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MDF machines well but it is not as stable as ply wood
the nice thing about this discussion is that there are many ways to do this. We all seem to develop methods that work for each individual. As a machinist and tool maker my discipline is secure fixturing .
What you want to do is have a way to make a process reproducible . So controlling critical aspect of the guitar goes without saying.
what are they ?
Symmetry
Neck block location
keeping sides true.
I use high grade balitic birch plywood , and early used many materials MDF being one of them , and if you use spreaders the MDF will flex , and don't get them wet.
Variable molds have issues but again do what works for you. Make an informed decision on need and affordability.
this is my method I use this as it removes an internal spreader and secures the location of the sides should you have to remove the rim.
https://www.youtube.com/watch?v=FcM3GErOI_A

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John Hall
blues creek guitars
Authorized CF Martin Repair
Co President of ASIA
You Don't know what you don't know until you know it

Mine require a socket and ratchet, so not super convenient, but I like the accuracy of the joints and low weight.

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formerly known around here as burbank
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http://www.patfosterguitars.com

FWIW, my $0.02 -
It's a bit more work initially, but I dowel and screw extra blocks top and bottom at neck and tail.
Lets me clamp the blocks in good and solid, and keeps everything square.
Just remove then after blocks are glued.



But I'm using these 'universal' spreaders now.

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The name catgut is confusing. There are two explanations for the mix up.

Catgut is an abbreviation of the word cattle gut. Gut strings are made from sheep or goat intestines, in the past even from horse, mule or donkey intestines.

Otherwise it could be from the word kitgut or kitstring. Kit meant fiddle, not kitten.

Thanks everyone for the input. It's been really helpful for me!

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I do the extra end mold block like Colin on a few of my molds, works great. Hey, I like those universal spreaders!

Pat

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Pat

I like John Halls video about screwing the neck block to the mold.
Simple and seems to be very effective.
I'm stealing that one.

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Say what you do, Do what you say.

Do you also screw in the tail? You mentioned not needing a spreader.


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John

I like your mold for weight and efficient use of materials. What are the extra holes between the spacers for?

Ed M

Definitely NOT "A." I bought one and regretted it immediately.

Home made ply from here on out.

D type.

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https://www.instagram.com/fostinoguitars/
https://www.facebook.com/PuraVidaUkuleles/

I think this is my favorite so far. I love those spreaders. Oh yeah, and the bench clutter. Just enough room for the job and no more. Makes me feel at home

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Hutch

Get the heck off the couch and go build a guitar!!!!

John Arnold's mold....I'd love to understand the wood dimensions (material thickness, spreader height, considerations of height so's there is room left for kerfing clamps). The one dimension I have is for two inches for rim width, so I know the spreaders are two inches wide as well.

Thanks!

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Peter Havriluk