Bell mouthed chuck

[Brian Rupnow]

I went so far as to get my Toolpost grinder from Little Machine Shop out and set it up just to see what was what.--It won't work. The grinding wheel is 2 1/2" in diameter, larger than the spindle thru hole. If I took the guard off and machined a spindle extension to be used with a smaller diameter stone, it could work---maybe. I don't trust myself to make a spindle extension that will fit the grinder well enough to remain perfectly concentric with the long axis of the grinder spindle.

 

[Richard Hed]

I went so far as to get my Toolpost grinder from Little Machine Shop out and set it up just to see what was what.--It won't work. The grinding wheel is 2 1/2" in diameter, larger than the spindle thru hole. If I took the guard off and machined a spindle extension to be used with a smaller diameter stone, it could work---maybe. I don't trust myself to make a spindle extension that will fit the grinder well enough to remain perfectly concentric with the long axis of the grinder spindle.

Do you have a Dremel? They don't cost all that much.

 

[almega]

When I did mine, I just used my little Dremmel in a holder that fastened into a tool holder. It is nothing very sophisticated but it is solid and it worked.

 

[Brian Rupnow]

I have a crappy little Dremmel clone, that is about 95% plastic.

 

[almega]

I have a crappy little Dremmel clone, that is about 95% plastic.

My Dremmel is mostly plastic. It is a cheaper version that I have had for almost 40 years. It won't win any beauty contests but it still spins and while it can't take aggressive cuts, I put a reasonable stone in it and it worked to straighten out the jaws on my old chuck. It is the definition of a tool, "a device or item suited to complete a defined task", and it did the task as yours may well do likewise.

 

[a41capt]

I use a dremel hand piece with flexible extension in a boring bar BXA holder. Works like a real small diameter grinder. I also have a 1/4” collet electric die grinder with a holder on it that fits my standard BXA tool post. I use either/or depending on my mood, and they work a treat on grinding and cutting off cast iron rings.

John W

 

[Charles Lamont]

I don't trust myself to make a spindle extension that will fit the grinder well enough to remain perfectly concentric with the long axis of the grinder spindle.

It does not need to be perfect as you can dress the grinding point in situ. For my chuck I have used a die grinder in a toolholder made from materials to hand:
Charles Lamont's Model Engineering Pages -> IQC Toolpost -> Toolholders

 

[Steamchick]

Beautiful work Charles. I bet it is all as precise as one may expect.
Puts my rough jigs to shame!
K2

 

[ajoeiam]

It does not need to be perfect as you can dress the grinding point in situ. For my chuck I have used a die grinder in a toolholder made from materials to hand:
Charles Lamont's Model Engineering Pages -> IQC Toolpost -> Toolholders

Hmmmmmm - - - quite the collection of tool holders you have.

I'm sorta thinking you like making things for your tools maybe even more than you like using your tools - - -yes?

 

[Charles Lamont]

Making more tools makes it easier to make more tools, and it is easier than making models 'cos the bits are full size.

 

[animal12]

Nice Job Charles !! Did you have the Multifix tool holder in the back of your mind while designing your tool post ?
I currently have a QCTP ,if I had the $ I'd have a Multifix . Your tool pose has got me thinking . thanks & nice work .
animal

 

[ajoeiam]

Making more tools makes it easier to make more tools, and it is easier than making models 'cos the bits are full size.

Sorry - - - - but your response is really pegging the chuckle meter!!!

My projects - - - well a 3m or 10' cube is sorta on the small end - - - ;-( !

 

[Charles Lamont]

No, animal12, I didn't. I wanted an improvement on the ordinary crude toolpost and clamp, but it did not take long for me to decide that I really could not get on with a 4-tool turret. I looked at the improved one in The Model Engineer's Workshop Manual by George Thomas. I still did not like that, but did take from it his discussion about the repeatability of the indexing.

My own ideas for a quick-change toolpost were a long time in gestation. I still have my initial sketches. They are undated, but were started about 25 years ago. Some of the CAD drawings are dated 2001, and the web pages have been up so long that the images are scans of film prints.

But, none of this is helping Brian with his chuck jaws.

 

[Brian Rupnow]

I'm not going to try to regrind my chuck jaws. I picked up another short design contract today, and a day and a half's work will buy me a new 6" 3-jaw chuck. It won't be a total walk in the park, because I will have to machine a backplate for the chuck to attach it to my lathe spindle. The contract comes at a good time, because I'm suffering from the mid-winter "blahs". I'm still dicking around making the perfect sparkplug, but that will take a back seat for a while.---Brian

 

[almega]

It is always nice to have some marketable skills, eh? Helps to pay for our habits.

 

[Brian Rupnow]

Today I bought my new 6" chuck. It didn't have any backplate, and I thought I might have to make one. Surprise--Surprise--the backplate off my old chuck bolted tight up to it. No muss, No fuss. I chucked up a piece of 1" hardened and ground shaft and turned the lathe on.--No visible wiggle. I mounted my dial indicator on it, and depending on which of the three "key ports" I used to tighten it, I got 0.005" total indicated runout, 0.005" total indicated runout, and 0.0035" total indicated runout. I marked the "key port" that gave 0.0035" total indicated runout. There are three studs that hold the backplate to the spindle, which gives three possible ways to mount the chuck, and I will repeat my tests in all three positions to see if the runout gets any better. I tried to slide a 0.0015" feeler gauge in between each individual jaw and the piece of steel they were holding, and it would not slide in any place. On my old chuck the feeler gauge would slide in under one jaw about 1 1/4" and under the second jaw about 1/2" and wouldn't slide in under the third jaw.

 

[Vietti]

Maybe try loosening the bolts holding the chuck to the back plate slightly and tap the chuck into a true position, poor mans adjust true.

 

[Charles Lamont]

I suggest checking it with a range of diameters. There may well be differences, in which case a compromising position may be best.

 

[Brian Rupnow]

Today I had more time available to play with my new 3 jaw chuck. When first installed, I mounted a dial indicator on the lathe bed and the business end against the piece of 1" hardened and ground material held in the vice jaws. Depending on which of the 3 "chuck key holes" I used to tighten the jaws, my total indicated runout was 0.005" then 0.005", then 0.0035". I used a punch to put an identifying mark on the chuck key hole that seemed to give the least amount of runout when I used it to tighten the jaws. The chuck adapter plate attaches to the spindle with three M10 studs at 120 degrees apart. Today I unbolted the chuck adapter plate and turned the entire chuck and backplate clockwise by 120 degrees and then retightened the studs. I may have hit the jackpot with this move, because my total measurable runout fell to 0.002". This is better than I ever got with the original chuck, which had visible runout of 0.0035". I used my vibrating marker to put match marks on the spindle and on the backplate so if I ever remove the three jaw chuck I can put it back on in the same rotational aspect to the spindle flange.

 

[clockworkcheval]

Nice, Brian! An old hand told me that whenever he has to do something precise in the 3-jaw chuck he will slowly tighten each jaw in several passes while tapping the chuck with a light copper hammer.