Jet Variable Speed Combo Meta/Wood SFM Question [Solved]

[Shiseiji]

Hi all, TIA. Bottom line Up Front, I'm having poor luck trying to cut some 1/2" aluminum bar in this bandsaw.

Background. Jet band saw with a two speed transmission and a Reeves drive. The manual doesn't list the max/min SFM in each range, but lists 2,600 as the max SFM for wood, and 90-340 SFM for metal with a SFM static indicator on the Reeves drive. School of hard knocks, burned up a couple of bi-metal blades by NOT reading between the lines that after pulling out on the dog clutch, continue pulling on the knob and rotate the bottom wheel until the helix gears engage (with a nice "klunk").

Manual lists 3k SFM for 4" aluminum, increase speed by % as material thins; 15% for materials 1/4- inch thick, 12% for 3/4-inch thick, 10% for 1-1/4-inch thick, and 5% for 2 1/2-inch thick. Since the max speed is 2.6k, that's what I'm using for my 1/2" test rod.

Now the problem. If this simple math is correct. 2,600 SFM divided by 60 = ~43.33 sfm per minute (uh second). With a brand new bi-metal 1/2" 14 tpi blade I can't get the thing to cut 1/8" sfm. By which time the material can't be held due to friction heat.

What am I screwing up?

Again, TIA.

 

[Ulma Doctor]

What alloy of aluminum are you trying to cut?
300sfm should be sufficient for all but the hardest alloys of aluminum with HSS tooling

 

[Shiseiji]

Sorry, 6061-T6511.

 

[markba633csi]

Is blade installed correctly? (teeth pointing down)
The manual is clearly wrong; you should be using the low range for all metals- the high range is for wood
300-350 sfm for aluminum, 100-200 for steel approximately

 

[projectnut]

3000 SFM sounds way too fast for cutting any metal. My Startrite bandsaw has 3 speeds. 60 SFM,100 SFM, and 160 SFM. Aluminum is normally cut at 160 SFM

As for blades the rule of thumb is no less than 3 teeth engaged at any time, and no more than 23. For a 4” piece you should be using a blade in the 8 tpi range. You can cheat a bit by lowering the blade speed and feed rate.

With the high speed rate you’ve probably quickly filled the gullets and dulled the blade. When a 4” round is finished cutting in my saw it’s just warm to the touch, not hot

 

[Shiseiji]

Yes, blade is in correctly. Had to reverse the twist when installing it, quick lesson.

300-350 sfm for aluminum, 100-200 for steel approximately

The 300 makes a lot more sense . . .

 

[Shiseiji]

3000 SFM sounds way too fast for cutting any metal. My Startrite bandsaw has 3 speeds. 60 SFM,100 SFM, and 160 SFM. Aluminum is normally cut at 160 SFM

As for blades the rule of thumb is no less than 3 teeth engaged at any time, and no more than 23. For a 4” piece you should be using a blade in the 8 tpi range. You can cheat a bit by lowering the blade speed and feed rate.

With the high speed rate you’ve probably quickly filled the gullets and dulled the blade. When a 4” round is finished cutting in my saw it’s just warm to the touch, not hot

And another one bites the dust and explains why trying to follow the manual didn't work so well.

The test piece is 1/2". The 4" is what the manual uses to start a percent of SFM scale for speed increases as work diameter/height decreases.

Thanks much, as soon as I read your rule of thumb it came back from probably 50 years ago in HS shop class or A&P general studies. I was honestly trying to remember, but couldn't pull it up. Thanks for posting it else I'd still be trying to remember.

 

[Shiseiji]

Late update, my apologies. Manual states to disengage the dog clutch. Doesn't mention it takes another ~ 3/4" of movement while jogging the lower wheel to get the transmission gears to engage. Blinding Flash of the Obvious (BFO).

Thanks again for the assistance.

Ron

 

[Rich Berg]

HI, I cut 6061 with my wood cutting band saw and table saw. I use skip tooth blades on my band saw, they seem to like aluminum and brass, no steel. you may be using the incorrect blade for aluminum, also a dull blade will give you fits.
Rich

 

[Shiseiji]

Thanks Rich, it was 100% speed related. Like you said, I have used wood blades on non ferris metal with good results. The aluminum in this case was more test on what the heck was going on.