My vintage 1HP Delta Drill Press was working normally until last week it will
not rotate but hums when I turned on the switch on. I removed the motor from the
DP and powered up. It still will not rotate but starts to hum again. I rotate
the pulley manually, it begins to rotate and speed up normally and the humming
stop. I switch off the motor, before it stops completely I switch the motor on
and it speeds up normally. I did another test: I turn the switch on, as it
starts humming, than I rotate opposite direction, it speeds up and again it
stops humming. Can I assume the start capacitor is bad? If, so where can, I buy
a replacement. The Capacitor is an old one; Manufacture Name": SF??? MIKE" Type
H, 210 259 MFD. 115VAC"
Thanks for your help.
Check the yellow pages for any motor repair shop in your area. You
need to match the MFD and voltage ratings of the capacitor for
performance reasons and the physical size for obvious reasons, so I'd
advise taking the old cap with you when you go. Note that the voltage
rating on the replacement can be higher than the original, but should
not be lower.
You could also do a Google search for online sources:
If the link below is inoperative, do a search on (without the quotes)
"motor start capacitor" and click on the "shopping" link.
Here's one that seems to be compatible with the electrical
characteristics of your old capacitor, don't know about the physical
On Sun, 21 Sep 2008 23:23:43 -0500, Tom Veatch wrote:
Hi fellow Kansan, I brought this DP from KC to the Bay area in 06'. I did a
search in the Internet and could not find an exact specification as marked on
the old capacitor. Yellow page here in the SF Bay areas are practically useless
that is why I posted here looking for help. The above link still does not give
me the detail I need to buy the "exact or acceptable" capacitor. I hate to burn
up the motor since I took so much effort to moved it two thousand miles away.
Go to http://www.mcmaster.com /
Left side of the page, enter "capacitor" in the search box
Third one down in the "AC Motor Start Capacitors", "110-125 VAC
Capicitors" is part number 7245K112.
The electrical characteristics are correct for use as a replacement
for your old capacitor, "Type H, 210 259 MFD. 115VAC". Whether the
physical dimensions are correct is another question. If it will fit
within the "bump" on the motor, go for it.
I've ordered from McMaster-Carr many times. As I recall, the "Company
Name" field is not a required field, so if you don't want to make up a
company name, just do as I do and leave it blank. They aren't like
Grainger which does require a business name.
Take it from an electric motor repairman - disconnect the capacitor and
short the two wires together. If the capacitor is bad, the motor will start
(it may start slowly, but it will start). If the motor still won't start,
the problem is with the starting switch inside the motor.
If the capacitor is bad, you can replace it with anything near the same mfd
value. A general ballpark for a 115 volt motor is 400 mfd per horsepower, so
a 1/4 hp motor would be 100 mfd. For a 1/2 hp motor the value would be 200
mfd. If you get too far away from the original value, you will lose starting
torque in the motor, but for a drill press, that's not usually significant.
Did exactly what you suggested. Yes, it start. I knew it was the capacitor, cuz
the switch was solid and sound. Thanks.
The motor is 1HP (original Delta), Type H 216 - 259 MFD 115 VAC.
From McMaster (Carr page 925) :
PN# 7245K114 AC Motor-Start Capacitor 340-552 Rating, 1-7/16" Case Diameter,
PN# 7245K112 AC Motor-Start Capacitor 216-389 Rating, 1-7/16" Case Diameter,
Look like PN# 7245K112 closest to my original capacity, what say you?
If you click on (maybe double-click) the part number in the catalog
listing, the data for that part number will appear in the pane on the
left side of the browser screen. In that data will be a drop down box
that allows selection of a specific capacity range. As I recall, one
of the selections is the exact capacity you originally reported. When
you select it, the capacitor part number will change to the one for
On Wed, 24 Sep 2008 00:20:18 -0500, Tom Veatch wrote:
Yes, I double click the PN and it show the capacitor spec. I believe that's the
one I should buy.
I did not go to the trouble of disassemble the motor as suggest by some
woodworks here to find if the switch is the problem. Anyway the switch is
mounted externally. I just tested the capacitor by shorting it as suggested by
Doug. Thank you and everyone.
You should use as close to the original value as possible for the best
starting torque. Must be your motor is 3450 rpm. My original reply about
motor capacitors was based on a 1725 rpm motor. For a 3450 rpm motor, the
capacitors are usually around 200 mfd per horsepower, so that would fit with
what you have. Like I said before, you don't have to be exact on the mfd
value. Even brand new start capacitors usually have a 10 percent tolerance.
If you put one in that has a large difference in mfd value, stick a piece of
masking tape on the new capacitor and write the original mfd value on it in
case you have to replace it again at some point.
I ordered the capacitor from McMaster-Carr this morning: PN# 7245K112 AC
Motor-Start Capacitor 216-259 Rating, 1-7/16" Case Diameter, 110-125 VAC.
It's exactly the same spec. but 1/16" larger in Diameter and the capacitor
casing is slightly larger anyway.
Thanks Doug, I really appreciate it.
Thanks for your confirmation. Before I removed the motor from the DP I suspect
either, the bearing or carbon brush was bad. As I rotated the pulley it rotated
freely. I knew immediately it was the motor's start capacitor. I wish I had
tested my lightly used, new 8" jointer's motor in KC before I moved. It had the
same symptom. I sold the jointer for a song, and the buyer insisted I gave him
the old motor as the new motor (I kept the new Baldor motor). I bought with the
incorrect RPM. Thinking back, the buyer must be thinking how stupid I was.
I should have thought of McMaster before I posted here. However, I would like to
know how do you buy from McMaster? They need company names etc, and I am
buying for myself? I went to page 925 in McMaster, but no part 7245K17.
Thanks for your help, any other source with a correct capacitor?
Just make something up. Or you can do what I did and put in what I
will call my company if I ever decide to start one.
I've bought from them a number of times and they've shipped straight
to my house, no problems.
The only thing I don't like about their setup is that they don't tell
you shipping up front, so you have to check the invoice. It's very
reasonable, though. They're not the kind of company that will charge
you $10 to ship a $2, if it doesn't actually cost $10 to ship it.
Two (2) possibilities.
1) Bad start capacitor.
2) Bad centrifugal switch.
Grainger can do a match up for a replacement capacitor.
Replace cap, if that doesn't solve problem, head to a motor repair
Replacing a switch is a total PITA.
My guess is you will spend 60%-70% of new motor cost to make repairs
with makes which makes repair a tough call.
And how did you determine this?
More often than not it is the centrifigual switch. May have dust in
the contacts. Supposed to be a rubber boot that makes it dust proof,
but, depending on the origin of the motor, maybe bad.
Does what you describe. Does not let the start circuit pull in.
Contacts are supposed to close when the RPM's run down, but dust
prohibits. When you spin it your are doing the same thing as the
start circuit does, that is, starting the motor.
On Tue, 23 Sep 2008 07:56:18 -0500, Frank Boettcher
I've not witnessed a large majority of all motor failures of this
type, so I'm not qualified to dispute that statement. But I can say
that I have experienced two motor failures that presented the reported
symptoms. In both cases, the failure was due to a leaking and failed
capacitor. The switch in both cases was defect free. But, perhaps my
experience is atypical.
I had the same experience.
To test for centrifugal switch, disconnect starting capacitor and measure
voltage on capacitor leads during startup. (briefly, so as to not
smoke the motor). No voltage means bad centrifugal switch.
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