Flex in the mill spindle.

[Mauzinette]

Thanks for the mention @matthewsx, I would’ve missed the thread without it @tstr, where in Finland are you located?

 

[Pevehouse]

Hi guys and gals.
So I finally got my Chinese ZAY7045V/1 to the point where I can begin to try to mill something but I can't seem to be getting any results. I tried milling some mild steel, just to learn how things work. I had a 16 mm HSS endmill in a ER25 collet and tried to slot mill the steel. 0,2 mm depth of cut gave terrible vibrations at 500 rpm and kind of crappy finish. Anyway after lots of trying onething and learning something else and repeating several times I decided to test the runouts on the ER holder and the endmill, results were 0,05 mm runout on both which seemed reasonable since they are from China. But after that I stuck the dial indicator to the spindle and tried how much give it has when pushed and pulled and the result was 0,1 mm. How screwed am I, this seems too much, is there anything to fix this?

Boo, do you have any pictures of your mill? I would like to see if it the same machine I have. If so I may be able to help

 

[Huub Buis]

But after that I stuck the dial indicator to the spindle and tried how much give it has when pushed and pulled and the result was 0,1 mm. How screwed am I, this seems too much, is there anything to fix this?

0.1 mm is a lot but are you measuring flex or play. It makes a lot of difference when you measure having the Z-axis at max height or just above the table. Also the length of the tool stick out in the chuck matters and how hard are you are pulling or pushing.

My BF16 small hobby manual mill (120 kg) will flex 0.02 mm when I pull at the tip of the spindle with 8 kg (X and Y direction). The spindle/tool is just above the table, the tool stickout is 40 mm (16 mm steel bar) and all axis are locked.
I mill mild steel using a 20 mm HSS-Co 8% 4 flute end mill at 500 RPM but only at 0.25 mm depth of cut. In general, I use smaller (10 mm) end mills but the max depth of cut in steel is 0.5 mm.
Because the mill has lead screws, not ball screws, I use conventional milling. For climb milling, I have to pull at the table with one hand and use the other hand to advance the table.

 

[markba633csi]

A word about backlash: All machines using conventional leadscrews have some. Machines with ballscrews have much less. The idea is to advance the table towards the cutter so as to zero out the backlash before the cutter contacts the workpiece (conventional cutting)
Trying to climb cut can be difficult with machines that have excessive backlash since the table can suddenly "jump" in the direction of the feed.
Climb cutting can sometimes give a better finish but it takes some experimentation. Usually it's best to stick with conventional cutting at first.

 

[woodchucker]

a 16mm end mill is a big end mill. a 12mm end mill is max of where I would be with that machine comfortably. I do not know if it will help.
On some mills, you can tighten the spindle play up by tightening an internal nut holding the spindle into the quill. It could be on the bottom of your quill and may have 2 holes for a spanner. That would be the best scenario if it would reduce the run out.

Were you using a 2 flute, 3, 4? The number of flutes does matter. More flutes in steel generally will smooth the cut out.
So many things to check to fix your run out.
is it:

• a spindle issue machined correctly.
• a quill issue
• a bearing issue
• a tunable issue (afformentioned nut)
• a user issue mis understanding how to measure it correctly.

 

[tstr]

For sourcing material are there any jobber machine shops in your area? Often if you get to know the guys there you can ask to buy offcuts (don’t call it scrap) at a reasonable price.

Also, does eBay work there? Lots of sellers on there so at least some of them should be willing to ship to you.

Finally, I know you’re not our only member from Finland. Try reaching out to @Mauzinette or @Norppu

John

Not in my immediate area that I know of, but will have to search around. Most of the aluminum I have is offcuts that was fist sold to a recycling center by a machine shop but that center was closed last year, but still no idea what grade it is.

Ebay works, but the shipping prices are still the +25 € so might as well buy from stahlhaus24.

Thanks for the referral, I asked Mauzinette and Norppu if they know any places for sourcing.

 

[tstr]

Thanks for the mention @matthewsx, I would’ve missed the thread without it @tstr, where in Finland are you located?

Near Turku.

 

[tstr]

Boo, do you have any pictures of your mill? I would like to see if it the same machine I have. If so I may be able to help

I posted a pic from the google image search earlier indicating the quill lock, it is the same machine, but I can take some more pictures later today.

 

[tstr]

0.1 mm is a lot but are you measuring flex or play. It makes a lot of difference when you measure having the Z-axis at max height or just above the table. Also the length of the tool stick out in the chuck matters and how hard are you are pulling or pushing.

My BF16 small hobby manual mill (120 kg) will flex 0.02 mm when I pull at the tip of the spindle with 8 kg (X and Y direction). The spindle/tool is just above the table, the tool stickout is 40 mm (16 mm steel bar) and all axis are locked.
I mill mild steel using a 20 mm HSS-Co 8% 4 flute end mill at 500 RPM but only at 0.25 mm depth of cut. In general, I use smaller (10 mm) end mills but the max depth of cut in steel is 0.5 mm.
Because the mill has lead screws, not ball screws, I use conventional milling. For climb milling, I have to pull at the table with one hand and use the other hand to advance the table.

I'm not entirely sure what is the difference with flex and play, but maybe I was meaning play? I had the indicator on one side set to 0 and pulled on the end mill with my left hand while simultaneously filming the indicator with my right hand and the needle moved to about -0,05 mm, then pushed the endmill and the needle moved to about +0,05 mm. I don't have a scale to measure the pulling/pushing force but I don't think the method described above can result in drastic forces. I've mainly tried conventional milling.

 

[tstr]

a 16mm end mill is a big end mill. a 12mm end mill is max of where I would be with that machine comfortably. I do not know if it will help.
On some mills, you can tighten the spindle play up by tightening an internal nut holding the spindle into the quill. It could be on the bottom of your quill and may have 2 holes for a spanner. That would be the best scenario if it would reduce the run out.

Were you using a 2 flute, 3, 4? The number of flutes does matter. More flutes in steel generally will smooth the cut out.
So many things to check to fix your run out.
is it:

• a spindle issue machined correctly.
• a quill issue
• a bearing issue
• a tunable issue (afformentioned nut)
• a user issue mis understanding how to measure it correctly.

Will have to try a smaller endmill. I was using a 4 flute endmill. A user issue and the tunable issue are probably only ones I could figure out on my own, as the manual is basically useless.