I like Mark Hockett’s fixturing idea. He uses some expanding studs for fixturing a piece. That way, there’s not even a bolt head standing proud to run into with the cutters:
Expanding studs on the fixture and ready to go…
A stud looks like this. Through bolt with tapered head…
The head drives into the expanding part as you tighten it…
Here is a part being tightened down with a hex key…
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My concern is the studs are located in a threaded hole. Would it be better to make the stud just a bit longer and counter bore the threaded hole to locate the stud exactly where you want it to be.
Dave
I use a commercial version of this hold down and have had great success. To address Dave’s concern mine have a bottom sleeve that does press into a counterbored hole in the fixture base for accurate locating. The top of the sleeve has a similar taper to the bolt head that is pulling down, so the expanding sleeve is being wedged open from both the top and bottom. Another nice feature of this type of clamp is that it pulls down on the part as you tighten it as well as the expansion outward.
Are the expanding studs homebrew or a commercial product?
Using counter bored holes sounds like a good idea for increased positional accuracy.
What is your commercial source for the hold downs?
The ones I have I got from All American Products (http://www.allamericanproducts.com/) but I just did a quick check of their site and I did not see them. If I can find a link to them I’ll post it here. Maybe I’ll give them a call and get the part #
I recall using Hilti drop in anchors in a pinch. They make them in an assortment of sizes. They have the slits already cut. Just have to clean them up. Make a tapered head screw. http://www.northlandconstruction.com/products/1483/orig/05-7405.jpg
Thanks!
After a bit of Google I found:
http://www.practicalmachinist.com/vb/cnc-machining/anyone-using-dexloc-devices-162715/
The website for the Dexloc pins is http://www.dexloc.com/
Mitee-Bite makes a product that works like this. They’re called ID XPANSION CLAMPS. I use them on our fixtures in our machine shop.
Their website is http://www.miteebite.com/