17-09-2020, 04:27 PM
James, no doubt others know more than I but here's my tuppence:
I wouldn't immerse it in water; A7 crankcases are quite resilient and you can happily play a blow lamp on it around the bearing housing as long as you don't go crazy (massive heat or stay on one spot too long). This will easily bring it up to suitable temperature without negative consequences (such as filling things with water). Heat will certainly help.
Aim your drift at the inner race only. You will need something long and thin, I have managed it with a long wire tent peg before though ideally something slightly stiffer. I guess in an ideal world it would have a 'soft' bearing end - at least try to avoid gouging the casing too badly and don't smack the bearing retaining lip!!
Lots of small taps rather than great big wallops, doing your best to move the drift around the race (I know, there isn't much scope) to avoid canting it sideways. Then it is just perseverance.
Place something soft under the front to catch the front race when it falls out! They are often re-usable but best not dropped on concrete floors from a height.
You may find they are actually not that tight at all, but don't be tempted to put them back in with Loctite. It is mainly the axial clamping force (if anything) that stops them spinning in the housing.
Oh yes, and keep the rear bearing in to hold the shaft straight while you drift, you don't want the crankshaft twisting them into the case.
I wouldn't immerse it in water; A7 crankcases are quite resilient and you can happily play a blow lamp on it around the bearing housing as long as you don't go crazy (massive heat or stay on one spot too long). This will easily bring it up to suitable temperature without negative consequences (such as filling things with water). Heat will certainly help.
Aim your drift at the inner race only. You will need something long and thin, I have managed it with a long wire tent peg before though ideally something slightly stiffer. I guess in an ideal world it would have a 'soft' bearing end - at least try to avoid gouging the casing too badly and don't smack the bearing retaining lip!!
Lots of small taps rather than great big wallops, doing your best to move the drift around the race (I know, there isn't much scope) to avoid canting it sideways. Then it is just perseverance.
Place something soft under the front to catch the front race when it falls out! They are often re-usable but best not dropped on concrete floors from a height.
You may find they are actually not that tight at all, but don't be tempted to put them back in with Loctite. It is mainly the axial clamping force (if anything) that stops them spinning in the housing.
Oh yes, and keep the rear bearing in to hold the shaft straight while you drift, you don't want the crankshaft twisting them into the case.