Milling Aluminum Long Board truck

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MarkVa1
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Joined: Mon Aug 04, 2014 12:56 pm

Milling Aluminum Long Board truck

Post by MarkVa1 » Sat Dec 12, 2020 1:49 pm

Looking for opinions / thoughts for milling some long board trucks for an electric skateboard. Trying to use the experience to get my teenage son into machining and such.

I have yet to do any aluminum milling with my KRMX02, but have watched the videos on the the Kronos website. Looks like 2 flute carbon end mills can do the trick. I'll need to make some type of jig to hold / rotate the piece for the various angles. Plan to mill the motor mounts and maybe even the 36 teeth pulleys. I think 6061 aluminum should be strong enough.

Just wondering if anyone has done something similar with their KRMX02 and can share some pointers.

Thanks,

Mark.

baysale976
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Re: Milling Aluminum Long Board truck

Post by baysale976 » Sun Dec 13, 2020 2:53 pm

I don't have much to share, except about work holding: There is a lot more force than you think.
Make sure it is held very solidly.

msimpson
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Re: Milling Aluminum Long Board truck

Post by msimpson » Sun Dec 13, 2020 4:56 pm

Yep, it all starts with holding your stock as secure as possible. If thats not good, nothing else matters.

I see a machinists vice in your future.

MarkVa1
Posts: 164
Joined: Mon Aug 04, 2014 12:56 pm

Re: Milling Aluminum Long Board truck

Post by MarkVa1 » Mon Dec 14, 2020 12:02 am

:D I was thinking about that! I’m surprised how low $ the aluminum flat bar costs. I will probably buy some larger pieces and use some symmetrical holes to secure it to the table and allow for milling both sides ... probably going to be large learning curve on this one :D

msimpson
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Re: Milling Aluminum Long Board truck

Post by msimpson » Wed Dec 16, 2020 7:11 pm

I would recommend looking at all my working with aluminum videos and web pages.

Here some information on the vises that I use. Not real expensive.

viewtopic.php?f=41&t=2040&p=10504

I have two of the 2" machinists vises and they handle pretty much most of my aluminum chores.

MarkVa1
Posts: 164
Joined: Mon Aug 04, 2014 12:56 pm

Re: Milling Aluminum Long Board truck

Post by MarkVa1 » Thu Dec 17, 2020 5:07 pm

Thanks Michael - surprisingly inexpensive. I read a little about the use / importance of parallels so I ordered the one with the parallels. Should hold everything I need as a 3" piece is my widest stock. Looked into the Kurt vises but a little pricey for what I need.

Design is almost done. Waiting on the bushings to arrive as getting true dimensions is hard online, and I need my pivot to precisely fit...

I'd like to mill the pulleys myself but the tooth spacing is a radius is 10mm deep and the radius is less than any bit I have that can cut that deep. Only way I've seen it done is sideways on a lathe with a flywheel tool. And I don't have a lathe... Otherwise I think I can make the trucks, brackets and braces...

Mark.
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baysale976
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Re: Milling Aluminum Long Board truck

Post by baysale976 » Sun Dec 20, 2020 11:29 am

Our HS Robotics team makes these pulleys by drilling (with the CNC) the correct diameter holes first, then machining at the right diameter to expose the needed tooth pattern. They tried doing it after cutting out the diameter, but the drill was not rigid enough to drill half a hole.

msimpson
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Re: Milling Aluminum Long Board truck

Post by msimpson » Sun Dec 20, 2020 4:34 pm

If you are not going too deep, I have found using an end-mill smaller than the diameter and milling them using ramps. Do them about .003 shy of the diameter. Then do a single full pass at proper diameter.

Add this method and a harmonic drive and some sort of collet holding system and you could make all kinds of gears very accurately.

MarkVa1
Posts: 164
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Re: Milling Aluminum Long Board truck

Post by MarkVa1 » Mon Dec 21, 2020 1:48 pm

From what I've researched, a 40 Tooth pulley is about 64 to 65 mm in diameter. The resulting drill holes for the teeth are about 1.3 to 1.5mm in diameter. I'm looking to hold a 15 mm belt, so the depth might be 16 mm.

I'm not sure where to find that type of bit with such a small diameter but enough cutting depth to bore down 16 mm? Drilling the holes first makes sense. I'm not in a hurry so I can take the milling slow, but most of the bits I've seen this small have a very short cutting depth.

Thanks

Mark.

baysale976
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Re: Milling Aluminum Long Board truck

Post by baysale976 » Tue Dec 22, 2020 2:22 pm

Here is one example of such a drill bit. https://www.mcmaster.com/29355A19/ The difficulty will be getting a collet to hold it. I am not recommending this set, but it is but one example that contains a suitable collet for 1.5 mm drill bits. https://amzn.to/2M1UUVJ

An option is a carbide bit like https://www.precisebits.com/products/ca ... &filter=12, which has a 1/8" shaft, but only a 10 mm depth of cut.

Perhaps you could just mark the holes with a CNC (drill to 0.030 depth with an 1/8" bit) and complete them in the drill press. But you will need robust and repeatable workholding to ensure the pulley remains concentric.

MarkVa1
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Re: Milling Aluminum Long Board truck

Post by MarkVa1 » Tue Dec 22, 2020 2:41 pm

baysale976 wrote:
Tue Dec 22, 2020 2:22 pm
Here is one example of such a drill bit. https://www.mcmaster.com/29355A19/ The difficulty will be getting a collet to hold it. I am not recommending this set, but it is but one example that contains a suitable collet for 1.5 mm drill bits. https://amzn.to/2M1UUVJ

An option is a carbide bit like https://www.precisebits.com/products/ca ... &filter=12, which has a 1/8" shaft, but only a 10 mm depth of cut.

Perhaps you could just mark the holes with a CNC (drill to 0.030 depth with an 1/8" bit) and complete them in the drill press. But you will need robust and repeatable workholding to ensure the pulley remains concentric.
Thanks - now all the discussions I've read about precision collets makes sense... :)

I may give the McMaster Carr bit (or something similar) and precision collet a try. Worse case scenario - it doesn't work and I buy the pulleys... but trying to use my KRMX02 to do it is the fun part!

MarkVa1
Posts: 164
Joined: Mon Aug 04, 2014 12:56 pm

Re: Milling Aluminum Long Board truck

Post by MarkVa1 » Wed Jan 13, 2021 5:39 pm

"The difficulty will be getting a collet bit to hold it..."

I ordered some ER20 collets for my Bosch 1617 but they don't fit. I thought I read online that the 1617 uses ER20 collets. After it didn't fit, I searched some more and read that no US router products use ER Collets? If I go the Precise Bits route, they are specifically made for the router and not actually ER20 standard sizes...

It's all a bit confusing and annoying... everyone doing the same thing slightly differently is ridiculous :D

Is Precise Bits the only way to go for smaller collet sizes on a Bosch 1617? They are Imperial and not metric... I was planning to mill with some 2mm and 3mm end mills, but at this point I'm not sure how to find a collet chuck nut to hold the right collets.... :shock:

baysale976
Posts: 462
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Re: Milling Aluminum Long Board truck

Post by baysale976 » Thu Jan 14, 2021 10:43 am

MarkVa1 wrote:
Wed Jan 13, 2021 5:39 pm
everyone doing the same thing slightly differently is ridiculous
Yep, kinda like different cars using different lug bolt patterns. Everyone thinks they have the best solution.

Ideas:
1. Google "collet for bosch 1617 router" and check out the results. Elaire Corp has a good selection. They say they are R24.
2. Someone on YouTube converted their EVS1617 to ER20. It is under 7 minutes long, watch it.
3. It is possible to make your own collets. You do need a horizontal mill and metal lathe and considerable skill, but it is not impossible. Then the center hole can be any size you like, to hold anything.
(In the machining industry, a 'blank collet' is something you keep in stock, to bore it out to hold some odd size workpiece or tool. They are not expensive and, most importantly, not hardened so they can be machined. But the Bosch is not a 'standard' collet (like ER20) so you'll never find a blank collet AFAIK.)

As I wrote, the collet to hold the tool is the hardest part.

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