $10 USD. I can probably get at least 10 templates from a sheet.

[Woodenspoke]

Here is the set I made, probably cost me under $3 to duplicate a $65 Ron Kirn 51 P Bass pattern and 20 minutes of work. Now if anything does happen I still have a master set. Plus another custom template, this will be duplicated today. I will be making several duplicates so I can add pickup, neck pocket and a control cavity routs to the templates.

[Ronkirn]

Here is the set I made,

Now, that's how to do it and keep life simple.

Ron Kirn

[Rick500]

Be careful with very thin templates. It's easier for the bearing to slip off the edge, and in an instant your workpiece and fingers are moving toward the spinning bit.

[Prostheta]

Same rule applies as always I guess, Rick....remove as much of the excess as possible with a bandsaw or whatever before cleaning up with the router (and avoiding climb-cutting as much as humanly possible) as opposed to removing large quantities of material with it, which has always been the cause of slipping, router-swearing and digging out the wood-stretching tool for me!

3/4" thick MDF templates are great for riding two or three bearings against also. I've almost gotten to the point of giving my 1/2" diameter 20mm depth CMT Orange template cutter an affectionate name.

I still get the lip myself, as I don't like the cutter to run shallow against or near the template. If i'm using a 10mm Perspex template or 1/2" MDF, having both bearings run against the template will still leave that lip. Changing to a 1/2" self-guided trimming cutter allows me to do a quick pass around the body using the first cut as a guide (removing the template first of course!). The rest of the body is then cut with the top-mounted three-bearing cutter till the last <1/2" which I then finish off from the other side with the self-guided trimming cutter. Just my way of working, which works for me!

[Woodenspoke]

I certainly agree with the reasons for removing as much material as possible. Besides the obvious climb cutting reduction, as everyone knows makes it more challenging, you are also putting less wear and tear on your bit, and it will last longer between sharpenings.

I still don't agree with the thicker template 3/4 vs 1/2. Also as you introduce more bearings into the process (multiple bits) and start riding along the edge of the body you introduce the possibility of bearing rub into the edge of the guitar. My reasons for buying a Whiteside pattern bit that was 2" high and a stiff 3/4" wide was to eliminate multiple passes. It is a single pass solution (in most cases).

Now I know that you still have to sand out the body even after a single pass, but for people who do not have tools like an oscillating spindle sander the task is more difficult when you add in a bearing rub line. The 1/2" temple makes this single pass possible a 3/4" template would make it much harder (bit height vs shank length makes the process difficult).

Yes such a large bit is harder to control but that is why I have a router table.

Some pictures to show my setup.

Adding an additional 1/4" would move the bit right to the very edge of the top of the body. Here the body 1 3/4" tall is shown with with a 1/2" template and a 2" pattern bit. I have just enough room for a clean single pass. The Bits shank is inside the collet at what I would consider a minimal safe distance. Extending the bit further up (shank moved further outside the collet)would be dangerous.

If you are using multiple bits than the pattern height is not as important, except when you start cavity routing and find your bit too short. Or too long.

I am certainly not saying a 3/4" template is wrong but I find a 1/2" template just right for almost all operations. If i need a higher template I just shim up the 1/2". I would not shim up a 1/4" template as I believe the edge is too narrow in the first place, there is no fudge factor.

Note: The epoxy edge coating on the MDF, helps eliminate bearing rub lines in the template. Mix epoxy with any solvent (almost anything even alcohol) until it is thin then brush it on. A 5 min epoxy will harden in about 15 min depending on how you thinned it. I mix the epoxy first then add solvent. Use a disposable glue brush.

[Prostheta]

Good tips, Spoke. I'm stuck with routing by hand at the moment till I clear out the "workshop" and create better work areas, which is why thicker templates for the "top down" approach suits me. A router table area will be on the cards (or in the bench) soon for sure. I might have to recut some templates in thinner materials, but that's just part of the fun!

Edited April 19, 2009 by Prostheta

[chops1983]

What router bit do you guys use for routing your cavity cover routes? eg. a 2mm deep route using a 12mm template.

[Rick500]

Another area where a thicker template makes things easy.

[Woodenspoke]

What router bit do you guys use for routing your cavity cover routes? eg. a 2mm deep route using a 12mm template.

Really depends on the manufacturer of the bit, you need to figure out how deep your shelf will be, how long the cutting edge is and how far away the bearing is from the edge of the cutter. In this case a really thick template would be a better choice than 1/2". Not everything falls into a standard you have to use this size template category as Rick points out..

Just a quick metric check on a 12mm long pattern bit. 2mm (shelf depth) minus 12mm = 10mm above the hole, but your bearing is 6mm (to center) away from the top of the bit. Just making this up for reference. So now you have 16mm to the center of the bearing with a 2mm deep cut. But you want some template above the bearing as well so lets figure 20mm would be a minimum template size. Its all just basic math or as most people do eyeball the bit and pattern and see where your bearing rides the pattern.

In the same inch scenario a 1/2" deep pattern bit would need a minimum of a 3/4' template but a 1" template would be a better choice. I would glue two 1/2" MDF pieces together.

[DC Ross]

What router bit do you guys use for routing your cavity cover routes? eg. a 2mm deep route using a 12mm template.

I use a straight bit with a template guide. Here's a cheap guide set that works well.

[Woodenspoke]

What router bit do you guys use for routing your cavity cover routes? eg. a 2mm deep route using a 12mm template.

I use a straight bit with a template guide. Here's a cheap guide set that works well.

The only issue I have with the template guides are that you have to make your pattern so it allows for the guide offset. If your routers base plate isn't perfectly centered it will make a real mess of the job unless you keep the same side of the guide against the template. With a cavity cover ledge choosing a method is always difficult, it is best done with your bit facing into the cavity rather than using a pattern where your bit faces outward. you can even use rabbiting bit (jrentis said) if the hole is the same shape as the cover since the hole is the pattern.

[chops1983]

Thanks woodenspoke. I figured as much but i thought i would ask. I alreadly have a guide set that comes with your router but the problem with this as woodenspoke said is the offset. I have made templates that work with the offset but it is a bit of a pain in the a**!