Okay, that sounds fine. But, that's certainly not the context airsmith was operating in. He clearly indicated the OP should waste a CNC shop's time quoting parts when there was no intention of awarding the job to them. It was only to get a reference price. And, this advice comes form a guy who seems obsessed with the value of time (presumably his, not the time of others).
Originally Posted by Mcgyver
Even the idea of getting a "local" CNC shop to quote is kind of ridiculous. There are CNC shops and then there are CNC shops. Some are ill equipped to do this type work, others can do the complete part in less time than the OP can tap one end. "knock off a few bucks" could leave the OP working for peanuts.
I use to work for a guy that would take any job. I kept telling him he needs to learn which jobs not to take. He would very often brake even and very often loose money. It is not too bad to break even but you can not stay in business loosing money. I use to tell this guy to sub things out to someone that has the correct equipment just increase the price and make a profit for being the middle man but he would never do that. He would rather spend $10,000. on a new machine to do a $5000 job. That company went out of business 5 years ago.
Originally Posted by airsmith282
So far you have all contributed useful ideas, for which I am very grateful. Some of them have helped my set ups However, no one has come up with a process / time analysis to which I might relate, nor even a suggestion of what they would charge, or what they have paid to have a similar job done. I have got further with set ups and test run a few pieces and time and effort is going down. I realise that it probably is a cnc style job, but the numbers needed seem a little low, given the likelihood of set up charges. A number of local CNC shops have gone under, and others are hungry so it might be negotiable. Just being a middleman would put some dollars on the table, but I am out of work and every dollar counts, even if I dont make big dollars every hour. Should I price it as if I am a machinist doing the set ups and an unskilled monkey when using my set ups, reverting to machinists rates when something goes wrong? I do not intend to be in a race to make less than minimum wage ( $ 10 an hour hereabouts). The shop is at home, coste nothing when idle, everything is long since paid for, and when I am not working commercially I build model steam engines. I will keep you posted as to progress. Thanks David Powell.
I think the lack of information you seek should tell you something.
Ok, so the guy wants no waste. What happens if you botch a part? What is your recourse? If he's bringing the aluminum because he doesn't want to pay a markup on the materials, that's fine, but he needs to supply extra stock so the inevitable problem doesn't leave you high and dry.
How do you plan to cut 400 cylinders all within .001" of the ideal?
Does the guy know that if he measures the cylinders from one day to the next, their length will change?
How long will it take him to measure all 400 cylinders and decide they are acceptable? I assume he won't pay until then.
edit - typo city...
Last edited by Tony Ennis; 02-21-2011 at 08:03 PM.
Perhaps those here that give free quotes would do so; IF you posted a link to a drawing with ALL the dimensions, tolerances, material spec and surface finish.
Originally Posted by David Powell
The difference between a 6-32 blind bottomed at 5/8" or a thru hole makes a big difference.
Ok, heres some more---
Just did a test run 10 pieces 1/2" dia 4" long Aluminium. simply face ends and tap 6/32 to accept 1/2" of screw. length + or - ! thou. including inspect all, for length and screw 6/32 Allen head in every end with fingers as check for thread 58 minutes. This includes feeding cat and a couple of brief stops for coffee kept warm on old coffee maker in shop and probably represents my usual way of working. So, if I look at my usual answer to pricing, ie 45$ hr each piece should be charged at $4.50, Seems a lot for what he gets, but can or will others do it for any less? Any further comments. Regards David Powell.
I'm not a machinist - I am a project manager (or close enough.)
First I think that one of those every 6 minutes is an impressive rate. /thumbsup
Anyway, when the dude says, "$4.50 ea, are you mad?" What will you be able to do less of so you can charge less? For example, if the guys says he will pay $3 each, would you be able to do it if your length tolerance was +- .01"?
Or would you be able to thread quicker with a different thread? Perhaps the thread selection and length tolerance is arbitrary, and he really doesn't care that much...
Still a bit to go---
I am currently using a small rotating tailstock mounted turret with MT3 in my tailstock ( Busy Bee 13/37 lathe) Starting with work in chuck I push tailstock forward to a stop clamped on the bed, then feed the centre drill to preset zero on the handwheel dial to give the centre and a tiny chamfer, the same each time.. then I turnback one turn, spin turret one notch and drill 10 turns ( 1"), then release tailstock and pull back about 5" while winding the handle back to the start stop( a hoseclamp wrapped firmly round the tailstock barrel) so that I can change the piece without impaling myself on drill or centredrill Then I spin the turret back to centre drill position, I am right handed, but am fortunately also pretty good with my left hand and once in a good rhythm the movements flow quite well. When I get my proper Hardinge turret back, once I have it set up it will all be done with one handle, then I really will be able to break drills quickly If I get too enthuiastic!!! In the previous mass production adventure in the 90s I began making 15$ an hour and by the job folded worked up to 75$ an hour simply by improved material flow and techniques ( including rear mounted part off tools,replacing cross slide feedscrews with levers, spindle brakes, purpose made boxes to hold the parts , dedicated arbor press to assemble parts etc etc) I am not the brightest bulb in the chandelier and it sometimes takes me a while to realise where the delays exist and figure better ways to do things,but once I get a good system going I enjoy seeing the parts coming off accurately and quickly. Thanks again for the encouragement and help. regards David Powell.
Tapping on the lathe is very slow, if possible move that operation to a mill and use a tapping head. All you need for a fixture is a simple V block clamped to the table, and a toggle clamp to hold the part, while tapping. Should increase the tapping speed by a factor of 10, or better.
I would run the job a little differently on the front end, I'm set up for that type job, but the tapping would be done on a mill.