Up Spiral Bits

[PEU]

When I saw this link the other day: http://cncrouting.co.uk/ (Thanks Kobus) I don't need to explain again what I want to do when I finish my shop, I give that address and let the people know.

Time ago I started making patterns, and last tuesday I had an idea, why not make samples at scale of what I want to do, so today I started making dust with my small router.

I have one question regarding MDF, Im using a 1/4" 2 Flutes solid carbide end mill and the finish on the upper side needs to be sanded to be ok, I wonder if there are better ways to do what Im doing.

Here are some photos:

http://img138.imageshack.us/img138/1017/mdf01.jpg
http://img28.imageshack.us/img28/4882/mdf02.jpg

After Grit 40 sanding
http://img192.imageshack.us/img192/5267/mdf03.jpg

The bottom side was better but needed sanding too
http://img11.imageshack.us/img11/5734/mdf04.jpg

Ideas are welcome.

Thanks

[Johannescnc]

I have routed a lot of MDF and rarely have had results like that... when making cuts with my machine, I make incremental cuts until to keep it smooth. Looks like your using perhaps an upcut spiral?

[Johannescnc]

that desk is pretty impressive :rolleyes: http://cncrouting.co.uk/ thanks for sharing..

[PEU]

Im using this cutter:

http://img695.imageshack.us/img695/6517/mdf05.jpg

[Johannescnc]

I hate sanding! :mad: but that unfortunately comes with the job some times...
I have several sanders! makes it faster but still hate it..
try using a straight cuter.. ?? adjust feed ?? still the sanded results look good!

[rayditutto]

That looks like tear out . . . which would be explained by the spiral upcut bit pictured . . . as the cutting edge is leaving the wood it will tend to tear

a spiral downcut will cut in to the workpiece (rather than up and out) and the tear out that would happen on the bottom is mitigated by having a solid backing (the spoil board)

cheers,
robin

[KenC]

Robin, Do you mean using straight flute would have less or no such tearing effects?

[rayditutto]

Yes, a straight bit should have less (but possibly some) tear out

The cutting force is in the direction that the cutting edge is moving

Imagine cutting a slice of bread from the bottom up :eek: contrasted with cutting from the top down :)

A spiral down cut pushes down and in the direction of rotation - it also works with your clamps, not pulling against them

When i have used a spiral up cut and been too aggressive with either IPM or depth of cut i've had the work piece lift up off the table :o

I tend to favour 1/4" spiral downcut and keep the depth of each pass to not exceed the diameter of the bit - the subsequent passes will clean out the sawdust that the bit likes to compress into the cut

cheers,
robin

[KenC]

Thanks for the elaborate explanation. Now I learn something important.

[Johannescnc]

well put Robin... I would add that the results are not terrible and can be easily improved with a palm sander with 80 grit. And I think the softened edges would be good for what your doing. makes fitting the pieces together easier.
I hate to sand, hate to paint and stain but love the results and that's what we all want.. great results with the least amount of effort! :)

[PEU]

did a couple of new patterns (*) with a 4flute upcut mill and the results were similar, I did noticed the board wanted to go up, mostly when the cutter was near the center were clamping forces were weaker. I wonder if changing from conventional to climb cutting method would help here.

Downcut are more expensive that upcut endmills?


(*) I recall reading in another thread that posting stuff made with non mechmate routers was a no-no, I wonder how this applies here.

[Johannescnc]

this discussion is about cutters... maybe should be in a different area.. :confused:
http://www.mechmate.com/forums/forumdisplay.php?f=82

[PEU]

I agree, from post 136, all posts can be moved to a new thread. Mike?

[PEU]

Thanks Mike!

I have straight router bits, will check how they perform compared to the ones I used.

[normand blais]

If you use downcut bit for pocketing they are great .But if you use a 1/4 inch downcut to cut 1/4inch slot in 3/4 inch wood in 3 pass of 1/4 inch ,the chips are getting pack back in the slot 3 time and every time you are rechopping those chips into dust and repacking it and that heat up the cutter and it get dull faster. Flying chip remove heat ,heat deteriorate edge .
Normand

[KenC]

would dust collector help?

[normand blais]

I doubt it ,those chips are pack so tight in the slot even with air coming down from the router it does not remove them. Chips are so tight that even with a sharp object they are hard to remove.It is good to hold part not edge:)

[rayditutto]

Normand,
you are quite right :)
sometimes i forget there is a bigger picture to look at :o
(and always trade offs)

i've learned to keep my depth of cut <= to the bit diameter which seems to help the dust packing problem somewhat (on slots)


cheers,
robin

[PEU]

Found this browsing for downcut mills

Downcut tools are used where the downshearing effect of the tool is preferred. This tool will:

Produce a clean top edge cut of dado type or groove type cut or simple a thru-cut where the bottom edge cut quality is not important
Direct chip flow downward
Help hold part onto table or pods
When nest cutting the tool path remains packed with chips helping preserve maximum vacuum
Never plunge straight down with downcut tooling. This may cause fire or tool breakage.


Source: http://www.vortextool.com/index.cfm?fuseaction=category.display&category_id=14

[mikefoged]

Hi Pablo

take a look in post 50 in this thread.

http://www.mechmate.com/forums/showthread.php?t=1708&page=2

[Gerald D]

Pablo, we realised that: 1. up-cut spirals are the cheapest and longest lasting bits we can can get locally and 2. that only a little bit of sanding with an orbital sander is needed, therefore 90% of the mdf work is done with upcut spirals.

[PEU]

Hi Pablo

take a look in post 50 in this thread.

http://www.mechmate.com/forums/showthread.php?t=1708&page=2

your offset makes the endmill go inside the toolpath? or first path is a little away and the last one is were is supposed to be?

Gerald, thanks for your comment, when I need carbide endmills I buy them at USA, with shipping and local duties they end costing half local price, and 2 flutes carbide upcut 1/4 endmills are among the cheapest (http://www.advancedtool.com/) I wonder if some surface treatment is better than uncoated carbide for MDF or Plywood.

Thanks!

[lumberjack_jeff]

Pablo, which specific carbide endmill do you buy? 00220-200?

[PEU]

yup, also purchased ball end in 1/4 and 1/8" joined forces with a friend that uses a lot of endmills and we both saved on shipping. From previous purchases I have 1/4"4FL and 1/16" 2FL

http://img693.imageshack.us/img693/5306/img1034q.jpg

When I start using an endmill I put 2 black marks in its container to know which one is in use and which one is new.

I wonder if some of the coatings they offer is recommended for wood.

[ger21]

If you can cut them in one pass, use a compression spiral bit. You'll get clean edges top and bottom. Downside is that the bits are more expensive.

http://www.vortextool.com/index.cfm?fuseaction=category.display&category_id=29

http://www.vortextool.com/index.cfm?fuseaction=category.display&category_id=59