Duplex Toolpost Grinder

[Colin HeseltineParticipant @colinheseltine48622]

I  have had a Dupex Toolpost Grinder for several years but never really needed to use it.

I now need to very slightly reduce the diameter of a hardened 90 degree seatcutter.  I have  made and fitted guards for the wheel and the belts, ordered a new belt but am struggling to find a source for suitable grinding wheels.

The wheels need to be 3″ diameter (or 75mm), 1/2″  thick and with a bore of 1/2″.  I have managed to source some 1/4″ thick wheels but cannot find any 1/2″ thick.

A Midlands grinding wheel specialist can machine a 5″ one down to 3″ but will have a 2-3wk wait.  Does anyone have any ideas on sources or even have a spare wheel they have no use for.

It is a Model D22A running at 1100rpm.  Capacity is given as 3″ x 1/2″.  Would I be correct in thinking that I could go smaller, say to 2″ diameter, safely.

Many Thanks,

Colin

 

[noel shelleyParticipant @noelshelley55608]

1100 RPM ? Do you mean 11,000 RPM ? As for size of wheel, smaller I would say yes but check the wheel speed rating ! It will reduce your cutting speed though this may not matter to much for a simple one off.

You do not name the supplier for the altered wheel but if it’s who I think it may be I had some 8″ wheels from them that were so far out of balance that they were unusable, only spending another £200 on a wheel balancer and a lot of work made these wheels any use. Good luck. Noel.

[Colin HeseltineParticipant @colinheseltine48622]

The motor states 1100rpm.  Based on pulley diameters the spindle can run at 1500rpm max.  Supplier was DGS Abrasives.

Colin

[bernard towersParticipant @bernardtowers37738]

Try abtec for wheels

[BazyleParticipant @bazyle]

Does it have to be 3″? Die grinder wheels are smaller but more available.

[DiogenesParticipant @diogenes]

EDIT – overtaken by events –

1500 seems very slow for toolpost grinding?

[JohnFParticipant @johnf59703]

Colin, I have a small TP grinder, a Boxford Little Giant, no instructions but I do have instructions for a VERY similar Dunmore grinder — so similar I believe they may well be the same ?  If you want the instructions message mw.

Looking for info on yours there’s some info on lathes.co.uk but no mention anywhere of your model D22A ! there’re others and as Noel says the speed you state is far lower than you will need for a 3″ wheel and more so for a 2″ wheel.

I purchased wheels of mine from Midland Abrasives

John

 

[noel shelleyParticipant @noelshelley55608]

John has mentioned the company I dealt with. Are you sure it is a tool post grinder ? I would say that a 3″ wheel should run at 5000 +RPM. It is unlikely to cut properly at 1100 – 1500RPM.  Noel.

[JasonBModerator @jasonb]

Any chance someone has swapped the motor pulley at some time. Looking at other similar ones the motor pully is much larger than the spindle one so would give a 6 or 10 times speed increase.

[JohnF]

On JohnF Said:

[…]

Looking for info on yours there’s some info on lathes.co.uk but no mention anywhere of your model D22A ! […]

https://store.lathes.co.uk/model/d22a

MichaelG.

[Colin HeseltineParticipant @colinheseltine48622]

The pictures below show the grinder mounted on lathe and also the motor plate.

Currently no guards or belt fitted.

 

[noel shelleyParticipant @noelshelley55608]

The speeds mentioned put me in the mind it is NOT a grinder ? Those speeds are more appropriate to a milling attachment. Or the pulleys have been changed ? Noel.

[Colin HeseltineParticipant @colinheseltine48622]

Lathes.co.uk under toolpost grinders have a Duplex D22A listed and have manuals, but not seen any pictures to check on pulley sizes.

 

[Michael GilliganParticipant @michaelgilligan61133]

Can’t see that exact model here:

https://www.lathes.co.uk/duplex-toolpost-grinders/

But it certainly looks like there was a wide range of wheel sizes

MichaelG.

[Colin HeseltineParticipant @colinheseltine48622]

Im beginning to think the motor pulley has been changed to a much smaller one.  Am going to look at a manual I have located and see how much the wheel has to be scaled up to get the recommended speed.

[onionParticipant @onion]

Colin, with regard to a source of grindsrones may I suggest that Black and Decker used to sell  a 3×1/2×1/2 grindstone for use on a drill chuck arbour back in 60’s.  There are 2 on an auction site at the moment (one very expensive, the other given as metric size) I have looked for my virtually unused example for you to try but haven’t found its hiding place. I’m sure other forum members may have better luck.  The auction pictures of the items suggest around 5000 max rpm

 

Neil

[Michael Gilligan]

On Michael Gilligan Said:

On JohnF Said:

[…]

Looking for info on yours there’s some info on lathes.co.uk but no mention anywhere of your model D22A ! […]

https://store.lathes.co.uk/model/d22a

MichaelG.

Thank you Michael, I didn’t look in the store only the main archive here — https://www.lathes.co.uk/duplex-toolpost-grinders/#google_vignette

John

[Colin Heseltine]

On Colin Heseltine Said:

The motor states 1100rpm.  Based on pulley diameters the spindle can run at 1500rpm max.  Supplier was DGS Abrasives.

Colin

If, as should be on a grinder, the motor is a fixed speed induction motor, then 1100rpm seems a strange speed for 50hz. Is it possibly a 6 pole motor intended for 60hz. Definitely too slow as it stands.

[noel shelleyParticipant @noelshelley55608]

It appears to be a brushed motor, note the brush holders. I have a wolf tpg and it is also a brushed motor. Angle grinders and small high speed grinders seem to be brushed.  Noel.

[Clive Brown 1Participant @clivebrown1]

You’re correct, I’d not noticed the brush-holders.

[Kiwi BlokeParticipant @kiwibloke62605]

For what it’s worth, this late in the thread, here’s some info. from an old Duplex brochure. Sorry, obviously no help with wheel availability …

Model D22A.

Plain wheels: Ext. 3″ X 1/2″ X 1/2″; Int. 1″ X 1/2″ X 5/16″ (‘standard vitrified’)

Motor: Universal (DC or SP, commutator-type), 1/3 HP

Speeds: 6,000, 16,000 RPM

Unfortunately, the brochure pics don’t show the belt pulleys, but there doesn’t seem enough room in the belt guard for a large enough motor pulley to give the speed ratio required if the OP’s stated motor speed is correct.

Later production models were fitted with fully enclosed induction motors. The commutator motors were not intended for continuous use, but their duty cycle was not stated. Spindle bearings are oil-mist lubricated – a few drops of oil required ‘every few working hours’.

[Colin HeseltineParticipant @colinheseltine48622]

Kiwibloke,

Thanks for that speed info.  Currently waiting for a manual and some brochures.  Looks as though I need to make new motor pulley.  Need to do some calculations to work out the diameter.  I will keep the spindle pulley as is.

Should have a suitable stone and belt to drive in current form by end of week.  Hopefully this will enable me to do the current job as its only a case of reducing a diameter, finish is not critical.

Colin

 

 

 

[Kiwi BlokeParticipant @kiwibloke62605]

Colin, I just dug out my ancient, but little-used, Duplex D 27 (C). It is old enough to have a universal motor, like yours. There’s no motor plate per se, just a plate on the belt cover giving spindle speeds (6,000 & 16,000 RPM) and motor power (1/3 HP). A rough measurement of the heavily-crowned flat belt pulleys and a couple of sums gives the motor speed as between 10,000 and 11,500 RPM (approx.). It certainly screams… Probably not a good idea to run the motor unloaded!

[noel shelleyParticipant @noelshelley55608]

The figures given by Kiwi are inline with what I fancy some, including me would expect. The speed rather than being 1100RPM  is probably X10, this would make sense. A ratio of 1: .55 or 1: 1.45 . Noel.

[Colin HeseltineParticipant @colinheseltine48622]

I have now collected the new 3″ dia grinding wheel and the new belt.  I have also purchased one of the cheap digital laser rpm counters.

Initial check of the motor gave speed of 15633 at the motor pulley.  This gave something like 26000 high speed for use with an internal grinding spindle and 7144 for the low speed for external grinding.  Ideally I need to take a number of speed readings and average them out.

I could possibly accept that whoever stamped the motor plate missed a zero off and it should read 11000, in which case this would give a low speed of 6490 and a top speed of 15155 with the current pulleys.

At least it looks as though I have suitable speeds for the size of grinding wheels I will be using.

Cheers all.

Colin

 

 

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