Ordering a 6-jaw Chinese Chuck-

[ErichKeane]

So, I just watched this video:

about the set-tru style chucks, the one thing that stuck out to me is the size of the set screws. The chuck I bought only has a 5mm register, so that obviously wouldn't work. However, I would think I could bolt an 'adapter' to the back to make it work. Now that I've seen it, I think I have my 4 jaw already attached to the back of a true-adjust back plate, except with an adapter to make up the register!

I wonder if I should just mount my new backplate (that is flat) to my 4 jaw and see if I can create something to make my 6 jaw into a homemade true-adjust.

 

[mikey]

That might work but you'll have a fair amount of chuck overhang. Plus, with so many interfaces the chances of something moving under load are higher but it might work for light work. OR you could return the 6 jaw and get a real set-tru chuck ... $$$.

 

[mksj]

I would check the chuck first and then decide where to go with it. If off, you would be better off taking a little off the back plate registration step and using the tap method. I have three set-true type chucks, one which I made. They tend to stay within spec. which is usually 0.0004" over most of the scroll range or collet variation. If it is slightly out, you can nudge one of the adjustment screws and compensate easily. The adjustment screws are 12mm fine thread with flat heads, you need a deep registration step for these types of chucks.

I do recall a few postings for the Shar's 6J Scroll Set-Tru version chucks with 2 piece jaws and they were satisfied with their performance. They were less than 1/2 of the comparable Bison, Rohm and PBA types.

6" 6 Jaw .0005" Adjustable Universal Chuck 2 Piece Jaws

www.shars.com

 

[ErichKeane]

So, I remembered why I did the offset-ring on my 4 jaw My 4 jaw has 4 bolts really close to the center that end up being in the way of the L1 taper with a normal backing plate.

I also worked on my 3 jaw. The jaws closed properly, but runout measured at ~.025" (yes, 25 thou!). I tried tapping it, but as soon as I would tighten it down it went right back. SO, I pulled it off the backing plate and realized the register was ~3 thou too big! So I was clamping oddly on the chamfer I think!

I re-faced the contact surface (I used cutting fluid last time, which made the finish horrible), then turned the center section down a little more than 20 thou, so I would have adjustment room. I re-mounted it, and indicated it in to a little more than 1/2 thou (touched both lines of a 1/2 thou indicator) at 3 different diameters!

I figure I'll try to do the same with the 6 jaw, but I'll have it for the situations where I've currently been abusing my flex collets, which is stuff I am afraid to clamp in the 3 or 4 jaw. I can keep the collets for when I need an accurate center BUT, probably won't be doing a home-brew adjust-tru.

 

[ErichKeane]

Got it yesterday so unpacked it today. It is of surprisingly good quality! I opened the back, and it seems to lack the common chinesium grit that most do. I cleaned it a bit, oiled and greased it, then put it back together. I turned down the backplate about 10 thou under so I can dial it in later.

The backplate is a cheap one (less than $100 for L1 apparently means Swiss cheese!) And I was able to find a place to drill the holes. Dinner bell rang right as I was setting it up in the mill!