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26th Feb 2013, 02:42 PM #1Most Valued Member
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Backlash in Hercus 260 cross-slide
Recently I replaced the cross-slide spindle nut on my 260. It reduced the backlash, but not as much as I had hoped. I assumed the remaining backlash was due to wear in the spindle thread. That was until today when I noticed a large gap between the spindle bushing and the graduated collar. I was able to slide a 0.5mm feeler gauge into the gap. All of the backlash appears to be due to this gap.
Is this gap adjustable? Or should I fit a shim to eliminate most of the gap? Since the collar floats on the shaft a shim could be fitted between the collar and the handle rather than where the feeler gauge is in the pic.
Chris
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26th Feb 2013, 04:58 PM #2Cba
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See here:
260_CrossSlide.jpg
Chris
PS: there is a Hercus 260 maintenance manual. Its just some 20 or 30 fotocopied pages. But it can be quite helpful at times... It may be buried somewhere in older threads if you want to search. From time to time Hercus will list the manual on eBay for little more of what it costs them to photocopy it by hand.
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26th Feb 2013, 05:52 PM #3Golden Member
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be careful Dont loose the woodroofe key
how do i know
john
experience is what you get just after you needed it
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26th Feb 2013, 06:03 PM #4Most Valued Member
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Backlash in Hercus 260 cross-slide
Chris,
I have the Maintenance Manual and I've read that section about a dozen times. For the life of me I can't see what they are trying to achieve. The drawing is so crappy. Is face C the face of the graduated collar or the screw? Or both?
ChrisChris
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26th Feb 2013, 06:21 PM #5Cba
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Jack.. err Chris, the aim is to remove excess axial play, and to set a new initial axial play of 0.03mm. That is why you put the 0.03mm shim washer in. You could make a thin paper shim washer as its only used once. Then you take the facing cut across both the collar and screw. Now you remove the washer, and voila, you have set the 0.03mm axial play. Over time this will wear larger, and after a couple years of frequent industrial use you may have to repeat this operation. If its only hobby use, it will last 10 years+, especially if you keep your machine clean and oil every day before using the lathe. Chris
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26th Feb 2013, 07:03 PM #6Most Valued Member
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Thanks Chris. I understood the purpose of the shim was to set the axial play to 0.03mm. What wasn't clear to me is which face(s) I was meant to machine. Now I get it.
I'm surprised at how much this part has worn, given that the rest of the lathe seems to be in good nick. I hope to sort it out tomorrow.
Chris
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26th Feb 2013, 08:51 PM #7Most Valued Member
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Backlash in Hercus 260 cross-slide
John,
Thanks for the tip on the woodruff key. I'll keep an eye out for it.Chris
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26th Feb 2013, 10:49 PM #8Most Valued Member
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Did you blokes make up the special spanner for removing the spindle assembly, or did you come up with an easier way?
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27th Feb 2013, 04:18 AM #9Most Valued Member
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You could make the pin spanner if you want or you could just put a long pin in it and give it a knock with a soft hammer or put something on the shaft to protect it and use vice grips or a pair of stillsons,multi grips or pliers if you have some big enough,it should not be very tight.
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27th Feb 2013, 08:11 AM #10Most Valued Member
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OK, I'll try the pin and hammer first. If that doesn't work I have a crack with the stillsons and something soft.
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27th Feb 2013, 08:39 AM #11Cba
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I found the spindle assy does not need be tightened very much, and then a pin works just fine.
The problem is when you first get the lathe. The spindle assy may not have been taken off in many years, and/or previous owner may have tightened it hard. If you then try with a punch or the like, you will most likely damage the hole. Not that it matters, it just looks bad. And may leave a bad impression about the owner if one day you want to sell the lathe. Kinda like a dent in a car door, better if you can avoid damaging it in the first place. Chris
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27th Feb 2013, 11:25 AM #12Most Valued Member
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I stuck a 3/16 drill bit shank in the hole and was able to undo it with my fingers! All sorted now. It appears the small dome-shaped nut that holds the handle on was the main cause of the backlash. Seems a poor design when the small nut that secures a handle also pulls the spindle against the bushing. There must be a better way. Looks like I need to make a slotted screwdriver to tighten the dome nut.
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4th Mar 2013, 08:49 AM #13Mechanical Butcher
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The nut should be tight, then it won't be a problem. Rather than ruin a screwdriver, I use a flat plate with a slot in it.
The main problem I find with the South Bend / Hercus design is that the graduated dial can drift out of position unless its locking grubscrew is tight.
I modified my 9 inch to prevent it drifting without having the grubscrew fully tight.
Jordan
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4th Mar 2013, 10:34 AM #14Most Valued Member
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Backlash in Hercus 260 cross-slide
Agreed about the graduated dial drifting. Bruce (Abratool) made me a couple of knurled screws for my dials. They allow me to tighten the dial pretty tight. But for more critical jobs I have a 30mm travel dial indicator I can rig up as a poor man's DRO.
Chris
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4th Mar 2013, 11:56 AM #15Mechanical Butcher
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Instead of a grubscrew (where's that screwdriver?), a knurled locking screw is a good solution - the easier it is to use, the more likely you are to use it.
I like having the dial always movable but with no fear of drifting. It involves a bit of machining, but it's not visible when assembled. Basically, you prevent the dial from transmitting force to the cross slide. It's the friction there that can upset the reading, with annoying results.
Jordan
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