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Reamer sharpening question

FlatBeltBob

Stainless
Joined
Jul 22, 2007
Location
central WI
This may be a question for the abrasive machining area , but lets see if you guys can help first ..
I am having trouble with a reaming operation on my Cnc mill .
I am reaming a DOM tube that is .735 ID to .766 and feeding @ 6 ipm /450 rpm.
Last time I ran this job at 12 ipm with no problems , but this batch of tube is slightly smaller .
The problem is that I am getting a built up edge fused to one of the flutes , and almost trashed the tool a few times . Looking at the reamer , it looks like the flutes are not very
deep and I am thinking that the chips do not have a free flow to curl out .
Should I try to grind the flutes deeper ( at least at the cutting end ).
I already have the set up on the cutter grinder to sharpen the tips , so a thin gashing wheel would not be a big deal to change to . Maybe grind a small radius at the bottom of the flute?
Other things I tried so far : very rich coolant mix / change drill cycle to a wood peck routine , to break the chips ( helps a bit ) added a pre drill , tool chg, fin ream routine ( too slow ) . Any advice appreciated .. I have to do a 2,500 part run asap .
Thanks
FBB
 
How deep are you reaming? I'm imagining that the flute is actually getting plugged up. If this particular batch is extra ductile, it may not be dropping the chips out and you'll have to peck. Not necessarily a full withdrawal peck, but a chip break peck cycle. One of the G73 cycle options on a Haas mill.
 
I highly doubt chip packing and highly suspect WAY too many rpm.

I'd cut the R's in half and dbl the feed.

edit - OK - I guess number of flutes would make a diff. Doo you have a course or fine reamer? I like course flute tipped reamers - like say - _____ Rock? (Kant think rat now)


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Think Snow Eh!
Ox
 
I am reaming thru a tube that is 2" long . The part is held in a 3 jaw , bolted on parallels - with a chip pan underneath . It reams Ok for about the first 1.25".
I am getting some rapid wear on the tips . Tried to grind the angle at about 45 deg , then changed it a few degrees ( sharper angle ) .
425 rpm figures out to around 80 fpm .. this is a HS reamer .
I am careful to hone a micro edge after grinding , by slipping a diamond stick on the land faces.
maybe a slower rpm will help , as it does seem to be a heat problem .
I was remembering a similar condition on my cold saw blades , where an improper tooth gullet shape , was impeding the chip flow , and causing metal to fuse on the tip.
That is why I was suspecting the flute depth as a possible concern . Plus it is a rather roughly ground surface for a USA made tool .
8 flutes on a 49/64" reamer
 
Last edited:
reamer

Don't have a CNC, but i have found DOM not to be always concentric.Iwould put a .750 centercutting end mill into the prior step just to true up the bore ,then only .016 to ream. Think it will save time over the run.Good luck
Jim
 
FlatBeltBob,
One thing I would add, is if you're set up with a cutter grinder, and feel inventive, there is no harm in trying to improve the chip flow through creative flute grinding.

Maybe you can invent the spiral point reamer that shoots the chips ahead of the reamer, keeping the flutes totally clear on through hole reaming :)
 
HuFlung, they already have that. It's a left hand twist, right hand cutting spiral flute reamer.
 
How is your cooling? We had a problem with a machine that lost it´s precision in pretty reproducible intervals, over days and then would shoot straight for another few days to go back to loose tolerances again for days. As I found out, it coincided with the shift plan. Problem was one of the operators bent away the flood cooling so he could see what was going on, not much, the part was still flooded but the coolant flow was no longer spot on the hole. This was bad enough to make the hole in form of an opening taper to the rear with a diameter increase of 0,02-0,03 mm. Doesn´t sound drastic but these parts generated a lot of noise when installed in the final product.

Cheers,
Johann
 
OK , so I tried almost everything without much progress. Slowed down the RPM, played around with the woodpeck parameters , hand dressed the face of the flute to get a smooth finish . Still get an occasional chip fused to the flute . Went back to the way we used to do the job , on the radial drill press . I hate doing it this way , but I got some tactile feedback doing it with hand feed . It is still not cutting freely . I need to go back to the books to see about proper reamer tip geometry . : 45 degree grind , back clearence , kind of eyeballing the clearence angle . Don't know what I am missing , as I have ground hundreds of reamer ends , core drills. Maybe as someone suggested , the material is more ductile ( softer ? )
and is just prone to built up edges .
In the meantime , my new USA 49/64 Cleveland drill showed up , and got a good work out .
cranked the feed up to 15ipm , and peck every .300" to break the chips . Doing a fine job , and customer is OK with the finish . Darn stringy chips are a hassle though .
Thanks all for the suggestions anyway
FBB
 








 
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