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Doug Short Red Special Build Thread

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Doug Short Red Special Build Thread

Postby Doug » Sun Feb 05, 2017 4:52 am

Introduction
Hello guys. I thought that it was high time that I started a detailed build thread for my full size Red Special replica. My first and only guitar build to date was a 3/4 scale RS replica that started off as a relatively straightforward BMG Mini May conversion project and morphed into a complete build that used only the truss rod from the original guitar. :lol: You can find details of this on this thread:

The '1975' Red Special
viewtopic.php?f=26&t=1347

You've no doubt seen my research on Brian's original Red Special which details how I believe that he and Harold arrived at the form of the instrument:

Body Design:
viewtopic.php?f=25&t=1357

Neck Design:
Posted on RSBA forum only so far. Headstock here:
viewtopic.php?f=25&t=1356

Pickguard Design:
viewtopic.php?f=25&t=1359

Internal Structure Design:
viewtopic.php?f=25&t=1371

I am trying my best to turn this theoretical knowledge into tangible results, but working shifts and having two young children doesn't leave much time left for resource intensive hobbies such as building and designing guitars. :roll:

I have had an interest in making a Red Special since I first got into Queen when I was about 14 years old; a family member lent me A Night At The Opera and A Day At The Races. Need I say more? ;)

I have had an interest in 3D CAD design and CNC manufacture for some years and only in the last couple of years have 'desktop' (or garage floor) CNC machines become accessible to the hobbyist. Also, my handicraft skills aren't very good. ;)

What better way to combine two interests but to design a Red Special replica in a 3D CAD software package and buy, assemble and operate my own CNC machine to make it?

As for playing guitar - sadly I am an average rhythm guitar player, a bedroom rocker, an amateur plank spanker having never mastered a musical instrument of any sort... Grade 2 piano at primary/elementary school, clarinet lessons and a third rate wind band at high/secondary school and then I nicked a school friend's guitar and tried to play Paint It Black by the Rolling Stones. 25 years later I'm still learning very slowly. No matter, I will surely spend my days trying to become a better lead guitar player. Thankfully, I have a decent ear for music. More than likely it will be blues that I default to.

Health warning/disclaimer: I believe in detail because that's where I think the quality builds rise above the average ones so, time permitting, the material in this topic will contain more build specific details than I have mentioned elsewhere. I reserve the right to edit my posts many times to tweak the information and correct errors so don't be surprised if you see multiple edits on any post. I won't repeat any design detail I have mentioned in other threads, I'll just hyperlink to them.

Doug
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Re: Doug Short Red Special Build Thread

Postby Doug » Sun Feb 05, 2017 4:56 am

Blockboard Preparation
I have been making my own softwood core, plywood faced blockboard over the last few days in preparation for receiving a new industrial quality HF cutting spindle for my Stepcraft 2/840 CNC machine on 25th January. Despite many teething troubles with my CNC machine, it is pretty much good to go now. Therefore the availability of blockboard became the critical path instead of CNC machine operability.

This has been more difficult than I anticipated due to not having any decent woodworking power tools such as a bench saw, planer/thicknesser, etc. CNC machines are wonderful things but you need the basic kit to prepare the workpieces for cutting.

For the actual build, I will use Spruce tonewood bracing strips for the softwood core sourced from Exotic Hardwoods/Timberline in Kent:

http://www.exotichardwoods.co.uk/

and the same plywood but with the best sections selected. I will get this assembled by a more skilled woodworker who has a good selection of tools. For the the test cuts, all the timber is rough: some of the plywood sections are warped, the core is low quality timber (see below) and the oak is the least linear grain sections of the 3 meter long length I ordered. For the test cut blockboard I have taken care to ensure that all the internal butt joints are square and have selected the sections with the smallest and fewest knots/flaws but I was not overly bothered about the external appearance.

I sourced my plywood from Travis Perkins (Plywood Hardwood Throughout Ply 2440 x 1220 x 3.6 mm) at £17.55 per sheet ex VAT:

http://www.travisperkins.co.uk/Plywood- ... E/p/767330

I sourced the smooth planed timber from the dreaded "big sheds", B&Q in this case at £16.15 per pack of ten:

http://www.diy.com/departments/smooth-p ... 521_BQ.prd

I sourced the PAR European oak from British Hardwoods:

http://www.britishhardwoods.co.uk/plane ... imber.html

I selected Gorilla brand wood glue:

http://uk.gorillaglue.com/gorilla-wood-glue

The pack of ten 12 x 44 x 2100 mm smooth planed softwood turned out to be way off (for my purposes): more like 11.3 x 42 x 2100 mm. The width and length isn't so much of a problem - the thickness is. I was hoping that it would be over spec: something like 12.3 mm to make up the difference between 3/4" (19 mm) and two sheets of plywood (3.35 x 2 = 6.7 mm). As it happens, the finished blockboard measures about 18.5 mm maximum. The oak was fairly precisely planed to 19 x 121 x 3000 mm but is over thickness so I will have to sand this down before starting the CNC toolpath.

I decided to make my workpieces 18 x 16 x 3/4" (457 x 406 x 19 mm) which would allow about an inch overlap for the guitar body which measures 15 3/4" x 14" (400 x 356 mm).

I smothered everything in the glue (I HATE glue), clamped it sideways with two Irwin 18" Quick-Clamps and weighted it all down with bricks, paint pots, cartons of car shampoo, car screen wash. Why is it that you can't find smallish heavy things when you need them? :roll: I expected to just go behind my shed and find lots of building bricks, but that's the downside of being ordered and tidy. There is no spare junk when you need it.

The bottom section was left clamped and weighted overnight. The top section is curing now and will be ready tomorrow (24 January 2017).

Doug
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Last edited by Doug on Sun Feb 05, 2017 1:56 pm, edited 2 times in total.
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Re: Doug Short Red Special Build Thread

Postby Doug » Sun Feb 05, 2017 4:58 am

Sticking with the wood theme, the first Red Special piece I cut using my new CNC machine is the small oak insert for the top section to which the knife edge plate is attached.

To achieve this, I used a section of the European oak wood stock in a two sided cut. I first drilled two 4 mm holes along the Y axis right through the stock and inserted two 4 mm stainless steel dowel pins to ensure that the stock did not move in the X or Y axes when flipped over. I built 4 mm supports onto the sides and stuck the stock down to a 12 mm MDF spoil board on the bed of the machine. I used a 4 mm diameter, 4 flute carbide end mill with 25 mm long flutes. The machine is capable of running at 3,000 mm/min. feed rate but I initially selected conservative 1,500 mm/min. X/Y feed rate and 375 mm/min. Z plunge rate based on factors input to GWizard Feeds & Speeds Calculator for a 90% fine/10% rough finish.

http://www.cnccookbook.com/FeedSpeedsCa ... izard.html

I have tweaked this again following setup activity for future cuts to 2,000 mm/min largely based on the fact that the machine generated dust so fine it was basically talcum powder when it should really be generating chips. X/Y feed rate and a lower Z plunge rate of around 120 mm/min. Retract heights are set at 2.0 mm to ensure plenty of clearance when the bit travels between regions. I initially selected a conservative rapid (unloaded) travel rate of 1,500 mm/min. but have since increased this to 2,250 mm/min (75%).

I designed a small (1/16") rebate into the bottom half leaving a ledge/overhang. This is to allow the full range of permissible movement on the tremolo block. I don't know whether the original guitar has this feature but I presume not since it is not illustrated in the early design sketches.

After producing design sketches and reviewing Greg Fryer's hardware drawings, I decided that height at which the tremolo retaining bolts sat meant that there was no requirement to cut channels into the lower section of the guitar body to accommodate them. Hence the channels in my block are 3/8" (9.5 mm) high, or exactly half the height of the small oak insert.

I have elected to drill all the pilot holes for the wood screws in the guitar by hand. I have not had very positive early experiences of using the CNC machine to drill - possibly because my spindle holder plate was initially not levelled ('trammed') relative to the machine bed. That is sorted now although other experienced Stepcraft users recommend drilling pilot holes before using a carbide end mill to bore out the holes. I might review this decision and incorporate pilot holes into my CAD design if I gain enough confidence that things are not going to go wrong.

As normal with routing processes, the cut corners are rounded off to be equal to the radius of the router bit used, so in my case they are 2 mm radius because I used a 4 mm diameter router bit. Where these need to be square (on the knife edge and bolt retainer block rebates) I will have to use a wood chisel or file to open them out.
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Last edited by Doug on Sun Feb 05, 2017 5:07 am, edited 1 time in total.
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Re: Doug Short Red Special Build Thread

Postby Doug » Sun Feb 05, 2017 5:00 am

Tremolo Retaining Bar
After examining Greg Fryer's design drawings:

https://fryerguitars.wordpress.com/pick ... -hardware/

I decided to "Go My Own Way" on the tremolo bolt retainer and just keep it simple so I made it from a length of 2 3/8" x 1/2" x 1/4" mild steel bar. If Brian didn't do it that way, I don't know why not. :lol:

I have been lucky enough to get a nice, accurately made set of custom hardware, so thankfully no requirement to make that although I do fancy my chances at making a roller bridge with the CNC machine just for a challenge.

The bar is just drilled and tapped to a 1/4" imperial fine thread. Er, that's it. From my own scale design sketch (attached), I reckoned that the bar sits 13/32" in the top section and 3/32" in the lower section. Best guess based on Brian's sketch I think.

I made a slight pig's ear of grinding the channel into the hex bolt head. I might try that again nearer assembly time.

Doug
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Last edited by Doug on Sun Feb 05, 2017 2:06 pm, edited 1 time in total.
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Re: Doug Short Red Special Build Thread

Postby Doug » Sun Feb 05, 2017 5:02 am

My new HF spindle arrived on 25th January for the Stepcraft 2/840 CNC machine. It's small but an industrial quality item so should not now be a weak point in the system. This is how the machine looks now: here is a short (2 minute or so) video of me jog testing it. This is just to make sure that all the axes move freely because it weighs 1.5 kg, much more than the original one I had. I haven't powered it up because I sent the kettle style power cord back with the last faulty spindle. Sigh.

http://www.youtube.com/watch?v=j5hxx007h6Y

And 5m 42s worth of footage of it cutting the small oak insert (31 January 2017):

http://www.youtube.com/watch?v=gGzD4v3TRUI

Further toolpath calculations show that I will need to cut away 2.0 mm per pass to get the rough cut path under an hour in the case of the upper body section. The finishing passes add about another 40-45 minutes. I have made up some blockboard offcuts to do simple up and down milling tests.

Doug
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Re: Doug Short Red Special Build Thread

Postby Doug » Sun Feb 05, 2017 5:09 am

Here is a 9 minute video of some test 'ploughing' cuts removing 2.0 mm depth per pass (four passes in total to 8.0 mm) on 3.6 mm plywood (hardwood throughout) faced softwood strips (simulated blockboard). The job was 100% successful AFAIC, which means that the longest roughing toolpath on the guitar body sections will be less than an hour. See later posts for actual body section cuts.

Stock details
Two pieces of softwood PAR timber 315 x 44 mm x 18 mm glued to an offcut of 3.6 mm thick plywood (actual thickness 3.35 mm on digital calipers) to yield a cuttable stock volume measuring 315 x 88 x 21 mm.

- StoneyCNC industrial HF spindle
- 4 mm diameter four flute solid carbide flat nosed end mill, 25 mm flute length
- Feed rate: 2,000 mm/min.
- Plunge rate: 120 mm/min.
- Rotation speed: 20,000 rpm.
- Depth per pass: 2.00 mm.

Total cut time approximately 9 minutes.

http://www.youtube.com/watch?v=-q3i-t8KXJg

I don't see how to embed a YouTube video on this forum; the [youtube][/youtube] tag doesn't work.

Regards.

Doug
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Re: Doug Short Red Special Build Thread

Postby Doug » Sun Feb 05, 2017 5:10 am

This short video is the machine cutting the insert out of 3.6 mm thick plywood for the upper body blockboard section. Same parameters as before but with two cuts of 1.675 mm depth per pass each.

As you can see, the machine makes short work of this job which took me ages using a Dremel professional multitool with the Dremel small circular saw attachment. I cut four sheets in maybe half an hour including the preparation and removal of the sheet, zeroing on the next sheet, etc. These more precisely cut and unwarped sheets are destined for Andrew Nisbet (you don't know him but I thought I might as well use his actual name) who is going to make up the blockboard sections with oak and the expensive spruce tonewood for my actual build.

http://www.youtube.com/watch?v=pQF6vuWfg4A

If anybody is interested, I have appended the G Code I used for this job to let you see how simple it is. I just made up the file manually in this case. The text in parentheses are just comments. The machine ignores these.

Regards.

Doug

%
(FILENAME: Upper Section Plywood Insert 3 Axis Cut Job.nc)
(TOOL/MILL,0.1,0.05,0.000,0)
G21
(STOCK/BLOCK, 406.4, 457.2, 3.35, 406.4, 457.2, 1.675)
(TOOL/MILL,4.0000,2.00000,25.000,0.0)
M6 T1
G0X0.0000Y0.0000Z2.0000
G0X58.625Y226.6000
G1Z-1.6750 F120.0
G1F2000.0
Y-139.2875
X-58.625
Y226.6000
G1F120.0
Z2.0000

G0X58.625
G1Z-3.3500 F120.0
G1F2000.0
Y-139.2875
X-58.625
Y226.6000
G1F120.0
Z2.0000

G0X0.0000Y0.0000

(END)
(OF PROGRAM)
Last edited by Doug on Fri Feb 17, 2017 7:32 am, edited 1 time in total.
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Re: Doug Short Red Special Build Thread

Postby Doug » Sun Feb 05, 2017 5:13 am

1 hour 44 mins and nearly 33,000 lines of G Code later, I appear to have a Red Special guitar body lower section! :o

I'm going to score it 96.4% because the plywood cap came off the cuboid that the potentiometer/capacitor plate rests on. Now I think I see why Brian put a washer on top of it!

I'm very pleased with how the Stepcraft CNC machine and its spindle performed. It can't have lost one single step. Some pics attached and link to YouTube video below:

http://www.youtube.com/watch?v=mlzdxmOpnp8

There are three non-contiguous parts which I had to join together because the camera is limited to 4 GB videos at a time. The total toolpath time was 1 hour 44 minutes. I think this is plenty to give you a flavour of how it all works.

Basically there's about an hour of roughing passes. I think that's pretty much all you see here so it's a bit repetitive. Then the toolpath moves to finishing passes which you don't see (parallel which moves across the X axis taking off the bottom of the pockets, waterline which goes round the outlines taking off 1.00 mm per pass and pencil cleanup which goes around the outline and takes off a little bit)

Doug
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