Template copy. (But smaller) (Full Version)

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Stu -> Template copy. (But smaller) (May 19 2020 11:24:10)

Hi Guys
I want to make a side form for a side bending jig.

I want to make it 5 ish mm smaller than the true size of the body side to allow room for heat blanket etc.

is there a way to make a copy of my body template but.... 5mm smaller?

I don't know how this would be done in normal woodworking but I imagine there is a standard way people do it. ??

I'm thinking perhaps workpiece on the router table. template fixed on top of that then a stop on my router table offset from the bit that my template runs along (over the top of the bit, but with clearence obvs)

Thanks
Stu



RobF -> RE: Template copy. (But smaller) (May 19 2020 12:02:33)

If I’m understanding the question right, you could either use a rabbet bit on the router table and make a new template from an inside form or you could use a pencil in a washer to make a tracing from an outside mold and cut that out with your bandsaw and sand the cut smooth.

I have an LMI machine and I did what you are planning and made a mold whose shape accounted for the blanket, etc. I find I almost always have to touch up the sides on the pipe afterwards, however, which means my effort to achieve a high level of accuracy wasn’t really necessary. Generally the pipe is used to re-establish the curves exiting the waist and also the curves of both bouts.

If I were to do it all again, I would draw the form up with an accurate curve for the waist and with slightly exaggerated curves into and out of the bouts to account for spring back. For example, I moved on from the original plantilla used to establish my form and have used the same form for I think four variants off the original plus two variants of another plantilla that I drew up. I’ve kept the basic waist curve as a common element for all the new shapes, however, with the bouts being the variations. I haven’t found it necessary to make a new form and just see the adjustments with the pipe as being part of the process.



Tom Blackshear -> RE: Template copy. (But smaller) (May 19 2020 14:25:18)

quote:

Generally the pipe is used to re-establish the curves exiting the waist and also the curves of both bouts.


If you have ever seen a Barbero guitar dropped on the floor and splintered into a hundred pieces, you would see the sides spring back toward their original position before bending. That is, unless you make a two laminate side glued together.



Stu -> RE: Template copy. (But smaller) (May 19 2020 15:03:34)

Ah Rob! Yes. I think that's a good idea. Use the inside form and do it that way. Wasn't thinking like that.Was transfixed on using the outside template.

Is the reason I want to do this valid?

That's side bending with the heat blanket underneath the side. Could it be done with the heat blanket on top of the side? Negating the need to make a smaller profile in the first place.

Or is that no good?



Stu -> RE: Template copy. (But smaller) (May 19 2020 15:10:52)

Pencil in a washer! I like a trick like that. Nice!
I'd kind of done that already with my calipers. Scoring a line.

Considered doing it that way like I had to for my inside mold. Bandsaw, sanding etc...But just the extra graft puts me off.. Time is route rare



JasonM -> RE: Template copy. (But smaller) (May 19 2020 16:02:04)

One of those rabbet bits with various bearing sizes is nice to have. Like the kind lmi sells for binding channels. Downside with these is that the bearings are expensive. but I’ve seen that Grizzly and other Import brands sell a bit with a general purpose bearing set for a decent price.

I made an offset template the hard way using CAD software. Actually drawing it is the easy part, u just need a way to get it out of the computer and on to the wood!



TomBeltran -> RE: Template copy. (But smaller) (May 19 2020 16:49:30)

Like RobF said. The best washers in my experience are called Fender Washers, where the OD is much larger than a standard washer.

Also, there is a good article that describes what RobF is stating about using a router. American Lutherie, #120, Winter 2014. Jayson Bowerman describes his process, complete with pictures. He starts with a half body shape template, and then makes a female template, by making an intermediate template, which then is used to make the final female template. He calls it expanding or shrinking a curve by a fixed offset. As to the router bit, he suggests using a Whiteside 1/2" diameter 3-flute straight flush trimming bit, with the follower bearing on top. Bowerman used shop made follower bearings, but you can use bearings sold by Whiteside.



Stu -> RE: Template copy. (But smaller) (May 19 2020 17:32:25)

Ha. 3d printer would be good for this no Jason?

Cheers for the Intel regarding that process Tim. Ill look into that.sounds ideal for what im doing.thanks



ernandez R -> RE: Template copy. (But smaller) (May 19 2020 18:47:47)

Stu,
I think you might be over thinking this and are trying to maintain a level of precision not required for this application.

Nothing wrong with trying to be precise but in the end it might drive you crazy and become a roadblock to success.

Save your precision for neck angle, cutting fret slots, and mounting your bridge.

Like it was mentioned up thread you you might need to do a final bending on the hot pipe. To be honest I made a couple bending machines and they get close enough for me so I don't need to touch them up on the pipe. The second side bender I built was for a parlor size and I did compensate for spring back by pulling the waist down about 7mm and pulling each end of the side wood in about 10mm. Nothing scientific, I just penciled in what looked about right. I screwed both sides together and cut them as one on the band saw. I'm making, or rather trying to make, Torres thin sides so they bend with ease in my clamshell form( I'm not using a traditional solera)

Dig around on the foro for a photo of Anders side bender; super simple and when I saw his I was able to make mine in less then two hours.
I'll get you a couple photos if I hobble out to the shop today.

Hope this helps.

HR

I forgot to add that I made my first three on the bending iron and only made the side bender because I had some vary special wood that I was afraid to bend in the pipe because I couldn't replace it if a screwed it up.



ernandez R -> RE: Template copy. (But smaller) (May 19 2020 19:03:28)

Found a photo on my phone 👍🏼
This is my parlor sazed bender.

Note the pins for indexing there are scribe marks on the inside if the metal strip. This way your waist bend is located precisely every time.

The clamp is disassembled so the arms are flipped around and provide the nessasery tension. Super simple and works quite well.like I mentioned this idea was stolen from Anders whilst he wasn't looking ;)

Took me one whole hour to make by not getting carried away with details and precision that don't matter.

It's double wide so I do both sides at once. I use two heat lamps and three on the full size bender

HR



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