Spindle swap

My drill a Sealey GDM30A has developed an unacceptable run out. Measuring this with the dial gauge suggests it's as much as 0.2 mm which is far too high and the drill really can't be used like this.  Removing the chuck and checking the tapers showed that most of this run out was due to wear and damage inside the chuck taper itself. Simply replacing the chuck should therefore fix the problem. Unfortunately this particular drill has a Jacobs 21/2 taper on the spindle, requiring a Jacobs 2.5 chuck and manufacture of these ceased some 70 years ago- spares haven't been available since the 60's.  

Date plate on my existing drill- yes it really is a 21/2JT chuck fitting even though many suppliers have never heard of it and assumed I didn't know what I was talking about!.

There are a few possible solutions to this problem- from quick and dirty to thorough and  involved! The modern version of this drill is the  SDM30 by Sealey which is fitted with a B16 taper compatible with many modern chucks. It seemed to me the most effective solution would be to replace the spindle with the B16 spindle from that model.

Having contacted the Sealey Technical advice line it seemed that the swap would be straight forward and the replacement spindle readily obtained. I therefore purchased the new Sealey spindle and set about dismantling the drill (see below) in order to commence the rebuild. Unfortunately this advice turned out to be incorrect and there were complications yet to arise.

New spindle from Sealey with 2MT chuck attachment.

The main problem with this approach was that I had intended to simply replace the spindle, reusing the existing upper spindle sleeve so that the pulley block and its mounting would be unaffected. Sadly, the new spindle will not fit into my existing GDM30A upper spindle sleeve because the new spindle has a square drive section and the original a hexagonal. You can see this in the pictures of the dismantled components below.

Looking inside the existing spindle sleeve and the spindle drive profile- GDM30a drill

Square drive section from the SDM30 drill spindle will not fit inside the GDM30 spindle sleeve. 

However the new spindle from the SDM30 has a squared  drive which will not fit inside the upper spindle sleeve from my old drill. I will therefore need a new spindle sleeve and its bearing mounting systems as well. Sadly it gets worse because the new spindle sleeve has a different pulley block attachment; instead of the taper used by the GDM30a, the new sleeve is cylindrical and mounts the pulley block using a grub screw- I need therefore to either replace the pulley block (new blocks are aluminium) or bore out the old one removing the taper and  fix it to the new spindle sleeve with a grub screw. Although this is irritating new parts were on special offer and relatively cheap so I tried both approaches. Overall the modifications should be well worth it to obtain a more modern drill. 

As mentioned above, I had already dismantled the drill ( see below) and so for all this time I had been without a drill and therefore I had to consider other, less satisfactory solutions. Since the existing spindle wasn't bent it should be possible to use it provided I could find some way of mounting a new chuck firmly and true to rotation. 

Taper adjustment 

A little research showed that the obsolete JT2½ dimensions are quite close to the more modern 6MT.  I can obtain a 16mm 6MT keyed chuck fairly cheaply. I found that this would mate with the spindle taper without modification but the fit wasn't great-the spindle would only penetrate about half way into the chuck and much of the taper surface was not engaged. Short of having the taper reground commercially,  the only course open to me was to grind the new chuck onto the spindle to improve its fit.  I was able to hold the spindle in the lathe  chuck whilst mounting the new drill chuck backwards in my tap holder- which was itself mounted in the tailstock. To do this I used a piece of straight round steel bar gripped in the chuck of my tapping unit. I could then grip this in turn with the jaws of the new chuck jaws so that its taper now faced forwards, towards the spindle held in the lathe chuck.

There was quite lot of grinding required so I used both coarse and fine valve lapping compound in turn- smearing the spindle taper with the appropriate compound and then advancing the tailstock so that the tapers engaged. I rotated the lathe firstly by hand and then at low speed whilst holding the tapping unit to prevent rotation. I ground in both directions by reversing the lathe. Clearly not the best solution in terms of accuracy but an awful lot better than free hand grinding. After grinding the fit was greatly improved but not perfect. I wont be able to check whether runout has been improved until I've reassembled the drill.

Spindle tapping

The second possibility, assuming that my grinding proves out of true or attachment is simply insecure, is to convert the drill to use a threaded chuck by drilling and tapping the end of the spindle. I can then use a short threaded stud as an adapter and screw the new chuck onto that. I decided to do this at the same time as grinding the taper since both required holding the spindle in the lathe. I didn't want to weaken the end of the spindle too much so chose to use a 3/8 threaded chuck rather than a half-inch. I found a 13mm chuck with an internal 3/8 thread (24tpi UNF) from Chronos tools and UNF studding was available from Ebay. This required an 8.5mm pilot hole to be drilled in the spindle which I did in the lathe to try and keep it true to centre.

Drilling the spindle end- note the taper has been ground at this stage but not yet polished.

To my surprise the spindle drilled quite easily as whatever hardening process had made the grinding difficult didn't seem to have affected the metal of the interior. I could then thread the inside of this bore using an HSS tap set, moving to the plug tap to get as close to the bottom of the bore as possible.

Finally as as a temporary measure I reassembled the drill using the reverse of the process below. Having attached the 6MT chuck I found rotation was now smooth with run-out vastly improved. Drill functionality restored- at least temporarily whilst I await delivery of the new parts.

Dismantling the drill

This is pretty much a reworking of my first post in this blog although I tended to use a more direct approach to pressing and removing the bearings. 

1st step as always was to remove the drive belts and Unscrew the nut holding the drive pulley block to the spindle which is a left hand thread . I then removed the 4 screws that hold the drive belt case at to the top of the drill removing the case as well as the pulley block.

 I have replaced the screws in the top of the drill for safekeeping.

 Next I removed the nuts holding the rise and fall sleeve spring mechanism to the left hand side of the drill.

 The spiral spring simply pulls off inside its case its not under much tension

 Having removed the Spring the rise and fall sleeve rack and pinion mechanism could be removed by simply pulling handle out to the right. 

 Next remove the depth stop guide by unscrewing the nut at the bottom and simply pulling the threaded shaft out

 Loosen the sleeve slide adjuster grub screw having 1st loosened the lock nut

 Remove the upper spindle sleeve clamp grub screw at the top of the drill on the left.

 The spindle and lower sleeve can then be removed by tapping downwards using a soft drift on the top of the spindle inside the upper spindle sleeve

 This removes the spindle inside the rise and fall sleeve.

 Here you can see that the E clip I placed on top of the upper bearing in the sleeve is still present

 Remove the E clip and then you can tap the spindle downwards out of the rise and fall sleeve. The lower bearing comes out attached to the spindle the upper  bearing remains inside the sleeve

To remove the lower bearing insert a screwdriver and twist to force the inner race away from the taper base of the spindle.

  The lower bearing will then slide most of the way along the spindle until it reaches the top bearing land.  Rest the bearing in the jaws of a vise and tap the rest of the spindle through to remove it completely.

Changing the spindle

New spindle from Sealey with 2MT chuck attachment.

To start reassembling locate the bearing and tap it down over the new spindle to the lower bearing mounting land. I used a hollow steel tube that slipped over the spindle and rested on the bearing inner race to do this

New sleeve with lower bearing fitted. The hollow tube used to install it is shown above.

The new spindle could then slip easily up inside the rise and fall sleeve and through the top bearing.  

The first difference is that although a "retaining ring" is shown above the top spindle bearing (where the E clip was fitted in the old drill), there is no groove in this new spindle to accept a circlip and so fix it in this position. I fitted a star washer at this point, tapping it down the shaft to contact the bearing.

Sadly this left an unacceptably large amount of wobble in the shaft. Inspection showed that the ground bearing land on the new shaft is lower than on the original. Unfortunately the recess in the feed sleeve isnt deep enough to allow the bearing to sit this low so it was actually resting above the ground land and was consequently too loose on the shaft. To overcome this I was forced to deepen (extend the bore) inside the feeder tube so that the bearing could sit lower.

Bearing location groove inside feeder sleeve. This needs to be extended by 10mm so that the bearing sits further inside the sleeve.

When the bearing is positioned here then the groove in the spindle can be used to fit a circlip.

 You can also buy a new feeder sleeve from Sealey but if you do, insist on a cast iron one as the more modern replacements are aluminium and a poor fit in the drill body.

Further, although the upper spindle sleeve bearings are the same in both drills, the mounting methods are different. The older drill GDM30 uses two bearings separated by a plastic spacer, the newer drill uses circlips to separate and locate  the bearings: circlips which presumably locate in grooves formed inside the drill body. Since my drill body is the original GDM30 version I don't have any such grooves, and in any event the clips needed are not available without a long lead time. I'm hoping to reuse the "twin bearing and spacer" system which fixes and positions the bearings using a grub screw to secure the intermediate plastic spacer. I therefore retrieved the plastic spacer from the old upper spindle sleeve.

Plastic spacer from the older drill which I hope to reuse with the new spindle sleeve (when it arrives!).

In fact the plastic sleeve turned out to be too thick for the new spindle so I machined a narrower soft aluminium spacer of similar dimensions and that worked well. It allows some adjustment of the depth to which the spindle sleeve is inserted so as to keep the pulley blocks level.

Thin aluminium spacer inserted between bearings on spindle sleeve

Spindle sleeve secured at aluminium washer level by grub-screw

Pulley block height adjusted (new pulley block illustrated)

Sealey pillar drill strip and replace bearings GDM30A

My workshop is sadly a place that good tools go to die! This one is no exception and I've had this drill for a few years now- I bought it second hand and its pretty old by now- obsolete very possibly having been replaced by the GDM50. That drill is more powerful but apart from that has only minor updating from my model 30.

Anyway its started making some horrible graunching noises and has a definite tight spot in rotation. I hope this isn't a bent drive spindle, but having eliminated belt tension I think the bearings are a likely culprit. The motor turns easily when disconnected and although the noise isn't as bad when the spindle is spun by hand I can detect some graunching noises using the tried and tested screwdriver-to-the-ear method. The motor bearings in contrast sound smooth.

This is the parts list for the drill. The spindle (58) passes through a sleeve (56) and into an upper spindle cover (65) which also holds the drive pulley. The upper spindle has 2 bearings (66) separated by a plastic spacer and the lower sleeve another two (61 and 59) fitted in the top and bottom. Upper sleeve bearings are type 6203ZZ and the lower sleeve (despite having different numbers in the chart) are both type 6201ZZ. Both types are readily available and  Sealey parts are in stock at CCW tools. However at £12-16 each this pretty much makes repair uneconomical when a 350w Silverline bench mounted drill is available new at only £70 or so. I shopped around and got Dunlop versions of both types for about £2 each. I'll try replacing these first although I do suspect I need new brushes as well.

Firstly Some general views before I start- I don't have a stripping manual (!) so I want a record of what was where before I start.

So first step is to remove the drive belt and unscrew the nut retaining the spindle drive pulley. This is a reverse thread 1/2 WW


Hold the drill chuck in a mole grip and it comes off fairly easily



The pulley stack is one piece and levers off carefully with a screwdriver.

Undo the 4 Phillips screws that hold the belt guard on and remove it. It handily lifts over the motor drive pulleys.

The upper bearing of the 4 is then revealed, as its top protrudes from the housing. To be frank-with hindsight I think this was probably my entire problem and simply tapping this back down might have sorted it. It wasn't until I reassembled that I realised that in fact there is room for this bearing to sit flush in the housing and this is presumably its correct location. However I didn't know that at the time and anyway changing the bearings should do no harm...?
Remove the grub screw using an Allen key

 Then refit the top nut and carefully tap it upwards using a soft punch, turning the shaft to equalize the pressure until it lifts clear.

 Withdrawing the spindle sleeve and its two bearings (note plastic spacer in between.

Remove the depth stop collar from above the chuck- one Phillips screw and then it just clips off.

The spindle itself is still held by the drilling handles so remove the double nuts that secure the handle shaft and return spring cage.

The return spring is coiled in the black housing beneath- it will unravel as you pull it off the handle shaft but it only seems to be under about half a turn of tension anyway.

The spring fits into a slot in the end of the handle but once off the handle can be withdrawn. Support the chuck as you pull the handle out because the shaft will drop free.

 It slides out easily revealing the gearing rise and fall mechanism on the handle.

At the same time the shaft cover also falls out (hence the need to support it above) and the ladder gear on the shaft is obvious

The upper bearing is visible at the top of the cover- note circlip retaining the bearings.

Remove the circlip and tap the spindle downwards through the sleeve. The lower bearing comes out with the shaft as you do so.

Shaft and sleeve- upper bearing remains in the top of the sleeve.

The upper bearing remains in the sleeve tube but is easily tapped out from beneath using a flat faced soft punch.

The chuck is a morse taper fit on the spindle and just taps off downwards. Lower bearing still on shaft.

 The lower bearing is tight on the shaft. Its tight up against the ridge above the chuck so it has to come off the long way round! I started it using a socket to tap it down and completed it using equal side blows - its a bit of a  fuss and I feel sure I can find a better way if I have to do it again. The bearing is tight all the way along and I'm a little worried about how to refit, but I think I  may have to freeze the spindles before fitting the bearings.
I couldn't use this method for the upper sleeve as I didn't want to transmit any force through the plastic spacer. Eventually I used  a large socket to support the lower bearing and pressed down on the shaft end using a socket  so that no force went through the plastic.

The upper bearing was then free and could be removed with the plastic spacer.

Note that this bearing pair has their inner covers removed. I'm not sure if this is necessary and I don't intend to do that- my new bearings are shielded and I'll leave both covers in place.

The shaft was then pressed out of the second bearing using an appropriate combination of sockets as above.

Reassembly was pretty straightforward. I didn't take any pictures but I will make the following comments.

I did chill both shafts down to -20 in a domestic freezer before fitting the bearings. The shaft bearings then went on much more easily and

no longer bound all the way down, once past the upper bearings location point the bearing simply dropped down the shaft and could be pressed into position using a metal tube sleeve.

I used the press in combination with the holes in the press-plate and sockets to support the bearings such that pressing onto a shaft- press on the inner race only, and pressing into a housing, press on the outer race.

When pressing bearing onto both spindle and sleeve it is important not to press then too far because they do tighten up, I had to back them off a couple of times to preserve free rotation.

I replaced the "C" clips using E clips because I happened to have these but they located more positively.

I reassembled the shaft and sleeve into the housing- that's when I found that the upper bearing can and does recess nicely flush into the top of the drill. However it is important that the drive belt runs horizontally between the two pulleys when the spindle sleeve pulley is pushed down firmly nto the taper. If you simply pusheverything down as far as it will go the belt will be tipped down at the front. As soon as you run the drill the drive bet then lifts the pulley block up the spindle taper unscrewing the retaining nut to allow it to rise. This I found was the cause of my problem with this drill- in use the sleeve and its bearings was being gradually pulled upwards- out of the housing and unscrewing the nut. This created noise and weakened the drive transmission to the sleeves. It took a few goes but through trial and error I did manage to position the bearings and sleeve such that the drive belt was hoorizontal and there was no "lift" tendency when the drill was operated. In this position the pulley block remained firmly on the spindle taper and rotated clear of both the drill housing and the upper belt cover mounting screws.This made rotation much quieter and smoother.

Anyway I completed reassembly and it was as they say, the reverse of dismantling. The shaft seems a bit tighter... Probably didn't get the bearings loose enough on the plastic spacer of the upper shaft but I think it will loosen up with use. Good news is that the horrible graunching has gone and everything runs smoothly and quietly... Job done I think!!!