need some machining tips

[Cane_man]

i am a self taught machinist, i dont know what i am doing completely i just do what works for me and i am probably doing things incorrectly and i probably have some bad habits... in the past i worked with softer materials (Duronze and German Silver) which were very forgiving and easy to ream and lap so good technique was not a premium... but i am finding out not so with tool steel...

i would appreciate your insights here:

reaming - what speed should i run the lathe when reaming? i will be using a 2 flute reamer made from W1 heat treated and annealed and it is probaly 50 RC hardness, and my lathe can slow down to about 50 rpm and speed up to 2000 rpm... i noticed when reaming that if i turn it too slowly the lathe doesn't have enough power to make the cuts.. i will be step drilling the point forming die, then reaming... do i ream it twice?

lapping compounds - i have some brass laps made up, where is a readily available source for lapping compounds... i hear the aluminum oxide is the way to go with steel but i cant seem to find any... and what grits should i be using... this is in context of lapping a point forming die and blind hole lapping...

[nhrifle]

If we were talking CNC equipment I could give you actual speed and feed numbers, but on our home machines we have to wing it. The rule of thumb when reaming is half the RPM of drilling and twice the feed for the same size hole. With my little lathe at home, I just back down on spindle speed till I feel comfortable and give the reamer a nice, slow and gentle ride into the part. Be sure and use plenty of cutting oil, or better yet, use some CNC coolant in a squirt bottle and keep the reamer bathed in coolant. Heat is the bane of cutting tools, and it is worse with reamers.

Not sure about the lapping compounds. Hopefully someone else can chime in about that.

I hope this helped a little, be sure and post your progress. We are all learning together!

[john hayslip]

If the tool steel is already hardened then you probably should anneal it, ream, and reharden. Isn't valve grinding compound aluminum oxide? Get a catalog from Enco or one of the other large tool suppliers.

[Cane_man]

^^^ the tool steel is reamed in the annealed state to approximately 0.004 oversized, then any scoring from the reamer is lapped taking out approximately 0.002, then the tool steel is heat treated and tempered to a hardness of 50 RC or so, and then lap the final 0.002 or so

[Reload3006]

Do you have a recommended FPM for your material? is O1 or W1 etc the steels we are talking about? I am guessing but would suspect you should be shooting for about 100 - 250 SFPM the formula for finding that is SFPM x 12=Pi x diameter x RPM since you are probably turning your tail stock to drill calculating your chip load is probably a waste of time just go slow and allow the tool to cut.

[customcutter]

Cane,
I think valve grinding compound is Al oxide, worth a try, and should be available at an auto parts house. Seems I also remember reading somewhere (maybe KTN's thread), that they used cast iron for a lap. I got some 1/4" brass, that I'm going to try also. I haven't found any cast iron less than 3" on the sites I've looked at a few weeks ago. I'm sure it's available, just haven't found it.

CC

edit, Laps are another reason I'm going ahead with the ball turner. I want the laps the same size as the reamers, or very close.

[Cane_man]

dang, i was reaming out the die today and the tip snapped off my latest version of the reamer

i was turning the die really slowly and advancing the reamer slowly as well, it hit a drill step locked into the metal and snap!

thanks cc, i got some valve grinding compound 2 pack at the auto parts store, one tube is course (Bing says it is 120 grit) and the other fine (280 grit), just about right for rough lapping

this die might be the end of me but i dont give up easily so i will eventually kick its butt

[customcutter]

Been there done that with my first reamer. It was a 4 flute. Entirely my fault, I forgot to temper it back after heat treating and it shattered like glass. I think I'm OCD myself, for what I've spent trying to make a set of dies, I could have bought a lot of bullets to reload with. OOPS I forgot, I can't find them anywhere, (and they are only going to harder to find in the future), so that's why I'm making the dies

Plus, I've bought a few more tools and learned more about machining since starting this project.

I've got some valve grinding compound around here too. If I can lay my hands on it.

CC

[JRPVT]

Cane, I usually grab a piece of soft stock to try new tools on to get the "feel" of them. Then you can practice feeds and speeds until you're comfortable with it. Then go for the real cut. Always use coolant, it really does make a difference.
jrpvt

[bob208]

i think you would be better off boring it to size rather then reaming. but if using a reamer use lots of cutting oil or it will cut over size.

[Cane_man]

is "coolant" any different than cutting oil?

[Reload3006]

Yes and no. Coolant is what is put in machines to be used as a cutting fluid it provides machining lubricant and rust prevention on the machine.

[nhrifle]

There are coolants that are rated as cutting fluid, but I am dubious as to the validity of that claim. True cutting oil has high pressure lubricants that operate under extreme conditions. Coolant is an oil that is mixed with water in a ration of 6 to 15 percent depending on application.

[KTN]

dang, i was reaming out the die today and the tip snapped off my latest version of the reamer

I know the feeling, I have broken my share of reamers . With 4 flutes .224" reamer tips get really thin, so my latest reamer is 3 flute . Keep up the good work.


Kaj

[teddyblu]

Hello KTN
I havent seen your posts for a while, but I follow them.
I also find the four flute difficult to manuf. and went to the three flute. Made one 308 three flute and looks and sharpens great.

[customcutter]

KTN & Teddyblu,

Just wondering, when you made the 3 flute reamers, did you mill the slots? Similar to the 4 flute except 120* instead of 90*?

Teddyblu,

IIRC, you used a "grinder" on a tool post? Was it set up like a ball turner/radius turner, to achieve the "ogive" or were you just "eyeballing" it?

thanks,
CC

[Cane_man]

wow, KTN is like bigfoot... you hear a lot about him but never see him!

you can see here where he mills the flutes:

http://castboolits.gunloads.com/show...l=1#post856545

3 fluted reamer, didn't think of that... i have to use my tool post and different sizes of end mills offset of the center line to work as a ghetto mill, but it seems to be working OK with limitations...

[teddyblu]

I use a mill and rotary index, and 120 deg spacing.
For the ogive I use a home made radius grinder with repeatable settings.
KTN uses the mill head set at an angle to shapen the point, which is great.
I use a swiss file to sharpen the point taking only 3-5 minutes. probably takes 20-30 minutes to recalibrate the mill head to 0.0

KTN may come in and tell his version, I would be glad to here any comments he has..

if KTN has a picture to show a 3 flute reamer great. If not I will post a pic tomarrow of th .308 I made.
Larry

[blaser.306]

Search diamond lapping compound over @ fleabay! Many grits available ranging from 400 - 200 000 mesh equivalent! Reasonably cheap and guaranteed to cut hardened steel !

[KTN]

Don't have any pictures right now, my old computer died and all pictures.... and it took me 7 months to buy new computer, that's why I haven't posted for a while.
I used bolt and nuts to make hexagonal holder for reamer blank. First I shimmed nuts on bolt so that all sides were straight, next lathe turned little bit of from corners to get consistent diameter and then milled all 6 sides straight and concentric.
Set it on lathe and drilled center hole for reamer blank, next drilled and tapped holes for set screws on all 6 sides, first hole about ½" from end and second about 1" from end, one hole per side.
With this holder slowly spinning in lathe, I can adjust blank with set screws until it's spinning straight.
Then it's just milling 3 flutes, filing, hardening, tempering and final sharpening.

Few more tips.
For derimmer and core seat punch I use 5.1mm=0.200" double-end drillbit and for core swage punch 4.9mm=0.193" drillbit.
It's nice to see I'm not the only amateur machinist trying to make swagedies .



Kaj