Bridgeport Series 1 Varidisc Head Bushes/Bearings

[_Paul_Participant @_paul_]

[_Paul_Participant @_paul_]

My 1988 Varidisc has a noisy head so it's time to repair it does anyone have dimensions for the plastic (Delrin?) bushes & keys that I need to replace? as I intend to make my own, I know I can buy them ($54 from USA vendors) but here in rip off Britain the only UK retailer of aftermarket bushes charges £19 for one bush.

I understand the Varidisc roller bearings are pretty much standard items but dont seem to have standard part numbers if anyone has the "real" bearing numbers I would be grateful.

I have read quite a few articles on the subject but none give definitive dimensions sadly.

Any and all help appreciated.

Paul

[KWILParticipant @kwil]

Describe the bearings you want by location within the head, I have the parts breakdown listings.

[Clive FosterParticipant @clivefoster55965]

Paul

Dimensions vary according to motor power and year the head was made. I made a new set to replace the turquoise bushes in my mid 1970's head with 1.5 HP motor. If yours is same power and has same colour bushes I can send you a PDF of the drawings. Note that the turquoise bushes appear to have been moulded in place then bored as there is a retention ridge halfway along fitting into a mating recess in the pulley which makes life complicated when going for an exact fit. Mine fit and work fine using loctite to retain them but I suspect the ridge is a little undersize in its groove. Some guessing involved in reverse engineering as mine came out is several parts and I never did find them all.

Later ones than mine have simple plain bushes which are easily reverse engineered. These are the ones the US kits are for. Sorry I don't know what year the change occurred, i think it likely that you have plain bushes.

Clive

[KWILParticipant @kwil]

Yes the turquoise bushes are moulded in place and are not replaceable. Bearing associated with front varidisc were Fafnir PM9110NPP, 9110 series bearings are 80x50x16 PP = 2RS

[_Paul_Participant @_paul_]

Thanks gents,

KWIL, I've not stripped it yet but I think it's plastic bush on the varidisc thats gone/going but what I intend to do once it is in bits is change the roller bearings on top of the Varidisc actuating arm and the motor plastic bushes & key:

Variable Speed Top Housing

Ball Bearings

OEM p/n: 1180253, 11170262 ?

OEM p/n: 11180252

Plastic Insert-Front Varidisk (2 Req)

P/N: HQT1126

Plastic Insert 2HP (2 Req)

OEM p/n: 1182126, 11182126

Clive, yes please to your PDF which Loctite did you use?

Regards

Paul

[_Paul_Participant @_paul_]

Thanks KWIL thats exactly what I need

[John Stevenson 1Participant @johnstevenson1]

Depends whether it was a Monday morning machine or a Friday afternoon machine

 

Seriously though it does depend a lot on models, horsepower, where made i.e. the licensed models etc.

Some are on 24mm motor shaft size, some on 28mm shaft size but of those 28mm ones some are on 7mm wide keys and some on 8mm wide keys and to muddy the waters still further some have different sized tail bearings.

 

When they wear bad they wreck the motor shaft. Typical varispeed motor rotor.

 

Top diameter of 29mm is OK as this is the fixed sheave but the 28mm diameter bit where the sliding sheave runs is toast and a new rotor is about £400.

 

Soooooooooooo.

 

 

Gobo some weld on it, don't talk to me about distorsion, and wait for the weld to dry.

 

[Note to self : Self, – remember to pick up by the other end ]

 

Once the weld has dried this is lurking under all the slag and crap.

 

 

Two hours, start to finish and another bridgeport lives to bend another day.

 

John S. [ who much preferes step speed models with a VFD. ]

 

[ EDIT ] BTW I this is not uncommon, I probably do between 15 and 20 per year.

Edited By John Stevenson on 27/09/2012 17:31:30

[Sub MandrelParticipant @submandrel]

Lovely job, John.

Neil

[Jeff DaymanParticipant @jeffdayman43397]

I sure hope there's no carbon migration at the weld zone inside those shafts. Any preheat used before welding? Are you using a high purity rod?

JD

[John Stevenson 1Participant @johnstevenson1]

In keeping with original Bridgeport design only the best high tensile / high purity licorice is used.

In all fairness it must be decent licorice because been doing these for about 15 years now.

Mind you these are easy compared to some jobs. Take a look at this.

Seriously, this got sent down and can you straighten the rotor and weld the housing ?

Turns out this motor drove a hydraulic pump on a largish press and stuck out the side of the press. Whilst they were installing a new press they lowered it onto the motor !!

Believe it or not the rotor repaired part straighten and part welded and turned back to size. Gave up on the housing, too many bits missing. Hoever if you study it the housing consistes of 5 different profiles so got these laser cut out of 10mm plate , welded up and machined back to size.

The press was running the following day.

John S.

[Clive FosterParticipant @clivefoster55965]

Paul

No problem to send the PDF drawing. Where do I send it?

Do remember to check it against your machine before following as its amended but untested. I corrected the errors in the original reverse engineered drawing to match what actually fitted but I haven't made another set to check. Making is a horrible job due to the thin wall and uncertainty as to how much the delrin will spring when you make them. Can't make turquoise style ones thick and bore out after fitting because they need to be very flexi to get in.

Pictures of the making process too if you want. Was going to write it up for MEW but first draft was so bad …..

Dunno what grade of loctite I used to stick them in with.  Probably one of the high strength ones (green?).

Clive

Edited By Clive Foster on 27/09/2012 22:00:59

[Jeff DaymanParticipant @jeffdayman43397]

John Stevenson-

I don't understand your "licorice" reference. My understanding is that Bridgeport made all their shafting from either SAE 1020 or 1045 plain carbon steel. These types of steel are subject to carbon migration during some types of electric welding, which can result in a layer of zero strength graphite at the weld boundary, unless measures are taken to prevent it, hence my comments.

JD

[John Stevenson 1Participant @johnstevenson1]

Jeff,

It's only when you get on to quite large or special motors that they use anything other than basic mild steel.

A lot of the smaller motors even use leaded steel.

The licorice reference was made that although Bridgeports have a large following they are a lot like Myford in that the machines is not as robust as the name. There are a lot better out there and usually for less money.

[_Paul_Participant @_paul_]

@ Clive PM sent

Many Thanks

Paul

[_Paul_Participant @_paul_]

@ Sir John,

So if my motor shaft is knackered I could MAG it up? if it's not being too inquisitive what do you weld them up with?

Regards

Paul

[James BParticipant @jamesb]

Hi All,

I know this is an old thread, but I think all relevant.

Regarding the replacement black Delrin bushes in the Varidisk assemblies – could I ask what glue people have used to replace the bushing?

Thanks,

James

[Clive FosterParticipant @clivefoster55965]

James

General recommendation is a high strength cyanoacrylate with a suitable primer to modify the Delrin surface and promote adhesion. For example :- **LINK** .

I've done well enough using ordinary cyanoacrylates and high strength loctite to retain simple bushes after lightly abrading the Delrin surface first. My shop made Delrin replacements for the turquoise "moulded in place" Varidisk bushings appear to be holding in there just fine. 6 years and counting! I doubt that it would be strong enough to hold a stressed joint though.

Maybe this stuff **LINK**. is the real deal. Says its for Delrin on the blurb. But being an epoxy I wonder if the joint line may be too thick for Varidisk bush retention.

Clive.

Edited By Clive Foster on 27/03/2018 09:28:39

[KWILParticipant @kwil]

You might like to consider **LINK**

I have used in on delrin in a car application.

[MuzzerParticipant @muzzer]

The key to bonding CA adhesives to "shiny" plastics is the polyolefin primer (aka "adhesion promoter" ). That Bondloc stuff (KWIL) and the "POP" product mentioned in the Permabond site appear to use such a primer. Note that the page for the POP product on the crap Permabond site is broken….

Google "polyolefin primer" and you get loads of hits, including the Loctite 770, Permabond POP and others. It's useful stuff to have handy, as it allows your existing selection of CA adhesives to be used on shiny plastics in applications such as this.

Murray

Edited By Muzzer on 27/03/2018 13:23:59

[James BParticipant @jamesb]

Thanks for all those details – plastics and adhesives is not my strong point, so useful reading. Hopefully I will be able to do it without glueing myself to anything….

[mark costello 1Participant @markcostello1]

It's nice to see John Stevenson still giving advice.

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