Reply by MrUnix

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Posted on Delta Jointer

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7388 posts in 2593 days

#1 posted 10-10-2017 07:11 AM

First off… if you have a 2.5” motor pulley and a 7” cutter head pulley – I can tell you right now that it’s not spinning anywhere near fast enough regardless of what motor you have. You don’t say what jointer or motor you do have… but for the ubiquitous Delta 37-205 and 37-207 jointers, the recommended cutter head speed is ~4200 rpm. Are you sure you didn’t mean a 7” motor pulley and a 2.5 inch cutter head pulley?

Anyway… cutter head speed (in rpm) = motor speed (in rpm) * pulley ratio

So for a 1725 rpm motor w/2.5” pulley and 7” arbor pulley, the cutter would be spinning at 616 rpm
A 3450 rpm motor would be twice that (1232 rpm) – both WAY too slow.

With the pulley sizes reversed (7” pulley on the motor), the cutter head would be spinning at 4,830 rpm when using a 1725 rpm motor – a little faster than recommend, but much better than the reverse.

For reference, the 37-205/37-207 jointer manual recommends a 1725 rpm motor, with a 7” motor pulley, and the jointer ships with a 2.75” arbor pulley.

You can play with motor speeds and pulley sizes using the arbor speed calculator over at the VintageMachinery site.


-- Brad in FL - In Dog I trust... everything else is questionable

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