Chrome builds on all surfaces exposed to it so it is crucial to understand the impact that chrome plating will have on the part’s dimensions before you start specifying the process for production to avoid having to carry out rework or scrap parts.
Chrome Builds on All Exposed Surfaces
The chrome solution is poured over all exposed surfaces of the part. There is an even build up of material on all surfaces that are left unmasked. The typical industrial build of chrome is between 25 microns and 500 microns, depending on the application for which the part is required.
Plan to Plate Oversize Then Grind Back
Typically parts are machined undersize prior to hard chrome plating, and then finished to size using a series of grinding stones. This way you can control the final dimensions of the part accurately. You have to cost and time allow for this, however.
Masking Controls Where Chrome Lands
For Chrome Plating, any surface that you do not wish to plate must be masked prior to plating. This will include threads, seal faces, bore(s) that are to be held at exact size. This should be discussed with your plating supplier prior to processing to confirm suitability for your specific part.
More on Hard Chrome Plating can be found at www.poeton.co.uk/advanced-treatments/apticote-100-hard-chrome.
Realistic Tolerances After Finish Grinding
A realistic allowance for the finish ground dimension of plated surfaces is plus or minus 5 to 10 microns. Information on dimensional measurement and surface metrology can be used to determine the requirements for the finished part and for its verification.
Tell Your Supplier the Finished Size You Need
When ordering a part for chroming inform the plating house of the required finished size and they will advise on the most suitable deposit thickness. They will also advise on the required grinding allowance. This will save a lot of time in avoiding incorrect assumptions regarding the pre-chroming dimensions and sizes.
A little planning at the drawing stage is all that is needed to make hard chrome plating a straight forward process.