Guides / For Shops

How to Win Motor Part Work: What Buyers Actually Check

Written by the sourcing desk that reads your RFQPublished September 25, 2026How we write these

Motor parts are good work for the right shop. The volumes repeat, the drawings are stable for years, and the buyers are engineers rather than procurement portals. The difficulty is that a motor part looks like ordinary turning and milling right up until the one feature that is not, and buyers have learned to test for that before they award anything.

Here is what they test, in the order they test it.

What a motor part buyer is actually worried about

Not price, first. Price matters, but it is compared after the buyer has decided who is capable, and buyers narrow that list faster than most shops expect.

The worry is specific: a bearing seat that is within tolerance on the report and wrong in the assembly. That failure is expensive in a way most machining failures are not. It does not show up at incoming inspection. It shows up as noise or as a bearing that has moved, weeks later, in a motor that has already shipped.

Everything a buyer asks is a proxy for that one risk.

The question that decides it

How do you check a bore?

This is the question. Not the machine list, not the certificate. How do you check a bore.

A shop that machines bearing seats answers with an instrument and a method: a bore gauge zeroed on a setting ring, an air gauge, a CMM with a stated routine, a roundness tester for form. It says whether the check is in process or after the fact, and it mentions letting the part come to temperature before measuring.

A shop that answers “we measure everything” has told the buyer nothing, and the buyer reads that as a no.

If you own the gauge, lead with it. Put the instrument and the method in the first reply, not in a capability brochure three emails later. It is the highest value sentence you can write to a motor part buyer, and most of your competition does not write it.

The second thing they check: whether the part keeps its reference

Motor housings and end bells usually have two or more features that must share an axis. A bearing seat and a spigot register. Two bearing bores at opposite ends.

Buyers who have been burned once will ask, in some form, how you plan to hold that relationship. The good answer names the setup: both features cut in one operation, or a second operation on a fixture built for the part with the clocking method described.

If you have a turn mill with a sub spindle, this is where it earns its keep and you should say so plainly. If you do not, say how the fixture works. An honest fixture plan wins against a vague claim of high accuracy every time.

What loses the job in the first email

Quoting without a single question. A motor part drawing nearly always has something open: the blank, the operating temperature of an aluminium housing, which datum a runout references, whether material is to be left for balancing. A quote with no questions tells an experienced buyer the drawing was not read.

Turn this around. One or two sharp questions in the first reply is the strongest signal you can send, and it costs nothing. It also gets you a more accurate drawing, which protects your own margin.

Saying you can hold anything. Every process has a limit. Naming yours reads as confidence. Avoiding the question reads as a shop that will find out on the first article.

A silent week. Buyers work to an assembly date. If you cannot quote by Thursday, say on Monday that you cannot, and say when you can.

Hiding the subcontract. Grinding, heat treatment, anodising, plating and balancing leave the building at most shops. That is normal and buyers know it. What damages you is a buyer discovering it when a lead time slips. Name the operations that go out and the lead time they add.

Quoting a housing without guessing

Five things set the price on a machined motor part, and four of them are usually ambiguous in the RFQ. Ask about them before you price.

1. The blank. Bar, tube, plate, a casting the buyer supplies, or a casting you source. This moves the number more than the geometry does, and buyers frequently have not decided.
2. The fit class on the seats. H8 and H7 are different jobs on your floor. If the drawing gives a diameter with no class, ask rather than assume the tighter one.
3. Which features must be concentric, and to what. This decides whether the part is one setup or two, and whether you need to build a fixture.
4. Surface finish, and where. A blanket Ra 0.4 sends the whole part through grinding. Ask whether it is really needed on every diameter, because often the buyer copied a title block.
5. Batch size and annual quantity. Both, not one. The first sets how the setup spreads, the second tells you whether to propose soft jaws or a dedicated fixture, and whether a casting conversation is worth having.

Asking those five is also a sales act. A buyer who answers them has spent fifteen minutes on your quote and is now invested in it.

Where to propose an alternative, and where not to

Suggesting a cheaper route is how a shop turns one job into a relationship, but only on the right axis.

Good to propose: a different blank, a looser class where the bearing table allows it, moving a finish callout to only the surfaces that need it, a small geometry change that removes a setup, ordering ahead to spread setup across a larger batch.

Not yours to propose: the fit the bearing maker recommends, the balance grade, anything that changes how the motor runs. A buyer will hear that as a shop trying to make a part easier for itself, even when it is right.

The line is simple. Propose changes to how the part is made. Leave changes to what the part does with the person who designed it.

Certificates, honestly

ISO 9001 is a baseline that opens doors and differentiates nothing, because most of your competition holds it.

IATF 16949 is required for automotive production programmes and irrelevant to everything else. If you hold it, say so and say which programmes it covers. If you do not, do not treat it as a gap. Industrial motors, pumps, fans, appliances, robotics, power tools and prototype work do not ask for it, and that is the larger share of motor part requests in the market.

What outperforms both, in a first reply, is an inspection report from a past job with the customer details removed. It shows you record what you measure, which instrument you used and who signed it. Very few shops send one unprompted. The ones that do get remembered.

A first reply that wins work

Short, and in this order:

1. Two specific questions about the drawing
2. The instrument and method you will use to check the critical feature
3. Whether the part is one setup or two, and why
4. Any operation that leaves your building, with the lead time it adds
5. The price, with the assumptions it rests on stated in one line each
6. What you would need in order to quote it lower

Six points. Most shops send one, which is the price. The gap between those two emails is most of what decides who gets the order.

If you want motor part requests without chasing them

This site matches motor part RFQs with shops. You see an anonymous preview of a request first, with the part, material, size, quantity, tolerance, region and deadline, and you decide whether to take it. You pay for the request, not the order, and you deal with the buyer directly afterwards.

The checks a shop clears before it sees a request are the same ones above, written out in full on the vetting page, including the parts we cannot verify. If that sounds like the kind of work you already do, register your shop.

Standards and references

1. ISO 286-1, ISO code system for tolerances on linear sizes. The H and k classes referred to in the gauging section.
2. ISO 9001, Quality management systems. Requirements. Referenced under what certificates do and do not carry.

Figures on this page are typical ranges drawn from the standards above and from ordinary shop practice. They are not a specification for your part. The shop that quotes you confirms what it can hold on your geometry.

Frequently asked questions

Keep reading

• Bearing Fits, Concentricity and Runout: Tolerances That Matter in Motor Parts
• How to Choose a Machining Supplier for Electric Motor Components