The BSA A7-A10 Forum

Technical => A7 & A10 Engine => Topic started by: Bsa Nut on 26.08. 2018 18:00

Title: Timing side bush reaming
Post by: Bsa Nut on 26.08. 2018 18:00
Can anyone suggest a USA-based competent shop for final fitting of an A7 timing bush??
I'm tempted to try it, but I worry about holding the tolerance.
(I do have a vertical mill w/ DRO, but I am NOT a machinist.)
I realize the importance of this fitment.

Opinions/suggestions ?

-Luke
Title: Re: Timing side bush reaming
Post by: coater87 on 26.08. 2018 21:51
 Morries Place in Ringwood Illinois did mine.

 Ed did a good job.

 Lee
Title: Re: Timing side bush reaming
Post by: coater87 on 26.08. 2018 22:08
 PM sent Luke.
Title: Re: Timing side bush reaming
Post by: edboy on 27.08. 2018 11:06
in my opinion the expandible reamer is quicker and easier. buy or source the size of reamer and make a bush to fit the reamer shaft into the bearing outer fitted in the crankcase. these reamers are about a foot long and only take slight cuts into the bush material. cases should be tightened together when cutting, then try the fit after every cut. place the crank in a vice and drop the t/s case on. easy.
Title: Re: Timing side bush reaming
Post by: RichardL on 27.08. 2018 11:35
No debate with Coater87 about Morrie's Place, I'm sure Ed did a very good job. I happened to use Custom Engine Service of Aurora, IL because they are 50 miles closer to me. Probably less experience with this specific task for A7/10s (for all I know, mine could be the only one they've done), but a full-service automotive machine shop with crank grinding, line reaming, valve seats, etc.

Richard L.
Title: Re: Timing side bush reaming
Post by: BSA_54A10 on 28.08. 2018 09:09
We are about to make a dummy bearing to fit into the drive side bearing outer race with a hole for a pilot then use a piloted reamer to do the job.
When you consider the way these were done back in the 50's & 60's I rather think we all get a bad dose of space shuttle engineering for a pram.
Remember the original BSA factory service tool clamped onto the outside of the timing side case
Title: Re: Timing side bush reaming
Post by: JulianS on 28.08. 2018 10:15
...............and on an historic note the 1957 on steel backed bearings with the Vandervell insert were designed not to be reamed, this continued through the A50/A65 series.

Sorry the bulletin is a poor copy.
Title: Re: Timing side bush reaming
Post by: edboy on 28.08. 2018 11:24
the bsa bushes were probably a precision fit . even the best ones today will need reaming as they will not fit on the crank and as long as the blades are sharpe the finish is good. the bsa template is not much good for the expandible reamers available to buy. however you will have to make a bush for the reamer to slide in as the thimble is too inaccurate.
Title: Re: Timing side bush reaming
Post by: coater87 on 28.08. 2018 12:27
 I went through the same things. I have the ability to make the jigs and fixtures to do this work.

 It comes down to the finish you want on the TS bushing. I dont own, and I do not have access to a sunnen hone.

 I would certainly believe thats the quality of finish you want for a long lasting motor.

If you are going to race this and see its skynards innards every week, its not as important.

 Lee
Title: Re: Timing side bush reaming
Post by: Peter Gee on 31.08. 2018 20:16
Hi, I have just gone thru 6 moths of research and thought about this. And done it.

1) Replace the steel backed bush with a Kebblewhite one piece phosphor bronze.

2) You MUST have the ovality taken off the  timing side  side crank bearing journal BEFORE you attempt bush sizing. You need to know how oval or worn it is under standard. There is no need to have it ground to a specific -010", -020" etc..... just whatever it takes to  eliminate any ovality in the journal.

3) You then choose the correct size replacement bush.. i.e. if you have .006" ovality, you choose bush +0.010". If you have 0.0012 ovalility or undersize, you choose bush +0.020" etc and you will BORE DOWN to your custom regrind size +0.0005" you have determined.

4) You CAN use a milling table with the correct equipment  (A boring head)  to vertically  "LINE BORE" an 107/A10 timing side bush  in perfect sizing without using more than the  Drive Side  BEARING RACE as the datum surface. It's an  unusual but clever  method fully explained and shown by a typical old time British machinist on Youtube if you follow this INGENIOUS link https://www.youtube.com/watch?v=Lg5AcTqq_9g (https://www.youtube.com/watch?v=Lg5AcTqq_9g)

5) Otherwise you will have to use a machine shop to LINE BORE your bush horizontally  using a mandrel /pilotfixture they will have to make up to align the drive and timing side and use the drive side bearing face as a datum..you can't use the DS bearing, because its a roller  bearing and will come out of the case as the line border device moves inward! If it was a roller ball grooved bearing, like  Triumph T100s, this would be no problem.

6) I  am very wary how hand reaming will work out well, unless you had the special  sliding reamer BSA used to use ( and their dealers) which passes thru the drive side  or else the reamer which used a special engine plate which affixed to the timing side ...in any case brass and bronze do not like being reamed and chattering/gouging  may happen, even if you had these tools unless you were experienced in reaming..

Please contact me if you wish to have the data for the various standard sizes of BUSH and JOURNAL for the A7. It's available in chart form online and you may already have it.

I had this job done after very careful consideration and achieved the 0.0005"~0.0001 clearance and perfect crankshaft SPIN after bolting up the cases with the AG engineering method.

If this job is not done right, problems multiply and cause extensive strip downs and re-dos. Get it right for your peace of mind!
Title: Re: Timing side bush reaming
Post by: edboy on 01.09. 2018 02:18
well peter i m sure you know whats best for your engine and what you state is what you have experienced. but you state lots of unnecessary hurdles in my opinion. for me time is money and the method i use takes about an hour per bush. if i was to go down the machine shop route i would opt for the needle roller conversion myself as it would probably be cheaper.
Title: Re: Timing side bush reaming
Post by: Peter Gee on 01.09. 2018 07:17
Dear Edboy, ..I wrote that thinking you had mentioned you had a milling table and there is a method as noted, using only that to accurately line bore a TS bush. In olden days everyone got by with reamers but the only pics I have seen of the BSA factory reamer it looked special.

(https://www.a7a10.net/forum/index.php?action=dlattach;topic=567.0;attach=1030)

Title: Re: Timing side bush reaming
Post by: coater87 on 01.09. 2018 13:28
 Thats  a piloted reamer.

 Everybody used to make those, now they are a little harder to get.

 There are lots of ways to do everything. That method there would be way down on my list of ways to do a T/S bush, but thats just me.

 Lee



 
Title: Re: Timing side bush reaming
Post by: Peter Gee on 01.09. 2018 18:31
Thanks Coater...did you see the AG Engineering you tube video I mentioned above? Novel way and seems to work fine.
Title: Re: Timing side bush reaming
Post by: edboy on 01.09. 2018 20:36
that reamer is exactly what i m using, but with a  machined sliding bush that fits the inner race dimensions. not the thimble. i like the method as its quick and easy. no more long winter rebuilds for me.
Title: Re: Timing side bush reaming
Post by: Bsa Nut on 05.09. 2018 05:52
Thanks for all the replies...
I was away at Davenport Swap Meet/Races, so I was out most weekend.

I've convinced myself to give it a shot here at home.
I've watched the above mentioned videos about line boring on the mill,
and I have the equipment.
I wondered about the reamers also. I have access to those as well.
I thought it possible to set up over the roller bearing side, then
set up the reamer in a collet, remove the top case, and ream the bush. (Statically only, not powered.)
I also have a boring bar, but I worry about the finish, as opposed to the reamer.
The shops Ive contacted either gave no reply, or were much higher in cost than seems necessary.
I'll keep you posted on the results...
even if it takes me a few bushes, its cheaper.
And its learning part that makes it fun.
Thanks again.


Title: Re: Timing side bush reaming
Post by: kiwipom on 05.09. 2018 07:08
in my opinion the expandible reamer is quicker and easier. buy or source the size of reamer and make a bush to fit the reamer shaft into the bearing outer fitted in the crankcase. these reamers are about a foot long and only take slight cuts into the bush material. cases should be tightened together when cutting, then try the fit after every cut. place the crank in a vice and drop the t/s case on. easy.
Yeah this is the way I would do it after watching the long U Tube video. I am sure BSA did it this way and obviously a lot quicker as the crank would be the same size every time, good luck, cheers
Title: Re: Timing side bush reaming
Post by: beezermacc on 05.09. 2018 07:34
in my opinion the expandible reamer is quicker and easier. buy or source the size of reamer and make a bush to fit the reamer shaft into the bearing outer fitted in the crankcase. these reamers are about a foot long and only take slight cuts into the bush material. cases should be tightened together when cutting, then try the fit after every cut. place the crank in a vice and drop the t/s case on. easy.
Yeah this is the way I would do it after watching the long U Tube video. I am sure BSA did it this way and obviously a lot quicker as the crank would be the same size every time, good luck, cheers
I agree with the above. I've done quite a few of these with a hand reamer and always had good results. I keep the crankcases tightened up all the way through the process and try the crank in the bush on the outside. This works fine if you've just had the journal skimmed so there is no shoulder on the journal. So not necessary to split the cases every cut. I do a final fit with the crank in the cases just to make sure there are no tight spots.