|Karl Mansson||14/03/2019 22:42:31|
|33 forum posts|
I give up.
I've tried getting this gear box off for something like two weeks now. I've taken every screw I can see out of it and it won't budge. The whole gear box is a layer cake with four parts. I've gotten the front end off, which holds the feed rod for the apron. What is left is the rear cover for the changewheels and the tumbler mechanism in a separate housing behind it. I've take pictures from inside the the rear foot of the bed and can see at least one threaded hole there which I assume holds a screw that I haven't undone. To get at it I need to get the change wheel cover off. I've removed everything fastener I can see except for the large flange nut pictured. It holds the large bearing for the leadscrew (this lathe has dual feeds). I find it strange because in the rest of the lathe the bearings will come out of their housings rather easily axially. Then again, this is a bearing that will see a fair amount of axial load being a lead screw bearing. So you'd want to keep it very closely aligned axially.
The casting flexes a little bit when I apply pressure at the top and reveals the separation between the parts. It does not at the bottom. Almost all of the parts have been painted over so it's hard to tell if that's why the parts are stuck together of if there are som fasteners I've missed left in there. The only thing I can SEE though is this nut and I think it may be compressing the other parts.
This became a long winded buildup to my question, just wanted you to know what I've tried so far and how the problem looks at the moment.
How do I get this nut off? This is the largest of its kind on this lathe. I have a single pronged spanner that I've used on the others and the best way to use it has been to use it to lock the nut and then turn the screw. I can't get a grip on this without damaging I'm afraid. I've used one of the change wheels for leverage but then getting the spanner in behind it becomes a problem. Plus I need to hold the change wheel by hand as not to damage it. I've put some penetrating oil on it now and I'll revisit it in a day or two.
The reason I want to get the gear box off is to be able to better handle the lathe bed for paint stripping and painting witout risking damaging the gear box castings.
|David Noble||15/03/2019 11:22:40|
81 forum posts
I sympathise, i've come across this before. The only way I have been able to do similar things is to make a dedicated 'C' spanner to fit the nut. I am assuming the blue handled spanner in the picture is the one you have been using. The spanner needs to be a perfect fit with no slack. Then the shaft needs to be locked in position, solidly. You can then apply serious leverage accompanied by some judicious shock to the 'C' spanner.
|Phil Whitley||15/03/2019 11:23:52|
|884 forum posts|
put a bolt into the end of the threaded shaft, and use some of these,
wrap a piece of aluminium round the shaft and put mole grips on to it? Strap wrench? Usually these nuts will come loose with a few smart taps of a hammer on the c spanner, even if the method of holding the shaft is less than 100% efficient.
|not done it yet||15/03/2019 11:46:18|
|3353 forum posts|
First, is it a CW or CCW thread. May need to insert a bolt, with a locking nut, in the shaft if the piece in question is CCW. A complete circle spanner is obviously best, but a C spanner may be adequate.
I've seen too many, to count, of these type on nuts that have been butchered with a blunt cold chisel or large punch, before now.
|Michael Gilligan||15/03/2019 11:49:51|
13998 forum posts
Good question ... But I think the answer is reasonably evident from Karl's first photo.
|Ian Johnson 1||15/03/2019 11:52:00|
|138 forum posts|
I'd use a decent sized pin punch and a hammer, Some smart taps against the slots (make sure it's not left hand thread!) and it will be off in no time. You will need to file off the burrs from the hammer rash if you are going to use the nut again, or just treat it like a sacrificial nut, and get a new one made, because if you are having problems getting it off, you will have problems getting it back on again unless you have the correct special castellated spanner.
I was a hairy ar*ed fitter/turner though!
|Ian S C||15/03/2019 11:56:13|
7447 forum posts
It looks as though there is enough thread sticking out from the nut to see if it is left or right handed. While you whack the C spanner, it is handy to have someone else to hold the shaft.
Ian S C
|Nick Hughes||15/03/2019 12:02:43|
200 forum posts
For my M/Cycle clutch basket that had the same nut and was both tight and recessed, I modified the end of a socket to fit the slots and used an air impact wrench to undo.
|Clive Foster||15/03/2019 12:08:07|
|1840 forum posts|
Whats worked for me with similar ultra stubborn nuts is to make a shallow, T handled, tube spanner with lugs for all the slots so that a balanced couple can be applied. I also used a big washer like spacer on the shaft to limit any attempt by the spanner to tilt. Obviously needs a little bit of clearance so the nut can unscrew. 50 thou / 1 mm should do. Usually by the time its come that far it will unscrew fairly easily. If it is still so tight that the spanner wants to tilt just add some smaller washers under the spacer so it can go another turn. Alternatively you could make the spanner bore a running fit on the shaft so it can't tilt but this will still let the spanner move endwise.
I think the single hook C spanner fails with really tight nuts of this form because the heel of the spanner pushes hard down in one place distorting the nut so the harder you push the more it distorts so the more it locks up. Obviously if its not super tight distortion will be negligible or non existent. The two handled, balanced couple spanner engaging all the slots simply tries to turn the nut with no attempt at distortion with its potential locking issues.
Of course as its my idea I'm gonna say its wonderful aren't I.
Allegedly butchering a big long reach socket by cutting lugs to match the slots on the end and applying an impact wrench works well. Not something I've done myself but many years ago I did see a properly made device of this type hanging on the special tools wall board at a vehicle main dealer. Possibly BMW car / motorcycle place.
PS Nick types faster and confirms that the impact wrench & modified socket works well. Something to try next time!
Edited By Clive Foster on 15/03/2019 12:09:29
|Mick Berrisford||15/03/2019 14:39:17|
|120 forum posts|
They are a common sight in most/every bike repair place as they are commonly used by many manufacturers, mainly front forks securing/tensioning and rear axle and suspension fitting. Got some commercial ones but also made a few from steel tube and old sockets grinding or milling the lugs when I couldn't source commercial ones. Depends on the size of the lathe one as to whether they are readily available, bike ones are probably up to 50mm across at most.
|Martin Connelly||15/03/2019 18:31:14|
852 forum posts
Here is one I made for a similar nut. Don't know what size your nut is but this tool will not damage the nut and is less likely to slip than a hook wrench. This is what the earlier posts were refering to as modified sockets which is one way of making this tool.
785 forum posts
My experience of hook spanner’s are that they are generally a waste of time and their slipping will damage either the nut or your knuckles or both. We encountered a lot of these nuts on aircraft and if there was no dedicated castellated spanner available then a suitable sized copper drift with the intelligent use of a hammer will loosen the nut without damaging the slots.
|Ian S C||16/03/2019 10:39:51|
7447 forum posts
It's sometimes useful to use two C spanners on a tight nut, you can put twice the torque on the nut before doing any damage.
Ian S C
|Karl Mansson||16/03/2019 12:15:32|
|33 forum posts|
Thank you for all the suggestions, gentlemen!
I did get the nut loos last night! I got myself a larger c-spanner and grabbed the shaft with a pipe wrench with some aluminium in between as protection.
The bad news is that it made no difference whatsoever. I got the leadscrew out but the sections of the gearbox still won't budge. I removed a C-clip from a shaft that I then tried tapping out. I soon realized that it was probably designed to be removed once the cover for the change wheels was taken off and had an integral gear on it. So I stopped and tried tapping it back the other way but I must have moved someting on the shaft because now it won't seat fully. So now I HAVE to get the thing apart.
Suggestions? I'm afraid I'll break a casting if I try prying more. I've tried tapping a knife edge into the seams between parts but so far nothing has given way. I'll inspect it again today with fresh eyes but I've already gone over it something like 20 times and still can't find any screws holding it together.
Edited By Karl Mansson on 16/03/2019 12:15:44
|Michael Gilligan||16/03/2019 14:42:14|
13998 forum posts
I have a nagging suspicion that you will find that the parts are dowelled together ... if so, you are right to stop trying to pry them apart.
A bit of 'hands-off' research would seem a good idea at this stage.
|Mike Poole||16/03/2019 15:10:06|
2108 forum posts
Don’t be surprised by a very long bolt coming in to the rear or the casting, check unexpected places like under the bed of the lathe and any other places that could be hiding a long bolt.
|Phil Whitley||16/03/2019 16:22:01|
|884 forum posts|
email@example.com does have manuals for some Habegger models, you could email him to see if he has a manual for yours. https://store.lathes.co.uk/search/node/habegger
|Karl Mansson||16/03/2019 16:51:23|
|33 forum posts|
I could have sworn I posted an update on this earlier but apparently not.
I got the parts apart! The last two screws were hidden behind the large bearing for the lead screw. Very complicated disassembly, this... I got the gear box off of the shaft but now I can't get the tumbler out of there.
As I mentioned earlier the shaft for the central tumbler wheel had a C-clip on it, indicating that the shaft is supposed to be a sliding fit through the bearing. I tried tapping it out earlier but it went a mm or so before sticking. So I thought I'd try to get the bearing out of the housing instead as most other bearings have been a slip fit into the castings on this machine. Got it a cm out or so but the the sound from my brass drift became very solid. I think I may have wedged a piece of dirt between the journal and the bearing. I've tried re-seating the bearing on the shaft and I've used a plastic bushing to take the strain off of the bearing while attempting to tap it home. I'm going to make a better bushing out of brass or copper as I suspect the shock isn't transferred properly. I don't have a press so I'll have to use my trusty old hammer and a brass drift.
Thanks againfor all the suggestions! I'll post pictures of what I'm dealing with this time around later. Any more suggestions on tackling this would be most welcome!
|Howard Lewis||17/03/2019 20:39:42|
|2330 forum posts|
Thanks for keeping us up to date on your progress, and successes. It is always good to know the conclusion to a problem, rather than being kept wondering!
|2254 forum posts|
Nice job Martin! I’ll have to remember that.
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