bushing templates from negative part

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Forum topic by swarfrat posted 02-09-2016 09:29 PM 557 views 0 times favorited 2 replies Add to Favorites Watch
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39 posts in 874 days

02-09-2016 09:29 PM

This seems like a basic skill, but I just can’t seem to wrap my head around it.

I’d like to make a template from a negative part, and I’d rather use a bushing than a template bit. BUT… I’m making my template from the actual part. It’s the neck pocket of an electric guitar body. It’s a neck pocket of unknown specs, and I’d like it to be an exact fit.

So: Template goes down on existing body. Use flush trim bit to follow existing neck pocket – gets exact duplicate (zero offset). From this point on – I can only make the offset greater, when what I need is a negative offset. Can I do this without making a 1) flush trim negative pattern—> 2) positive pattern with bushing offset—>3) negative pattern with correct bushing offset?

2 replies so far

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615 posts in 1372 days

#1 posted 02-09-2016 10:28 PM

It took me a while to understand your question, but I think I have it. My guess is that you just need a type of router bit that you don’t currently have.

Clamp your template material to the guitar body and use the flush trim bit like you had planned to copy the profile of the opening. Then move the template to the new body and use a PATTERN BIT to rout out the new cavity. The flush trim bit has the bearing at the end to follow the cavity. The pattern bit has the bearing at the top near the shank to follow the template as you make the new cavity.

Note that the diameter of the two bits you use will determine just how accurately you can duplicate the corners of the opening. A smaller diameter will give a more accurate turn at the corner, but it will come at the cost of more passes to hog out all of the waste in the cavity. You will probably have to do some fine tuning of the corners to get a perfect fit. Perhaps you can make the adjustments on the end of the neck piece.

Note added when I reread your post. I now see that you mentioned a template bit. I missed that since I haven’t used that terminology. Your eventual desire to somehow increase the size of the template could be done, but it seems very awkward and prone to unecessary complication. Just buy a pattern bit and you have your problem solved perfectly.

Here’s a picture.

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39 posts in 874 days

#2 posted 02-10-2016 12:09 AM

I guess you did answer my question. I was trying to cross from a template made from flush trim / pattern bits to one for a bushing without a bunch of wasted patterns. But I think the bushing diameter alone is probably enough to rule that route out. At any rate – copying the existing neck pocket sounds like flush trim / pattern is the way to go.

However, I also have a freehand traced positive pattern which I also need to route (for the body I’m making), and that’s probably a good candidate for bushings and a large straight cutting bit.

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