Machinists will understand

[mrblaine]

We see sloppy work from local machine shops fairly often. They get into a hurry and quality goes down.

As soon as you bring it to their attention, they always seem to "fix" the problem and all is well again.

They just got sloppy or in a hurry and tried to blame the cut off saw. I bet the rest of the batch is nearly perfect.

Just out of curiosity, do you supply the machine shops with a drawing that has tolerances, or just a sample? We have got into some pretty big pissing matches with a couple shops over tolerencing issues.

If they listen, take notes, and pay attention, I've bought enough machine time to get them to build from the sample easily, effectively, and at the lowest cost for both of us possible. For this part, it is simple. I don't need the saw cut face machined flat. The hole is clearance for 9/16" or .570 or so. The slot is critical in overall length, width and height so it is the only close tolerance section of the part and even that isn't hard.

I always go over the part, how I need it done, where the tolerances matter, and stand there with a sample in hand while we go over it. I stay after it until I see the light bulb turn on and they understand my needs. Again though, they have built these before, it wasn't an issue, they will get this one correct, but damn, 50 thou?

In perspective, I do business with 4 different machine shops currently depending on the part. I do about 100 grand a year with one of them.

 

[Dan Carey]

I would have made the part in my lathe then milled it. Everyone knows a bandsaw won't cut straight.

 

[mrblaine]

I would have made the part in my lathe then milled it. Everyone knows a bandsaw won't cut straight.

How many would you like to make?

 

[Dan Carey]

You send me a detailed print and I will build you one (1) part to within +/- .0001"

 

[astjp2]

They will fix them. They have done them before and they will be right when I get the full order. I just couldn't get my head around that big of an error.

New employee?

 

[mrblaine]

New employee?

Nope, same guy who has been there for years.

 

[astjp2]

You send me a detailed print and I will build you one (1) part to within _+ .0001"

What kind of equipment are you running? I worked on $1Million mazaks that only held .0002 consistently. Surface grinder will hold that tolerance but many lathes are not as precise if they are working with high production counts.

 

[Dan Carey]

Come on now, if you are a machine operator you know it can be done on a manual machine.

 

[mrblaine]

You send me a detailed print and I will build you one (1) part to within _+ .0001"

I need them in quantities of 5-600 at a time. They are little more than a fancy washer. I don't currently make or want to make any parts accurate to a tenth or even 5 tenths. That is a ridiculously close tolerance for a washer that fits in a slot. The part is worth about 4 bucks. What will it cost to get them done to a tenth tolerance? Triple that?

 

[mrblaine]

Come on now, if you are a machine operator you know it can be done on a manual machine.

Not at any affordable production level.

 

[astjp2]

Come on now, if you are a machine operator you know it can be done on a manual machine.

It can, but who wants to build 1000 parts on a manual lathe?

 

[Dan Carey]

LOL, I'm retired and not looking for a production job. I just have the equipment and knowledge. I just offered to build an accurate sample. Actually I didn't expect to being taken up on the offer, but had I, I would have built it just for the heck of it. I was a machinist in the US Navy.

 

[mrblaine]

LOL, I'm retired and not looking for a production job. I just have the equipment and knowledge. I just offered to build an accurate sample. Actually I didn't expect to being taken up on the offer, but had I, I would have built it just for the heck of it. I was a machinist in the US Navy.

The accurate sample is saw cut on one face, machined to flat on the other with a reasonable amount of parallelism between the two. It doesn't need to be more accurate than that between the two faces. I can handle .003 out of parallel, I can't handle .050.

 

[ranger101]

This man needs two op’s and a detailed print to make a single washer? Lol

What kind of equipment are you running? I worked on $1Million mazaks that only held .0002 consistently. Surface grinder will hold that tolerance but many lathes are not as precise if they are working with high production counts.

Hell I hold .0002” on a wire EDM machine(my specialty). I’m a micro machinist, so holding .0001” is just another day in the shop. We have two Yasda’s that we consistently hold .00005” with almost every day. Our newest machine has .000005” adjustments which is just absolutely crazy. Yes, 6 decimals. We don’t even have a way to measure that. We have to use high dollar microscopes to measure our parts because of the human error involved in the measuring process. We’re cutting slots as small as .0008” at times, with .0008” endmills that you can hardly look at without breaking. Holding these tolerances is actually pretty easy to do, but there’s a lot of science and trial and error that’s gone into figuring this stuff out. It’s all about temperatures at that level. Way oils have their own coolers, new coolant must be sitting out in 5gal buckets for 8hrs minimum etc. We’re also in a temperature controlled shop that stays 75* year round.

 

[jesseshoots]

Hell I hold .0002” on a wire EDM machine(my specialty).

Wire EDM is some of the coolest stuff I've seen in a while! What kind of stuff requires .000005” adjustments?

 

[mrblaine]

This man needs two op’s and a detailed print to make a single washer? Lol

Not the man, the shop. He doesn't have a bar feeder and live tooling that would allow it in one operation and I don't need that many at a time.

 

[ranger101]

Not the man, the shop. He doesn't have a bar feeder and live tooling that would allow it in one operation and I don't need that many at a time.

I was referring to someone else, but I didn’t realize they had the boss in the center like that.

 

[ranger101]

Wire EDM is some of the coolest stuff I've seen in a while! What kind of stuff requires .000005” adjustments?

I program/operate two wire machines and I love them. Kinda got thrown into it one year and it was either sink or swim haha I do a lot of high angle stuff which usually leaves you with an awesome looking drop.

Wish I could tell you what kind of parts need six place adjustability haha I wish I even knew. We just make them to the print. Sometimes we have .0002” tolerance, sometimes they want zero tolerance.

 

[mrblaine]

I was referring to someone else, but I didn’t realize they had the boss in the center like that.

I tried them as laser cut blanks but the dross and hardened areas from the cut eat up their tooling too fast and they won't buy specialized tooling for a simple job like that one. Now we just saw cut to rough length and take them down in the mill.

 

[mrblaine]

I program/operate two wire machines and I love them. Kinda got thrown into it one year and it was either sink or swim haha I do a lot of high angle stuff which usually leaves you with an awesome looking drop.

Wish I could tell you what kind of parts need six place adjustability haha I wish I even knew. We just make them to the print. Sometimes we have .0002” tolerance, sometimes they want zero tolerance.

My best machinist that moved out of state made some parts for very high speed air drills. Something along the lines of 50,000 RPM and he related similar. Controlled temps, tooling, material, machines, and coolant at the same temp. Machine running to warm up before they started making parts and he was only holding 5 tenths.

The best wire video I've seen is an older one with the snowflake. Really impressed the first time I saw it.