Doughbro - Posted - 05/26/2009:  16:25:57

I recently bought a 1977 OMI roundneck dobro and I think I need to upgrade the cone. The original cone doesn't appear to be spun (no lines).

I have 2 questions.

1. Does someone sell a 10 1/2" replacement cone for a Dobro, or is it easy enough to buy one that's 10 9/16" and trim 1/16".

2. How would I know if I also need a new spider bridge. The old one has legs that are almost flat and I don't know if it will work with a new cone.


I will be doing the labor myself. Any recommendations or comments will be appreciated. Thanks, Doughbro

Edited by - Doughbro on 05/26/2009 19:32:31

jaykellogg - Posted - 05/26/2009:  19:52:35

I did what you are about to do. I bought a Beard cone from Janet Davis Music. I also replaced the nut and bridge inserts. I filed down the parting line on the spider and levelled the legs per Paul Beards instructional video. Janet Davis sells both 10½ and 10 9/16 cones and you have a choice of Beard or Quarterman. To check the spider, I held it to a window pane and checked that all 8 legs touch at the same time. I did not replace the screw between the bridge and cone and I wished I had. For about 80¢ I think it is a good idea.

W. Jay Kellogg

Slideman1939 - Posted - 05/27/2009:  08:16:37

The Beard cone and the Quarterman cone are both spun from the same type aluminum alloy so the sound will be similar from whatever supplier you select. Selling the old cone: surprise--some folks like the tinny echo sound of an OMI stamped cone.It yields a particular old time sound that is not currently fashionable but is salable. If it is in good condition you may get $15 or $20 for it as an E Bay sale. The older pre-war LUGGED cones are also favored on some conversions and are much harder to find--selling at $70 - $75 on the used parts market. They have a sweet "Brother Oswald" tone but lesser volume. Simply a different alloy from a different time period. One man's trash is another man's treasure.In the 1970's and half into the 1980's the O.M.I. standard cone was stamped and a spun cone was a $12 extra option. How times have changed.

Doughbro - Posted - 05/27/2009:  15:07:06

I put a new maple/ebony saddle in the old cone/spider and Slideman, I see what you mean about it having a neat old timey sound.

I need to add another question about spiders. This OMI has the offset bridge, with a one piece saddle and the screw behind the saddle.

Question 3. If I replace my spider with a non-offset bridge, won't the intonation be off? Wasn't the scale set up for a bridge that's shifted forward? Thanks fellas

Slideman1939 - Posted - 05/27/2009:  20:07:08

Like yourself, Doughbro, I ALSO own a 1977 O.M.I. (squareneck/ carved sandblasted Model 66) BUT I have a standard spider. My understanding was the offset spider was developed PRE war and carried over later to post war OMI as an option. The purpose was some of the licensees who were also authorized to make dobros had clearence problems in the handstrap area because the coverplate wasn't high enough--so the offset spider was developed. Perhaps a luthier reader will answer. I was always taught that a 25 inch scale means 12 and 1/2 inches from the nut to the 12 th fret and then 12 and 1/2 inches from 12th fret to the bridge (center of the spider). So IF ONE HAS an OFFSET SPIDER does that mean that either the instrument length where the neck joins the body was altered ?? OR the fingerboard fret positions were altered ??? Logic would seem to indicate a person with an offset spider ( which changes the scale) would require different fingerboard/fret markers--to make it intone properly to various bar positions. IMPLYING that you have to replace that spider ONLY with another new offset spider because a standard spider would throw your scale and bar positions into sour notes. Help....somebody.....what's the answer on offset spiders

Doughbro - Posted - 05/30/2009:  06:01:57

On the recommendation of Jay, I purchased a 10 1/2" Quarterman cone from Janet Davis and they we're very knowledgable about Resos and nice to work with. I also spoke with the Paul Beard folks and was told that my old offset spider would be just fine with the new cone.

The scale on my 77 OMI is 24 1/2" and measures 12 1/4" to the 12th fret. Logic tells me that my frets were laid out for an offset spider and that a standard spider would throw the intonation way off. Slideman, I'd be interested to know what the scale length on your 77 model is, and maybe we can get to the bottom of this thing.

jaykellogg - Posted - 05/31/2009:  03:22:08

Setup is all important. Are you replacing the nut and bridge inserts as well? You will need to level the legs of the spider. If you do not know how to do that I can tell you. The bridge inserts should be a tight fit. After the spider legs are level it should sit on the cone and all eight legs should touch at the same time (without the screw installed. Also the cone should sit in its recess and not tip or wiggle when lightly touched. I had to re route the recess on my guitar. I also had to redrill the coverplate screws as it wasn't centered on the cone.

Let us know how it works out for you.

W. Jay Kellogg