mandrel question

[jimr]

Is there any difference in diam. of mandrels between Berea and Craft supply? Not the Berea "B", the smaller ones. My Sierra bushings do not spin true. I have tried everything I can and still have the problem. BB even sent me a replacement set but there is still a wobble. There is a slight slop when they are on the mandrel. I only have the Craft supply 7mm mandrel and thought maybe it was a bit smaller than the berea. Anyone else have this problem with the Sierra bushings.

 

[pastorbill1952]

Jim I think there is a slight variation that was discussed once before. Try doing a search and be sure to check the archive box.

 

[vbatwork]

Hi Jim, yes there are slight differences in mandrels from the big three manufacturers. Some of the more experienced than I could probably provide some cross over as to what you can mix and match. Theres lots of discussion on that topic under various threads. As a rule of thumb I like, and a newbie [], I stay with BHW mandrels for BHW kits and have always had good luck. My BHW 'A' mandrel measures .246" if that helps you compare against your CSU unit. Best of luck!
HTH - John

 

[KC]

I have four Woodcraft mandrels, one new Berea, and a couple old Berea from my penmaking days years ago...and every set of Sierra bushings I've used (probably 6 sets) are loose on all the shafts...and it makes just enough 'out of round' to be noticeable.

It's not loose enough for a single layer of scotch tape. I tried painting a mandrel, and also spraying with lacquer to get a tighter fit, but the bushing ends up scraping the buildup away.

KC

 

[gerryr]

The sloppy Sierra bushing problem has been noted here more than once. Making a Sierra requires stopping on a very frequent basis and rotating the blanks on the mandrel. If you do that, you can make it round.

 

[Borg_B_Borg]

Using brass or stainless shims to correct for the looseness of the bushings is preferred to rotating the blanks during turning.

Steve

 

[Charlie in Garfield]

Hi All,
Got what you all might conder a dum sulation. Why not have a freind that has a metal leath make bushings to fit a 7mm. mandreal and turn the out side to the required demetion for the pen. ????
Just Charlie & Betsy

 

[jimr]

I read this forum daily and this is the first time I recall any mention of loose bushings for the sierra, but apparently it is a common problem. You would think Berea would make a correction. A loose bushing is not a very good recommendation for an outfit like that, but I guess they don't care.
I really like the pen but this may keep me from making any more. From everybodys comments I guess my first inclination to purchase a berea mandrel is not worth it. What if Berea sent me a "sloppy" mandrel.
Thanks for all your help

 

[woodbutcher]

I have several Berea mandrels and their bushings are loose. I now use bushings from Penn state. They are almost too tight at first but will loosen up just enough with patience. I still rotate my blanks 180 deg. Hope this helps,
Jim

 

[Randy_]

I have read about the problem with Sierra bushings; but was under the impression that it had been corrected??

As to your mandrel question, Berea says their "A" mandrel is 0.247" +0-0.002". The CSUSA mandrel is said to be 0.246" with no tolerance specified. A little shim stock should solve your problem.

Do you have any way of measuring the hole in your bushings? It would be interesting to know exactly how big the hole is. I've got set of unused Sierra bushings. Not sure if I can measure the hole accurately; but I will give it a whirl!!

 

[Randy_]

My Berea mandrel mikes at 0.2475" to 0.0248". The bushings fit snugly on a 1/4" drill bit. They seem to fit a bit more loosely on the mandrel than some of the bushings from PSI and CSUSA for other kits. I don't really know how closely bushings and a mandrel should fit?? Maybe Paul or another one of our machinists could comment on what we should expect to be a reasonable fit??