DIY collet chuck questions

[martik777]

I made my nut without an internal groove and it works just fine. I cut the 1.5mm thread by replacing the 20t stud gear with a 26t on a South bend 9A, but if you are making your own chuck just use imperial threads.

The nut is almost the same price as an entire collet chuck - check out ctctools - approx $17

 

[Craig_J]

Are you interested in making another one? I have the same lathe. Name your price!

Even if I charged a cheap labor rate, you probably wouldn't want to pay for my time! I am enough of a beginner that I work pretty slowly. It was only the second or third project on my lathe, and I sweated the details to get it right. Thanks for the complement, though. Besides which, on this part I really think you should make it to fit your machine's spindle exactly. It wants to fit snugly enough to maintain good repeatability. Although your G0602 may be nominally the same, I'll bet it's not the same to <.001! And because you make the collet end with the chuck screwed onto the spindle, this compensates for any spindle eccentricity. I suspect this is why you don't see someone selling them commercially.

 

[martik777]

I have thought about making my own collet holder for my 1 3/4-8 spindle nose. A problem to address is how to gauge the internal thread to make sure it fits the spindle nose. Obviously, you wouldn't remove it from the machine to try it. I suppose one could buy a bolt that size but the sloppy fit of a commercial bolt may not give the class of fit required on the spindle nose.

Make a male thread out of scrap to test the fit. I didn't have anything large enough when I made mine so I used some wood with a 1/4 layer of bondo. The hardened bondo cuts much cleaner than wood. The threads do not need to be a precise fit, it's the register than maintains repeatability.

Just do it, it's not that difficult.

 

[Ebel440]

Another option instead of making the oblong hole in the nut is to make a grove and then use a retaining clip with an oblong hole. Like a circlip with the hole ground oval this is what some of my er collet holders for milling use it is replaceable and harder then aluminum

 

[cascao]

I have done mine too. (Flange type)
It took more time to do the finish than the part itself.
+ 1 in buy the nut (Really, buy 2 or 3 nuts to speed up collet changes)
And definitely, go to steel. Aluminium and threads doesn't work well when you use the thread frequently.
Here, the dimensions you need.

View attachment ER Collet data.pdf

 

[Carlos SA]

What material do they usually make collets out of?

 

[Uglydog]

I've been looking forward to making a collet holder for my Logan 10".
However, based on the amount of runout I had on my spindle I hadn't started (my existing spindle has worked really well with my 4jaw).
I picked up a new/used spindle, hope to get her in next week.
Then I'll move on the collet holder.
However, I'm not sure that I want to make collets.
There are alot of different used collets available.
Some cheap and plentiful, others not.

I'm not marketing Hardinge but this is an interesting pdf which lists alot of options and specs.
http://hardingeus.com/usr/pdf/collet/2348.pdf

Additionally, I found this an interesting document.
Workholding Collets And Factors That Affect Grip Force
http://www.productionmachining.com/articles/workholding-collets-and-factors-that-affect-grip-force


Daryl
MN

 

[Craig_J]

However, I'm not sure that I want to make collets.

MN

Collets have complicated slots and are precision ground and hardened alloy steel. I can't imagine wanting to do the work to try to make one myself, or that it would be as good as a commercial collet. I have a 23 piece set of ER40 collets (with an R8 holder) that I bought from tools4vcheap.net for about $150. They are definitely not junk and seem to be very well made and nicely finished. This comes out to less than $10 per collet. The best ones are European and cost 3x as much. If a person only wanted the best, they could buy a few sizes to start (1/4, 3/8, 1/2, 3/4) and add other sizes as needed. After about 18 months, I have used all of sizes that are multiples of 1/8 but many of the in-between fractional sizes are still in their original shrink-wrap. While I have a commercial MT4-ER40 holder and the threaded spindle holder that I made for the lathe, I most use them in the mill. I don't own any R8 or 5C collets. Since I only use one machine at a time, the one set of ER40 collet serves both machines.
Craig

 

[martik777]

If you want to get started with collets on a budget, get the Full 15pc ER25 metric set on ebay for $42. I use them on both my mill and South Bend 9A. Didn't see much use in ER40 since my spindle is only 3/4"

 

[strantor]

Are you sure you can't cut 1.5mm threads? Some smart guy around here just might be able to give you a work around if you tell us what lathe you have. It may end up easier than fabricating a nut.

I have read accounts of hobby machinists making ER chucks from aluminum, so it should work for light use. Getting a piece of steel or cast iron might be a better idea if you plan to do a lot of collet work.

Try this link for ER dimensions http://www.takayama-shoji.co.jp/rego/pdf/13_technical_information.pdf

Sorry it took so long to reply to this; It's been hectic. I never considered the possibility of cutting metric threads on my lathe; I just accepted it as something not worth pursuing, but you inspired me to look into it.

My lathe is a Logan 9". It has a QCGB and an 8TPI lead screw. I've devoted some hours to figuring out the gearing and how everything works; I can assure you I don't "get it" 100%, but here's what I've come up with:

I think that by replacing my 48T gear going into the QCGB with a 74T gear I can cut a 1.498MM screw (0.13% error) with my QCGB set to 11TPI.

I came to this conclusion by playing around with my spreadsheet (see attached).

If you'd like to check out my spreadsheet and sanity check me, here's how my lathe is set up:



I have no other gears other than what's shown.
Here's my QCGB chart:



I realize a 74T gear is not part of any standard gear set, by any lathe manufacturer, anywhere in the world, ever, but I think it should be a breeze to print one out in my 3D printer in Nylon645. I've done the math on the gear and drawn it up in Sketchup. My nylon has been sitting for months and needs to be dried out before use, you have time to save me from a foolish move. Here's a pic, source file attached (rename 74T logan gear.pdf to 74T logan gear.skp):



I've wondered if 3D printed gears will stand up to use in machine tools; I guess now is a good time to find out. If it works out, I might just print the 127/100 tooth gears that I really should be using (although my spreadsheet doesn't seem to like those numbers much - probably an error in on my part).

If any of you old salts have a better suggestion, I'm all ears.