couple of questions regarding tube thickness, brazing and milling

[bencooper]

I'm just guessing at 1200, by the way - I normally use the top speed on my drill, but not always at full throttle. I find I can feel if it's sawing nicely through or not, and vary speed and pressure as I go.

I guess what this shows is there's no right answer ;-)

[steve garro]

I'm just guessing at 1200, by the way - I normally use the top speed on my drill, but not always at full throttle. I find I can feel if it's sawing nicely through or not, and vary speed and pressure as I go.

I guess what this shows is there's no right answer ;-)

Yes there is - you just don't know it.
You just said so.
You're just using a dewalt hand drill and a jigger & guessing, right?
Day & night from a real milling setup.
My mill has been set a 240RPM for thousands of tubes.


18bikes has it going on right there, great suggestions esp as per thickness = a 7/4/7 OX Plat will be way more scary then a 1/7/1 Supertherm even though they are the same alloy.

- Garro.

[bencooper]

Yup, you're right, I've been just guessing for 15 years of professional framebuilding. But hey, thanks for your patronising answer

[steve garro]

Yup, you're right, I've been just guessing for 15 years of professional framebuilding. But hey, thanks for your patronising answer

Your words, not mine.

I'm just guessing at 1200, by the way - I normally use the top speed on my drill, but not always at full throttle. I find I can feel if it's sawing nicely through or not, and vary speed and pressure as I go.

I guess what this shows is there's no right answer ;-)

I'm not a patronising type of person, but guessing/assuming is not fit for a thread aimed at actual dissemination of factual knowledge to build object on which peoples' lives depend, right?
You don't own a mill, right?
- Garro.

[bencooper]

I do own a mill - it's a small one so not brilliant for mitring. I also have a couple of lathes. Is this a "I own more expensive kit than you do" willy-waving contest?

Okay, a simple thought experiment. Take a chainstay - most people can hacksaw through a chainstay in 30 seconds or so, without causing any problems at all, right? Now a hole saw is just a hacksaw blade welded into a circle, and is about the same effective length, so whats the difference between hacksawing though a chainstay in 30 seconds and hole sawing through one in about the same time?

[steve garro]

A) "I own more expensive kit than you do" willy-waving contest?

B) so whats the difference between hacksawing though a chainstay in 30 seconds and hole sawing through one in about the same time?

A) That is SO not me.
I barely attach any value to objects.
People, yes.
Objects, no.
I'm not going to win any "Willy-Waving" contests (That's so cute, BTW)

B) Accuracy, repeatability, less wear & tear on the body, the ability to miter both at once to perfect length & with offset on the BB shell?

I'm not busting chops, I just so want this to be a source for reliable info.
- Garro.

[bencooper]

Okay I misunderstood your comment about a mill. As I'm sure you know, results are what matters, and you can get equally good mitres with a hand file, a hole saw, a milling cutter or a full CNC setup. The only difference between those methods is the speed of manufacture, not the quality of the result.

My hole saw setup provides high accuracy, repeatability, and the ability to miter at the correct length and offset. What it might do, because hole saws aren't designed for this job, is go through cutters at a faster than optimal rate. But they're so cheap that's not a big issue - if a £9 hole saw only lasts 1/4 the time a £120 milling cutter does, I still win on price.

I like this to be a source of reliable info too, and an important part of providing reliable info is describing methods and techniques that have been tested and work.

[EnginCycles]

Here is something I will add that might shed some light on the situation of milling.

The bigger and more robust the machine the slower you can run the RPM and the harder you can feed (or feed rate). The more robust fixture is only as robust as the weakest link between the part and the floor. If the machine is clapped out and light duty the most robust fixture will only tell you where those machines are clapped out. A weak fixture on a totally stout machine will also tell you the fixture has limitations. With all that said the speed rates and feed rates are going to be in the ball park of the suggestions but the final # will be adapted to the end user. My set up is almost always running at 293 RPM with a feed rate of 1 inch per minute. Power feed is the key to running a slower RPM since it can be controlled to keep feeding. The power feed also requires EVERYTHING to be robust since it won't stop and your emergency stop (you panicking and hitting the stop button) will be too late.

I have tried all types of machines from small clapped out to my Cincinnati which weighs 5000lbs. The quality of the miter you get with power feed and an extremely robust machine and fixture is hard to beat. I am not saying my set-up is better than others. Just saying what I have experienced and trying to explain the difference between set-ups.

Also just a note. Until you have mitered 953 you have not experienced what a hard material that snags is. Sub .6mm thick and rock hard. AerMet is a close 2nd with S3 not far behind. All three can annihilate a hole saw in one cut. Missing teeth and in the garbage before even finishing the miter.

[arregui]

I'm just guessing at 1200, by the way - I normally use the top speed on my drill, but not always at full throttle. I find I can feel if it's sawing nicely through or not, and vary speed and pressure as I go.

I guess what this shows is there's no right answer ;-)

claramente!!!!