What cutters to use for custom micro-v pulleys?

[ChrisAttebery]

I just cut a set of Micro(Poly) V pulleys last month. I'm a die hard carbide user but I opted to use a ground HSS tool. It worked like a charm. Cut a groove, step over .092", repeat.

 

[robotwizard]

Lathe is a PM-1127. Have a 1.5hp marathon motor with 1000:1 torque to upgrade from the original 1hp, but not installed yet. Would 3/8" or 1/2" shank be better?

Looks like the Ebay set was a good buy, but unfortunately I got there too late.

Matts site says sets are on backorder

What lathe do you have? These are some good starter sets.

First link is for a 3/8" shank set. It's on sale now. Perfect for an AXA.
https://www.ebay.com/itm/SHARS-7PCS...972823?hash=item1ca79a0397:g:OKQAAOSwkrFagcTe

This is the same set as above but 1/2" shank. These will fit your AXA holders but may be too big for your lathe.

https://www.ebay.com/itm/SHARS-1-2-...166083?hash=item4602f2a103:g:PcAAAOSwcBhWU1kt


This set is great, sold by a friend of mine and sponsor of this web site. These are different inserts than above but unlike the sets above, all the insert holders take the same insert which is VERY convenient. This is my preferred recommendation from a technical perspective but, they are a little more expensive.

Here's a 3/8" set.
http://www.precisionmatthews.com/sh...ool-set-sized-for-axa-quick-change-tool-post/

Here's a 1/2" set.
http://www.precisionmatthews.com/sh...ool-set-sized-for-bxa-quick-change-tool-post/

Yes, a DCMT can cut aluminum.


Ray

 

[Ray C]

Lathe is a PM-1127. Have a 1.5hp marathon motor with 1000:1 torque to upgrade from the original 1hp, but not installed yet. Would 3/8" or 1/2" shank be better?

Looks like the Ebay set was a good buy, but unfortunately I got there too late.

Matts site says sets are on backorder

You could go either way but most "hobby-level" lathes with 14" swing and under, are not designed for hogging. With 1/2", all your toolpost holders will need to be adjusted about as low as they can go. With 3/8, you might have an occasional (rare) problem if you ever need to extend the tool to reach a cut. If I had no plans to ever upgrade to a larger lathe, from 11" swing, I personally would go with 3/8". It's appropriately sized and won't get in the way of your setups. As time passes, you could get a few 1/2" shanks to handle the fewer situations when extra stick-out is needed. In all reality, when you need extra stick-out, you probably need to re-think the setup and how you're approaching that cut. Anyhow, if you think you might upgrade to a 12 or 14" lathe, then go with 1/2".

A quick question: Why are you upgrading the motor on the lathe? 1 HP is plenty for an 11" swing lathe. You'll never be able to utilize the extra power because the rest of the machine will be subjected to undue stress.

Ray

 

[cjtoombs]

I would try the form ground cutter mentioned above and go stright in, cutting on both sides of the tool, as a first pass. If your lathe isn't up to the task, you will get chattering. If that happens, grind one side of the tool with a bit of relief and feed it in at half the included angle with the compound (20 degrees in this case) with the 20 degree side of the tool doing the cutting. Make sure the tool is still square with the worrk. That should help with any chattering. Unless you have a very light lathe, I wouldn't expect any problems with the straight in method with those shalow groves in aluminum.

 

[robotwizard]

You could go either way but most "hobby-level" lathes with 14" swing and under, are not designed for hogging. With 1/2", all your toolpost holders will need to be adjusted about as low as they can go. With 3/8, you might have an occasional (rare) problem if you ever need to extend the tool to reach a cut. If I had no plans to ever upgrade to a larger lathe, from 11" swing, I personally would go with 3/8". It's appropriately sized and won't get in the way of your setups. As time passes, you could get a few 1/2" shanks to handle the fewer situations when extra stick-out is needed. In all reality, when you need extra stick-out, you probably need to re-think the setup and how you're approaching that cut. Anyhow, if you think you might upgrade to a 12 or 14" lathe, then go with 1/2".

A quick question: Why are you upgrading the motor on the lathe? 1 HP is plenty for an 11" swing lathe. You'll never be able to utilize the extra power because the rest of the machine will be subjected to undue stress.

Ray

Thanks. My motivation for the motor upgrade isn't to increase horsepower. Besides replacing the no-name oem motor with a higher quality unit that will last, the Marathon will provide constant torque all the way down to zero rpm. I've seen videos where guys can grab the chuck and stop the motor at low rpm settings with this particular lathe with the original motors. The upgraded motor/vfd will also interface better for computer control of spindle for threading and constant sfm when I do the cnc conversion at some future time . I was looking for a motor to upgrade my PM727 mill for the belt conversion to be able to run the spindle at 5k for small cnc cutters, while maintaining low speed torque for larger cutters etc. I ran across these 1.5hp inverter duty 1000:1 motors that were new surplus at a fraction of new cost. They had 2 left, so I decided to get one for the lathe as well.

 

[robotwizard]

I would try the form ground cutter mentioned above and go stright in, cutting on both sides of the tool, as a first pass. If your lathe isn't up to the task, you will get chattering. If that happens, grind one side of the tool with a bit of relief and feed it in at half the included angle with the compound (20 degrees in this case) with the 20 degree side of the tool doing the cutting. Make sure the tool is still square with the worrk. That should help with any chattering. Unless you have a very light lathe, I wouldn't expect any problems with the straight in method with those shalow groves in aluminum.

Thanks cjtoombs, I will give that a try.

 

[Ray C]

Thanks. My motivation for the motor upgrade isn't to increase horsepower. Besides replacing the no-name oem motor with a higher quality unit that will last, the Marathon will provide constant torque all the way down to zero rpm. I've seen videos where guys can grab the chuck and stop the motor at low rpm settings with this particular lathe with the original motors. The upgraded motor/vfd will also interface better for computer control of spindle for threading and constant sfm when I do the cnc conversion at some future time . I was looking for a motor to upgrade my PM727 mill for the belt conversion to be able to run the spindle at 5k for small cnc cutters, while maintaining low speed torque for larger cutters etc. I ran across these 1.5hp inverter duty 1000:1 motors that were new surplus at a fraction of new cost. They had 2 left, so I decided to get one for the lathe as well.

Sounds pretty cool then. Take pictures and let us see how it's working out. What kind of controller will you use with it?

Did you finally get some tool holders?

Ray

 

[jbolt]

I agree with Bob. Don't over think it. I have made on the order of two dozen or more micro-v step pulley sets for people for belt drive spindle conversions. I use a HSS T-Type cut-off blade ground to 40 degrees with a lightly blunted point. Works like a champ. The angle doesn't have to be perfect just close.

 

[rowbare]

The thing you need to be mindful of is that even though you have constant torque down to very low speeds, you have next to no horsepower at those low speeds. Horsepower is a function of torque and speed so if you motor is rated at 1.5hp at 1800 rpm, it is only putting out .15 hp at 180 rpm whereas if you use mechanical reduction to get down to that speed you still have 1.5 hp.

Why is this significant? Because Metal Removal Rates are a function of HP. So if you use mechanical means to get to 180 rpm, you can hog like crazy. If you use a VFD to get to 180 rpm not so much; in fact you can only remove about 1/10th of the metal per unit time. That gets old really fast.

One way to get around this is to use a much larger motor than seems appropriate for the size of the machine. The extra power doesn't do much for you at the upper end due to machine limitations but will help you a lot at lower speeds. Also it is a good idea to have two speed ranges, a high range for normal use and a low range for threading and large diameter stock.

bob

 

[P. Waller]

The thing you need to be mindful of is that even though you have constant torque down to very low speeds, you have next to no horsepower at those low speeds.

bob

What he said. Work Over Time

Horsepower + Torque in Ft. Lb's. X RPM/5252