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Calling all Startrite Mercury drill owners - opinion on noise

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not done it yet24/11/2020 07:12:15
5382 forum posts
20 photos

OP stated, earlier, that a pulley is not running concentric? I would be further investigating that line of enquiry if I was a sleuth looking for a motive... the belt ‘bump’ will be a relatively low frequency, while the pully would create a much higher frequency of oscillation.

Alistair Robertson 124/11/2020 09:45:22
124 forum posts
6 photos

Knocking splines are very common on basic pillar drills.

We used to have a French built drill and it had a very clever split sort of key that kept the splines in contact at all times with very short and stiff coil springs maintaining the contact. It was impossible to "clunk" the splines so to speak.

A good quality notched belt is a great asset to smooth running. Use lab quality belts but sit down before you get the price. 10 times the cost of a standard belt if you can get it in the right size!

Graeme Durant 124/11/2020 17:17:40
26 forum posts

Many thanks Chaps - more food for thought.

I did for a while try and use a little strip of shim stock in the motor pulley bore to try and correct for the runout, but struggled and so moved on. What you say however makes sense - I will investigate further on that score.

Notched belts are something I wondered about, as I'd read good things about them in the past. Useful to know they can help with smooth running. I had a quick look and it seems I can source a Gates one in the correct size and section for less than £10 plus postage. Not sure it equates to your "lab quality" recommendation - but if it would help, it doesn't seem too painful a price.

Alistair Robertson 124/11/2020 17:57:26
124 forum posts
6 photos

Gates notched belts are usually very good and will be an improvment on non-notched type.

I replaced the standard belts on a new Warco drill I bought (for my home workshop) with notched belts and it transformed the smoothness.

I used to pay about £75 for one 800mm long belt for a test machine and 24mm x 5 meter belts were several £1000's each and we needed 5 matched belts at a time!!

Graeme Durant 125/11/2020 13:38:01
26 forum posts

So I parked the idea of changing the motor for a while, and had a look last night at the motor pulley concentricity. My DTI tells me it is 0.25mm out of true, and the "high spot" is in line with the single grub screw fixing. It clearly pushes the pulley off centre, due to a little slackness in the fit of the bore.

How to improve this? I stuck a small strip of self adhesive aluminium tape to the motor shaft, opposite the keyway where the grub screw bears. It had a thickness of roughly half the error.

It took a bit of persuasion for the pulley to go back on, but it did in the end. Tightening the grub screw, and re-measuring the run out, it had been more than halved to 0.1mm.

Running the machine, the belt still oscillates, but I could be convinced it is better! I tried all the pulley ratios, and a couple were actually quiet and oscillation free. So maybe this is one of the sources of the problem. It would be great to get the runout down by some more, but I'm not sure how best to achieve that. Adding more shim would make it very hard to get the pulley back on the shaft. And it doesn't feel worthwhile reboring the pulley - after all, I don't think it is not concentric - it's just 0.2mm oversize.

Any suggestions would be most welcome!

Edited By Graeme Durant 1 on 25/11/2020 13:39:12

Graeme Durant 125/11/2020 13:44:53
26 forum posts

On a related note - I am now wondering whether I am using the right vee belt profile. The one my second hand machine came fitted with is a "3V", which appears to be a narrow wedge belt. I replaced it a few years back with an "SPZ" wedge belt, which I seem to remember was touted as being an equivalent. Certainly their dimensions are close - though not identical.

But my question is - are these the right choice? Could it need a classic Z type belt profile? They are less tall in profile, so would presumably behave slightly differently in the pulley. I was just copying the original I had, but can't find any technical sources online to say what the manufacturer fitted. And right now, I feel I need to fit the right type of belt to try and eliminate my oscillation issues.

Any guidance from Mercury owners - without oscillation or noise problems - would therefore be welcome!

KWIL25/11/2020 15:27:46
3334 forum posts
63 photos

I bought my Startrite Mercury Floor model new some 30 years ago and it is still as good as new.

Over the years I too have changed bearings and Item 45 on the parts list, an O ring No 114.

As I recall this O ring did appear to quieten the spline chatter when unloaded, but does need to be done again! The O ring is located below the top bearing pair (6005 2RS) and sits around the splines.

The 5 speed belt is noted as V-belt A400 (Startrite part no.)

Clive Brown 125/11/2020 16:28:17
591 forum posts
23 photos

I am not a Startrite owner but I'm surprised that you use an SPZ belt which I thought is a metric specification and therefore rather unusual on an elderly UK made machine. Even a "Z" section is uncommon in my experience as most machinery of that era seems to use the heavier "A" section, which is 1/2" in width.

How wide is the top of the pulley grooves on your drill?

Edited By Clive Brown 1 on 25/11/2020 16:28:55

Graeme Durant 125/11/2020 19:57:46
26 forum posts

Mmmm, all very interesting - seems like a few things coming out today!

First the O-ring. Looking at the parts diagram I found online, item 45 seems to pushed onto the splines, on top of the collar that in turn sits against the upper bearing of the quill. Is that about right? Then when the quill is in the resting position, this O-ring may well contact the pulley bearings, and maybe damp any spline movement?

If my assumptions above are right then my response would be - wot O-ring?! My machine has no O-ring there! So maybe something that needs to be remedied. An essential - and easy - addition to my noisy machine!

Secoind, the belt. I measured the top of the pulley grooves - it's around 9mm. I found an old A-section belt and held it in the groove, but it barely went into the groove. So it doesn't look to me like it's an A section. Maybe mne is a later model which went to a Z or whatever? KWIL - when you mentioned an A400, what did you mean by that? Please pardon my ignorance if it's obvious to everyone else!

KWIL25/11/2020 20:06:56
3334 forum posts
63 photos


Just popped into the w0rkshop for you, mine is a Fenner SPZ 1010, just fills the pulley and is original belt.



Edited By KWIL on 25/11/2020 20:07:16

Graeme Durant 125/11/2020 20:12:46
26 forum posts

Many thanks KWIL. SPZ 1010 is what I'm using currently - so that's extremely useful to know. Mine is a Medway - so a budget one I think - and does have a bump at the join, which I wonder might not be helping my belt oscillations. Maybe time for an upgrade....

KWIL25/11/2020 22:05:06
3334 forum posts
63 photos

Bumps at a join, well where the wrap ends is never a good thing.

Graeme Durant 125/11/2020 22:16:31
26 forum posts

So is a bump an indication of a lower grade belt? Any suggestions on brands to go for would be useful - I can't find a Fenner at any kind of reasonable price!

Also, any thoughts on choosing a cogged or notched belt? Just looking for ways to reduce the opportunity for belt oscillation - as I have currently.

Dennis R25/11/2020 22:37:46
60 forum posts
15 photos

Just checked my floor standing model, pullies 9mm at top and belt fills groove, belt is a Picador Z995.

Belt has been in service for at least 20 years and no problems.


Graeme Durant 125/11/2020 23:48:44
26 forum posts

Many thanks Dennis - more proof that this is a "Z" type belt, of around the 1m length.

I'm currently planning on ordering a notched SPZ 1010 or similar tomorrow, so hopefully I can try it at the weekend. My hope is that a better quality belt than the one I have - with the added advantage of the notches (as described by earlier posters) will help damp my belt oscillations. That plus the newly discovered missing O-ring, may just fix my noise issues.....

Graeme Durant 113/12/2020 11:30:34
26 forum posts

I just wanted to follow up with my conclusions, and also thank everyone that helped with their thoughts and feedback. There's nothing worse than a thread in a forum that doesn't tell you the ending, especially when you are looking for help and find what seems to be the answer - but doesn't give you the punchline!

Either way, my Startrite Mercury is all back together now, and much quieter than when I started. The changes I made were;

  • Replaced the motor bearings - not sure if that made much difference, but they seemed a bit gritty and were not expensive. The originals were also open bearings, so I replaced with something to add a little protection against dust ingress.
  • Stripped the spindle (which was not as difficult as I'd thought it might be), cleaned the old grease out of the thrust bearings, re-greased, and re-assembled. This also eliminated a tiny bit of vertical play, which may or may not have been a contributing factor to the noise.
  • Added the missing O-ring identified by KWIL in the thread above.
  • Greased the splines - these were dry from the outset.
  • Replaced the belt with a good quality notched type. It certainly has no bumps in it like the one it replaces!

The noises I had at the start were I believe from the spline rattling, but may have been a combination from other sources too. Now these have disappeared. My belief is that the main remedy was the new belt, and getting the tension right. Too tight and it oscillates, and the noises come back as the spines pick up the speed variations. Looser seems to be the order of the day. And since the notched belt has "raw" rubber sides, it grips much better on the pulleys, and so doesn't need to be drawn so tight to avoid slipping.

I did have high hopes for the O-ring helping too, but for me it seemed to make no difference. I must confess I'm not sure what it is supposed to achieve, sitting where it does - but it does no harm, and is supposed t be there looking at the exploded diagrams!

Anyway, I think I'll live with it for a while and use it in anger and see how it goes. Hopefully the improvements are permanent! But it certainly sounds much smoother and quieter - which was my intention. All in all a good result!


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