DP speeds

[Skip C]

I am new to drill presses. I recently bought a big, old heavy Henry Corp DP (unfortuneately the co is out of biz and I can't find a manual). I know how to figure the drill speeds but I don't know whether I measure the inside diameter of the pulley (where the belt lays) or the outside diameter.

If anyone can lead me to a manual it would be much appreciated. The unit is in fine shape. It looks like it was built to take abuse!

Thanks, Skip

[LCHIEN]

a pair of calipers will do the job.


(photo from Rockler.com)

To measure the OD put the belt on and open the jaws to measure across the diameter.

To measure the ID remove the belt and use the jaws (they're skinny) to measure the inner diameter getting the jaws between the flanges (the calipers will have to be parallel to the pulley).

Take the diameter as the average of the ID and OD. For all practical purposes, however, just using the ratio of the outer diameter of pulley1 to the outer diameter of pulley2 will probably be close enough.

Don't worry about too much accuracy, the motor speed will be probably low by 5% or more and +/-20% is probably OK for selecting the correct speed.

this might be interesting reading:
http://www.bt3central.com/showthread...875#post180875

[Skip C]

Thanks, Loring!

[LCHIEN]

that was fast. You might reread it I added some more thinking and a link.
I first thought you were asking how to measure but I then saw you didn't know which to use.

[Joe DeFazio]

To measure the OD put the belt on and open the jaws to measure across the diameter.

To measure the ID remove the belt and use the jaws (they're skinny) to measure the inner diameter getting the jaws between the flanges (the calipers will have to be parallel to the pulley).

Take the diameter as the average of the ID and OD. For all practical purposes, however, just using the ratio of the outer diameter of pulley1 to the outer diameter of pulley2 will probably be close enough.

Don't worry about too much accuracy, the motor speed will be probably low by 5% or more and +/-20% is probably OK for selecting the correct speed.

Or you can borrow or buy a cheap photo tachometer, which I find to be quite handy, and the existence of which I learned about from Loring on this forum. Attach a single dot of reflective tape to your chuck or spindle, aim the laser, and read out the exact speed. You can easily make your own chart of pulley combinations, so it's a one-time job with the photo-tachometer.

Here's an example of a cheap one (which I am not specifically recommending; it's just an example):

http://www.ebay.com/itm/New-Digital-...item43a91e6743

Congrats on the old iron; it's great to have a heavily built tool like that. Does it has a pulley cover? Some of the older DP's don't. If it doesn't, I hope that you will take the time to make one, for safety's sake.

Joe

[LCHIEN]

yes, a photo tachometer is a much better way, I assumed the OP didn't have one and would not be willing to order and wait for one.
Here's my original post describing the photo tach.
http://www.bt3central.com/showthread...oto+tachometer