209 "Spool Tension Knob" thread size... What is it SUPPOSED to be?

[GrowleyMonster]

I notice that a M7 x 0.75 tap fits into the threaded hole of the left side plate into which the bearing cap or "Spool Tension Knob" if you prefer, screws in, and is not difficult to get that tap in there but it is definitely a proper fit. But the knob itself fits VERY TIGHT into an M7 x 0.75mm die. I do mean really tight. Tight enough that I hesitated before actually forcing it with tools. Usually my fingers alone would be strong enough for this. Now a M7.5 x 0.75 die fits comfortably on the cap's threads, but a M7.5 x 0,75mm tap simply will not go into the corresponding threaded hole of the side plate. That indicates to me that the correct thread size is somewhere between M7 and M7.5, but there does not seem to be any such tap and die made. Likewise there is no imperial tap and die in between there, either. The thread pitch is definitely in the neighborhood of .75mm, and I am not ruling out 32tpi or 36tpi, .75mm metric pitch being right about 34tpi. The Penn reel designs from that era are a mish mash of metric and Imperial size screws and threaded holes, so the way forward is not absolutely clear. I wonder if this is actually a totally oddball size, with custom made tooling rather than customary diameters and thread pitch?

If I force a 7mm die on the bearing cap, with tools, I can get it but it is definitely cutting the threads deeper. When I then screw the cap into the side plate, the fit is definitely slightly looser, though it is unnoticeable with the spring in there. Now, I know that I CAN use the M7 tap, but I want to be sure that I SHOULD, before I DO. Obviously what I am aiming to do is to make a couple of 209 left side plates with very strong adjustable mag brakes without giving up the clicker. Yes, I know, it's a $15 reel, so why bother. The fact that they can be had for chimp change is exactly why I am goofing around with the 209, because they are expendable and I have so many of them. No Squidders or Jigmasters will be harmed during the making of this movie. When I know what I am doing, I will operate on some nicer reels, and meanwhile hopefully I will have some very nice modified 209's in my stable.

If there were such a thing as a 9/32 - 34 tpi tap and die set, it would probably fit perfectly. 5/16 is too big and I tried 5/16 - 32 and also 5/16 - 36 tools, no cigar. 19/64? That is a hair over 7.5mm an so it would be too big. 37/128? Surely not a thing. But it would be a good size. However I want to believe that if not a common size, at least it is not an unheard of size. If nobody has any ideas, I will go with the M7 x 0.75mm tap and die.

Yes, I can simply use an OEM bearing cap, and I will, and only have to worry about the hole. But while prototyping I want to check the hole position with a center punch screwed into the threads, as well as an interference fit center punch through the frame post holes, to verify my measurements and template for drilling the holes that absolutely need to match the original locations.

[oldmanjoe]

 I believe it is 9/32 x32     the tap and die is available 
https://alantani.com/index.php/topic,36478.15.html

[GrowleyMonster]

I believe it is 9/32 x32     the tap and die is available 
https://alantani.com/index.php/topic,36478.15.html

Ah. Thanks for that. I will look into it. The size will definitely fit but I didn't see one that size anywhere.

[oldmanjoe]

https://www.amazon.com/Aceteel-Machine-Right-Hand-Thread/dp/B09VZNCJ6K

https://www.amazon.com/s?k=9%2F32+x32+die&i=tools&ref=nb_sb_noss

 There are other vendor , just google seperate tap then die for better results .

[GrowleyMonster]

Thanks. I have dealt with Aceteel before and would avoid them if possible. McMaster has taps only, uncoated HSS, very pricey, but delivery Monday instead of next month. Found UK sellers for both taps and dies but their target market seems to be builders of miniature brass steam engines and I suspect they are just high carbon steel. Looks like a US seller, Vermont Gage, has a HSS die, price okayish, delivers before the end of the month. So I popped for that die, and the McMaster tap. I really should practice my fine single point threading and get better at that. It will save me a lot of money.

https://www.mcmaster.com/catalog/130/2917/2595A631
https://www.amazon.com/32-13-HSS-Round-Die/dp/B007PL2PTG

[oldmanjoe]

 I wish that I had all the change gears for my lathe and a couple thread bitts .  Taps and dies can get pricey  for being used only one time or two .

[GrowleyMonster]

I wish that I had all the change gears for my lathe and a couple thread bitts .  Taps and dies can get pricey  for being used only one time or two .

Yeah I feel ya. It's not so bad, when high precision isnt needed and it is a common size usually included in Home Depot or Harbor Fright tap and die kits. They are cheap and they usually last a good while if you aren't threading a lot of hard stainless steel and you are careful not to break off the taps in a hole. But it sucks when you have to wait for a month on an overpriced mediocre quality tap or die from China or India and it is an oddball size that you might never use again.

If your lathe is a benchtop type, you can probably get by pretty good with 3D printed change gears. They are cheap to buy and not too hard to print. That's what I use though I would still RATHER have metal change gears. One thing I like about my Chinese 7x12 is my feed screw is 16 tpi, so that makes it simple to make standard Imperial threads. Well, relatively simple, anyway. My handwheels are all set up for inches, too. Did I ever mention how I hate metric? No?