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5th Feb 2020, 11:43 PM #1Member
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Hafco AL336 - disconnect leadscrew
Wondering if any Hafco Metalmaster AL336 owner has disconnected the lead screw from the gearbox?
My AL336D has a lead screw cover which restricts travel and doesn't allow the saddle to get close enough to the workpiece when I clamp it in a collet. I need to remove it and this task involves disconnecting the lead screw so the cover can slide off.
I have read the instructions for the lathe and for the lead screw cover but neither mention lead screw details.
I suspect that I have to knock out the [brass] shear pin from the sleeve which connects the lead screw to gearbox output shaft, but I'd like to confirm this with someone more experienced.
Any comments or suggestions would be most appreciated.
Thanks for reading my first post in this forum.
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6th Feb 2020, 06:54 AM #2
Hi Apprentice,
Welcome to our MetalWork Forums
I own a 2007 -12 x 36 lathe which I am fairly sure is laid out the same.The dials are all in the same position as the AL336.
Yes, I have had cause to remove / refit the lead screw.The spring crew cover compressed into a solid block and some how pops out of the socket made for it. The saddle then traveled under power into that and the shear pin failed to sheer because it was steel not brass. That caused the rack pinion to bend which I had to replace.
I tried to wind the flat cover spring over the lead screw but I found it impossible.
I found the only way was to remove the support block at the RH end of the lathe. If yours is like my machine it will have socket screw and taper pins securing the block.
The lead screw should be able to be wound back enough to the right to enable removal of the telescopic spring. Remove the (sic) shear pin.If I recall, I found this fiddly as the access was poor. CHECK that the pin is indeed brass. I replaced the steel one with a bit of brazing rod.
Best of luck to you as I would rather fill in a tax form or go to the dentist rather than do all that again.
To have a look around the rest of the forum go to the FORUM box in the top LH cnr of the page and click the little down arrow.A drop down menu will appear and you can select Forum Home on the top line. Click that and a scroll down page will come up.
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A big welcome to our Forums
Grahame
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6th Feb 2020, 08:16 AM #3Member
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The JET GHB-1236 lathe is very similar. I have found for other machines that JET have thorough manuals and they are based on the same generic Chinese machines that many of us have. I have downloaded this myself but not looked at it in detail.
https://content.jettools.com/assets/...236_man_EN.pdf
Tony
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6th Feb 2020, 08:39 AM #4Member
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Hi Grahame,
many thanks for your warm welcome and advise.
I've already done my tax and dentist visit for the year so I'll have to bite the bullet and remove the lead screw ... that cover is really annoying and restricting my work.
I can see two pins, the one on the gearbox side has a silvery colour, the other pin has a gold colour, I therefore assume (DANGER!) the golden colour pin is brass.
I gave the [brass] pin a semi-gentle knock with a punch but it wouldn't budge, I didn't want to do any damage, hence this thread.
Will have another go tonight ....
Thanks
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6th Feb 2020, 09:37 AM #5Member
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Many Thanks Tony,
Jet CHB-1236 is indeed very close to Al336D.
that's a great manual, much better than the manuals provided by Hafco.
The explosion drawings are of much better quality and detail.
Whilst it doesn't show the lead screw cover itself, it certainly shows how the lead screw connects to the gearbox.
Screen Shot 2020-02-06 at 09.26.55.png
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6th Feb 2020, 10:29 AM #6Diamond Member
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Remove lead screw shear pin at LH end and bearing block at RH end. Crank the carriage to the right, (the lead screw will move with it) until you have enough room to remove the spring cover.
The shear pin is typically 4mm dia brass.
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6th Feb 2020, 10:57 AM #7
It does beg the question. Are the pins parallel, tapered or stepped as the jet drawing shows?
I guess parallel, but the said pin might require a good belt if there has been a lock up. From my now shonky memory 13 years back
The 5c pin may have been on the point of shearing but didn't and waited for the hard to get at, tapered pin in the rack pinion shaft to sacrifice itself
My lead screw pin was hard to remove if I recall. Not sheared but nearly sheared not straight and difficult to drive out.
All I am saying is that the pin may be distorted and hard to drive out. You might need and extra pair of hands as the spring coil may need to be manually compacted and held out the way gain access to strike at the pin.
I suppose you already may have rotated the shaft over to see if the pin diameter is the same each side if it is parallel?
Grahame
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7th Feb 2020, 08:45 AM #8Member
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Job done,
thanks to everyone for your assistance.
For other's with the same task:
- there is no need to remove bearing block on the RH end of the bed, the lead screw will slide through the bearing block (see photo)
- move saddle near RH end, remove brass pin, engage half nut, move saddle to the right to move the lead screw.
- the brass pin was hard to get out and came out bent.
- the brass pin is 4x24mm, mine measured 4.04mm, I made another one to the same dimension but it was way too tight, in hindsight it should be 4.00 exactly.
IMG_5804.png
IMG_5802.png
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14th Aug 2020, 08:53 PM #9New Member
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New member
Having recently purchased AL336D I was having problems with lack of carriage travel until I found this forum. Removed the front lead screw cover and solved the issue. Thank you for the correct information.
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15th Aug 2020, 10:16 PM #10Diamond Member
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I keep 4mm brass round on hand. To make it into a shear pin I cut a piece, squish one end, thread the other end M4, install the pin and nip up an M4 nyloc. Importantly the job can be done without an operational lathe.
[QUOTE=TheApprentice;1962761]............................
- the brass pin was hard to get out and came out bent.
- the brass pin is 4x24mm, mine measured 4.04mm, I made another one to the same dimension but it was way too tight, in hindsight it should be 4.00 exactly.
/QUOTE]
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7th Aug 2021, 05:12 PM #11New Member
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AL336D lead screw shear pin failure
Hi, thank you all for the useful feedback on this page. I am new to using a lathe and have purchased an AL336D about two weeks ago. I was practising my threading on some soft aluminium bar stock and made the mistake of not manually checking the travel on my head stock and not disengaging my half nuts before my head stock came to the end of its travel on the lead screw. Hope this makes sense. Essentially the lead screw was trying to drive the carriage beyond where it would travel. This put all the stress onto the leadscrew. I head a bang and then noted my lead screw would work but could travel sideways out of the gear box (causing its position to move and causing it to become disengaged). Thanks to all your comments here I found out there is a brass shear pin under the left hand lead screw cover. This is a sacrificial pin to prevent further damage in the event the machine is in the hands of an idiot like myself. I found the failed part and have the problem fixed. To do this I pushed the headstock to the far right to pull out the lead screw cover on the left, unscrewed the lead screw cover on the left. Used a fine punch to knock out the broken brass pin. Keeping the half nuts engaged I was able to slide out the lead screw and also punch the broken pin out of this. Cheers
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