Collet chuck build - a work in progress

[Jonathan Coates]

I bought myself an ER40 to backplate adapter last year and have been slowly working round to getting it fitted. I'd guessed from the Ebay photos that it was a Myford fit, or something similar, and so would need some playing about with to get it fitted to my D1-3 spindle nose.
I machined a lump of cast iron that I've had for years, "salvaged" from a customer's site where they made continuous cast bars and had some scrap offcuts lying about. Well some accidentally fell into my van and have been sitting around for a long time.
I faced off a suitably sized lump and then had to bore the centre to accommodate the spindle nose shape. This has a slight taper and research (YouTube) led me to the Tangent Engineering compound sine bar as being the new toy that I needed. Can you buy these in the UK? No. Can I pay the price plus shipping from USA? Maybe, but it seemed like a challenge to make one. My version, see photo, is a little out on the centre distance of the pins by 0.4 thousands of an inch, but really really close is close enough.
This set the taper angle as close as I can tell is bang on as the bored hole seats onto the taper with no wobble whatsoever. Then I decided that I'd need to grind the taper bore to get a better finish, and because I got a Proxon grinder thing for Christmas.
Next then is to mount the grinder on the toolpost, but I don't have an adapter for that yet. That's next on the to-do list. There's a photo of the pre-utilised cast iron that this could be machined out of with sharpie layout lines to remind me what I was thinking.
As you can see from the photos I have a new sexy lathe toolpost which comes with a 1" or 3/4" mount for a boring bar. I considered this but it doesn't leave much grinder stuck out of the end and I think I'll occasionally need to poke the grinder in a bit.

 

[ShopShoe]

Jonathon,

Checking the fit of one part to another is often done with the bluing technique. There are many videos and writeups available if you enter "Checking the fit of a taper with Prussian Blue" in your favorite search engine. You may find Prussian Blue as "Engineer's Blue" or under another name. I buy mine from an auto parts store.

Regarding fitting your Proxxon grinder to your lathe: I made an adapter myself that fits my wedge-style QCTP and I have used it from time to time, but the setup is not rigid enough for a lot of things. There are some who have made toolpost grinders with varying degrees of success. If I remember right, small wood routers, laminate trimmers, and die grinders have provided motors for those projects. For more rigidity, the tool holder is removed from the lathe and the grinder is bolted directly to the cross-slide or compound slide.

I look forward to further posts on this project.

--ShopShoe

 

[Jonathan Coates]

I had wiped a bit of the blue yak on it. As an old guy told me years ago (joking) if the blue doesn't cover the whole surface, you didn't put enough blue on. This was a slight film on the lathe end after wiping the adapter bit on it.
Next bit was to put the adapter on and measure the gap on the faces. Now my feeler gauges have several shortcomings. They appear to only work in my right hand, they're not in any particular order and all the markings have vanished over the years. It must be ten years since these saw the light of day and the next thing they'll be seeing is the bin. (Pile of stuff that'll be very useful one day)
I got the indicator set up so that I could put the saddle back after testing the fit (no dials on these Chipmasters) which I thought was a good idea. The gap was measured and it was going well until some clumsy fool knocked the mag base onto the floor. On to plan B then, after a very light cut with the saddle lock on, I clamped a 123 block to allow the position to be repeated. This turned out to be robust enough for the most ham-fisted bout of swearing at feeler gauges.
I'd got the gap measured and put the chuck back on, returned the saddle to it's known point and locked it. Next I loosened the clamp and slid the feeler gauge alongside the 123 block. This would now be my position for the final cut. With a thin feeler gauge alongside the 123 block I got the taper so that the gap between the lathe spindle and my adapter is about 4 thou, or half a blonde one in metric.
Next step is the grinding when I've finished messing with the toolpost mount.

 

[Jonathan Coates]

I made a new DTI setup which clamps to the bed of the lathe for the next go at it. The grinder holder thing is finished and I did a bore grind. The first wheel didn't seem to do much so I stopped it all and it had a black splodge of, I assume, bits of the cast iron. The next wheel did better and I got what I thought was a poor finish.
I test ground a bit of stainless bar and it looks like an ***** has been at it with a file. Something not right here. Either one part needs to turn in the opposite direction, speeds are wrong, the wheel is wrong or the whole thing is too floppy to ever work.

 

[user 52078]

To be honest, I think you would be better off with a finely ground HSS tool and a finish straight off the lathe rather than your proposed toolpost grinding set up. Those mounted points for Dremel / Proxon type gear just aren't stiff enough or true enough and you are probably struggling to get in the right zone for peripheral wheel speed as well.
Sorry to be the bearer of bad news, but with a decently ground and honed tool you should be able to get an acceptable finish and more importantly one that fits the lathe spindle nose.
Good luck,
Martin

 

[awake]

Did you dress the grinding wheel (i.e., using a diamond point)? If not, almost certainly the stone is going to be just enough out of true to bounce around on that flimsy shaft, and that may account for the results you are seeing. I'm not saying that you will get good results - Martin's point above is well taken - but you will definitely get poor results out of any precision grinding setup if you have not dressed the stone.

Also - hopefully it just wasn't showing in these pictures, but make sure you cover the ways before spreading grinding grit everywhere!

 

[Jonathan Coates]

Thanks for the pointers guys, I'm dead set against buying diamonds, that got me into a lot of trouble in the past. Probably because I gave them to ladies who turned out not to like me years later.
Joking aside, I just brushed the inside of the chuck adapter before packing it in as the tiny wheel obviously wasn't running true. The stainless steel bit shows how much it needs truing first, at the very least, but I thought maybe turning up the rpm might get the wheel fast enough that it would do a fly-cutter job on the thing.

 

[ajoeiam]

I made a new DTI setup which clamps to the bed of the lathe for the next go at it. The grinder holder thing is finished and I did a bore grind. The first wheel didn't seem to do much so I stopped it all and it had a black splodge of, I assume, bits of the cast iron. The next wheel did better and I got what I thought was a poor finish.
I test ground a bit of stainless bar and it looks like an ***** has been at it with a file. Something not right here. Either one part needs to turn in the opposite direction, speeds are wrong, the wheel is wrong or the whole thing is too floppy to ever work.

Grinding is not a simple topic - - - do you have the right stone with the right bond and at the right rpm for your project?

I only know enough to know that for that job you would be rotating the piece slowly and the grinding is moving relatively quickly.
Suggest that you contact a grinding tool supplier (specialist) and make sure you get your basic parameters down.
What I'm remembering is the softer the material the harder the stone (and vice versa).
Truing the stone is also important.
Further details - - - need to talk to someone with experience!!! (That's likely a specialist!!!!)

(Your surface finish tells its tale.)

 

[ShopShoe]

I will add my 2 cents that you need to dress your grinding wheel or stone. The diamond point wheel dressing stones are not too expensive and you can build a holder to do the dressing, or buy one. If you search the catalog of any large tooling supplier you can find "diamond dresser" or "diamond wheel dresser." and there are plenty of options.

There is a caveat: diamonds are hard but mountings are not. I killed a single-point diamond dressing tool by putting it up to the wheel to be dressed too quickly and too far: "Tink" sound and diamond is long gone, along with the money I spent on it. (Yes, I had adequate safety gear, so no damage to me.)

I believe that you want to rotate your grinding stone in the opposite direction from the rotation of the part you want to grind. BUT, check with that expert mentioned above.

--ShopShoe

 

[Jonathan Coates]

I'll keep trying it with different stones, speeds and feeds, for the moment the collet thing is out of the chuck and on the mill ready to drill the holes. Just need to fix the mill as the auto feed crashed into the end of the travel mashing the gib screw up and forcing the gib too far in. The limit switches are now on order to prevent me from breaking the thing any more.
FYI the Tom Senior mill runs out of travel when the spidle is about 300mm from the end of the T slots, so what looks like a lot of acreage is actually a small work area with extended clamping bits at the end. Similarly if I need more than about five inches of Y travel I have to do it in stages by unlocking the dovetail and sliding the vertical head in or out accordingly. It will cover quite a bit in Y travel but loses some time and messes with the DRO when I move the head. I plan to get a small DRO style readout on the dovetail so that I can use an offset to the Y axis DRO to get back to where I was. Things like drilling holes on a PCD are currently done by finding centre, drilling half the holes then offsetting the head and repeating for the other half. Not quite the best way, but it works.