So much depends on the size of the peghead (or peg box), and the overall size of the dulcimer.
Choose pegs that don't look too big or too small for the instrument. Use your eye. 👁

My 29" vsl langspil was equipped with Wittner internally geared viola pegs:

It's an imposing instrument and violin pegs would have looked silly on it.

I personally go smaller rather than larger in my selection of pegs, Nate.  I like 1/2 size violin pegs on most of my builds.  I've always felt like many of those pre-Revival dulcimers had 'way too large of pegs for the size of the tuning head and instrument.  Probably, as you suggest, because the players had trouble adjusting hand whittled pegs with small heads and short shafts.  With well fitting pegs, and experience,  the issue is moot.  People have been playing small violins since the 16th century.

My two Holly Leaf pattern dulcimers shown here have different size pegs.  The larger one has full size -- 4/4 - violin pegs and the smaller one has either 3/4 or 1/2 violin pegs, I can't remember which.  When I made that smaller scroll head, the full sized pegs just looked out of place -- too big for the size of the head, so I got smaller ones.  The same taper reamer that I have works for all sizes of commercial pegs from 1/8 violin up  to full size cello and viola IIRC.

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Seems that Cello pegs or a good wrench are both way better options than making my own. Thanks
Nate

You can buy pegs designed for viola or cello. Bigger than violin ones.

You are forgiven, my son.... go forth and dulcimorize!

Yep!  Sorry John; Credit where credit is due!  YOU made those Lyre pegs and the wrench, not Dan Cox,  and a darn fine job you did, too.  Mea culpa....

Ken, that looks like the wrench I made for you, to go with the pegs I made at the same time.

Nate -- here's an idea I got from Michael King, in England, my Lyre plan supplier -- a tuning key for wooden pegs.  Dan Cox made this one for me when he made the oversize pegs for my Oberflacht Anglo-Saxon Lyre.    You can approach the peg from almost any angle and the 4" or so length gives you plenty of leverage.  

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Thanks for the info. I have seen some chinese ones on ebay for 15 dollars each for the reamer or shaver, a couple times less. I assume theyre less precisely made or less durable than nice ones. Still, if premade pegs only cost 1.50 that would take a lot of pegs to be worth getting the kit. The main reason I might want to make my own is that I find pegs with a very large flat head to be much more comfortable than the smaller ones on a violin.
Nate

Nate, the "pencil sharpeners" you speak of are called violin peg shapers and used to be very expensive, as Ken said.  They're typically used along with tapered reamers, which also were very expensive.  Used together, they make the forming of pegs and their accompanying mounting holes easy to deal with.  

Do you mean the peg shaver?  If you're making pegs from scratch they are so much less work than trying to whittle a taper with a pocket knife.  They used to be very expensive but you can get them now for around $30 that will create several different tapers to match the taper of the peg hole reamer that you have to make a perfect fit. 

You can also make your own peg shaver with a block of HARD wood and the peghole reamer you already have.

Personally I use standard commercial violin tuning pegs, Unless you're trying to duplicate the pegs of a particular pre-Revival builder, they are just fine... inexpensive and available in a variety of sizes from 1/8 to 4/4 violin plus sizes for cello and viola. They can be found in a variety of woods and knob designs.  I've been paying under $1.50 per peg for the sizes I use.

What do y'all think of the pencil sharpeners designed for friction pegs? Are these a good method for creating tuners, or just an artetfact of a tradition?

I recently replaced  friction tuners on a Bill Davis 5 string dulcimer, I had to put some bushings in as the Perfection Plantary Tuners were to small, So glad I did, it is so easy to tune and holds tuning well.

Thanks everybody!

Yes, the manufacturers offer different sizes.  Just select ones that are the proper size.  I know of three manufacturers-- Knilling (Perfection pegs), Wittner (Finetune pegs), and Pegheds, which are made in South Carolina!

Or, the geared tuners in viola size. Violin sized tuners might only look natural on smaller dulcimers. Check the sizes of the tuners and the instrument.

I agree with John,  If you want that traditional look go with Perfection geared violin pegs.  Simple to install.

I have had good results using Perfection geared violin pegs by Knilling.  The tuning action is very smooth for those suffering from arthritis or other hand conditions.  Any violin repairperson should be able to install them in a dulcimer.  They look amazingly like wooden violin pegs.  They are available from several online dealers.

A friend of mine recently had nice ukulele geared tuners put on a Jeffreys instrument and was happy with the result. 

I recently purchased an A.W. Jeffreys dulcimer from 1967 (I think - serial # 993). Although I wanted a very traditional style instrument, I am having trouble adjusting to the friction pegs. I'm thinking of replacing them with geared tuning pegs, as used by some violinists (not guitar-style tuners). Would welcome any thoughts or advice on doing so!