Milling Steel on a Mini Mill

[jonesrick]

Hi, all. My first post here. I want to buy a mini mill to make blades for my wood chipper, which the seller no longer supports. I think the blades are hardened steel, although I don't know for sure, only assuming. The mill I'm looking at is the LMS 4190. My question is: what size motor would I need on my LMS 4190 to bevel, drill holes, and tap into the steel blades for my wood chipper? Can anyone here recommend a mini mill for this operation?

Thanks for any reply, and happy holidays.

 

[Eddyde]

First, Welcome to Hobby Machinist.

Well, depending on the hardness required, "hardened" steel will be difficult to impossible mill, especially a mini-mill. The procedure is usually to machine the part while the steel is still soft, then harden it. if the part needs any additional shaping or sharpening after hardening, it is done by grinding. So if you can fit the part and tooling in the working envelope of the mill you are looking at, you will be able to machine the part. We here can also walk you through the hardening process.

What are the dimensions of the blades you need to make, can you post any photos of them?

 

[Larry$]

Might be easier/cheaper to have someone with a mill make them in O-1 then you can harden/temper them.
I have not experience with a mini mill but unless you have other uses for one......

 

[markba633csi]

Can you post a sketch of the blade's dimensions? Probably (and this is a guess) you could make them without having to buy a milling machine
if you had a bench grinder and a drill press but it depends on the shape and size
Like Ed mentioned you would machine them from tool steel like O1 then harden/temper them so they would have good wear characteristics,
stay sharp and be tough and resistant to fracture

 

[jonesrick]

First, Welcome to Hobby Machinist.

Well, depending on the hardness required, "hardened" steel will be difficult to impossible mill, especially a mini-mill. The procedure is usually to machine the part while the steel is still soft, then harden it. if the part needs any additional shaping or sharpening after hardening, it is done by grinding. So if you can fit the part and tooling in the working envelope of the mill you are looking at, you will be able to machine the part. We here can also walk you through the hardening process.

What are the dimensions of the blades you need to make, can you post any photos of them?

Hello, Eddyde. The blades are 150mm x 50mm and about 0.50 in. thick. I need to mill the 150mm side to 45 degrees. I did some research and amazingly found on Google that wood chipper blades are usually 8% chromium work steel, tool steel, or SB chipper knife steel. I've had the chipper for almost two years now and my opinion is they are very durable blades and it takes only a light filing to keep them in shape. I've put them through a grinding wheel multiple times with no adverse results, but I think I now realize I don't have to be so drastic with them. I want to make a new set just in case they do wear out eventually.
Thanks a bunch for your reply.

 

[Just for fun]

I don't have a recommendation for a mini mill, but once you get one you will find lots of stuff to use it for.

How many blades does your woodchipper have? and what are the dimensions of the blades? That is all going to come in to play when it comes to what size mill.

My woodchipper has 4 Chipper Blades and 36 Shredder Knife Blades. Mine are double sided but still it would be a lot of work to make the 36 Shredder blades on a mini mill. I bigger mill would sure make it a lot easier.

 

[jonesrick]

Might be easier/cheaper to have someone with a mill make them in O-1 then you can harden/temper them.
I have not experience with a mini mill but unless you have other uses for one......

Yeah I agree. I may take one to a machine shop and see what can be done. There is also a raw steel supplier near me that I think can provide me with the material I need. I haven't checked yet, but I've been there before, and they look like they have a lot of different stuff available. And last, I'm old and retired and looking for something to keep me a little less bored. Thus, my interest in milling, where I have practically no experience. I'm also investigating other projects available that might justify spending $2000. + on a new toy. I guess if I do find a machinist to do the work, my time on this forum will be short . We shall see. Thanks for your interest.

 

[jonesrick]

Can you post a sketch of the blade's dimensions? Probably (and this is a guess) you could make them without having to buy a milling machine
if you had a bench grinder and a drill press but it depends on the shape and size
Like Ed mentioned you would machine them from tool steel like O1 then harden/temper them so they would have good wear characteristics,
stay sharp and be tough and resistant to fracture

Yes, I would buy the tool steel, cut it, bevel the blade, tap the holes, and then harden it, which I have no idea how to do (hint). My blades are 150x50mm and about a half inch thick.
Thanks for your response.

 

[jonesrick]

Can you post a sketch of the blade's dimensions? Probably (and this is a guess) you could make them without having to buy a milling machine
if you had a bench grinder and a drill press but it depends on the shape and size
Like Ed mentioned you would machine them from tool steel like O1 then harden/temper them so they would have good wear characteristics,
stay sharp and be tough and resistant to fracture

I have a bench grinder that I've used to sharpen the blades. I don't think that would work here. I don't have a drill press, and I've done a bit of research on lathes and mills. My inexperienced opinion is that milling is the way to go this job. I'm pretty sure I can buy the steel I need, but I need information on how you would harden the finished product and if that is feasible for me.
I really appreciate the replies I've received here. Thanks much.

 

[markba633csi]

That's a fairly large part to make but a mini-mill would do it no problem. Buy the best unit you can afford.