[Hamzter]

Hi All,

I'm currently making a small 2 part mold that is to be dowelled together, the holes for the dowels are to be reamed to Ø4, however the part also needs to be carburised. I'm concerned the carburising will throw off the hole diameter, what's the best way of making this hole? I'm thinking of carburising the part first, then drill and chamfering with carbide tools, and finish off with a HSS reamer. Any other ideas? The material is 080A15 (equivalent to SAE 1016) and it will be case hardened to a depth of approximately 0.5mm.

Thanks

[mactec54]

Hamzter

You have to finish the holes before case hardening, after heat treatment, you would lap the holes with diamond lapping paste to suit the pins you are using, Ideal if you had a cnc grinder you would grind the hole positions after heat treatment

[mactec54]

Hamzter

You can also fit premade hardened bushings in one side, which is a better way, why are you wanting to case harden the parts, if you made them out of a good quality tool steel, you most likely will not need to heat treat your parts

[Hamzter]

Hi Mactec,

The person I'm doing the parts have is insisting they're hardened for wear resistance. I should point out it's the mold cavity that needs hardening, it's fine if the dowel holes are unhardened. Would you still advise finishing the holes before carburising?

Thanks

[mactec54]

Hamzter

Yes I would & lap them after, you still could get a misalignment of the holes, it depends on the quality of the steel, & the heat treater, you will have to grind all faces after the heat treatment as it will distort all the faces case hardening is not the norm for molds

I would talk to your heat treater, you may be able to rough in the holes & chamfer, the heat treater can plug the holes so the they don't get a case on them, any hardness in the hole area, & you will not be able to touch it with a HSS reamer

[dertsap]

hit it with a solid carbide reamer afterward

[juergenwt]

In a case where the dowel pin holes need not to be hard or where we would worry about distortion in heat treating (case hardening), we lay out the approx. position of the holes and use a dap of a product called "Condursal" on each side. This prevents carbon from entering the steel and the covered area stays soft. Holes can than be drilled and reamed after heat treating. We have used this product for many years on our parts and in the tool room. Before we used to copper plate the part and removed the copper in the area to be case hardened. After heat treating all the copper was removed.
Duffy Company: Condursal Stop-Off Paints
Duffy Company: Condursal 0090