honing in action

Honing in or out?

June 2016 -

There are lots of reasons to outsource honing, so what are the key considerations for subcontracting this process?  Martin Elliott, managing director of Delapena explains.

Whilst Delapena is a master in the honing and grinding market, precision surface finishing isn’t for everyone.  A skills shortage has pushed close tolerance honing dangerously close to being a ‘dark art speciality’ and many organisations choose to outsource this process altogether.  Beyond the skills issue, there are other good reasons for this.

Low or variable volumes clearly imply that subcontract honing will be a better solution than machine purchase.  The key consideration is return on capital investment and, for some, it doesn’t make financial sense to own and run honing equipment – although it’s worth doing the calculations.  With older machinery, there is also the issue of having expertise in-house as fine tolerance work can require a lifetime of experience from the operator (note though that the latest electronically-controlled machines de-skill the process).

Short term need also drives honing towards sub-contracting.  For example in the case of a machinery failure or unusual peak in demand caused perhaps by a large contract.  Here the critical consideration – assuming quality of work – is finding a supplier with the capacity and agility to handle the project.  Contractors with modern machinery are likely to turn the work around quickest as the more recent honing machines have improved part rate considerably, without any compromise on quality of finish.

As in the previous scenario, some use subcontract honing to top up their own in-house process and this can be for volume reasons or to meet precision demands.  For example, the subcontract honing service at Delapena offers tolerances of down to one micron, which may be beyond the scope of in-house expertise.  In this case, sending fine finishing work out is a useful complement to in-house process.

Supporting bid work is another helpful role for sub-contract honing.  When a contract has not yet been won, but honed samples must be provided, then outsourcing that finishing process is an obvious winner.  In this case, working with the sub-contractor can demonstrate the quality and perhaps also the repeatability of the work.  Again, quality of the sub-contractor’s machinery will play a part in demonstrating this.

The material to be honed can also be a determinant for subcontracting; not all organisations have the capability to hone all that is possible: Aluminium, brass, titanium and hard steel can be honed as standard, with harder materials such as ceramics and inconel also within honing capability.  These more ‘exotic’ materials may require a specialist subcontractor. Delapena has an abrasive development facility and so can produce job-specific abrasives, currently offers without additional charge, as part of its subcontract service.

Beyond just outsourcing the whole process, it is also possible to source support for elements of honing, such as tool head refurbishment.  This is a common requirement for automotive OEMs, giving the volume of their honing work and so this alone may be useful to send out.

Another consideration for subcontract honing is to use it as an interim measure as part of a migration to honing in house.  This can provide a risk-free strategy that safeguards production and supports a smooth transition to honing as part of an in-house process flow.

Typical parts suitable for sub contract honing are spools for hydraulic and servo valves, cylinder liners, bushes, gears, carbide dies and ceramic sleeves. The are often sent out due to the hardness of the material or size of diameter. 

Expanding the scope for subcontract honing, this method is a good way to remove material, to replace internal grinding and to create tight geometry and an exact surface finish, all to a consistent standard.  New applications appear every day.