# Double sided tape for router template?



## MusicMan

I have some delicate routing to do using a template for cutting internal ellipses. I have excellent mrmdf templates very kindly made for me by Droogs, made more than a year ago in fact but I've been kept out of the workshop by medical and family issues.

The material is maple, about 12 mm, and only one side of the workpiece is accessible (it's a closed box and had to be made that way). It's the soundbox of a harp, so is highly visible and has to be right first time. I have some offcuts on which to get the feel of cutting the various quadrants to avoid tearout.

So I started setting up a practice piece, and find that my double-sided adhesive tape for mounting is decidedly aged and looks untrustworthy. The makers' label has of course long disappeared. I am looking for a recommendation for double sided tape or tapes that will hold a flat wood surface strongly enough for template routing, yet can be removed from both work and template without damaging or staining the work, or damaging the template. 

I have some carpet tape but that leaves quite a gooey mess on removal. (The final finish will be French polish.) The UJK tape from Axi looks good but may be too strong, as it seems to be designed for a more permanent bond.

Is there a suitable tape that someone can recommend from experience? Or is the guitar makers' trick of using masking tape on each piece, then superglue in between likely to be more satisfactory?

I'd also welcome suggestions for the best router cutter (with top bearing).

Thanks

Keith


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## custard

Are you saying you only have access to one side now, or will only have access after the component is made and assembled?

Doubled sided tape isn't usually a problem, but that's because you can generally apply some pressure with an F-Cramp to increase the bond. However, if you only have access to one side now then you're unlikely to have that option.

If that's the case this becomes quite a dodgy process. Most commercial workshops that I've been in frown on using double sided tape for copy routing, because the craftsmen always chance their hand by using the barest minimum, and then the tape can let go or creep mid cut.

I use Tesa double sided tape, this German company makes a wide range of superb tapes for woodworkers, Tesa veneer tapes is an industry standard. Their double sided tape has a ferocious grip but removes cleanly with no residue to screw up your finishing. 

https://www.tesa.com/en-gb

Only problem is that Tesa knows how to charge, but a high risk job like this isn't the place to save a quid or two!

You'll find a great range of copy router bits at Wealdens.


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## Nelsun

Never tried it myself but using two pieces of masking tape with super glue between them did sound like a clever idea... and a lot easier to get off. Think it was an English guitar maker on YouTube I saw demonstrating it.

*clickityclack* And here he is: https://youtu.be/ub6PsY4cgwg


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## custard

I'll say it again, unless you can apply some cramp pressure to the tape then this becomes a much riskier operation. The OP needs to think about that first before deciding if he's going to add to the risk with some DIY tape!

Don't forget, there's _always_ alternative options. Does the template overhang the component? If so can it also have some cramps at the edges where there's supporting timber? Or what about cutting through apart from say 1mm, cutting that out with a pad saw, then either finishing with abrasive paper/file or doing a final router pass to clean up? There are usually loads of options once you sit down and think about it.


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## AndyT

A picture of the harp would help, but is it possible to put the template in the middle of a much larger piece of wood which spans all the way across and could be clamped?
Even if it means making a deeper cut?


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## MusicMan

Thanks for the very helpful comments. In particular, thanks for the experience, Custard, concerning clamp pressure on the tapes, which I was not aware of - I've done a fair bit of template routing but almost always where I could screw the template to an unimportant part of the work. And also for the confirmation the the right Tesa tape holds well but can be removed without residue. Could I trouble you for a product code or link to the actual tape that you use, Custard? As you say they make many types and it isn't obvious which is best. 

For info, here's a couple of pictures, first of the overall structure (the part carrying the strings and the front column are not glued to the soundbox but held by locating pins and string tension when they are fitted):







at this point neither the soundboard nor the back board were on. The soundboard has to go on first, since access is required to its back at this stage, and it's somewhat better to fix the back first and then align the back holes; though I might rethink this next time!
Here are the elliptical templates made for me by Droogs, with the soundbox in the background.

The soundbox is here mounted in the jig I made for assembly, and you'll see (Andy) that it is explicitly designed to get cramps close to the edge, for gluing the back on. It rests on cauls which allow clamps to get underneath. So indeed I can use these for cramping the tape on. Following yours and Custard's remarks, I realised that I can easily cut a hole in the middle of each ellipse, into which I can get a small F or G cramp to increase the pressure near the edge of the template. That will be well worth doing.

The masking tape/superglue method isn't quite DIY, as it was developed and used by professional luthiers https://www.youtube.com/watch?v=ub6PsY4cgwg
But I do take your point that it would be an experimental technique for me, and I'd be better off using taking the lowest risks.

So, Tesa tapes and much clamping it will be. Here's the test piece. 






The plan is to start with bush plunge routing to remove the bulk of the waste to a few mm from the line and work out the routing pattern (uphill with risk of tearout, downhill with risk of runaway ... bump routing?), then to go to a bearing copy router. 

I have a number of straight-flute copy routing bits, but I wondered if there were any recommended types (e.g. spiral or slanted rather than straight?) to improve finish on the end grain in particular, since it can't be avoided when cutting a closed form!

Thanks again

Keith


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## AndyT

It looks a fascinating and challenging project.
I still don't understand why you can't just clamp the (quite wide) template onto the work, without any tape.
Or even cut the hole before fitting the board onto the box - in which case I'd have thought clamping down to the bench, or screwing down to a sacrificial board would be ok.

Do let us see the next step!


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## MusicMan

AndyT":399pw12a said:


> It looks a fascinating and challenging project.
> I still don't understand why you can't just clamp the (quite wide) template onto the work, without any tape.
> Or even cut the hole before fitting the board onto the box - in which case I'd have thought clamping down to the bench, or screwing down to a sacrificial board would be ok.
> 
> Do let us see the next step!



Thanks Andy. The picture is quite foreshortened and the templates are only just a bit wider than the work at their locations. So I can't clamp the templates onto the work and then route, as the router would hit the clamps. 

I can't now cut the hole before fitting the board to the box, as it is already glued, with Aerolite! The recommended order of assembly (this is my first harp and I am following an existing design) was sides, front (soundboard, with ribs), back, then cutting the holes in the back. The soundboard certainly has to be done first because of the intricacies of fitting the column/arch assembly to it. It might have been possible to cut the holes before mounting the back, but I didn't. Not without thinking about it; for the first one I wanted to eye up the proportions and locations before deciding on the hole sizes and positions. You also need to ensure that you can get a hand in there to fit the strings in all the holes from top to bottom. The design was vague on these dimensions. If I do another to the same pattern it would be better to do as you suggest. 

I'll certainly show the progress, warts and all! Very worst case I take the back off and make another. 

Keith


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## AndyT

Ah, thanks.
But it might still be possible to extend the templates with some thin wood or a second piece of mdf. The new cutout wouldn't need to be accurate - just a diamond, a bit bigger than the oval, close enough so the router base is well supported. You could even screw through the template into side pieces which would exploit the wedge shape of the box and snug up nicely.

This all assumes that the reach of your router bit is enough. I have very little experience of power routers so can't help with that but others can.

I just hate to think of strong tape damaging the surface of your work.


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## custard

PM me with your address and I'll send you some Tesa double sided tape to try, all I know is it's their red DST!

But going back to Andy's point, and picking up on the previous theme that there's always another option, even if the cramps are fouling the router it may still be possible to cramp the template. A method I regularly use for copy routing is to rout in small sections and move cramps in stages.

This sequence of photos illustrates the principle.

Here's a router template overhanging the edge of my workbench (you'll have to imagine the workpiece underneath the template, just protruding by say 1mm) as you can see the router is free to route the first half of the curve.





Now here's the critical bit. Before removing a cramp I first add a cramp. This discipline is what maintains perfect registration.





Then a cramp is removed, which allows the router to complete the curve.





This is a simple curve that can be completed is just two stages, but I've done much more complex curves that require half a dozen stages. As long as you follow the rule of never removing a cramp before first adding a cramp, then you can go on indefinitely and still deliver a flawless end result. I mentioned earlier that in many commercial workshops the use of double sided tape for copy routing is prohibited, well it's techniques like this that are used instead.


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## Phil Pascoe

I've used routing templets stuck down quickly and easily with hot melt glue.


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## custard

Here's a another option to consider, a combination of double sided tape and cramps.

I copy route the legs of this Shaker table,





Here's the template,





This template gets used on a router table or a spindle moulder. Therefore I can only use toggle cramps and stops at the ends, which means the centre of the leg upright could flex during the operation. Two pieces of one inch long double sided tape are all that's required to remove this risk.

Maybe you could do something similar and employ cramps and double sided tape together?


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## dynax

hot melt would be my go to solution,


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## MusicMan

custard":30jcs48a said:


> Here's a another option to consider, a combination of double sided tape and cramps.
> 
> '''''
> This template gets used on a router table or a spindle moulder. Therefore I can only use toggle cramps and stops at the ends, which means the centre of the leg upright could flex during the operation. Two pieces of one inch long double sided tape are all that's required to remove this risk.
> 
> Maybe you could do something similar and employ cramps and double sided tape together?



Yes that looks like a very good idea. I have used this method before in other circumstances. I am also going to remove the centre of the ellipse by boring, to get a cramp inside and tighten up the tape. 

When using the Tesa tape be removed without damaging a mrmdf template ok, after a good cramp tightening operation on it?

Keith


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## MusicMan

custard":18pzkcyh said:


> PM me with your address and I'll send you some Tesa double sided tape to try, all I know is it's their red DST!




PM sent. That is a very kind offer, Custard, much appreciated.

Keith


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## MusicMan

AndyT":2kiisno5 said:


> Ah, thanks.
> But it might still be possible to extend the templates with some thin wood or a second piece of mdf. The new cutout wouldn't need to be accurate - just a diamond, a bit bigger than the oval, close enough so the router base is well supported. You could even screw through the template into side pieces which would exploit the wedge shape of the box and snug up nicely.
> 
> This all assumes that the reach of your router bit is enough. I have very little experience of power routers so can't help with that but others can.
> 
> I just hate to think of strong tape damaging the surface of your work.



Thanks, Andy. Exploiting the wedge shape of the box to help clamping is a clever idea! I shall use that, if possible. 

Not sure if the reach would be enough to use an extender piece, but I think that, as Custard suggests, combining a multistep clamping method with a wedge caul or cauls and some DST will be the answer.

I am definitely doing a trial run on scrap before attempting the harp itself, both to practice the technique and to check for damage to the work or the template.

Keith


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## MusicMan

custard":2d93ewer said:


> ... all I know is it's their red DST!



Looks like it might be this stuff, based on the colour, description and cost!

https://www.amazon.co.uk/Tesa-4965-T496 ... PG7FWH1440


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## Droogs

Hi Musicman,
Glad to see you're getting back to it, hope all is OK with you. If you want, I can do you some more templates but put them on wider pieces of board with some slots that would allow adjustable side battens to be fitted and be wide enough that by using some threaded bar or clamps a base board could be fitted underneath and the whole lot tightened up to ensure position and prevent movement.

Just send me the dimensions (widest, narrowest and length) of the sound box and I'll make something up on the big SMC CNC. Oh, will need the ellipse radii for each of the holes again as I can't find the old pm. I do remember them each getting gradually smaller


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## Droogs

MusicMan":2bd35cgc said:


> custard":2bd35cgc said:
> 
> 
> 
> ... all I know is it's their red DST!
> 
> 
> 
> 
> Looks like it might be this stuff, based on the colour, description and cost!
> 
> https://www.amazon.co.uk/Tesa-4965-T496 ... PG7FWH1440
Click to expand...


that looks like it's just duct tape not double sided 

forget this just saw the description at the bottom, rather than just the header 

my bad


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## custard

Yes, that's the stuff. I'm happy to send you a sample first for you to try. Personally I'd be tempted to take Droog up on his very generous offer, a template you can cramp down will always be the least risky option.


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## MusicMan

Droogs":2j5etie5 said:


> Hi Musicman,
> Glad to see you're getting back to it, hope all is OK with you. If you want, I can do you some more templates but put them on wider pieces of board with some slots that would allow adjustable side battens to be fitted and be wide enough that by using some threaded bar or clamps a base board could be fitted underneath and the whole lot tightened up to ensure position and prevent movement.
> 
> Just send me the dimensions (widest, narrowest and length) of the sound box and I'll make something up on the big SMC CNC. Oh, will need the ellipse radii for each of the holes again as I can't find the old pm. I do remember them each getting gradually smaller



That's another very kind offer. Let's see how I get on with the present ones and I'll come back to you if it is problematic. I can cut slots for clamps in these anyway, so they may be fine, and I never like to cause unnecessary work!

Thanks

Keith


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## MusicMan

custard":29xordgv said:


> Yes, that's the stuff. I'm happy to send you a sample first for you to try. Personally I'd be tempted to take Droog up on his very generous offer, a template you can cramp down will always be the least risky option.



Thanks again, yes I would indeed like a sample. I've PMed you my address.

I think there is enough scope to get clamps in my present templates and setup, so I will try after making wedges and cutting slots, but it is also very generous of Droogs.

I have had success using the clamps on the trial piece held in the vice. With just two clamps on one side, I first drilled and jigsawed out the bulk of the hole. At his stage I could easily get a cramp in to tighten the tape bond. Then I used a 12 mm straight 2-flute router with a bush slightly larger:







This left just enough to allow the final cut to clean it up. This was done by the same tool with the bearing follower. The clamps can be seen in this picture:





The accuracy was fine with just a little roughness where the cutter was rotating against the grain, and a small mouth of router burn thanks to my technique:





which cleaned up very nicely with a couple of minutes on the oscillating bobbin sander ... just what I bought it for!






The cut is now clean and smooth. The precise accuracy is not important; the idea was to get an elegant, smooth shape that looked right visually, which I think it is.

If I can find a copy router bit with a shear cut I think that would improve things, and some tape as well would give belt and braces.

Thanks all for your help. I'll keep you posted.


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## Phil Pascoe

If you are to invest in a shear cutter think about one with top and bottom bearings - it gives you the freedom to work something with the templet underneath - not relevant to what you're doing now, but who knows?


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## MusicMan

Thanks to Custard's very generous gift of Tesa tape, I've done the evaluation. 

A short length of 25 mm tape was stuck onto the mdmd in a safe place:





The maple was placed on this:




then rollered down. I didn't try particularly hard to get it as flat as possible since I preferred to have a less-than-ideal specimen. It was then clamped in the vice for a few minutes:
Then the maple was pulled sideways (shearing the tape glue lines) using a heavy spring balance:









It came off at about 10 Kg force. Both surfaces were undamaged. The MRMDF was discoloured a little but the maple was not (it still has tape on the surface). A little sticky residue stayed on the maple in parts but was easily removed by finger rubbing and domestic Sticky Stuff remover.

That is quite adequate to hold stably while routing. I can't push that hard holding a router. So, two lengths of tape either side, plus two or three clamps for security should be fine.


Keith


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## Droogs

good luck and happy routing


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## MusicMan

Thanks, Droogs. One of the reasons I had such a long gap after you made the templates for me was that I got "trigger finger" problems in a finger on each hand, which meant that I couldn't hold many woodworking tools without making it worse, for several months. Happily, hand surgery corrected one hand and the other gradually ameliorated through physiotherapy. Fortunately I could still play the clarinet, that counted as good physio, but it's nice to be able to hold tools again!

cheers, Keith


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## AndyT

Interesting to see how a quality product gives good predictable results. Probably because I have only ever used unbranded double sided tape, I was thinking that there was a risk of spoiling the surface when removing it. I'm reminded that there's a lot of research into adhesives leading to some clever applications, such as self adhesive hooks which hold well but can be removed cleanly by stretching just the adhesive goo, at the correct angle.


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## MusicMan

Andy, that was my concern as well, but I'm reassured by the trial. You are right, there has been a massive amount of research in adhesives in the last few decades. Even metal airplanes and cars are held together with them (e.g. Lotus chassis, airliner panels). These, of course, have to be consistent. Tesa seem to me a serious company whose aim is to know everything about tape and produce appropriate products for the different applications. It will get a lot of use in my shop now.

Keith


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## MusicMan

phil.p":1c9almwc said:


> If you are to invest in a shear cutter think about one with top and bottom bearings - it gives you the freedom to work something with the templet underneath - not relevant to what you're doing now, but who knows?



Good suggestion, Phil. After much search I settle on this up/down shear cutter from Wealden Tools, which they claim is unique. It looks ideal, so is worth waiting for.

https://www.wealdentool.com/acatalog/On ... m_871.html

I got distracted from the harp by an urgent bookcase build for the son!

Keith


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## Phil Pascoe

https://www.wealdentool.com/acatalog/On ... im_23.html
Is the one I've got, but yours is probably more versatile.


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## MusicMan

Ah yes, I looked at that one. On the task I have right now, I was concerned about the lower edge, which cannot be supported in my setup, chipping a bit under a down shear bit.I'll show how it goes (too cold for the shop right now!).


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## custard

MusicMan":3cy0c6ns said:


> phil.p":3cy0c6ns said:
> 
> 
> 
> If you are to invest in a shear cutter think about one with top and bottom bearings - it gives you the freedom to work something with the templet underneath - not relevant to what you're doing now, but who knows?
> 
> 
> 
> 
> Good suggestion, Phil. After much search I settle on this up/down shear cutter from Wealden Tools, which they claim is unique. It looks ideal, so is worth waiting for.
> 
> https://www.wealdentool.com/acatalog/On ... m_871.html
Click to expand...


I use those, like most Wealden tooling they're excellent.

Incidentally, using a shorter copy routing bit (rather than the standard kitchen fitters super long jobs), can be a lot safer when working on a template cut cramped to the edge of your bench.


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## MusicMan

custard":12aas74w said:


> MusicMan":12aas74w said:
> 
> 
> 
> 
> 
> phil.p":12aas74w said:
> 
> 
> 
> If you are to invest in a shear cutter think about one with top and bottom bearings - it gives you the freedom to work something with the templet underneath - not relevant to what you're doing now, but who knows?
> 
> 
> 
> 
> Good suggestion, Phil. After much search I settle on this up/down shear cutter from Wealden Tools, which they claim is unique. It looks ideal, so is worth waiting for.
> 
> https://www.wealdentool.com/acatalog/On ... m_871.html
> 
> Click to expand...
> 
> 
> I use those, like most Wealden tooling they're excellent.
> 
> Incidentally, using a shorter copy routing bit (rather than the standard kitchen fitters super long jobs), can be a lot safer when working on a template cut cramped to the edge of your bench.
Click to expand...


Thanks, Custard. I have ordered the shortest one they do (30 mm).


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## MusicMan

OK finally the success story.

The up/down shear cutter from Wealden worked very well. After a delay caused by finding I didn't have an 8 mm collet for any of my 4 routers (!) I got one for the small Katsu router. I gave it a test run on a scrap piece of maple to get used to it. Then I taped up the work all round the hole using the excellent tape kindly sent by Custard, then was able to squeeze it all round from inside the rough hole, following advice by Andy to tighten it down well. I don't think it would have been stable without this. I then got cramps all the way round, and ditched any when needed to access different parts the hole (Custard again). So the ellipse was cut in parts and there was not a jot of movement of the template.






The three ellipses were cut in succession in a similar way. The templates made by Droogs worked perfectly. The templates were removed by using a wedge with a shallow taper, and there was no damage to either work or template.

And the final result was much to my satisfaction:






This is raw, without edge rounding or sanding and I am very pleased. Many thanks to Droogs, Custard and Andy for their help and advice. Well worth asking advice, taking it, and going slow!

I'll now go back to the harp build thread and pick up from here.


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## Droogs

How did this turn out Keith?


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## peter-harrison

Hi, these people do very nice router bits which I have used for similar work.
https://radiantools.com/


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## MusicMan

Droogs":xirb3lmt said:


> How did this turn out Keith?



The ellipse routing using your templates and the up/down shear cutter worked out really well. I then just rounded over the sharp edges and took the edge off the inside. Many thanks for your help.

The harp itself has not progressed much. The next step is sanding and French polishing the sound box and pillar/neck. Unfortunately, I contracted angina in the spring, which severely limited my mobility and workshop time till it was sorted out. I couldn't risk continuous activities even such as sanding (seriously) till it was diagnosed and sorted. The angiogram showed that I have ceramic arteries with a severe calcified restriction. Fortunately it could be fixed with a stent, but they had to blast the constriction with ultrasonics to crack it up before the stent could be inserted. Brilliant technology.

Anyway that has only just happened; I'm waiting for the final sign-off, but feel much better and beginning to do things again. Won't be long before I am back on the harp, and I'll report WIP as usual.

Cheers

Keith


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## Droogs

So sorry to hear about the problems, hopefully all sorted now and you can get back to the things you enjoy. I look forward to following the WIP, can't wait to see how it turns out. My other half is a storyteller and is kind of trying to persuade me to make her a lap harp kind of thing :roll: I want to find out how you get on first, hard, easy nigh on impossible bits first, to see if I'm willing to wast cash on trying it


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