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[machinist] Special T-nuts for registering vises to milling tables?
- From: Lawrence London <lfljvenaura@gmail.com>
- To: machinist@lists.ibiblio.org
- Subject: [machinist] Special T-nuts for registering vises to milling tables?
- Date: Mon, 2 Dec 2013 11:50:33 -0500
http://www.practicalmachinist.com/vb/general/special-t-nuts-registering-vises-milling-tables-276129/
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Special T-nuts for registering vises to milling tables?
I have a number of vises, rotary tables, index heads, etc that have slots in the bottom measuring about 0.688 wide and 0.150 deep, plus threaded holes to secure whatever is meant to go in those slots. My original thought was that these were intended for alignment keys that would also fit into the mill's table slots, but those measure only 0.625 wide. So it appears that the "missing piece" would have to be some sort of T-nut. Easy enough to make, but is there some sort of standard T-nut that's already made to go in there?
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On some of the vise/table combinations I've seen the slots are both the same width, on others they differ. Sounds like in your case you'll need to make a stepped key. Leave it a little loose--perhaps .010"-.015"-- so that the vise slides easily in the slot. If the key is accurately located on the base of the vise for a lot of work all you need to do is drop the vise on the table, push it back tight on the key, tighten it down and you're good to go. For those jobs where you want more precise alignment the clearance you left allows enough room to run a test indicator along the face and bump the vise around so it's perfectly square to the table...
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I was told that these slots in the base were made slightly oversize relative to the machine table slots the vice was expected to fit so that the key could be trimmed for precise fit and alignment after installation. Trimming by attaching a suitably hefty bar to the table then tramming accurately to produce a reference object which could be grasped by the inverted vice allowing the key to be cut exactly in line with the fixed jaw. Clearly best done with a brand new vice with nice new accurate jaws. Sounds logical. Especially when applied to some of the older style vices but I'd have thought the key way itself would have been cut by reference to the fixed jaw so a well made, parallel sided key would already be as accurate as could be produced by such trimming.
I find that careful pushing back against a key slightly loose in the slot permits resetting parallel to around a tenth of a thou per inch taper tolerance. Maybe a bit better on a good day with two stage bolt up procedure. Nip, tap, tighten. As always the judgement of how much nip and how hard a tap decides the result.
Clive -
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12-02-2013, 07:48 AM #5
- Join Date
- May 2011
- Location
- Texas
- Posts
- 2,321
Bolt an 11/16 piece of key to the vise and trim it to fit the t-slot in the place you intend to install the vise.
The more time you spend getting it right the less you spend dicking around later. -
Many sizes of these keys are available off-the-shelf from Kurt Manufacturing and from Enco
Reply
- [machinist] Special T-nuts for registering vises to milling tables?, Lawrence London, 12/02/2013
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