How to repair a Kenwood Chef gearbox

The images and text below follow the work of fiddling about with the gearbox of a Kenwood Chef A701A but should help those wanting to do the same for A701, A702, A703, A703C or A707. I'm told (by Vic Curtis) that, for the A902 mixer, "although it is slightly different from [the A701] it was close enough to help in getting the gearbox stripped down". Take this link for the differences on the A902.

This guide to the different models will help with identifying which one you have.
However, be careful, since even the same model number can have major differences (e.g. there are two different planetary hub designs on the A701A).

I was just replacing the original drive pinion gear which was slipping and causing the beater to stop when loaded. The plastic version of the gear had split. I replaced it with a metal version which works well.

I've shown parts descriptions in italics below to help you order anything you need. I suggest you look through the notes below to see what you need to order, before starting to dismantle your mixer. There are a variety of names used for some parts. I've quoted the Kenwood name for the parts first (where known).

The planetary orbit hub drive (the unit which the beater fits into) can vary in design and is somewhat separate from the rest of the gearbox, so I've split the descriptions for this within this guide.

It's advisable to check all the gears whilst you have the gearbox open since they can become chipped over the years. The intermediate gear and planetary orbit gear are the most likely to be worn. Replace any that look damaged.

If you obtain a load of Kenwood foodsafe gearbox grease then you will be able to clean out and replace all the old grease as you go - but you'll need quite a lot (suppliers provide around 150ml.). Some of my pictures aren't as clear as they should be because they were taken with the grease still in. Note that the old grease may not mix well with the new, so make sure you clean out all the old before refilling. Pack it well to ensure good lubrication.

Consider getting a Gearbox servicing kit with all the essential parts and materials, or you could get a complete refurb gearbox if you have several spare pounds available.

If you find anything to add to this page (or correct it), please let me know - see the end of the page for contact details.

N.B. This web page is only intended to help you work on your Chef, but I don't take any responsibility for any damage or injuries which result.


Fault diagnosis (not guaranteed):

Basic faults:

The whisk or K-beater knocks against the bottom of the bowl or isn't reaching the ingredients in the bottom of the bowl. This just needs an external adjustment which is covered by the basic manual.

The beater stops during operation. It is fitted with an "overload protection device" which cuts out for a time. Reduce the quantity of what you are doing. Wait a while. Try again.

Mixer spins the wrong way. See this How To mend It item.

Can't remove the slow-speed outlet cover.
Look at my Step-15 photograph - it shows (not very clearly though) the mechanism for the cover release.
It's possible that one of the pivot pins has come out.
The lever certainly has to be pushed hard over before it will pull the pin from the side of the cover.
First try squirting WD40 and then use a very thin blade to slowly lever the covering plate off. You will probably see that the inside was full of 35 years worth of grease and grime. My thanks to John Drayton for this technique.
If the above doesn't work, you may need to unscrew the bottom cover so as to get access to the lever mechanism from underneath.
You certainly won't be able to access it from above as the top cover needs the slow-speed cover removing before you can lift it off.

Noise.
The first thing you can do is to replace the rubber feet at the bottom of the mixer. After fifty years these will have reduced down to solid lumps - plus they're quite easy to pull out and replace.
Now it is time to note that, as David Hallas of Lana's Kenwood Spares says "Any moving part in the mixer will have worn and therefore will create noise."
You can determine if it is the gearbox or the motor which is making the most noise by:
following steps 1 to 5 below and then remove the toothed drive belt.
Now you can try the motor without the gearbox to see how much noise it produces.
As a check, without the clutch dog being there, I used an electric drill, pushing down on the first gear, to hear how much noise the gearbox made compared to the noise of the drill on its own. This is a dodgy procedure and not recommended.

Gearbox faults:

General noise from gearbox.
As "Martin" says, on How To Mend It, "These always were a noisy beast, as long as there is no crunching from the gears it's all good."
The "clutch dog" and its associated gear are certainly noisy and can be replaced by a Gearbox conversion kit. It is not worth doing this if some other part is worn or damaged so I recommend dismantling the gearbox and checking it over before spending on such a kit.
Remember that all the gears are over 50 years old.

Liquidiser works but mixer doesn't switch back to the bowl when the top cover is replaced. The pin at the front underside of the cover pushes down on the top of a spindle to re-engage the front gears. Check this pin hasn't broken.

Mixes but beater stops turning under heavier loads. Replace the plastic drive pinion gear which is slipping. This plastic version of the gear splits.

Noise from the front of the gearbox and / or the beater doesn't turn.
Probably the planetary orbit gear has broken (some of these were plastic and, presumably, were designed to break if the whole thing was overloaded. See Steps P1 to P4 below and this How To Mend It item.
N.B. If the flat on the planetary orbit gear drive shaft hole is badly worn or damaged, then you will need a whole planetary hub assembly.

A second possibility here is that the rivets holding the planetary gear housing to the lower gear box casing, have broken. Thus, when the motor runs and the unit powers the beater, the lowest gear housing also rotates rendering the beater useless. The Chef will probably have made some loud clicks before stopping - as the last of the rivets sheared. See Steps R1 to R4 for this specific problem (courtesy of Charlie Riddock).

Can't remove the Slow-Speed Access Cover - see Step 15 below - a spray of WD40, pushing the cover to the left (to help clear the catch) and a gentle leverage should release it, allowing you to clean out the gunge which caused the problem.

If the release catch doesn't stay closed, see this How To Mend It item.

Grease dripping into the mixing bowl. See this How To Mend It item. In some cases, the planetary orbit chrome nut contains a rubber washer so it may just need undoing with a spanner, cleaning and refitting (see Steps P1 to P4 below).

Electrical / motor faults: If you have one of these, then this page won't help you (except for links to parts suppliers and advice sites, below). See my work-in-progress "motor" page to help with this.

Any smoke. Turn off at the mains and start searching How To Mend It (see links below).

Mixer runs at full speed, whatever setting is used on the speed dial.

Mixer starts intermittently but lacks power. Replace the carbon motor brushes.

I quote "Paul" from 2006 on How To Mend It, who advises "The most important maintenance you can do is to get the carbon motor brushes replaced.

Note also that the rubber feet should be in good condition. David Davenport told me that "the gap around the base is important for air flow through the motor. I carefully drilled the dead rubber out from the sockets and pulled out the pin that pushed through the new rubber foot to keep it in place."

If the motor has dropped then the rubber bushes probably need replacing.

If it is a noise problem then the rubber bushes may help but then it's a major job to replace the oilite bearings in the motor.

Lastly, note that, if you need to order parts from abroad, check the voltage matches yours.


Parts suppliers.
Do be careful which parts you order since there are often more than version of items eg. there are two versions of the drive belt - one if it connects to a plastic large pulley and another if it is metal.
These may help, but I'm not recommending any product, etc.:

N.B. There are two different types of gears for old Chefs - one set straight and one angled. The angled ones do not fit the 701 unless it has a gearbox conversion. Probably best to check which your Kenwood has before ordering any replacements. See Step 9 below.

For re-greaseing, the service manual recommends Shell LGP1 which doesn't seem to be available now. Other mixers (KitchenAid) use Benalene 930-2 (3.5 U.S. fluid ounces for one gearbox repair).

Lana's Kenwood spares with sometimes different products as "kenwood-kits2012" on eBay. David and Lana have been very helpful in spotting some of my errors.

GTA Electrics of 63 Henrietta St., Bulwell, Nottingham, NG6 9JB. Contact them for un-listed items using gtaservice@tiscali.co.uk or on 0115 979 7550.

4Kenwood - linked from Kenwood's own web site.

Torre Electrics.

Kenwood Chef Restore. This is their parts list.

Kenwood Chef Restore. This is their very useful list showing compatibility of attachments with different Chef models.

4ourhouse.

Spares2go.

Belstar Electrics.

Gearbox conversion kit. A kit to convert your gearbox to the A901 Chef direct drive mechanism (which gets rid of the "clutch dog"). See my page on fitting a conversion kit.

An engineer, Rupert Wheatstone, has designed a number of gadgets which make maintenance easier. If you encounter problems or regularly work on Chefs, then consider these. You can reach him via his "Seller" page on eBay. His gadgets include:
- a gearbox lock - "this fits into the mincer drive and locks the gear train, so that the dog nut can be removed with an open ended spanner - simple, if the nut threads are not stripped or the primary gear is not shattered",
- a tool design/suggestion for removing the centre speed control fixing on an A700D without causing any gouging marks.

For a complete restoration of your mixer, try here at Kenmix Engineering of Gosport, Hampshire or at Kenwood Chef Restore of Bridgwater, Somerset.

Note that Kenwood say that they are no longer supporting this model.

Notes re "How to shop safely".

Service agents:

Find a Kenwood-approved service agent.


Advice sites:

Kenny the Mixer site with videos, manuals, etc., etc.

IFIXIT page with loads of good stuff.

How to mend it.com

George's blog.

Lost your basic manual - try the Kenwood manual for the "Kenwood Classic Chef and Major KM330 KM630 series Instruction Manual-Multilingual PDF". It's 6MB though (mostly because it's in lots of different languages) but does not contain anything about the Chef internal layout.

For electrical problems, try Hyperentang's Blog.

See below for the full service manual.

Regarding various other models, the following may help with covering the differences - A702.

There is a Yahoo Group called WACEM (for "We Actually Collect Electric Mixers") where more help is available.
The Group Description is - "We're a collector's group interested in electric kitchen mixers. You probably thought you were the only one nutty enough to want that old mixer. Take heart, you are far from alone".

And if you want to see demonstrations of Kenwood Chefs in "old" kitchens, try going to the Goodwood Revival. David Davenport told me that "The Goodwood Revival event is quite an expensive motor sport weekend but is themed on historical motor racing. The attending crowds all dress in period clothes and have great fun. Kenwood have the shop and a café along with an old Tesco fitted out with 1960s stock and many other retro premises."

Service manual:

Note that the parts lists are in an erratic order.

This is the manual in PDF format (10.4MB).

Cover
Inside cover
Page 1 - Table of Contents
Page 2 - General description / Diagram of exterior
Page 3 - Specification / Dismantling gearbox
Page 4 - Dismantling gearbox, pedestal, feet, motor. Note that the drive belt for plastic gears (#197944) no longer has a red band.
Page 5 - Dismantling motor
Page 6 - Dismantling motor, speed adjustment, beater adjustment, gearbox servicing
Page 7 - Dismantling and testing the motor
Page 7 - Re-assembling the motor
Page 9 - Motor overview diagrams
Page 10 - Exploded diagram of the main body
Page 11 - Parts list (item nos. 1 to 9)
Page 12 - Parts list (item nos. 8 to 36)
Page 13 - Parts list (item nos. 36b to 55)
Page 14 - Parts list (item nos. 56 to 68)
Page 15 - Parts list (item nos. 65 to 70)
Page 16 - Exploded diagram of gearbox with planetary hubs (both types)
Page 17 - parts list (item nos. 76 to 97)
Page 18 - Exploded diagram of gearbox
Page 19 - parts list (item nos. 98 to 122)
Page 20 - Exploded diagram of motor - overview
Page 21 - Parts list (item nos. 123 to 133)
Page 22 - Parts list (item nos. 130 to 147)
Page 23 - Parts list (item nos. 142 to 149)
Page 24 - Parts list (item nos. 148 to 166)
Page 25 - Exploded diagram of motor - internals
Page 26 - Parts list (item nos. 167 to 189)
Page 27 - Wiring diagram
Page 28 on, dealing with attachments, not included.

Exploded diagram of Kenwood gearbox with TDA part numbers. Check the parts with the Service manual (above) before ordering - especially the "assemblies":
73 #183644 Planet gear (metal) with mounting shoulder
74 #199459 Push-on fastener
83 #203705 Planet hub washer
84 #182743 Planet hub and bearing
86 #182810 Planet hub nut
88 #177023 Clutch dog
89 #177530 Clutch dog spring
90 #177463 Large pulley assembly (now glass-fibre filled nylon)
92 #197920 for metal gear Timing belt
92 #197944 for nylon gear Timing belt
94 #178089 Special screw
95 #196043 Screw 2BA x 5/8"
96 #203731 Lock washer
97 #205052 Nut 2BA
98 #177334 Top cover assembly
103 #182482 Body assembly
108 #177384 Vertical drive shaft assembly
109 #177425 Output shaft assembly
110 #177449 Penultimate gear and pinion assembly
111 #177451 Intermediate gear and pinion assembly
112 #185769 Drive pinion assembly (metal gear)
113 #204436 Shim washer
114 #204448 Shim washer
A to D Direct drive conversion kit comprising:
A and B #KW650130 Intermediate and penultimate gears
C #KW696574 Drive pinion assembly
D #KW696586 Large pully (M6 nut)
E Sadly, this is a wallpaper which colour-coordinates with Kenwood-blue - Crown Berry Nice Maine Blue M0930.

Kenwood gearbox exploded
Tools and parts used for my Chef repair. See Step 6b for the picture hook.
Medium-sized flat-head screwdriver.
Medium-sized cross-head screwdriver.
Possibly an 8mm. spanner.
For removing the dog clutch gear - see item 6b below - one or more of:
Fairly thin pliers.
Adjustable spanner.
Small, flat piece of metal, eg. picture hook, frame support bar.
Drill.
Metal-cutting bits.
Vacuum cleaner.
You need to decide if you are going to replace the grease.
It is only worth getting some food-grade grease if you are going to clean out all the old grease.
See Step 10a below.
Re-packing new grease is easiest done by greasing individual gears / shafts as they are reassembled and then, after the gearbox is closed up, use a grease gun to inject sufficient grease via the access screw at the bottom of the gearbox.
For the above technique you'll obviously need a clean grease gun filled with food-grade grease.
Kenwood gearbox repair tools used
Step 1.

Remove the liquidiser cover.

Kenwood gearbox repair
Step 2.

Unscrew the chrome plate which is the high-speed drive outlet with a 7mm flat-head screwdriver.

Kenwood gearbox repair
Step 3.

You have now exposed the high-speed spigot or liquidiser pulley which is attached by a pin (if you need to remove it).

On the right is a picture of the spigot itself.

Kenwood gearbox repair Kenwood gearbox repair
Step 4.

Push the outlet catch A to allow you to remove the slow-speed outlet cover above.

Now pull (or lever) off the plastic end of the catch A.

Kenwood gearbox slow-speed outlet cover
Step 5.

Remove the cover, with the citrus juicer cover / stopper still attached.

Kenwood gearbox repair - removing gearbox cover
Step 6.

Ease off the toothed rubber drive belt (or drive pulley belt) by pulling it upwards whilst rotating it.

The dog clutch and large pulley can now be removed (see below).

Kenwood gearbox repair - drive belt removed

The dog clutch.

This is a rather tacky mechanism which produces a large part of the noise from your Chef.
It engages the rest of the gear train when the liquidiser cover is in place. This pushes down on the top of A (below) - the dog clutch gear. When pushed down, the gear engages with the knobbly bits on C - the large pulley.

To do any testing of the system whilst the liquidiser cover is not in place, you will need to press down on the gear using something like the flat of a pair of pliers. Be careful not to slip whilst doing this.

Rupert Wheatstone (see above under parts suppliers) says "(This technique) scared the life out of me - what you need is a soft plastic implement with a hole filled with grease, so that you can press down on the dog before switching on the machine - don't forget to remove the gearbox lock!"

To over-ride the operation of the dog clutch, or if the clutch is worn, see this How To Mend It item.

Step 6a.

To remove A - the dog clutch gear you will need to unscrew it whilst stopping the gears.

For the following guidance, I'm indebted to David and Lana at Lana's Kenwood spares (see above).

To stop the gears, first remove the planetary orbit hub drive (see separate section below).

Place a adjustable spanner on to the D shaped shaft.
Place a adjustable spanner on to the clutch dog and unwind.
On a tight clutch dog the adjustable on the shaft will lock on to a worktop surface whilst unwinding the clutch dog.

If the gears are stopped and the dog clutch gear doesn't unscrew, then your drive pinion gear is probably plastic and slipping. See Step 6b (below) in this case.

Under the dog clutch gear is the B - dog clutch spring and the C - large pulley which can now be lifted off.

Kenwood gearbox repair - the dog clutch
Step 6b.

This step is only required if Step 6A (above) fails.
Because the dog clutch gear cannot be removed, you will need to undo the upper gear box case so that you can lift off the dog clutch with it.
You need to gently ease up the large pulley enough to get a very thin excuse for a screwdriver (or thin pliers [I used a picture hook]) into the gap below it, and undo the screws holding the case.
Once all the screws are removed you can lift off the whole assembly.

If this doesn't work then you can try drilling a hole (as suggested to me by Brian Norris and Alan Diver), just big enough for your screwdriver (I used a 6.5mm bit), above the screw, through the pulley below the dog clutch (C above). The outer edge of the small round indentations is the correct place for a hole. Obviously, you will need to be careful to:

clamp the gear with an adjustable spanner, etc. rather than use your fingers,
avoid breaking the gear,
cover the entry to the electric motor compartment,
get rid of any swarf from the drilling - start with a vacuum cleaner,
find a thin screwdriver which will fit through the resultant hole.

Rupert Wheatstone (see above under parts suppliers) advocates the following technique - "In order to separate the gearbox halves, you need to wedge up the pulley, (as above), but then adopt another, more elegant solution to removing the two troublesome screws - as an alternative method to 'chiseling' the heads round and spoiling the heads - you could ... use a low profile screwdriver bit with a flange and a square drive turned by a flat spanner with a square hole. To loosen, before removing with long nose pliers - an alternative would be a screw driver bit turned by a flat spanner with a hexagonal hole, albeit a little wobbly."

Kenwood gearbox repair - drilling
Step 7.

You can now unscrew the upper gear box case but don't lose the locking washers.

The upper case should lift straight up.

If your Chef has been recently serviced, etc. then the silicone seal around the bottom edge of the upper case may hold it and you may have to be more firm in your lifting!

Kenwood gearbox repair - upper gearbox case removed
Step 8.

Pull the gears up, but keep them in order and especially don't lose their washers.

What remains is the Lower gear box case.

Kenwood gearbox repair - lower gearbox case
Step 9.

A is the original plastic-geared (split and slipping) "drive pinion gear".

B is the new metal-geared (works fine now) "drive pinion gear".

C is the "intermediate gear or 2nd. drive gear".

D is the "penultimate gear or 3rd. drive gear".

Kenwood gearbox repair - drive pinion gear

Watch out that you don't try to fit angled gears when the 701 normally has straight ones.
The angled ones are only found in later models and gearbox conversions.
Here's a picture of the angled intermediate and penultimate gears.
and here's the matching drive pinion gear which WILL NOT fit a basic 701.

Step 10.

Now you can access the slow speed outlet gear which can come out by pushing it into the cavity.

Kenwood gearbox repair - slow speed outlet gear
Step 10a.

This is the stage at which you may want to clean out all the old grease.

To help with this, it is easier to remove the Lower gear box case. The nuts and bolts holding this are quite tight and require an 8mm spanner.
This also makes working on the gearbox much easier.

You will need to scrape out as much as you can - watching out for washers stuck in the grease.
Then wipe out with a rag.
Then finish off by either:

using a steam cleaner, or
putting the parts in a (scrap) bowl and use an engine degreasant like Gunk, with an old toothbrush to get into those awkward crevices. Rinse with water and dry thoroughly.
Step 11.

Now you come to reassembly.
If you have changed any of the parts in the gearbox then it is best to try a full reassembly of the gearbox (washers and all) and its cover before (re-)greasing it. You don't need to screw the upper casing down - just check there isn't a gap where something is too large - and check that the gears turn easily.

Now refit the gears on their spindles (not forgetting the washers and plenty of grease).

You'll see that I've removed the gearbox from the rest of the mixer - to make working on it easier.

For all you food photographers - try using a small aperture to get everything in focus! (sorry, pet hate)

Kenwood gearbox repair - refit gears
Step 12.

Clean off any spilled grease around the edge of the casing and apply silicone seal around the edges of the gear box. A small tube of silicone makes this easier than with the regular DIY type.

N.B. Don't leave any spills inside where it can get into the gears.

You may wish to leave the gears out whilst doing this but that's up to you.

Apply a quite thin bead all round - somewhat less than James May did on TV since too much may squeeze into the gears.

Kenwood gearbox repair - seal the case
Step 13.

Refit the top gearbox cover and do up the screws (not forgetting the locking washers).

It is safest to do them up as you would a cylinder head - first doing them all up gently and then going round tightening them up.

Don't do them up so tight that you crack the cover.

Kenwood gearbox repair - refit top gearbox cover
Step 14.

Refit the dog clutch components.

Kenwood gearbox repair - refit dog clutch
Step 15.

This is the slow-speed outlet showing the mechanism of the release lever.
The stud which holds the cover can be seen at the right of the tube.

Kenwood gearbox repair - slow speed outlet
Step 16.

Refit the "toothed rubber drive belt" by the reverse of how you took it off (step 6).
Note that it should be a different belt if you replaced a metal large pulley with a plastic one.

Kenwood gearbox repair - refit drive belt
Step 17.

Replace the top cover, with the citrus juicer cover / stopper.

Try to find the plastic end of the outlet catch for the slow-speed outlet cover and re-fit it. The outlet catch is shown in the picture for Step 22 (below).

Replace the chrome plate on the high-speed drive outlet (see picture on right which shows the correct way round).

Kenwood gearbox repair - replace cover
Step 18.

Fit the lower gearbox felt cover, being careful to align the four holes with the screw holes on the casing. N.B. The holes are different for each side so check which way up you have it.
If fitting a new felt you may have to cut a slot for the release lever.

Kenwood gearbox repair - replace felt
Step 19.

Replace "lower gearbox cover" but be careful of the screws which will break the casing into which they connect if over-tightened (even a little).

Kenwood gearbox repair - replace lower gearbox cover


The planetary orbit hub drive - version with chrome cover.

If yours has a plastic cover, see the next section.

Step P1.

This shows the planet hub assembly.

To remove it, undo the planetary orbit chrome nut and then gently pull down / lever off the assembly.

Kenwood gearbox repair - planetary hub
Step P2.

This is the inside of the planetary orbit hub drive which I didn't need to remove for my Chef repair, but I did so to check it was OK and well lubricated.

In the centre is an out-of-focus view of the D-shaped shaft.

Kenwood gearbox repair - inside planetary orbit hub
Step P3.

This is the planetary orbit hub drive with its planetary orbit hub drive gear cog and the planetary orbit chrome nut on the right.

The three studs Hold felt washers on some mixers (thanks to Allan Wayte for this information)

Kenwood gearbox repair- the planetary orbit hub
Step P4.

Apply a blob of grease and then replace the planet hub assembly. This should push up into place.

Check the planetary orbit chrome nut before refitting to see if it has a rubber washer which may need cleaning. Do up the nut with a spanner - but not too tight.

Kenwood gearbox repair
The planetary orbit hub drive - version with plastic cover. This section courtesy of Charlie Riddock.

Step Q1.

This shows the planet hub assembly.

To remove it, undo the planetary orbit chrome nut and then gently pull down the cover.

Kenwood gearbox repair
Step Q2.

This is the inside of the planetary orbit hub drive which it is best to open up so as to check it is OK and well lubricated.

Kenwood gearbox repair
Step Q3.

This is the planetary orbit hub drive with its planetary orbit hub drive gear cog.

In the centre is the D-shaped shaft.

Kenwood gearbox repair
Step Q4.

To re-assemble, place the rotary arm on the D-shaped shaft and push up, making sure the cog engages as shown.

Replace plastic cover, which should push up into place.

Check the planetary orbit chrome nut before refitting to see if it has a rubber washer which may need cleaning. Do up the nut with a spanner - but not too tight.

Kenwood gearbox repair
The planetary orbit hub drive rivets. This section largely courtesy of Charlie Riddock.

Here we deal with the rivets holding the planetary gear housing to the lower gear box casing, which can shear.
In our units, there were 6 pins (some units may only have 3).

When the motor runs and the unit powers the dough hook, the lowest gear housing also rotates, rendering the dough hook useless. But you can't see this until the lower part of the planetary hub is removed.

If this has happened to your Chef, then I have only heard of one way of replacing the rivets - see below.

If you don't want to try this method, then you will have to replace the whole lower gear housing. You can't simply put new rivets in place as these would foul the inner cog rotation as it all sits flush. See at the top for a list of suppliers.
The lower gearbox housing and planetary gear are supposed to be one unit (a replacement should come as one unit).
There are some very cheap complete machines on eBay at times and, if you go for one which is broken, it's not likely to be broken in the same way and you could use it as a donor for the housing.

Step R1.

This shows how the planetary gear pulls down from the gearbox - if the rivets are broken.

Kenwood gearbox repair - rivets 2
Step R2.

Here is a view of the inside of the lower gear box, from above, with the broken rivets pushed up from the under side to show them clearly.

Kenwood gearbox repair - rivets 2
Step R3.

This shows the plate (from inside the gearbox) which should be held down by the rivets.

It shows the tear out of the broken 'cast rivets'. (Meaning they can't be drilled out and new rivets inserted).

Kenwood gearbox repair - rivets 3
Step R4.

This is the planetary gear which should be clamped to the gearbox by the rivets.

See the picture in Step Q4 above which shows how the rotary arm and cog sit flush, explaining why you cannot replace the broken cast rivets with new rivets.

And now for the fix, for which I'm indebted to Piers Butterfield -

"What I did ... was to drill out the six holes to a close fit to M5 (possibly M4) and in fact I drilled out another 6 holes, then countersinked the underside and fitted twelve (possibly over-kill!) M5 countersunk posidrive-head screws in place (countersunk in order not to foul the planet gear).

I think I ground them to length and used thin washers on the upper face so as not to foul with what was going on there.

I was aware that if any of these screws came loose they could do a whole heap of damage, so did them up pretty tight and used Loctite as well as 'staking' the screw ends, all to try and keep them secure.

The alternative would have been to put the screws in from above and thread the gear housing, but I wasn't convinced the cast metal would take the fatigue load. It's rather expensive if you're doing it professionally, but I got fed up with the rivets breaking!

Sorry but I have no photos as it's all assembled now and has been working hard for approx 5 years. I took it apart recently to attend to the input gear, and all seemed OK although it is of course wearing..."

Kenwood gearbox repair

And now, put all the left-over nuts, gears, screws, etc. in an envelope for safe-keeping.

Then let me know if the above helped, or if you found any mistakes (see below).

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This page last updated 9th. October 2017.
Images and text © Copyright Jim Batten, 2014-2017. Some images © Copyright Charlie Riddock, 2015.

Send corrections, comments, enquiries, etc. to Jim Batten