Making small helical gear(s)

[Dave Smith the 16thParticipant @davesmiththe16th]

Tried a load of the gear lists and nothing seems to match my gear. The closest is a 20DP gear, but the OD is 1mm smaller than the gear in the picture below.

[HopperParticipant @hopper]

Might be time to seach out a car wrecker to get parts.

[JasonBModerator @jasonb]

As I said earlier the diameter will vary depending on teh helix angle so unless you can find a gear with the same algle you won't get an off the shelf match.

How does the gear fit to the shaft as that is something that may also need to be correct especially if it is splined or otherwise shaped internally.

Hoppers option sounds good, what is it off?

[Dave Smith the 16thParticipant @davesmiththe16th]

The plastic gear must have been formed on the shaft. I think the thread on the left part extended the entire length and they ground some off and then sliced some to lock the gear into place.

 

Searching a wreckers wont help find a solution to a weak part. Thats why i need to make a gear our of something else.

 

Thanks.

 

Edited By Dave Smith the 16th on 02/06/2016 22:35:01

[HopperParticipant @hopper]

Measure the angle of the teeth with a protractor. Cut the gear like you would cut as a straight spur gear with whatever module cutter matches the original, or make your own flycutter. But set the gear blank up at the same angle as the teeth on the original. This will give you the angled teeth to match your worm. Yes it is not a true helix but it works, especially for low load and infrequent load applications like this.

For indexing, use a lathe change gear or similar mounted on the end of the spindle you mount the gear blank on for machining, with a pointer engaging with the teeth to lock it in position for each tooth.

Make the new gear out of bronze and drill, pin and loctite it in position, after turning off the remains of the old moulded-on gear.

To avoid future wear on the gear, keep the "leadscrew" that it powers lubricated with a non-stick teflon spray on lubricant. The failure of teh original gear was probably not down to "weak part" as to unlubricated screw causing overload (unless you weight 300kg or something !)

[Dave Smith the 16thParticipant @davesmiththe16th]

The issue is nothing matches the original gear. The equivalent would be a mod 1.314 ?? A DP20 is the closest but the figures suggest that its 1mm smaller than the gear i need to make. I made a tool which seems to fit but whether it cuts who knows

I need a straight flycutter no an angled one.. Silly me.

Plenty of grease in there normally and its in a sealed part of the motor, so not a lot of space for the grease to escape. Although i have not seen how much grease there is in one thats broken.

Its a common failing point on these cars, so i think the part was slightly under specced. Although they last well beyond the warrranty so to them they got it right. Why spend more when it fails out of warranty and you can sell them a new motor because the gears are not sold on their own.

 

Thanks.

 

 

Edited By Dave Smith the 16th on 04/06/2016 21:16:05

[Dave Smith the 16thParticipant @davesmiththe16th]

Another PITA now

I got the shaft that the gear fits on and i may have mentioned i think the bar was threaded all the way and they ground off sections and took slices out of the thread to secure the plastic gear.

Thinking it maybe a good idea to thread the gear and attach it with loctite or a roll pin. I have a metric lathe and measured it at 8TPI. damn.. OK i can get it to 8.005 so that shouldn't be a problem i want it tight anyway.

But the shaft is 11.9mm (0.468&quot. Dashed my hopes of buying a tap and cheating.

What steel do i need to make my own tap? It will be used for aluminium, but possibly brass later on.

At least the heat wont be an issue, i built a furnace to melt aluminium a while back and it may even melt steel if i try

Will a towbar bolt be hard enough? The only thing i can think off i have to hand. Otherwise i need to order something and even more delays

Thanks.

[HopperParticipant @hopper]

Why make a tap? Simply screwcut the ID of your gear blank in the lathe to fit the shaft it is to screw on to. Much easier than making a tap and then trying to grind the chip clearance relief on the teeth etc etc.

Silver steel is a common choice for making taps if you really must. Harden it at cherry red then temper to light straw.

[Chris SheltonParticipant @chrisshelton11794]

This looks like a seat adjusting motor from a Mondoe or Jaguar, these are available on eBay made in brass.

They are rather pricey but, they do last OK

Search for Mondoe seat adjustment gear will show a few, all about the same price.

HTH

[Dave Smith the 16thParticipant @davesmiththe16th]

Yep thats the one but the brass ones are variable. Some come in 3 pieces and some have straight cut teeth.

The hardened shaft needs to be ground off for most of them.

Never cut a sub 12mm internal thread as yet. The tool i ordered some time back arrived looking totally different to the picture. The picture appeared to be a shaft with the carbide bit brazed directly. When it arrived the tool have a 90 degree bend then the bit brazed to that. Smalled it will thread is approx 20mm. So i never bothered trying an internal thread.

Just looking for simple options. But not buying one even though it would have been cheaper

Thanks.

[HopperParticipant @hopper]

For brass you are better off using a a HSS internal boring bar, the type that holds a piece of 1/8 or 3/16" HSS in one end with a grub screw. Then you can grind the HSS toolbit to suit the thread profile you want. (Probably Acme but if Jaguar are anything like British motorbike manufacturers, don't bet on it.)

[Dave Smith the 16thParticipant @davesmiththe16th]

The shaft is only 8mm diameter and the thread depth appears to be 2mm, with a 1mm fairly square profile, slight taper outwards approx 1.5mm at the outer edge? Although i only have the calipers to hand at the moment and the jaw is a tight fit.

It will be a Ford part rather than a Jaguar one. The Jaguar was a Mondeo undeneath. Buy parts from Jaguar and they come stamped with Ford on them. Oddly though some parts are cheaper than buying from Ford?

I think grinding the thread off would be an easier solution. Just hoping to pass on a few extra ones to club members who may not have the facilities to grind the teeth off and drill and pin it.

I may try and make a boring bar, i never seem to have the right stuff to hand. 2" round stock maybe excessive to make a 6mm boring bar

Thanks

[HopperParticipant @hopper]

Sounds like it would be easier to pay the $25 for an aftermarket brass Mondeo gear on Fleabay. You could hardly buy a piece of brass to make your own for that price, something that is a constant annoyance to me. I always seem to end up spending a week of my spare time making a $20 part from $50 worth of materials.

Edited By Hopper on 08/06/2016 02:54:25

[Roger HeadParticipant @rogerhead16992]

Posted by Hopper on 08/06/2016 02:52:24:

I always seem to end up spending a week of my spare time making a $20 part from $50 worth of materials.

It's the journey, Hopper, not the destination.

Roger

[Michael GilliganParticipant @michaelgilligan61133]

Dave,

I presume you have seen this already, but, for the benefit of the discussion: **LINK** shows how to install a brass gear.

Personally; I don't like the 'drill it & pin it' approach … The next breakage could easily be the worm-shaft.

MichaelG.

[JasonBModerator @jasonb]

Dave are you sure it's 8tpi as that diameter and the sizes of crests and vallys you mention could make it a standard 12×3 trapizoidal thread.

Might be possible to get a flanged nut and cut the gear teeth into the flange, solder on an extra bit of brass/bronze for the other side.

Or you can buy taps for under $20 on the net which you would soon recover if making for other club members

Edited By JasonB on 08/06/2016 10:09:51

[Dave Smith the 16thParticipant @davesmiththe16th]

Never sure of anything but with a bit of parallax error

[Dave Smith the 16thParticipant @davesmiththe16th]

Maybe its the pictures but that gear looks wrong. It should not be flush with the top of the shaftthe shaft extends very slightly and there is a hardened button the top inserted ball bearing rests on.

I can see that wearing the casing out.

I couldnt find an 8TPI tap under 12mm diameter. 0.468 i think? I put that measurement in a previous post.

As Roger says, Its the journey i want to make one, I dont even need one its just something that i thought i could knock out quite easily. But it seems to be a bit of a learning curve.

Excuse to buy a mill though

Had to get some aluminium in because i didnt have anything over 25mm. Some 2" steel to make a holder/flycutter. An arbor to take an involute cutter (if the tooth pattern matches)? If not its the flycutter ( 90degree) not angled.

3D printed a U shaped holder for the gear. This is to test the theory and possibly used as a pattern to mill one or cast one. It may even be strong enough if i use light cuts?

It cost pennies to make and approx 3 hours so not a big loss if i break it.

Thanks.

PS.. Suggestions that doesnt include buying one.

Cut the internal thread or grind the shaft?

Tight fit and threadlock, or tight fit and threadlock and a small diameter pin at the top section not the botton as in the link above?

Suggestions please

[Michael GilliganParticipant @michaelgilligan61133]

Posted by Dave Smith the 16th on 08/06/2016 21:26:31:

Tight fit and threadlock, or tight fit and threadlock and a small diameter pin at the top section not the botton as in the link above?

Suggestions please

.

Close sliding fit, and Loctite 638 … No pin.

MichaelG.

[Neil WyattModerator @neilwyatt]

Posted by Dave Smith the 16th on 08/06/2016 02:08:27:

It will be a Ford part rather than a Jaguar one. The Jaguar was a Mondeo undeneath. Buy parts from Jaguar and they come stamped with Ford on them. Oddly though some parts are cheaper than buying from Ford?

Was a bit miffed to find I could have got a Jaguar with the same body pan & engine as my Mondeo for the same price second hand 😕

[Dave Smith the 16thParticipant @davesmiththe16th]

On my previous car i had the Jaguar flip / remote key. Got some funny looks when i got the key cut.

Handed him a Jaguar blank and a Ford key to copy. Lucky he has a brain and not a robot. I said they are the same car and he compared the keys and said no problem.

Although the MOT guy coming into the waiting room to tell me my cars not there got my heart rate up a bit. Although he looked at the paperwork to see a Mondeo booked in he just looked at the key and assumed a Jaguar.

I have some Loctite 271, is that no good?

 

Thanks

 

 

Edited By Dave Smith the 16th on 09/06/2016 00:01:39

[Michael GilliganParticipant @michaelgilligan61133]

Posted by Dave Smith the 16th on 09/06/2016 00:01:24:

I have some Loctite 271, is that no good?

.

271 is classed as a very high strength threadlocker, and 638 is a retaining compound.

But I think 271 should be adequate for this purpose [especially as you have some]

… It's roughly equivalent to choosing between two grades of Silver Solder.

MichaelG.

[Dave Smith the 16thParticipant @davesmiththe16th]

Yeah i bought a bottle of 271, i put a tiny drop on 1/4 of a washer and pressed 2 together with them just overlapping approx 5mm and it took a good twist to break them apart.

Not troed silver soldering. What draws the solder into the joint? the heat or the flux?

Thanks.

[Anonymous]

Neither, it's capillary action.

Andrew

[Jens Eirik Skogstad 1Participant @jenseirikskogstad1]

The alternative to make worm gear wheel can you see this movie. Take the measure of the worm as you has in your gearbox as you showed the picture of worm wheel in gearbox in early post and create a gear cutter of silver steel to make a exact and correct size of the worm wheel.

 

Edited By Jens Eirik Skogstad on 10/06/2016 21:20:43

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