Making a backplate for an ER40 set tru chuck

[WobblyHand]

A while ago, I purchased an ER40 set tru chuck. At the time, the backplate wasn't available, so I bought a 2" long chunk of 5" diameter cast iron to make the backplate. Honestly, I guessed on the length, but it looks like it will work out very well. Bought the cast from Speedy Metals, as they were the only place where I could get cut by the inch cast iron.

Using some measurements from my G0752Z lathe, and from the Shars website, I have modeled the backplate. There are very few measurements given for the set tru backplate, but the chuck itself is very well documented. I still need to confirm my spindle measurements, but since the model is parameterized (almost completely) should be able to tap in the measurements into the spreadsheet and the model will be updated. Used FreeCAD to do the work. After the steep learning curve, it has been surprisingly easy to put this together.

Anyways, to start, here's a view of the spindle side. Hope to get this going in earnest this coming week.

 

[cathead]

I just ordered an ER40 square collet block for $30 and intend to chuck it in my lathe in a four jaw chuck. Wouldn't that be just
as good as one of those fancy chucks or am I missing something?

 

[Ed ke6bnl]

If dialed in it would be fine, maybe a bit more work for setup.I am just a hobbiest though

 

[WobblyHand]

I just ordered an ER40 square collet block for $30 and intend to chuck it in my lathe in a four jaw chuck. Wouldn't that be just
as good as one of those fancy chucks or am I missing something?

I suppose, if it was machined correctly and dialed in. Let us know how it turns out.

You could also machine your own chuck, only takes skill and talent. You have both.

But this thread will be about machining a back plate for my ER-40 chuck.

 

[rabler]

Make sense to me, a backplate made on the lathe to be used should run well if you get the backplate to spindle registration right. I thought about making a backplate too, since the D1-6 backplate is always out of stock at Shars, haven't been able to find another vendor with stock. A D1-6 backplate needs to be about 7" min for the stud circle (I don't have the exact dimension off hand), that size stock gets a little pricier compared to just buying one.

The collet block isn't a bad idea for ocasional use. The problem I personally would have with the block approach is that I'd first have to put the square jaw on if I had one of the other chucks, then go through the process of dialing it in. I wonder how hard it would be to a take one of the 4 sided blocks and cut it to 12 sides so it could be thrown in a three, four or 6 jaw. Obviously the challenge is minimizing runout.

 

[mksj]

One of the advantages of 5C and ER chucks on a lathe is you can get your hands near the chuck and not get worried about getting you fingers ripped up, you loose that advantage with collet blocks mounted to a chuck. I also tried using ER40 collet block mounted in a chuck and found that there was too much skew the further you went away from the collet. I ended up purchasing a Gator D1-4 Set-True back plate (~$140) and made my own ER40 chuck. At the end of the day, it would have cost about the same to buy the back plate materials as it was to buy one. I used the bolt pattern and specs. from the back plate to make my ER40 chuck. I eventually went with a Rego-Fix ER40 bearing nut. Dimensions on the Bison/Gator back plates are listed on their site if you need some specs.

There are a number of vendors with D1-6 back plates (semi-finished) in stock, here two for around $100, the first is an extra thick for a set-tru turning.

8-1/4" D1-6 Thick Back Plate

<h1>SB1435 8-1/4" D1-6 Thick Back Plate</h1> <p>Made thicker for use with adjustable chucks, this extra thickness allows a large step to be machined on the front of the plate for use with the adjusting screws on the chuck.</p> <p>The remaining material safely supports and secures the chuck.</p>...

www.grizzly.com

8-1/4" D1-6 Back Plate

<h1>SB1434 8-1/4" D1-6 Back Plate</h1> <p>Sized to fit D1-6 chuck mounts, these SB1434 8-1/4" Back Plates are precision made and mount to your chuck with minimal modifications.</p> <p>All South Bend back plates are made of fine-grain cast-iron.</p> <p>Whether you need a blank or semi-finished...

www.grizzly.com

 

[rabler]

There are a number of vendors with D1-6 back plates (semi-finished) in stock, here two for around $100, the first is an extra thick for a set-tru turning.

Most D1-6 backplates have a fairly large center hole, 2.5”+ to accommodate large spindle bores.
The collet chucks I’ve seen generally need a set-tru shoulder at around 2.125” dia, which falls inside the spindle bore cutout. So it takes a special backplate.

 

[mksj]

Not knowing which ER40 chuck being used and if it is a set-tru type or not makes it difficult to discuss back plates and options. If one is looking at something like the Shar's ER40 Zero-Set, the step specified is 2.165" with a .591" depth and an outer diameter of 5". The Bison D1-6 back plate (7-875-056) for their 5C chuck fits the same dimensions as the Shar's ER40. The Shar's ER 40 D1-6 back plate would appear like it needs to be turned down slightly to fit (2.26" diameter and 0.53" height). The Semi-finished chucks from Grizzly do not list dimensions and tend to use generic stock photos, but probably would not fit a 5" ER40 chuck. Of note, there are a number of unfinished cast iron back plates available, so an option as an alternative to trying to start with a cast iron square block material, or one could also use round steel stock. I purchased the two 5" rounds of 8620 for around $40. Wobblyhand did not indicate the chuck or lathe he was making the backing plate for.

5" ER40 Zero Set Fine Adjustment Collet Chuck

www.shars.com

5" D1-6 Threaded Black Plate for ER40 Zero Set Adjustment Collet Chuck

www.shars.com

Bison Back Plate, D Taper for SET-TRU Chucks, 5" D1-6

Bison Back Plate, D Taper for SET-TRU Chucks, 5" D1-6. Usually ships in2 days. Buy it and Save at GlobalIndustrial.com

www.globalindustrial.com

 

[WobblyHand]

I have the Shars ER-40 set Tru chuck. My Grizzly lathe uses a 1-3/4" spindle thread. About the only part I'm uncertain about is the register dimensions. Got to remove the 3 jaw and take some measurements.

If I understand correctly, please let me know if I have something wrong or out of order, the first thing I should do is to make a copy of the male spindle. Then face the cast iron round, drill it, bore it to the thread ID size. Then thread it all the way through. Once that is done, then make the register?

After that, remove the round from the chuck and install on the spindle to finish the rest of the turning and finishing.

 

[WobblyHand]

I was surprised that the piece of stock I needed to make a spindle copy was as big as it was. I wanted to have the stock be close to the same diameter as the mating back side of the register. Since that is about 67mm, I need a piece of stock that is close. Closest I have is 63.5mm or 2.5". I thought I would get away with a 2" diameter piece, but that would only leave me with a 0.1" lip to check for fit.

Anyways, modeled the spindle parts that are needed. During this modeling, I discovered I had a P10 blade for my AXA-8. Unfortunately, that only goes to 10 TPI. So found a P4 blade. Also found a source for a P6 blade. When I get either of them, I can make the spindle copy. Here is a picture of the spindle model.

When I make the backplate, what is the section that is critical? Is it the face that the backplate seats against?