By continuing to use this site, you agree to our use of cookies. Find out more
Forum sponsored by:
Forum sponsored by Allendale Jan 24th

Help with poor finish when cutting with the side of the cutter

All Topics | Latest Posts

Search for:  in Thread Title in  
nic30/12/2011 18:17:16
42 forum posts
1 photos
Hi there,

I've just milled the first test cuts on my new Super X3 on a block of aluminium and I'm surprised at how much poorer peripheral (side) cuts are compared to top cuts. For example, using a 50mm indexable end mill I can get a virtual mirror finish on the top, but when cutting the side, a 16mm 4 flute HSS end mill leaves the surface marked with many vertical lines, often wavy. Other cutters show the same problem.
I think the side cuts should be as good as top cuts, so what's going on?

Any help greatly appreciated.

Thanks,

Nic
JasonB30/12/2011 18:28:14
avatar
Moderator
18134 forum posts
1996 photos
1 articles
What depth of cut and how thick is the material?
 
Wavy lines suggest chatter.
 
Have you checked teh spindle bearings for play, when my X3 arrived I could move it 0.030" from side to side, the lock nuts were completely loose.
 
J
nic30/12/2011 19:35:48
42 forum posts
1 photos
Hi there,
 
I can't measure any play in the spindle bearings, I have just tried locking all gib screws except the axis i'm traversing and those ones were done up extra tight and i'm still having the same problem.
 
All were very light finishing cuts, the aluminium is approx 75mm square.
 
Thanks
 
 
JasonB30/12/2011 19:40:20
avatar
Moderator
18134 forum posts
1996 photos
1 articles
How much of the 75mm side are you trying to cut in one go eg what length of the side of the 16mm cutter is actually cutting.
 
What speed are you using?
 
Any cutting fluid, if so what?
nic30/12/2011 19:44:44
42 forum posts
1 photos
Hi there,
 
At most 10mm depth.
 
1700rpm
 
WD40
 
Cheers.
 
 
 
 
JasonB30/12/2011 19:47:14
avatar
Moderator
18134 forum posts
1996 photos
1 articles
Try halving the speed.
 
J
Jim Greethead30/12/2011 19:49:19
avatar
131 forum posts
8 photos
Good question Nick, I have the same problem but I didn't think to ask. I will be watching with interest to see if there is anything I can do to improve the finish. It could save a lot of filing and polishing.
 
Thanks for the interest Jason, I have a feeling that you might be able to help here as you have in other threads.
 
Jim
 
Chris Gunn30/12/2011 20:52:31
327 forum posts
24 photos
If you are running a 16mm cutter along the side of your block 10mm deep, each tooth is trying to take a 10mm long cut, even though it may not be a deep cut. When you are face milling each tooth is only taking a cut of a few thou.
This leads to chatter on a hobby machine, however good the set up and the bearings are. Every vertical miller I have had gives a similar result.
Industrial machines have a much better spindle than hobby machines and are much heavier all round.
The marks can be minimised by getting the speed right and taking a very fine cut to finish, but you will still get a ripple.
In the good old days a horizontal miller would have been used to mill the sides of your block, and you would then be back to a few thou a tooth and a good finish. The answer is, if the finish is vital, dont do it, turn the workpiece around and do it with your face mill if possible.
Chris Gunn
Stub Mandrel30/12/2011 20:59:33
avatar
4307 forum posts
291 photos
1 articles
I've notioced this on my X2, as the wavy effect is very regular and can be reduced by changing speed (up or down) I think its possible a resonance effect.
 
You could try changing your feedrate as well.
 
Neil
mgj31/12/2011 10:53:09
1008 forum posts
14 photos
If its resonance, or flexing , then the other solution might be to change the number of teeth on the cutter. I know most endmills are 4 tooth, but some of the indexable ones have varying numbers of teeth, and you can often find 3 tooth cutters around.
 
One other solution might be to increase depth of cut, so that the helix of tooth A has not left the work before tooth B engages. That cuts down vibration and improves finish, if the size of job permits.(and the shape/helix of the cutter). The small FC3 cutters always seem to produce a very good finish, and that, I think is/may be one of the reasons.
 
I think its also important to realise when milling that the depth of cut is determined by the feed - or more specifically the tooth load per rev, so just because one is taking a deep (long) cut, doesn't mean to say that the cutter is seeing a deep (big) cut. Tooth loads are generally within a couple of thou per tooth per rev - but then if you have a lot of teeth you can feed very fast. What may well be happening is that you are using too low a feed, and the cutter is skidding initially and then digging and engaging, so you end up with peaks and troughs. (and a blunt cutter can do this too - blunt cutters need higher feeds).
 
If you look at Tubal Cains book Milling Operations in The Lathe, the whole business of tooth load and feed rates is explained very well. Its getting a little long in the tooth, since it predated carbide cutters (toothload figures for which should be available from the suppliers, manufacturers web site), but its first calss on the principles one needs to understand, and where to start.
 

Roderick Jenkins31/12/2011 11:12:17
avatar
1885 forum posts
481 photos
I'd just like to reinforce MGJ's recommendation of Tubal Cain's book "Milling Operations in The Lathe". This is a very good treatise on the technicalities of milling. I'm sure Tubal Cain would have written a book on vertical milling if Arnold Throp's rather superficial "Vertical Milling in the Home Workshop" wasn't already in the Workshop Practice series.
 
Rod
Tony Pratt 131/12/2011 11:59:55
1130 forum posts
5 photos
Ric, as has been said try halving your speed to get rid of any resonance and check your spindle bearings aren't too loose. Check that the axis you are using is correctly adjusted, smooth in operation but not tight or loose. Take a small cut with a sharp cutter in the conventional direction ie feed the work against the cutter rotation, then reverse the feed and go back across the machined surface[this is climb milling] without adding a cut, you may notice some small amout of material being removed and perhaps the finish improving?
Tony
Jim Greethead01/01/2012 10:06:54
avatar
131 forum posts
8 photos
Thank you all for your good advice to Nic which I have also taken on board.
 
There are many things to try and I have found that a climb milling cut on the same setting improves the finish as does the use of WD40.
 
I have ordered a copy of Tubal Cain's book and will examine it with pleasure when it arrives.
 
Ultimately, I suspect that Chris Gunn's advice will prevail but I will have learned something on the way. And that is part of the pleasure.
 
Happy New Year to all of you.
 
Jim
 
nic01/01/2012 17:51:19
42 forum posts
1 photos
Hi there,
 
Thankyou so much for your help so far, I have only just managed to get back to the computer, new year and all!
 
I will be reading through all your advice but in the mean time I came across this page:
 
 
Again I have not read all the way through it but someone does talk about a carbide end mill specifically designed for cutting aluminium.
 
I have gone ahead and bought one from ebay to eliminate the cutter being the problem and I will report back when it arrives, has anyone else tried this type of cutter?
 
Thanks again
 
Nic
 
 
Jim Greethead01/01/2012 21:52:00
avatar
131 forum posts
8 photos
Hi Nic,
 
Thanks for the link, I did read all the way to the finish. He decided that the problem was that the taper was bellmouthed and that the solution to this (and other) problems was to have the spindle rebuilt.
 
But then we did not get the results from all that. A recent post has asked for the outcome so we may yet find out.
 
BTW, I get this type of finish and I also get it when I use a woodworking router bit to round off the edges of my engine bases. The bit is a two blade carbide so I was not surprised to see chatter marks. But perhaps it is just the limitations of the HM45.
 
I will be interested to see the results you get with the carbide end mill.
 
Jim
 

All Topics | Latest Posts

Please login to post a reply.

Magazine Locator

Want the latest issue of Model Engineer or Model Engineers' Workshop? Use our magazine locator links to find your nearest stockist!

Find Model Engineer & Model Engineers' Workshop

Support Our Partners
emcomachinetools
Eccentric July 5 2018
Allendale Electronics
ChesterUK
cowells
Warco
Eccentric Engineering
Subscription Offer

Latest "For Sale" Ads
Latest "Wanted" Ads
Get In Touch!

Do you want to contact the Model Engineer and Model Engineers' Workshop team?

You can contact us by phone, mail or email about the magazines including becoming a contributor, submitting reader's letters or making queries about articles. You can also get in touch about this website, advertising or other general issues.

Click THIS LINK for full contact details.

For subscription issues please see THIS LINK.

Digital Back Issues

Social Media online

'Like' us on Facebook
Follow us on Facebook

Follow us on Twitter
 Twitter Logo

Pin us on Pinterest