mbrown
Elder Statesman
Posts: 1,723
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Post by mbrown on Mar 12, 2022 19:52:04 GMT
You could try using a very small cold chisel, catching the screw at the top where the edge has broken off and gently tapping it anticlockwise. With luck, the chisel should cut a small groove in the screw which will give enough purchase to drive it around. You'll need to be careful not to mark the surface beneath.
Malcolm
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stevep
Elder Statesman
Posts: 1,070
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Post by stevep on Mar 12, 2022 20:02:12 GMT
Drill a hole and use an 'eesi-out' (or however it's spelled).
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Post by Roger on Mar 13, 2022 0:04:12 GMT
I've replaced the Y-axis gib screws and some of the X-axis ones - but the final one is eluding me - it looks like the allen head has partially snapped off. Any ideas on how to get this out? There's no purchase for pliers, and because of the concave nature of the end that's left, I can't easily get a punch in there to force it around... I think you're going to have to drill it out. If you can't offer this up to a pillar drill, ie you have to use a had drill, you're going to need a guide to keep it square in my opinion. A piece of Mild Steel bar, way 40mm diameter with a hole that's say 0.5mm smaller than the tapping side of the screw would be my starting point. You can start the hole using the hollow as a centre, but only go in 1mm to check it looks right. If that's ok, you can take the drill out of the chuck and use it to locate in the hole while you clamp the guide in place. You can measure how deep you need to go and maybe put a piece of tape on the drill as a visual indicator. If all goes well, you won't see any thread breaking into the hole. If that's ok, open up by 0.1mm at a time until you just see the thread breaking through. Then you should be able to break out the first couple of turns, enough to get a bottom tap to start. Obviously you will need to be able to get through to the other side. Others may suggest Easyouts, but they're pretty hopeless in my experience. If you've got them, there's nothing to lose, but I wouldn't spend money on them expecting them to work.
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Gary L
Elder Statesman
Posts: 1,208
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Post by Gary L on Mar 13, 2022 0:51:38 GMT
I've replaced the Y-axis gib screws and some of the X-axis ones - but the final one is eluding me - it looks like the allen head has partially snapped off. Any ideas on how to get this out? There's no purchase for pliers, and because of the concave nature of the end that's left, I can't easily get a punch in there to force it around... I think you're going to have to drill it out. If you can't offer this up to a pillar drill, ie you have to use a had drill, you're going to need a guide to keep it square in my opinion. A piece of Mild Steel bar, way 40mm diameter with a hole that's say 0.5mm smaller than the tapping side of the screw would be my starting point. You can start the hole using the hollow as a centre, but only go in 1mm to check it looks right. If that's ok, you can take the drill out of the chuck and use it to locate in the hole while you clamp the guide in place. You can measure how deep you need to go and maybe put a piece of tape on the drill as a visual indicator. If all goes well, you won't see any thread breaking into the hole. If that's ok, open up by 0.1mm at a time until you just see the thread breaking through. Then you should be able to break out the first couple of turns, enough to get a bottom tap to start. Obviously you will need to be able to get through to the other side. Others may suggest Easyouts, but they're pretty hopeless in my experience. If you've got them, there's nothing to lose, but I wouldn't spend money on them expecting them to work. Regrettably, my experience with Easyouts is the same as Roger’s. It looks highly likely that the head came off the screw from over tightening, and that being the case, you don’t stand much chance with Easyouts or chiselling the head, sorry. Drilling out, to Roger’s plan is your best bet. Gary
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Post by ettingtonliam on Mar 13, 2022 7:41:13 GMT
I know it sounds like a lot of faff, but you might be best pulling the table off, so you've got access to both sides of the hole, especially if you need to run a tap through it. Who knows, there might v be enough of the screw projecting on the inside for ypu to get a grip on it and turn it out.
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Post by racinjason on Mar 13, 2022 8:07:55 GMT
I use left hand drill bits to remove broken bolts most of the time the cutting force is enough to unscrew the broken bolt out. cheers Jason.
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Gary L
Elder Statesman
Posts: 1,208
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Post by Gary L on Mar 13, 2022 11:51:57 GMT
I use left hand drill bits to remove broken bolts most of the time the cutting force is enough to unscrew the broken bolt out. cheers Jason. That’s an intriguing observation. If the drilling force is sufficient to do that, then the corollary is that using a normal RH drill (as included in my set!) to prepare for an Easyout will make a bad situation significantly worse. (To be fair, mine are NOT trademarked Easyouts). But you can’t get LH drills at every corner shop, and not many if us will lay in a full set on the offchance, nor want to wait while a special order is delivered… Gary
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Post by William A on Mar 13, 2022 15:53:55 GMT
I found that a washer between the quill lock handle and the VH stopped it bottoming out and vastly increased the clamping force, so that's all good.
Here's a video of the axlebox prototype:
And here for the dimensioning of the remainder and the work on the mill:
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millman
Part of the e-furniture
Posts: 297
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Post by millman on Mar 13, 2022 17:30:55 GMT
Gary, left handed drills are available singly from Drill Service Horley, they deliver next day, been using them for years and am a very satisfied customer.
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Post by racinjason on Mar 14, 2022 1:26:59 GMT
I use left hand drill bits to remove broken bolts most of the time the cutting force is enough to unscrew the broken bolt out. cheers Jason. That’s an intriguing observation. If the drilling force is sufficient to do that, then the corollary is that using a normal RH drill (as included in my set!) to prepare for an Easyout will make a bad situation significantly worse. (To be fair, mine are NOT trademarked Easyouts). But you can’t get LH drills at every corner shop, and not many if us will lay in a full set on the offchance, nor want to wait while a special order is delivered… Gary I don’t have many just a few odd ones that I have brought usually when someone brings me a job to remove a broken bolt Cheers Jason
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Post by ettingtonliam on Mar 14, 2022 8:12:38 GMT
I don't like Easyouts, especially the small ones because if they break (easily done), a bad situation is made far far worse. Also, with small ones, inserting the Easyout into a small bolt can swell it, making it much tighter than it was.
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millman
Part of the e-furniture
Posts: 297
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Post by millman on Mar 14, 2022 9:08:52 GMT
Sorry it it’s a stupid suggestion but how about drilling a small hole, about 1/8 inch diameter as deep as possible without breaking through and Locktiting a piece of steel in the hole. When Loctite has cured it may well unscrew.
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Post by Roger on Mar 14, 2022 18:40:25 GMT
Sorry it it’s a stupid suggestion but how about drilling a small hole, about 1/8 inch diameter as deep as possible without breaking through and Locktiting a piece of steel in the hole. When Loctite has cured it may well unscrew. You might get away with that. However, since it looks like the cap head has been torn off, it's probably tight in there.
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Post by William A on Mar 14, 2022 20:27:40 GMT
I had a 2.5mm left handed drill bit and it 'bit' and unscrewed the grub screw - maybe I just got lucky?
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Post by Roger on Mar 14, 2022 22:12:51 GMT
I had a 2.5mm left handed drill bit and it 'bit' and unscrewed the grub screw - maybe I just got lucky? Possibly, I never seem to find that happening. More often than not I end up drilling the offending part out.
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Post by William A on Mar 16, 2022 10:54:48 GMT
Luckily my grub screw wasn't jammed - honestly I can't quite work out what had happened but it was broken off flush with the surface. If the drill hadn't bit, my next port of call was going to be to turn down a BA bolt to fit into the drilled hole and loctite it in, then unscrew.
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Post by William A on Mar 20, 2022 18:57:32 GMT
Well, another day at the mill to get those axleboxes roughed out and honestly, I'm very demotivated.
1) The X-axis handwheel on the Centec is suddenly very stiff and squeaks as it's turned. I've had the handle off at one end and the locknut off at the other and it seems to make no difference. Gib screws have been both loosened and tightened and it's made no difference.
2) I managed to over-dial after edge-finding by 25 thou - TWICE - and so now have a keep slot on one axlebox which is 1/16" wider than it should be. I've checked and double checked all my measurements, using a dial indicator in addition to the handwheels and the results have not matched up across multiple different features across all three boxes.
3) I have even cut one side of the slot and flipped the part around to cut the other side, and somehow they are >0.005" different in width.
4) I cut a second axlebox slot slot and it seems that not only did I over-shoot the mark, but the cutter was deflecting enough to leave a wider section of the remaining material at one end, so the slot side is shaped like a banana when viewed from above. Yes, I did lock the table.
5) Dialing in the depth of the slot to the exact same knee-dial value ended up with a slot floor that has ~0.010" variation even between 'front' and 'back' passes of the same axlebox.
6) One of the axleboxes has one side which is mysteriously not square to the top or bottom, despite being machined identically to the rest of them.
It feels like nothing at all has gone right. Everything is off and I'm rapidly running out of leeway to fix things. I can't even begin to establish how I made the mistakes I clearly have made, let alone a clear path forward.
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Post by Roger on Mar 21, 2022 21:59:14 GMT
Well, another day at the mill to get those axleboxes roughed out and honestly, I'm very demotivated. 1) The X-axis handwheel on the Centec is suddenly very stiff and squeaks as it's turned. I've had the handle off at one end and the locknut off at the other and it seems to make no difference. Gib screws have been both loosened and tightened and it's made no difference. 2) I managed to over-dial after edge-finding by 25 thou - TWICE - and so now have a keep slot on one axlebox which is 1/16" wider than it should be. I've checked and double checked all my measurements, using a dial indicator in addition to the handwheels and the results have not matched up across multiple different features across all three boxes. 3) I have even cut one side of the slot and flipped the part around to cut the other side, and somehow they are >0.005" different in width. 4) I cut a second axlebox slot slot and it seems that not only did I over-shoot the mark, but the cutter was deflecting enough to leave a wider section of the remaining material at one end, so the slot side is shaped like a banana when viewed from above. Yes, I did lock the table. 5) Dialing in the depth of the slot to the exact same knee-dial value ended up with a slot floor that has ~0.010" variation even between 'front' and 'back' passes of the same axlebox. 6) One of the axleboxes has one side which is mysteriously not square to the top or bottom, despite being machined identically to the rest of them. It feels like nothing at all has gone right. Everything is off and I'm rapidly running out of leeway to fix things. I can't even begin to establish how I made the mistakes I clearly have made, let alone a clear path forward. When things don't make sense and it's all going wrong, it's best to stop and go back to basics. Am I right in thinking that you don't have a DRO on the machine? Although this isn't essential, it solves so many issues with counting turns on dials and zeroing things. I wouldn't want to use a machine without a DRO, it's just too much like hard work. It would be useful to include pictures of the parts with the issues, showing the setup you're using and what's gone wrong. It's very hard to be sure what's going on without that. I'd try to figure out one problem at a time. Some of the issues may be to do with the machine, others with the setup and some with tool and cut choices.
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Post by coniston on Mar 22, 2022 22:23:58 GMT
As Roger says going back to basics is the only way, one thing I do when using hand wheel graduations (before I fitted a DRO) is to mark the division I need to wind into with a fine permanent fiber tip pen, just gives a visual reminder of where to go to. It can be wiped off with meths on a rag or IPA (not the beer type)
Regarding the X axis has some swarf got into the leadscrew nut? maybe on the Centec there is adjustment for backlash and maybe the leadscrew is not so worn where you are now using it? just a thought.
Keep at it I'm sure you'll see where your methods can be improved to achieve satisfactory results. Don't forget that steam locos need a bit of slack and although some of our esteemed contributors are working to excellent tolerances it is not essential to do so to achieve a working locomotive.
Chris
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kipford
Statesman
Building a Don Young 5" Gauge Aspinall Class 27
Posts: 566
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Post by kipford on Mar 22, 2022 23:06:01 GMT
William I am 85% through my build, not having used any machine tools since my teenage years. In the build so far the major bits I have written off are; a set of Tender Axle Boxes, A set of Driving Wheels and two crank axles so you are not alone. But I learnt from it and don't make so many mistakes now and I am still enjoying it even if. You will get there. Dave
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