Mick,
Thanks for clarifying your desired use; that helps me a lot.
I’m going to make my recommendations with the assumption that you need to bore 2” square EVA stock or “glueups” so that you can mount it on a mandrel and turn it for shaping purposes.
There are two ways to approach boring the hole on a lathe. Either you turn the EVA in the headstock and feed a bit into the EVA with a tailstock mounted drill, or you’re going to turn the bit in the headstock and use some kind of sliding homemade jig to position and feed the EVA into the turning bit. Either will work, but the latter will require a very sturdy, well designed jig.
To turn square EVA in a chuck you need a 4-jaw chuck, not a 3-jaw chuck. When comparing various 4 jaw chucks, it would be prudent to select a chuck that has optional profiled tower jaws with serrations to hold the EVA firmly. Standard jaws designed for wood turning have a small contact area and do not grab ahold of EVA well. This can pose problems when you try to pull the drill bit back out of the hole as it will want to dismount the EVA from the chuck. Tower jaws have taller jaw contact surfaces and more securely hold onto the EVA significantly lessening the chances of this happening. So instead of looking for a chuck, I recommend you find a good set of tower jaws and then buy the chuck that matches those jaws. Jaws that are profiled have flat areas and are not completely circular. The flat area along the edge of each jaw further increases the holding power on EVA.
Here’s an example of some excellent #2 profiled tower jaws for turning EVA: [
www.oneway.ca] These are Oneway part #3658. When paired with either of these Oneway chucks: [
www.oneway.ca] (note those are not the tower jaws in the phote) or the Oneway Talon chuck [
www.oneway.ca] the #2 profiled talon jaws offer exterior holding size range of 1 1/2” – 2 5/8” which is ideal for 2” square EVA.
Note that it’s important to confirm a set of jaws capacity on a particular chuck, for example a set of #2 profiled tower jaws for Oneway’s larger Stronghold chuck will have a minimum exterior holding range of 2” – 3 3/8” which is too large leaving no capacity to compress the 2” EVA slightly when mounting.
Oneway are certainly premium chucks and you can find less expensive examples, these are the chucks I am familiar with. It should be noted that with Oneway (and possibly other mfgs), you can buy a bare chuck without the standard jaws and purchase the tower jaws separately for a similar cost to the complete Oneway or Talon chuck; you don’t have to purchase two sets of jaws and never use the standard ones. If you decide to buy from another company, just follow the idea of locating the right jaws first and then match up the best chuck with the jaws to give you the correct exterior capacity, not the other way around. You don’t want to buy a chuck and then find out you can’t get jaws for it.
For turning on a mandrel, you have some options. It’s likely your headstock has the ability to accept a tapered shaft in addition to your 1x8 thread. If it does accept a taper it’s probably a #2 Morse taper, this will be listed in your machines specifications section in your owner’s manual. Look in the area describing your headstock specifications.
If your machine has a taper shaft capability the easiest solution would be to purchase an inexpensive shaft and large capacity keyless drill chuck combo. For about $40 shipped you can get something like this: NOTE: this site won’t allow me to link an E b a y site (I can’t even write it normally) so copy and paste this into google search, it’s the first thing that comes up for me: 3/16-3/4" 3JT PRO-SERIES KEYLESS DRILL CHUCK & JT3-2MT TANGED TANG ARBOR MT2
You can mount anything from 3/16-3/4 inch mandrels in this. Pair these with mandrels that have center drilled ends and your tailstock live center and you could turn just about any grip imaginable.
