Gearing Down A Jet Drill

Wow, all this information to digest. Thank you all. It is a Jet 13-R, with one belt and two four step pulley's. Really a heavy cast foot and table. Bought it from the widow across the street after her husband died of brain cancer for $100. Myself being on fixed income... it would be a hardship to sink hundreds of dollars into it now...BUT looking at the intermediate shaft has its rewards. I may lose the cover, as the plastic housing is rather long and skinny, or perhaps severely modified. Thank you for all your help.
 
Arknack,
Would a VFD cause the motor to stall at low speeds? In other words...would I lose my torque?
Don't know for sure. I have seen where people complain about loosing torque and others say they are great. I suspect a lot has to do with the quality of the vfd. Good units have torque boost on them. I have a couple vfd units but mainly use them to generate 3 phase at 60 hz. My mill has a veri-drive on it. The other is on a carbide grinder.

From a cost stand point dc is cheaper. I just bought. speed control for $90. It's a Baldor/ABB unit and has regenerative breaking on it. Not sure about reverse. Treadmill motors are around 1hp. If this works out well, I'm planning on converting my 9" SB lathe to dc.
 
Hi Daryl,

Thus, you still only need the one belt tensioning mechanism.
Absolutely correct.

How does the pivoting lever mount? Is it just a hole with a pin? Bearings? Anything to keep it aligned?

It looks like just a tube fixed to the head frame. The tube needs to be long enough to resist the bottom pin twisting out of a vertical orientation. The bottom pin on one end of the crank simple drops into the tube with no bearings on that end. The bottom pin is only a 4-5 inches long. No bearing required, as it is really only used to adjust the intermediate shaft and pulley along an arc. The tension of the two belts in opposing directions is all the holds it.

You want to be sure that the pulley steps align well. Adding simple spacer washers to the bottom pin could lift the crank arm up.

Thanks for the pic!!
Your welcome. I was trying to save a thousand words!

-brino
 
Was it this one?
Yes, that's it! Thanks Frank.
I don't know how I missed it in my search, I used many of the same terms....oh well.

Here's the direct link:
http://www.hobby-machinist.com/threads/slowing-down-my-drill-press.33007/

I specifically remembered the pictures in post #12:
http://www.hobby-machinist.com/threads/slowing-down-my-drill-press.33007/#post-280592
because that machine already had a mounting hole for the intermediate shaft crank arm.

Thanks again Frank!

-brino
 
Thanks Brino,
I took the pulley's off the Jet and cleaned everything up the post is hollow with a cast cap, which I made a plug in which to install the center shaft when it arrives from Grizzly. Got all the parts ordered so I hope it all works out. My concern is that I have a four step pulley and I think the Grizzly is a 5 step pulley, we'll wait and see.
toolroom
 
Toolroom,

I am glad I could help!

I'd appreciate some photos when you get your parts in.

-brino
 
brino,
The Grizzly parts arrived late evening, I'm scratching my head on this one. The schematic shows two bearings, however the pulley depth would only accept one, with lateral play. I will try, and see if it will work, but I'm skeptical at higher speeds.
toolroom
 
I swapped the 1/2 hp motor for a 3/4 hp in my drill press. I did this mod so I would not have to changes belt positions too often. I can adjust from 66 RPM's to 1677 RPM's with just the turn of a pot, that's with the belt position set for 750 RPM. It does have a torque boost setting that works great. If I intend to use at low RPM for many holes, then I will change the belt so the motor can cool itself. I should have stuck with 120v rather than going to 220v. The conversion was about 250$. It was more than I paid for the drill press. It was worth it, having very low rpm range also.
 
Back
Top