Also according to andy at Torch and fike:
The SILVA head tube mill for 1-1/4” steerers is no. 058 with mill no. 406ALE which has 36.95mm o.d. and 20.5mm bore.
I will email Park, their website still says their reaming kit comes with a 1 1/4 reamer, but I doubt it.
This is not my area of expertise: Which reams fit on which reamers? Is there any sort of cross compatibility? Which reamer do most builders have?
I’m in the process in building a gravel bike so I will switch to EC37. I will be call Coco with an order soon and will get one. Since I don’t have a fork yet for it it’s worth a try.
Reamers are the biggest issue.
I am a park tool reamer guy.
Chatted with Andy at Park tools about the HT reamer kit: HTR-1 Head Tube Reaming and Facing Set | Park Tool
Unfortunately the “36.8 mm pilot (part #766)” is just a bushing, and they said that Park never made a 37mm reamer for it.
Andy is also a big fan of metal/custom bikes, so he said he will bring it up at the next product meeting and chat with their machinist to see if it’s possible to reduce the EC44 reamer. 
I wouldn’t hold your breath. Andy is a nice guy, but there’s only one opinion that matters at park tool, and it’s not Calvin’s either
My logic says no, but my heart says maybe 
For a big company like Park Tools, its probably not financially worth supporting ~100 frame builders with a reamer. But also for a big company like Park, making 20 prototype/custom reamers is water off a duck’s back.
Many people who are passionate about cycling are also passionate about custom/handmade frames, so I am optimistic that if they can help, they will try.
I can’t remember the tap mfg that Park works with, but they are in Wisconsin somewhere. maybe it would be possible to work around the indifference at the top.
In order to get T47 off the ground, we invested in taps. Our goal was only to supply taps until Park or one of the other manufacturers took it over. I believe Park was the first, and now there are a number of T47 tap suppliers. I’d rather not have to do it again with 37 mm reamers. We had taps made by Cheboygan Tap, https://www.cheboygantap.com/ They are in Wisconsin, but I don’t know if they do work for Park. I think one reason that Cheboygan may have been willing to do T47 taps for us is that PMW had a history of getting custom and semi-custom taps already. We were a well established customer. I can speak to the quality from Cheboygan, it’s first rate.
Maybe if we had a number (?) of builders willing to commit $$ for reamers, we could get a batch made.
I’ll put up money for a reamer. The paragon t47 taps are way better than anything available now and a reamer from the same supplier is money well spent.
I would be in for a set. Can never have enough tools
I’d be in for one as well.
I’d take reamers. I like the slimmer EC37 headtube. Getting Radavist or other media to support it might help customers move away from the oversized, chunky stuff that they are so used to now. Headset makers need to also get on board - one or two lower end ones. White Industry are wonderful but pricey for some.
PS - I love T47 and use it on pretty much everything that isn’t lugged.
I chatted with the Canadian distro of Cyclus this morning and they’d be able to get some cutters in June… but then I’d have to get the handle and cone as well. Even at wholesale I’d be looking at a few hundred bucks.
All that to say, if there’s going to be a PMW reamer that works with the Park handle - count me in.
Thank you Mark and @Coco_PMW for sending me one of these!! I haven’t re-mitered my TT and DT yet because I’d like to figure out a reamer before I commit on this frame. But it looks so good and I’d be very keen to go in on a reamer that would work for the park tool set.
Looking good.
Thanks for starting this conversation Daniel. I dislike 44mm headtubes on steel bikes generally - just adds weight. So when I could source US-made carbon forks from Allied, I decided to create my own headtube/headset design to mate to the 1-1/4” tapered steerer.
To make sourcing headtube stock easy, I designed around 1.5”x0.035” tubing. Which I guess makes my headset EC36.3. The lower cup fits a Cane Creek 47mm bearing, and the skirt is tapered to fit up to the Allied fork crown (which has an integrated crown race - headset also plays nicely with Enve forks with a crown race installed). Upper bearing is 41mm, I buy an IS41 upper headset and the cup matches nicely to the cover.
I have been building with this system for four years - the main reasons I still use 44mm headtubes sometimes is either a customer wants to have a headset that matches hubs/BB, or we are doing internal routing.
Holesaw being 1.5” means the same for headtube and BSA BB, which makes life simple.
If we are looking to resurrect an old standard that has limited current availability, then perhaps considering a new standard for ease of tube sourcing is worth considering? Wanted to share my experience anyway.
Thanks, Rob.
If there is no reamer for it yet, how are y’all trying this? What am I missing?
Also, could you use some motor honing tool instead? I have used one to smooth the interior of my seat tube and it worked like a charm, I know they don’t remove a lot of material but… dunno… wanted to throw it in the mix.
Talking about:
Flex hones are great tools, but only for removing tenths of thousands of an inch, and to improve surface finish. They also tend to bell-mouth a bore at the entrance and exit.
Ceeway should be able to get the needed reamer. I have always gotten my Cyclus tools,thrpugh them or a Europe based mail order shop.
We’re getting quotes, but haven’t heard anything yet. Stay tuned!
Thanks Mark and team!
