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delrin vs aluminum

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carlsoar

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#1
Hi All,

is there any real reason to make a stepper motor mount for a CNC conversion out of aluminum vs delrin?

I broke a tap in my aluminum Y axis motor mount, although the mount is fine to use still (hole for an endstop), I would like the placement there, and I have a block of delrin that could be milled to fit.

Thanks
 

woodchucker

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#2
So delrin is more flexible, soooo, will your mount flex at all. If not your probably good.
I would rather do it in al. So why did the tap break? did you use the correct drill bit? Did you use enough cutting fluid (tapmagic for al is what I use) ?
 

carlsoar

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#3
Thanks for the reply- the other reason for waiting to do delrin was finding a place to anodize the aluminum once cut. The one I would be replacing was. It's the y axis block from CNC fusion for an LMS 3900.

I think I broke it from a combination of not enough cutting fluid and not backing out enough to break up chips. Haven't done much tapping before, and mistakenly thought I could push through a bit of resistance buildup. Lesson learned on that one.
 

chips&more

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#4
Welcome and sorry, but not enough info and pics, this will only get you random answers.
 

Tony Wells

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#6
Delrin is not a substitute for aluminum in any structural part IMO. I would never use it for mounting a motor.
 

ch2co

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#7
Aluminum! Take it easy on the taps and use quality taps not really really expensive ones but not bargain basement ones.
What size tap were you using? I've done very little machining up until a couple years ago, but have been drilling and tapping holes
since I was a kid. Used to break them fairly often. Time will teach you the correct way to almost effortless tapping. I have probably
tapped 3-400 holes in the last year, mostly in aluminum in sizes from 2 - 56 to 1/2 - 18 and not broken one. Practice (and patience)
will guide you. There are some YouTube tutorials on tapping that are worthwhile watching. Good luck.

Welcome to the group! You have found a treasure chest of machining (and a few other things) knowledge.
Oh, and we like pictures of what members are doing. Lots of pictures.

CHuck the grumpy old guy
 

benmychree

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#8
If the tap did not shatter in the hole, chances are that it could be removed with a Walton tap extractor; its fingers enter the flutes in the tap and a tap wrench is used to back it out; some back and forth movement of the tap may be necessary to dislodge chips and burrs, but they usually do the job. If it is a through hole, the tap can be forced out its entering end with a punch and hammer and the hole can be repaired with a STI thread insert (HeliCoil)
 

tq60

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#9
What size tap?

If you have not much experience tapping then the cheapest harbor freight set may be good investment. ..

We had one that the taps were not near as hard as others. .Our craftsman set is similar in that the tool steel not being as hard does not cut as well but they are not near as brittle.

Better for hand tapping or chasing threads as less likely to snap.

After you get proper feel for it then use the good stuff.

Sent from my SAMSUNG-SGH-I337Z using Tapatalk
 

JPigg55

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#10
I've never tried this, but when I had a similar situation, a friend of mine told me to chill to tap with liquid nitrogen or canned air. Then use a punch to smack it, it should shatter and the pieces can be removed. In my situation, I didn't have either on hand and it was easier to make a new piece.
 

rwm

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#11
Nitric acid. Dissolves the tap but not aluminum. Order on ebay.
Robert
 

Wreck™Wreck

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#12
Why anodize a hobby machine part?
 

rwm

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#14
Because over time it will react with any steel part it is touching and "rust" to it
Especially if it gets wet. I just tried to get an aluminum and stainless roof rack apart after years of use. I had to cut it apart. Perhaps consider anti seize compound?
Robert
 

Metal

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#15
Especially if it gets wet. I just tried to get an aluminum and stainless roof rack apart after years of use. I had to cut it apart. Perhaps consider anti seize compound?
Robert
Apparently, machinist people that make their own sub plates use plain old KY jelly, and they have to take it apart and clean/reapply every few years but it keeps the two metals from reacting.
 

ch2co

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#16
Some of us just live in dry places ;)
 

Metal

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#19
[QUOTE="rwm,
"Regardless, environmental conditions remain large determinants of corrosion rates."
[/QUOTE]

Not that it doesn't happen if it is dry, it just happens slower
 

Reddinr

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#20
Delrin seems soft for a motor mount but it depends on your specific set-up. I've painted aluminum with pretty good luck with no corrosion with steel in a wet climate even. For next time tapping in aluminum, maybe try roll-form taps. I've had really good luck with them for smaller holes. They mash the aluminum into threads instead of cutting the metal. I'm sure someone on this site told me about them a while back. I use some aluminum tapping oil (green can) I got at a building supply store years ago that works well. Once I started with roll-forming taps on Al, I've only broken one 4-40 tap in hundreds of 4-40 - 1/4-20 tapped holes. I broke "many" of the regular cutting taps in Al. Be advised though that drill hole sizes need to be a bit different for those taps.
 

sabb0

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#21
Especially if it gets wet. I just tried to get an aluminum and stainless roof rack apart after years of use. I had to cut it apart. Perhaps consider anti seize compound?
Robert
Yes when i used to build ally ships we used to smear durolac between the aluminum hull and any stainless fittings coming into contact.

Sent from my SM-G920I using Tapatalk
 

Tim9

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#22
Just to add that most of the times when I broke a tap it was because I most likely was not holding the tap perfectly straight and level while turning the tap. In other words, I was not just turning the tap but also putting too much side forces on the tap while turning the tap.
That is why these work very well.

http://www.grizzly.com/products/Hand-Tapping-Machine/G8748?utm_campaign=zPage&utm_source=grizzly.com

But...if you want to save some money, here is a good YouTube Video by Tinker John.

His ingenious design uses a Briggs & Stratton connecting rod. I built one similar to his but I have since modified my build by just using 3/8"-drive tap drive sockets and I use a 3/8" long extension which tightly fits through the connecting rod. No drill chuck and an easier build. It works great and I haven't broken a tap since using this fixture.

Hanson® 2 Piece Adjustable Tap Socket Kit https://www.amazon.com/Hanson-3095001-2-Piece-Adjustable-Socket/dp/B000TGM7HY
 
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magicniner

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#23
You can massively reduce your chances of breaking taps by using a drill which gives less than a 100% thread.
 

Tim9

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#24
You can massively reduce your chances of breaking taps by using a drill which gives less than a 100% thread.
I totally agree Magicniner. I'm only pointing out that on those little taps...the few times I broke them I really did not have much resistance turning the tap. In fact, it seemed to be going in rather easy and then all of a sudden it snapped. And I remember that I had carelesly allowed the turning force to move sideways.
I'm pretty sure that since they are so brittle that the side forces increase the possibility of snapping them. That's why drill presses, mills or even a tapping fixtures are much less likely tox break a tap.
 

7milesup

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#25
One of the epiphanies I recently had was tapping aluminum with two flute taps. I always used the "standard" 3 flute tap until coming across a bunch of two flute taps. After using two flute taps, the difference between the 3 flute and 2 flute was astounding. Maybe all you guys knew that already but it was quite an eye opener for me.
 

benmychree

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#26
Two flute taps are wonderful, but should not be used for hand tapping, that is without a fixture or machine spindle to guide the tap; they have little .lateral strength and will snap off easily with small amount lateral force.
 

magicniner

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#27
I totally agree Magicniner. I'm only pointing out that on those little taps...the few times I broke them I really did not have much resistance turning the tap. In fact, it seemed to be going in rather easy and then all of a sudden it snapped. And I remember that I had carelesly allowed the turning force to move sideways.
I'm pretty sure that since they are so brittle that the side forces increase the possibility of snapping them. That's why drill presses, mills or even a tapping fixtures are much less likely tox break a tap.
I totally agree Tim9, I was only adding information not already in the thread without quoting or commenting on any content already there.
 
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