a interesting project and is there a better material?

[knight_toolworks]

I got a job from a local glass making company. they needed molds make for glass blowing. The fun part is the wood they use soaking wet cherry. they saw off a chunk of log and bought it to me in a plastic bag. I did a couple of test cuts in mdf to see what step-over I needed. I ended up doing it with 4% step-over and a 1/4" ballnose bit.
The fellow who was doing it before me could not do them in time. I guess hes had a shop sabre and would start it up and go home. a bit scary but in wet wood I doubt you could start a fire. His machine must have been pretty slow these took a little over a hour and that was using the same 1/4" bit to do the roughing pass and cutting at 4ips.
I guess they can also be made from graphite but the company had trouble finding small enough pieces to do it.
So I was wondering has anyone else found anything else that would work? I used my typical 1/2" 2" long downcut bit to cut these out and that sure did not work. the sawdust really packed in there and caused chattering so I guess I will need a upcut for these. it's nice to cut wood without using the dc. I wonder with the wet wood if it keeps the bit cooler they will last longer?
http://i154.photobucket.com/albums/s266/knighttoolworks/photo-9.jpg

[bleeth]

Steve:

I would use a different bit for roughing. Something like a Vortex upcut roughing or possibly even a chipbreaker. These puppies are made for hogging out hardwood and you should be able to push them as fast as your Chassis will take. They also have a real go to blazes upcut ball nose.
Downside is you are going to flip when you see the price! Upside will be cut speed and tool life.

[steelhead]

Dave is right on using two bits. However I can understand you wanting to use 1 bit so you don't have to change tools.

I don't believe your problem is material, rather your bit. Cherry machines well. The key word is "up cut". From the picture it looks like you could also use a larger diameter bit. Can you? A good rule of thumb is always use the largest diameter possible. Down cut bits have there place as well as up cut. Your situation calls for up cut. Also keep in mind that cherry burns at a low temperate.

My set up would be this if I did not want to change tools.


.375" ball nose, .25" depth with 33% step over. Feed rate 5.5" per second. .05" leave allowance. Finishing pass: 4" per second, .01" step over.

Hope this helps.

[steelhead]

Steve:

I would use a different bit for roughing. Something like a Vortex upcut roughing or possibly even a chipbreaker. These puppies are made for hogging out hardwood and you should be able to push them as fast as your Chassis will take. They also have a real go to blazes upcut ball nose.
Downside is you are going to flip when you see the price! Upside will be cut speed and tool life.

Dave,
I stumbled across this site a few weeks ago.

http://www.endmilldiscount.com/end-m...ls-180-185.asp

Good prices and carry extra long lengths. I haven't used them yet, but will in the future.

[bleeth]

Thanks for the link Ben. Here is another supplier that has very good pricing on a variety of end mills (Original credit for this source to Brady):

http://obergbrothers.net/

And as someone else mentioned recently, Ballew tools is very nice to deal with.
I suggested the Vortex bits for this job as they are a total top performer in the industry for those type of bits much like Doctor Joe recommends Belin Tools as Aces for his work. They are pricey but last a long time and have fabulous geometry for removing a lot of material quickly.

[steelhead]

Dave,
Thanks for the link. I'll check them out.

I'm not familiar with Vortex... Just checked them out, and it looks like an excellent cutter. Yeah pricey, but I can see how the tool would last a long time.

Thanks for the tip.

What caught my eye on the link I sent you was the long lengths that are available. We cut allot of odd shaped stuff, and to get around not having a 5 axis (which I plan to build one day) we need the long lengths. There hard to find!

That was me who mentioned Ballew Saw And Tool. It's good to know someone else is buying from Fred and Jack. FYI I believe they are going to be re-doing their site and optimizing it. I gave Jack the contact info for the company that takes care of our site and he has been talking to them. They have been burned allot in the past. It would be good for them, I hope they do it.

[knight_toolworks]

the cutting problem I had when I was cutting the block out. the downcut was not great on the wet cherry. works fine on every other wood but not wet. but it was the longest bit I had on hand. I have hollowed out 3" deep boxes with those bits but they sure don't work on wet wood cutting that deep. the shavings don't come out of the slot.
The customer wanted as little toolmarks as possible and no sanding so the shape would not change so I used a small bit.
not sure on a larger bit if the marks would show more. on the next one I will try a larger bit. but I was limited to what I had on hand. it only took a few minutes each to do the roughing path so no real reason to change bits. I did both of them in about a hour and changed 200.00 that as at least 50 below the last person doing it. so it was just easier doing it all with one bit.

[Gary Campbell]

Steve...
Have you tried a large core box bit? Use the largest diameter that will allow you to cut in the relief. No bit change and time savings from generous stepover. The carbide insert shear geometry may help with the wet wood. Throw the rpm to it, as the bit wont heat, nor should the cherry burn if its wet.

[knight_toolworks]

I think that may be what the other guy used. I did nto have any cuting issues on the 3d part. it cut really clean. I was more worried about tool marks. at the small end a 3/8" may be too big though I ma not sure.
time wise the whole thing was faster then I expected and faster then my competitor.
so the customer is wiling to pay any extra to have the molds a clean of toolmarks as possible. any small toolmarks or fuzz get burned out with the glass blowing. the wood is kept soaking wet the whole time.
He will just bring me chunks of logs as needed.

[steelhead]

Gary a core box bit is a good choice.

On the cherry burning, I was referring to that in general!;)

Steve,
I drew this for you real quick like to give you an idea how a larger size can help out with both time and cut quality.

Hope it helps.

[knight_toolworks]

looks good. most of my 3d work has been detail work. Plus this was a rush thing and I did not have the time to hunt up bits.
At least with this wood there is no dust flying around. but I vacced it all up so it would not swell my spoilboard.
the customer wanted to try a mdf mold with graphite in it see how it worked with the glass blowing.

[bcondon]

Hey Steve,

how many of these do you need to make?

The reason for the question is that I have a repetitive project that has multiple tool changes, I set up my table (if they are small enough) and make some large number of them by using the same cut file but just shifting the
origin to a new location and run the same cut file.

By doing this, you set up he tool once, let it cut, say 10 objects and then load the new tool and run that cut file using the same origins, then you have 10 done without 10 tool changes.

You may know all this but I do this often and would be glad to give a sample main file (that changes the origins) and a small cut file that uses them (and how to edit those files so you do not start and stop your spindle/router)

Thanks
Bob Condon

[knight_toolworks]

only the two but I am doing the positives of this and a bottle. so I hot glued the mdf blocks to a sheet of thin plastic and I am changing bits for roughing.

[bcondon]

Darn...

I hoped you were making 100K of them!

BC

[knight_toolworks]

(G) but these sure pay will.

[widgetworks_unlimited]

It's funny how we have our tried and true bits that we automatically goto for all projects of a certain type - and how sometimes things don't workout despite a history of jobs well done.

Like Steve, I would have reached for a 1/4" or 1/8" ball nose first - even though I have a 3/8" and 1/2" sitting right next to them. I can't think of any projects I've done that involve similar 3D contours. Usually it's the details and depths that make a 3D carving standout.

I'm looking forward to trying a 1" ball nose on my next large carving - probably a on the 4th axis. I don't have the patients to wait around all day or to sand tiny tool marks out.

[myxpykalix]

Russ If you go to magnate.net and get a 1", 2" or 3" core box bit I think you will find that there will be little sanding needed. When i have made baluster and small legs on my legacy using a bit similar to the ones used in the link i gave you for the legacy demo, I have been surprised at the smoothness achieved.

I can't tell you what feed/speed because it is a totally different gearing/motor combo but the object is to take more material off in a roughing pass (so to speak) but it be smooth.

[steelhead]

Jack,
Thanks for the link to that site. That came in handy for me as well. I'm beginning to believe that this site is the "Facebook of woodworking for us woodworkers". Cool:cool:

[myxpykalix]

Ben,
I like your "moniker" below your name. I can look out my front door and see Thomas Jeffersons house from where i live. Several years ago we were commisioned to do some video work at Monticello and you would be surprised at some of the hidden staircases and things built into that house that the average person never sees.

[steelhead]

Jack,
I would love to live where you do. Better yet there and own property that borders Jefferson's place. He is my all time favorite person in history. Admittedly I have not studied to many others, I have not found them to be as interesting. I have more respect for him and he he has done for our country than anyone else. Odd I never hear anyone in office today mention his name.. I don't think I have ever heard it. I better stop there, I may end up opening a thread that never ends....

[michael_schwartz]

Oddly enough I made a similar glass mold a few weeks ago for a local glass blower, but we decided to use kiln dried cherry, and last I heard the mold was holding up well. We had originally planned to use green cherry, but we couldn't locate a suitable piece in time.

I machined mine with a 9% step-over but the customer was more than satisfied with the surface.

[knight_toolworks]

yes i bet it would be hard to find. they buy logs and just chainsaw off chunks as needed. I think a larger stepover would have been closer to what the other guy was doing. but I could do 4% and still charge less and make almost 200.00 a hour. with a larger bit it woulds be even faster. they brought me a mold sample and even soaking wet it was black on the inside. they keep the molds in water between uses and at all times when not in use.

[michael_schwartz]

Best part was they gave me the first beer stein to come out of the mold I made. I got to watch them blow some glass as well, and what they do is simply amazing. Really interesting to see glass in its liquid state.

From what I understand there are very few people currently making these molds, and one is about to retire. Definitely a good opportunity to develop a working relationship with local glass blowers.

I did my rough out with a 1/2" straight flute bit with a mortise tip. I believe I ran my dust shoe for the roughing pass but I didn't have any trouble. I suppose with wet wood, you could do a rough layout and hog some wood out at the drill press.

I modeled the mold I cut in aspire, but I am guessing they provided you with a file.

[knight_toolworks]

They did provide the file I could not draw in 3d if I had too. I found dc was usless with the wet wood the shavings just pile up. As long as I don't use a downcut everything is fine too.