kerry super 8 problem

hello , i have just acquired a kerry super 8 pillar drill off the bay, it was advertised as having a slipping belt but was cheap so i bought it any how, what ive found out is that when u start drilling a hole the drill slows right down and the more downward pressure u apply it will eventually stop, so im thinking the motor is knackered? the motor on it is a clark 0.5 hp 0.37kw 1400 rpm 240v single phase, the guy i bought it off said the motor was at least 6 years old, does anyone have an idea if it is the motor or something more sinister , cheers Alan.

This should help, Alan : **LINK**

http://www.lathes.co.uk/kerrysuper8/

Nice machine … deserves a good motor.

MichaelG.

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Edit: __ I’ve just found this ‘rebuild’ : https://youtu.be/JDH5VDO_E64

Edited By Michael Gilligan on 27/03/2022 07:38:58

Alan

Although Clarke motors are budget price they are generally perfectly acceptable performers over a decent lifetime. 6 years on a drill seems way too short. Generally that sort of low motor power is accompanied by smells and magic smoke leaking out so it may be premature to condemn the motor.

How many capacitors does it have? The one time I saw a similar issue was with a capacitor start & run motor with a defunct run capacitor. Dunno if Clarke do capacitor start & run motors in that size but worth a look.

A stuck on centrifugal start switch in the motor can have similar effects as the start winding is always on and fights the main winding at higher speeds significantly reducing torque. Usually kills the motor because the start winding isn't rated to run for very long and overheats destroying the insulation. However run time on drills is pretty short so, with intermittent use, it might not get quite hot enough to die. Listen for the click at about half speed when the switch operates as the motor runs up to speed and slows down again. The two Clarkes I had through my hands had loud switches.

Capacitor start and run motors have a second, run capacitor in addition to the usual start one. They run smoother and have better torque distribution improving performance on heavier loads. At a price.

An effective way to verify that there are no load related mechanical issues is to set a ball bearing on the table and mount a pressure pad in the chuck to push down on the inner race. Slip the belt off and bring the pad down onto the bearing as if you were drilling. Twisting the chuck by hand as you increase downwards pressure will quickly reveal if something is binding up under thrust loads.

Clive

Need to isolate the cause before spending any lovely money.

The fact that the motor starts and only stalls when a cutting load suggests it may be OK, that is the problem is caused by something else, perhaps in combination. Some suggestions, apologies if teaching Granny to suck eggs:

• Operator Error:
  • Big blunt drill and a difficult material, like work-hardening Stainless steel. (A small blunt drill should spin without cutting.)
  • Drill jambing whilst trying to open up a largish pilot hole.
  • Big drill in wrong gear (spinning too fast, with low torque, causing a stall.)
• Drive-train fault, causing binding or wedging when pressure is applied:
  • Mis-assembly by previous owner
  • Broken bearing(s)
  • Problem in the sliding part of the quill.
  • I notice this is a nice machine with back-gear in addition to the usual belt change, but it's another thing to go wrong - has to be set up correctly, and the mechanism might be damaged.

Operator error is unlikely if Alan is experienced: I mention it just in case.

I'd proceed by disconnecting the power and taking the cover and belt off. Does the motor turn freely by hand? If the motor seems OK, concentrate on the drive train. Do the quill-side pulleys turn easily without any sign of trouble, and as the quill is moved up and down? Does the back-gear engage and disengage correctly. With a rounded end rod in the chuck for low friction when pressed on a plate, does the spindle turn freely when down pressure is applied, or does it bind up? If it binds, time to dismantle the quill looking for wear, bent parts, bulging, lube failure damage, bust bearings etc.

Perhaps a motor expert could comment on what sort of faults can cause a single-phase motor to start and run normally, but then stall easily. Outside my limited practical experience, which is single-phase motors suffer start problems due to capacitor or centrifugal switch failures rather than loss of power once running. The previous owner's report of belt slipping could be consistent with high drive-train friction before cutting starts.

Good news: lathes.co.uk says these machines are easy to work on and spares are available.

Dave

Edited By SillyOldDuffer on 27/03/2022 10:18:50

Alan,

Take a look at the belt grooves in both pulleys. I've had this problem on an aluminium 4 step lathe spindle pulley and with a good light and a wedge shaped gauge you might find the sheaves are worn to a J profile, allowing the belt to run on the narrow section at the bottom.

Without a load all appears to be normal but belt slip is very apparent as load increases, to the point where stall takes place.

Regards

Brian

You say the motor starts and runs, so can discount the centrifugal switch and capacitors. Dave has listed other things and I would go with him. Never seen a drill with a capacitor as fitted by the manufactures, they NORMALLY start on No load so don't need a cap. John

Is the motor actually stalling?

Or does the spindle stall and the motor continues to rotate?

Could be as simple as loose motor pulley if the latter.

As Hopper says, it is worth checking that the pulley is TIGHT on the motor shaft, and then for any other pulley in the drive train.

Once you are confident that the pulleys are not slipping on their shafts (Strip and clean both shaft and pulley bore if they are, before refitting and ensuring that the pulley IS tightly clamped to the shaft )

Then the belt becomes the suspect.

Hopefully, it is oill free, and not badly worn because of slipping.

Is it really the correct section? Don't expect an A section belt to drive in a B section groove!

Is it really the correct length? Sometimes a slightly shorter belt will allow the correct tension to be obtained within the range of adjustment by moving the motor.

Is it the correct tension?

All this is based on the assumption that the drill chuck is not slipping in the quill of the drill, or the chuck slipping on its arbor, and that the drill is being clamped firmly by the chuck itself.

Howard

Edited By Howard Lewis on 27/03/2022 15:14:01

Edited By Howard Lewis on 27/03/2022 15:15:09

Alan,

Silly question but is the spindle rotation correct? Does the drill cut metal/ wood at all.

Regards

Bob D

If the motor is OK then Brian may have it, the pulley is badly worn and the belt instead of pulling into the V and increasing grip is running on the bottom of the pulley with VERY little grip. The belt is tight ? There are many belt sections does it have the right belt for the pulleys ? WHAT stops ? Is the pully fixed by a grub screw that has slipped and cut a groove in the shaft, is a key missing ? If the motor is stalling then it will not last long as the start windings will come in and quickly cook ! Good luck Noel

Looking at the Lathes website, it like quite similar to my backgeared QDM750. Are you confident you have engaged the gears correctly? It is possible that you have not engaged a pin that locks a gear to a pulley. The drill chuck will likely spin until you exert any downwards pressure.

Brian

Edited By AJAX on 27/03/2022 19:44:25

Given the concern expressed about the vee belt … it’s definitely worth checking:

This page shows both the specified A section and the metric substitute :

**LINK**

https://www.bearingboys.co.uk/A-Belts-13mm-x-8mm/A42-V-Belt-Dunlop-120-p

MichaelG.

Edited By Michael Gilligan on 27/03/2022 20:52:24