[Bob La Londe]

For me its a cost and time equation. When I take the head apart I want to be able to put it back together very quickly. I am fortunate in that I have other mills, but I don't want to have one down for days, and the others tied up making parts for it. I never had issue with ths noise level on the Hurco. Like I said, if Dave's kit wasn't six months out I woud just buy his and be done with it. Then I could be swapped out and running in a couple hours. I mostly wanted to know if there was an over riding problem with using a timing belt, and it appears there is not.

While rigid tapping sounds wonderful, its not something I would likely do with a regular 3 phase spindle motor. I might if I went to an AC servo spindle. Spiral thread milling meets most of my odd size tapping requirements, and 95% of the rest is done on the drill pess with a tapping head.

Again for me its about cost and time. (mostly time)

Look at the cost of billet. Its not much cheaper than a complete pulley.

[hjl4]

I agree.
Here are some facts about different belt configurations which the US Energy department has provided.

"The majority of belt drives use V-belts, which use a trapezoidal cross section to create a
wedging action on the pulleys to increase friction and improve the belt’
s power transfer capability. Joined or multiple belts are specified for heavy loads. V-belt drives can have
a peak efficiency of 95% or more at the time of installation. Efficiency is dependent on
pulley size, pulley wear, V-belt alignment, transmitted torque, under or oversizing belts
for load requirements. Efficiency can deteriorate by as much as 5% over time if slippage
occurs because the belt is not periodically retensioned.

The most important operational and maintenance issue in a V-belt drive is its tension. If
belts are too loose, they tend to vibrate, wear rapidly, and waste energy through slippage.
If belts are overtightened, they will show excessive wear. An increased belt load may
shorten bearing life through excessive lateral loading and could possibly result in shaft
failure. The proper tension of a V-belt is the lowest tension at which the belt will not slip
at peak-load conditions. After the break-in period, belt tension should be checked every
3 to 6 months.

A notched belt has grooves or notches that run perpendicular to the belt’s length, which
reduces the bending resistance of the belt. Notched belts can use the same pulleys as
cross-section standard V-belts. They run cooler, last longer, and are about 2% more
efficient than standard V-belts.

Synchronous belts (also called cogged, timing, positive-drive, or high-torque drive
belts) are toothed and require the installation of mating grooved sprockets.
These belts operate with a consistent efficiency of 98% and maintain their efficiency over a wide
load range.

In contrast, V-belts have a sharp reduction in efficiency at high torque due
to increased slippage. Synchronous belts require minimal maintenance and retensioning,
operate in wet and oily environments, and run slip-free. However, synchronous belts are noisier than V-belts, less suited for use on shock-loaded applications, and transfer more vibration due to their stiffness"

So there you have it.

[mactec54]

Anyway, I wasn't really challenging anybody's choice of multi V-groove belts. I just wanted to know they why of the thought process.

You asked for the Why

I think people throw "better" and "best" around a little to easily.

I gave a simple answer, these Belts are ideal for these low HP machines to use the Poly-V Belt, this is a very good choice for the kits they are making

[mactec54]

I agree.
Here are some facts about different belt configurations which the US Energy department has provided.

"The majority of belt drives use V-belts, which use a trapezoidal cross section to create a
wedging action on the pulleys to increase friction and improve the belt’
s power transfer capability. Joined or multiple belts are specified for heavy loads. V-belt drives can have
a peak efficiency of 95% or more at the time of installation. Efficiency is dependent on
pulley size, pulley wear, V-belt alignment, transmitted torque, under or oversizing belts
for load requirements. Efficiency can deteriorate by as much as 5% over time if slippage
occurs because the belt is not periodically retensioned.

The most important operational and maintenance issue in a V-belt drive is its tension. If
belts are too loose, they tend to vibrate, wear rapidly, and waste energy through slippage.
If belts are overtightened, they will show excessive wear. An increased belt load may
shorten bearing life through excessive lateral loading and could possibly result in shaft
failure. The proper tension of a V-belt is the lowest tension at which the belt will not slip
at peak-load conditions. After the break-in period, belt tension should be checked every
3 to 6 months.

A notched belt has grooves or notches that run perpendicular to the belt’s length, which
reduces the bending resistance of the belt. Notched belts can use the same pulleys as
cross-section standard V-belts. They run cooler, last longer, and are about 2% more
efficient than standard V-belts.

Synchronous belts (also called cogged, timing, positive-drive, or high-torque drive
belts) are toothed and require the installation of mating grooved sprockets.
These belts operate with a consistent efficiency of 98% and maintain their efficiency over a wide
load range.

In contrast, V-belts have a sharp reduction in efficiency at high torque due
to increased slippage. Synchronous belts require minimal maintenance and retensioning,
operate in wet and oily environments, and run slip-free. However, synchronous belts are noisier than V-belts, less suited for use on shock-loaded applications, and transfer more vibration due to their stiffness"

So there you have it.

So who is talking about common old V-Belts, all of this information on V-Belts has nothing to do with Poly-V Belts which is a totally different type of Belt

Trying to pretend again you know something about the subject

The Bridgeport Head conversions I used to do by the dozen, the one in the photo does Rigid Tapping, Here is the Head with the top on with a spindle Encoder for the Rigid Tapping

Enjoy

[hjl4]

I don't have to pretend anything.
What is the total area of contact of your superior belt?

Do you have a belt tensioner?

When your belt gets moisture on it, can it guarantee positive drive?

Don't even bother replying, as my past discussion with you on a different topic, leaves me to believe, you know everything.

[Bob La Londe]

Thanks everybody for your insite into the differences between the belt drives. I see the posititves in each, and iterate that better or best is conditional.

[Fireman11]

I was under the impression that the advantage of timing or multy groove belts over v groove pulleys was they worked well with much smaller diameter pulleys that would fit on the top of a machines head.