Reply To: haveing trouble setting frog to allow plain iro to be set
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Late to the party, my fate in life.
Hey, after lots of diagnostics and fussing over the last year my bench planes are working pretty well. One problem with frog adjustment is seeing a clear line against which to adjust the front of the frog.
For three out of four of my planes, the mouths were not square across the body. Moreover, one had (apparently from the factory) problems inside the mouth. Perhaps some of my experience will be of benefit to you.
I used bluing across the sole in front and back of the mouth. Then tested a square across front and back from both sides. Fortunately, the two sides agreed in each case indicating that the sides were parallel. Therefore lines were scribed in the bluing to indicate the smallest possible mouth with square front and back edges.
A 6” second cut flat file with safe edges was the appointed weapon, and in each case squared the opening quickly. At this point the edges of the opening had been filed vertically. On the front, it’s easy to open up the angle and approximate what had been there previously.
Fitting and adjusting the frog to the back edge is harder. One plane had a Bedrock style frog and there was an odd bump on one side of the body next to the bottom of the frog. It was hard to find but required correction. Other lesser oddities existed on the remaining planes.
An upside-down Hock blade works effectively to test the frog to body interface. Hock because the top of the blade is straight across, and it’s a thick rigid blade. BTW, this applies to Bailey pattern frogs equally.
First partially tighten the frog screws – allowing just enough slack that you can adjust it with a tack hammer or very light ball-pein. Set the blade in place (cutting edge up for protection) and slide it down. It should sit tightly on the frog and while sticking into the mouth. Then tap the frog and blade back until the blade also engages the mouth (without lifting from the frog).
I’m going to offend the world here, but hang with me.
The proper position of the frog is when the full plane of the blade is in contact with the bearing surfaces of the frog and the back edge of the mouth. The back edge in this case will be only the inner edge (meaning the mouth is cut vertically or nearly so).
In other words, support for the blade will not extend through the sole. Not to worry. Even if the plane of the frog is extended by the edge of the mouth, the blade’s bevel prevents it from being supported by the mouth itself.
Most people speak of moving the frog forward In order to avoid tear out, and don’t accept that there’s a correct position relative to the mouth. They may be right.
I believe, however, that frogs are adjustable for one reason. Back when Bailey was perfecting his design, it’s wasn’t cost effective to accurately mill the plane body to hold the blade. Similarly, it wasn’t cost effective to mate a frog and body to fit together in a single position while accurately positioning the blade. In other words, the adjustments were designed to overcome poor tolerances – not to tune for tearout.
This would explain why it’s hard to tune the mouth despite the later addition of frog adjuster screws. One still must remove the irons, loosen the frog screws, adjust the frog, check it’s square, tighten screws, replace irons and test whether the adjustment works.
Yes it’s possble to close the mouth, but this is cumbersome and not something many people regularly adjust. And cap iron adjustment does a great job of tuning for tear-out.
So just adjust the frog to mate the squared back edge of the mouth and you’ll be good.
- This reply was modified 6 years, 8 months ago by Richard Guggemos.