On Fri, 18 Dec 2009 22:39:53 -0500, GeoLane at PTD dot NET
GeoLane at PTD dot NET wrote:
I'm looking at R8 carbide indexable end mills from CDCO to use for
cleaning up rusty stock and squaring up stock. One says it uses
tpg-32 inserts. Are those the same as tpg-322?
Get a copy of the Enco [or another] catalog that has instructions
on how to decode carbide specifications.
http://www.michigandrill.com/catalog/view-mdc/173.pdf will get
you started.
for sale prices see
http://www.use-enco.com/CGI/INLMK32?PARTPG=INSRAR2
TPG stands for "Triangular Positive Ground"
TPU stands for "Triangular Positive Unground" [on the top], and
is about the cheapest carbide insert available. For home shop
turning and milling use these are generally entirely adequate.
If possible buy a package [on sale] as the price per insert is
generally much less.
Generally TPU/TPG inserts will have 11 degree side relief angles.
To decode the numbers
TPGxyz
x is the diameter of the largest circle that will just fit onto
the insert in eights of an inch, thus a TPG3yz is a triangular
insert that will just enclose a 3/8 diameter circle.
y is the thickness in 1/16s of an inch. thus TPG32z is nominally
2/16s or 1/8 thick.
z is the corner radius in 64ths of an inch. Thus as TPG322 would
have a 2/64ths or 1/32 corner radius
Another alternative is a similar 2.5" indexable end mill, which uses
a different insert. SPG422 carbide Positive rake, 15 Degree lead angle
I have a Bridgeport with the 2J head. Which of the two is more likely
to give a good finish on hot and cold rolled steel?
SPG stands for Square Positive Ground" and the numbers are coded
the same way. Note that you get an additional corner with the S
inserts, but you may find out when you do a per corner cost that
the TPUs are cheaper.
What difference does the positive rake and 15º lead angle make?
Long involved discussion here. You have to have positive rake
inserts for the back of the tool to not drag on the work. While
there are mill and lathe holders for negative tools, this
generally requires more rigidity and power than the typical
home/hobby machine. Moltrech among several others discusses the
effect of lead angle on milling.
http://www.amazon.com/Machine-Shop-P.../dp/0831111321
https://www.hanserpublications.com/p...=9781569902738
Here's a link to the 2" one
http://www.cdcotools.com/item.php?itemid=126
Here's the link to the 2.5" one
http://www.cdcotools.com/item.php?itemid=471
RWL
Be reminded that you will [theoretically] need two grades if you
machine both aluminum and steel. C2 for Aluminum and C5 or C6
for steel. However for the typical low volume low stress home
shop machining more than likely either one will be perfectly
satisfactory with both materials.
Given that you will be tending to chip and break the inserts
milling rusty material, possibly with hard spots, I urge you to
consider a fly cutter using HSS lathe tools. The cost is low and
as you can resharpen the HSS tool bit on most any grinder or belt
sander, this is one of the most economical solutions,
particularly for the home shop where production and speed are not
important.
Making a fly cutter was a traditional apprentice project,
frequently with two HSS bits, one roughing and one finishing,
however as you are just starting machining I would buy a single
bit fly cutter set to start and then after you gain some
experience and insight into the terminology such as axial and
radial rake, you can build your own, sizing to fit your
equipment.
For an import fly cutter set see
http://www.use-enco.com/CGI/INSRIT?P...&PARTPG=INLMPI
if you want a fly cutter with an R8 shank see
http://metalworking.mscdirect.com/CGI/MWSRCH?N=4051
for a more elaborate fly cutter see
http://www.kristitool.com/ktl/b-52.php
Let the group know how you make out.
Unka George (George McDuffee)
...............................
The past is a foreign country;
they do things differently there.
L. P. Hartley (1895-1972), British author.
The Go-Between, Prologue (1953).