machinist@lists.ibiblio.org
Subject: Machinist
List archive
- From: Lawrence London <lfljvenaura@gmail.com>
- To: machinist@lists.ibiblio.org
- Subject: [machinist] Slitting Saw Help
- Date: Wed, 11 Dec 2013 01:17:13 -0500
http://www.practicalmachinist.com/vb/general/slitting-saw-help-276651/
Thread: Slitting Saw Help
-
Slitting Saw Help
I need to cut a slot through a piece of 2"x2" 1018 steel. The slot will be about 1.25" deep and go for about 12". The thickness of the slot doesn't matter. I'm looking for some advice on what diameter saw, teeth, and thickness I should use. I do know I should keep the RPM about 80-120 depending on the diameter. Also, how many passes, depth per pass, what it should sound/feel like as I cut etc. I've never used a slitting saw and would prefer not to ruin any as they're relatively expensive.
The part will be adequately clamped down but is being cut in a less than rigid machine. I want to be safe and not ruin anything, but I am trying to get this done as quickly as possible. -
12-10-2013, 04:43 PM #2
- Join Date
- Oct 2010
- Location
- Oregon, USA
- Posts
- 1,918
If thickness doesn't matter, I'd pick a 5" diameter, 1/8" wide, side tooth milling cutter and put it on the appropriate 1" or 1-1/4" arbor. The 5" diameter should just leave enough room for arbor spacers and nuts and still reach 1.25" deep.
This job would be better done on a horizontal, but you could do it on a "less than rigid" vertical if you take an appropriate depth of cut. Feed the table against the cutter rotation; don't climb mill on a "less than rigid" machine. Without knowing your machine, I can't advise you on depth of cut. On a decent horizontal, I'd probably bury it and take passes as deep as the chip clearing capacity of the gullets allows. On an R8 spindle machine, maybe start with 1/4" depth of cut? Set the feed rate appropriately for the HP of your machine. -
12-10-2013, 06:19 PM #3
- Join Date
- Sep 2005
- Location
- San Diego
- Posts
- 2,549
The Slitting Saw and the Woodruff Cutter
Slitting saws and Woodruff cutters work in much the same way; so we
can just call them saws for now. Saws have one big difficulty.
After we understand that difficulty we will solve it and increase
their performance. First a little background.
After you dig a hole in the ground to fix a water pipe you need to
put the dirt back. However all the dirt wont go back because it
doesn't fit anymore. The dirt has been "upset". That is, all the
little grains of soil and pebbles are no longer nestled together in
a compact form. This upset condition also happens in metal during
the cutting process.
Upsetting the metal increases its volume. So the metal in a chip
that is cut from a bar takes up more space after it has been cut.
Parting off steel in a lathe using a slender "part off" tool (The old style)
creates a long slender upset chip. This chips volume is greater
than when it was compact material in the parent metal. And greater
also are its dimensions. The chip is longer, thicker and wider.
The wider condition is what causes the problem. The kerf or groove
being cut has a width as wide as the part off tool. During the
cut, the emerging chip is actually wider than the groove being
formed. So the chip is in the groove under a "press fit"
condition.
As the bar rotates the press fit chip is being forced down against
the cutting tool. The tool has to support the pressure of the
downward cut in addition to the downward force created by the
emerging chip. The deeper into the bar the tool cuts, the greater
these forces multiply; because the chip grows longer before
exiting the groove.
The tool will break during this process unless the cut is shallow
or the feed rate is very light. A light feed rate will create a very
thin "ribbon" like chip with light forces; but this takes a much
longer time to do the work.
The difference between a part off tool and a slitting saw is
slitting saws have many "part off tools" or teeth around their axes.
Manufactures of these saws make them with tooth forms which have
flat ends on the teeth like a part off tool. These teeth then cut
a chip which is as wide as the slot just like the lathe tool and
with the same problems of high destructive forces caused by the
"press fit" chip being formed.
Unlike the lathe tool the saw has many teeth. So if one tooth
misses cutting something the tooth coming right behind it can
scoop up the remainder. Now to the "fix".
A double cut saw blade has chamfers on alternate teeth. These
chamfers on one corner of the tooth are made by grinding away one
third of the tooth on the left side of the first tooth and then on
the right side of the next tooth and so on. This grinding is done
on each tooth at a 45 degree angle with a little relief.
Now when the saw cuts, it cuts a chip on the left and then a chip
on the right. These chips are only two thirds as wide as the slot.
The following tooth has its chamfer on the other side and so it picks
up the remainder of what the first tooth left. The forming chip
isn't wide enough to rub both sides of the slot so the slitting saw
can cut very freely and take a heavier chip load. Higher production
can then be the result.
Another saw geometry which I found very smooth was what is called a
triple cut blade. It works with a saw with a number of teeth which can
be divided by three.
The tooth width is about thirty five percent of the blade width. It develops
with a tooth on the right, then a tooth on the left, and finally a tooth in the
middle and repeat. It works with less pressure and almost feels like a rotary file.
Regards,
Stanley Dornfeld, San Diego -
12-11-2013, 01:01 AM #4
- Join Date
- Jan 2001
- Location
- Running Springs, Ca. USA
- Posts
- 108
That may have been true with the (The old style) "part off" tool but with athe ISCAR Dogrip the chip comes out narrower than the slot being cut because of the bent back on the chip.
Originally Posted by Metalcutter
Parting off steel in a lathe using a slender "part off" tool (The old style)
creates a long slender upset chip. This chips volume is greater
than when it was compact material in the parent metal. And greater
also are its dimensions. The chip is longer, thicker and wider.
Don
-
New Concepts in Milling Handbook
A practical approach and illustrated guide to milling cutter selection and use
© 1973 Niagara Cutter Inc.
New Concepts in Milling Handbook from Niagara Cutter, LLC
C O N T E N T S
• A Value Added Approach to Milling Techniques -
An analytical,scientific and practical approach to milling cutter selection and use
• Milling Cutter Nomenclature -
A written and pictorial definition of the basic nomenclature of a milling cutter
• Basic Cutter Styles and Their Application -
A written and pictorial definition of the multiple uses of Building Block Cutters with engineering charts for modification and interlocking
• Selection of Speeds and Feeds and Cutting Tool Materials
A definition of the formation of the chip, chemical composition of cutting tool materials and engineering charts for setting of speed and feed for a variety of materials
• Cutter Sharpening and Inspection Data
Reply
- [machinist] Slitting Saw Help, Lawrence London, 12/11/2013
Archive powered by MHonArc 2.6.24.