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  1. #1
    Join Date
    Mar 2013

    Looking for a small CNC machine shop

    I am the owner of a small husband/wife company that makes small rocket motors for hobby use. We are looking for a new machine shop to make 7 to 10 different parts, preferably close to the Springfield, MO area, but our last shop was in South Carolina. I'd like to be able to visit sometime or drop off/pick up materials in person if you were close. We are 1.5hrs from Springfield, but in reality, you can be anywhere in the country.

    We really need a small operation that does consistent quality work and has extremely low overhead in order to keep costs down as low as possible. Time is normally not an issue, meaning we don't email on Monday and ask for them in hand a week or two later. I have waited several months for parts knowing the price didn't pay for expediency, however 4 to 8 weeks has been more typical for us. I'd like to find one shop to make all the aluminum parts since we often send several different parts to be plated at the same time to save on plating and shipping costs.

    -Five of our parts are made from 6061 T6 or T6511 aluminum and currently range from ~1"OD to 2.75"OD. We can supply the materials if need be.
    -Two parts currenly are made from thick walled LE (linen) phenolic convolute tubing and we supply this material. I realize that some places will not want to machine this material but we do have parts made from it.
    -Knurling on three aluminum parts is required.
    -Trepanning is required on one part currently but may expand to larger parts. See here. This part is 2.730"OD x 2.600"L and needs to be made for around $20. The last run of these was done at $15.50 for 96 pieces. Admittedly this was a very good price and I know he was helping us out because he was in the hobby himself, however I'd still like to have these made for around $20 in the future.
    -I do prefer a smooth, slow finish cut/pass so that there are not easily visible machine lines/grooves on the parts surface. It makes for easier clean up after firing a motor.
    -We hardcoat all of our aluminum parts so after machining, they have to be packaged VERY securely in such a way that the platers can easily unpackage all parts and then easily repackage them the same way for return shipment back to us. We no longer laser etch parts. It's just too expensive.
    -External threading is required on one part and 1/4-20 and 3/8-16 thread taps are required on others
    -Most tolerances are +/-.005" but some dimensions like o-ring glands are +/-.002".
    -We do small runs of parts from 65~100 pieces on larger more costly parts up to ~500 pieces for the smallest parts.
    -Because we sell to hobbyists and not the government, our prices have to be kept very low to be competitive with our competition who does have government contracts. We also have dealers that we must deeply discount hardware parts which takes away even more profit margin.
    -We do not require any ISO certification of any kind.
    -We just need someone who does quality machine work, knows how to communicate well, does not assume anything but instead asks questions, and can make smaller runs of parts at a affordable prices.

    Here is a drawing of a part that has since been very slightly modified, but our recent run of these parts earlier this year was done at $5.50/piece (material and machine work included) for 524 pieces. Again, I realize that this is/was a very good price, but I don't need to waist anyone's time getting quotes at double or triple this price.

    Anyway, if you think you can service our needs from the above information and do so at very competitive prices, I would like to hear from you. Feel free to throw a figure out for the drawing above, but realize that we have several hundred on hand right now. I'm just using it as a reference/guide.

    Feel free to ask questions here if I have left out any information that would be more helpful to others.
    Thank you for your time and consideration.

  2. #2
    Join Date
    Mar 2013

    Re: Lookng for a small CNC machine shop

    I forgot to add, I am happy to send you a few prints if you would like to send a quote our way. Currently, I only have the need for one of our parts to be made (the threaded one) but others will eventually follow.
    Thank you.

  3. #3
    Join Date
    Mar 2013

    Re: Lookng for a small CNC machine shop

    ianagos, please clear out your inbox. It is full.

    Deshengruimac, US manufacturers only please.

    We only purchase US made materials and parts.

  4. #4
    Join Date
    Jul 2018

    Re: Lookng for a small CNC machine shop

    Deshengruimac - Hi - your page says that 6063 is stronger then 6061 in UTS and YS this is not true. You need to fix that. Peter

  5. #5
    Join Date
    Mar 2013

    Re: Lookng for a small CNC machine shop

    Sorry for any delays. We had a busy day yesterday and I didn'thave time to respond to any messages.
    I just sent out 5 more reply emails to those of you who have contacted me.

    Thank you everyone. I'll be sure to post here again when we make a decision to let people know.

  6. #6
    Join Date
    Mar 2013

    Re: Lookng for a small CNC machine shop

    I'd like to add some more details for those of you whohave requested prints, as I've had a few questions from some of you. So, I'd like to make sure we are all on the same page.

    All dimensions are before plating.
    They are plated by Pioneer Metal Finishing which are plated at a 0.0021" with a +/-.0003" tolerance. So they need to be packaged extremely well for shipping not once but twice.
    I can't find laser printing services affordable enough so it is no longer done.

    I don't have a tolerance on the threads other than what is allowed for within the thread class that is called out. I don't know for a fact if prior machinists have used an oversize H tap or not for internal threads.
    For the 1.5" external thread, I have a steel master external thread ring, a GO/No GO gauge so to speak. It fits the part after plating with very little play. I can probably send you a few slugs to do some practice thread runs with to match it.
    I would send the steel master along with a finished part to the machinist, and then on the phone, go over the entire part to explain the purpose of each feature so that you have a crystal clear picture.

    The 1/4-20" hole goes thru the 54mm Standard Bulkhead. The Extended version is solid or plugged with a 0.055" thickness at the lowest point.
    The knurling on the Standard version is not a critical dimension. It is solely use to aid in the parts removal from a motor case. The important thing here is that the knurling gives a good bite and grip.
    It can be almost even with the OD of the mating surface or raised.
    As far as the .850" knurling depth, that can be flexible if it is difficult to turn it that close to the 1.920"OD shoulder.
    The rounded corners comment is because I once had a machinist want to program in a radius for the breaks rather than a simple sharp 45 deg break. If it wasn't done perfectly it would leave a tiny groove on a portion of the radius.

    On the snap ring. It's a standard HO-0131-PA retaining ring in a 1.25" bore. Use the drawing at the bottom of this page. https://www.mcmaster.com/99142a500

    I hope this helps.

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