Author Topic: Router speeds and belt drive questions.. (Read 11199 times)

John Hill · « **on:** February 18, 2009, 04:51:12 PM »

I am building a copy router, it is of the parallelogram type but I am not happy with it so far..

The main problem is the weight of the router motor, usually with these machines the solution to that is another arm and a counterweight but I would also like to up the horsepower and get variable RPM.

SO, the idea is to mount a much bigger motor near the cross piece (where its weight wont be an issue) with a belt drive to a vertical spindle. But how fast can I run a belt drive? 30K maybe? (Sounds a bit scary!)

Also, this machine will be used for wood 3D copying but I also want to cut shapes in sheet aluminium using a 3mm cutter, what RPM do I need for aluminium? Really fast or quite slow. If possible I want to avoid liquid lubricant.

Any thoughts?

[Yes, it will be painted one day, at the moment it has a nice even coating of 'Seaside Ochre'.]

SPiN Racing · « **Reply #1 on:** February 18, 2009, 07:25:10 PM »

You really dont need to have a motor that spins very fast.. Nor the belt itself.

Simple put a larger pulley on the engine.. and real small on the spindle.

Bernd · « **Reply #2 on:** February 18, 2009, 10:23:04 PM »

John,

I've tried using a variable speed Bosch router, 1HP, on aluminum. The aluminum is/was 6061 1/4" thick. No matter what speed I ran it at the cutter got gummed up. Of course I used a 4 lipped and 2 lipped HSS mill cutter. Neither worked very well.

The idea of the motor being belt driven is fine in my opinion.

I hope some of what I tried can help out on your quest as far as trying to cut aluminum is concerned.

Bernd

John Hill · « **Reply #3 on:** February 19, 2009, 02:43:09 AM »

Hi Bernd, did you try really slow? Did you try with lubricant on the bit? I had a bit of success using Vaselene on the bit and smeared on the work. Friends said I should be using kerosene or CRC-56 but I would really like to be able to do this without flooding the workshop and coating the walls and ceiling.

sbwhart · « **Reply #4 on:** February 19, 2009, 03:02:00 AM »

Hi John

Have you tried WD40 ?

Stew

Bernd · « **Reply #5 on:** February 19, 2009, 09:43:29 AM »

John,

The slowest that router would run was over 1000rpm, still to fast. At that speed I don't think any kind of lubricant would stay on the cutter.

I wanted to but never tried a single flute cutter. Don't if one is available commercialy. That might have worked. I think the aluminum is just to gummy to try with a router, plus using it like you want makes for not so rigid setup.

Sorry to be such a wet blanket on this. It's just I tried using a router to route out a large, 14" (355mm) dia. hole in 1/4" (6.35mm) aluminum plate. Wasn't very sucessful.

Bernd

bogstandard · « **Reply #6 on:** February 19, 2009, 11:28:20 AM »

Bernd,

Don't you mean 10,000 RPM. I regularly use 2,000 on my mill to run small cutters in ali, with a bit of WD40 as lube.

The WD isn't there as a main lube, but to stop the ali chips bonding to the cutter faces.

Above about 4,000 RPM I would suspect you would start to have trouble clearing the swarf away and keeping the tool cool. You could try a high pressure jet of air like the CNC lads do.

John

John Hill · « **Reply #7 on:** February 19, 2009, 05:25:24 PM »

Yes Stew, WD-40 is useful but it seems I have to almost flood the work to stop gumming with the high speed router I have been using.

I am hoping getting variable speed will lead to the answer and I have stepped pulleys in mind, but the question is can I use a belt drive for really high speed work?

Hmmmm, an air jet should be easy enough!

bogstandard · « **Reply #8 on:** February 19, 2009, 05:42:39 PM »

Just to answer your question John.

Yes you can use belts at high speed. PCB drilling machines can run at over 80K, most run at around 50K, and they are belt driven. Nothing spectacular, just mini V pullies with either a fabric reinforced belt or Redthane. I used to replace the belts with 1/4" Redthane, and as long as you can get a good heat join, they work great.

You would need to make sure the belt is fully enclosed for safety reasons, if a belt was to go at that sort of speed, it would be like a shotgun going off.

The bearings for the spindle would be your main problem at these speeds. Standard bearings normally only go up to 30 to 40K RPM.

John

Bernd · « **Reply #9 on:** February 19, 2009, 06:06:16 PM »

Your right John, 10,000RPM.

I thought that didn't look right.

Bernd

John Hill · « **Reply #10 on:** February 19, 2009, 06:12:39 PM »

Thanks John, whats Redthane? Is that like 'O' ring stuff?

Most of the bearings in my boxes are salvaged from really old computer tape drives so I cant imagine they were designed for high speed though they would have been the best available at the time (early '70s').

bogstandard · « **Reply #11 on:** February 19, 2009, 06:55:02 PM »

John,

Bearings are very cheap nowadays, it might pay you to invest in a pair for the job in hand.

http://www.poly-products.co.uk/beltext.htm

In the UK, most engineering suppliers stock it in all different sizes. You can get it as a solid belt, that you join by melting the ends and sticking together quickly. Full strength bond almost as soon as it is cool to the touch. For the tubing you can get little adaptors that stick in either end of the belt and gives a very good joint (this system was once retailed as emergency fan belts for cars), but I just join it by the heat method. I always have some in my shop just in case a belt breaks at an inopportune time. One of the main advantages is that you don't need to slacken the motor off to change the belt to a different position, you just stretch it and move it over. It is great if you have a belt driven lathe, where you would normally have to take out the spindle to change the belt. Just feed it thru and melt the ends, job done.

John

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