Machining 4140 Chrome Moly

[erikmannie]

Why is everyone such carbide devotees for the HOME SHOP? HSS gets sharper than carbide and makes cleaner cuts. It can do interrupted cuts. You can easily grind custom shapes. I even make W1 cutters where I need a complex shape that can't be ground with what I have. (just slow the speeds down!)

You guys don't need to use carbide for much except long facing jobs like taking a cut across your cast iron face plate. Cast iron eats up HSS pretty fast. I also use carbide on HARDENED steel sometimes(though that is not its intended purpose). Pre hard 4140 is not all that hard. I use HSS on it all the time.

We are not operating factories here. I think many waste a lot of money they don't have to on carbide and inserts. Most of your home shop machines don't run fast enough to even make the proper use of carbide.

I have both HSS & carbide in my home hobby shop. I use carbide about 90% of the time. I chose carbide so that I can get near perfect geometry immediately. I don’t mind grinding HSS bits, but I would rather spend that time cutting & knocking out the project.

 

[erikmannie]

Ready-made disposable HSS inserts? Yes, that's a joke. I think.

I have a lot of ready made HSS inserts. They are just like indexable carbide inserts, but the material is HSS. I dispose of them once they become dull or chipped, just as with the carbide inserts. They have a very small nose radius; the documentation says that they are good for non-ferrous, non-hardened materials.

 

[pdentrem]

HSS still has use in the shop environment.
I was not satisfied with the cutting forces with the available carbide inserts we had available that day. Had the wrong type for the job. So used a hand ground HSS tool to turn these 4140 shafts from 2” to 1.125“ +.010” on one end and 1” +.010”. Leaving the +.010” so that I could finish to size on the grinder. Was taking .100” off the radius per pass at the start and less of course at the end. I guess my clone of Jet BDB1340 w/2 hp VFD does just fine as well.
Pierre

 

[mickri]

Except for a boring bar set I bought for my boring head and some 60* carbide tool bits that came with my lathe I only have HSS. My old craftsman 12x36 lathe was made for use with HSS. Learning how to grind HSS tool bits isn't hard if you have a belt sander with a table that can be adjusted to different angles. Hard is trying to use a 4.5" hand held high speed angle grinder to grind tool bits. That's what I started with before getting a bench grinder and then finally my 1x42 delta belt sander.

For me I can't see any benefit in a hobby shop to using expensive carbide inserts and the special tool holders needed to use them except to line the pockets of the people that sell them. I researched feeds and speeds for what I usually work on, 1018. According to my 1937 edition of the MOLO 164, 266 and 418 are the proper rpms to use for what I machine. These rpm's are also appropriate for 4140 according to the MOLO. Carbide doesn't work at these speeds.

It doesn't matter if it takes me 10 minutes or 10 hours to make something. Longer is probably better from a fun factor because I get to spend more time using my machines. There is no prize in my shop to see how fast something can be machined.

 

[killswitch505]

Why is everyone such carbide devotees for the HOME SHOP? HSS gets sharper than carbide and makes cleaner cuts. It can do interrupted cuts. You can easily grind custom shapes. I even make W1 cutters where I need a complex shape that can't be ground with what I have. (just slow the speeds down!)

You guys don't need to use carbide for much except long facing jobs like taking a cut across your cast iron face plate. Cast iron eats up HSS pretty fast. I also use carbide on HARDENED steel sometimes(though that is not its intended purpose). Pre hard 4140 is not all that hard. I use HSS on it all the time.

We are not operating factories here. I think many waste a lot of money they don't have to on carbide and inserts. Most of your home shop machines don't run fast enough to even make the proper use of carbide.

I’ve really wanted to start grinding my own HSS. I don’t have a lot of extra time I work 10 to 90 hours a week. so inserts are my go to. That might play a factor into why a lot of hobby guys use them. I don’t see it so much in this forum but in the Facebook groups guy giving other guys **** over installing DROs on their hobby machines. I’ve DRO on my mill and lathe because when I get hobby shop time I want to spend it as efficiently as possible.