Thread: rigidity problems with bridgeport clone

Hi,
I'm not sure how big your machine is, power or weight wise, but I would think a 100mm dia face cutter would be too big for what is really not a very rigidly designed machine. As for the endmill, what sort of depth are you trying? Are the gibs snug? With chatter one of the fixes can be as easy as a faster feed speed.....but not alway.

Cheers,
Ew

Just a random thought, but what are your bearings like?

Michael

Originally Posted by the fabricator

...

any ideas?? it is giving me a headache..

Sounds from the symptoms you've described like you might be machining hardened or really tough steel of some type (or welds maybe, given your name ) - does this happen on known mild steel too ?

plain mild steel plate is what im cutting, did a bit of work on some 4140 ( made a fly cutter for it )

I understand the cutter is probably too big and I'm purchasing another smaller one, say 50mm or so. the 100mm cutter was free so that's why I gave it a shot.

all gibs are tight and I have locked the other axis' when not using them

and as for bearings, from what I can tell they feel ok. how would one go about checking them properly?

Originally Posted by the fabricator

... as for bearings, from what I can tell they feel ok. how would one go about checking them properly?

I'm not an expert but I'd start by popping off the belts and then rotating the spindle by hand to see if it felt notchy or gritty. See also whether the spindle has any movement in it (can wobble around or move up and down). With the belts off check that the motor bearings are smooth as well.

To me it sounds like there is some play between the cutter and the material that shouldn't be there. If the work is well secured, the jibs tight or locked I would next suspect that the spindle is not behaving.

Michael

If I had to guess, my first guess would be you are in reverse.

Stuart

If your mill head is varieble speed you need to reverse the motor when changing from hi to lo range.

Originally Posted by Michael G

I'm not an expert but I'd start by popping off the belts and then rotating the spindle by hand to see if it felt notchy or gritty. See also whether the spindle has any movement in it (can wobble around or move up and down). With the belts off check that the motor bearings are smooth as well.

To me it sounds like there is some play between the cutter and the material that shouldn't be there. If the work is well secured, the jibs tight or locked I would next suspect that the spindle is not behaving.

Michael

Just a quick one. Do you know of the machines heritage? Can you contact former owners? If every thing else is rigid can only be lumpy spindle brgs no pre load etc etc. or bent internally.Is it a m taper spindle they get awful tight and seen harm done trying to get a stuck chuck cutter loose. Just 0.02 cents worth Good Luck with it I run a Bport head with a 12 inch holden fly wheel single point cutter no probs but does only light cuts it has a no2 morse spindle.John.

Originally Posted by Stustoys

If I had to guess, my first guess would be you are in reverse.
Stuart

That's exactly what I was thinking! I just felt a bit more uncomfortable sayng that to a stranger than Stuart did....

a KR3000 should handle a 100mm face cutter with ease.

My money is on Stuarts guess. Check your gear (low gear (backgear) run the machine in reverse, high gear run the motor forward.

Best of luck

Also, it'd be a 3 phase motor from factory - have you verified it's wired in correctly?
cheers
Jon

Originally Posted by jhovel

I just felt a bit more uncomfortable sayng that to a stranger than Stuart did....

I'm not sure if thats a good thing or a bad thing lol

I do have a second guess but I was waiting to see how the first one went.

Stuart

I will take the belts off and check etc tomorrow and let you know.

and yes the mill head is variable so there is a switch for hi and lo range

the spindle is NT30 so is prenty rigid for what I need it for but seeing as the ram, gibs and head bolts are all tight and short, im leaning toward the spindle being the problem so I will let you know how it goes tomorrow boys!

Originally Posted by the fabricator

I will take the belts off and check etc tomorrow and let you know.

and yes the mill head is variable so there is a switch for hi and lo range

the spindle is NT30 so is prenty rigid for what I need it for but seeing as the ram, gibs and head bolts are all tight and short, im leaning toward the spindle being the problem so I will let you know how it goes tomorrow boys!

Have had several bridgeports and a Kondia (30iso Spanish copy) even though the Kondia was heavier I never felt the 30 ISO column was as good as R8. Yes the R8 key is crap but the majority portion of the tooling is supported inside the column between the bearings. With ISO30 a fair share of the tooling hung below the lower bearing.

ok so ive done a fair bit of troubleshooting since last post! I have the motor off ( bearings are rat sh&t)
I have the spindle half out ( bottom two bearings are also rat sh&t ) but I cant get the spindle all the way out. story is I took off the spindle nose nut, the spindle came out about 150mm but now wont go any further. any ideas?

hoping some new bearings will solve this problem