Which housing, and which of its surfaces, is being cleaned?
Spindle housings are not one part. On a machining centre the headstock casting is bolted to the column and carries the spindle cartridge, and the outer shell the operator sees is painted steel or a stainless shroud. On a grinding or turning machine the housing may be a smaller casting with a belt cover above it. Send photographs of the housing from two angles with the machine shut down, and mark the surfaces in the photographs: the outer casting faces, the belt and pulley cover, the tool-change area nearest the spindle nose, the coolant nozzles and their hoses, and the top faces where swarf settles. Send the photographs with the marked list: a supplier reading a part name alone will recommend for the whole assembly, while a supplier reading a marked surface list recommends for what you can actually reach.
Ask the question the other way round, as an exclusion list. Encoders and linear scales, bearing gaps, seal lips, the spindle bore taper, cable glands, connector hoods, labels and data plates, and any vent or breather opening belong on the page as surfaces that must not be sprayed. Whether those exclusions leave enough area to clean at all is the first real feasibility test, and it is answered from your own machine, not from a catalogue.
What is the deposit, and how long has it been there?
The duty on a spindle housing is usually a mixture: cutting oil or mist film over a wide area, way oil that has crept down a face, hydraulic bleed near a fitting, and dried coolant paste where splashing has repeatedly landed and dried. The difference matters because a mist film and a dried paste are not the same job, and both behave differently on a warm surface. Cool metal that has come off a shift is still warm enough to flash a wet steam off quickly, and hot deposits soften differently from cold ones. Write down the deposit per surface, and say whether it is fresh or baked on.
Say how swarf is involved. Swarf fines bound in oil form a crust that water moves rather than lifts, and those fines travel with run-off to wherever the run-off goes. A supplier who knows the deposit contains particulate will handle containment differently from a supplier who assumes oil only. If your cleaning exists partly to control particulate, that requirement outranks speed, and it belongs in the enquiry in one sentence.
Describe the interval between cleans. A housing cleaned every week and one cleaned once a year are two different duties even when the soil type is identical, and the cleaning window available on a production machine is a site fact you supply, not something the equipment selects for you.
Which machine condition and which utilities exist at the position?
Cleaning a spindle housing happens inside a live shop, so the questions shift to the site. Is the machine tagged out for the work, and who signs it back? How long is the window? What is the floor around it, and where would water go? Is there a drain, a bund, or only a floor drain shared with coolant handling? Oily run-off from a machine cleaning has to be collected somewhere, and that is normally your obligation as the site, not an inclusion in an equipment quotation.
Then the services at the position. A fixed machine needs a confirmed supply at the socket it will actually be plugged into, and access for the machine itself through the aisle and doorway to that position. A mobile unit changes where and when work is possible, but it changes other things as well, so ask for the figures that apply to the exact configuration being quoted rather than assuming a value carries across a range. The published rows for one fixed model in the Fixed Steam Cleaning Machine PowerDe HW02 page - heating power, supply voltage, tank volume and material, overall dimensions including handles, and the tap-water inlet arrangement - are page records for that unit only, and a quotation should name the rows that apply to your position.
Water quality is part of the same question set. Ask what scale is expected on a mains supply, whether an inlet strainer is fitted, and what descaling duty the maintenance plan assumes. Hard-water work is the least discussed and most often regretted line on the sheet.
What is near the housing, and what must stay dry and cool?
This is where a spindle housing differs from a flat panel. Around it sit electrical enclosures and cable entries, pendant controls, cable carriers, way-cover seals, linear guides and ballscrew covers, quick couplings, and the vents on drives and spindle-related motors. Heat and dwell are as much a constraint as water: seals, gaskets and plastic components are the parts that fail quietly after cleaning, long after the machine has gone back into service.
Ask the supplier in writing what protective features exist on the machine being quoted, and - more usefully - what they do not cover. Ask which mode suits work near an electrical enclosure and what the operator does differently in that mode. The machine builder's own cleaning restriction, if the manual carries one, outranks any cleaning preference; put that restriction in the enquiry and ask the supplier to work inside it.
Then fix the closing condition. A cleaning task that ends with a wet surface near an enclosure has not finished. Name the dry check, who performs it, and what has to be true before the machine is handed back - and make the machine owner the person who confirms return to service.
What has to be true before anyone accepts the method?
A supplier recommending equipment for a spindle housing should be able to answer a narrow acceptance question: what will be visible on a test area, and who decides whether that counts. Write the acceptance lines per surface class before the trial rather than after it, because a general cleaning result and a defined acceptance standard are two different things, and only one of them can be signed.
Ask for a bounded trial on one representative machine, with the deposit, the exclusion list and the drainage plan written before it starts. Record what was removed, what was not and why, the time the passes actually took, and the number of refills and walks between the machine and the supply point. Photograph the test areas before and after. Those records do two things: they make the recommendation enforceable on paper, and they become the baseline the next machine family is judged against.
State plainly in the enquiry that a rate, a time saving, or a cleaning quality claim should not be assumed on your behalf. Where the published product pages describe vehicle, parking-facility and medical duties rather than a metalworking scenario, the fit for your spindle housing has to be proved on your machine with your deposit, and written down - the site's own category for machine tool steam cleaning is the starting point for that conversation, not the end of it.
What should every supplier be asked to put in writing?
Send the same question set to every bidder so the answers can be read side by side. That set should ask: which published specification rows apply to the position described, and on which page; what is included and excluded for site preparation before delivery; how the machine is connected at the position and who carries out that connection; which protective items come with the unit and where its limits stop; the maintenance interval, the wear items and the parts prices; who trains the operator and against which document; and what the supplier needs from you to make any of those answers firm.
Score the answers as stated, qualified, or missing. A missing answer is information, and it usually becomes a variation order later. Where your shop has a genuine non-standard condition - a machine that cannot be isolated on the normal window, a housing with no clear exclusion boundary, run-off that cannot be routed to a drain - the route is described under customized steam cleaning equipment, and it starts from the same facts the standard questions ask for.
Four points the supplier has to settle before a recommendation is useful
A recommendation you can act on names four things. The surface list and the exclusion boundary for the housing. The deposit type and interval, per surface. The utilities, access and drainage arrangement at the actual position, measured by you. And the acceptance standard the trial is judged against, with the person who signs it. A supplier asking for those four before quoting is doing the job properly. A supplier who recommends a machine before asking for them is quoting a catalogue, and the cost of that guess lands on your floor, in your production window, with the housing still dirty.
