Need Advice About Side/Slot Milling in Steel

[ChandlerJPerry]

I am wondering if anyone can offer a better way to do this. I am making a few of these parts. Currently I am cutting out the main window by slotting with a 1/2" carbide 4 fl endmill. Running around 1000 RPM. Currently doing it in two passes as I run into chatter issues at full depth of cut, even if I slow down the RPM. Ideally I would like to knock it out in one pass if possible. My machine may not have the rigidity for what I want but taking ideas.



I'm wondering if switching to a roughing style endmill would get me what I'm after? Or maybe a different tooling choice I'm not thinking of. Material is 1/4" thick low carbon steel. Machine is a 1500~ lb knee mill.

 

[m1kemex]

Do the "window" has to have round edges at the bottom?

Whenever you're cutting a feature in a hollow material, the answer is usually some sort of saw, not a mill. An acetylene torch or plasma cutter with a guide would be far quicker. And then you can just clean it up with the mill. With the bonus that you keep the chunk you cut off for some other use, instead of a mountain of swarf.

 

[MikeInOr]

That was my thought too. Remove the bulk of the material with a plasma cutter using a jig to guide it then clean up with the mill.

 

[ChandlerJPerry]

Both fantastic ideas! Unfortunately I lack both tools which is why I settled on milling in the first place. What about some kind of slitting saw? I've never used one before so uncertain if they would work for this application.

 

[MikeInOr]

I have never used a slitting saw either.

A roughing endmill definitely cuts a lot faster for me (and can take bigger cuts) at the cost of leaving a rougher finish. But a roughing endmill can easily be cleaned up with a pass from a regular endmill.

P.S. I have a cheap YesWelder plasma cutter that has saved me a ton of time. At $200 it has probably paid for itself in tooling.

Amazon.com

What are the pieces for? They look very nicely made!

 

[ChandlerJPerry]

Surface finish isn't the most critical here because I'm likely putting a coat of chassis paint on these when they're finished, so a rougher sounds like it could be a great option followed by a cleanup pass. Maybe even just the rougher depending on what it leaves the edges of the window looking like.

They are to make a differential mount for a 1986 Nissan 300ZX. Sadly the original mount is no longer available from Nissan and can't be easily repaired once the rubber rips. The design I am making is a direct copy of one that an aftermarket manufacturer used to make, however it seems that they've gone out of business recently.

Thankfully a friend of mine had one available for me to copy the dimensions from in order to replicate, with the condition being that I make him another in exchange for getting to reverse engineer it.

I've gotten some interest from a few online communities dedicated to these cars in doing a short run of these since they're no longer available elsewhere, which is why I'm interested in a better process.

I will say, a $200 plasma cutter is a pretty appealing option if I get enough interest in this. At the prices they were being sold for previously, it would only take a couple to pay for it, and then I get a shiny new tool to make more things with!

 

[MikeInOr]

Cool project for a cool car!

I think you might find a roughing end mill will speed things up considerably.

The YesWelder is definitely a low end plasma cutter... but mine has been working fine for a couple of years of hobby use with no problems.

 

[RaisedByWolves]

I am wondering if anyone can offer a better way to do this. I am making a few of these parts. Currently I am cutting out the main window by slotting with a 1/2" carbide 4 fl endmill. Running around 1000 RPM. Currently doing it in two passes as I run into chatter issues at full depth of cut, even if I slow down the RPM. Ideally I would like to knock it out in one pass if possible. My machine may not have the rigidity for what I want but taking ideas.

View attachment 500608

I'm wondering if switching to a roughing style endmill would get me what I'm after? Or maybe a different tooling choice I'm not thinking of. Material is 1/4" thick low carbon steel. Machine is a 1500~ lb knee mill.
View attachment 500609

Are you locking all 3 axes?

1000 rpm is much too fast.

 

[woodchucker]

Both fantastic ideas! Unfortunately I lack both tools which is why I settled on milling in the first place. What about some kind of slitting saw? I've never used one before so uncertain if they would work for this application.

use an angle grinder to rough cut it. Just cut on the waste side and then clean up. Much faster.

 

[bill stupak]

Plus 1 on the roughing end mill. I've cut through 1/4" mild steel with a 1/4" HSS roughing end mill in a small mill (g0704) in one pass and had no problems, cut through like butter.