Yhey are both for the same width iron....so, unless you got a chipbreaker from a Transitional Style plane.....a 5-1/4 chipbreaker should fit a No. 3 plane.....

problem comes from where the slot for the depth adjuster tab comes through....as they are different spacings.

 

Thanks, bandit571. I knew there had to be a difference in the placement of that slot.

How can I find out what the difference in the depth adjuster slot’s placement is? Is the 5-1/4’s slot higher or lower than the the No. 3’s?

 

How can I find out what the difference in the depth adjuster slot’s placement is? Is the 5-1/4’s slot higher or lower than the the No. 3’s?

The depth adjuster slot difference between the #5-1/4 and #3 is complicated, as there are at least two variations of the #5-1/4 (household jack and jr jack). Not to mention normal production variations during the many decades of mfg.

Does anybody know where you can get the exact dimensions of these chip breakers including distances from the top of the breaker to its yoke slot, its assembly screw hole and its lever cap screw slot?

Not that I found?
My challenge with a replacement 1-3/4" blade set is detailed in this thread. It has some comparison dimensions/images.

 

The depth adjuster slot difference between the #5-1/4 and #3 is complicated, as there are at least two variations of the #5-1/4 (household jack and jr jack). Not to mention normal production variations during the many decades of mfg.
Not that I found?
My challenge with a replacement 1-3/4" blade set is detailed in this thread. It has some comparison dimensions/images.

My reply appears below. Apologies.

 

CaptainKlutz: Your thread was very educational. Thank you. Did you ever resolve your blade set dilemma? What did you decide to do?

My 5-1/4 is definitely a Jr. Jack. The blade is stamped at the top:

[STANLEY]
5¼ P(12-025)
U.S.A.
​

The hyperkitten plane dating flowchart says it’s a Type 15, as does Joshua Farnsworth’s WoodAndShop typing/dating tool, but too many features don’t match for me to be comfortable with that result.

I’ll have to buy “vintage” 1-3/4" OEM cap irons until I find one that fits.

 

Don't have a Stanley Junior Jack ( Millers Falls No. 11 is the same as a No. 8 in width) , but,,,

One on the left is from a Stanley No. 31....one of the right, is from a Stanley No. 6c

Note the differences? these are the same width..at 2-3/8"
iron for the Stanley No. 31 has the April Patent date...No. 6c's iron has the clipped Box Stanley

 

Thanks for the visual, Bandit. That’s a huge difference in the placement of the depth adapter slot. It’s probably the same difference between the chip breakers for a No. 3 and a No. 5-1/4. It’s certainly enough of a discrepancy to explain why the blade assembly hangs outside the mouth 3/16" when it should be fully retracted.

 

A Stanley # 5-1/4 iron is 1-3/4" wide, same as the Stanley No. 3....as they take the same frog....and the same chip breaker...can't remember IF the 4 Square Junior Jack was different, of not....

Sargent Chipbreakers are just a wee bit off from a Stanley one...something about patents, I think?

 

Did you ever resolve your blade set dilemma? What did you decide to do?

Resolution was to use the Vertias replacement on older #3 plane where it fit properly.

I’ll have to buy “vintage” 1-3/4" OEM cap irons until I find one that fits.

Check out the folks at NH Plane parts or MJDtools. Both are antique tool brokers that sell Stanley plane parts. They should be able to get a chip breaker from compatible 5-1/4 plane. Both sell parts on evilbay, but can be contacted directly as well. This should avoid buying more than one....

FWIW - The difference in adjuster slot location between wood body transitional and steel body planes may be your issue? The 2" and wider transitional planes adjuster was ~1/4" difference; but I have never dug into difference on the narrower 1-3/4" wide blades found on; #21, #22, #23, or #25, sized transitional's? The problem could also be that a non-Stanley chip breaker was used. As Bandit mentioned, Sargent (and others) varied some plane size dimensions to avoid Stanley patents. Also; Antique hand planes are often FrankenPlanes, not fitting the type studies; as Stanley sold replacement parts for many decades.