The Hegner Scroll Saw

George CarlsonBuild Log, News, Tools

Hegner 25V

The Hegner Scroll Saw

We’ve been watching school and government auctions for items to equip The MakerBarn.  We have gotten some great deals on high quality tables, cabinets, and chairs.  On one of the auctions sites, I noticed a school district down near Victoria was auctioning a Multimax scroll saw and a Delta bandsaw.  Both looked fairly rough, but I placed some bids just to see how it went.  Victoria is a long drive so I hoped by bids would be fruitful.

I won both auctions.  This meant driving 300 miles, but with luck, it would be well worth it.

The Delta bandsaw was fairly recent vintage.  It had been the victim of a student brawl and had been knocked over.  But the upper and lower trunions were broken, but everything else survived.  A few used parts off eBay and some new tires, and the bandsaw tuned up beautifully.

The scroll saw had been sitting outside for quite some time.  It is a Hegner Multimax 25V, which is a very high quality scroll saw with a 25” deep throat and a variable speed motor.  New, these saws sell for about $2,000.  At some time in the past the motor controller had failed.  The school had wired the motor direct, which meant it was being run at hyper-fast speed.  This torn-up the link between the motor eccentric and the lower arm as well as a few other things.  I machined a new link from aluminum, then went to work on the motor.  The controller had a bad IC, which I was able to replace. The motor and controller are rather unusual.  The motor is a permanent capacitor split phase induction motor with a tachometer output.  The tach output is used as a feedback to the motor controller to assure constant speed.  The output voltage of the magnetic pickup was very low.  So I use a tiny audio transformer to increase the voltage.  After adjusting a few component values in the controller (sometimes it’s helpful to have an electronics design background) the motor ran fine.  The last item to repair was the cast iron flywheel/eccentric that attached to the front of the motor.  It was being held by some material that looked a lot like JB Weld.  This was not a good sign.  In the abuse that followed the rewiring of the motor, the flywheel must have come a bit loose.  The hammering of the eccentric, due to the high speed, enlarged the hole in the soft cast iron flywheel.  I put the flywheel in the lathe, trued it up, and bored the mounting hole for a steel sleeve.  Then I machined a precise steel sleeve and pressed it in the flywheel.  A bit of work, but the motor, flywheel and link were now working perfectly.  I replaced a couple of additional parts and now have a saw that runs like new.  Altogether, the parts cost about $75, but that’s not too bad for such a high-end machine.  Oh, by the way, the auction price for the scroll saw was $27.50, so we came out pretty well.