lathe belt

[macmarchParticipant @macmarch]

HPC and Davall explain it differently, but the pitch is controlled by the chord. You can’t have a 21 1/2 tooth gear nor a 21 1/2 tooth wheel for a belt. Nevertheless Chester need a firm prod in the nether regions.

 

Edited By macmarch on 04/12/2010 21:50:07

[tedParticipant @ted]

hi gordon

i too have a chester DV8 lathe and had the same problem last week with the motor drive belt but got a vee belt the same length and vee angle but no teeth on the outside from a farm &industial supplies in irealnd so far the belt the belt works on the lathe without slip and  min tension and the tacho works .i have been to told that chester don,t export to ireland directly anymoore and have go thru a sale company in ireland who mainly deals with colleges .i have already replace the 3/4 hp motor as the insulation on the armature of the motor had broken down and was causing the RCD breaker to trip .This was more than likely cause from drilling under heavy load or heavy cutting .The new motor is a 1hp now a small gain but just might reduce the chances of this happen again

[Trevor Drabble 1Participant @trevordrabble1]

   As a Myford user, I have so far found this thread extremely interesting and enlightening……….

[Gordon AParticipant @gordona]

Peter,

 

Thank you for your interest, but there is very little similarity between the  Hobby 818 that I owned and the Mashstroy in the picture to which you refer.

Mine looked similar to the Emco Compact 8, but was much more basic. The bed was similar to the Mashstroy in that it had a combination of flat and vee form, but the saddle and tailstock ran on the outer flat parts with the centre vee section preventing lifting of both.

The Gates belt ran directly from the motor to the spindle pulley with no countershaft, giving 4 direct speeds from 250 to 1700 rev/min.

It did however have the advantage of a Myford type spindle nose which made accessories easy to source.

I did once make a half-hearted attempt to trace the origin of this machine, but as I was at least the third owner, I assumed that Axminster had stopped selling this model long ago.

Gordon.

[John OlsenParticipant @johnolsen79199]

Trevor, I don’t know if you are trying to assert that the Myford does not have trouble with belts, but if you are I would point out that there is a well known modification to improve the Myford belt drive. This was originally published about 30 years ago, and is still available as a kit and set of drawings from one of the suppliers. My own experience with my ML7 has convinced me that the belt centres on the Myford are too short and the pullies too small for the type of belt supplied, and this leads to heating of the aluminium alloy pulley on the spindle. This can be sufficient to cause the bronze back gear to come loose in the pulley…it is only a press fit. In order to fix this, one must dismantle the headstock bearings. I’ve adapted the poly V belt conversion, which was designed for the Super 7 and made it work on the ML 7. The poly V belts do run quieter and cooler than the originals, as well as providing four ratios instead of three.

 

So all is not exactly sweetness and light in the Myford camp either.

 

regards

John

[Gordon WParticipant @gordonw]

Thanks again for suggestions. Terry,  did not get email, so did not ignore, grizzly is speed controlled motor. Just to repeat, the belt I need is a toothed belt ,from motor to counter-shaft. I have tried all the usual suppliers with no luck. Difficult to measure accurately as belt is a bit mangled, also teeth are only about 1mm high, so pitch line is a bit debatable. All I know is it does not match any of usual standards,or come anywhere near. Teeth are for drive only, not for timing. Can’t find F belt. Looks like redesign is the way to go, but will keep trying to find another supplier, would be a great help if could get the original spec.

[Martin WParticipant @martinw]

Gordon

 

Have you tried posting on the Chester forum itself. It may attract attention to this problem from other users of the Chester DB8 machines and if they is enough interest may cause Chester UK to change their mind re stocking spares.

 

Just a thought.

 

Cheers

 

Martin

[blowlampParticipant @blowlamp]

Gordon.

Would it be a big job to change the pulleys and belt for something more current?

 

Martin.

[Keith LongParticipant @keithlong89920]

Hi Gordon W

Are the pulleys on your lathe “toothed” to accept the teeth on the belt – I’ve recently seen a lathe that looked at first sight that it was using a timing belt drive, but while the belt was toothed the pulleys were plain. I suspect the belt was being used for it’s higher tensile strength allowing the use of a smaller section. 

You say that the teeth are not for timing but just for drive – sounds as though your looking for the wrong thing in going for a timing belt – you want a “cogged” v belt – very common. They look like timing belts at first sight but the “teeth” are there to give the belt greater flexibility for use on smaller pulleys and top allow a better fit to the pulley flanges. All you need to do is find a suitable section that will fit on to your pulleys. You might find it useful to download the Gates catalogue from here:-

http://www.beeline.co.uk/gates-drive-belts.aspx

and have a look through. Your best bet is to find a local belt stockist – there will be one where-ever you are in the country, and have a talk to them, taking your old belt with you. Once you know what will fit buy 2 – then you’ll never need to fit the spare!!!!!

Keith

[JasonBModerator @jasonb]

The belt drive DB8 does have toothed pullies so needs a toothed belt, changing to another pully is not easy as they are integral with the triple V pully wheels.

 

Gordon, if you follow the link to the BELT drive 6 speed NOT VARIABLE SPEED BD10 clone that Grizzley do you will see by downloading teh manual that it does have the same toothed/V pully arrangement as your lathe just not the same size.

 

And if you follow the link in the CNCzone thread that I posted you can all see the type of pully arrangement. The poster there specifically says that using other standard belts the teeth soon get out of sync with the pully due to the wrong pitch

 

 

My suggestion would be to skim the teeth off the pullies and take them down to the correct OD to suit easily available 5mm metric pitch belts and cut the corresponding number of teeth to suit that dia.

 

The easiest way to measure the belt pitch would be to count the number of teeth over a given distance, lay it out tooth up on a flat surface.

 

For an XL pitch you will have 15 teeth over a 3″ distance

For a T5 Metric you will have 20 teeth over 100mm

For the 3/16″ pitch F profile you will have 16 teeth over 3″

Jason

Edited By JasonB on 05/12/2010 13:17:01

Edited By JasonB on 05/12/2010 13:19:41

Edited By JasonB on 05/12/2010 13:23:33

[Gordon WParticipant @gordonw]

Jason , that is the very pulley. My plan, if all else fails is to turn the teeth of it, then bore a standard pulley to fit over the outside. If I end with a lower ratio, even better .Will have to the small motor pulley as well, of course. Might even be cheaper in the long run

[Peter G. ShawParticipant @peterg-shaw75338]

Gordon A,

 

Thanks very much for your reply. As you may well realise, there do not appear to be very many owners of my machine, hence my interest.

 

Regards,

Peter G. Shaw

[wheeltapperParticipant @wheeltapper]

Hi

Just had some good news from Chester, new belt for a Comet is £14. 95+vat.

 

nice to know they have them.

 

Roy

[Gordon WParticipant @gordonw]

Glad you’ve got a belt, W/tapper. I’ve emailed a couple of USA sources and hope for a result. It’s a great pity this has happened ‘cos I like the lathe, does just what I need with no electronics. Some obs. which may be of use to others with a similar set-up. I found embedded dirt in the wheel grooves, this may have resulted in belt stretch, clean them out, right down to the bottom. Keep an eye on belt tension, I used the “turn thru’ 90 deg.” method ,but have no idea what the tension should be. If using faceplate or big 4 jaw there is a huge inertial load to start up, giving it a start by hand helps. ( don’t try at home)

[TerrydParticipant @terryd72465]

Hi All,

 

I don’t know these lathes but is not the toothed belt drive  used to provide a positive feed to the driven shaft to ensure correct relationship much as the timing belt on a vehicle engine.  If so a vee belt solution would not work as slip would be introduced, if not then a vee belt would be a possible solution and would have cost less initially.  Why is there a toothed belt, can anyone answer?

 

Terry

[JasonBModerator @jasonb]

The toothed belt does not link to the spindle or any of the gear train, it is used to drive an intermediate shaft to obtain the lower speeds and I assume the teeth will slip less than a V belt.

 

Have a look at page 33 of this pdf it shows a similar setup on a 10″ grizzley lathe

 

J

[blowlampParticipant @blowlamp]

Looks like it could be a good candidate for a Poly-V belt conversion, if you can get the right length.

 

Martin.

[Gordon AParticipant @gordona]

Prior to parting company with my Hobby 818 lathe, I was planning to install a countershaft driven by a poly-V belt in order to reduce its bottom speed from 250 rev/min to something more acceptable.

I obtained a suitable belt from a local independent electrical shop specialising in domestic appliance spares.

The use of this type of belt in washing machines, dryers, vacuum cleaners etc is not uncommon.

 

Just food for thought.

 

Gordon.

 

 

 

[TerrydParticipant @terryd72465]

Hi JasonB,

 

If that is the case and the toothed belt is simply a drive from the motor to the countershaft.  Is it possible that this part of the drive is where the highest torque could cause problems and perhaps excessive slip at slow speeds?  The manufacturers must have had a reason to put this type of belt drive here.  If a vee or round belt would suffice surely they would have taken this cheaper solution?  And if they are just mimicking the European machines then the European manufacturers would likewise have a sound reason for this type of drive?

 

Sorry to seem nitpicking but it seems to me that someone, probably a design engineer, has seen the need, probably an empirical decision following experience, to put this type of drive here and if it were me I would research all possibilities before making such a drastic modification without knowing all the details.  That modification would be my last resort. Still, each to his own,  Let us know how you get on Gordon.

 

Terry

 

 

[John OlsenParticipant @johnolsen79199]

Hi All

 

I have been wondering about the torque requirement too, although since it is the first reduction when in the low ratio, it should not be handling as much torque as the second belt does.

 

Having seen the pictures of the setup, my own inclination would be to modify the pulleys to take a standard readily available toothed belt. Actually I would probably go the whole hog and use toothed belts for all of the reductions, although that might be a problem if there is not enough room. I did that with my Unimat and fitted it all within the standard cover, a great leap forward for the little machine. One advantage of the toothed belts in my view is that they do not require to be under any great tension, so other than the drive forces they do not put any loads on the headstock bearings.

 

It should be possible to turn the existing teeth off the existing pulley, and either allow the new set to be a little undersize, or else fit on a  ring turned from a suitable piece of tube to bring it back up to the nominal size. With the big area available, loctite should be fine to hold such a ring in place.

 

regards

John

[TerrydParticipant @terryd72465]

Hi John,

 

When I was discussing the torque at the primary drive I was thinking of the starting torque.  The lathe does not have motor speed control so it is trying to start at full speed.  I don’t really know enough about the theory involved,  that’s for others to discuss.  I just feel that the toothed belts are there for a reason, it’s not an accident or an offhand decision to use this type of drive it is a deliberate design decision.  It would have been so much easier just to add another vee pulley to the cones if it didn’t matter. 

 

If Grizzly do the equivalent of the 10″ version of this lathe someone will surely supply the 8″ model being discussed here.  personally I think the way to go would be to research suppliers of the lathe rather than belts.  Saves a lot of work and possible expensive components if they could be located..

 

Regarding your idea of skimming the pulleys, excuse me if I seem thick, but did you mean that teeth for a new pulley could be cut when the new ring is in place to match a standard Belt?

 

Terry

[John OlsenParticipant @johnolsen79199]

Hi Terry,

 

Yes, I would agree with you that  it is not an accident that they have used this type of belt. The price of the belt itself is probably not much different between toothed and V, but the pulleys do tend to be dearer for the toothed one.

 

I was thinking it would be possible to fit a ring neatly in place and then cut the teeth to suit something standard. A bit like a ring gear on a car. Of course the motor end would have to be done too, which might be harder. If a supplier of the belts could be found that would actually be the way to go.

 

regards

John

[JasonBModerator @jasonb]

Some of the larger Emco machines use a toothed primary belt and its well know that these form the basis for a number of the far eastern machines.

 

“If Grizzly do the equivalent of the 10″ version of this lathe someone will surely supply the 8″ model being discussed here”

 

Back on the first page I linked to Quantum who do the belt drive DB8 clone, would be better contacting them to see if they can provide a spare.

[TerrydParticipant @terryd72465]

Hi Jason,

 

You’re probably right about the Quantum lathe, In fact they now supply them through Excel in Coventry who may be able to source the belt due to their connection with the company.

 

By the way I finally decided on the Warco WM280 VF but my garage rebuild has been held up by the weather (and inefficient builders appointed by the insurance company ). So I probably won’t be able to have it delivered until after Christmas, very Frustrating . 

 

I’ll console myself with the old adage that good things are worth waiting for.  I just wish that I could persuade myself of that. 

 

Regards

 

Terry

[Dinosaur EngineerParticipant @dinosaurengineer]

Maybe the toothed belt is used due to a small pulley being used  ( high torque at small radius) and the pulley wheel centres are close so that it’s difficult to provide enough “wrap around” for a ‘V’ belt. A friction belt would be better than a “geared” belt as it’s more likely to slip rather than cause mechanical damage. The equivalent ‘ v ‘ belt drive would probably need more space and/or a tensioning roller to increase the small pulley “wrap around” 

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