Author Topic: A cautionary tale for those that use a screwed on chuck on a RT  (Read 4094 times)

Offline Stuart

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A word of caution with the use of adaptors to hold a threaded chuck on to a RT

note this will not happen if you mill on the inside of a bore its milling on the outside that is the big problem


no machines were harmed nor any operators or pets in this vid and its totally blood free

list=UUw3UZn1tcVe7pH3R6C3Gcng

Adam called it before it happened don't forget to duck

Stuart
My aim is for a accurate part with a good finish

Offline mcostello

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Re: A cautionary tale for those that use a screwed on chuck on a RT
« Reply #1 on: August 22, 2014, 04:51:04 PM »
If He would have had the cutter on the other side of the blank, it might have screwed it tighter but it would not have come off.

Offline Stuart

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Re: A cautionary tale for those that use a screwed on chuck on a RT
« Reply #2 on: August 22, 2014, 05:10:38 PM »
Sorry you are incorrect the cutter will still unscrew it

Where Adam has the cutter the edge to work is going away from him therefore the job unscrews, with the cutter on the left side ithe cutter to work is towards him so it will still unscrew

The only safe way is a left hand cutter and reverse the mill

If he was working in a bore it would tighten the work with normal cutters

Read the comments on the vid and Adams answers

Stuart
My aim is for a accurate part with a good finish

Offline Bearcar1

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Re: A cautionary tale for those that use a screwed on chuck on a RT
« Reply #3 on: August 22, 2014, 09:11:09 PM »
I wonder how long it took him to clean out his trousers after that event? Lol!  I like his style and his way of approaching a piece….


BC1
Jim

Offline crueby

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Re: A cautionary tale for those that use a screwed on chuck on a RT
« Reply #4 on: August 22, 2014, 10:08:26 PM »
My four jaw chuck has a slot around the rim near the spindle side thay can be used with a hold down on the table to prevent this. The 3 jaw does not, wish it did.

Offline PStechPaul

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Re: A cautionary tale for those that use a screwed on chuck on a RT
« Reply #5 on: August 23, 2014, 08:45:51 AM »
Test post. I had written a rather long post and when I tried to submit it, it gave me a "Forbidden" error and all was lost.

Basically I was saying that it was not the chuck that came unscrewed from the table, but the adjusting nut from the bushing. It might have been good to have drilled and tapped some holes where he drilled them for the spanner, and used set screws to keep it from unscrewing. Also, without such positive locking, the work could have unscrewed a little bit between each milling operation, and the angular positions might have lost some accuracy.

For my 6" rotary table, I'd have to remove my 4" 3 jaw or 6" 4 jaw chucks from their threaded adapter plates, and bolt them to the table with the T-slots. But for small work I have a mini-lathe chuck with an MT2 taper that might work on the table, but I think it screws onto the adapter, and would need to be secured. My 4" chuck has a spindle clamp so it can be used in reverse. I need to make one for my 6".

OK, I'm saving this first. That'll probably guarantee I won't get the dreaded "Fobidden PHP" message!

Got it again! It might be because of the emoticons? Seems to be...

Here's the message:

Forbidden You don't have permission to access /index.php on this server.
« Last Edit: August 23, 2014, 08:59:15 AM by PStechPaul »

Offline Stuart

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Re: A cautionary tale for those that use a screwed on chuck on a RT
« Reply #6 on: August 23, 2014, 09:19:33 AM »
Yes Paul it was the lock ring in this case , I to thought about drilling the spanner holes deeper and fixing the part to the arbour that way , but hindsight is a powerfull tool.

but I am glad you have your chucks bolted down as I do

A chuck on a threaded adaptor milling on the outer could unscrew in the same manner but don't ask me how I know it's a fact , but I learnt many years ago that a mill head can move 10degrees out of tram quicker than I could turn off the mill with the Oh S..... Switch


Maybe I got the thread title a bit misleading

But we have had posters advocating using screwed chucks mounted to arbours on a RT but with no warning that they can unscrew in use ,

Stuart
My aim is for a accurate part with a good finish

Offline PStechPaul

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Re: A cautionary tale for those that use a screwed on chuck on a RT
« Reply #7 on: August 23, 2014, 11:30:25 PM »
Dang! That PHP "Forbidden" error trashed my post again. I think it was because I used an image.

But what I was saying is that perhaps some chuck jaws can be made that will fasten to the T-slots of the rotary table. Or purchased. And I found these:

http://www.toolmex.com/products/browseresults.aspx?CatID=2235&Parent=

I tried to embed the picture using this URL:
http://www.toolmex.com/images/ecomm_images/MasterProducts/medium/7-645.jpg

(even the preview causes the "forbidden" message)

More discussion:
http://bbs.homeshopmachinist.net/threads/44785-How-is-the-Chuck-Mounted-to-Your-Rotary-Table
http://www.chaski.org/homemachinist/viewtopic.php?f=43&t=99262

Offline kev

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Re: A cautionary tale for those that use a screwed on chuck on a RT
« Reply #8 on: October 13, 2014, 03:53:16 PM »
If he mounted the chuck at right angles and fed in from the right with a ball end cutter it would have tended towards tightening. Or I guess cheaper but with more setup time bolt it down to the table with clamps would have been a safe option

on small pieces I tend to make oversize then go round it plunge cutting so forces are equal in each direction, can either finish on the lathe or if its not round with a very light cut in the mill