Author Topic: Rigidity of a Mill  (Read 135 times)

ddickey

Rigidity of a Mill
« on: March 19, 2019, 05:55:49 AM »
What is the single most important component that makes a mill rigid?
I know it is combination of things as simple as weight, width of ways, spindle bearings.

PJB

Re: Rigidity of a Mill
« Reply #1 on: March 19, 2019, 08:11:21 AM »
I would add the more articulation it has the less rigidity usually.   Eg a bed mill vs knee mill.
So tell me - What's your fair share of everything I've worked for??? Nothing?  Correct answer!
I cordially invite you to join me in starving and beating our govt back to it's honeymoon physique.

4GSR

Re: Rigidity of a Mill
« Reply #2 on: March 19, 2019, 08:52:13 AM »
The amount of cast iron that goes into making a good solid mill.

A good example I always used a 2J Bridgeport mill that weighs around 2200 lbs. and a 9-J Gorton mill that weighs in at around 3400 lbs.  The Gorton can snap off a 3/4" end mill and just make a thump, like it was not there, and doesn't affect alignment.  If you broke a 3/4" end mill on a Bridgeport mill, you would know it, and be injured from the breakage.  It also knocks the head out of alignment.  Of course this is not a realistic comparison.

Another thing to consider is how rigid is the head.  Does it chatter/vibrate when taking heavy cuts?  This vibration generally transfer into the base casting too.

Ken

chips and more

Re: Rigidity of a Mill
« Reply #3 on: March 19, 2019, 11:39:51 AM »
Thatís a good question. I guess run a little Sherline mill or the like. And then run a floor model milling machine. I think you will quickly learn about difference in rigidity.

ddickey

Re: Rigidity of a Mill
« Reply #4 on: March 19, 2019, 11:50:59 AM »
I have a knee mill (PM935TS). Never used a bench top. Upgraded from a round column Grizzly knee mill. I thought the difference would be great but it is not. I believe that the spindle/quill is probably the greatest cause for rigidity or not. If that makes sense. I like my mill but I think R8 spindles are limited to what they can do. Not that I need anything more just thought I'd start a conversation. Probably would've gone with the Cat. 30 spindle option if I knew about it before I bought the mill.

woodchucker

Re: Rigidity of a Mill
« Reply #5 on: March 19, 2019, 12:29:22 PM »
I have a knee mill (PM935TS). Never used a bench top. Upgraded from a round column Grizzly knee mill. I thought the difference would be great but it is not. I believe that the spindle/quill is probably the greatest cause for rigidity or not. If that makes sense. I like my mill but I think R8 spindles are limited to what they can do. Not that I need anything more just thought I'd start a conversation. Probably would've gone with the Cat. 30 spindle option if I knew about it before I bought the mill.
if you think r8 is limited, try an MT2.. my Clausing 8520 has an MT2 and it is limiting.

Jeff
Clausing 8520   SB Model 9a - power hacksaw, Milwaukee band saw in a table.  Delta Rockwell Surface Grinder (not online yet .. being rebuilt where am I going to stick this)
For pics: https://imgur.com/user/woodchucker/posts

Carpenter84

Re: Rigidity of a Mill
« Reply #6 on: March 19, 2019, 12:30:26 PM »
I've heard that before... Why is the R8 less rigid than a cat. # spindle?
Shawn

First 9x42 column mill,
Enterprise 10x28 lathe,
Ko Lee 6x12 surface grinder,
Airco dip/stick 160 welder,
Fully stocked wood shop.

woodchucker

Re: Rigidity of a Mill
« Reply #7 on: March 19, 2019, 12:36:33 PM »
I've heard that before... Why is the R8 less rigid than a cat. # spindle?


just by design.
You have a lot more meat in play with the cat s.
I believe the taper on the cat is alot more in contact than the R8 is. The r8 collet walls are super thin. The CAT is super heavy.
Just look at the difference.
The CAT generally has Mill holders (weldon).. or could have a collet, (more like ER) mostly or other similar. 

Jeff
Clausing 8520   SB Model 9a - power hacksaw, Milwaukee band saw in a table.  Delta Rockwell Surface Grinder (not online yet .. being rebuilt where am I going to stick this)
For pics: https://imgur.com/user/woodchucker/posts

Carpenter84

Re: Rigidity of a Mill
« Reply #8 on: March 19, 2019, 12:38:30 PM »
Alright, I buy that.
Shawn

First 9x42 column mill,
Enterprise 10x28 lathe,
Ko Lee 6x12 surface grinder,
Airco dip/stick 160 welder,
Fully stocked wood shop.

ddickey

Re: Rigidity of a Mill
« Reply #9 on: March 19, 2019, 12:55:06 PM »
I was told that cat 30 was no better than R8. I can't dispute that as I've never run a cat 30 spindle. I know you can buy beefy R8 spindles that come with extra bearings I think.

4GSR

Re: Rigidity of a Mill
« Reply #10 on: March 19, 2019, 01:17:05 PM »
I know you can take out the spindle of a 2J head, replace the spacers with two more bearings for a total of 4 or two sets of matched "DU" arrangement and go back together.  That's about as rigid as you can get on a R-8 spindle.
The NMTB 30 spindle can be much more rigid than a R-8 in terms of driving an adapter, end mill holder, etc. It also has driving keys on the face of the spindle for larger accessories (specially made) for heavier cutting on a mill equipped with an 30 taper.  The disadvantage is the lack of accessories available for the NMTB 30 spindle as there is for the R-8 spindle.  The little dog point set screw on the R-8 is not for driving the collet.  It's just there to hold the collet or adapter long enough to get the draw bar threaded into it and tighten.  I've taken mine out and tossed it as far as I could throw it in the yard to never be seen again!
Ken

Carpenter84

Re: Rigidity of a Mill
« Reply #11 on: March 19, 2019, 01:58:45 PM »
A: are you suggesting you can change the spindle from an R8 to a different taper in a 2J head?

B: would another set of bearings potentially quiet a noisy spindle during an interrupted cut?

C: why does no one like the R8 "dog"?... Poor little guy...
Shawn

First 9x42 column mill,
Enterprise 10x28 lathe,
Ko Lee 6x12 surface grinder,
Airco dip/stick 160 welder,
Fully stocked wood shop.

woodchucker

Re: Rigidity of a Mill
« Reply #12 on: March 19, 2019, 02:21:01 PM »
A: are you suggesting you can change the spindle from an R8 to a different taper in a 2J head?

B: would another set of bearings potentially quiet a noisy spindle during an interrupted cut?

C: why does no one like the R8 "dog"?... Poor little guy...


I would like the R8 over the MT2.. more options available to me.
Not as expensive as CAT..
Jeff
Clausing 8520   SB Model 9a - power hacksaw, Milwaukee band saw in a table.  Delta Rockwell Surface Grinder (not online yet .. being rebuilt where am I going to stick this)
For pics: https://imgur.com/user/woodchucker/posts