How to.... and how much $$ to charge

[Mac Tech]

Hello all, hoping someone out there will help a newbie out....

Sorry for the long post, but I will try to give all the info needed.


Background info...
I have a benchtop CNC mill that I have been learning to use (Syil X4+). My father works maintenance for a company that dyes cloth. His has told his boss about me having the mill and he would like to toss a few odd jobs to me that they would normally send to a local machine shop. Nice.

They recently ordered new shafts for some equipment (4 of them). The shafts were not exactly what the needed and need to be modified. Also, they have some old longer shafts that they want me to try to cut to size and make more of the shafts like needs to be modified.

The shaft is as follows....
Pics below-
1" dia x 27.75" long
one end has a section milled half way through the shaft
one end has a keyway 4.25"L x .25"W x .13"D
not sure exactly what the steel is, but I don't think it'll be too tough to cut


The How To part..... 2 parts here (modifying existing and making new)
I would like to get suggestions on how to modify the new shafts that were bought as well as making shafts from the old stock....

OK. So when it comes to making new shafts from the old ones, it seem pretty straight forward.

- cut the stock to length
- set up in v-blocks and check that things are square and centered
- mill the one end down to half the shaft (.5")
- turn shaft around and setup again
- mill keyway



For the 4 that need modified... The mod is pretty simple. They keyway needs to be extended toward the end of the shaft.

My question here is what procedure would you use to accurately line up with the existing keyway to smoothly extended it?



The How Much $$ to Charge Part....

I'm not looking to make big money here, but these types of job will give me that much needed experience. I know that the cost of the 4 new shafts was around $45 each.

- How much would be reasonable to charge for extending the keyways on 4 shafts

- How much would be reasonable to make new shafts from old shafts they provide for stock? (again, the new ones were $45 ea.)


I know these things seem simplistic for others with more experince, so thanks for taking the time to answer.

[flick]

In order to extend the keyway smoothly:

1. Orient the shaft so the keyway is vertical by inserting a key, and using an accurate bubble level. Insert the key in all 4 orientations, and if they don't all agree, then level it to the orientation that's somewhere in the middle.

2. Program a toolpath that goes up one side, makes a semi-circle, and comes back down the other with an undersize endmill, leaving .005" on each side. Nibble it down in Z until the floor blends in.

3. Adjust your endmill geometry a half-thou at a time until the sides blend in. If both sides blend in simultaneously, congratulations, your touch off was perfect. If one side blends in first, just move your G54 towards the other side until it blends in too.

This is a lot more love than a simple keyway usually deserves, but it's the only way I've been able to extend one so it looks and functions perfectly. In my case it was well worth it for the large berylium copper part with a weeks worth of machine time in it. $$$.

What to charge? this is definitely more for the learning experience. You can't make a reasonable wage for this work, so just charge him half the cost of a new shaft. Good deal for him, and it pays for your cutters.

[Mac Tech]

Thanks flick,

I used a setup pretty close to your suggestion, worked great. I'm just starting out and really enjoy doing stuff like this just to learn something new.

I modified 3 shafts (extending the slot) and I may make a couple more if they bring me the stock. Pretty simple once I settled in on a working process, but it was time consuming.

For my efforts they bought me a pretty nice set of US made V-blocks that I needed to hold the shafts to do the work. The set has 4 v-blocks (2 each of 2 diff sizes). I believe they spent around $130 on them.

It may not be much, but it get me experience and may lead to more work in the future.

[M250cnc]

Mach Tech Flicks description is one way of doing the keyway but not the correct way.

The correct way would be to mount the shaft in a dividing head.

Then using a DTI make sure it is level and parallel to the table

Then again using a DTI or probe find the centre of the shaft

Then when you have found the shaft centre you rotate the dividing head to find the centre of the keyway

Then you are good to go

This is the sort of job that would be easier on a manual machine.

To blend the sides of the shaft you would use a cigarette paper between the existing keyway and the rotating cutter when the cutter starts to grab the paper you know you only have the paper thickness to go before you touch 0.001"

To 4 shafts would be about an hour

Phil

[flick]

First, after re-reading my post, I realized that we're all using the wrong terminology. It's a shaft, so we're dealing with a keyseat. Keyways go in bores.

Secondly, If the customer likes the result, and you got it done in a reasonable amount of time, it most certainly is correct.

Lastly, In the case of putting in a new keyseat, you most definitely do need to find the center of the shaft, but in the case of extending one, doing so assumes that the existing keyseat is centered perfectly. This is a bad assumption, as there are acceptable tolerances on the alignment of a keyseat, like all machined features. Using the method I describe above aligns the extension with the existing keyseat instead of the shaft. This results in a better blend, and therefore a better fit with the key.

[flick]

Thanks flick,

I used a setup pretty close to your suggestion, worked great. I'm just starting out and really enjoy doing stuff like this just to learn something new.

I modified 3 shafts (extending the slot) and I may make a couple more if they bring me the stock. Pretty simple once I settled in on a working process, but it was time consuming.

For my efforts they bought me a pretty nice set of US made V-blocks that I needed to hold the shafts to do the work. The set has 4 v-blocks (2 each of 2 diff sizes). I believe they spent around $130 on them.

It may not be much, but it get me experience and may lead to more work in the future.

That's awesome. Congratulations on completing your first paid work, it sounds like you made a nice arrangement.

[M250cnc]

Flick,

You should always do it the correct way, but we all like to cheat a bit.

So the correct way should be described and whoever is taking note of the instructions given can make there own mind up.

You quoted Lastly, In the case of putting in a new keyseat, you most definitely do need to find the center of the shaft

So if you were extending a slot you would assume that it had been done correctly in the first place so it would be in the middle.

If you wanted to be absolutely sure the slot was in the correct orientation by running the DTI across the face of the bottom of the slot.

You should never be using a level as this is nowhere accurate enough because for for a start the mill whatever may not be level.

No trained engineer would come up with the solution you provided, because a DTI is essential kit and i have 4 of various types.

Phil

[flick]

No trained engineer would come up with the solution you provided

Well, i guess my solution is the result of the fact that I'm a trained, professional machinist.

My level is good to a tenth over 3 inches. And it's a simple matter to check the level of the table, and then make sure the workpiece agrees with the table, rather than absolute level.

But you do it your way.

[MrWild]

Great googly moogly. Engineers, "professional machinists" Lord, it isn't hard at all. Put the shaft in a vise, tighten the vise snugly. Indicate front and back to find the center. Chuck up an endmill or better yet dowel pin the same size as the keyway, key seat, whatever, and loosen the vise enough you can rotate the shaft until the endmill or dowel enters the slot. It's now centered and in proper perspective. Much easier to do this on a manual mill. You could even be anal retentive and use an indicator to find true center of the keyway once you've found the shaft/vise center. It will be much slower than using a dowel, but not that much more precise.

In the shop I got my T&D card, there were as many different ways of doing something as there were Tool and Die Makers. The common saying was get different ways to do something and choose what works best for you. All the ways mentioned will work, all are proper, all have their Brass Bands claiming their way is the only way. Take them all with a grain of salt, sift, and pick the way that makes you feel comfortable.

[flick]

All the ways mentioned will work, all are proper

I totally agree. I got a bit distracted from that point, as it always puts a bug up my butt when someone tries to speak of methodology in absolutes: correct/incorrect, right/wrong, legitimate/illegitimate. It's old school thinking that stifles creativity, and punishes the imaginative.

I pointed out a potential shortcoming of the other method, which I think was a fair, constructive comment. I certainly didn't say it was wrong. In fact, I said:

If the customer likes the result, and you got it done in a reasonable amount of time, it most certainly is correct.

That should have been the main point of my previous post, and it pretty much sums up my philosophy about machining.

[tusavision]

Great googly moogly. Engineers, "professional machinists" Lord, it isn't hard at all. Put the shaft in a vise, tighten the vise snugly. Indicate front and back to find the center. Chuck up an endmill or better yet dowel pin the same size as the keyway, key seat, whatever, and loosen the vise enough you can rotate the shaft until the endmill or dowel enters the slot. It's now centered and in proper perspective. Much easier to do this on a manual mill. You could even be anal retentive and use an indicator to find true center of the keyway once you've found the shaft/vise center. It will be much slower than using a dowel, but not that much more precise.

In the shop I got my T&D card, there were as many different ways of doing something as there were Tool and Die Makers. The common saying was get different ways to do something and choose what works best for you. All the ways mentioned will work, all are proper, all have their Brass Bands claiming their way is the only way. Take them all with a grain of salt, sift, and pick the way that makes you feel comfortable.

Well said.

And Coming from someone who can rarely decide what he's most comfortable with: for me it's USUALLY worthwhile to follow through with whatever I decide to do vs. changing courses halfway through. Knowing a hurdle from a lost cause due to bad judgement when I see one is something I still haven't mastered.

If I can afford to: my preference is to make it in wax or plastic first until I like my methodology, and then commit my process to metal. That way: when the best laid plan goes astray: it costs me $1/pound. More importantly: helps get chips on the floor NOW, vs. doing a mental cost benefit anlysis on the merits of 5 different process for a one-off $10 part.

Then again: 10 minutes planning the right way to do it the first time is better than 2 hours of tearing down setups.

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