The Dale Maley Family Web Site

Subtitle

Repairing Porter Cable scroll saw PCB370SS

I bought this scroll saw back in 2012 and have put a lot of hours on it.


When I first got it, the plastic knob that you tighten the top of the blade broke.  I replaced it with a steel one from McMaster-Carr.  That solved that problem.  The part number from McMaster-Carr is 92581A430.


A few months ago, I noticed the plastic knob below the table that is supposed to turn and lock the table in place no longer worked.  If I just leaned on the RH side of the table, it easily slid out of position.


Today I decided to tackle it and figure out why the table would no longer stay in place.


The design has a 1/4" threaded steel shaft inserted into a plastic knob.  The plastic broke inside the knob, so you can no longer tighten the table.



Manual

The exploded view in the manual did not help me to understand what failed.  The plastic knob and inserted steel shaft is PN 2XZP in the exploded diagram.


Broken Plastic knob

Cross-Section of original knob design

New Design

I thought I would thread a new piece of 1/4" steel rod and use some nuts to secure a new Hickory knob to the shaft.  I measured and the threads are 22.5 TPI which screw into the scroll saw.   These are not English UNC, FNC, or M6 Metric.  I decided to just use the same steel shaft, but thread 1/4" UNC or coarse thread on the other end so I could bolt it to my new Hickory nut.  I turned the new Hickory knob on my 1939 Montgomery Wards wood lathe.  I epoxied the steel shaft to the Hickory knob....and tightened up the nuts on each end as well.


My New Design

closing thoughts

Hopefully I have now broken and fixed all the original parts on the scroll saw that did not have a robust design...........and my saw works fine for many more years !!!!!!!!!!