Fret bender/straightener

Construction and repair of Classical Guitar and related instruments
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Alexandru Marian
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Fret bender/straightener

Post by Alexandru Marian » Sun Dec 31, 2017 9:50 am

Luthier supply will hate me for this, but since there was Christmas...

Not a must have, I have lived for 10 years hammering coiled frets on flat boards but with harder wires (I now use steel) they can be more of a pain to seat nicely.

The thing can be made for less than 10$ in a few minutes. I bought a set of 8 bearings for roller skates from Decathlon. They are 22mm od, 8mm id. Then you need three 8mm bolts and nuts and 6 standard washers. For in between the bearings you need another 3 washers of about 0.7-0.8mm. I had some brass pieces around here at 1mm and they were easy to thin on a grinder. Then you need a block of hardwood at least 50mm wide and 20 thick. The harder the better. The adjustment top screw is a big thread bolt for wood with a 4mm hex top and 4mm "stem". Here I used oak and a 4mm bit and some vaseline is perfect for cutting the threads in the wood but with harder you might need a 4.5 or even 5mm hole else the wood will crack. If you want it perfect, use a block of aluminium and tap a standard thread.

For the bottom bearings drill the base as to have some 1-2mm of space in between them. The top bearing low position should be a couple mm below the top of the lower bearings. After you drill this third hole, go up several mm and drill a 4th then file the resulting corners. Check that the bolt can travel up and down.

For adjustment simply back off the adjustment screw, hold the screw high up and tighten it enough that it is very snug. Feed some wire, it should be loose. Work the adjustment in small increments until it lowers to the correct tension.

The beauty is that it works for both bending and straightening depending on how you feed the wire. In the video I straighten, for bending simply turn the wire around.


Youtube

JRomano
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Re: Fret bender/straightener

Post by JRomano » Sun Dec 31, 2017 9:59 am

That is a very cool bit of DIY. I have often looked at the Stew Mac catalog, and have seen lots of what appear to useful items. But I think the cost is often prohibitively high, especially since some of these things might be used just a couple of times. Nicely done.

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Alexandru Marian
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Re: Fret bender/straightener

Post by Alexandru Marian » Sun Dec 31, 2017 10:38 am

I have a lot of money put into commercial jigs and gadgets for which I didn't have time/machinery/skills/patience to do myself. But this one is simply too simple not to. And if the:
-base is made from alu
-instead of hw store bolts use real axles which are only threaded where needed
-bearings are high quality with very precisely made chamfers, it should impossible to be improved. It would still cost less than what you can buy without spending a lot of time

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geoff-bristol
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Re: Fret bender/straightener

Post by geoff-bristol » Sun Dec 31, 2017 11:43 pm

Nice - very elegant ! will make one. Bearings are so cheap ( why, amazes me, as they are such precision things )
If you buy hex head bolts - rather than Hex head machine screws - the bolts are not threaded at the head - same price, snugger fit in an 8mm hole.
Maybe thats what you used ?

I modified my bandsaw guides with a very similar set up !

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Brian McCombs
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Re: Fret bender/straightener

Post by Brian McCombs » Mon Jan 01, 2018 1:43 am

LOVE IT!!

Here I'll share what I call my Pabst Blue Ribbon inspired fret radius remover. If you should ever need one in a pinch.

Strategic rotation of the bar in my left hand determines the radius....I like them flat because I glue them in. Bridge the wire across the gap in the bolts... rotate the bar until desired bend is achieved. Tighten up the clamp, grab the end of the fret wire sticking out there with pliers and yank it through. The tang of the wire is captured within the bolt threads like a channel. In no way does it hurt the fretwire. Stupid but effective.
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Alexandru Marian
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Re: Fret bender/straightener

Post by Alexandru Marian » Mon Jan 01, 2018 8:03 am

Happy New Year!

Geoff, good catch about the bolts. I used full thread because I already had them. Even so, the vertical play is small and they lock reasonably aligned. I mentioned precise axles because my first attempt involved some old bearings I had in the junk pile. I found 3 pieces of 5/8 - 1/4 which were a heaven fit with worn router bits. A bit of bearing Loctite would have secured them perfectly but I dropped it since ordering a 4th bearing online just before 1-1 wouldn't have worked. Decathlon is 5 mins away from me.

Brian, if it works, it works! While I am very open to try the quickest impros, this never occurred to me. I tried to massage them with a hammer in a wide slot, or lift and pull ends, or hammer, to poor results so I gave up. Reminds me when i (reluctantly) accepted a refret for a friend. Pulled the frets to find they were glued in a 1mm slot. Had to clamp-glue each down, there was so much cursing. Filling slots and recutting would have been equally annoying. Every time I swear I am not taking repairs no matter how much pity the owner inspires me.

Anyway i just finished fretting a guitar with the straightened pieces and although there is always self deluding involved, they seemed to go in with less fussing than before. I use a self made (Pb) lead hammer. After going back and extra smashing 3 or 4 high spots, it looks like a perfect fret job that does not require any leveling let alone recrowning. Can't find any high spot with the triangle.

SteveL123
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Re: Fret bender/straightener

Post by SteveL123 » Mon Jan 01, 2018 2:32 pm

Hi Alexandru, Nice job and design! I've read and saw a few youtube videos where they say for conventional (softer) frets, you want the bend that the coils are shipped it when installing them, i.e. they should not be straightened first. This is not true for stainless frets? Do you still hammer the stainless frets in or do you use a press? It seems to me that a press set up properly will do a better job than hammering. What do you think?

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Alexandru Marian
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Re: Fret bender/straightener

Post by Alexandru Marian » Mon Jan 01, 2018 4:29 pm

If by soft you mean the "classical" alloy with 12% nickel, that stuff is so noodly it really doesn't matter. You can literally tie it into knots with your bare hands. I used it on just one guitar and throw away the rest, never again. A professional player can return for a recrown in just 6 months, no thanks. Even the much stiffer 18% can wear fast with intensive use so a few years ago I switched to EVo wire which is again harder and stiffer. It went OK on new boards but when refretting, if the wood is soft or too chewed in the slot you can have a hard time making it seat. Even on a new guitar it can be troublesome beyond the 12th. A few times I couldn't make them go in fully no matter how much I dared to hammer so in the end had to do a serious amount of filing and recrowning.

Stainless is again tougher than evo but I didn't notice any extra issues hammering it compared to evo. it is definitely a pain to cut and file so now I do must of this work on a grinder, including the bevels.

I have pressed only once, with evo. Worked very nicely but since I had an improvised press made from a screw clamp, it took a long while compared to hammering.

Last job with hammered straightened evo went really well with zero sweat and cursing beyond the 12th, and this is a very wide 8 string guitar! I am very pleased.

Either hammering or pressing, you are exerting an amount of force/stress on the metal, and on the wood from the barbs. Some of this energy needs to straighten a curved wire, or at least hold it in tension with the barbs. So I can't imagine any benefit from using curved wire.

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geoff-bristol
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Re: Fret bender/straightener

Post by geoff-bristol » Tue Jan 02, 2018 12:41 am

I find it helps to straighten fret wire if I press in the upper frets ( above 14 ) with the board on. I generally do this with a good g clamp with leather on the pad and caul inside ( pre-fitted when building the top ) Having a dead flat fret helps there. 12 and 13 will hammer ok onto the block area - but up to the soundhole is a little tender !

Fretting' - is a good name for fitting frets - it always seems to be a problem ! - not helped by lack of consistancy from one batch of the same wire to the next !
I find a good saw to match a supply of wire - only to find when I buy in more of the same its not the same ! I have had to devise ways to ease slots ever so slightly !
It is I suppose something one must just learn to do - and one only gets the chance on each guitar you make ! Change of wood - then it all different agian !

SteveL123
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Re: Fret bender/straightener

Post by SteveL123 » Tue Jan 02, 2018 1:06 am

When I said pressing the frets in, I envisioned this being done before gluing the fret board to the neck. Any problems doing that?

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Alexandru Marian
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Re: Fret bender/straightener

Post by Alexandru Marian » Fri Jan 05, 2018 8:10 pm

I wouldn't do it without a trussrod and non-water based glue for attachment to the neck.

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