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28-04-2016 #1
(As per the title, the bloke doing the work is Chinese, so I need to keep the instructions simple ...
I need some sfu1204 machined & need the resulting ends to be a tight fit when inserted into a bearing with an 8mm ID / bore.
But what would a tight fit be? 7.99mm? (because obviously 8mm machined ends will not fit into a bearing with an 8mm ID)
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28-04-2016 #2
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28-04-2016 #3
Thanks Lee...I'm just a little worried that the guy on the lathe takes any such measurement literally ...so if I tell him the ends are 8mm, then there's a possibility that they won't fit through an 8.0mm ID bearing (becuase obviously, 8mm ends wont fit into an 8mm bore...the ends need to be a miniscule shade less)
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28-04-2016 #4
If you want to specify tolerances then ask for the shaft to be machined 8mm g6 (should be within range of 7.986mm to 7.995mm) which should give you a sliding fit dependant on the bearing's dimensions...if you want a tight(er) fit then go for h7 (range of 7.991mm to 8mm) but you may have to press the shaft into the bearing (or run a bit of emery paper on the shaft till it fits...) if it's at it's upper tolerance of 8mm (range of 7.991mm to 8mm) and the bearing is also 8mm!
Last edited by njhussey; 28-04-2016 at 05:01 PM.
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29-04-2016 #5
Well yes unless he's got the bearings in hand for a piston fit he can only do his best, if it was me I'd ask for 8mm OD and as Neil suggests you then tweak the fit yourself with some fine wet and dry or emery paper.
As I say I had to do this on my Z leadscrew but it was from another source, if you can spin the screws it's quite easy to do and won't take much, my other two screws fit sweet on the AC bearings and all I asked for was 12mm OD.
Edit: Just to add, these guys do this all day long, so they know what their doing and have a good idea what the blank is going to, your gonna need to speak to them really for reassurance otherwise.
.MeLast edited by Lee Roberts; 29-04-2016 at 09:19 AM.
.Me
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29-04-2016 #6
Thanks guys - really helpful.
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23-02-2017 #7
For fixed side shaft k6 (interference fit)
for "sliding" side f6 or g7 (gap fit)
Bearing hole shall be H4
regards
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23-02-2017 #8
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23-02-2017 #9
Fifa,
what company do you represent?https://emvioeng.com
Machine tools and 3D printing supplies. Expanding constantly.
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23-02-2017 #10
I would just tell the guy that I wanted the end machining to fit an 8mm bearing, I`m sure he will have done hundreds before so will know how tight/loose to make it.
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