Guides / Choosing a Supplier
Choosing a Shop to Machine Your Delrin and POM Parts
September 21, 2026
Most acetal parts are simple enough that any competent shop can make them once. The difference between suppliers shows up on the second order, on the tight tolerance, and on the part that has to hold a dimension six months later.
These are the questions that separate them.
1. Which acetal grades do you keep in stock?
A shop that machines acetal regularly holds natural homopolymer and copolymer rod in common diameters and plate in common thicknesses. One that does not will order in for every job, and that is a week of lead time on every order.
Ask which diameters and thicknesses, not just which grades. A shop with the right grade in the wrong size is in the same position as one with no stock.
2. Do you anneal in house or send it out?
In house means a day. Sent out means several. For a tight tolerance part this is the difference between a two week and a four week lead time, and it will not show up in the price.
If the answer is “we do not anneal”, that is fine for simple parts and a problem for thick ones. Know which you have.
3. What temperature do you inspect at?
A shop that machines plastics daily will answer this immediately, usually twenty degrees C, and will mention letting parts settle first. A shop that hesitates has probably been measuring warm parts and getting away with it.
This one question tells you more than most capability lists.
4. What tooling do you run for plastics?
You are listening for sharp positive rake, polished flutes, few flutes and dedicated plastic tooling. A shop that says it runs the same tooling as aluminium can still do good work, but a shop that has never thought about it will deliver smeared surfaces.
5. How do you hold thin acetal parts?
Soft jaws, vacuum plates, sacrificial fixtures. If the answer is a standard vice, expect marked and distorted parts on anything thin.
6. What material documentation can you supply?
Material certificates, batch traceability, food contact compliance declarations if relevant. A shop that supplies food or medical equipment produces these without a special request. A shop that tells you it is fine and has nothing to send is telling you something.
7. What is your first article process?
You want a dimensional report on the critical features, the inspection method and the temperature, and a clear statement of what was measured. Not a certificate of conformance with no numbers.
8. What happens when something is out of tolerance?
Ask before you need to know. A shop with a clear answer about containment, rework and replacement has thought about it. A shop that says it does not happen has not.
9. Who answers the technical questions?
On an acetal part with a fit, a grade choice or a tolerance question, you want to reach someone who can discuss it. A supplier where every technical question goes through a sales contact and comes back two days later will cost you more in schedule than in price.
Red flags
- A quote with no grade named. The shop has not decided what it is making.
- No mention of inspection temperature on a tight drawing. The tolerance discussion has not happened.
- Promising plus or minus 0.01 mm across a large plate. Not realistic in acetal over a long face, whatever the equipment.
- No pushback on a drawing with an obvious gap. A good supplier asks questions before quoting.
- A price far below the others with no explanation. Find out what was left out.
What to do on a first order
- Order a small quantity first, even if you need more
- Ask for first article inspection on the critical features
- Ask for the inspection temperature in writing
- Measure the parts yourself, at a known temperature, after they have settled
- Keep one part as a reference for the next order
That sequence costs a little time and catches most of what goes wrong.
Making quotes comparable
If quotes come back far apart, the usual cause is that the drawing left a decision open. Before choosing on price, ask each shop what it assumed about the grade, the general tolerance and whether a stress relief cycle was included. Then either fix the drawing and requote, or pick knowing what you are buying.
How we fit into this
We are a matching service, not a machine shop. We read your RFQ and send it to shops whose machines, stock and part size fit, up to three. They quote you directly and you place the order with whichever you choose. We take no commission on the order.
That means we have no reason to steer you to a particular shop, and no reason to match a part with a shop that would have to learn on it.
Ready to find one? Send your RFQ with the drawing and we will match you within 24 business hours.
Frequently asked questions
Does it matter if a shop mostly machines metal?
It can. Plastics want sharp positive rake tooling, different workholding and an understanding of how a part moves after machining. A metal shop with a plastics habit is fine. A metal shop cutting its first acetal job usually learns on your parts.
What should I ask for on a first order?
A first article inspection on the critical dimensions, the inspection temperature used, and a material certificate. Those three tell you more about a supplier than any capability list.
Is the cheapest quote usually the problem?
Not necessarily, but find out why it is cheapest. If it is cheapest because the shop did not include a stress relief cycle the drawing implied, you will find out later. Ask what each shop assumed before picking on price.
Need a quote for this part?
Send the drawing. We match you with up to 3 shops that machine acetal and reply within 24 business hours.
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