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Two sided machining question

Posted: Sat Mar 28, 2015 8:29 pm
by SawdustandSmoke
Hello, I have watched a lot of tutorials on the two sided machining but still have a few questions.

I am hoping to do a good number of 3d models cut on two sides, Is it necessary for the dowel hole cuts in the material to be dead center?

I have two machines, one I would like to leave setup with the dowels in the table and use the other one to make the dowel holes one on each end.

Re: Two sided machining question

Posted: Sat Mar 28, 2015 8:37 pm
by CarveOne
If you want the front and back sides to be registered to each other - yes. There may be situations where it doesn't need to be absolutely perfect.

CarveOne

Re: Two sided machining question

Posted: Sat Mar 28, 2015 8:49 pm
by SawdustandSmoke
I was hoping you would say no :( I have a rotary axis most of the way setup, Do you think I would be better with it than the other method? I am making corbels and the edge faces away from the wall making any inconsistencies stand out.

I have previously machined them separately and glued them, but the shape lends itself very well to warping even in the more stable materials.

Re: Two sided machining question

Posted: Sat Mar 28, 2015 9:45 pm
by rscrawford
The dowel holes can be anywhere you want. You just need to drill the mirror image of the holes in the first side you are cutting, so when it is flipped the holes line up with the holes in the table. You can even cut the two sides on totally different areas of the table - just clamp the first side down and cut it (cutting the index holes with the first side cut) then drill the mirror image of the index holes in another part of the table and flip the piece and cut the second side. All the index holes do is ensure the piece is positioned where your machine thinks its positioned!

Re: Two sided machining question

Posted: Sat Mar 28, 2015 10:27 pm
by SawdustandSmoke
I found a generic picture, so anyways if I am understanding you correctly, If my dowell holes where are off center lets say 1/2 inch like the are in the photo the model would still be centered when flipped?

Re: Two sided machining question

Posted: Sat Mar 28, 2015 10:47 pm
by rscrawford
If you flip horizontally, then yes. Make sure they are an even distance from the centre of rotation. I personally like 4 holes. I never get good positioning with just two holes. Remember, any error in positioning will show up as double the error when cut, because the piece is flipped.

Re: Two sided machining question

Posted: Sat Mar 28, 2015 11:10 pm
by SawdustandSmoke
Thanks for the help, I believe I am over thinking it, oh well time to make some sawdust.

Re: Two sided machining question

Posted: Sun Mar 29, 2015 1:41 am
by dhellew2
Just another suggestion I have a few smaller table boards cut that are pinned to the main table. These small boards are then pinned to fit smaller projects, eliminating the need to make many holes in the main board. Pins align the board then I add a couple of hold-down clamps.

As already posted, you can put the pin holes anywhere you want but center alignment is the easiest and least likely to have errors. The secondary smaller tables eliminate the need for using specific holes in the main table.

For lithophanes I cut and leveled a small board leaving a ridge along one side which is used to align the bottom edge of the lithophanes. The head end has a pin the other two sides are clamped by pushing the Corian against the ridge and the pin.

Re: Two sided machining question

Posted: Sun Mar 29, 2015 7:40 am
by mtylerfl
Hi Dale,

I really like your lithophane board idea. Do you have any photos of that? I 'think' I followed your explanation, but thought a couple photos would help me (and maybe others) understand it better.

Re: Two sided machining question

Posted: Mon Mar 30, 2015 1:48 am
by antennasDIY
A question about drilling the dowel or pin holes , do you use a regular drill bit and just lower spindle speed to use an end mill to do it? I used an endmill but got a lot of burning. I now think though because it was a four flute, so I'll use a two from now on, but would still like to hear the best way to do the holes please.

Re: Two sided machining question

Posted: Mon Mar 30, 2015 8:08 am
by scottp55
Check out the .crv at the bottom. Works quite well for me.
http://forum.vectric.com/viewtopic.php? ... mp#p156811
scott

Re: Two sided machining question

Posted: Mon Mar 30, 2015 11:48 am
by Adrian
antennasDIY wrote:A question about drilling the dowel or pin holes , do you use a regular drill bit and just lower spindle speed to use an end mill to do it? I used an endmill but got a lot of burning. I now think though because it was a four flute, so I'll use a two from now on, but would still like to hear the best way to do the holes please.
I do most of my holes using a inside profile toolpath with the ramp option set to spiral.

Re: Two sided machining question

Posted: Mon Mar 30, 2015 12:55 pm
by rscrawford
I use a high quality carbide tipped brad point drill bit. I'm often drilling through 3.25" of material and with the brad point drill I can set my rpms at 5000 and do it in 2 passes (1.625" per peck). This gives a very snug fit for 3/8" dowels. End mills won't give as nice of a cut.
http://www.leevalley.com/en/wood/page.a ... ,180,42240

Re: Two sided machining question

Posted: Wed Apr 01, 2015 5:57 am
by dhellew2
I drill using brad point bits. They make smooth straight accurate holes and are available in just about every size. I use high speed steel bits from Lee Valley Tools.
Dale

Re: Two sided machining question

Posted: Wed Apr 01, 2015 6:15 am
by dhellew2
Michael,
This is my lithophane table.
lithophane table.jpg
The board I use to pin smaller boards to is removed because I was turning walking sticks today. The lithophane board is also used to align the other board, keeping everything straight without the need for any adjustments. For anything over 5' long Just go over the top of the lithophane table by raising the table with aluminum extrusions clamped to the aluminum rails.
Dale