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View Full Version : RFQ: small machining job??



Wobblybootie
06-01-2011, 07:04 PM
Anyone want to give me a price for knocking out three of these for me. They are bushes / sleeves for my 10mm lead screws but I want to use John S's mounting system. I do not have access to a lathe and I cannot find 8mm angular contact bearings. Any one have any reasonable ideas / modifications or advice, I'm listening ... Oh and Hobnobs will be winging their way northwards John, if you are listening!!



3544

Jonathan
06-01-2011, 07:47 PM
I could make those. Boring such a small diameter over that length could present a problem. I take it it definately needs to be bored, not drilled? I could get an 8mm reamer.

m_c
07-01-2011, 12:23 AM
8mm reamer would be the way to go, or 5/16" would give 7.935mm, but that may be just too small even for a shrink fit.

Jonathan
07-01-2011, 12:30 AM
8mm reamer would be the way to go, or 5/16" would give 7.935mm, but that may be just too small even for a shrink fit.

If you get a shaft which is 8.000mm and a bearing, you won't get the bearing on the shaft without a decent amount of force. So I reckon 8mm reamer is good as I read somewhere you'd need 8.05mm to get a 'just slides on' fit.

m_c
07-01-2011, 12:54 AM
The numbers that stick in my mind are 1thou per inch diameter.
1thou clearance for sliding fit, the same for press fit, or 1thou under for tight press fit.

Only way to get the exact size with a machine reamer is if it's perfectly aligned with the rotation axis. If it's off any, it'll cause an oversized hole, which can be handy, but also a PITA.

AdieR
07-01-2011, 02:14 AM
You'll almost certainly need to ream out the 8mm, because you'll be lucky to find a boring bar that small - plus boring bars can "chatter" and cause poor sizing / finish. As a guide for reaming, the hole needs to be drilled 7.5 - 7.8 mm and finished with the reamer. Beware of putting an undersize diameter hole on an 8mm shaft, otherwise you may find they split and become damaged (esp with the 2 holes in the side, which will weaken it).

What are the two holes "pins or grub screws" for?

Wobblybootie
07-01-2011, 01:07 PM
Thanks folks ... I have read all posts and will take the advice. Adie, the screws were to secure the shaft so that the sleeve and shaft turn as one. A member has agreed to knock these up for me and pointed out the same flaws in my design as everyone else did. So once again, thanks everyone, I will post to my build log/blog as progress is made, (Don't hold your breath though, my build is progressing with the speed of a striking slug!!)

irving2008
08-01-2011, 12:52 AM
Use Loctite 680 rather than fixing screws/pins. Over time they will loosen and slip and you dont really have enough depth to get enough thread in there. A 1 or 1.2mm pin might be OK... but the loctite is permanent until you heat it up.

Jay
25-02-2011, 12:04 PM
Use Loctite 680 rather than fixing screws/pins. Over time they will loosen and slip and you dont really have enough depth to get enough thread in there. A 1 or 1.2mm pin might be OK... but the loctite is permanent until you heat it up.


Id be happy to quote you on these mate and i would bore the holes instead of reaming them but you will need to ammend the drawing so i know what size you want because their seems to be some confusion on what size your after in the bore.
Drop me a drawing via email in PDF,IGS,DWG and ill get back to you but dont foegt to let me know how many.

cheers
jay