Jack throat/mouth clearance problems

[edmund]

Hi Everyone,
I thought I'd see if someone could come up with some helpful suggestions for the following problem I'm having with an old Record 5 1/2 jack plane. When I'm using a square edged iron, in order to get the cutting edge parallel with the sole of the plane I have to use a fair amount of lateral adjustment. This ends up with the cutting edge at one side being quite close to the front edge of the mouth such that the shavings jam the gap quite quickly. I've tried moved the frog back but it doesn't make any difference. I've also moved the chip breaker back to allow more visible cutting edge. Something in the set up is obviously not square but I can't readily identify what. So, what's the best way to solve the problem? Should I just offset the frog to compensate?
Thanks, E

 

[Alf]

Some things to check that leap to mind:
Blade edge square?
Frog square to the mouth?
Mouth not square?
Frog bedding skewed?

or

Just use a cambered blade. :wink:

Although if the shavings are jamming the gap even with the frog back that might indicate the cap iron not bedding properly on the blade too...

Cheers, Alf

N.B. Please note I'm hopeless at working out plane problems in the abstract, so best wait for someone else to point out the fatal flaws in my reasoning before proceeding...

 

[mudman]

Could be that the chipbreaker is skewed slightly on the blad. Perhaps it twisted slightly when the screw was tightened?
Also possible is that the front of the chipbreaker isn't at 90 degrees to the sides?
Wouldn't this effectively skew the blade slightly when put into the plane?

Mind you, I could be way off here and bow to more knowledgeable people.

 

[David C]

Edmund,

Alf is right. This is the classic skewed frog syndrome.

For your plane to have an even mouth, there is a unique position for the frog. I refer to the twist of the frog relative to the plane body. viewed from above.

When refixing the frog, you need to test fix, set a balanced shaving, and then examine the parallelism of the mouth. The frog is then twisted a little in the desired direction and you start again.

Getting this spot on can either be easy or take many attempts. The blade C/B etc having to be removed every time you wish to adjust frog. Fine twist adjustments can be made by loosening one screw and crabwalking the frog with the central adjuster. either forward or backwards.

A balanced shaving must be set every time before examining the condition of the mouth, (Space tho which the shaving comes).

After finishing this job it is advisable to do a little sole flattening as the new tensions on the frog screws, (NOT TOO TIGHT), may alter sole flatness near the throat.

I think this is reasonably well described in my first book page 30.

good luck,
David Charlesworth

 

[edmund]

Thanks for the advice. Always good to have such esteemed persons as Mr C dropping in - will keep me on my toes . I've made the adjustments to the frog and its all much better now (and everything looks much squarer, which I always like to see).

I hadn't paid too much attention to setting up the frog as I had been using a cambered blade for heavy duty planing. I'd only recently decided to put in the time to sharpen up the rather badly treated original crucible steel blade. I was quite surprised as it cuts much better than I'd anticipated.

E

 

[bugbear]

I have a Record #5 1/2 where there is a 1.2mm difference in height between the 2 frog mounting points... (!!)

And I have to use A LOT of lateral adjustment too.

BugBear (been meaning to get a ME friend to mill the error off, but I have "some other" planes to use in the meantime, so the tuit hasn't appeared)