Established 1993. The only club dedicated to all types of vintage garden tools and machinery

 
.....Find the NEW website and machinery forums at www.vhgmc.co.uk
 
  Active TopicsActive Topics  Display List of Forum MembersMemberlist  CalendarCalendar  Search The ForumSearch  HelpHelp
  RegisterRegister  LoginLogin
Projects
 VHGMC ForumsThe Main Forum AreaProjects
Message Icon Topic: howard gem Bearings Post Reply Post New Topic
Author Message
plonker
Forum Member
Forum Member
Avatar

Joined: 15 Nov 2009
Online Status: Offline
Posts: 528
Quote plonker Replybullet Topic: howard gem Bearings
    Posted: 01 Sep 2013 at 11:09pm
having stripped the chain drive backplate and removed the two bearings, I wonder if a Gem owner can help identify the main drive sprocket bearing? the one on the Jackshaft sprocket is easy it is 1" bore x 2.5" outer diameter, and is bog standard, the other one on the main rotor drive sprocket is a bit of a puzzle, the shaft measures 1.186" which is not 1 3/16" that I expected, and the outer diameter seems to be 72.5mm it is marked as a Hoffman 330, does anyone know if this is still available? I know they are supposed to be a press fit, but I am not sure of the tolerences, any ideas out there? I am sure that lots of Gem owners must have replaced this bearing.
plonker
IP IP Logged
wristpin
Forum Member
Forum Member
Avatar

Joined: 20 Apr 2012
Location: United Kingdom
Online Status: Offline
Posts: 853
Quote wristpin Replybullet Posted: 01 Sep 2013 at 11:29pm
My guess is that any decent bearing factor will recognise that Hoffman number. If I remember I'll ring my usual supplier and ask in the morning.

Monday
My man says that it is a metric size 6306
IP IP Logged
Quilla
New Member
New Member
Avatar

Joined: 01 Sep 2013
Location: Australia
Online Status: Offline
Posts: 6
Quote Quilla Replybullet Posted: 02 Sep 2013 at 2:07pm
 Use a double shielded bearing so the oil in the chain case will not get into the roror clutch and make it slip.I fit the oil seal as well with a smear of grease  .
IP IP Logged
plonker
Forum Member
Forum Member
Avatar

Joined: 15 Nov 2009
Online Status: Offline
Posts: 528
Quote plonker Replybullet Posted: 02 Sep 2013 at 9:59pm
Wristpin, thank you, that is interesting, wonder why they chose Imperial for the jackshaft bearing and metric for the main drive sprocket? Quilla, thank you, I will, depending on what bearing is available, I thought that "Gem" users must have changed these bearings, perhaps they are all away on Holiday!
plonker
IP IP Logged
wristpin
Forum Member
Forum Member
Avatar

Joined: 20 Apr 2012
Location: United Kingdom
Online Status: Offline
Posts: 853
Quote wristpin Replybullet Posted: 03 Sep 2013 at 1:32am
Originally posted by plonker

Wristpin, thank you, that is interesting, wonder why they chose Imperial for the jackshaft bearing and metric for the main drive sprocket? Quilla, thank you, I will, depending on what bearing is available, I thought that "Gem" users must have changed these bearings, perhaps they are all away on Holiday!


No idea why they should have chosen metric for that bearing, seems totally "out of period" but my guy is usually right about these things!
IP IP Logged
enginear
Forum Member
Forum Member


Joined: 12 Jul 2010
Online Status: Offline
Posts: 626
Quote enginear Replybullet Posted: 03 Sep 2013 at 8:05pm
Hoffman bearing size is 30x72x19 as stated that's a 6306
simple
IP IP Logged
wristpin
Forum Member
Forum Member
Avatar

Joined: 20 Apr 2012
Location: United Kingdom
Online Status: Offline
Posts: 853
Quote wristpin Replybullet Posted: 03 Sep 2013 at 9:29pm
Originally posted by enginear

Hoffman bearing size is 30x72x19 as stated that's a 6306


Just to add a bit more to that, with many but not all, metric bearings if you multiply the last digit by 5 you get the inner diameter eg 620x 5 =30mm!
IP IP Logged
plonker
Forum Member
Forum Member
Avatar

Joined: 15 Nov 2009
Online Status: Offline
Posts: 528
Quote plonker Replybullet Posted: 03 Sep 2013 at 10:08pm
Thanks Chaps, that is just what I wanted, I got both bearings out with a Birmingham Screwdriver and an Iron bar, but that size gives an interference fit of about five thou. on the shaft, looks like I will have to pay a man money to press the new bearings in! still, cant win em all!
plonker
IP IP Logged
wristpin
Forum Member
Forum Member
Avatar

Joined: 20 Apr 2012
Location: United Kingdom
Online Status: Offline
Posts: 853
Quote wristpin Replybullet Posted: 03 Sep 2013 at 10:12pm
Originally posted by plonker

Thanks Chaps, that is just what I wanted, I got both bearings out with a Birmingham Screwdriver and an Iron bar, but that size gives an interference fit of about five thou. on the shaft, looks like I will have to pay a man money to press the new bearings in! still, cant win em all!


Can you deep freeze the shaft and warm the bearing in oil or won't the assembly allow that?
IP IP Logged
plonker
Forum Member
Forum Member
Avatar

Joined: 15 Nov 2009
Online Status: Offline
Posts: 528
Quote plonker Replybullet Posted: 03 Sep 2013 at 10:33pm
Yes, I was thinking of something like that, but the outside of the bearing is a very tight fit in the housing, so I was thinking of the reverse, freezing the bearing, and warming up the backplate housing to press it in, then warming up the bearing and freezing the shaft as you say, I will try it all before I admit defeat and go cap in hand to the local engineers.!
plonker
IP IP Logged
hitchinsm
Forum Member
Forum Member
Avatar

Joined: 22 Nov 2012
Online Status: Offline
Posts: 51
Quote hitchinsm Replybullet Posted: 12 Sep 2013 at 3:37pm
If you live anywhere near the West Midland you can pop in to us and I can press the bearing in for you.
Regards Mike
IP IP Logged
plonker
Forum Member
Forum Member
Avatar

Joined: 15 Nov 2009
Online Status: Offline
Posts: 528
Quote plonker Replybullet Posted: 13 Sep 2013 at 12:42am
That is a very kind offer, but they arrived yesterday and they are now both in, I froze the imperial bearing for the jackshaft and warmed up the housing and it went in with a copper hammer and a brass drift, same with the main sprocket bearing (6306) except I froze the sprocket and drive shaft and warmed up the bearing, it drifted on to the shaft ok, I would mention that the collar that fits over the drive shaft splines was quite badly rusted, I turned it down in the lathe to 1 7/16" from its original 1 1/2" and bought an oil seal to match, one observation, it took some brute force to get the main 6306 bearing out, but to my surprise the new one fits in quite easily, just waiting now for the rotor clutch to be returned, and I can put it all back together.
plonker
IP IP Logged
Post Reply Post New Topic
Printable version Printable version

Forum Jump
You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot delete your posts in this forum
You cannot edit your posts in this forum
You cannot create polls in this forum
You cannot vote in polls in this forum



This page was generated in 0.063 seconds.