# Engraving /Micromachining tool holding advice needed.



## Flynth (Jan 28, 2021)

I recently acquired a desktop cnc machine and I was both amazed by its positioning accuracy and disappointed with its spindle runout. I'm interested in using it for micromachining of soft materials (brass, aluminium, copper on pcb's) and engraving. Unfortunately the "spindle" is simply a dc motor with a 5mm output shaft and a 5mm to er11 coupler. By careful manipulation it is possible to lower few thou of runout to few tenths (0.015mm) in the er taper, but then the collet settles into up to few thou of runout after few minutes of work. 

So I decided to do some experimentation. First I made a tiny boring bar and a holder for it (pictured) 
	

		
			
		

		
	






Then I turned the OD of 9mm brass stock to 8mm and polished it to make holding it repeatable. I ended up with a taper under 4 tenths (0.01mm). I then used a Morse 3 collet (runout around one tenth) in my mini lathe and bored very precisely 5mm in one end and 1/8th (3.175) in the other for a fairly tight (manual) push fit. 

You can imagine my surprise when I measured 4 tenths(0.1mm) of runout. Still not as good as planned. 

So instead I bored out the 5mm hole and the screw to hold the shaft without preparing the OD and I chucked the whole motor with my "adapter" installed into my big lathe chuck. Then I used a bench psu to power the motor and bored the hole in tiny increments like that. (I attempted boring directly on the cnc before, but it wasn't rigid enough). 

II ended up with one good one roughly acceptable holders. The 1/8th has under a tenth of runout (0.01mm) 10mm from the holder and 4mm holder has about 3 times that.


At last I have a usable 1/8th holder for pcb milling etc. 



So I'll probably have to remake the 4mm holder. 

I'm wondering if there is a way to make one without having to use the motor to do the turning. I imagine my initial failure was because the 5mm hole isn't adequately concentric. Then if I use the spindle itself for boring that compensates for it (the screw ensuring same position each time). Perhaps using an expandable lap and lapping it would be the solution? What do you think? 

I can make a tiny expandable lap from aluminium, but I thought to ask first if anyone can comment from experience on what precision I can expect from a two part expandable lap. 

I'have some ideas for how to make such a tiny lap, but all involve custom d bits etc. So before I spend days on it I decided to ask here if anyone has any advice to offer or links to any content about such tiny diy laps etc. Buying one unfortunately is uneconomical, because the only manufacturer I'm aware of is in US, and shipping alone would make it not worth it. However if there is a manufacturer of such tiny laps in Eu I would also be very keen to find that out. 

Also, I'm considering making a complete miniature spindle with belt drive RC motor for that cnc. This is a different project however and I have to wait for parts to arrive from China before I can start. So I'm trying to improve what I have first. 

On a side note, it is amazing that shipping small parts from China can be so cheap while equivalent distance the other way - US is at least two orders of magnitude more expensive. 8


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## Steve-F (Jan 28, 2021)

I might have a small spindle, ....will have to look.


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## Lo-Fi (Jan 28, 2021)

You're unlikely to get great results with the bearings in that cheap DC motor, which is probably the limiting factor. If you want something accurate and smooth running, it's not hard to construct a tiny spindle with a couple of magneto bearings and belt drive. Or really go for it and run a straight shank ER collet holder in graphite air bearings. You can buy the holder commercially and blocks of graphite are cheap and easy enough to get hold of.






For what it's worth: The Chinese gov essentially subsidizes export shipping, making Chinese stuff even more competitive...


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## Flynth (Jan 28, 2021)

Lo-Fi said:


> You're unlikely to get great results with the bearings in that cheap DC motor, which is probably the limiting factor. If you want something accurate and smooth running, it's not hard to construct a tiny spindle with a couple of magneto bearings and belt drive. Or really go for it and run a straight shank ER collet holder in graphite air bearings. You can buy the holder commercially and blocks of graphite are cheap and easy enough to get hold of.


Building one is in my plans. I already sourced standard roller bearings that appear to be good enough, but I have to wait probably about a month for the straight shank ER adapter. So what I'm doing with this motor is just temporary. Still, I'm trying to make the best of it.



Steve-F said:


> I might have a small spindle, ....will have to look.


Thanks. I'm definitely interested how it is constructed. If you can take some photos and perhaps measure runout that would be great.

I see belt-drive mini spindles occasionally in online videos, but I haven't seen one where runout numbers, max speed etc would be mentioned as well as construction details.


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## Lo-Fi (Jan 28, 2021)

It's a cool project! 

The trick with home build spindles seems to be to machine the critical parts to final dimension in their own bearings, then treat is as a non serviceable cartridge that cannot be disassembled. I'm building a Quorn tool and cutter grinder which uses a couple of magneto bearings and gets finish machined after final assembly. Tricky with a commercial ER holder, but if your bearings are decent you should get good results.


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## Braeden P (Jan 28, 2021)

i have a little 30 18 mini ¨mill¨ to much flex going to upgrade the whole entire spindle with new rails and bearings


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## Steve-F (Jan 28, 2021)

Flynth, found it......here is picture of what I have. Adjustable depth control with a 3/16" collet and Excellent bearings!


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## macardoso (Jan 28, 2021)

Get that from Steve!

You need a proper spindle - runout kills tiny tools.


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## Braeden P (Jan 28, 2021)

macardoso said:


> Get that from Steve!
> 
> You need a proper spindle - runout kills tiny tools.


yup alum eats the vee bits alive i might know from practice


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## Flynth (Jan 28, 2021)

Steve-F said:


> Flynth, found it......here is picture of what I have. Adjustable depth control with a 3/16" collet and Excellent bearings!


This is nice. If we weren't located half a world away I would be interested in buying it off you (if you didn't need it)  

As an example what difference a thou of runout makes I took two microscope pictures of test pcbs milled. Those were done with 10 degree 0.1mm v bit (2.5thou ),10k rpm, 130mm/min (5.1in/min) feed, 0.04 doc (1 thou) 2 passes so total depth 0.08mm (2 thou). I estimate the width of the cut is 0.11mm (around 2.5 thou) on the first picture and 0.15mm (3.5 thou) on the second. It is not a huge difference, but I think it will affect the tool life quite a bit. 







BTW, this on on 3018cnc "Pro" version using the same g code. The only difference is the height map. As the pcb is not flat and it is glued to a piece of mdf it wouldn't be possible without a height map. 



Braeden P said:


> i have a little 30 18 mini ¨mill¨ to much flex going to upgrade the whole entire spindle with new rails and bearings



I always considered 3018 an engraver rather than a "mill" (even in quote marks ;-) I assume we have the same device. I have the so called Pro version that uses thick bakelite as y supports rather than aluminium extrusions. I think they are OK. They feel very stiff in hand. I'm not expecting miracles from it, but with some upgrades it should be possible to cut aluminium with tiny cutters at high speed and shallow doc. My main issue with it so far was the runout and the flexibility of the spindle mount. Imbalance caused by motor's shaft cutout is enough to cause vibration in the mount... I think it is because they saved money by designing large empty cavities in the plastic. If it was a solid block of plastic it would be much better. I'm considering 3d printing a new z mount from abs with close to 100% infill. That should be much more solid. Of course aluminium would be better. 

Here is a photo of the above pcb being cut. 



Coming back to the original subject  



Lo-Fi said:


> It's a cool project!
> 
> The trick with home build spindles seems to be to machine the critical parts to final dimension in their own bearings, then treat is as a non serviceable cartridge that cannot be disassembled. I'm building a Quorn tool and cutter grinder which uses a couple of magneto bearings and gets finish machined after final assembly. Tricky with a commercial ER holder, but if your bearings are decent you should get good results.


Yes, definitely. With the ER holder I hope it will fit the bearings nicely and I'll be able to "dust grind" the taper to make it true once it is assembled. 

Having to wait for that adapter a long time I may end up making my own equivalent before it arrives...

Also, why magneto bearings? Did you just happen to have them, or are they in some way better for a spindle?


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## Braeden P (Jan 28, 2021)

Flynth said:


> This is nice. If we weren't located half a world away I would be interested in buying it off you (if you didn't need it)
> 
> As an example what difference a thou of runout makes I took two microscope pictures of test pcbs milled. Those were done with 10 degree 0.1mm v bit (2.5thou ),10k rpm, 130mm/min (5.1in/min) feed, 0.04 doc (1 thou) 2 passes so total depth 0.08mm (2 thou). I estimate the width of the cut is 0.11mm (around 2.5 thou) on the first picture and 0.15mm (3.5 thou) on the second. It is not a huge difference, but I think it will affect the tool life quite a bit.
> View attachment 352962
> ...


same as mine, mine is the big one it was about $220 of amazon with collets and some bits but i got it hooked up ready to go using easal from inventables i had it ready to go and it said turn on spindle so i did i went back and it could not find the machine and i cant get it connected to it and i dont know how and i cant figure it out  and yes all of the cables are connected maybe should not have bought the cheapest one


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## Steve-F (Jan 28, 2021)

Flynth, no, I don't need it, I have 3 more just like it and enough projects to choke a horse right now. The unit weighs about 912 grams as it sits. No idea what shipping something like it would cost?


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## Braeden P (Jan 28, 2021)

Steve-F said:


> Flynth, no, I don't need it, I have 3 more just like it and enough projects to choke a horse right now. The unit weighs about 912 grams as it sits. No idea what shipping something like it would cost?


i would be interested where you got them i am trying to upgrade mine to


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## Steve-F (Jan 28, 2021)

We have engravers at work and they upgraded to digital motors and spindles, making the old ones non compatible any more. They were offered to me then:<)


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## Braeden P (Jan 28, 2021)

Steve-F said:


> We have engravers at work and they upgraded to digital motors and spindles, making the old ones non compatible any more. They were offered to me then:<)


could i buy one from you?


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## Steve-F (Jan 28, 2021)

Sure Braeden, I don't know what to ask for one? At least you are "local" so shipping should be reasonable :<)


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## Braeden P (Jan 28, 2021)

Steve-F said:


> Sure Braeden, I don't know what to ask for one? At least you are "local" so shipping should be reasonable :<)


could you put it on ebay?


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## Lo-Fi (Jan 28, 2021)

I think because they lend themselves to the task fairly well with the races being removable from the cages and being fairly close tolerance for not a lot of money, but nothing more than that. Any decent bearings will probably do!

I tried grinding my Bridgeport spindle after replacing the bearings, but found I couldn't get it as true as hard turning did. Your mileage may vary!


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## Steve-F (Jan 28, 2021)

I have never sold on Ebay, only purchased and I don't have the time to monitor transactions. Are you a seller?


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## Braeden P (Jan 28, 2021)

Steve-F said:


> I have never sold on Ebay, only purchased and I don't have the time to monitor transactions. Are you a seller?


nope i am 12 so i ask my dad when i want something and pay him


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## Steve-F (Jan 28, 2021)

Braeden, I only have 53 years on you:<) I'm sending you a PM


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## macardoso (Jan 28, 2021)

Ebay will take 10% cut. Have your dad pay with PayPal and have Steve ship to you. No biggie - Steve seems like a nice guy


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## Braeden P (Jan 28, 2021)

macardoso said:


> Ebay will take 10% cut. Have your dad pay with PayPal and have Steve ship to you. No biggie - Steve seems like a nice guy


not allowed to get stuff from this site


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## davidpbest (Jan 28, 2021)

Braeden P said:


> nope i am 12 so i ask my dad when i want something and pay him


Hahaha


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## Rex Walters (Jan 28, 2021)

Lo-Fi said:


> I'm building a Quorn tool and cutter grinder which uses a couple of magneto bearings



Not to hijack the thread, but I'm also building a Quorn. Only a complete idiot™ would orient the wheel-side bearing as shown incorrectly in older versions of the Hemingway drawings. I'm, uh, told that it really doesn't work well that way, no matter how careful you are with the machining.

Just in case you're also making one per the Hemingway drawings, the correct orientation is with the open sides of the bearings facing the end caps at both ends.


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## Lo-Fi (Jan 28, 2021)

Wow, that's quite a drawing fail! Thanks for the heads up, I've actually been working from the original book as I stumbled across some super cheap castings on eBay a while back.


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## Rex Walters (Jan 28, 2021)

Nah, it’s actually an very small and easy mistake to make in the top level assembly view. I should have caught it if only I’d thought a little harder about how it must work.

I’m think Prof. Chaddick’s original also used magneto bearings and a spring-box design. Just remember the open sides face outwards.


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## Flynth (Jan 28, 2021)

Steve-F said:


> Flynth, no, I don't need it, I have 3 more just like it and enough projects to choke a horse right now. The unit weighs about 912 grams as it sits. No idea what shipping something like it would cost?


If it could fit into a usps small size box (8-5/8" x 5-3/8" x 1-5/8") it would be around $40 (slightly less or more) to ship using Priority Mail International (flat rate). Probably if I found one like that on ebay I would bid up to $35 as well if it was possible to measure runout in advance and it was around 2 tenths or less. If it wasn't possible to measure runout I woul probably bit $20 on it. Please don't be offended if this is way too low  One of US members could probably offer more as shipping would be a lot less.

If you are interested please pm me. We could use paypal etc. If it doesn't fit into small box next size up costs 80$ and is 13-5/8" x 11-7/8" x 3-3/8" or 11" x 8-1/2" x 5-1/2". That is a bit too much IMO.




Braeden P said:


> same as mine, mine is the big one it was about $220 of amazon with collets and some bits but i got it hooked up ready to go using easal from inventables i had it ready to go and it said turn on spindle so i did i went back and it could not find the machine and i cant get it connected to it and i dont know how and i cant figure it out  and yes all of the cables are connected maybe should not have bought the cheapest one



Braeden, if you would like to give it another go pm me or start a new thread (maybe in questions and answers section). It shouldn't be difficult. I haven't used easel. I use software called candle. It is very simple software that is used to control the mill manually, load a g code program etc. If you could at least get it working in candle I think easel is likely to work if you're currently having a driver or connectivity problem.

Candle should be on the usb stick that came with the machine or you can download it from here https://github.com/Denvi/Candle/releases It is probably better to use one from the usb stick as it should match the machine's software version. If you need help lets take this to a new thread or pm. Please bear in mind I'm in a different timezone so my replies will come late/early for you


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## Braeden P (Jan 28, 2021)

Flynth said:


> If it could fit into a usps small size box (8-5/8" x 5-3/8" x 1-5/8") it would be around $40 (slightly less or more) to ship using Priority Mail International (flat rate). Probably if I found one like that on ebay I would bid up to $35 as well if it was possible to measure runout in advance and it was around 2 tenths or less. If it wasn't possible to measure runout I woul probably bit $20 on it. Please don't be offended if this is way too low  One of US members could probably offer more as shipping would be a lot less.
> 
> If you are interested please pm me. We could use paypal etc. If it doesn't fit into small box next size up costs 80$ and is 13-5/8" x 11-7/8" x 3-3/8" or 11" x 8-1/2" x 5-1/2". That is a bit too much IMO.
> 
> ...


Works fine in candle but not easel so I will make a new thread


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## Flynth (Jan 29, 2021)

Braeden P said:


> Works fine in candle but not easel so I will make a new thread


Unfortunately I don't know anything about easel, but perhaps others do.


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## Flynth (Feb 1, 2021)

Look what arrived today from China much sooner than expected  



I should be able to turn this into a pretty good spindle I think.


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