Myford ML7 – Direct or Back Gear

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Myford ML7 – Direct or Back Gear

This topic has 9 replies, 7 voices, and was last updated 25 October 2018 at 23:03 by Hopper.

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23 October 2018 at 16:39 #377278
Scott Underhill
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@scottunderhill83729
Do you use direct drive during normal turning operations? I assume direct drive is when the bull gear and the bronze gear/vee cone are locked together via the adjustable cog on the bull gear. The back gear lever would be in the down position.

In order to engage the back gear I assume you first have to raise the cog on the bull gear so that he bronze gear/vee cone can rotate independently of the bull gear, then raise the back gear lever. In this instance does the bronze gear/vee cone rotate around the main shaft and need to be oiled to keep it from seizing the bronze bushing onto the shaft. How often does it need to be oiled. Do you need to be worried about pulley speed to keep the bronze bushing from grabbing the main shaft.
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23 October 2018 at 16:39 #9382
Scott Underhill
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@scottunderhill83729
23 October 2018 at 17:49 #377294
not done it yet
Participant
@notdoneityet
I’ll answer your first point. It depends on what you call normal. Same diameter as faceplate and HSS cutters on steel would definitely benefit for the low speeds of the back gear
23 October 2018 at 18:54 #377303
Robbo
Participant
@robbo
Scott

Direct drive, which is when the bull wheel is locked to the pulley cone, will do for most everyday turning; when a lower speed is needed because of larger diameter workpieces, or for some faceplate work, or deep/large diameter drilling, then the back gear offers a reduction in spindle speed. The backgear is probably most frequently used when cutting threads, as this is more easily controlled at lower speeds, as are some parting off operations.

There is an oil nipple on the large pulley behind the bull wheel, and Myford recommend oiling this "Frequently" when using backgear. You decide how often equals frequently! There is an oil nipple on the backgear spindle which should also be oiled "Frequently" Myford also say the pulley oil nipple should be "well lubricated"

The main pulley cluster will rotate at the same direct drive speed selected whether you are using direct drive or backgear. As you say, in direct drive the bull wheel is locked to the pulley cluster, for backgear it is separated by moving the sliding key and raising the backgear lever. This takes the drive from the pulley cluster gear via the backgear reduction gear on to the bull wheel.

Basically, if its a Myford, keep the oil gun handy and give it a squirt whenever you use it seems to be the philosophy. The lubricant is a thin oil and runs off easily. The only problem you will get from too much lubrication is oil dripping out of the headstock and a messy drip tray/bench.
23 October 2018 at 19:03 #377306
Pete Rimmer
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@peterimmer30576
Direct drive is favoured because it means less noise and wear & tear.
23 October 2018 at 21:18 #377333
Scott Underhill
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@scottunderhill83729
Thanks for the all the information.
23 October 2018 at 21:37 #377337
Gordon A
Participant
@gordona
You may also be aware that using backgear not only reduces speed but also increases torque.
25 October 2018 at 12:55 #377595
larry phelan 1
Participant
@larryphelan1
Sparey gives a useful formula for calculating turning speeds for different materials——cutting speed divided by 1/4 of work dia= rpm.

For mild steel,cutting speed is about 80 feet per min

For brass,it,s about 200 ft per min.

So,it,s easy enough to pick the right speed,taking into account the dia of your workpiece. He also makes the point that you might find yourself using back gear more often than you think. I found this to be the case,much to my surprise. Cutting speeds for all materials are available.

Hope this helps somewhat.

/
25 October 2018 at 13:26 #377603
Scott Underhill
Participant
@scottunderhill83729
Yes that does help. I just inherited the lathe and getting used to all its functions. Never owned one before but always had an interest. In the process of practicing turning down some scrap mild steel shafts to get used to it.

thanks for the help.
25 October 2018 at 23:03 #377688
Hopper
Participant
@hopper
Rule of thumb for turning steel, using HSS tool bits:

1" diameter: 400rpm

1/2" diameter: 800rpm

2" diamter: 200rpm
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