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Gearing Down A Jet Drill

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toolroom

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#1
I have followed along in the forum long enough to safely ask this question. I own an older Jet bench drill it is a single phase ? 120 volt 1/2 horse 1725 rpm motor. The pulley speeds on it are 500, 900, 1600, & 2800. Yowza, can't do much with this, so I only use the 500 rpm.
I have tried in vain to find a larger pulley for it but 1) Jet remains ignorant. 2) The Farm stores carry step pulley's with little room to bore the ID out...so, Should I replace the motor with a lesser rpm range? Try to install a VFD?
What would you senior member do to bring the rpm's down to a workable range?
 

modela

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#2
I have followed along in the forum long enough to safely ask this question. I own an older Jet bench drill it is a single phase ? 120 volt 1/2 horse 1725 rpm motor. The pulley speeds on it are 500, 900, 1600, & 2800. Yowza, can't do much with this, so I only use the 500 rpm.
I have tried in vain to find a larger pulley for it but 1) Jet remains ignorant. 2) The Farm stores carry step pulley's with little room to bore the ID out...so, Should I replace the motor with a lesser rpm range? Try to install a VFD?
What would you senior member do to bring the rpm's down to a workable range?
I have an older Jet Drill. It was a few years old when the pulley broke and I had a hard time finding a replacement. Most ordinary drill presses do not gear down very low. Even a heavy duty one that I have really runs faster than I want. One thing I have done is to replace the motors with three phase and use a VFD on them to control the speed. Even if you don't have three phase you can get VFD units that are single phase that work with three phase motors. Three phase motors are actually quite reasonably priced on ebay.
 

ARKnack

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#3
On a Atlas drill press I have I installed a DC motor from a tread mill. I haven't used it a lot yet but so far I've been really happy with it. I don't like the speed control unit from the tread mill, so I just ordered a real DC speed control. Hope to try it out after it warms up a little. 10 degrees is too cold to be working in the barn. :confused 3:
 

uncle harry

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#4
I have followed along in the forum long enough to safely ask this question. I own an older Jet bench drill it is a single phase ? 120 volt 1/2 horse 1725 rpm motor. The pulley speeds on it are 500, 900, 1600, & 2800. Yowza, can't do much with this, so I only use the 500 rpm.
I have tried in vain to find a larger pulley for it but 1) Jet remains ignorant. 2) The Farm stores carry step pulley's with little room to bore the ID out...so, Should I replace the motor with a lesser rpm range? Try to install a VFD?
What would you senior member do to bring the rpm's down to a workable range?
Someone recently posted a project where he modified a band saw for normal as well as low speed to cut metal. He added a gear motor to the system using an overrunning clutch bearing and a jackshaft. When the gear motor was energized it engaged the overrunning clutch for low speed. When the high speed motor was energized the overrunning clutch freewheeled thus isolating the gear motor. This prohibits reversing your drill press but could work. Sorry I don't remember where this was posted. Two motors on a drill press would be rather clunky though.
 

Waterlooboy2hp

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#5
I have followed along in the forum long enough to safely ask this question. I own an older Jet bench drill it is a single phase ? 120 volt 1/2 horse 1725 rpm motor. The pulley speeds on it are 500, 900, 1600, & 2800. Yowza, can't do much with this, so I only use the 500 rpm.
I have tried in vain to find a larger pulley for it but 1) Jet remains ignorant. 2) The Farm stores carry step pulley's with little room to bore the ID out...so, Should I replace the motor with a lesser rpm range? Try to install a VFD?
What would you senior member do to bring the rpm's down to a workable range?
================================================

What model drill press, do you have ?? Should be easy enough to adapt the 3ed reducer pulley, from one of the Grizzly 12, or 16 speed models. I have bought replacement parts from them, to use on machines, that were not Grizzly--- John
 

toolroom

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#6
Arknack,
Would a VFD cause the motor to stall at low speeds? In other words...would I lose my torque?
 

modela

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#7
I am not sure about the torque. That would be a good one to find out.

There is also a question of how much torque a smaller drill can take. I have VFD units on a lathe of mine and two exhaust fans. The fans are probably lower torque units. I like the one on my lathe because it gives me the option of quickly changing cutting speeds. If you really want a lot of torque you might want to look at a larger drill. I don't think the jet I have would take a lot more torque with the chucks, pulleys, etc.
 

Chipper5783

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#8
There are a number of options. It sort of depends on what resources you have available and what you are hoping to accomplish. It is pretty easy to spend more on fixing up a machine than it would cost to purchase a machine that would do many of the things you want. Certainly, you can put a variable speed drive on (3 phase or DC). The torque will drop off (if you slow it way down, it will drop of quite a bit - mainly because of the difficulty in cooling it).

If you go with a 6 pole motor (1150 rpm), that is physically quite a bit larger - but that would get you down to about 350 rpm (and full torque capability). You could make your own larger pulley (which still gives you plenty of torque) - how much room do you have? You could go with a DC motor & drive - often these motors are fairly high speed, so you get variable speed - but you may need an intermediate shaft to get some decent torque back. You could go with a VFD and a 3 phase motor - recommend a 6 pole motor and/or upsizing the motor to preseve torque at the low end (a very nice solution, but if you pay store price for the components it will exceed the price of a good used HD drill press). You could set up an intermediate shaft - which works great, lots of speed selections, good torque (until that wee little belt slips - unless you go to a cog belt as the second belt), but a little fussy to set up and make guards for.

I had the same problem as you (too fast a drill press). I had an 11" Rockwell drill press (1/3 HP). I put a 1/2 HP DC motor on it. It was constantly popping the over current protection.

I was able to obtain a good HD Rockwell at auction for $375. It came with a 3 phase, 6 pole motor (1150 rpm) and quite a large step pulley on the spindle. I solved the 3 phase requirement with a cast off VFD (meaning old, free and still works, albiet noisy). I then spend quite a few hours engaged in "recreational chipping" to fit the drive in a nice enclosure, make up a pretty little mount for said enclosure, wire in the 3-wire stop/start to the drive - the result is great, but I was starting with something that was well along in achieving a slow drilling speed.

I no longer have that 11" DP. I got a nice 14", which is sort of fast, but combined with the 17" the bases are covered.

Your original question was, to ask what others here would do. First of all, just use the machine as is - sure it is a bit fast, but does it really cause you problems? At worst you may get a bit more practice sharpening drill bits.
Second, I would keep an eye out for lower speed motors (single phase or 3 phase). 3rd, I'd keep an eye out for a HD drill press (running a light duty drill press at low speed, is still a light weight drill press). 4th, I'd start thinking about setting up an intermediate shaft (picking up materials etc. on the cheap) - after a few years of "First", if "second" or "3rd" had not worked out and I found there was problems - only then would I modify the drill press.

Let us know what you work out.

DSC02370.JPG DSCF2220.JPG
 

brino

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#9
What are you starting with? Does it have 2 belts or just one?
Since you mentioned only 4 speeds I assume it has only two four-step pulleys and just one belt.

Many drill presses have 3 pulleys and 2 belts. There is an intermediate shaft between the motor pulley and the spindle pulley. It allows you to have more speed choices.
Here's my King KC122FC:
belts.jpg
and the speed chart:
speeds.jpg

It is a very simple arrangement, there is an anchor hole in the head, a crank with two pins on opposite sides of opposite ends, another 4-step pulley with bearings to mount it to the top shaft.

upload_2016-1-19_21-49-33.png
from here:
http://www.manualslib.com/manual/87282/King-Canada-Kc-122fc.html#manual

Once you figure out the belt sizes required it could give you both more low-end RPM and more high-end for small holes.

I believe I saw a thread here where someone added an intermediate shaft to their drill press.
If I can find it I will post back here.

-brino
 
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Uglydog

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#10
Brino,
Thanks for the break down pic.
It appears that the center pulley is on a pivoting lever #14. Thus, you still only need the one belt tensioning mechanism.
How does the pivoting lever mount? Is it just a hole with a pin? Bearings? Anything to keep it aligned?
Thanks for the pic!!

Daryl
MN
 

toolroom

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#11
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

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#12
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.
 

brino

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#13
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
 

francist

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#15
image.png Was it this one?

-frank
 

brino

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#16
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
 

toolroom

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#17
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
 

brino

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#18
Toolroom,

I am glad I could help!

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

-brino
 

toolroom

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#19
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
 

berniehernandez

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#20
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.
 

brino

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#21
I will try, and see if it will work
Hi toolroom,

Did you make any progress on this?
I would certainly want two bearings in the idler pulley to resist any twist...or one very thick one.

-brino
 

toolroom

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#22
brino,
No progress. The motor has begun to make growling noises, and I see that I MUST go with a three phase 220V motor, ot scrap the unit and buy a really cheap Chinese one from Harbor Freight. Either $60.00 Chinese vs. $2000/$3000.00 for a new motor with a vfd.
Can't afford that yet, which is a shame as the Jet is a heavy cast unit and has a good spindle on it, but you can't drill holes with an anchor
Toolroom
 

BobSchu

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#25

Dunc1

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#26
I have followed along in the forum long enough to safely ask this question. I own an older Jet bench drill it is a single phase ? 120 volt 1/2 horse 1725 rpm motor. The pulley speeds on it are 500, 900, 1600, & 2800. Yowza, can't do much with this, so I only use the 500 rpm.
I have tried in vain to find a larger pulley for it but 1) Jet remains ignorant. 2) The Farm stores carry step pulley's with little room to bore the ID out...so, Should I replace the motor with a lesser rpm range? Try to install a VFD?
What would you senior member do to bring the rpm's down to a workable range?
Check out the Google reprints of old Popular Mechanics (PM) & Popular Science magazines (One eg is PM Mar 42). Another idea: (not my original idea but I could not locate a source). Remount the motor upside down on an auxiliary plate along with a ball bearing arbor. Place a small (2-2 1/2 inch diameter pulley) on the motor shaft and use it to drive, via another v-belt, a 10 or 12 inch diameter pulley on the bottom of the arbor. Place the original cone pulley on the other end of the arbor & have it drive the original pulley on the spindle.
Here's another concept:
 

Smithdoor

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#27
This is way I slow down my mill
Add a center pulley wend I need low speed
Note: The center pulley is very large and was shop made.
Use a larger small pulley on the center pulley so the belt dose not slip
Slow speed is 139 RPM with 1725 motor I have 2 speed motor and at 1140 the it is 92 RPM

Dave
 

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