Mounting a collet chuck on a backplate !

[BaronJ]

Hi Guys,

In this series of posts I will be making a backplate for my lathe in order to mount an 80 mm ER32 collet chuck.

Collet Holder.png

This is the chuck that I've ordered. Delivery expected 8 or 9th of December. I've already obtained a slice of 100 mm round bar 30 mm thick, although I could get away with 25 mm.

Pictures to come !

[BaronJ]

Hi Guys,

I've started to machine the piece of 100 mm round bar for the backplate. I put it in the four jaw chuck and centered it up. It was not truly round, it has flat on one side, not much about 8 or 10 thou. But it doesn't half cock up trying to get it centered properly. I also made a slight booboo cutting it off the bar. As it happens it won't make a big difference when its finally machined.

04-12-2024-001.jpg

This is the piece that was cut off the bar. Its EN1 material. I was warned that it will rust in very short order if I don't protect the surface.

04-12-2024-003.jpg

This is it mounted in the four jaw and centred up, ready for facing off.

04-12-2024-006.jpg

Knowing that I need to bore and thread the centre, I made a gauge for the correct diameter for a 1.125" inch X 12 TPI thread. I will use this to ensure that the centre hole is bored to the right size. I will also recheck it tomorrow when the piece has cooled down. It got quite warm when being drilled.

04-12-2024-002.jpg

This is after facing off and drilling. I just put an 8 mm hole through first and then followed with a 25 mm hole with a blacksmiths drill.

04-12-2024-004.jpg

here I've just finished boring the hole to 26.5 mm. You can see the booboo where I started to cut the slice off on the bandsaw, then realised that I had made a measurement error.
To save you guessing, I mixed up mm and inches, using the wrong side of the scale.

That boring bar was the one that came with the set of insert lathe tools I bought recently.

04-12-2024-005.jpg

Any way the plug gauge is a nice push fit, if I can get it out ! It went in with a firm push but the work was still quite warm.

Next job is threading.

[kafie1980]

I will assume once you have finished the internal 1 1/8" x 12TPI BSW thread you will mount it directly onto the spindle nose and machine the rest in place to ensure concentricity.

Are you going to skim the rear face of the ER collet chuck?

[Dave J]

I will assume once you have finished the internal 1 1/8" x 12TPI BSW thread you will mount it directly onto the spindle nose and machine the rest in place to ensure concentricity.

Are you going to skim the rear face of the ER collet chuck?

I would have thought mounting it as accurately as possible and lightly skimming the taper once locked in place.

To skim the rear face would mean having a 100% true collet and piece of bar to be perfectly accurate, then a perfectly true chuck to mount it in.
Then there are the compiling errors as you have 3.

I'm not sure, maybe your idea is different to machine it?

Sent from my SM-A235F using Tapatalk

[BaronJ]

I will assume once you have finished the internal 1 1/8" x 12TPI BSW thread you will mount it directly onto the spindle nose and machine the rest in place to ensure concentricity.

Are you going to skim the rear face of the ER collet chuck?

Hi Kafie,

Yes that is the idea, then machine a register on the backplate to match.

Kafie I know that you have a super 7, I can't remember how many teeth the first gear under the tumbler should have, I think it should be 24 but I've changed it that often to 32, 33 & 34 tooth ones in order to cut Metric and BA threads, and of course misplaced the chart.

Thanks:

[BaronJ]

I would have thought mounting it as accurately as possible and lightly skimming the taper once locked in place.

To skim the rear face would mean having a 100% true collet and piece of bar to be perfectly accurate, then a perfectly true chuck to mount it in.
Then there are the compiling errors as you have 3.

I'm not sure, maybe your idea is different to machine it?

Sent from my SM-A235F using Tapatalk

Hi Dave,

I do have an ER32 chuck on an MT2 mandrel that I use in the spindle and a bit of 12 mm precision ground bar with collets to suit. But I do take your point, each item adds to the possible error.

What I did with the 125 mm three jaw was to turn the backplate register about 10 thou small, put a piece of precision 20 mm bar in the chuck jaws and using a dial gauge tap the chuck until it read zero all the way round. Then tighten the mounting bolts.

OK it will only be spot on at 20 mm, but it did reduce the runout on smaller diameters. I think, if I remember correctly that originally the chuck runout was about 3 thou.

[kafie1980]

Kafie I know that you have a super 7, I can't remember how many teeth the first gear under the tumbler should have, I think it should be 24 but I've changed it that often to 32, 33 & 34 tooth ones in order to cut Metric and BA threads, and of course misplaced the chart.

NO idea how I missed replying to this.

Which gear are you exactly referring to in this image:

Myford tumbler setup.JPG

Gear no. 3 in that image is a 30T gear on the spindle.

Tumbler reverse gears (no. 2) are made of tufnol and are 28T and 30T.

Tumbler sleeve gear no. 4 is a 30T gear.

On the Tumbler sleeve gear no.4 from factory it comes paired with a 24T gear. But we often replace that with a 20T for imperial threads and 21T for metric threads.

There is also a fine feed special tumbler gear (single piece) that replaces entirely gear no. 4 and is a 12T/30T combination for super fine feed.

[BaronJ]

Hi Kafie, Thank you for your reply.

My Myford is a Super 7 with a gearbox and power cross feed.

Both tumbler gears are Tufnol and I believe are both are 28 teeth. Tumbler sleeve gear no. 4 is currently a 33 tooth gear. That is the one that I keep changing to get Metric and BA threads plus others. I do have a 24 tooth gear to replace the 33 tooth one. With the correct gear I can select 12 tpi directly from the gearbox.

I will get a picture of mine since it looks to be slightly different to yours.

The collet holder turned up this morning. It was well packed and fully ground all over. The collet nut turns very smoothly and is not loose on the threads like my other ER chuck. I have a very good feeling about this one !

Thanks again:

[kafie1980]

Mine is just a S7 + PXF and no QCGB version. I waited almost a decade to find an honest machine that I liked and that was within my budget.

I double confirmed with the manual (parts diagram) that those tumbler reverse gears made of Tufnol are indeed a 28T and 30T combination. I believe this is intentional to take up the slack in the drive train when reversing the tumbler.

I have seen the QCGB versions (I have a Myford restorer near me that has done about 50 lathes by now and in his shed I have seen almost every accessory/attachment MyFord and other 3rd parties made) and I know their change gear quadrant assembly (aka banjo assembly) is different. I have a manual for the QCGB kicking around somewhere in digital form and looked at it once out of curiosity.

I figured it was no longer a quick change gear box if I still need to change gears to flip between metric and imperial

The import tooling manufacturers do a great job with the grind and finish on the products but their QC does fall through the cracks at time. You do want to clock it to ensure concentricity.

[BaronJ]

Hi Kafie,

I did check the Tufnol gears they are 28 and 30 ! Yes I did count them . I also found the chart I thought I had misplaced, it had slipped over the back of the drawer and down inside the cabinet.

Pictures below.

06-12-2024-013.jpg 06-12-2024-012.jpg

I hope that the chart is OK to see, it looked small to me. All I do to change from imperial to anything else is to change the tumbler sleeve gear. Whilst its in my mind the gear size difference explains why I get tight threads when cutting towards the tailstock.

Now pictures of the collet chuck !

06-12-2024-007.jpg

It came in this plastic screw thread box. I right pain to unscrew the top. That is destined for the plastic salvage bin !
06-12-2024-008.jpg 06-12-2024-010.jpg 06-12-2024-009.jpg

The chuck was packed in an oily plastic bag, well tucked into the collet nut. I'm quite impressed by the finish on this chuck. The mounting holes are M6 threaded, so without drilling them out it looks like I will be bolting it from the back. I've yet to measure the register but it looks to be about 50 mm or so.

06-12-2024-011.jpg

I got the backplate threaded and the register bored to size at 31.7 mm. I have a MT2 chuck mounting that fits perfectly ! So I'm very pleased with that. Just need to take a skim off the face before turning it down to 80 mm.

[BaronJ]

Hi Guys,

09-12-2024-16.jpg

Having got the backplate threaded and the register machined, I've turned it around and now need to get it down to size. 80 mm with a 55 mm register for the collet holder.

09-12-2024-15.jpg

This the backplate screwed onto the lathe spindle. I ended up putting it back in the four jaw because it wouldn't screw onto the spindle register. I actually only had to take about 15 thou more off the inside to have it screw on properly.

09-12-2024-14.jpg

This is the live tailstock center that I used in order to test the threads. When I measured the register diameter on this and compared it to the lathe spindle there is 10 thou difference, it is that much smaller. The threads are spot on.

Next job is to turn the collet chuck register and drill the mounting holes.

More pictures next time.

[kafie1980]

09-12-2024-14.jpg

This is the live tailstock center that I used in order to test the threads.

This is an interesting live center that I have seen in recent years and I have seen 4 jaw chucks mounted on to them and held in the tail stock.

The only circumstances that I have seen these in action on bigger lathes is with an independent 4 jaw chuck to hold heavy work that would be heavy for a cone point live center and we have the added benefit of dialing in the runout or even offsetting the work for eccentric turning.

How useful have you found it so far? Especially with the threaded mounting of the chuck?

Wanted to know before I splash out my hard earned money. [emoji846]

[BaronJ]

Hi Kafie,

I must have had that Myford live spindle for about ten years. In all that time I've only used it once ! Until now, and then only as a gauge reference for the 1.125" x 12 threads and register, even that was under size. Its proved to have been an expensive waste of money. I would have been better off making a reference nose. But this is where experience counts...

At the time I bought it I had never turned a thread successfully, its taken a long time to understand exactly what is needed to turn threads properly. I still use taps and dies for some jobs, but they tend to be small metric or BA ones.

So my advice is "Don't even think about it" there are more useful things that you can spend your hard earned on.

[kafie1980]

Thanks for sharing your opinion on the revolving live center chuck gizmo.

You are right about threads.

I actually have a Myford nose plate for a 6” rotary table from Warco (UK) and the spindle nose register needed a quick thou off and the threads were slightly over and I had to work the threads with some grinding paste.

When I contacted them they told me they checked it against their reference chucks.

All I can say is that even production setups get it slightly wrong.

[BaronJ]

Hi Kafie,

I don't think any of them are as good as being able to measure your own spindle. I've measured mine at 32.640 mm, whilst the live spindle one is 32.623 about 10 thou small.

I think that its only a nominal measurement with a few thou tolerance. But if you mic it and lock the mic you can feel the size difference.

From new the 6" inch four jaw was very tight on the register, so whilst I had the chucks off the spindle I removed the jaws and screwed it onto the spindle backwards.

This gave me access to the inside of the register bore on the chuck body. Surprisingly I found that there was very tiny specs of rust in the pores of the cast iron. Using a X20 loupe you could see what looked like crystals of rust. I gave it a spinning wipe with some of that green scotchbrite, which polished the surface but made little difference to the size or the rust. I ended up taking a couple of thou out of the bore. I also used a HSS toolbit rather than the carbide insert.

It now screws on nicely exactly the same as the original three jaw. I've given it a rub with some grease, which I hope will stop any more rust crystals.