So much sanding after changing bits

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rosielee
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So much sanding after changing bits

Post by rosielee »

Hey

I'm a newbie (ish) to cnc and this forum so I hope I'm posting this in the right place!

I am using VCarve Pro. I'm doing a simple pocket tool path around some lettering on a 10 x 10" piece of pine. I'm using a large area clearance tool 1/4" bit and then a 1/8th inch bit for the detail.

I'm using a touch plate to zero my z axis each time.

The 1/4 does a great job, very clean. When the 1/8 goes round there is a indent line (not super deep but very noticeable) around every letter which will require a whole lot of sanding.

Is this something I should just accept? Or would you expect, given the touch plate and all, that the sanding would be minimal?

Jules

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Rcnewcomb
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Re: So much sanding after changing bits

Post by Rcnewcomb »

Wood moves when it is cut. If the relative humidity in the shop is higher than the moisture content in the wood then the piece absorbs water. If the shop is drier than the wood then moisture flow out of the wood.

You may get better results by using the smaller bit and then the larger bit.

A better holddown method such as vacuum may help.

Sometimes it is faster to do the whole piece with a single bit rather than spend time sanding.
- Randall Newcomb
10 fingers in, 10 fingers out, another good day in the shop

steve323
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Re: So much sanding after changing bits

Post by steve323 »

Maybe the 1/8" bit has a bit more flex than the 1/4" bit. Would the lines go away if you raised the 1/8" bit a very small amount? My touchplate it handheld. I move it manually to the location where I want to reference. A sheet of paper or a playing card under the base would result in a small offset in height.

Steve

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martin54
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Re: So much sanding after changing bits

Post by martin54 »

is it a fixed touch plate or one you place on top of the material? If it is the latter then are you placing it in exactly the same place & orientation after your bit change? Wood often isn't as flat as we think it is so even with a touch plate it is possible to get different z heights when changing bits :lol: :lol:

As Randall says changes in humidity can affect things as can tension within the wood that is released when a large amount is removed from one side. Have you experimented with different types of wood ?

rosielee
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Re: So much sanding after changing bits

Post by rosielee »

thank you for the replies!
I did the whole job with the 1/8th bit nudge a touch higher and the result was much better! I guess it's all about experimenting with different types of wood too.
Thank you

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Re: So much sanding after changing bits

Post by Heime »

Over on the Shopbot Forum they put up a good video on best practices for zeroing this week. It dealt exactly with your problem. Well worth a look.

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scottp55
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Re: So much sanding after changing bits

Post by scottp55 »

Here's yesterday's tutorial on Zeroing multiple bits;
https://www.youtube.com/watch?v=0sOTwmW ... e=youtu.be
scott
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Adrian
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Re: So much sanding after changing bits

Post by Adrian »

I thought that was everybody who zeroed to the material surface did anyway? :? Still doesn't account for the cut area expanding or the different vertical "pull" of the tools etc. Not a lot you can do to get around that though.

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scottp55
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Re: So much sanding after changing bits

Post by scottp55 »

Agree Adrian.
Doesn't take into account a lot of things.
Just posted for the OP for basics.
scott
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rosielee
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Re: So much sanding after changing bits

Post by rosielee »

Thank you, that was actually very helpful :lol:

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